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monty
2008-05-31, 12:09 AM
The "ingenious use of spells" thread got me wondering. What would happen if you cast Reverse Gravity on a black hole? Also, in order for it to have an effect, would you just have to cast it on the core or would you need a ridiculously high caster level to affect the entire volume to the event horizon?

BizzaroStormy
2008-05-31, 12:13 AM
It would become a white hole and start expellnig the trapped energy and matter it gained as a black hole.

FlyMolo
2008-05-31, 12:15 AM
The spell "reverses gravity" (in the spell text, even), so if you cast it on the core of a black hole, (Possible. Hard to get there, but you could.) the hole would turn itself inside out, throwing all its mass out of the area of the spell. Once outside the area, it would try and recollapse again. At the very least, the amount of mass moved around in the immediate area would play havoc with local spacetime. Gravity waves! BIG ONES!:smallbiggrin:

Edan
2008-05-31, 12:16 AM
With all the infinite (theorized) properties of a blackhole, I don't think a finite spell would affect it that much. Perhaps a fluctuation. Have it stop for a bit, like a hiccup. Personally, I would have it stop for 1 Round/Caster Level. Destroying reality and other dramatic effects I think are a bit on the Rule of Cool side of this.

monty
2008-05-31, 12:25 AM
With all the infinite (theorized) properties of a blackhole, I don't think a finite spell would affect it that much. Perhaps a fluctuation. Have it stop for a bit, like a hiccup. Personally, I would have it stop for 1 Round/Caster Level. Destroying reality and other dramatic effects I think are a bit on the Rule of Cool side of this.

It really only breaks, though, if it is infinite. I assume that Reverse Gravity basically just reverses the direction of the force vector for gravity within its area of effect. So if a black hole has a gravitational force with a magnitude of ∞ (within the event horizon) directed toward its center, then reversing it would give it a magnitude of ∞ directed away from the center. This would instantly accelerate all of the matter within the effect to c (that is, the speed of light), moving outward from the black hole, which would break all of the laws of relativity and do bad things to the universe.



By the way, how many catgirls do you think we've killed so far?

FlyMolo
2008-05-31, 12:30 AM
With all the infinite (theorized) properties of a blackhole, I don't think a finite spell would affect it that much. Perhaps a fluctuation. Have it stop for a bit, like a hiccup. Personally, I would have it stop for 1 Round/Caster Level. Destroying reality and other dramatic effects I think are a bit on the Rule of Cool side of this.
It's a spell that multiplies by -1. Not really finite. And if you shut off a black hole, all the bits would come sproinging out really fast. They're wedged in there pretty tight.

I don't think it would destroy reality, but the bits nearby wouldn't be in very good shape. For a start, they would have large fractions of a solar mass shoved through them quite fast.

If a black hole has infinite curvature of space, a reversed black hole is like a wall. Nothing can get in, because it requires an infinite amount of energy to get past. There's just a mirrored ball, which everything bounces off of.

If you're falling in, a reverse gravity spell targeted on you is the best idea. You'll go zooming off into freedom. At least in theory. Yeah, because the curve is so steep. The gravity is so much stronger at the end where you're at that it shoves you up through the top of your head and out to the end of the field, flinging you a long way. Hopefully. Recast if necessary. Casting it on the black hole is a bad idea, because nobody wants to be vaporized.

monty
2008-05-31, 12:39 AM
If you're falling in, a reverse gravity spell targeted on you is the best idea. You'll go zooming off into freedom. At least in theory. Yeah, because the curve is so steep. The gravity is so much stronger at the end where you're at that it shoves you up through the top of your head and out to the end of the field, flinging you a long way. Hopefully. Recast if necessary. Casting it on the black hole is a bad idea, because nobody wants to be vaporized.

Of course, if you're falling in, you're dead anyway. The combination of the massive amounts of radiation and the gravity on your body (the distance between your head and feet is enough that the black hole will start tearing you apart) will probably kill you before you can get a spell off. I was assuming you had some means of casting it that didn't involve you personally being there.

FlyMolo
2008-05-31, 12:44 AM
Of course, if you're falling in, you're dead anyway. The combination of the massive amounts of radiation and the gravity on your body (the distance between your head and feet is enough that the black hole will start tearing you apart) will probably kill you before you can get a spell off. I was assuming you had some means of casting it that didn't involve you personally being there.

Contingent Spell and Animate Object. That's clever, no? Throw the pet rock at the hole, then watch the fireworks from a safe vantage points. FAR AWAY.

Lycan 01
2008-05-31, 12:51 AM
Mmmm, spagghettification... :smallamused:


I like the whole "universe rips in two" outcome. I mean, black holes are the universes' vaccuum cleaners. They suck up stuff, and that stuff doesn't come back out. If you somehow manage to reverse it (the vaccuum cleaner), then you have random stuff flying out everwhere and a really big mess. Now, lets say a black hole reverses. Well, the laws of physics and space and time and other complex law things just basically got told to drop their pants, and now you have ungodly amounts of mass coming out of nowhere, with nowhere to go. End result? REALLY BAD THINGS!!!


So yeah, I'd just go with "everything dies" to save a lot of time. :smalltongue:

Edan
2008-05-31, 12:56 AM
One idea. General relativity states that a black hole singularity has 0 volume, but the spell targets a defined cubic area, can it even be affected.

Another question, in the exact words of the spell:

This spell reverses gravity in an area, causing all unattached objects and creatures within that area to fall upward and reach the top of the area in 1 round. If some solid object (such as a ceiling) is encountered in this fall, falling objects and creatures strike it in the same manner as they would during a normal downward fall. If an object or creature reaches the top of the area without striking anything, it remains there, oscillating slightly, until the spell ends. At the end of the spell duration, affected objects and creatures fall downward.

Provided it has something to hold onto, a creature caught in the area can attempt a Reflex save to secure itself when the spell strikes. Creatures who can fly or levitate can keep themselves from falling.
(Emphasis mine)

What would that imply, even if gravity was reversed you would not travel beyond the area of the spell, at least until it ended.

Anyone a physicist and rules lawyer?

PS: We need to kill more catgirls.

monty
2008-05-31, 12:58 AM
So yeah, I'd just go with "everything dies" to save a lot of time. :smalltongue:

That really doesn't describe it that well. I'd rather go with something like "rapidly expanding sphere of absolute destruction of everything everywhere" or something like that. I mean, can you really even conceive of what an arbitrary quantity of matter moving at the speed of light can do?

Lycan 01
2008-05-31, 01:02 AM
Really bad things?


I'm guessing every little particle of matter will be moving at really, really fast speeds, which would allow them to simply rip through everything in their path.

Examples...

Tornados hurl pine straw with enough force to impale it in walls. So lets say the exploding black hole is a really, really, really big tornado. Now add in a bazillion, jillion bits of pine straw. The pine straw then proceeds to impale through everything everywhere at once.

Or, for the hunting types, every piece of birdshot in existance x infinity shoots through every square inch of reality at once.



Destroying the universe is fun.....


So what's this "killing catgirls" joke I keep hearing?

monty
2008-05-31, 01:05 AM
One idea. General relativity states that a black hole singularity has 0 volume, but the spell targets a defined cubic area, can it even be affected.

I'd assume that if the singularity is within the area of the spell, it would be affected.


Another question, in the exact words of the spell:

(Emphasis mine)

What would that imply, even if gravity was reversed you would not travel beyond the area of the spell, at least until it ended.

Well, in normal gravity, when you reached the top of the spell area, normal gravity would take over and start to pull you down; hence the oscillation. However, the force of a black hole is only (possibly) infinite within the event horizon; outside of that, it only has regular gravity based on its mass, which is insignificant compared to the force within. So if the singularity was within Reverse Gravity, would the event horizon be reversed (since it is caused by the singularity), normal outside the spell effect (which would cause a rather interesting oscillation effect) or something completely different?


We need to kill more catgirls.

Agreed.

Edan
2008-05-31, 01:11 AM
So what's this "killing catgirls" joke I keep hearing?

It is a running meme on the forums that basically goes like this.
"Whenever someone brings up real world physics in a discussion of magic (particularly magic in an FRPG) or science fantasy "technology," a catgirl is killed. The statement "please, think of the catgirls!" is meant to deter such discussions from starting in the first place."

Or we could just make this easier and say this is where spheres of annihilation come from. How they get into statue's mouths, we don't really know.

Xefas
2008-05-31, 01:29 AM
Would the multiplanar nature of the D&Dverse effect this at all? Other than that if you managed to escape the Prime and into some alternate plane, the Inevitables would be coming in the millions to teach you a lesson.

"This one just destroyed all the laws of physics at once. Do we have a model of Inevitable for that?"
"Lets just have it be ironic and make a giant sentient Spiked Chain to kick the crap out of him."

quiet1mi
2008-05-31, 01:51 AM
i smell an Epic level plot hook... Or it could be the rotting flesh of the poor cat girls...

