Thanks, JesseM. I appreciate your comments to my posts. Is my reasoning correct that on the return trip from a space journey time relative to Earth time speeds up?
Like I said earlier, I am not a physicist. What is gamma? The formula I mention is taken from Einstein's book "Relativity", which is high school level reading.
The Twin Paradox
In an earlier submission I stated that concerning the twin paradox, when a spaceship travels away from the Earth at a velocity near the speed of light time in the spaceship slows down relative to the time on earth, but on the return trip time in the spaceship speeds up...
If there is no "now", only 4D spacetime, then would the future not be fixed as well as the past? This would be a predetermined universe just playing out as a movie.
I am not acquainted with relativity mathematically, but in my way of thinking the relativity of simultaneity does not rule out...
Two assumptions I make are that time is just the rate at which things change, and that to visit the past the past or future they must both exist. The definition of time travel as popularly conceived is that a person visits either an earlier or later "now". If my assumptions are correct, either...
Correct, Peter. I was looking at the situation of a person measuring the speed of light while traveling back to earth. His velocity would add to the speed of light if it were not for relativity. Therefore to keep c constant time would have to go faster for the traveler relative to Earth time...
My assumption is that to visit the past, the past must still exist. If the object's "worldline" curves back on itself to revisit a region of spacetime it already crossed through before, would that space time not have the identical state and energy as when first crossed? If so, wouldn't the...
You are neglecting a term in the numerator. Einstein gives the time dilation equation as:
t' = __t-vx/c^2____
sqrt(1-v^2/c^2)
where t' is the traveler's time,t is Earth time, and x is the coorinate along which both the light beam and the spaceship is traveling. The x is...
Whose Future?
Question is whose future would you return to? Your life would have been continuous, so there is no "break" in time which there would be if you had actual time travel.
Here is a question I have concerning the twin paradox, where one twin goes on a space ride near the speed...
Would every change need to be reversed?
I haven't been on the forum until now, but your question of why reversal of time requires every change to be reversed requires an answer.
If you assume that only certain changes would have to be reversed, who would decide which ones to be reversed...
Relativistic velocities lead to mass increases. The mass of particles (atoms, molecules, etc.) does affect the rate of diffusion, chemical reactions, and many other processes. Since the photon does not have mass it is not effected by relativistic mass. Therefore I would expect that there...
I'm not a physicist but I will add my two cents worth. Time is nothing but change. In a
static universe (without change) there would be no such thing as time. We measure time by comparing the rate of change of one process to another.
As for time travel, to go back in time every change...
Quote: It seems to be a good assumption for objects at least as large as GPS satellites as well as for quantum particles.
What evidence is there that the proportionality holds for objects as large as GPS satellites? The GPS system uses atomic clocks where the timing is a resonance frequency...
The scientific concept of time assumes that there is a proportional relationship between all rates of change. In relativity, where time is malleable according to ones frame of reference, it is assumed that the rate of change of clocks used to measure the velocity of light in a vacuum (c) will...