While there are so many fantasies in science fiction, what really gets my goat is travelling backwards into history. While what Einstein probably said is that  astronauts traveling at speeds comparable to light are likely to come back to earth younger than people staying on earth, it doesn't mean that they would get back into history. A moment passed is gone forever.

Film makers and some writers make the mistake of passing off their imagination as credibly scientific which is not correct in my opinion.

Any Comments?

I understood that if it were feasible to travel faster than light (and very recent research suggests that the speed of light is not the ultimate speed), then you would be able to overtake images of the past and see what really went on. This means you could see your great-grandfather, but as he is merely an image you would be unable to kill him, as you can't attack an image. However, if you retrace your steps, and follow the image back to its source quicker than the image is coming "forward" to meet you, does this mean you can then step into the original place where the image emanated from, and interfere in the actual event from which it emanated?

mr_inconsistent wrote:

Film makers and some writers make the mistake of passing off their imagination as credibly scientific which is not correct in my opinion.

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the physicist Ronald Mallett is doing serious research on time travel. so even if you think something is "not correct in your opinion" doesn't necessarily make it so.

Well if you reach the speed of light, you will become energy, and therefore cease to exist...

I agree that sci-fi seems to be drifting away from hard science.  It frustrates me to see especially when related to more recent scientific discoveries, like genetics where they get it completly wrong.  Sorry I can't think of any examples off hand.  Personally I feel sci-fi is a lot harder hitting when it is solidly grounded in reality.

 But then again sci-fi is fiction and futuristic technology is a convenient Deus Ex Machina.

  

Were it possible to travel faster than the speed of light, one would not travel back in time. Instead, time, mass and length would all take on imaginary values, as the value inside the square roots of Einstein's special relativity equations would be negative. I am not so sure what would happen under general relativity, but I am sure that the result would be approximately the same. So, one would not so much travel back in time as perpendicular to it. Whatever that means.

Time travel is excellent in fiction, though. It was shown that a universe rotating at a sufficient rate would permit time travel, however our universe is not rotating.

At the speed of light, mass is infinite. It would thus take an infinite amount of energy to reach the speed of light. While the universe has a very very large amount of energy, it is a finite amount.