Patashu
2008-05-31, 02:14 AM
Good thing black holes don't exist in the D&D cosmology, eh? ;)

bosssmiley
2008-05-31, 03:17 AM
Good thing black holes don't exist in the D&D cosmology, eh? ;)

Errr, they do. As magic items (http://www.d20srd.org/srd/magicItems/artifacts.htm#sphereofAnnihilation), as monsters (http://www.d20srd.org/srd/epic/monsters/umbralBlot.htm) and as BBEGs (http://www.wizards.com/default.asp?x=dnd/drfe/20080318a). Sentient vengeful black holes. :smallcool:

A non-catgirl endangering explanation: reversing the gravity of a black hole cause massive structural strain on the surrounding plane and results in the awakening of the Herald of Galactus Thurizdan. Congratulations bub, your Epic version of reverse gravity just started the Apocalypse. :smallamused:

Tsotha-lanti
2008-05-31, 06:14 AM
What would happen if you cast Reverse Gravity on a black hole?

Things in the area of the spell would "fall" away from the black hole.

Until they got outside of the spell's effect, when they'd presumably fall back toward the black hole, and enter the spell's area again, and so on until the spell wore out, since the spell only affects gravity in a small area, rather than changing any intrinsic property of anything in the area.

Good luck getting close enough to cast it, though...

Xsjado
2008-05-31, 07:22 AM
This would instantly accelerate all of the matter within the effect to c (that is, the speed of light), moving outward from the black hole, which would break all of the laws of relativity and do bad things to the universe.

I'd point out that this breaks no laws of relativity. Objects that started very close to the reversed black hole would indeed be accelerated to near c but nothing says that they would exceed it. Indeed it just turns gravity into a force more similar to the electric force (where it can act as either attractive or repulsive).

Equally nothing says that the black hole would start spewing out matter. The spell just reverses the vector force of gravity, so while it would create an odd effect it wouldn't "break" anything. Current cosmological theory even includes a force which produces exactly this effect: "dark energy."

EDIT: Black holes don't contain infinite mass anyway, they are points of infinite density. This creates very strong gravitational effects, but if they were truly infinite mass then everything would be instantly attracted to them at the speed of light. Gravity is a function of the masses of two objects. If one of those is infinite then the attractive force is infinite.

Chronos
2008-05-31, 11:11 AM
Anyone a physicist and rules lawyer?Not only am I a physicist, I specialize in general relativity, the field directly concerned with black holes and the like. And Reverse Gravity is one of my favorite spells. And I'm afraid to contemplate this combination. If you can content yourself with something tame like blasting away everything in the vicinity at nigh-limitless speed, then I'll leave you to your bliss. Naked singularities are ugly.


"This one just destroyed all the laws of physics at once. Do we have a model of Inevitable for that?"Actually, they do. There's an epic Inevitable somewhere reserved for folks who tamper with the fabric of space and time. They're called Quaruts, I think.

FMArthur
2008-05-31, 02:40 PM
In what ways would this be different from a small-scale "Big Bang" event?

ikrase
2008-05-31, 03:23 PM
If you reverse a black hole, it forms a reverse event horizon the same diameter as the original (and a small black hole can have a small event horizon, one inch is theorecially posible). A gravitational shockwave rolls out. This does no damage, but disrupts any planar portal, and destroys Portable Holes, Bag of Holding, ect within several million mile radius, no planar stuff can happen for years.
The material in the hole is ejected as radiation and hydrogen gas and 99.99999% speed of light. WHen the singularity is reduced to zero mass, it disappears. No naked singularity, i am pretty sure. You could kill every planar spell and destroy a solar system.

SolkaTruesilver
2008-05-31, 03:47 PM
Hum, if you'd cast Reverse Gravity on a part of a black hole (as some person may suggest would happen), that would create a Pulsar, where the matter is ejected from one side, and re-absorbed be the equator.

The thing is, about the 0-volume thing and spaghettisation, it only appears from the outside perspective of the black hole. If you are going yourself in it, your are staying pretty much the same. The thing is, your time frame is slowing, and you will never really reach the point of time where you reach the black hole itself.

Hurray for relativity!

Lycan 01
2008-05-31, 03:51 PM
Can you hear it? Can you hear the screaming? The screaming of all the catgirls you just killed?


Seriously, this topic makes my brain hurt. If I were a DM, and I had to deal with this, I'd save myself and my group a lot of time and brain pain by just saying reality shredded itself slowly and painfully. :smalltongue:

monty
2008-05-31, 03:55 PM
The thing is, about the 0-volume thing and spaghettisation, it only appears from the outside perspective of the black hole. If you are going yourself in it, your are staying pretty much the same. The thing is, your time frame is slowing, and you will never really reach the point of time where you reach the black hole itself.

You are actually stretched, though, and it doesn't have anything to do with relativity. Since gravitational force is a function of distance, and the top of your body is a different distance from the center as the bottom, the different parts of your body are being pulled with different levels of force. Normally, the difference is insignificant, but with the magnitude of force in a black hole, it will start to stretch you.

Cuddly
2008-05-31, 04:04 PM
Can you hear it? Can you hear the screaming? The screaming of all the catgirls you just killed?

Like a million voices cried out and were suddenly silenced....

Wabbajack
2008-05-31, 04:28 PM
Wait, isnt a black hole basically only as large as a sphere with a diameter of one planck length, wich means you cant target only one part of it?

Chronos
2008-05-31, 04:41 PM
In what ways would this be different from a small-scale "Big Bang" event?The Big Bang singularity is behind a horizon of sorts. It's a different sort of horizon, being based on an infinite redshift, but it still gets the job done.


The thing is, about the 0-volume thing and spaghettisation, it only appears from the outside perspective of the black hole. If you are going yourself in it, your are staying pretty much the same. The thing is, your time frame is slowing, and you will never really reach the point of time where you reach the black hole itself.Spaghettification isn't something inherent to black holes; it's just a matter of tidal forces. In the same way that the Moon is stretched into an oblong shape by the Earth, or the Earth and its oceans are stretched into an oblong shape by the Moon and the Sun, things near a black hole will also be stretched. Whether this results in anything lethal or otherwise interesting depends on the mass of the hole, the distance of the object from the hole, and the durability of the object. For a sufficiently large black hole, a human could pass through the event horizon and be completely unharmed.

As for the time thing, you've got it backwards. From the reference frame of someone safely outside the hole, the falling person will never quite reach the horizon. However, from the reference frame of the person falling in, you'll reach the horizon, pass through it, and inevitably hit the singularity, in very short order (a few nanoseconds, for a stellar-sized black hole; perhaps as long as a couple of minutes, for the largest supermassive black holes).

EDIT:

Wait, isnt a black hole basically only as large as a sphere with a diameter of one planck length, wich means you cant target only one part of it?When one refers to the size of a black hole, one means the size of the region within the event horizon. The event horizon has a radius proportional to the mass of the hole, and works out to be a few kilometers for one of stellar mass. The singularity in the center of a black hole appears, in current models, to be of zero size, but really, it could be anything, so long as it's spherically symmetric and entirely inside the horizon, and the theories all work just as well. It is widely suspected that once we have a working theory of quantum gravity, the singularity will turn out to have a very small but finite size (perhaps the Planck scale), but we don't yet have a working theory of quantum gravity, so that's just pure speculation.

Flickerdart
2008-05-31, 04:53 PM
I wonder.

If casting Reverse Gravity on a black hole rapes the universe, could a Genesis spell cast at the right time take advantage of that somehow?

The Corinthian
2008-05-31, 04:56 PM
Not to be a party-pooper, but Reverse Gravity does not actually reverse gravity in the area it affects. Its' more like Sustained Force mode Telekinesis. I'm no physicist, but if this were not the case I imagine it would cause matter to behave rather more strangely (and fatally) than just "falling upward".

Chronos
2008-05-31, 05:07 PM
Actually, if Reverse Gravity worked through any mechanism other than gravity, it would cause strange and possibly fatal effects. Telekinesis, for instance, acts directly only on the outer surface of an object, so if Reverse Gravity worked like Telekinesis, your skin would be pushed upwards, while your innards are still pulled downward by real gravity, making you feel like you were lying on a floor in two gees, rather than the zero gees you'd experience from freefall (even freefall upwards).

Besides which, the spell is pretty clear on what it does:
This spell reverses gravity in an area

The Corinthian
2008-05-31, 06:06 PM
The designers who wrote that were, as the saying goes, thinking of the catgirls, more concerned with conveying the point of the spell's effect than its impact on physics. If gravity were really reversed, all matter within the spell's area would repel, rather than attract, all other matter (and interaction between things inside and things outside the field would be seriously weird) and, although as I noted I am not a physicist, I imagine that at least some types of accretions of matter would fly apart or outright disintegrate, that is those not bound together by other forces stronger than gravity. Even objects held together by such forces are structured to function in normal gravititional fields, and could be seriously screwed up if that force was momentarily reversed.

Or am I just completely off the deep end? Physicists, please help!

