OT: Faster than the speed of light?
So I found this question and it really interested me especially after watching Interstellar. Can someone answer this for me? I'd like to build a time machine by going faster than the speed of light.
If I built a railroad track that circled the earth in a straight line, then put a train on that track so long that the first car could connect to the last car (making a full circle around the world). This train can go 100 mph. This train also has a set of tracks on top of it with another train (that circles the world) riding on them, this other train can go 100 mph, so relative to the ground it is going 200mph. This 2nd train also has a set of tracks on top of it with another train on them that can go 100mph, and so on and so on...
when we get thousands of trains out one of the trains eventually reaches the speed of light and it can no longer go faster, but the train that is on top of that one would just be standing still? It would only have to be able to move itself at 1mph to be going faster than the speed of light. Each train relative the the one below it only needs to move incrementally faster, what happens to train above the one that reaches the universal speed limit?
DISCUSS & HARBAUGH
EDIT: Let's assume the trains are powered by Dilithium extracted from Denard. Sorry Denard.
Yeah, like everyone said, as an object approaches the speed of light, it takes more and more energy to increase its speed even a little bit, so much so that it would take an infinite amount of energy to ever increase its speed to light speed (assuming an object with mass). Also, as a couple of people said, relative motion, that is, adding velocitiies, doesn't work like most people think it does. The effects are most noticeable at high speeds, but the bottom line is, you can't just keep adding and adding velocities linearly.
As for warp drives like the Alcubierre drive, I gotta say no. Those things allow for backwards time travel (or at least the equations they require allow for backwards time travel) and as Arthur C Clarke said, the best evidence against (backward) time travel is a distinct lack of tourists from the future.
And wormholes, I mean, you're talking truly cosmic amounts of energy to manipulate that, even if the general relativity solutions that allow them turn out to be valid. And after all that, it's not at all clear that they would do what you want them to do (allow nice safe FTL travel to DS9 or something).
If you want to read about serious attempts at backward time travel, take a look at Cramer's work out at U Washington.
Here's a joke:
Bartender says, "What'll you have?"
A tachyon goes into a bar.
There was a recent article that said that NASA may have discovered particles travelling faster than the speed of light and essentially proposed a sort of warp bubble for interstellar travel. Its pretty fascinating, but all conjecture at this point.
I havent read every response but assume others have made these points. Nonetheless me being me I am compelled to put in my two cents as I see it.
Answer is NO. There are two reasons.
First, this is a theoretical question that the laws of the universe conspire to make impossible. The closer something gets to the speed of light, the heavier it will get. Infinitely close to the speed of light, it will have infinite weight. To go after, you have to accelerate an object; to accelerate it, you need to apply a force (F=ma); to get a force, you apply energy over time (work). Infinitely heavy mass requires infinite force, requiring infinite energy, which does not exist. So it is simply not possible to accelerate an object past the speed of light.
The "fastest" train, at the "top" of the stack, would appear to get infinitely heavy as it gets closer to the speed of light. No amount of energy in the universe could cause the trains beneath it to accelerate it over (or even to reach) the speed of light.
Second, this is also a trick question. When you say "going 100 mph," you have to ask -- as measured by whom? An observer on the side of the tracks will measure a different speed than the conductor of the train. Time slows down for the moving trains; distances shorten. 100 mph to the conductor might be a million miles an hour to the observer.
What would the train look like from behind, as no light could ever travel fast enough to reflect?
Could you ever see something moving faster than light? - No, because nothing does move faster than the speed of light. At least, nothing with mass, and nothing that started with a speed less than light. There are theoretical - _extremely_ theoretical, as in, there's no real evidence they exist - particles called tachyons that always move faster than light. And you couldn't see them coming. But there really is no evidence for them, and plenty of evidence against the things that their existence would imply, so... there's very, very little serious work done concerning tachyons.
What would a train moving at 99.99999% the speed of light look like from behind? - It's complicated. First, you could definitely see it, from either in front or behind, as light still reflects off it at c (3*10^8 m/s in vacuum). Now, if you measured it, you'd find that the train's length in the direction of travel would be contracted while its other dimensions would be unchanged. However, just looking at it, you have to take into account the transit times of light, which get complicated. Basically, it would look distorted - rotated in some sense - but not simply contracted as an instantaneous measurement would yield.
Thanks for the info. I had presupposed a scenario where someone had gotten something with that mass going at a speed faster than light, which I know they can't. In those, hypothetical conditions, I wondered what you would see from behind the object, as light could never actually reach the surface of the object to reflect back (at least at a favorable angle). I assumed it would be a point of perfect black surrounded by heat radiation.