Weight

[PersonMan]

Assuming that we aren't being restrained by all that physics nonsense, how dense would an approximately 8-foot-long long sword-esque weapon weigh? It's meant to be a two-handed quasi-reach weapon, as the handle along is around 2 feet long.

Here's the catch-it's made up of neutron star matter. Once again, yes, I'm ignoring physics. This will be BY MAGIC in the situation it appears in, I just want to know the weight.

Alright, seeing as it depends on where in the star, I'm thinking around 4.4 x 10^17. I am, however, unsure of how to calculate the number of square meters in this weapon.

[Yarram]

I would guesstimate around 15-20 lb?

[PersonMan]

I would guesstimate around 15-20 lb?

Unhappy face.

I was hoping for something absolutely ridiculous, but then again I am talking about a rather long sword, as opposed to a giant hammer.

Oh, well.

[Shas aia Toriia]

Since a star is, generally speaking, just a whole bunch of really hot gas (as far as I know), the weapon would weigh however much the handle weighs.

[Mando Knight]

8 feet is around 2.5 meters. Let's assume a constant blade width of 8 cm, a maximum thickness of 6 cm, and a parallelogram cross-section.

This yields an overall volume of about 0.012 m³. Assuming your value of 4.4e17 kg/m³, the sword's mass is about 5.28e15 kg, or about half the mass of Phobos and around 4 times that of Deimos.

It is not a sword. It is an asteroid compressed into the size and shape of an oversized sword.

[Haruki-kun]

Since a star is, generally speaking, just a whole bunch of really hot gas (as far as I know), the weapon would weigh however much the handle weighs.

Not neutron stars. (http://en.wikipedia.org/wiki/Neutron_Star)

[PersonMan]

Since a star is, generally speaking, just a whole bunch of really hot gas (as far as I know), the weapon would weigh however much the handle weighs.

Seeing as a cubic meter of the stuff around the mid-density zone of a neutron star weighs 44x10^16 kilograms, I'd still say that it'd be fairly heavy.

Also, I mean the entire weapon is made of this. It's essentially meant to cut through more than any sword could reasonably cut through.

It's also solid.

[PersonMan]

8 feet is around 2.5 meters. Let's assume a constant blade width of 8 cm, a maximum thickness of 6 cm, and a parallelogram cross-section.

This yields an overall volume of about 0.012 m³. Assuming your value of 4.4e17 kg/m³, the sword's mass is about 5.28e15 kg, or about half the mass of Phobos and around 4 times that of Deimos.

It is not a sword. It is an asteroid compressed into the size and shape of an oversized sword.

Yes. This is what I was hoping for! Very large numbers with letters variables in them!

Thank you, Knight of the Mando!

[Mando Knight]

Seeing as a cubic meter of the stuff around the mid-density zone of a neutron star weighs 44x10^16 kilograms, I'd still say that it'd be fairly heavy.

Also, I mean the entire weapon is made of this. It's essentially meant to cut through more than any sword could reasonably cut through.

It's also solid.

It does not cut. It annihilates whatever it's set upon by sheer momentum. Enemies cannot avoid it, for it exerts massive gravitational forces. The user cannot wield it, as it puts even an advanced epic dragon beyond its drag load. It's a block of death if it manages to move.

[RS14]

It's also solid.

Nope.


The equation of state (EOS) for a neutron star is still not known. It is assumed that it differs significantly from that of a white dwarf, whose EOS is that of a degenerate gas which can be described in close agreement with special relativity. However, with a neutron star the increased effects of general relativity can no longer be ignored. Several EOS have been proposed (FPS, UU, APR, L, SLy, and others) and current research is still attempting to constrain the theories to make predictions of neutron star matter.

In short it is exotic. See also, Degenerate Matter (http://en.wikipedia.org/wiki/Degenerate_matter).

Also, I would guess that it will tend to evaporate rapidly (if not explosively) if not constrained by the immense gravitational attraction of the star.

[Capt Spanner]

Also, I would guess that it will tend to evaporate rapidly (if not explosively) if not constrained by the immense gravitational attraction of the star.

May I refer you to:


I'm ignoring physics. This will be BY MAGIC in the situation it appears in.

[RS14]

May I refer you to:


I'm ignoring physics. This will be BY MAGIC in the situation it appears in, I just want to know the weight.



Well yes, we got that. It's just density*volume, as Mando Knight posted.