EDIT: Just realized Chronos IS a physicist, so I look pretty dumb gainsaying him. Still, Chronos, could you explain to me what I'm getting wrong?

monty
2008-05-31, 06:27 PM
The designers who wrote that were, as the saying goes, thinking of the catgirls, more concerned with conveying the point of the spell's effect than its impact on physics. If gravity were really reversed, all matter within the spell's area would repel, rather than attract, all other matter (and interaction between things inside and things outside the field would be seriously weird) and, although as I noted I am not a physicist, I imagine that at least some types of accretions of matter would fly apart or outright disintegrate, that is those not bound together by other forces stronger than gravity. Even objects held together by such forces are structured to function in normal gravititional fields, and could be seriously screwed up if that force was momentarily reversed.

Or am I just completely off the deep end? Physicists, please help!

EDIT: Just realized Chronos IS a physicist, so I look pretty dumb gainsaying him. Still, Chronos, could you explain to me what I'm getting wrong?

I'm not Chronos, nor am I a physicist (not yet, anyway), but I can probably help to some extent. The repulsion by stuff within the effect would be, for the most part, negligible. On a normal scale, gravitational attraction (or in this case, repulsion) can only be measured by sensitive instruments and has no meaningful effect in daily life. On a microscopic level, it is equally irrelevant; the electromagnetic and strong force effects between atoms and subatomic particles are many orders of magnitude stronger than the gravitational effects between them.

Collin152
2008-05-31, 06:43 PM
Bwahaha!
I knew it!
A passing comment from me can spawn a whole new thread!
I still say reality gets cut to pieces by pieces of metaphysical shrapnel impaling every last bit of matter on a subatomic level.

Bitzeralisis
2008-05-31, 06:55 PM
The spell doesn't make an object exert negative gravity. The spell basically multiplies the "dimensional warping" caused by gravity by -1 in that area, so that instead of falling in, things are expelled out. At the very border of the reversed gravity is a tiny zone of stability, and this is where, by the laws of inertia and friction, matter will gradually oscillate at a gradually slower and smaller rate.

Casting Reverse Gravity on the center of a black hole would do absolutely nothing at all (at least outside) — the matter at the center of the black hole would get expelled out, only to meet the inwards-pulling gravity of the area outside the area of the spell. Thus, it would ram into the "wall" of the spell and stay there, quite unable to get more compressed and most likely staying the same size as it was before the spell was cast.

If the spell was large enough to cover the whole black hole, it would start to "blow up" (and thus remove the gravity to be reversed from the area of the spell), until the explosion formed a mass sphere sufficiently large enough to basically reverse the gravity in the area by pulling outwards in every direction evenly. This "reversed" gravity would then be reversed again by the spell, which would pull all the mass back in (hopefully, there might be some residue that escapes) and restart the cycle. Ending the spell could be fatal.

Xuincherguixe
2008-05-31, 07:54 PM
Whatever it does, it definitely seems like something fun.

Recaiden
2008-05-31, 11:27 PM
I think that if the spell was large enough, by the time the matter was at the edge, gravity would be weak enough to prevent the black hole reforming

Waspinator
2008-06-01, 12:34 AM
I think it's safe to say that no matter what happens, you're probably going to tick off some D&D entities that you really wouldn't want to.

Cursedblessing
2008-06-01, 07:50 AM
uhhhh, no.
Reverse gravity would not destroy the black hole at all because at that point the black hole is held by density and if it were there would be no return to blackhole because of a) force of expusion and b) the cause of gravity was rid of. but bcause the densit self sustains there would be an object that nothing can come near (think file of repusion):smalltongue:

MorkaisChosen
2008-06-01, 08:36 AM
The infinite gravity thing is misleading. From my 16-year-old nerd perspective, it looks as if there's only infinite gravity right on the singularity. I think it'd just turn into a white hole, spew everything out at a large fraction (but still only a fraction) of c, and, if the area was big enough to encompass the whole thing right to the event horizon, it wouldn't reform since all the matter would go flying out and momentum would carry it away (since there probably wouldn't be another large lump of matter to cause more gravity).

The question is, what form would the matter spewing out take...?

Another thing that just struck me: you can use True Creation to make any type of matter. "The volume of the item created cannot exceed 1 cubic foot per caster level."

Using only a level 15 wizard, I can destroy all civilisation on the planet.

How?

Antimatter bombs.

SolkaTruesilver
2008-06-01, 08:48 AM
The infinite gravity thing is misleading. From my 16-year-old nerd perspective, it looks as if there's only infinite gravity right on the singularity. I think it'd just turn into a white hole, spew everything out at a large fraction (but still only a fraction) of c, and, if the area was big enough to encompass the whole thing right to the event horizon, it wouldn't reform since all the matter would go flying out and momentum would carry it away (since there probably wouldn't be another large lump of matter to cause more gravity).

The question is, what form would the matter spewing out take...?

Another thing that just struck me: you can use True Creation to make any type of matter. "The volume of the item created cannot exceed 1 cubic foot per caster level."

Using only a level 15 wizard, I can destroy all civilisation on the planet.

How?

Antimatter bombs.

I am sure you will kill mot Catgirls with your antimatter than you'll kill dragons

MorkaisChosen
2008-06-01, 09:09 AM
Depends on the density of antimatter (and of catgirls). Thing is, this is a direct application of E=mc^2. Energy released from the antimatter lump is equal to the square of the speed of light multiplied by twice the mass of antimatter (since it annihilates an equal mass of matter).

This reminds me of a haiku from KoL:

Hippopotamous
Antihippopotamous
Annihilation.

Justyn
2008-06-01, 09:17 AM
I would assume that the effect would depend on the area of the spell's effect: smallenough, and after the spell ends, gravity resets, and the black hole reforms; big enough, and the gravity is not enough to reform the black hole.

Of course, the "large enough area" in question might just give VY Canis Majoris a run for its money in the size catagory.


Also, a black hole exploding would not have the energy to destroy the universe. If enough energy to destroy the universe was gathered in one location, the universe would be be destroyed because of the lack of energy anywhere else.

InaVegt
2008-06-01, 09:20 AM
Of course, the "large enough area" in question might just give VY Canis Majoris a run for its money in the size catagory.

Not really, it wouldn't even come anywhere near the size of the moon, let alone of the biggest star we've found.

Black holes are known to be only kilometres in diametre.

Yvian
2008-06-01, 09:39 AM
O.K., the spell says:

If an object or creature reaches the top of the area without striking anything, it remains there, oscillating slightly, until the spell ends. At the end of the spell duration, affected objects and creatures fall downward.

So, if you cast the spell inside the event horizon, gravity reverses direction, right? So we now have a hole in space [empty] with a lot of matter on the outside, a shell.

So I think one of 2 things could happen.

The first is that the shell of matter would still be in the event horizon. Instead of having a point, you have a balloon. Nothing has been changed per say, just that the event horizon has been pushed out by the radius of the spell.

The 2nd is that now the matter resides on the outside of the event horizon. Still very massive so it is going to try to pull itself together. So you are going to have a very massive shell. Maybe white dwarf material?

Which, I think, takes me to my 2nd point.

Not all black holes are created by massive mass crushing all things. In theory one can also have smaller black holes that were created by high pressure. These Black Holes may tend to "evaporate" thanks to Hawking radiation, but that is a different topic.

So, start with a small black hole. Cast reverse gravity on that, causing the event horizon to expand. Then cast a 2nd reverse gravity on that so it does not fall to the center of the earth. It kind of sounds like this would be one way of manufacturing a Sphere of Annihilation.

And you don't have to kill any catgirls.

Uncle Festy
2008-06-01, 09:55 AM
By the way, how many catgirls do you think we've killed so far?

Doesn't matter. You killed them all when you broke the universe.

Chronos
2008-06-01, 10:21 AM
Quoth MorkaisChosen:
The infinite gravity thing is misleading. From my 16-year-old nerd perspective, it looks as if there's only infinite gravity right on the singularity.Depends on what you mean when you say "infinite gravity". The event horizon is the location at which you would have to exert an infinite force to prevent yourself from falling in, so in that sense, you could say that everything inside the event horizon has infinite gravity. If you're talking about the gravitational potential, or the curvature of spacetime, though, the gravity only goes infinite at the singularity. If you're using the Ricci tensor to measure curvature, in fact, it's zero everywhere except at the singularity (of course, there are other components of curvature which aren't included in the Ricci tensor).


The question is, what form would the matter spewing out take...?Any form at all. A black hole can eat anything at all, and it has no memory of what it's eaten (a black hole that's eaten ten tons of hydrogen gas is indistinguishable from a black hole that's eaten ten tons of pink elephants made from antimatter), so if one got a black hole to spew out matter, it could spew out anything at all. Which leads to the next point...

Quoth Justyn:
Also, a black hole exploding would not have the energy to destroy the universe. If enough energy to destroy the universe was gathered in one location, the universe would be be destroyed because of the lack of energy anywhere else.It's not a question of the energy. It's a question of the laws of reality not being capable of comprehending the existence of an "opened" black hole. In layman's terms, the rest of the universe sees the naked singularity, panics, and goes insane.

