# What people forget about time travel

vivify
Science 04 Feb '15 02:28
1. vivify
rain
04 Feb '15 02:28
Think it through:

2. 04 Feb '15 05:48
Originally posted by vivify
Think it through:

In some time travelling / teleporting movies, the person ends up in the wrong country. Oddly enough, they never seem to end up in the middle of the ocean which is what one would expect if a random point on the earth's surface was selected.
3. 04 Feb '15 08:385 edits
Originally posted by vivify
Think it through:

This could be why we are not inundated by time traveling tourists from the future: Their many bodies are now all floating around in outer space ðŸ˜›
Somehow, they really must make their time travel machines take into account relative motion and that means taking into account both relative position and relative speed. I say "relative speed" because, if that is not taken into account, if you time travel 12 hours into the past to the same spot on the Earth's surface when the that point on the Earth was moving in the opposite direction relative to the earth's axis of rotation because of its rotation on its axis, you could suddenly be traveling sideways at lethal relative speed relative to that point on the Earth's surface and flung to your death.
A similar problem could occur if you traveled six months into the past due to the Earth's orbit around the Sun.
And what about the rotation of the milky way? -so you could end up just about anywhere.
4. 04 Feb '15 09:35
Anyone who will travel in t but not in x, y or z - he will most certainly die in space or under ground. Even a few percent error in the spatial coordinates will put him to death by falling even 100 meters above ground or suffocate 100 meters below ground.

So don't travel in time if you don't know how to do it!
5. 04 Feb '15 10:50
This problem would also apply to travelling forward in time. If one was to significantly slow time down for an object, would it get whipped off into space, as the earth leaves it behind?
6. sonhouse
Fast and Curious
04 Feb '15 12:07
Originally posted by vivify
Think it through:

The Earth moves at a rate of about 200 miles per second through the universe in its corkscrew fashion. So if you are in a time machine you better take all the factors of its movement into account if you want to end up in the target area, assuming you want to time travel on Earth itself.

If you just click on your time machine and go back in the past say, 2000 years ago so you could see JC and the boys or some such, you would find yourself about 2 light years away from Earth.
7. 04 Feb '15 12:15
only a problem if the time machine pops out of existence a it's start point
and then re-materialises at it's destination.

Time machines that don't do this avoid this problem.

For example H G Wells time machine remains fixed to the earth as it moves
backwards and forwards in time, and thus will go wherever the earth goes.
8. sonhouse
Fast and Curious
04 Feb '15 12:491 edit
only a problem if the time machine pops out of existence a it's start point
and then re-materialises at it's destination.

Time machines that don't do this avoid this problem.

For example H G Wells time machine remains fixed to the earth as it moves
backwards and forwards in time, and thus will go wherever the earth goes.
That makes it more than a time machine, it is also a space machine. Time does not peg itself to a planet. You go 1 second in the past, you are 200 miles from where you used to be and now you might be 200 miles underground or 200 miles in space. Either case, you don't have a good outcomeðŸ™‚

I guess there is a certain probability you could end up 200 miles away on the surface of the Earth but that would depend on exactly which direction the Earth is moving through space. If the line was tangential to Earth's surface you would still end up several miles up and you better have wings or a parachute to get down safely.
9. 04 Feb '15 13:38
Originally posted by sonhouse
That makes it more than a time machine, it is also a space machine.
In that case, so am I, and so is my table. Remember that Wells' machine doesn't pop from one time to the other, it only speeds up time inside itself, or runs it backwards. It's like a tape deck fast-forwarding or spooling back, not like a grammophone user lifting the needle through another dimension to the next track.
Wells' time machine does nothing in space that I, or my table, doesn't do as well: it sticks to the planet it was stuck to before, through gravity. It does do something in time that neither I, nor my table, does: it moves through it at a different speed than most objects.
Therefore, it's a time machine. If you want to call something a space machine, I suggest your car.
10. 05 Feb '15 09:47
If you travel from one point in time to another point and this is done instantly, then you have a time machine, as it often is presented.

If you travel from one point in space to another point and this is done instantly, then you have a space machine (analogously), but is presented with other names, like quantum jumps, 'beam me up, Scottie', and such.

A true time/space machine is when you instantly are traveling from a four-dimensional point in the space/time continuum, then you have a true time machine, where the space coordinates adjusts to the point in the rotating coordinate system we have on earth relative to a fixed point in space so it will be safe to travel in time.
11. 05 Feb '15 10:491 edit
Originally posted by FabianFnas
[b]If you travel from one point in space to another point and this is done instantly, then you have a space machine (analogously), but is presented with other names, like quantum jumps, 'beam me up, Scottie', and such.
Teleporter is the usual word.

A true time/space machine is when you instantly are traveling from a four-dimensional point in the space/time continuum, then you have a true time machine, where the space coordinates adjusts to the point in the rotating coordinate system we have on earth relative to a fixed point in space so it will be safe to travel in time.
H G Wells' machine does not transport you instantaneously, but rather takes you along a line through spacetime.
I guess we should see an H G Wells type time machine as an entropy reverser (when used for going back in time), as the machine was always there in the past, but it is experienced in reverse.

If I met a 'time traveler' today that claimed to have come from 2050, then I could claim that he didn't travel back in time, but rather he is travelling forward in time, but remembering the future.
12. 17 Feb '15 16:12
Originally posted by vivify
Think it through:

Like the movie I recently saw..."Interstellar"
13. sonhouse
Fast and Curious
18 Feb '15 01:30
Like the movie I recently saw..."Interstellar"
What did you think of that movie?
14. 18 Feb '15 20:49
Teleporter is the usual word.

[b]A true time/space machine is when you instantly are traveling from a four-dimensional point in the space/time continuum, then you have a true time machine, where the space coordinates adjusts to the point in the rotating coordinate system we have on earth relative to a fixed point in space so it will be safe to travel i ...[text shortened]... 't travel back in time, but rather he is travelling forward in time, but remembering the future.
"H G Wells' machine does not transport you instantaneously, but rather takes you along a line through spacetime."

His machine wouldn't work in reality. It's fiction.
15. sonhouse
Fast and Curious
19 Feb '15 02:28
Originally posted by FabianFnas
"H G Wells' machine does not transport you instantaneously, but rather takes you along a line through spacetime."

His machine wouldn't work in reality. It's fiction.
Well, that would be with our level of physics. I wouldn't count it out for folks a million years ahead of us in the technology game somewhere is some galaxy or other. It's a rather large universe, so I'm toldðŸ™‚