I just started reading Stephen Hawking's A Brief History of Time and just wondering about something.?

Question

It states in the book that when the sun collapses, it won't affect us until 8 minutes later due to the time it takes light to travel to Earth.
If this is true, we can build a machine that can cause us to travel faster than the speed of light(classified as "not allowed" in the book) and escape time, right? Then, somehow we might be able to travel to the past, right? If you have no idea what I'm talking about then I'm sorry for wasting your time.=P

Answer 1

Well, not really. If any matter starts travelling at close to the speed of light, the mass becomes infinetely inmense, therefore impediing to travel at that speed. The math simply won't allow anything to travel at that speed. Anyway, if you look at the sky, what you are actually seeing is not in "real" time, but you are looking at the things that were there millions of years ago. By peeking into a telescope, you are looking at the past.
Hope it makes sense...

Answer 2

Ya thats right. It takes 8 minutes for light to reach the earth. If the Sun exploded or collapsed we would not know about it for 8 minutes. Light travels at 186 thousand miles per second. Furthermore if you look at a star that is 26 lightyears away, you arent really looking at the star how it is. You are actually looking at a 26 year old image of the star which has an image that took 26 year to reach our vision.. Its possible that the star might have been destroyed 20 years ago, but we would not know it for another 6 years! By the way, I dont think you can travel back in time because of the possible paradox that could happen. What would happen if I traveled back in time 10 years and killed my younger self? That could not be possible. Because then my younger self would not have aged 10 years and have had the opportunity to do that in the first place. Time travel just cant exist.

Answer 3

First, we will feel the gravitational effects of the sun's collapse, since that is a space-time structural phenomenon. The light and other energy phenomena will reach earth at the speed of light, so by the time we "see" the collapse, it will be way too late to try to escape its effects.

Second, if you are assuming, despite Hawking's saying you can't make a FTL craft to get out of the solar system before the collapse, that you can, you are both confused and resorting to fantasy.

Third, going FTL does not mean time travel. Where's the connection? You would be going faster than light, so you would be going into the "future" of the light that will reach you, but that has nothing to do with going into the past. Hawking has come around to agreeing that the arrow of time points only in one direction.

Answer 4

Though the affects of the sun's collapse won't be felt until 8 minutes after the fact the only experience we will know is our own physical reality of experiencing it, be it 8 minutes later than the actual occurence. That kind of information is important to physical reality but not to the physical experience of reality.
I mean, Does it really matter if we get a play by play of the destruction of our universe as we know it on CNN for 8 minutes before we all explode or freeze?
To the person who has time-travelled back from that moment to this one, "Hi".

Answer 5

If people were able to travel back in time...they would have already done so, eh?

In any event...since you do not want to play "what ifs" using the laws of physics, we could merely step off the planet into a new universe where we would begin right where we left off. That would be a better solution...and take much less than 8 minutes.

You can do so much when you ignore physics.

Answer 6

I don't see how light taking 8 minutes to reach earth allows you to build a time machine? in the same way, light from the stars you see at night has been traveling for hundred and sometimes hundreds of thousands of years. Soo. again how are we supposed to escape time?

I am intrigued by your question though. just not sure about where you made this leap of logic. please explain further.

Answer 7

No, we can't build a device that would permit us to travel even near the speed of light. Our physics don't allow for that. The formula is the, Lorentz Transforms. Basicly, it would take all of the combined energy of our universe to acclerate one particle of anything to 95% the velocity of light ,let alone the mass of a human body . Sorry

Answer 8

As you approach the speed of light, a phenomenom sometimes called "dilation of time" occurs and if it would be possible to travel at exactly the speed of light with realtion to any arbitrary reference frame then the effect is that time would come to a stop in relation to that reference frame. In other words, if you could escape the earth at the speed of light in relation to the earth, then it would be like your onboard clock stopped also in relation to any clock left on earth. This would be the equivalent of travelling to the future and not to the past since the clock left on earth would be ticking while yours is "stopped". For you the clock would tick as usual but not in relation to that one left bak on earth. If you do not understand relativity then sorry for wasting your time.

Answer 9

No, because at the speed of light, time slows down for the occupant of the craft. You don't escape time, as it continues to flow normally for everything else, it just slows you and your perception of time. It has been nearly 20 years since I read the book.

Answer 10

no and really, things must be able to travel faster than the speed of light. We just can't see them. however, we would only be allowed to travel in space, not time, there fore would not be able to go backwards in time.