Dervag
2008-06-01, 11:19 AM
Mmmm, spagghettification... :smallamused:


I like the whole "universe rips in two" outcome. I mean, black holes are the universes' vaccuum cleaners. They suck up stuff, and that stuff doesn't come back out. If you somehow manage to reverse it (the vaccuum cleaner), then you have random stuff flying out everwhere and a really big mess. Now, lets say a black hole reverses. Well, the laws of physics and space and time and other complex law things just basically got told to drop their pants, and now you have ungodly amounts of mass coming out of nowhere, with nowhere to go. End result? REALLY BAD THINGS!!!

So yeah, I'd just go with "everything dies" to save a lot of time. :smalltongue:I'd go with "total conversion of the hole's mass into energy and subatomic particles headed outwards"

Which means everything within a range from several miles to several lightyears dies, depending on how big the hole was. A small one will explode like a nuclear bomb. A big one will explode like a colossal supernova.


That really doesn't describe it that well. I'd rather go with something like "rapidly expanding sphere of absolute destruction of everything everywhere" or something like that. I mean, can you really even conceive of what an arbitrary quantity of matter moving at the speed of light can do?Yes.

Remember, the hole doesn't have infinite mass. It has finite mass.


Bwahaha!
I knew it!
A passing comment from me can spawn a whole new thread!
I still say reality gets cut to pieces by pieces of metaphysical shrapnel impaling every last bit of matter on a subatomic level.I think you're right, but only out to a certain radius. The black hole as finite mass. In the worst case (a stellar mass black hole), you get something like a supernova, only a little bigger. As far as I can tell, this spell should turn your black hole into a total conversion bomb of equal mass.


The spell doesn't make an object exert negative gravity. The spell basically multiplies the "dimensional warping" caused by gravity by -1 in that area, so that instead of falling in, things are expelled out. At the very border of the reversed gravity is a tiny zone of stability, and this is where, by the laws of inertia and friction, matter will gradually oscillate at a gradually slower and smaller rate.

Casting Reverse Gravity on the center of a black hole would do absolutely nothing at all (at least outside) — the matter at the center of the black hole would get expelled out, only to meet the inwards-pulling gravity of the area outside the area of the spell. Thus, it would ram into the "wall" of the spell and stay there, quite unable to get more compressed and most likely staying the same size as it was before the spell was cast.Not quite. Because the gravity inside the reversed zone is stronger than the gravity outside it (inverse square law, anyone?) Objects that can make it out of the zone of effect will have enough kinetic energy that they won't be pulled back, especially since there isn't any mass left in the hole.


If the spell was large enough to cover the whole black hole, it would start to "blow up" (and thus remove the gravity to be reversed from the area of the spell), until the explosion formed a mass sphere sufficiently large enough to basically reverse the gravity in the area by pulling outwards in every direction evenly. This "reversed" gravity would then be reversed again by the spell, which would pull all the mass back in (hopefully, there might be some residue that escapes) and restart the cycle.Hmm... it might... don't think so. Probably not.

The most likely form for stuff emitted by a black hole is going to be an enormous burst of EM (light). Particle-antiparticle pairs maybe, but my bet's on EM radiation. Given the energy release, almost all that stuff will be travelling outward at relativistic speeds. The stuff will fly away so fast that gravity won't be able to pull it back together, I think.


uhhhh, no.
Reverse gravity would not destroy the black hole at all because at that point the black hole is held by density and if it were there would be no return to blackhole because of a) force of expusion and b) the cause of gravity was rid of. but bcause the densit self sustains there would be an object that nothing can come near (think file of repusion):smalltongue:Force of density does not exist. Assigned reading: "Frozen Star" by George Greenstein.


The infinite gravity thing is misleading. From my 16-year-old nerd perspective, it looks as if there's only infinite gravity right on the singularity. I think it'd just turn into a white hole, spew everything out at a large fraction (but still only a fraction) of c, and, if the area was big enough to encompass the whole thing right to the event horizon, it wouldn't reform since all the matter would go flying out and momentum would carry it away (since there probably wouldn't be another large lump of matter to cause more gravity).Seconded, and I'm an older and somewhat more experienced nerd. Not by THAT big a margin, mind, but enough to be fairly confident. I welcome correction by any phyisicists who have completed their apprenticeship, though, as I have not.


Another thing that just struck me: you can use True Creation to make any type of matter. "The volume of the item created cannot exceed 1 cubic foot per caster level."

Using only a level 15 wizard, I can destroy all civilisation on the planet.

How?

Antimatter bombs.Swordguy came up with this one too. The reference is in his sig, but the phrase someone else came up with to describe this is delightful:

I'd complain about killing catgirls, but they're dead already. You killed them with your 685 quadrillion damage. (http://www.giantitp.com/forums/showthread.php?p=2010735#post2010735)

Of course, antimatter really only has to exist in a universe where relativistic quantum mechanics applies, and we're pretty confident the D&D universe is nonrelativistic because we know it allows teleportation.
_______________________________


So I think one of 2 things could happen.

The first is that the shell of matter would still be in the event horizon. Instead of having a point, you have a balloon. Nothing has been changed per say, just that the event horizon has been pushed out by the radius of the spell.Chronos would know details, but I think you've just created the ultimate in ring singularities. I'm not sure the event horizon changes, though.


The 2nd is that now the matter resides on the outside of the event horizon. Still very massive so it is going to try to pull itself together. So you are going to have a very massive shell. Maybe white dwarf material?The energy it gained falling up out of the hole is great enough that it won't crush back together. Gravity outside the shell can slow it down, but not stop it, because it's going to be travelling at as close to c as makes no difference.
_____________________________


Quoth Justyn:It's not a question of the energy. It's a question of the laws of reality not being capable of comprehending the existence of an "opened" black hole. In layman's terms, the rest of the universe sees the naked singularity, panics, and goes insane.Doesn't the reversion itself "explode" the singularity, though?

monty
2008-06-01, 11:41 AM
Doesn't matter. You killed them all when you broke the universe.

I'm going to steal that, ok?

Chronos
2008-06-01, 01:46 PM
The most likely form for stuff emitted by a black hole is going to be an enormous burst of EM (light).Well, assuming we can use Hawking radiation as a model, you'll start off with all sorts of crazy things, but once the dust settles and the unstable particles have decayed, you'll probably have mostly neutrinos (about 80%), followed by light, followed by a not insignificant amount (a few percent) of gravitational waves. Neutrinos end up dominating over light mostly by virtue of the fact that there are more kinds of neutrinos than photons, and everything else will either decay away, or annihilate with its antiparticles.


Doesn't the reversion itself "explode" the singularity, though?The answer to that question is the same as the answer to any other question involving singularities: Nobody knows.

And you can do pretty much whatever you want with a black hole, so long as whatever it is is contained entirely within the horizon. Nothing inside the horizon makes any difference to anything outside the horizon. I'm just worried about what happens when a portion of the horizon is in the area of the Reverse Gravity.

Nikolai_II
2008-06-01, 02:54 PM
Mmmm, spagghettification... :smallamused:


I like the whole "universe rips in two" outcome. I mean, black holes are the universes' vaccuum cleaners. They suck up stuff, and that stuff doesn't come back out. If you somehow manage to reverse it (the vaccuum cleaner), then you have random stuff flying out everwhere and a really big mess. Now, lets say a black hole reverses. Well, the laws of physics and space and time and other complex law things just basically got told to drop their pants, and now you have ungodly amounts of mass coming out of nowhere, with nowhere to go. End result? REALLY BAD THINGS!!!


So yeah, I'd just go with "everything dies" to save a lot of time. :smalltongue:


Nothing bad with that. All the mass was there already, magic makes it come out again. And not at the speed of light, since things inside the black hole are at ease. They would try to accelerate towards the speed of light, but since the spell effect would end before that, no problems. Make it persistent though.. :smalleek:

Uncle Festy
2008-06-01, 04:28 PM
I'm going to steal that, ok?

Awesome! I got sigged!
… you can take that as an OK.

Flickerdart
2008-06-01, 04:50 PM
Guys, guys, guys.

Is there any way to cast Reverse Gravity on the entire universe at once? That could be fun.

Bitzeralisis
2008-06-01, 04:59 PM
Not quite. Because the gravity inside the reversed zone is stronger than the gravity outside it (inverse square law, anyone?) Objects that can make it out of the zone of effect will have enough kinetic energy that they won't be pulled back, especially since there isn't any mass left in the hole.

Hey, I'm not a physics professor. I'm just glad I actually figured something (even if it was wrong) out. :smalltongue:

Chronos
2008-06-01, 05:55 PM
Guys, guys, guys.

Is there any way to cast Reverse Gravity on the entire universe at once? That could be fun.Oddly enough, that wouldn't be nearly as catastrophic. I think the net effect there would be to effectively reverse the direction of time.

Collin152
2008-06-01, 06:40 PM
Oddly enough, that wouldn't be nearly as catastrophic. I think the net effect there would be to effectively reverse the direction of time.

Which undoes the reverse gravity, so time goes back to normal.
So the reverse Gravity takes place.
So time reverses.
Therefore, time stops.

