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Aerogel (aka "solid smoke") was the lightest so far, at 1mg/cc[1] . The density of air is 1.2 mg/cc. FTA: "The substance weighs just 0.2 milligrams per cubic

by ajays 14y ago

Aerogel (aka "solid smoke") was the lightest so far, at 1mg/cc[1] . The density of air is 1.2 mg/cc. FTA: "The substance weighs just 0.2 milligrams per cubic centimeter" So why doesn't this thing just fly away, if its density is 0.2 mg/cc ? [1] http://en.wikipedia.org/wiki/Aerogel http://en.wikipedia.org/wiki/Aerogel

jws 14y ago
I suspect it is 0.2mg/cc when weighed in a vacuum. It does point out a blurry line between substance and structure. At some point, the voids in the material get large enough that you would call it a structure, for instance, if you outlined a soccer ball in fine copper wire and removed the soccer ball it would certainly be even lighter than this, but you wouldn't call it a substance.
- mseebach 14y ago
  > It does point out a blurry line between substance and structure. On the Aerographite wikipage it's called a "structural material".
- ars 14y ago
  > It does point out a blurry line between substance and structure. It's not new. What is the density of a boat? The density of the boat as a whole is lower than water - so it floats. But if you could only the materials it's made of they are all heavier. So you have to know what you are describing.
  - ChuckMcM 14y ago
    Exactly and a boat only 'floats' because it holds out the water and thus establishes a pressure differential. If you could put one of these things in a vacuum chamber, then put a seal around the outside of it, and then take it out, it would float. Except what it would really do is compress. And from the article it looks like it would compress to a size which put it into the 3 - 5 mg/cc range if not higher. That said, in Neal Stephenson's diamond age they used vacuum balloons as a floatation device. something that I hope we can build at some point.
- Zenst 14y ago
  maybe, though I do wonder how it compares with belly-button fluff in terms of lightness and strength. joke aside how durable is it as by definition it will be extreemly brittle andthe video does seem to indicate that with bits breaking off. If they made round ablls then structurely it would be a little bit more robust. I do wonder what use it could actualy be though. Not very strong, ok it's light but it's not much stronger than air going by that video. I do wonder if you could make a static drawn bellows with this to move air, but thats me being geek. Anybody know what uses this could have beyond coffins for ants sent via beemail! Anybody know a use?
  - Ralith 14y ago
    > by definition it will be extreemly brittle By what definition? Because according to Wikipedia, it's just the opposite: https://en.wikipedia.org/wiki/Aerographite#Structure_and_properties https://en.wikipedia.org/wiki/Aerographite#Structure_and_pro...
    - Zenst 14y ago
      Definition I was using was that is was a very the structure has alot of air gaps and that the video shows bits breaking of just from a little bounce. That said brittle is not realy scientific so I'll bow to that and kudos for the wiki link, covers potentual usage as well - thank you.
      - Ralith 14y ago
        That's an observation.
beambot 14y ago
LoL. I had the exact same thought [1], but you managed to finish your comment while I was still away reading about aerogel. ;-) Incidentally, there was a "carbon nanotube aerogel" that (AFAIK) has the exact same composition as this one and is listed at 1.5 mg/cc [2]. Weighing in a vacuum would seem a bit sensationalistic IMO. [1] http://news.ycombinator.com/item?id=4261353 http://news.ycombinator.com/item?id=4261353 [2] http://www.sciencemag.org/content/323/5921/1575.full http://www.sciencemag.org/content/323/5921/1575.full
will_work4tears 14y ago
"So why doesn't this thing just fly away, if its density is 0.2 mg/cc ?" Static friction? It probably would float for some time in air if it wasn't touching something and there is no breeze.
- stephengillie 14y ago
  In the video (from the article), they wafted up and down between the static-magnetic pull of a wand and the pull of gravity. But they don't stay in the air for long.
- ars 14y ago
  > Static friction? It probably would float for some time in air if it wasn't touching something and there is no breeze. No. The atoms of carbon are still heavier than air, and no type of structure can alter that. However it can be blown by a breeze and stay up that way - same way a cloud, which is heavier than air, stays up due to wind.
  - dasil003 14y ago
    Uh, I'm pretty sure clouds don't float because of wind.