There's nothing wrong with discussing the other ramifications now that the question is resolved.

[Dr.Epic]

Here's the catch-it's made up of neutron star matter. Once again, yes, I'm ignoring physics. This will be BY MAGIC in the situation it appears in, I just want to know the weight.

Couldn't you then just make it weigh however much you want?

[Flickerdart]

8 feet is around 2.5 meters. Let's assume a constant blade width of 8 cm, a maximum thickness of 6 cm, and a parallelogram cross-section.

This yields an overall volume of about 0.012 m³. Assuming your value of 4.4e17 kg/m³, the sword's mass is about 5.28e15 kg, or about half the mass of Phobos and around 4 times that of Deimos.

It is not a sword. It is an asteroid compressed into the size and shape of an oversized sword.
How can a sword blade be 6cm thick without being reclassified as a club?

[Soterion]

Well, it probably could be wielded, since we already know one exists: Roy's sword. Okay, technically it's only partially "starmetal", but it's still a usable weapon made from "metal" from a star.

[Stars are composed of gas. Even things like titanium exist in gaseous form inside stars. So therefore any solid called a "metal" that comes from stars is clearly ludicrous. Neutron stars, on the other hand, are composed of a kind of "ubersolid." Which means, if you were to somehow lever a chunk away from a neutron star and keep it from evaporating, you could make it into a sword. Yes, I am aware that technically starmetal comes from meteors, but having starmetal = neutron-degenerate matter is much cooler.]

[Jimorian]

Not only could nobody lift it, but it would immediately plunge towards the center of the planet in question, boring through the crust and mantle much like a rock falls through air. It would oscillate back and forth, failing to reach the surface by a little more each time until friction finally wins out and it settles at the center of the planet core.

The gravitational pull of it moving around inside the planet would cause MASSIVE earthquakes and tsunamis that would render the surface practically unlivable.

(I find that if you don't ignore the physics, you get even cooler effects :smallamused:)

[Mando Knight]

How can a sword blade be 6cm thick without being reclassified as a club?

Maximum thickness, and it was an off-the-top-of-my-head number for an 8ft long sword. It probably is a stupid number, but so is 8 feet for a blade's length.

[Jimorian]

6mm would actually make sense for thickness.

[RS14]

Maximum thickness, and it was an off-the-top-of-my-head number for an 8ft long sword. It probably is a stupid number, but so is 8 feet for a blade's length.

Basing the volume off of that of a greatsword from the SRD (8lb/(7.85g *cm^3)), I get 2*10^14kg using the above figure for density.

[Flickerdart]

Considering that this sword is made out of an ultra-dense material, it could be 6nm thick and still not break. Having a 2.5m long sword that's sharper than a razor and invisible when turned sideways is considerably cooler than having a 2.5m long metal bar.

[RS14]

The gravitational pull of it moving around inside the planet would cause MASSIVE earthquakes and tsunamis that would render the surface practically unlivable.


I don't know about this--it's about 10 orders of magnitude lighter than the earth. At about 60 meters, it will cause 1g gravitational acceleration, but this will rapidly drop off as you move farther away. From 1km away, it will be basically negligible. It would be a good idea to stay of of mines and buildings if it's going to be nearby, but I don't think it will have much effect beyond perhaps triggering a few already delicate faults.


Considering that this sword is made out of an ultra-dense material, it could be 6nm thick and still not break. Having a 2.5m long sword that's sharper than a razor and invisible when turned sideways is considerably cooler than having a 2.5m long metal bar.

Density and strength are not the same. Gold is dense, but very soft.

[Mando Knight]

Considering that this sword is made out of an ultra-dense material, it could be 6nm thick and still not break.

Maybe. It depends on the Young's Modulus. Probably not, unless it's orders of magnitude less flexible than diamond.

Using an elastic material with a tensile/compressive Young's Modulus equal to the compressive modulus for diamond (roughly 1200 GPa) and a length of 2.5 m, width of 8 cm, and constant thickness of 6 nm, the force required to buckle the bar is less than 1 nano-Newton. (2.729e-15 N, to be a bit more precise)

Increasing the size to 6 cm increases the buckling load to about 2.729 mega-Newtons.

Both of these mean that the blade will buckle under its own weight. Oops.

[Forever Curious]

(I find that if you don't ignore the physics, you get even cooler effects :smallamused:)

This pretty much wins.

