Sigh-Fi

Implying that there is a privileged reference frame of the universe that you can be still relative to

lol .... time travel is possible and many species, and individuals have done it many times in the past and in the future. It's just that they keep appearing in random places in the universe in empty space.

There are hundreds, thousands, millions or billions of poor unfortunate time travellers that all appeared in empty space or embedded in rocky planets or asteroids ... or appeared next to a star and immediately just vapourized ... or just suffocated and froze to death.

And all throughout time, they all keep attempting it never knowing that it does work, but that it has unfortunate consequences.

Aren't all time machines also space machines? Since space and time are intrinsically linked

There was a not great scifi show about time travel called seven days. They had a alien time machine that could go back in time seven days. Three trick was you had to pilot it as time went backwards chasing the earth.

The main character would often crash somewhere and have to call in to get picked up after a time jump. There was a great scene where he crashed in a civil war reenactment and had a "oh shit I went back to far" moment.

More pixels

The problem with this line of reasoning is that it assumes a universal frame of reference, which inherently doesn't exist. Motion, or lack thereof, is inherently relative.

Wouldn’t everything be relative to the gravity influence?

When you would travel through time, it would make more sense that you appear in the future in the same spot relative to the thing holding you there now, the universe has no absolute X,Y,Z coordinates.

Unless it has enough technobabble to retrocausally gravity tether the machine in space and moved through time without somehow violating something something... Look, just reverse the polarity, it'll be fine.

I am wondering, if your time machine was also a spaceship, when you jumped back, say, 50 years: how far would you need to travel to make it back to Earth from where you are in space if you left tomorrow (May, 29th 2025)?

I get the feeling that calculating a space shift perfectly for a long enough time jump so that one would appear exactly on the surface of planet Earth (not more that a meter or two above and definitelly not at all below) would probably be extremely hard giving the precision required and how gravitation works: theoretically every single body in the Universe affects the position of planet Earth and each other, and whilst the effect of gravity drops steeply with distance, over enough time the errors of not having calculated using all bodies add up, which for very precise positioning (not merelly "near planet Earth" but actually above but not too high a certain point in its surface) would probably get dangerous fast.

So I bet that if we ever do time travel it will only really work for really small timeframes (forget about going back a couple of million Earth orbits to the time of the dinossaurs) or it will both have a space shift and a time shift with a vehicle capable of at least limited space flight and reentry so that a "near planet Earth" error margin is acceptable in the spacial shifting part.

This is, of course, before we go into the whole time paradox discussion.

PS: I was curious so looked for and found a paper about the influences Earth's orbit. One of the interesting conclusions one can derive from it is having to take in account the collision with the asteroid that killed the dinossaurs if one wanted to travel back in time to the time of the dinossaurs with a suitable space shift to end up on the Earth's surface.

gelbanana

Time travel for physical beings is a much more difficult process then sending a message. If the position of the orbiting Earth at your destination date is not accurately calculted...

I read some time travel short story once where science found time travel was possible, but you had no control on where you go in the universe. So they went to the only place they could get to, the big bang.

Neat! So basically a free ride to an extrasolar system that's able to host life if you get really lucky. Kill two birds with one stone, what could go wrong?

V o i d b e r g

Safety not guarenteed.

You just need to phase back into time just long enough to maintain a paired momentum

Yes! Thank you. Lots of time travellers lost in the void or buried in solid objects.

Some possible ways of dealing with this:

• The time travel device does the complicated math to get the time and position correct, assuming the SF writer only wants to deal with 4 dimensions.

• Tunneling effect so that it's a straight point to point between the two timelines.

• Get Weird. Invoke quantum entanglement to rearrange the exact same atoms that make up the time travellers' bodies in the destination timeline, because mass/energy can never be created, only borrowed, and perhaps the universe has a conservation of mass/energy rules and can't add more mass/energy from a foreign timeline without tipping the balance from a "Big Rip" end of the universe event to a "Big Crunch" event.

I always figured if the creator is smart enough to figure out how to time travel, they're smart enough to account for where things will be at that point in time.