Chronos
2008-06-01, 07:09 PM
Yeah, I didn't think that cunning plan through all the way. There's no problem at all with time being reversed, but there is a problem with time becoming reversed. So that one would be bad, too, but at least it's comprehendably bad.

Collin152
2008-06-01, 07:11 PM
Yeah, I didn't think that cunning plan through all the way. There's no problem at all with time being reversed, but there is a problem with time becoming reversed. So that one would be bad, too, but at least it's comprehendably bad.

True. All it's doing is rendering something formerly infinite... finite.
I'm sure that's good for the cosmos.

Flickerdart
2008-06-01, 07:31 PM
Hmm...couldn't they then use a Quickened version of any spell that lets you move forward in time (there are a bunch of those, I think) to move in the NORMAL direction of time, which is now backwards, and in effect travel back in time?

Or, if it still moves forward forward, the caster would escape the time standstill while everything else would be caught inside...how would that work? Would it create two realities, or just give the caster free reign over the timeless 'verse?

MorkaisChosen
2008-06-02, 04:56 AM
PERSISTENT TIME STOP!

...

That or we get a Trousers of Time effect and there are now two universes- one fixed, and one (the one the wizard went into) where the spell never happened (because time going backwards stopped it) and it works normally.

Note: this is more like a science fiction writer's view (not that I am one) than actual coherent physics. Give me a few years to get some degrees and I'll get back to you.

The New Bruceski
2008-06-02, 05:48 AM
I'm not sure that reversing gravity would reverse time. From a very macroscopic perspective it would encourage progress towards a less clumpy universe, which is how things were after the Big Bang, but I don't believe it would be on a similar time scale, or result in a reversed Bang.

For point of fact, look at local effects; people and other objects would fly off the planet (stronger forces hold us together, but not onto the earth), not only from the gravity but from the lack of counter-force to the planet's spin. For the latter force, take a pail full of water and swing it in a circle by the handle. Now turn it around and do the same thing holding the base. That's anything that isn't tied onto the planet when gravity flips. Similarly the earth would leave its orbit from the sun and proceed on a straight line in its current vector, quickly prodded by celestial forces towards the most vacant part of the universe.

I'm not sure what would happen to planets or suns themselves, I'm not quite clear what's gravity and what's other forces. There would be a lot of disrupted equilibrium states (for example, solar pressure vs. gravity is what keeps the sun at a steady radius. Flip the gravity and it's all the same direction.) and I would not be surprised to see everything break apart rather quickly.

EDIT: To clarify the last paragraph things would definitely break apart. I am unsure how clumpy the resulting mess would be, and what form those clumps would take.

llamamushroom
2008-06-02, 06:16 AM
Quick question:
Hypothetically, what happens when you use 'Reverse Gravity' on an area previously engineered to have 'negative' gravity?

More on topic:
In words that your above average high-schooler can understand (NOT Physics wiz, more English/Biology/Chemistry), why would reversing gravity on a universe-wide scale reverse time? And wouldn't that mean that it would also do so on a smaller scale? Which would mean that objects in the spell are moving up and... uggh... that's not a happy thought.

I think we've managed to kill at least one catwoman by now.

MorkaisChosen
2008-06-02, 06:42 AM
All the stars would explode immediately. They're currently held together by gravity, despite fusion pressure opposing it- reverse the gravity and they explode.

Fun.

DigoDragon
2008-06-02, 08:19 AM
... my head hurts. :smalleek:
I think I'd just rule black holes to be dead magic zones and avoid this issue if it ever comes up in a game. But... some pretty awesome thinking outside that box folks.

monty
2008-06-02, 08:37 AM
I think I'd just rule black holes to be dead magic zones and avoid this issue if it ever comes up in a game.

Aww, that's no fun!

Telonius
2008-06-02, 09:56 AM
Not a physicist here ... but is a black hole actually a single point, or is it more of an area? Because Reverse Gravity only affects a single ten-foot cube per two levels, and only lasts rounds/level. Even if the matter started exploding outwards, would it reach beyond the point where it's affected by the rest of that mass, when the spell ends?

Inyssius Tor
2008-06-02, 10:19 AM
[QUOTE=llamamushroom;4406251]Quick question:
Hypothetically, what happens when you use 'Reverse Gravity' on an area previously engineered to have 'negative' gravity?QUOTE]

That's actually not a problem. The effects overlap, not stack. You'd still have the standard "negative" gravity effect.

MorkaisChosen
2008-06-02, 12:23 PM
Not a physicist here ... but is a black hole actually a single point, or is it more of an area? Because Reverse Gravity only affects a single ten-foot cube per two levels, and only lasts rounds/level. Even if the matter started exploding outwards, would it reach beyond the point where it's affected by the rest of that mass, when the spell ends?

Both. There's a single point at the middle where all the actual substance of the black hole is, but there's an area around it where the gravity is so great that the escape velocity is greater than the speed of light (inside the event horizon).

Chronos
2008-06-02, 04:32 PM
...but there's an area around it where the gravity is so great that the escape velocity is greater than the speed of light (inside the event horizon).The fact that the escape speed at the horizon is c is actually a bit of a coincidence: There are a couple of factors of 2 in the Newtonian and relativistic calculations that happen to cancel out in that particular case. The true defining feature of the event horizon is that there exists no path from the inside of the horizon to the outside, in exactly the same sense that there exists no path from today to yesterday.

Collin152
2008-06-02, 05:55 PM
I think we've managed to kill at least one catwoman by now.

I thought Catwoman went extinct in like, 2004.

ahzreal
2008-06-02, 07:47 PM
It really only breaks, though, if it is infinite. I assume that Reverse Gravity basically just reverses the direction of the force vector for gravity within its area of effect. So if a black hole has a gravitational force with a magnitude of ∞ (within the event horizon) directed toward its center, then reversing it would give it a magnitude of ∞ directed away from the center. This would instantly accelerate all of the matter within the effect to c (that is, the speed of light), moving outward from the black hole, which would break all of the laws of relativity and do bad things to the universe.



By the way, how many catgirls do you think we've killed so far?


Well, the "Reverse Gravity" spell DOES have a given duration, however, combined with a "Permanancy" spell.. :smallbiggrin:

llamamushroom
2008-06-03, 04:08 AM
I thought Catwoman went extinct in like, 2004.

Which is why it's so amazing we've managed to kill one.

Think about it.

Bender
2008-06-03, 07:16 AM
my thoughts on the question:

First, things work different in the absence of real physics. The spell only works on objects that are not attached. Although not specifically mentioned, for ease of gameplay it could be assumed that the ground on which you stand is not affected. You fall upwards, but the earth and rocks on which you stand stay on the ground. In this assumption the main gravity-exerting object is unaffected. This would mean nothing would happen except that the small area of the spell stops attracting things, which probably aren’t even there because they would have been sucked in the hole a long time ago.

Then, all the catgirls in the universe are instantly sucked into the black hole, and we arrive at including certain principles of physics.
I thought the space around the black hole is curved to form an (infinitely deep) hole in space. You could argue that the area of the spell can’t reach deep enough to even reach the hole, but only the space immediately around it, in which case nothing happens.

Suppose the spell does affect the black hole, and gravity is in fact reversed. If the area of the spell is smaller than the event horizon, I’d guess you get a momentary flash of light, which manages to escape (this would explain the mysterious gamma burst astronomers keep seeing), before the black hole reforms. In case the spell area is a perfect sphere, centred perfectly on the black hole, I’d vote for an infinitely thin black hole shell around this area. In case of a small deviation from the required perfection, the black hole would reform to a single point at the edge of the area.
As far as I know, the size of the event horizon depends solely on the mass, thus it doesn’t increase. It probably decreases a little bit due to the portion of light/energy/mass that managed to escape before reformation.

If the area of the spell is larger than the event horizon, you might get a hollow neutron star around the spell area.

If all mass is immediately expelled as light/neutrino’s, the hole just disappears, and the immediate vicinity of the black hole gets a hot shower of high energy radiation, but unless it’s a centre-of-galaxy-size hole, only the nearest star systems get lethal amounts of radiation, which only reaches them years later. And even the mass-of-a-million-suns type holes probably only annihilate life in their galaxy. I don’t know what the effect on stars and planets would be. If most of the radiation are neutrino’s which pass through everything and hardly affect anything, I guess stars are not really affected.

About the reversal of time: gravity slows down time. Wouldn’t reversed gravity speed up time, rather than reversing it?

If gravity is reversed, stars would explode, and every structure in the universe would rip apart, since everything is spinning. Planets would be shredded by lack of centripetal forces to keep them together. Galaxies would drift apart, remnant star gasses shooting out in all directions. In a matter of only a few million years, you would get a kind of very cold and very dark soup, with a very sparse distribution of particles, dust and larger chunks of rock, held together by atomic and electric forces.
Spacecrafts or spacestations would be unaffected.

