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Author Topic: Does a vacuum float?  (Read 1753 times)

Pierre

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Does a vacuum float?
« on: 30/05/2008 09:15:59 »
Pierre asked the Naked Scientists:

Hi,

I write from Montreal, Canada.
I love your show, it's great to be able to use my commuting time to work to learn new things.

I was wondering, if to make something rise in the air it needs to be of lesser density then air. Would it be possible to build a super light, super strong container, create a vacuum inside and make it rise in the air?
Or would it simply be crushed by the atmospheric pressure.

Thanks

Pierre

What do you think?


 

Offline Soul Surfer

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Does a vacuum float?
« Reply #1 on: 30/05/2008 10:11:29 »
No no materials are strong enough and light enough to contain a vacuum in atmospheric pressure and remain bouyant hydrogen or helium must be used to balance the pressure.  Hydrogen is a very cheap light gas to inflate ballons with but it has the disadvantage of being highly inflammable.
 

lyner

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Does a vacuum float?
« Reply #2 on: 30/05/2008 11:36:14 »
You can still measure the decrease in weight when you take the air out of a relatively light container; for instance, a 1litre lab flask.
 

Offline graham.d

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Does a vacuum float?
« Reply #3 on: 30/05/2008 13:11:11 »
I believe the weight of air in a Boeing 747-400 is about 1 ton. Dropping cabin pressure during a flight makes the plane a bit lighter. I think the cabin pressure during a flight is set at about 8000 feet which will reduce the weight of air by nearly 10% (I think). I have not done the calculations - this is from memory only.
 

Offline LeeE

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Does a vacuum float?
« Reply #4 on: 30/05/2008 14:13:15 »
IIRC, the very first proposal for a lighter than air (LTA) craft was to utilise an evacuated vessel (I think it may have been a copper sphere).  I can't remember exactly who came up with the idea though - Wikipedia credits it to Franceso de Lana, an Italian monk, in 1670 but I've got a feeling it may go back a lot further than that.  Certainly, Archimedes (c. 287 BC c. 212 BC) established the theory of buoyancy and I'd be a bit surprised if the idea hadn't occurred to him.

 

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Does a vacuum float?
« Reply #4 on: 30/05/2008 14:13:15 »

 

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