[Flickerdart]

I should think this stuff would be considerably stronger than diamond, never mind gold.

[Soterion]

Maybe. It depends on the Young's Modulus. Probably not, unless it's orders of magnitude less flexible than diamond.

Using an elastic material with a tensile/compressive Young's Modulus equal to the compressive modulus for diamond (roughly 1200 GPa) and a length of 2.5 m, width of 8 cm, and constant thickness of 6 nm, the force required to buckle the bar is less than 1 nano-Newton. (2.729e-15 N, to be a bit more precise)

Increasing the size to 6 cm increases the buckling load to about 2.729 mega-Newtons.

Both of these mean that the blade will buckle under its own weight. Oops.

Neutronium nanotubes! That's the solution! Like carbon nanotubes, only with neutronium! And everyone knows that carbon nanotubes can do anything!

[PersonMan]

...I see.

Well, then, I'll just ignore physics use MAGIC and some sort of gravity/magnetic field to explain away any stuff that doesn't result in a massively overpowered sword. Like plunging into the center of the planet.

...Wait. What a wonderful idea for a cursed item!

[Erts]

I must ask, exactly why do you need to know this?

Mando Knight is right: this is not a practical weapon by any means at all, in fact, its not even a weapon.

[PersonMan]

I want a sword that can cut through anything. I decided that absurd density was the way to go. I also decided that Osmium would quite possibly not be dense enough.

So I used the densest(or most dense, whatever) material I could think of.

[Mando Knight]

I should think this stuff would be considerably stronger than diamond, never mind gold.

To survive the force of its own gravitational reaction with the earth, it would need to be about a dozen orders of magnitude stiffer than steel or titanium. And that's for an 8 cm x 6 cm x 2.5 m rectangular bar.
Neutronium nanotubes! That's the solution! Like carbon nanotubes, only with neutronium! And everyone knows that carbon nanotubes can do anything!
I... you... it... :smallsigh:
A Wizard Did It (http://tvtropes.org/pmwiki/pmwiki.php/Main/AWizardDidIt). That's the only explanation I'll accept. Neutronium nanotubes won't be the answer.

[RS14]

Mando Knight is right: this is not a practical weapon by any means at all, in fact, its not even a weapon.

"Go beyond the impossible and kick reason to the curb! That's the Team Gurren way!"


I should think this stuff would be considerably stronger than diamond, never mind gold.

Why?

[Soterion]

I want a sword that can cut through anything.

"A more elegant weapon from a more civilized age."

[Erts]

Well, obsidian, due to it's lack of a crystalline structure, can be sharpened down to the molecule. Of course, due to this absence, it is not strong and breaks fairly easily.

[Flickerdart]

Why?
Because it`s more interesting that way.

[Quincunx]

What I want to know: will this neutron-star-forged item radiate as does its parent substance? The sword may sing, the sword may sing, for those who have ears to hear--and those who have listened to the song of the celestial spheres have traditionally been a bit enlightened and/or insane.

If you're going to mix this much science into your magic (and "I want a sword that can cut through anything" is purely a request of magic), though, could you mix in a technobabble explanation for why the sword doesn't fly apart when removed from the heavens?

[PersonMan]

What I want to know: will this neutron-star-forged item radiate as does its parent substance? The sword may sing, the sword may sing, for those who have ears to hear--and those who have listened to the song of the celestial spheres have traditionally been a bit enlightened and/or insane.

If you're going to mix this much science into your magic (and "I want a sword that can cut through anything" is purely a request of magic), though, could you mix in a technobabble explanation for why the sword doesn't fly apart when removed from the heavens?

At this point, a God Did It. Some war god wants people to kill eachother to get a sword that can kill people very well, so he keeps it from flying apart and/or destroying the world.

[Brother Oni]

Mando Knight is right: this is not a practical weapon by any means at all, in fact, its not even a weapon.

I'm fairly sure if you give the item to a bunch of players, they'll wrangle some way to use it as one.

Off the top of my head, portable hole, fly above the target, then upend the hole. Should make a big dent in something. :smallbiggrin:

Hulking hurler fetch toy?

[Mercenary Pen]

I'm fairly sure if you give the item to a bunch of players, they'll wrangle some way to use it as one.

Off the top of my head, portable hole, fly above the target, then upend the hole. Should make a big dent in something. :smallbiggrin:

Hulking hurler fetch toy?