Man, this became a long post, sorry for that… :smallredface:

Valairn
2008-06-03, 09:20 AM
I always assumed the reason the ground didn't float up away from the earth was that the bottom of the spell was on the ground itself, not under the ground. If the spell was shaped in a sphere and placed around a black hole, you would get something really wonky going on. Since the reverse gravity has a range, the black hole would literally be forced to the outside of the sphere itself, but the gravity outside of the sphere would still think there was a black hole in the center, so in effect you would have created a black hole with an eye in its storm. Since all the mass is forced to the outside of the sphere to oscillate between two paradigms of gravity, on the inside of the spells range you have a black holes worth of gravity pushing out, and the outside of the spell you have a black holes worth of gravity crushing in, you have fundamentally altered the shape of the black hole, what would probably occur is an equilibrium, the range of the spell forces a vector on the mass in the black hole away from the singularity, but outside the range the gravity is still very much pressing in with the same amount of force.

You would in effect create a circle of mass equal to the mass of the black hole with nothing in the center and all mass spread equivalently around the edges. Depending upon the amount of mass in the black hole to begin with the circle itself could be an infinitely dense circle and you just create a very freaky weird bending of space-time. Congratulations!

It must not be ignored though that the gravity outside of the spell is still pointing towards the center of where the black hole was, because the mass is evenly distributed the center is still in the center. Really you didn't change anything, the event horizon may have moved or disappeared, and various other things, but outside of the range of the spell there is still a black holes worth of gravity pointing towards the center of the "black hole".

I hope that makes sense.

Chronos
2008-06-03, 11:05 AM
Really you didn't change anything, the event horizon may have moved or disappeared, and various other things, but outside of the range of the spell there is still a black holes worth of gravity pointing towards the center of the "black hole".There's also a black hole's worth of gravity outside the surface of the Sun, pointing towards the center. Or any other object, for that matter. The gravity of a black hole as a function of distance is the same as for any other object of the same mass. The only difference between a black hole and other objects is that the hole is completely contained within its Schwartzschild radius (the radius of the event horizon), and you can therefore get much closer to a black hole than to anything else of the same mass. So if you go mucking about with the properties of the event horizon, you should expect very dramatic effects.

Valairn
2008-06-03, 11:27 AM
You are right. Of course part of the issue is that what is actually happening past the event horizon can't be observed.

Here's a question, is the distance from the event horizon to the singularity actually infinite, or does it behave more like a limit does in calculus?

monty
2008-06-03, 11:31 AM
Here's a question, is the distance from the event horizon to the singularity actually infinite, or does it behave more like a limit does in calculus?

All infinities are limits. You can never actually reach it.

Valairn
2008-06-03, 11:35 AM
Let me rephrase, A limit approaching a finite number, or a limit approach an infinite number, similar process very different effects.

FlyMolo
2008-06-03, 01:08 PM
Let me rephrase, A limit approaching a finite number, or a limit approach an infinite number, similar process very different effects.

Umm, to quote my physics buddy, "Bad Question No Biscuit." The question makes no sense. Both? Neither? Infinite curvature of spacetime basically breaks all the rules.

Valairn
2008-06-03, 02:00 PM
Yeah, its a bad question. Unfortunately it affects the question of whether the spell can reach the center of the black hole at all to pull off this reality stopping conundrum. If the distance between you and the center of the black hole is actually infinite, you can never get close enough to cast the spell on this singularity itself, no matter what your frame of reference is.

monty
2008-06-03, 03:37 PM
Yeah, its a bad question. Unfortunately it affects the question of whether the spell can reach the center of the black hole at all to pull off this reality stopping conundrum. If the distance between you and the center of the black hole is actually infinite, you can never get close enough to cast the spell on this singularity itself, no matter what your frame of reference is.

A good reason to pick a black hole with a small enough event horizon that you can cover it all with the spell. Then you don't have to deal with those pesky potential infinities.

Bender
2008-06-03, 04:02 PM
A good reason to pick a black hole with a small enough event horizon that you can cover it all with the spell. Then you don't have to deal with those pesky potential infinities.

I think the point is that the spaced is curved in such a way that the actual distance to the singularity is too large, and you can never actually cover the singularity itself, even if you cover the space around it.

Dervag
2008-06-03, 10:20 PM
PERSISTENT TIME STOP!

That or we get a Trousers of Time effect and there are now two universes- one fixed, and one (the one the wizard went into) where the spell never happened (because time going backwards stopped it) and it works normally.

Note: this is more like a science fiction writer's view (not that I am one) than actual coherent physics. Give me a few years to get some degrees and I'll get back to you.So we get the Trousers of Time doing splits or something?


Which is why it's so amazing we've managed to kill one.

Think about it.Yeah. There are now -1 catwomen in the universe.

Collin152
2008-06-03, 10:31 PM
Yeah. There are now -1 catwomen in the universe.

Maybe one was retroactively killed at an earlier point.
Therefore leavign the total at zero.
or, the potential for a Catwoman to exist has been set to -1. Which is to say, when one attempts to exist in this reality, by whatever means, it will instantly cease to exist.

Bender
2008-06-03, 11:55 PM
Maybe one was retroactively killed at an earlier point.
Therefore leavign the total at zero.
or, the potential for a Catwoman to exist has been set to -1. Which is to say, when one attempts to exist in this reality, by whatever means, it will instantly cease to exist.
We are down to a constant number of 42 catwomen. When one is killed, somewhere else one pops into existence. Maybe this could solve the energy crisis...

That, or there are exactly 0.378 catwomen

Chronos
2008-06-04, 12:27 AM
Pshaw, a catgirl is created every time anyone writes a slash fanfic on the Internet. We physicists are necessary to keep the population under control, but I fear we're losing ground.

Infinity_Biscuit
2008-06-04, 01:51 AM
About the form the contents of the black hole would take, I seem to remember reading recently that it was found (or maybe conjectured; I don't remember well) that black holes actually do conserve information. Wouldn't that mean it wouldn't just be randomised forms of mass-energy being released?

Bender
2008-06-04, 03:45 AM
Pshaw, a catgirl is created every time anyone writes a slash fanfic on the Internet. We physicists are necessary to keep the population under control, but I fear we're losing ground.

So teleportation works by using the quatum-connections between twin particles.
creation spells must actually use the mass from air particles, or another plane, because creating it would need a ridiculous amount of energy.
The commoner rail gun is not possible, because at high speeds, the spear would become too heavy for the commoners to hold it.
That should help


About the form the contents of the black hole would take, I seem to remember reading recently that it was found (or maybe conjectured; I don't remember well) that black holes actually do conserve information. Wouldn't that mean it wouldn't just be randomised forms of mass-energy being released?
I think I've read something like that too, theorising about using black holes as supercomputers. I've also read that black holes are rugby-ball shaped, that you could fly through a spinning black hole unharmed, and that you might end up somewhere else entirely (through a wormhole, maybe even to another univers) if you do so.
There are a lot of theories about black holes, that's the fun thing about not knowing what actually happens there, and having no way of checking.
The answer to that question is the same as the answer to any other question involving singularities: Nobody knows.

Kd7sov
2008-06-04, 01:10 PM
Going back to the RG on the universe reversing time into an oscillation:

My first instinct, were I DMing, would be to have entropy not be reversed, but instead work as a sort of temporal friction - over metatime, the oscillations would get "smaller", until oodles of metamillenia later, when they're below the Planck time, everything would sort of gray out.

Unless, of course, other planes weren't affected, in which case there'd likely be some Outsider or planar traveler who could use Wish or some such to stop it.

Chronos
2008-06-04, 01:54 PM
About the form the contents of the black hole would take, I seem to remember reading recently that it was found (or maybe conjectured; I don't remember well) that black holes actually do conserve information. Wouldn't that mean it wouldn't just be randomised forms of mass-energy being released?That was Hawking a few years ago. His argument was mostly just handwaving, though, and he's since retracted it. What exactly happens to the information in a black hole is currently one of the larger mysteries in theoretical physics.

I've also read that black holes are rugby-ball shaped,A spinning black hole is flattened, not elongated, in somewhat the same way that a spinning planet is flattened. Most black holes are expected to have a significant spin on them, but there's no reason you couldn't have a non-spinning hole, which would be perfectly spherical.

...that you could fly through a spinning black hole unharmed, and that you might end up somewhere else entirely (through a wormhole, maybe even to another univers) if you do so.Yes and no... An idealized spinning black hole has a ring singularity instead of a point one, and a path through that ring would take you someplace that you can't reach any other way (which you might as well call a different universe). The two catches are that, first, you'd still be inside the event horizon, and second, any object with nonzero mass which tried it would perturb the black hole away from the idealized case enough that it'd still hit the singularity anyway.

Infinity_Biscuit
2008-06-04, 03:34 PM
That was Hawking a few years ago. His argument was mostly just handwaving, though, and he's since retracted it. What exactly happens to the information in a black hole is currently one of the larger mysteries in theoretical physics.
Ah. Thanks for the clarification!


A spinning black hole is flattened, not elongated, in somewhat the same way that a spinning planet is flattened. Most black holes are expected to have a significant spin on them, but there's no reason you couldn't have a non-spinning hole, which would be perfectly spherical.
How does a singularity have any shape at all, with no volume? Or is this some sort of crazy math thing, and not simplistic geometry?

