Posted: Mon Jun 24, 2013 2:44 pm
You are completely correct in your assessment--no one ever takes the motions of the Earth and Sun as they rotate around the galaxy into account. Typically, they often assume (for whatever reason) that you somehow maintain the proper momentum and spatial vectors when you travel but logic would state otherwise.aTOMiC wrote:Here is a real head kicker in this discussion in my opinion.
There is a component in the time travel debate that is frequently, but not always, ignored.
Suppose you had the ability to travel backward in time with a real world time travel device that obeyed the natural laws of the universe.
Traveling backward in time is not the only concern.
Your destination comes into question.
First of all if you simply engaged your device and traveled backward 75 years you'd end up exactly where you started only in the past. Three quarters of a century ago the Earth wasn't in the same position it is today so you start out with a real problem.
Where exactly was the Earth 75 years ago an how would you determine its location?
The Earth rotates, it also orbits the Sun. Our Solar System rides the great circular disk of the Milky Way galaxy and the galaxy itself is hurtling away from the origin point of the big bang.
For the achievement of creating the ability to travel backward in time the universe does not grant wishes.
Its not as simple as clicking your heels three times and just picturing your destination in your mind and poof you materialize in Europe circa 1939.
The Earth was located in a very specific location at any given time in the year 1939 and that location is very, very, very far from where it is today. With the gigantic ballet the matter in the universe is dancing at all times it would be extremely difficult to determine spatial coordinates for your time travel destination. I haven't even gotten into a discussion about whether the universe itself may be moving as well. Imagine that every body is affected by gravity. The wobble of distant stars helps us discover orbiting planets. Since there is no frame of reference, there is no way to know if or how fast the universe might be rotating around, confusing the location of the actual big bang point of beginning with respect to its actual location, not its relativity to all of the observable matter in the universe.
Sure go ahead and travel backward in time all you want. Its very likely that you'll end up in open space light years away from the nearest star let alone the Earth itself.
All I'm saying is you'd better bring a space suit with lots of oxygen. Provided of course you don't materialize inside a random star or are instantly sucked into a singularity.
Time travel isn't as much fun an idea if you go back in time to try to kill Hitler but Berlin, Germany is dozens of light years away and you have no idea which direction to go and no conceivable way to get there.
The only show I have ever seen that takes your spatial location into account was Red Dwarf. As you probably recall, they managed to retrofit a time drive onto Starbug--how they did that I am not certain buy Kryten was smarter than he looked...sometimes--and travelled back to the 14th century...in deep space.