by ajays 14y ago

jws 14y ago

I suspect it is 0.2mg/cc when weighed in a vacuum. It does point out a blurry line between substance and structure. At some point, the voids in the material get large enough that you would call it a structure, for instance, if you outlined a soccer ball in fine copper wire and removed the soccer ball it would certainly be even lighter than this, but you wouldn't call it a substance.

mseebach 14y ago
> It does point out a blurry line between substance and structure. On the Aerographite wikipage it's called a "structural material".
ars 14y ago
> It does point out a blurry line between substance and structure. It's not new. What is the density of a boat? The density of the boat as a whole is lower than water - so it floats. But if you could only the materials it's made of they are all heavier. So you have to know what you are describing.
- ChuckMcM 14y ago
  Exactly and a boat only 'floats' because it holds out the water and thus establishes a pressure differential. If you could put one of these things in a vacuum chamber, then put a seal around the outside of it, and then take it out, it would float. Except what it would really do is compress. And from the article it looks like it would compress to a size which put it into the 3 - 5 mg/cc range if not higher. That said, in Neal Stephenson's diamond age they used vacuum balloons as a floatation device. something that I hope we can build at some point.
Zenst 14y ago
maybe, though I do wonder how it compares with belly-button fluff in terms of lightness and strength. joke aside how durable is it as by definition it will be extreemly brittle andthe video does seem to indicate that with bits breaking off. If they made round ablls then structurely it would be a little bit more robust. I do wonder what use it could actualy be though. Not very strong, ok it's light but it's not much stronger than air going by that video. I do wonder if you could make a static drawn bellows with this to move air, but thats me being geek. Anybody know what uses this could have beyond coffins for ants sent via beemail! Anybody know a use?
- Ralith 14y ago
  > by definition it will be extreemly brittle By what definition? Because according to Wikipedia, it's just the opposite: https://en.wikipedia.org/wiki/Aerographite#Structure_and_properties https://en.wikipedia.org/wiki/Aerographite#Structure_and_pro...
  - Zenst 14y ago
    Definition I was using was that is was a very the structure has alot of air gaps and that the video shows bits breaking of just from a little bounce. That said brittle is not realy scientific so I'll bow to that and kudos for the wiki link, covers potentual usage as well - thank you.
    - Ralith 14y ago
      That's an observation.

beambot 14y ago

LoL. I had the exact same thought [1], but you managed to finish your comment while I was still away reading about aerogel. ;-) Incidentally, there was a "carbon nanotube aerogel" that (AFAIK) has the exact same composition as this one and is listed at 1.5 mg/cc [2]. Weighing in a vacuum would seem a bit sensationalistic IMO. [1] http://news.ycombinator.com/item?id=4261353 http://news.ycombinator.com/item?id=4261353 [2] http://www.sciencemag.org/content/323/5921/1575.full http://www.sciencemag.org/content/323/5921/1575.full

will_work4tears 14y ago

"So why doesn't this thing just fly away, if its density is 0.2 mg/cc ?" Static friction? It probably would float for some time in air if it wasn't touching something and there is no breeze.

stephengillie 14y ago
In the video (from the article), they wafted up and down between the static-magnetic pull of a wand and the pull of gravity. But they don't stay in the air for long.
ars 14y ago
> Static friction? It probably would float for some time in air if it wasn't touching something and there is no breeze. No. The atoms of carbon are still heavier than air, and no type of structure can alter that. However it can be blown by a breeze and stay up that way - same way a cloud, which is heavier than air, stays up due to wind.
- dasil003 14y ago
  Uh, I'm pretty sure clouds don't float because of wind.