Ahhhh...............
:o
Now my head hurts!!!!
:nope:

But to view Hiroshima we would need to be 65 light-years from Earth. How long would it take to get there and set it up? And how would we pinpoint a specific incident for viewing? How would the viewer focus on a chosen location when the Earth is in constant motion?

Ahhh, Antoine Lavoisier! That was the guy I was thinking of but couldn't remember his name. He was put to death during the French Revolution and his wife took over his quest to study matter IIRC.

Oh yes, definitely possible, this method is used to take pictures from the "past" universe. Hubble has taken pictures off galaxies hundreds of millions of years from the "past". The James Webb space telescope that is to be launched in few years is hoped to be able to take pictures of galaxies and planets from the very early universe.

I stand by my objection. Any star we see is a picture from the past, but we can't pinpoint a specific building in a specific city on a specific planet and look at a single incident that took place there millions of years ago. We can only see the light from the stars themselves.

A wonderful feat, but not actually seeing "the past".

I'm not sure if i understand what you are saying right Steve, have been awake for allmost 38 hours and close to 24 of that spent at work, but you seem to be saying that just because we can not make out specific details we are not seeing the past when looking at distant luminous objects in space. Or have I missed something?

Yes and no. I was specifically replying to Privateer's comment that if we placed a viewer far enough from Earth we could outpace the light from 1945 and see the nuking of Hiroshima and Nagasaki. The light we see from distant stars is indeed from the past, but I don't think that kind of viewing of past events is possible, because the further away we get the harder it is to pinpoint anything.

Given a hypothetical situation with perfect conditions I suppose it might be possible to see that event, but hightly doubt it, as the nukes droped then compared to the Suns luminosity is kind of like shining one of those huge searchlights used against night time bomber raids in your face while lighing a candle in the light beam and expecting you to be able to tell the difference.
This next bit im probably going to get wrong, but meh, at 65 light years planets are detected by the wobble they cause in the stars movement as they orbit it so yeah, not to mention the fact that the plant itself spins on an axis completely independant of its orbit (well not completely but meh again) and a nuclear explosion takes a miniscule ammount of time the odds are staggering.

I have to concur with Sailor Steve. We get like 99% of our light from the sun (a tiny fraction we get from starlight), everything we see on Earth we see because sunlight reflects off it unless its lit by a man made source. The best cameras in Earth Orbit can't make out the stuff we left on the Moon from Apollo. The best telescopes are just starting to make out planets in orbit of other stars. Seeing historical events from many lightyears is just not feasible with current or any projected future technology, and I seriously doubt anything short of a Gigaton nuclear blast in space will be visible or detectable for more than a few light years.

Not to mention the fact that you would need to travel faster than light to "Get in front of" the light of the event. If you can travel faster than light than causality or relativity (Pick one) starts to go out the window and time travel becomes possible. You might as well go back and see it for your self.

... clean up on aisle 3... privateer's head has just exploded.

Wow this thread has already gone far beyond my laymans understanding of spacetime and relativity. Reading through made me remember a couple of films involving time travel that were really good.
There was one where future humans from a near perfect (but ultimately stagnant) world would travel back to watch the imperfections (disasters etc...) of the past, the film played out pretty much hollywood style but the idea was a good one.
A better film was the one when future humans had destroyed their world through time travel - as paradoxes occur they cause time 'quakes' in the (future)present measuring on a sort of richter scale of how significant the changes caused by the initial paradox were. They had also managed to open a wormhole to a new world however, they as a species were now bound by the myriad paradoxes that they had instigated, so what they were doing was analysing history to find when groups of people were killed in plane crashes etc... kidnapping them moments before the event and replacing them with corpses, so they could send them through to the new world to start again. That one ended with the line "Time Quake approaching, force, INFINITY!" as reality unravelled around them.
If anyone remembers these films also and can remember what they are called I'd love to watch them again.

My favourite time travel flick though is more recent, it is called 'Los Cronocrimenes' or 'Timecrimes'. It really emphasizes that however much we think we understand, and can prepare for, that things like time travel (even travelling back a few minutes, nevermind going back far enough to change history) would have unimaginable and very, very serious consequences (or would that be presequences?) for those involved.

http://www.imdb.com/title/tt0480669/

Check it out it's well worth a watch, It stays very close to what we (our best scientists) actually know about the subject.

Back on topic what always baffles me is - If a photon moves at the speed of light, time dilation means that from the photons point of view, time does not move. Therefore, for the photon, it exists at all possible points along its path at the same time. How does the photon know which direction it is travelling? when the start of travel happens at the same time as the end of travel, aswell as the actual travel, what difference would a reversal of direction make? None that's what. So who's to say photons don't really burst out of dark objects and zoom towards the nearest light source? and what about.... :damn: oww. time to stop.

Larry Niven wrote a short treatise titled 'The Theory and Practice of Time Travel', in which he approached the concept from several points of view. The final idea was along the lines of the possibility of going to the past and changing things, over and over again, finally ending with the possibility of creating a universe in which time travel was never invented...wait a minute - what it's that's what happened?
:rotfl2: