Astronomy/physics earth rotation question

[Modelworks]

I was watching something scifi and they were doing time travel when something dawned on me. If someone were to travel 100 years into the past or future would the place they are going in the future be the same point in 3d space in the future ? How much does the earths position change from year to year ?

If a person was standing in a parking lot in NY city and went 100 years in the future from that location, would they even still be in the parking lot ? Or could they be somewhere else like over an ocean or even in space ?

Would time travel to the future also require calculating where the 3d spot you are standing is located accounting for the earths changes ?

How much are the 3d coordinates of something like a house this year, different from those the year before if using something external to the earth as a reference ?

 

[silverpig]

The answer is a lot, or nothing.

Position is relative, and every reference point is arbitrary. If you are standing in front of the Chrysler building, then the Chrysler building is your reference point and you can say you'll be in front of the Chrysler building.

But the Chrysler building is on the earth and the earth moves relative to the sun. Our orbit wobbles so there's a good chance that, relative to the sun the Chrysler building's position on Jan 1 2011 will be inside the earth, or out in space as compared to the Chrysler building's position on Jan 1 2010.

But the sun is moving...

And so is the galaxy...

And so is the local cluster...

So yeah, all of this stuff is moving. Physics is the same in any inertial reference frame, so you can arbitrarily pick the earth to be the non-moving center of the universe and your physics will work out, but this is just an arbitrary choice.

While some say there is no absolute rest frame for the universe, I'd say that there is one choice which is less arbitrary than the others: the frame of motion where the dipole term from the cosmic microwave background is zero. That is, the frame of motion which is at rest compared to the afterglow of the big bang.

If you want to ask how fast we are moving compared to that, well I don't know off the top of my head, but it's fast enough that you'd be way out in space with a simple "time shift".