Chronos
2008-06-04, 04:55 PM
Again, the black hole is more than just the singularity. The singularity of a spinning black hole is a one-dimensional ring, still with zero volume due to its lack of width or thickness. The region within the event horizon, however, is a flattened sphere.

FlyMolo
2008-06-04, 05:04 PM
It really only breaks, though, if it is infinite. I assume that Reverse Gravity basically just reverses the direction of the force vector for gravity within its area of effect. So if a black hole has a gravitational force with a magnitude of ∞ (within the event horizon) directed toward its center, then reversing it would give it a magnitude of ∞ directed away from the center. This would instantly accelerate all of the matter within the effect to c (that is, the speed of light), moving outward from the black hole, which would break all of the laws of relativity and do bad things to the universe.

This is true. And the energy released by rapidly accelerating several solar masses to very significant fractions of the speed of light is enough to seriously break stuff. And by stuff I mean everything.

A good way to set this off without having to be nearby is Ducttape an undead mouse to a pebble. Contigent spell (reverse gravity) on the nearest large(heavy) mass, when the mouse passes the event horizon. That should work, barring something nasty and relativistic. If you release it from far enough away, it should also give you time to run like hell. Greater Teleport, perhaps.

Infinity_Biscuit
2008-06-04, 07:25 PM
The region within the event horizon, however, is a flattened sphere.
Is this the same as saying the event horizon itself is a flattened sphere? I'm having trouble wrapping my head around either the event horizon itself not being a sphere or the region inside the event horizon being shaped differently than the event horizon itself.

monty
2008-06-04, 10:55 PM
Is this the same as saying the event horizon itself is a flattened sphere? I'm having trouble wrapping my head around either the event horizon itself not being a sphere or the region inside the event horizon being shaped differently than the event horizon itself.

I may have it wrong, but my understanding is that the event horizon occupies a particular volume in space, but if you were to pass through it, you wouldn't travel any distance.

Dervag
2008-06-04, 11:10 PM
Is this the same as saying the event horizon itself is a flattened sphere? I'm having trouble wrapping my head around either the event horizon itself not being a sphere or the region inside the event horizon being shaped differently than the event horizon itself.What's happening is that mass distorts the shape of space. The event horizon and the singularity are both geometric phenomena; you can't talk about them as objects with structures in the traditional sense. The singularity has colossal mass, but it's like pure massiveness distilled down to its barest essence.

In general relativity, mass creates gravity by bending the spacetime around it. For objects of 'decent' density, the strength of this bending is such that simple math can give you the acceleration of objects in the vicinity due to the bending. This is the approximation method Newton hit on in his groundbreaking work on astronomy in the 1600s. Newton's method actually does predict the idea of a black hole for a sufficiently dense object, assuming a finite speed of light, but it utterly fails to predict the black hole's real properties.

However, in the high density case, the curvature of spacetime becomes so great that freakiness starts to happen. You can't use Newton's laws as an approximation very well if there's something extremely dense about, just as you can't use them for speeds near the speed of light.

What Chronos is talking about is geometry that results from solving the equations of general relativity for the mass in question. If your 'black hole' (referring to the entire system of event horizon and singularity as if it were an object) has no angular momentum, the mass forms a point, surrounded by a spherical bubble of spacetime that is eternally closed off from the rest of the cosmos. You can enter the bubble from outside, but you can't escape it.

As Chronos says, there is no path from inside the event horizon to outside it, any more than there is from tomorrow to yesterday. And for the exact same reasons. Black holes are so dense that they bend space and time together into freakish twisty shapes. So they essentially create an eternal region of "tomorrow" inside their event horizon; you can't come back from it any way you try.

If the black hole is spinning, the stable solution to the equations is a little different, with a hoop-shaped singularity (after all, to have angular momentum it must have size; a point can't rotate about its axis). And the hoopiness of the singularity changes the shape of the inaccessible "bubble," turning it into an oblate spheroid (a flattened sphere).

But yeah, this is all 'freaky geometry.'

Infinity_Biscuit
2008-06-04, 11:25 PM
What's happening is that mass distorts the shape of space. The event horizon and the singularity are both geometric phenomena; you can't talk about them as objects with structures in the traditional sense.
I know. That's why when the Voyager found a crack in an event horizon, it amused me so much. What's next, a hole in the number two?


If the black hole is spinning, the stable solution to the equations is a little different, with a hoop-shaped singularity (after all, to have angular momentum it must have size; a point can't rotate about its axis). And the hoopiness of the singularity changes the shape of the inaccessible "bubble," turning it into an oblate spheroid (a flattened sphere).
This is the part that's confusing me. Wouldn't it still be a sphere defined from the center of mass, since it's caused by the gravity and not, say, tides? Is this explained by tensors or other voodoo witchcraft, or is it something I should understand just with undergrad physics?

Chronos
2008-06-05, 12:08 AM
(after all, to have angular momentum it must have size; a point can't rotate about its axis)Careful, there... You don't want to confuse the poor fellow when he encounters quantum mechanical spin. Well, confuse him any more than he will be inevitably anyway.


This is the part that's confusing me. Wouldn't it still be a sphere defined from the center of mass, since it's caused by the gravity and not, say, tides? Is this explained by tensors or other voodoo witchcraft, or is it something I should understand just with undergrad physics?The important thing to realize here is that centrifugal force is exactly as real as gravity, and works essentially the same way. Just as centrifugal force distorts the shape of the Earth, in a similar way it also distorts the shape of a black hole.

Bender
2008-06-05, 03:51 AM
As Chronos says, there is no path from inside the event horizon to outside it, any more than there is from tomorrow to yesterday. And for the exact same reasons. Black holes are so dense that they bend space and time together into freakish twisty shapes. So they essentially create an eternal region of "tomorrow" inside their event horizon; you can't come back from it any way you try.
Couldn't you teleport out? If they ever find a way to teleport more than a proton. In D&D teleporting out shouldn't be a problem. Outside the hole, time would have gone faster than for you of course.

Careful, there... You don't want to confuse the poor fellow when he encounters quantum mechanical spin. Well, confuse him any more than he will be inevitably anyway.
QFT. Is there any way to look at that (or anything else with 'quantum' in its name) and not be discombobulated?

Infinity_Biscuit
2008-06-05, 02:29 PM
Careful, there... You don't want to confuse the poor fellow when he encounters quantum mechanical spin. Well, confuse him any more than he will be inevitably anyway.
Don't worry; already there. I've done three semesters of quantum, just not much at all in general relativity (and that little bit wasn't on the final... :smalltongue:).


The important thing to realize here is that centrifugal force is exactly as real as gravity, and works essentially the same way. Just as centrifugal force distorts the shape of the Earth, in a similar way it also distorts the shape of a black hole.
Can the centrifugal force also distort spacetime like gravity? If so, that would clear it up for me, since my main sticking point is how centrifugal force changes the shape of the event horizon, something that is simply the warping of light cones.

Bender
2008-06-05, 03:17 PM
Can the centrifugal force also distort spacetime like gravity? If so, that would clear it up for me, since my main sticking point is how centrifugal force changes the shape of the event horizon, something that is simply the warping of light cones.

Centrifugal forces in fact don't really exist. They are virtual forces, manifesting in rotating reference frames. It's the absence of a sufficient centripetal force that rips rotating things apart. Inertia of course has a close relation to gravity (inertial mass being equal to gravitational mass), but I don't know whether that has any implications on space-time

Chronos
2008-06-05, 03:30 PM
Centrifugal forces in fact don't really exist. They are virtual forces, manifesting in rotating reference frames.The same is true of gravity. If you want to call gravity a "real" force (whatever that means), then you have to say the same of the centrifugal force.


Couldn't you teleport out? If they ever find a way to teleport more than a proton. In D&D teleporting out shouldn't be a problem. Outside the hole, time would have gone faster than for you of course.D&D teleportation doesn't allow time travel. I think there are a few high-level psionic powers that do, but not just the plain ordinary fifth-level spell. A Wish could probably do it, though, based on the clause about transporting travellers regardless of local conditions or impediments.

Collin152
2008-06-05, 07:59 PM
The same is true of gravity. If you want to call gravity a "real" force (whatever that means), then you have to say the same of the centrifugal force.

D&D teleportation doesn't allow time travel. I think there are a few high-level psionic powers that do, but not just the plain ordinary fifth-level spell. A Wish could probably do it, though, based on the clause about transporting travellers regardless of local conditions or impediments.

Teleport Through Time teleports through time.
Ninth level spell.

Or Plane Shift somewhere else. Preferably with a time trait that will help you sort things out.
Like a reverse one.

Chronos
2008-06-05, 08:45 PM
Teleport Through Time teleports through time.
Ninth level spell.That must be a real headache for DMs.

