Re: [Sci.nanotech] Re: Just thinking crazy I guess :)



"Spaceman" <Realspace@xxxxxxxxxxx> writes:
"Perry E. Metzger" <perry@xxxxxxxxxxxx> wrote in message
news:121p985f2au0med@xxxxxxxxxxxxxxxxxxxxx
"Spaceman" <Realspace@xxxxxxxxxxx> writes:
Trapping hydrogen in nanotubes has been proposed as one possible way to
store hydrogen for use as a fuel source, so there is some value in that
concept. I'm not sure what value there is in trapping helium, though.

Thanks for the reply Jim,
Well, depending on how long it would stay trapped, I would gather it
would make the tube slightly "lighter"

How? A buckyball or sealed nanotube with nothing in side is
necessarily less massive than an identical one with something
inside.

I am comparing it to nitrogen or oxygen or whatever filled it
if not built in a close to perfect vacuum.
(I suppose it would have to be built in such vacuum anyways?)

Might I suggest that you spend the five minutes it would take to learn
the answers to your questions? This is the age of the internet. You
don't even need to go to a library first.

As for this notion of "vacuum" you have in this context, I suggest you
think for a moment about the mean free path of gas molecules at 300K,
and compare that to the size of a buckytube.

and in turn may be
able to make tiny machines made lighter so less
energy would be needed to run them in the long run depending on if
they actually would make a difference to the weight of the nanotubes
themselves.

Er, huh?

Just what I said.
Here is the shorter version,
Less mass needs less energy to move it.

An object with something inside it has more mass, not less, than the
object without something inside. Mass is not reduced when something is
bouyant. I suggest going back to introductory physics class.

(I also think about vacuum "filled" nanotubes).
And I was also wondering about "floating in air of course too."
(the floating is the crazy part I am think I guess.)
:)

Putting something inside a nanotube makes it heavier than having
nothing inside. If you want objects that are buoyant in air, putting
helium inside doesn't magically make them "lighter". If you don't
understand this, you should work out for yourself why it is that
ships float.

I do know that.
As I stated, I also have thought about the vacuum filled version.
but one difference would be a gas without actual pressure on the
walls inside could actually help with the strength of the structure
where a vacuum would actually create a stress in the structure.

So how would a buckytube crush under 1 atmosphere of pressure? Or even
far, far more? Even without doing a calculation it is pretty obvious
to the casual observer that isn't going to happen. If it isn't obvious
to you, you don't know enough to make informed speculations on this
topic.

I think this is why we don't have balloons that float by using vacuum?
:)

If you can't tell, intuitively, why a macroscopic object like a
balloon wouldn't behave the same way as a nanoscopic object like a
buckytube, you don't know enough to speculate on these sorts of
topics. Here is one hint: think about scaling laws, and how ratios of
surface to volume might change over twenty or more orders of
magnitude. If that takes you more than a second or two, you don't know
enough to be speculating on this topic.

Perry

.

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