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Can Graphene/Nanotubes Change Mass? (Massless Propulsion)

Posted by: sanman - Thu Oct 21, 2010 2:50 pm
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Can Graphene/Nanotubes Change Mass? (Massless Propulsion) 
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Space Walker
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Post Can Graphene/Nanotubes Change Mass? (Massless Propulsion)   Posted on: Thu Oct 21, 2010 2:50 pm
A new conjecture postulates that it may be possible to "create" mass through relativistic effects on leptons inside of graphene, when it is rolled up into a nanotube:

http://www.technologyreview.com/blog/arxiv/25914/?p1=A4

Gee, does that imply that it could be possible to manipulate or modulate the mass of a system comprising graphene/nanotubes?
Can anyone think of a suitable mechanism to accomplish this?

Leaving aside the details of how to accomplish this for a moment, what are the further implications and applications of a system whose mass could be modulated through internal relativistic effects?
Could it be possible to achieve propellantless propulsion? Perhaps even artificial gravity?


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Post Re: Can Graphene/Nanotubes Change Mass? (Massless Propulsion)   Posted on: Thu Oct 21, 2010 4:33 pm
I don't think this has much of an impact on anything practical. The way I read that article, electrons and holes in graphene behave just like electrons in a vacuum, which is to say, as if they have no mass. If you roll up the sheet, they will behave normally again. For sure that will allow some interesting experiments, but given that the vast majority of the mass in the structure is in protons and neutrons, it will only make a tiny difference when you put your graphene on a scale (if any at all, I don't know enough about this to say).

Propellantless propulsion may be possible if you could indeed have the mass change. You just mount your mass-changing stuff on a cylinder, make the mass big, push it towards the back of your ship, then make the mass small again and pull it back towards the front. That will give you a net forward momentum. I seem to recall reading about this in the context of the quantum Casimir effect long ago, but I may just be mixing things up. That wasn't about graphene, that I do know.

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Post Re: Can Graphene/Nanotubes Change Mass? (Massless Propulsion)   Posted on: Thu Oct 21, 2010 6:18 pm
Certainly electrons traveling in a vacuum have mass. If you fire a bunch of electrons in a vacuum at a target mass, then that mass will move due to the electrons colliding with it. Electrons are not massless in a vacuum.

However, it does seem to really just be the composite quasi-particles formed by these leptons which behave masslessly. So it's possible that it's totally off the mark to say that the relativistic analogy would actually result in an increase in mass.


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Post Re: Can Graphene/Nanotubes Change Mass? (Massless Propulsion)   Posted on: Fri Oct 22, 2010 9:03 pm
Hmm, good point on electrons not being massless in a vacuum. I don't understand the Wikipedia article on the Dirac equation, but it does seem to contain one mass term, as does the Schrödinger equation. So either we or the author of that article must be missing something.

Anyway, I think the key here is "is mathematically equivalent to the behaviour of...". A hot-air balloon that does not change altitude despite a gravitational force pulling it downwards may be said to exhibit behaviour that is mathematically equivalent to that of a massless object as well. After all, according to the law of universal gravitation, F = G * m_earth * m_balloon / r^2, Newton says F = m_balloon * a. We can combine that to m_balloon * a = m_balloon * G * m_earth / r^2, G * m_earth / r^2 is strictly positive, a is zero since the balloon doesn't move, so m_balloon must be zero.

Of course, the balloon isn't really massless, it's just that the gravitational pull is compensated for by bouyancy. "Is massless" is not the same as "behaves like a massless object".

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