Recent content by Maartenc

Ah, thanks, and apologies for my ignorance. I guess what I wanted to know was can you heat up a gas through an absorption line?

Hi, I have been wondering if greenhouse gases always need to be polar molecules. Can a gas also absorb energy, and heat up, without being polar?

Thank you very much, all of you, for taking the time to help me understand these issues. It is a fascinating subject, but it can be difficult to see things in the right context. Your comments have helped a lot.

Sorry, I should have said 'if the effects of acceleration propagate at a finite speed'

Sorry, the article in the link looks a bit too complicated for me. Perhaps I should give it a try anyway. Thanks.

Thanks for the answer, and those links are excellent.

I'm reading up on relativity, but it confuses me. If I observe a virtual particle pop up in empty space, what sort of average speed would that particle have? It cannot depend on my reference frame, because the particle doesn't know about that. Or perhaps it does, as my observation ties it into...

Yep, that's clear. But the same is true for gravity. If the same rod is exposed to a sudden large increase in the gravitational field the compression caused by that would also have a limited speed. But the gravitational field will propagate at the speed of light. My confusion is a bit more...

OK, thanks for the answers. I do understand that Lorentz contraction is caused by velocity, but velocity is caused by acceleration, and acceleration would contract an object if it propagated at a finite speed. I guess I'm just surprised that a simple explanation like that doesn't seem to hold...

Hi, I have been asking friends with physics degrees this question, but they cannot answer it, or give conflicting answers. When two reference systems move relative to each other, space becomes shorter in them, as seen from the other system. Gravity and acceleration are indistinguishable. The...