Faster than light speeds—could you see the past?

originally posted by: frostie
Traveling faster than the speed of light means you get somewhere faster than light, not a reverse in time.

BINGO


relativity where ever you are there you are

originally posted by: andy06shake
a reply to: frostie

Think on it this way, if indeed we were somehow able to launch a probe capable of reaching another star with in say 50-100 years(journey time). From our perspective here on Earth the probe would seem to take rather more than 50-100 years to reach its intended target.

So if It launched today 2015 would the spacecraft get there 2065 (lets go with 50 years) It would just feel longer? Or would Timewarp?

Travelling at the speed of light, if it were possible, would have the relativistic effect of travelling into the future ONLY if one were to return to one's point of origin. Clocks move more slowly as we approach the speed of light, therefore, what for you (as the light speed traveller) takes 5 years for example, for those left behind takes much, much longer. On your return you would find all your relatives and friends had passed away.

The idea of travelling into the past is not so simple, one could perhaps OBSERVE the past, with the super-duper wormhole telescope thingy, but you could never arrive back there.

There is however, such a thing as a Tipler cylinder which theoretically can use closed timelike loops to enable travel into the past. But that would require so much energy it is basically just a thought experiment.

a reply to: frostie

From the FTL space crafts perspective 65 years would have passed until it reached its destination but back here on Earth from our frame of reference time would have progress somewhat further than 65 years depending on the velocity of the space craft. This is because as you approach the speed of light time dilation becomes a factor. Never mind your in cress in mass and the fact that the ship would contract in the direction of travel.

This little relativity calculator looks rather helpful.

www.1728.org...

a reply to: andy06shake

Were on the same page

Thanks for the link too!

originally posted by: Thebel
If your ship had headlights on and you were travelling at the speed of light, you wouldn't see any light emitted by those headlights. If your speed would be even slightly slower than speed of light, you would see the lights, but it takes forever to see the actual light.

And if you teleported on planet that is 50 light years from us, you would see Earth as it was 50 years ago. If you teleport far enough, you would see the dinosaurs.

If you were to look back at the earth it would take 50 light years to see, you would see the future, (and most likely be dead) not 50 years ago. It's not like the earth is projecting a camera outwards.

I'll go one better- if you could do a cosmic-scale kind of femto photography and had adequate computing power to account for what light was coming from where, perhaps you could take a picture of the reflection of our own history on a distant body without traveling faster than light.

a reply to: chr0naut

We may indeed be able to see our past, learning from it however still seems to be beyond our capability's, shame really considering hindsight can be such a powerful tool.

a reply to: frostie

Just read that question again, 50 years would pass for the probe not 65, somehow read 2000 instead of 2015.

a reply to: frostie

Hey frostie! Good to see you in the threads. If you have physics questions there is a thread here called "ask me anything about physics or something similar" It's an excellent thread where you can ask real physicists who happen to be members here your science related questions. They are some smart folks in that thread too. I've asked some seriously off the wall questions there and gotten some great responses. I recommend asking member Arbitrageur and MBKennel any of your science questions. They are good guys and really damned smart. Another good member is Bedlam, who really, really knows his science. . ..just don't ask him questions directly related to classified stuff.

a reply to: BASSPLYR

Im drowning in the threads lol

Ive run into these smart people and they make my brain hurt!
I do have a plethora of question for these folks.

Im not even sure what you call physics that has to do with FTL travel

Thanks!

Are you aware of any time other than now? There is no past to recover, no future to anticipate, only reality distortions to be avoided as fantasy.

Simple answer if you could make a trip faster than light yes. Lets say i travelled out 120 light years id be listening to the start of radio listening to their commercials and radio shows. In effect i went back in time to listen to the broadcasts

How is this any different than listening/watching a recording made at the earlier time. One is not at the past event, just hearing/seeing the material.

I've read replies and I will add my own. In short to the post heading no, firstly you can't travel faster then light. But let's assume a thousand lights years away (relatively close) could you use a very very very powerful telescope and view things happening on the surface of a planet, it would be a thousand years in the past. Problem is I personally don't think you would be able to because light wouldn't carry so precise an image over such a distance. even now planets aren't seen they are mostly infurred. It wld take like a planet size telescope in dead of space with a clear vision of the target. plus you wld be looking at the past of some planet not yours. Instantanious travel, then yeah it probably can happen. But instantanious travel is pretty damn doubtful

originally posted by: TheMadTitan
Interesting concept. Say we had wormhole tech, open a wormhole next to earth with the exit say 100 million light years away. Send a telescope through and have it look at our solar system while instantly sending info back through the wormhole. Voila! Front seat tickets on the creation of the earth.

a reply to: thesearchfortruth

Um, you'd have to go out to around 4.5 billion light years for that. So it's more like, "Voila! front row seats to the age of the dinosaurs".

