- #1
Mark_Laverty
- 12
- 0
Hi,
I would be really grateful if someone could help me with two questions I have, both have puzzled me on and off for years. I have read what I can regarding these points, but a lot of it I don't understand (the maths specifically). I would love it is someone who understands this more than me could take a few minutes to help me understand what I am missing/misinterpreting.
The first question can best be described with a thought experiment...
Imagine you have two planets 1 light year apart. Let's call them planet A and planet B. Exactly half way between them is a small star and on both planets there is a person observing that star.
At the moment both observers see a huge solar flare erupt from the star they fire a huge flare up into low orbit and a spaceship takes off from Planet A traveling to planet B at exactly the speed of light.
The observers on each planet then turn their telescopes towards each other and zoom in.
Over the next year the observers on each planet will watch each other with time passing normally. To start with they see each others planet as it was a year before and after one year of observing they will each see the other turn their telescope towards each other and the flare go up into low orbit.
That bit I get :-) What I don't get is what happens from the spaceships point of view and why people say that that if it travels faster than light it can 'travel back in time' effectively.
Whilst it is traveling at the speed of light, the pilot looks out the front window. I believe he would see events on the planet he was heading too happening twice as fast as they were for the people on that planet. Effectively when he launched he was 1 year behind events on planet B, and by traveling at the speed of light he is effectively just catching up.
He looks out the back and he see's events on the planet he has left as completely frozen solid. They are frozen at the moment just after he hit the speed of light departing from Planet A
E.g. nothing is actually happening. Basically he started at planet A one year ahead of what people on planet B would see when looking at Planet A. and when he arrives at Planet B and stops then looks at planet A out the back window he see's events resume but as there were when he left 1 year before. This is in agreement with what people on Planet B see.
If he'd traveled at twice the speed of light events would have been going past 4 times faster than normal in front of him, and actually going backwards when he looked at the back window at planet A.
When he arrives at Planet B he looks back at Planet A and sees things as they were 6 months before he leaves, in complete agreement with what the people on Planet B would see.
Even if he turned round and flew back to Planet A faster than the speed of light he still couldn't arrives back before he left because as he was flying towards planet A he'd see events on planet A going past faster than normal, meaning he'd still arrive after he left.
Even if he traveled at 100, 1,000 or 1,000,000 time the speed of light he still couldn't travel in time.
Its all just an optical effect created by the speed of light and time appearing to distort.
Basically, even if you could beat light, you still couldn't beat time.
So, that is how I visualise things. I just can't see how traveling faster than light could allow time travel? What am I missing?
Thank you!
PS. I'll post the second question once I've found an answer for this one, my head hurts now! :-)
I would be really grateful if someone could help me with two questions I have, both have puzzled me on and off for years. I have read what I can regarding these points, but a lot of it I don't understand (the maths specifically). I would love it is someone who understands this more than me could take a few minutes to help me understand what I am missing/misinterpreting.
The first question can best be described with a thought experiment...
Imagine you have two planets 1 light year apart. Let's call them planet A and planet B. Exactly half way between them is a small star and on both planets there is a person observing that star.
At the moment both observers see a huge solar flare erupt from the star they fire a huge flare up into low orbit and a spaceship takes off from Planet A traveling to planet B at exactly the speed of light.
The observers on each planet then turn their telescopes towards each other and zoom in.
Over the next year the observers on each planet will watch each other with time passing normally. To start with they see each others planet as it was a year before and after one year of observing they will each see the other turn their telescope towards each other and the flare go up into low orbit.
That bit I get :-) What I don't get is what happens from the spaceships point of view and why people say that that if it travels faster than light it can 'travel back in time' effectively.
Whilst it is traveling at the speed of light, the pilot looks out the front window. I believe he would see events on the planet he was heading too happening twice as fast as they were for the people on that planet. Effectively when he launched he was 1 year behind events on planet B, and by traveling at the speed of light he is effectively just catching up.
He looks out the back and he see's events on the planet he has left as completely frozen solid. They are frozen at the moment just after he hit the speed of light departing from Planet A
E.g. nothing is actually happening. Basically he started at planet A one year ahead of what people on planet B would see when looking at Planet A. and when he arrives at Planet B and stops then looks at planet A out the back window he see's events resume but as there were when he left 1 year before. This is in agreement with what people on Planet B see.
If he'd traveled at twice the speed of light events would have been going past 4 times faster than normal in front of him, and actually going backwards when he looked at the back window at planet A.
When he arrives at Planet B he looks back at Planet A and sees things as they were 6 months before he leaves, in complete agreement with what the people on Planet B would see.
Even if he turned round and flew back to Planet A faster than the speed of light he still couldn't arrives back before he left because as he was flying towards planet A he'd see events on planet A going past faster than normal, meaning he'd still arrive after he left.
Even if he traveled at 100, 1,000 or 1,000,000 time the speed of light he still couldn't travel in time.
Its all just an optical effect created by the speed of light and time appearing to distort.
Basically, even if you could beat light, you still couldn't beat time.
So, that is how I visualise things. I just can't see how traveling faster than light could allow time travel? What am I missing?
Thank you!
PS. I'll post the second question once I've found an answer for this one, my head hurts now! :-)