I don’t see how negative mass would allow ponderous bodies to move at the speed of light. The +mass and the -mass pair would just approach the speed of light, just like any accelerating body.
wastelands,
Things travelling at SOL don’t turn to mass, As you approach the speed of light your mass increases and the increase (at any particular speed) is proportional to your mass. Photons have no mass. Things that have mass cannot reach SOL. Things with no mass must travel SOL (in a vacuum)
Another thought experiment is if you light a lamp in the center of a room moving relative to me. You would observe the light hitting the front and rear walls at the same time. I, however, would observe the light hitting the rear wall sooner, because the light would not have as far to travel.
Virtually yours,
DrMatrix
If I’ve told you once, I’ve told you 0.99999999… times.
Photons have energy. Energy is mass. They don’t rest mass.
You can’t, even in theory, especially in theory (i.e. the theory of special relativity), have an absolute velocity, unless you have zero rest mass and are thus travelling at the speed of light, in which case your velocity is absolute in all reference frames.
According to General Relativity, something does happen to photons in a gravitational field: They change their direction of motion. If they are travelling perpendicular to the field (away from a center of mass), they lose energy and their wavelength increases.
Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum immane mittam.
I found this in the archives:
[url=http://boards.straightdope.com/ubb/Archives/Archive-000004/HTML/20000403-3-001932.html]Explain the Theory Of Relativity
Virtually yours,
DrMatrix
If I’ve told you once, I’ve told you 0.99999999… times.
Well, in the simple two-body case, where one has negative mass, the fact that the total mass is zero lets us get around the ass dilation problem, but there’s still admittedly a problem with time dilation: from the point of view of the rest of the Universe, it’d take forever to reach c. There are other methods proposed which use negative mass in more creative ways, though. For instance, it’s negative mass which would allow for stable wormholes or warp bubbles. Still doesn’t change the fact that we have too much of the stuff, i.e., none.
“There are only two things that are infinite: The Universe, and human stupidity-- and I’m not sure about the Universe”
–A. Einstein
Well, it isn’t as if Einstein pulled Relativity out of his rear end. It was based on observations of the universe. A theory is only useful if in addition to describing known phenomena, it also predicts phenomena. General Relativity predicted visual displacement of stars around the sun, because of its gravitational field. The sun was observed during a total eclipse, and voila! the stars were in fact shifted from their normal positions.
Now, the only way to make predictions about circumstances we haven’t tested, we must extrapolate from existing theories, or come up with new ones that are consistent with known phenomena, and that are testable. Without this framework, you’re just making stuff up at random.
Again, the problem is that nothing with rest mass can travel at the speed of light. Period. And BTW, light does have energy, and does knock things around, but they’re generally on the order of electrons, etc. Ever gotten warm on a sunny day? That’s (mostly) the light from the sun (probably most of it in the infrared spectrum) warming you up.