I'm not sure how theoretically possible this is but my question is...

If we could somehow make a perfect bubble of photons (a massless bubble) and put a spaceship inside it, could it therefore effectively become massless as the perfectly sealed bubble around it has no mass adn therefore travel at lightspeed?

Sorry if this is just nonsense.

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    $\begingroup$ As my friend Zach once remarked when confronted with a similar question, "I've got a mushroom pound of photons for your forehead." I don't know what he meant, but it sure was snappy. Joking aside, I think the answer to this question is 'no'. The mass of an object is not generally related to the presence or absence of photons nearby. $\endgroup$ – Andrew Mar 10 '11 at 16:32

Let me enumerate several reasons why it's indeed nonsense:

  1. Photons are called massless because their rest mass is zero; however, their total mass that is subject to gravity etc. is given by their energy, $E=mc^2=hf$, and it is nonzero

  2. Photons can't be kept in a shell because they need to move by the speed of light; the closest thing you can get is the "photon orbit" of a black hole - at distance $R=3GM/c^2$ from a neutral black hole center, for example - where photons may move for a long time but this orbit is unstable, so the photons eventually either fall to the black hole or escape from it

  3. Even if you ignored the problems above, the photons would have no impact on the spaceship inside: analogously, toilet paper is also light but a dumbbell doesn't become light just because you pack it in toilet paper. I have already written enough so if you need to explain why the previous sentence is true, please ask another question and someone else may wrestle with it.

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    $\begingroup$ "but a dumbbell doesn't become light just because you pack it in toilet paper" lol, thank you! I think I understand now! Photons really do cause me problems getting my head around. But this has helped a lot. $\endgroup$ – takkischitt Mar 10 '11 at 16:40
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    $\begingroup$ It was a pleasure. Photons are cool but they're just pieces of light. $\endgroup$ – Luboš Motl Mar 10 '11 at 17:10
  • $\begingroup$ Funny for you to say that "Photons (...) [a]re just pieces of light". As Einstein said in a letter to Besso: "50 years of consciously pondering have not gotten me closer to the answer of the question 'What are quanta of light'. Today every rascal thinks he knows but he is wrong" (that's a simple translation from the originally german letter) $\endgroup$ – BandGap Mar 11 '11 at 10:55

This is just nonsense.

The only remotely possible idea that comes to mind in this context is by using the photon's impulse to maintain some sort of balanced spaceship but there is no way to create a bubble of photons. They cannot be confined without some material border (aka mirror)and you would have to carry that weight with you.

Edit: Ok, not only material borders but also bending of space would allow for photon confinement. But gravitational effects have the side effect that you need some major amount of mass to do that (black holes, galaxy clusters, ...). Unfortunately to accelerate such a body you need a lot of force of some kind since F=ma and thus a=F/m. (a being acceleration, m the mass and F the force)

  • $\begingroup$ Thanks for your answer. I'm not a physicist or in any way schooled in this sort of subject so this is more a product of my basic knowledge and imagination, so again, this may appear as nonsense... but gravity bends light (photons) as in the case with gravitational lensing, so would it be theoretically possible to hold the photons in a bubble through massive gravitational fields? $\endgroup$ – takkischitt Mar 10 '11 at 16:30
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    $\begingroup$ @takkischitt Read Lubos' answer again. You would need a black hole to bend the light a lot , but it would not form a bubble. $\endgroup$ – anna v Mar 10 '11 at 20:51

The real answer here is 'why not?', of course!

You all assume that you need billions of static photons to form a bubble.

Just one, (obviously, traveling at the speed of light), and forced to follow an arc which steps sideways by the width of a photon on completion of one orbit, would be a complete bubble to us.

What forces are generated inside this one photon bubble? This is the question to ask yourselves.

  • $\begingroup$ Jeez! I never looked at it from that point of view! $\endgroup$ – Terry the Timelord Mar 21 '13 at 19:44
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    $\begingroup$ Bit of a weird comment on your own post ;) $\endgroup$ – Bernhard Mar 21 '13 at 20:08
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    $\begingroup$ That's an answer fitting to the level of the question. Science fiction for non-physicians. ;) $\endgroup$ – Stefan Bischof Mar 21 '13 at 20:15

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