Far better to use a load of neutron-degenerate slingshot for that though (at least the portable hole trick)?

[paddyfool]

So... ways this could work:


The starblade: A weapon of the gods, held in magical stasis in a sacred place to whichever god created it. And unless a god picks it up, it pretty much just sits there.
Epic hulking hurler's favourite projectile: Stick returning on it. Kill anything, anywhere.
Trap 1: You find a sword sitting on an alternate plane/specially enchanted room/whatever that has no gravity. If you take it back to a place with gravity, it tears free of any attachments and falls straight downwards, killing anything it hits along the way.
Trap 2: You find a sword held rigidly between two immovable rods. It's balanced so that if you turn either one of them off, it'll swing downwards and bisect anyone standing in the obvious place to do so on its way to the earth's core. Reflex save or die.
Trap 3: The sword is enchanted to have no more than ordinary weight for the bearer, and functions as an exceedingly deadly weapon until it gets hit with a dispel, enters an antimagic field, etc. In which case, it detonates, as such matter is unstable in any normal environment. Reflex save or take loadsadamage in a wide radius.

[Knaight]

Maximum thickness, and it was an off-the-top-of-my-head number for an 8ft long sword. It probably is a stupid number, but so is 8 feet for a blade's length.

However, there have been 6-7 foot long swords historically, as early as the early renaissance, a reasonable weapon is only 12.5% smaller in that dimension. However, 6 centimeters is absurdly thick, .3 centimeters is far more believable (There were significantly thicker swords, but .3 isn't unreasonable thin, and the math works out well). A reasonable thickness is 95% smaller in that dimension. 8 cm is also very wide, 3 cm is more likely, 4 cm also showed up. Using 4 cm, a reasonable thickness is 50% smaller than the listed value.

Keeping the proportions more in line: 8 feet long, 4.6 cm wide, .34 cm thick.

Rounded: 8 feet long, 4.5 cm wide, .35 cm thick.

Rounded Metric: 2.5 meters long, 4.5 cm wide, 3.5 mm thick(typical of swords, bump it up to 6.5 mm if need be.)

Rounded "Standard" 8 feet long, 1 7/8 in wide, 1/8 inch thick(typical of swords, bump it up to 1/4 if need be.)

[Manga Shoggoth]

Well, obsidian, due to it's lack of a crystalline structure, can be sharpened down to the molecule. Of course, due to this absence, it is not strong and breaks fairly easily.

And probably blunts fairly easily as well...

[ForzaFiori]

Keeping the proportions more in line: 8 feet long, 4.6 cm wide, .34 cm thick.

Rounded: 8 feet long, 4.5 cm wide, .35 cm thick.

Rounded Metric: 2.5 meters long, 4.5 cm wide, 3.5 mm thick(typical of swords, bump it up to 6.5 mm if need be.)

Rounded "Standard" 8 feet long, 1 7/8 in wide, 1/8 inch thick(typical of swords, bump it up to 1/4 if need be.)

I used similar numbers, obtained off a website. The only difference is an extra 1/8th of an inch in width. as for the weight of the sword, here's my calculations.

An 8 foot sword, assuming it is, in other ways, like a two hander out of the Renaissance period (2 inches wide, average of 1/8 of an inch tall), would have a volume of about 24 cubic inches (96X2X(1/8)). That is 393.289 mL. 5 mL (about a teaspoon) of neutron star weighs 5.5×10^12 kg (or 550,000,000,000kg)

there are 78.6578 (393.289/5) teaspoons of material in that sword, so if you multiply that by the weight of the sword, you should get your answer.

The weight?
43,261,790,000,000kg. 43 Trillion, 261 billion, 790 million kilograms.

That is, if my math is correct

[Flickerdart]

What's the STR you need to carry that as a Heavy, Medium or Light load?

[RS14]

What's the STR you need to carry that as a Heavy, Medium or Light load?

Seems to be 209, 212, or 217 respectively.

(Log4(X/Y)*10+29)

[PersonMan]

47,587,969,000 standard tons. Oh my.

So 95,175,938,000,000 pounds. Yeesh.

217 Strength, huh? So a Strength bonus of +103.

So as a two-handed weapon it would deal XdY+154 points of damage, assuming you needed to carry it as a light load to use the weapon.

Well...Yeah.