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General Science => General Science => Topic started by: abrooks051 on 20/07/2019 01:51:47

Title: Wouldn't Earth moving through space be a big problem for time travel?
Post by: abrooks051 on 20/07/2019 01:51:47
I enjoyed "The Time Machine" movies, the original and the remake. However, I began to think about how this might work in the real Universe.
Let's say I sit in my machine, in my study and look out my picture window at a store across the street. Now in the movie, as I move forward in time I watch the world move before my eyes. Here is the problem. The Earth is moving, rapidly in space as is the Solar System, the Galaxy, our "Cluster", etc.
As I push the time lever on my machine, rather than watching the world move outside my window, I would be immediately moved a great distance, since the "space" where my machine is sitting (it's x,y,z,c) would remain stationary as the rest of the Universe speeds away from me. If I am very unfortunate, by the time I stop my machine I will be sitting in the cold darkness of space. Also, regardless of how long I continue there will probably be no chance that I would luck into settling in a habitable spot on any planet ever.
I believe I will stick to using history books for my time travel, much safer.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: Halc on 20/07/2019 02:20:37
rather than watching the world move outside my window, I would be immediately moved a great distance, since the "space" where my machine is sitting (it's x,y,z,c) would remain stationary as the rest of the Universe speeds away from me
First of all, and most important:  There is no such concept as a 'location in space' with coordinates and such.  Not even the absolute interpretations assert such a thing, since the coordinates of our solar system is never specified.  Only relative coordinates are ever used.  And what is the 'c' anyway?  c is a constant speed of light, not a coordinate.

Second of all, why should this fictional machine (which seems to work by staying parked, bolted to the floor if you like) suddenly require to take a different trajectory?

The machine as depicted (moving forward) exists already, and is effectively achieved with cryonics.  Anesthesia almost does the job, but doesn't prevent ageing.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: alancalverd on 20/07/2019 09:25:48
If everything is moving in x,y,z as t varies, then you will also move in x,y,z with t, so whilst the stars and planets will appear to whizz about as you move forward or backward in time, your position as the origin of all you observe, will not change (though the chair will rust and crumble as it gets old, or revert to iron ore and a live horse as it gets young).

The real problem, however, is to prevent yourself becoming dust or reverting to an ovum.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: abrooks051 on 20/07/2019 11:13:17
Halc.
https://en.wikipedia.org/wiki/Spacetime
My bad I should have used "t" not "c".
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: jeffreyH on 20/07/2019 12:02:45
Traveling forward in time requires no action at all. Just sit in place. The problem is traveling backwards in time. That is, if you travel a worldline different to the one that got you to the present. You are then creating energy out of nothing.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: Halc on 20/07/2019 12:54:02
Halc.
https://en.wikipedia.org/wiki/Spacetime
My bad I should have used "t" not "c".
If you remain at x,y,z,t, then your time machine doesn't go anywhere.  The whole point of the machine is to vary t, and ending up in the correct place is no more of a problem than selecting an orientation for those 4 axes so that your start and end events are in the correct position on (presumably) Earth.

That's how I get to work each day.  I get in my time machine (a Hyundai) and select an orientation of the axes so that only t changes but not x y or z.  Then the world moves under me and I just travel through time.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: abrooks051 on 20/07/2019 14:58:13
Halc
However, your Hyundai is gravitationaly locked to the Earth, going where the Earth goes, where as my time machine would supposedly not be.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: Halc on 20/07/2019 15:07:59
However, your Hyundai is gravitationaly locked to the Earth, going where the Earth goes, where as my time machine would supposedly not be.
If so, it appears that my Hyundai is a better (or at least safer) design than the device you have in mind.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: abrooks051 on 20/07/2019 19:14:41
Halc.
Quite so. Thanks for the back and forth.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: Bored chemist on 20/07/2019 19:53:59
"Wouldn't Earth moving through space be a big problem for time travel?"
Only if time travel was real...
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: abrooks051 on 20/07/2019 21:20:07
Bored chemist.
Time travel is real, you do it every day. However, "retro-time travel", that is another thing.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: Halc on 20/07/2019 21:37:00
Time travel is real, you do it every day. However, "retro-time travel", that is another thing.
How is what my Hyundai does not retro time travel?

I get in the thing at 9AM at work and am back at home at 8AM an hour earlier.  Ta-Daa!   Retro time travel.
Or one could argue that I am not present at home at 8AM this morning, but I have witnesses.

Admittedly, I could not have the device take me back to 1955.  It seems to have a limit of 2013.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: abrooks051 on 20/07/2019 22:30:44
Halc.
You just brought up a good point. I have actually traveled back in time. I was traveling to California and I passed from the EST zone into the CST zone. One second it was 09:00 and a second later it was 08:00!
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: Halc on 20/07/2019 23:10:59
That's just playing with a clock.  Without crossing any time zones or other cheats, my car puts me 50 minutes ago.
That's time travel, same as the forward method.
Title: (and aRe: Wouldn't Earth moving through space be a big problem for time travel?
Post by: evan_au on 21/07/2019 00:18:20
Quote from: OP
Wouldn't Earth moving through space be a big problem for time travel?
- It takes a lot of energy to move out of Earth's gravitational field.
- It takes a lot of energy to change the velocity of something travelling around the Sun at 30 km/second (and around the center of the galaxy at 230 km/second), and just stop it.

So Conservation of Energy and Conservation of Momentum suggests that you will remain at the surface of the Earth (if we ignore the fundamental problems of time travel itself).
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: yor_on on 30/07/2019 15:37:03
Depends. You have length, width, height and time. That's the four dimensions we use called SpaceTime. If you would be able to go back in time a hundred years the relative coordinates we would give Earth would differ from the ones you would have as you 'exited'. The same if you go forward in time of course. Then again, that's a tricky one as it belongs to 'relative motion' which locally defined (not using relative coordinates) is indistinguishable from being 'at rest'.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: abrooks051 on 06/08/2019 13:48:38
Halc:
A thought occurred. I had a "re-think" on the time machine problem. Actually, the time machine would remain on the Earth as it moved through time due to gravity. The chair would be drawn to the Earth, constantly, so it would have to move with the planet. My scenario would occur if you were able to negate "gravity". If you could turn off the Earth's gravity, say for 10 seconds, my chair would end up staying in one place as the Universe moved away. Or would momentum keep me close to the point where gravity was switched off? Hummmm.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: Halc on 06/08/2019 14:22:27
If you could turn off the Earth's gravity, say for 10 seconds, my chair would end up staying in one place as the Universe moved away.
The universe has no location, so cannot move away.

If you could turn off Earth's gravity for 10 seconds, besides killing the majority of the population of Earth, your machine would become inertial, ceasing its otherwise ~3cm/secē centripetal acceleration.  Over 10 seconds, that will displace your device (and the landscape with it) by up to 1.7 meters (depending on how close you are to the equator), hardly enough to get it out of Earth's gravity well.

Doing so breaks just about every conservation law in the books, but hey, we're talking time travel here, so we've already presumably thrown the laws of physics out the window.
Title: Wouldnt Earth moving through space be a big problem for time travel
Post by: AustinnEp on 30/08/2019 23:47:58
1000 years into the future this time, to see whats been proven true, whats been proven wrong, what were worrying about now that they dont even remember.
Title: Re: Wouldn't Earth moving through space be a big problem for time travel?
Post by: Paul25 on 19/03/2020 14:44:07
Only in the returning home stage