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Well, since this was posted in Science Memes, I'll be so pedantic that science does not support the idea of travelling back in time.
It does support travelling forwards in time, at various speeds, but you'll constantly be aware of where you are (even if one method involves travelling really fast and therefore may still leave you in empty space).
I'm traveling forward in time right now.
Big, if true
Me too! What's your destination?
Stable employment hopefully
I'd like to get off at the next stop but thanks to my friend Schrödinger I fear I'm stuck here until the end of the line.
I thought it was possible in relativity if only you could solve that pesky going faster than light problem. Only going to the speed of light is impossible. If you were to start out beyond the speed of light you should be traveling backwards in time. Mathematically that should be possible.
I have heard that notion before, but don't know how the maths is supposed to work.
I can tell you, though, that light would be going faster than light, if it could.
Here's a simple equation you probably know:
F = m * a
(F is force, m is mass, a is acceleration)Well, if you rearrange it, you get this:
a = F / mWe currently believe photons to have no mass.
Insert that into the equation and you get a division by zero, but our closest approximation means acceleration is infinite, as soon as any non-zero force is applied.Infinite acceleration results in immediate infinite velocity. It makes no sense for light to only accelerate until 300,000 km/s and then take its foot off the gas pedal.
This is why it's instead believed that there is a speed limit to causality itself.
The speed of light (as well as of gravitational waves and other massless things) just happens to be the same value, because they're going as fast as is possible.Here's a video about the speed of causality: https://www.pbs.org/video/pbs-space-time-speed-light-not-about-light/
if you believe in the notion that the universe is cyclic then you can mimic time traveling backwards by traveling forwards, past the end of the universe, and stopping at just the right time in the new universe.
e.g., to get to 1700 you’d go (present time) -> (death of the universe) -> (1700 in next universe)
But what if the absence of the atoms of your body affects how the universe collapses and in turn expands?
If you've already done six impossible things today, why not stop for breakfast at Milliways?
then you’re in for a fun surprise
If the universe is cyclic, then the version of you from the previous one is also jumping to a time before when you left. It works if the board gets reset to the exact same position and true randomness doesn't exist. We're talking down to the electron scatter of radioactive decay.
If the universe is cyclic, then that would define it as a closed loop without any energy being removed or added. The very first instance of yourself traveling through time would break the loop by removing themselves from their iteration of the universe and reinsert into a future iteration. During those two points, the universe would now function with a deficit. This deficit could affect how it cycles to subsequent iterations.
What if that discrepancy in energy affects when the universe starts to contract or it's speed to the big crunch/bang and subsequently the time to, and speed of expansion. Maybe it could even prevent the big crunch from reaching critical mass, where it would normally trigger a big bang, and stop the cycle altogether.
I mean, personally, I actually don't believe that the Big Bang created everything out of
thin airvacuum, because much like travelling backwards in time, that would break causality.It makes much more sense for everything to just have always existed and the Big Bang is merely a very visible event + expansion afterwards.
I'm open to the notion that expansion and contraction happen in some sort of cycle, because well, many things do.But for it to be cyclical to the point where it repeats precisely the same? Why?
Can't we just let the universe flobber on its merry way without assigning some higher meaning to everything it does?Futurama has an episode like that. It was a pretty good one.