# Time Travel Question [changed title]

I have this theory that I came up with a few weeks ago after science class and studying about how long it takes the light from the stars to reach our eyes. It is like looking many years into the past.

Alot of this is sort of hypothetical but let’s get over that part…lets assume that we could send some humans far enough out in space that the light and images from earth would take one year to reach their eyes. Now here comes the hard part, explaining this; so when they get there they have a device with them that is able to see the earth…would they be looking into a past earth? If so if they could see people on the earth would it be the people doing things that happened a year ago? Could this be a step toward time travel? although we wouldn’t be there we could observe from a great distance the events that went on a year or two ago.

Now I know how fast light travels and to get far enough away that it would take a year to reach you is now impossible but does my theory have any slight chance of being workable? Assuming we found a way to get that far out into space.

If nobody understands what I’m trying to say I will come back and word it differently.

Assuming you have humans one light year away from Earth with the ability to see Earthlings. They will be viewing them as they were a year earlier.

Got it?

Yes. But remember that, since it is impossible to travel faster than light, they had to have departed from the earth more than a year ago, so they’d be seeing things that happened after they left.

Nope.

You can’t travel faster than the speed of light. So no matter how far or how fast you went you would only see images from after you left.

These images will be of times earlier than your present, just as every image of a star in the sky tells us the way that star looked several years earlier. (The nearest stars are 4 light-years away, so we see what they looked like 4 years ago, etc.) But this can in no way be termed time travel. There is no way, even in theory, to do the kind of time travel viewing you speak of.

Time travel itself is not forbidden by general relativity and several physicists - starting with Kip Thorne - have looked at the physics of it all. Doing time travel involves building wormholes and using exotic materials with properties that are not even imaginably realizable so creating one is out of the question for any foreseeable future. And you can’t go back in time before the time machine was built, which may explain why we never see time travelers.

But you simply can’t outspeed light.

EVERYTHING you see is in the past.

The very words you see on the monitor are about a picosecond old.

There are some theoretical physicists who aren’t totally convinced that you can’t beat the speed of light barrier. Theories involving wormholes and other abnormalities abound, some have even suggested that humans will be able to create rips in spacetime via various means using advanced technology. None of it has ever been observed however. If it were true, then it would be possible for a specific person to travel out into space, look back, and “see themself”. This actually creates a number of paradoxes, which is one reason why many believe that faster-than-light travel will always be impossible.

There is no problem with viewing the past. If you could interact with the past, that might pose a problem, but we view the past all the time.

[moderator hat on]
It helps to have descriptive titles. I’ve changed the title for you.
[moderator hat off]

None of what you have suggested “beats” the speed of light. Wormholes and other “rips” in spacetime change the topology of the background manifold. Locally, nothing is travelling faster than light, although globally they are reaching points in spacetime that would be outside the forward light cone were it not for the “rip”.

Is there a quantum version of faster than light? Aren’t there phenomenon at a quantum level that happen instantaneously over distance between related particles. Excuse me for being so general, I’m not sure what it involves…antielectrons maybe?

I’ve always heard this anecdote, and wondered - why not?

The closest thing, as being discussed in the thread on Hidden Variables theories, is the resolution of an EPR state. No information is really being sent, though, so no signal is passing the speed of light.

Short answer from Wikipedia’s Time Travel page:

Long answer: Black Holes and Time Warps: Einstein’s Outrageous Legacy, Kip Thorne’s original book on the subject.

Probably closer to a nanosecond, if I remember the details of Admiral Grace Hopper’s appearance on David Letterman correctly, she produced a handful of lengths of wire, about 15cm long or so (hard to judge on TV) and she called them her “handful of nanoseconds”, as she explained that’s about how long it took a near-speed-of-light signal to travel that length. After Dave and the audience were comfortable with the concept, she produced a small paper packet of pepper - with perfect timing she revealed it to be he “packet of picoseconds”.

Dave had little he could say to this amazing woman

But did she go over to the band to let Pete (the piper) pick the paper pepper packet?