Let’s say that you build a telescope with mind-boggling resolution. Not satisfied with winning just one Nobel Prize, you also build a faster-than-light mode of transportation. At this point, you’re a little sick of all the fame and the paparazzi, so you zoom off in your FTL buggy. Just to get away from it all; you know.
After a few days at hyper-speeds, you start to get a little lonely. But you’re too stubborn to go back to Earth after the big fuss you made about leaving. So you decide to check out what people are doing with your telescope (don’t leave home without it!).
My question is, what do you see? The conclusion I’ve reached is that if you’re X light years away from Earth, you’d see an image of Earth as it was X years ago. So if you leave in 2066, go 1000 light years in a few days, and turn back around, you’d see the Normans kicking some Anglo-Saxon ass. Seems like time travel without the kill-your-own-dad paradox. Of course, relativity could make going back home a real bitch.
I think there was a Fred Pohl story in which a spaceship disappeared and some folks were trying to figure out where it went. They used the exact method described in the OP to accomplish this.
I don’t know why anyone would consider this time travel. Whenever we look at anything we are looking at it as it was when the light left it, and not at it as it is now. In most cases the difference is unnoticeable. However, every time you look at the sun you see it as it was eight minutes ago. (or thereabouts) Are people traveling through time (in addition to burning their retinas) every time they look at the sun? Of course not.
So I would suggest that you get to work on you big ass telescope. You should be done with this by dinner time. tomorrow you can start work on that FTL drive. This may take a week or two because it may very well be impossible. Then pack a lunch, take 27 light year trip, come back, and let me know who killed Kennedy.
ellis–this is “time travel” in the same way that watching an old documentary is time travel. You can see the images, but you can never physically interact with the people as it happens.
If you want to reverse your hypothetical scenario, all the light we see in the night sky is from the past. The light from, say, Alpha Centauri is from 4.3 years ago. If you had your super-telescope, we could see who won the 1996 Alpha Centauri World Series, or something like that.
You want big numbers? The light from the Andromeda Galaxy over a BILLION years old. When that light first left its source, there wasn’t even life on Earth.
Sorry if I confused you there, big fella. I wasn’t trying to
give the impression that I considered this on an equal level with stepping into Dr. Peabody’s Time Machine and shaking ol’ Will the Conqueror’s hand. It obviously isn’t time travel in that manner. It is, however, time travel in the notion that it would allow you to observe what had happened in the past.
Interesting that you mention the Pohl story. Just goes to show that great minds think alike. You have any idea where I might find a copy? (was it first in some pulp? early collection? or was it a novel or novella?)
Basically, this thought had occurred to me, and I couldn’t see any flaws in it (provided the damn big telescope and the FTL, of course). I ran it by a buddy, and he agreed it was pretty nifty, so I decided to trot it before the teeming millions before I went off and embarassed myself at the next cocktail party.
-ellis
ps. you might be surprised at how easy it was to build all that. i could tell you who killed JFK, but then we’d have to kill you.
Same deal as with Lance; sorry if I gave you the impression that I thought I could somehow interact with the Conquering Normans. But I don’t think that this would be just a documentary. Ken Burns might be cool and all, but he sure as hell doesn’t have footage of the dinosaurs getting wiped out by a big f*ing meteor. And I think that it would be immensely interesting to watch that footage.
There was a young lady named Bright,
Who could travel much faster than light.
She set out one day,
In a relative way,
And returned home the previous night!
I think it was an extremely minor plot point in one of the Gateway books, or the Heechee Saga, or whatever the hell you want to call it. Probably the third in the series, but that is a guess.
Not to be a pain but why wouldn’t this be time travel?
Forget for a moment that what’s being proposed is impossible. Somehow, someway you have a ship that travels faster than the speed of light (and no sneaking through hyperspace and screwing my post up).
In order to do the equations correctly doesn’t time have to become a negative number? I’m no physicist and math like that makes my brain melt but I thought this is how it would have to work.
When Spaceman Spiff is out there looking back on the earth as it was 1,000 years ago he of course can’t interract with it. But if he turns around and flies back the 1,000 light years in a day wouldn’t he end up in the past? Maybe not 1,000 years in the past but somewhere back there?
Wasn’t something like this the theme of the opening sequence of the movie “Contact”? You recede from Earth at high speed, listening to older and older radio broadcasts as you go.
I don’t recognize the Pohl story, but T.L. Sherred wrote a novella, E for Effort, pretty similar to this idea in 1947. He used a machine that could view the past rather than a long distance telescope but the effect was the same. The owners of the machine used it to film scenes from the past which they then incorporated into highly realistic historical epics. If you’re looking for the story, it was reprinted in The Science Fiction Hall of Fame, Volume IIB.
I do recognize the Pohl story, it’s one of the Gateway series of novels. Unfortunately I can’t remember which book - definitely not the first or last though. Maybe 3rd.
Soemthing similar is mentioned in one of Niven’s Known Space short stories. A spaceship captain decides to show a starseed (interstellar life form) unfurl its sail. The thing is huge and slow though, so the captain had the ship approach the starseed at near light speed. Therefore the 10-hour spectacle got contracted to a one-hour show. Come to think of
There is a similar, real phenomenon called relativistic beaming. Some active galaxies and other astrophysical bodies eject matter at relativistic speeds. When a chunk of the matter is heading almost but not quite towards the observer (Earth), it almost catches up with the light it emitted some time ago. In other words, it’s chasing its own light. So the light from the whole trajectory reaches the Earth almost simuntaneiously, and it looks as if the chunk moved sideways faster than light.
Jeff -
Quite frankly, I don’t know. But I don’t think so. The light that you’re looking at is still X number of years old. And when Spiff zips back to Earth, he wouldn’t be traveling in time, he’d just be seeing light that was progressively younger and younger, until he landed. But I’m not positive. That’s why I asked. Hopefully someone else will come along and help us out.
Nemo, Lance -
Mayhaps I’ll look one (or both) of the two up next time I hit the library.
Everyone is correct that once you get 1000 LY away from the earth your Uber Telescope will see the earth as it was 1,000 years ago. This is not time travel.
However, assuming you somehow did move faster than the speed of light (and didn’t jump through a wormhole or something) I believe you would have to go back in time (Bibliophage–I’m quite aware that this is thoroughly impossible…just play along for a sec).
It would work something like this:
You left Earth on January 1, 2000, and flew 1000 LY in one day.
You look back at the Earth and see it as it was 1,000 years ago.
Let’s now assume you have an instantaeous phone link back to the Earth. You pick up your phone and ask the guy on the other end what day it is and he responds that it’s December 26, 1999. (I have no how the actual math would work out here assuming I’m even correct in the first place).
Now you turn around and fly the 1,000 LY back to earth in a day. When you land the date is December 22, 1999.
Needless to say this causes all sort of potential paradoxes which is probably one of the reasons the universe is setup in such a way as to make this totally impossible. Still, for pure speculation I think this is what would happen.
I knew, right after I posted, that I was going to get busted on my numbers. Yes, the numbers are wrong, but my point remains the same.
Ellis-, sure there are no films of the Civil War, but that’s not my point. Watching old light isn’t time travel, except in maybe the metaphorical sense.