Of course such a telescope that could see in that detail from that far away would be bigger than the Wormhole itself. In fact you'd have to send probably millions of small telescopes through the wormhole to create a interferometer the size of a small galaxy to see anything from that distance.

originally posted by: allistar
I've read replies and I will add my own. In short to the post heading no, firstly you can't travel faster then light. But let's assume a thousand lights years away (relatively close) could you use a very very very powerful telescope and view things happening on the surface of a planet, it would be a thousand years in the past. Problem is I personally don't think you would be able to because light wouldn't carry so precise an image over such a distance.

It wld take like a planet size telescope in dead of space with a clear vision of the target. plus you wld be looking at the past of some planet not yours.

Oh but it does. That's why we have very precise images of galaxies many millions and billions of lightyears away. All you'd need to see details on an exoplanet from 1,000 light years away is a very large optical interferometer, and when i say much bigger I mean larger than our solar system because an optical interferometer the size of our solar system would be able to resolve a Honda Accord around 100 light years away.

1,000 light years to get the same resolution would I am doing the math correctly would require an optical interferometer about 5 times the size of our solar system.

even now planets aren't seen they are mostly infurred.

That's not a limitation of light but our ability to gather it while blocking out the light of the star. Want to see planets better? Build bigger telescopes and. It's that simple. We have taken images of some young giant planets with current telescopes by the way but they're just dots for now.

The ratio of the our Sun's light output to Earth's reflected light is about 1 billion-to-1 for a solar type star. If you want to look at an earth around a dimmer, smaller, red dwarf star then that ratio gets knocked down to about 1 million-to-1 which is technically feasible with today's equipment if we chose to build an 8-20 meter version of Hubble (which is completely doable).

Instantanious travel, then yeah it probably can happen. But instantanious travel is pretty damn doubtful

How about this one...

Suppose Harold White, NASA et all work out an actual warp drive in the next 100 years.

Because the distance is not that far, 200 light years is relatively nearby, you could fly a bunch of telescopes (A larger version of Seth's hypertelescope interferometer I linked above) out to a region of space 200 light years away and look back at the Earth.

At 10c (ten times the speed of light - a speed Dr. White references frequently) it would take 20 years to get to 200 light years.

So let's say they launched these telescopes in 2080.

They'd arrive at the 200 light year target in the year 2100 but they'd be seeing the Earth as it was in the year 1900.

So for the next 200 years Earth would be treated to a distant view of the events of the 20th and 21st centuries.

Was it clear skies during the Kennedy Assassination?

How about 9/11?

Any event popular in conspiracy circles could be viewed down to the size of a Honda Accord on Earth provided there were clear skies it happened on the side of the world viewable from the telescope's location.

Pretty cool huh?

Of course that all assumes Alcubierre warp drives are possible and that NASA has actually confirmed Alcubierre warp theory.

originally posted by: The Vagabond
I'll go one better- if you could do a cosmic-scale kind of femto photography and had adequate computing power to account for what light was coming from where, perhaps you could take a picture of the reflection of our own history on a distant body without traveling faster than light.

Yes the reflection concept is a nice theoretical way to look into the past without having to exceed light speed, but whether you used that or flew a telescope faster than light away from Earth, we don't have the technology to see very much detail.

We can't even aim a telescope at the moon and get a good view of the Apollo landing sites. Can you imagine how bad the resolution would be light years away? Using a mirror would double the effective distance.

Even though it's not practical, it's an interesting thought experiment.

I forgot to add. The example above assumes instantaneous communications. If they were just sending regular radio signals or laser signals to send back the images collected then they would take 200 years to arrive back at Earth.

In that scenario Earth in the year 2300 would be viewing Earth as it appeared in the year 1900.

a reply to: JadeStar

I don't know Jade but might you have got carried away?

Let's look at this realistically, IF the Alcubierre warp drive worked, not only the ship, but all photons following and in front of, as well as accompanying the ship would be swept along, wouldn't they? How in this case could one look back?

Wouldn't a position need to be established in order to receive any emissions, and wouldn't the act of establishing a position close the warp?

originally posted by: Arbitrageur

We can't even aim a telescope at the moon and get a good view of the Apollo landing sites. Can you imagine how bad the resolution would be light years away? Using a mirror would double the effective distance.

My first digital camera was about 160 x 120 pixels more than 20 years ago. Never say never.