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18 Nov 11
1 edit
Well air has a density of about 1.275mg/cm3 whereas this is being reported as having a density of 0.9mg/cm3 presumably due to having vacuums inside it.
Not sure how you make a materiel less dense than a gas without having vacuum spaces inside it, otherwise it gets air inside it which contributes to it's density.
19 Nov 11
Originally posted by googlefudgeIf it really had a 0.9 density it would float but there was no mention of that. It may not be strong enough to have vacuum inside, the 14.7 PSI of air would squash it flat.
Well air has a density of about 1.275mg/cm3 whereas this is being reported as having a density of 0.9mg/cm3 presumably due to having vacuums inside it.
Not sure how you make a materiel less dense than a gas without having vacuum spaces inside it, otherwise it gets air inside it which contributes to it's density.
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19 Nov 11
Originally posted by sonhouseIt's possible (maybe, the 'articles' I have seen on it are very non specific.) that the metal tubes
If it really had a 0.9 density it would float but there was no mention of that. It may not be strong enough to have vacuum inside, the 14.7 PSI of air would squash it flat.
it's made from have vacuum inside, they are nano-scale structures and very strong.
Or it might be that the stated weight doesn't include the weight of air inside the structure.
28 Nov 11
Originally posted by googlefudgeNano is not small enough to exclude air. Picosized devices are.
It's possible (maybe, the 'articles' I have seen on it are very non specific.) that the metal tubes
it's made from have vacuum inside, they are nano-scale structures and very strong.
Or it might be that the stated weight doesn't include the weight of air inside the structure.
02 Dec 11
They aren't reporting density of total material including the air it contains, they are reporting density of the material itself excluding air. The article is actually pretty explicit that the material contains 99.99% air (not vacuum).
Compare to the density of styrofoam, which at .089 mg/cc, also doesn't measure the air inside. We all know styrofoam doesn't float 🙂
02 Dec 11
1 edit
Oops, figure on styrofoam was wrong it's more like 9 mg/cc, but anyway... you get my point.
Another way to look at it is that the figure presented is the density of the material in a vacuum. Reporting anything else wouldn't really make sense -- they'd have to report the density of the measured air, since it would dominate the measurement.
05 Dec 11
Originally posted by WoodPushWould air contribute to the weight if the pores were not sealed? I don't think it would in that case. I think it would weigh the same in a vacuum.
Oops, figure on styrofoam was wrong it's more like 9 mg/cc, but anyway... you get my point.
Another way to look at it is that the figure presented is the density of the material in a vacuum. Reporting anything else wouldn't really make sense -- they'd have to report the density of the measured air, since it would dominate the measurement.
05 Dec 11
3 edits
Originally posted by sonhouseYou might be confusing weight and density, which aren't the same (the figures in the article and most of this thread were density).
Would air contribute to the weight if the pores were not sealed? I don't think it would in that case. I think it would weigh the same in a vacuum.
But to answer your question:
Air doesn't contribute to weight measured by a scale, in general, because the scale is already calibrated with air pressure considered. So unless you change the density of the air (and with open pores, you aren't), there won't be a change in weight measured.
But if you move the scale into a vacuum, it would have to be recalibrated, because it would no longer have atmospheric pressure applied.
I suppose it might be difficult to say how much the scale would register the difference because it depends on the shape of the scale and how the air pressure was originally distributed on the scale's parts.
So, to sum up: no the material itself would never weigh different in a vacuum - weight, or force of gravity, isn't affected by air pressure. But the scale might have a different reading due to the change in air pressure.
05 Dec 11
Originally posted by WoodPushThat is clearly incorrect. A simple example of a helium filled balloon which would have a weight in a vacuum, but has negative weight in air.
So, to sum up: no the material itself would never weigh different in a vacuum - weight, or force of gravity, isn't affected by air pressure. But the scale might have a different reading due to the change in air pressure.
05 Dec 11
Originally posted by twhiteheadNo, it's not incorrect. Weight is defined as the force of an object due to gravity.
That is clearly incorrect. A simple example of a helium filled balloon which would have a weight in a vacuum, but has negative weight in air.
Gravity doesn't push helium balloons away from the earth.
Your experiment to measure the weight of the helium balloon was done incorrectly.
05 Dec 11
Originally posted by WoodPushI see. But that means that a scale does not measure weight.
No, it's not incorrect. Weight is defined as the force of an object due to gravity.
Gravity doesn't push helium balloons away from the earth.
Your experiment to measure the weight of the helium balloon was done incorrectly.