Plane Shift wouldn't work, though. There are actually some theories in physics involving what D&D would call other planes, and in all of them, black holes are still fully enclosed by a horizon. Extrapolating from those theories to what's known of the D&D cosmology, you could probably Plane Shift to the Ethereal or Shadow planes, and possibly the Astral, but you'd still be inside a black hole on those planes, and you couldn't shift to any other planes at all.

Collin152
2008-06-05, 08:54 PM
That must be a real headache for DMs.


Well, you need a flower that hasn't been bothered since the time you want to get back to.
So it's kinda hard to cast.

Dervag
2008-06-05, 09:01 PM
Careful, there... You don't want to confuse the poor fellow when he encounters quantum mechanical spin. Well, confuse him any more than he will be inevitably anyway.OK, point. That said, doesn't "spin" drop out of the Dirac relativistic-quantum-mechanical description of particles? Rather than being an example of a physical point mass with zero spatial extent being described as spinning like a top?

Or:

Do we have to interpret spin as a geometric point bearing angular momentum? Even if relativistic constraints make it impossible for the particle to bear its angular momentum by spinning like a top, are we forced to accept that quantum mechanical spins can be applicable to a pure geometric point?

Chronos
2008-06-05, 09:19 PM
Well, electrons appear to every measurement we can make to be point particles, and they're certainly small enough that if spin is "spinning like a top", then the surface of the electron (if it has one) would have to be going faster than the speed of light.

And you don't have to accept any particular interpretation of anything in quantum mechanics, but spin is definitely a form of angular momentum, and there's no indication that it's constrained by things like the size of the particle.

Bender
2008-06-06, 12:44 AM
The same is true of gravity. If you want to call gravity a "real" force (whatever that means), then you have to say the same of the centrifugal force.
No.
To have a force, you need two bodies exerting the force on each other. In the case of gravity, that is the case. In an accelerating frame of reference (such as a rotating one), the inertial forces are not exerted by anything, they are just a mathematical representation of the fact that the reference is accelerating, and they affect every object in that frame of reference.
I don't know enough about quantum physics to know about some strange quantum force that are not exerted by anything (which would violate conservation of energy), but the centrifugal force is, as far as I know, no strange quantum effect.

About getting out of a black hole: if he can survive long enough, could he cast genesis and escape from his own demiplane to another, or would the demiplane only connect to the inside of the black hole?
Otherwise, a reverse gravity on himself (but not on the singularity, to avoid side effects) should get him out long enough to teleport away.

Chronos
2008-06-06, 12:57 AM
An object experiencing a centrifugal force is not feeling a force exerted by anything; it only appears to be under the effect of a force as a result of the non-inertial reference frame you're describing it in. Likewise, an object experiencing a gravitational force is not feeling a force exerted by anything; it only appears to be under the effect of a force as a result of the non-inertial reference frame you're describing it in. In either case, if you switch to an inertial reference frame, you'll discover that there is no force at all in that frame, which is consistent with the fact that there is nothing exerting a force. This has absolutely nothing to do with quantum mechanics, since general relativity and quantum mechanics appear at present to be irreconcilable.

Bender
2008-06-06, 06:28 AM
An object experiencing a centrifugal force is not feeling a force exerted by anything; it only appears to be under the effect of a force as a result of the non-inertial reference frame you're describing it in. Likewise, an object experiencing a gravitational force is not feeling a force exerted by anything; it only appears to be under the effect of a force as a result of the non-inertial reference frame you're describing it in. In either case, if you switch to an inertial reference frame, you'll discover that there is no force at all in that frame, which is consistent with the fact that there is nothing exerting a force. This has absolutely nothing to do with quantum mechanics, since general relativity and quantum mechanics appear at present to be irreconcilable.
I'm not entirely certain I'm following, I've only got rudimentary knowledge of general relativity (but extended knowledge on mechanics).
What exactly do you mean with a non-inertial reference frame? Is it a frame that is not accelerating? In that case, there is no centrifugal force, nor does an object appear to be under the effect of it.

Now gravity is a real force when the frame is not accelerating, and it is caused by the mass of an object: it has a cause. Centrifugal force doesn't have a cause, it is a mathematical tool. At least, that's the case in Newtonian mechanics. I didn't know general relativity covered centrifugal forces.

I'm of to vacation now, so I don't know whether I'll be able to continue to contribute to this thread. I enjoyed learning from your insights in physics.

Mr. Friendly
2008-06-06, 07:02 AM
Errm...

How would you cast Reverse Gravity on the core of a black hole without being, you know, condensed.

Chronos
2008-06-06, 02:40 PM
Now gravity is a real force when the frame is not accelerating, and it is caused by the mass of an object: it has a cause. Centrifugal force doesn't have a cause, it is a mathematical tool. At least, that's the case in Newtonian mechanics. I didn't know general relativity covered centrifugal forces.Not in the context of general relativity. GR makes the revolutionary assumption that acceleration is what an accelerometer reads. So you and I, sitting in our chairs in front of the computer, are continually accelerating upwards at 9.8 m/s2, and as a result of this acceleration, we think there's a gravitational force on us. The astronauts on the ISS, meanwhile, aren't accelerating, and as a result, don't measure any gravity.

Zeful
2008-06-06, 03:15 PM
That really doesn't describe it that well. I'd rather go with something like "rapidly expanding sphere of absolute destruction of everything everywhere" or something like that. I mean, can you really even conceive of what an arbitrary quantity of matter moving at the speed of light can do?

Actually if the black hole was infinite and reverse gravity managed to encompass the entire core (not that hard, it's much smaller than a 5x5 cube) then the matter would be permanently accelerating outward at an infinite rate in an instant, being converted to energy (E=mc2 anyone?) and sending a wave of destruction backward through time (as it's accelerating at an infinite rate, it surpasses the speed of light by the power of infinity) destroying the freakin' big bang before it formed. This would also annihilate any particles vibrating differently, destroying the upper and lower energy levels (if they exist). And due to the constant acceleration of the energy, nothing can ever be live there again.

In short: Nothing will ever be the same again.

Collin152
2008-06-06, 03:31 PM
Actually if the black hole was infinite and reverse gravity managed to encompass the entire core (not that hard, it's much smaller than a 5x5 cube) then the matter would be permanently accelerating outward at an infinite rate in an instant, being converted to energy (E=mc2 anyone?) and sending a wave of destruction backward through time (as it's accelerating at an infinite rate, it surpasses the speed of light by the power of infinity) destroying the freakin' big bang before it formed. This would also annihilate any particles vibrating differently, destroying the upper and lower energy levels (if they exist). And due to the constant acceleration of the energy, nothing can ever be live there again.

In short: Nothing will ever be the same again.

In short, destroying reality.
Like I originally said.

dwagiebard
2008-11-19, 05:29 PM
Well, assuming we can use Hawking radiation as a model, you'll start off with all sorts of crazy things, but once the dust settles and the unstable particles have decayed, you'll probably have mostly neutrinos (about 80%), followed by light, followed by a not insignificant amount (a few percent) of gravitational waves. Neutrinos end up dominating over light mostly by virtue of the fact that there are more kinds of neutrinos than photons, and everything else will either decay away, or annihilate with its antiparticles.
The answer to that question is the same as the answer to any other question involving singularities: Nobody knows.

Emphasis mine.

Neutrinos would just pass through everything, right? And light isn't particularly deadly, and gravitatinal waves probably wouldn't do anything too horrific. So what happened to the matter, exactly? All the stuff that was eaten by the black hole, wouldn't it still be there?

monty
2008-11-19, 05:49 PM
It's a strange feeling, seeing my own thread being raised as a zombie.

shadow_archmagi
2008-11-19, 06:07 PM
That was Hawking a few years ago. His argument was mostly just handwaving, though, and he's since retracted it.

I seem to recall reading something in one of his books about black holes converting negative energy to real energy...

Collin152
2008-11-19, 07:27 PM
It's a strange feeling, seeing my own thread being raised as a zombie.

It's strange seeing that I was the last living member before its Animation...

Lycan 01
2008-11-19, 08:10 PM
Thread necromancy is fun. But why this thread?



Oh, btw, I came up with my own paradox. What if Cthulhu tries to eat a guy, and the guy carves an Elder Sign into his chest just as Cthulhu drags him into his mouth?

Does Cthulhu spit him out? Does Cthulhu get a belly ache? Does the guy's undigested torso wash up on a deserted beach a few days later? Does the Great Old One contract an unholy case of explosive digestive issues? The possibilities are limitless! :smallbiggrin:

Prometheus
2008-11-19, 09:07 PM
It's a strange feeling, seeing my own thread being raised as a zombie.
As you call out to it, something seems wrong. As you approach, it's ungainly shambling dispels all illusions that you might had about it's belonging to the realm of the living. Looking upon the dessicated abomination of the friend you once knew, you have one question in your mind. "How? How could this be?"

Sorry, I just thought it would be amusing if thread necromancy was a theatrical as real necromancy (well not "real" necromancy, but how necromancy would be were it to be "real" in a world where things like that are "real").

Daracaex
2008-11-19, 09:53 PM
Not reading this whole thing, but I believe the spell would never get to the core of the black hole because time gets infinitely slower as the spell approaches the singularity.