Re my own "scientists being able to refocus the rays to witness the scene":
So if any of you have ever had sex in the great outdoors your strenuous athletic exploits could be a YouTube viral hit in the year 3115 ;-) ---In [email protected], <s3raphita@...> wrote : After sending the post about time travel being impossible 'cos we ain't seen time travellers . . . it occured to me that time travel could be theoretically possible but maybe it is prohibitively expensive - using up half the energy in the Universe, say - or maybe Our Great Leader Nathaniel Clinton (Hillary and Bill's great-grandson) of the New World Order has forbidden the use of such machines because of the dangerous implications. Also, light rays from the Battle of Hastings have been travelling into space since 1066. You can imagine scientists being able to refocus the rays to witness the scene (but crucially not being able to influence it). ---In [email protected], <[email protected]> wrote : ---In [email protected], <s3raphita@...> wrote : Re this story: on another site someone added a comment - "A time machine in my lifetime would be awesome." To which some wag responded: "If it happens at all it'll be in everyone's lifetime". Nice. Yes. Reminds me of the old physicists joke: "What do we want?" "Time travel!" "When do we want it?" "It's irrelevant!" It's a bit like those who argue that if there are aliens how come we ain't seen them. So if there are time machines how come no one from the future pops up with a cure for cancer. At least aliens are possible, even if they are a bit elusive or can't be bothered to get out much. But is time travel? Nobody has ever demonstrated that your traditional TARDIS, the one we all want, is actually permitted by the laws of physics. But some types of time travel are possible, and one is even really easy. The easy one is to travel relativistically into the Earth's future. All you need is a spaceship that can accelerate at one Earth gravity and then you go for a trip round the nearest star. Time will pass slowly for you but for observers on Earth it will go slow. So when you get back it's thousands of years into the future. This time dilation prediction of Einstein's was actually tested as far back as the 70's with one of those supersonic spyplanes and a pair of atomic clocks. Not what we want as you can't go backwards, not easily anyway but even that's theoretically possible, with caveats. I read a book by a top physicist who'd lost his father in Vietnam and promised himself that if it was possible he would build a time machine and go back to say goodbye. So he devoted a lot of time to it even while he was gaining tenure and a reputation for general extreme cleverness. Working on time travel is career suicide in those days so he kept it quiet until he was sure he'd cracked it and made a presentation to the world's finest minds at a conference, and they agreed with him that it's possible. Tricky though, it involves manipulating the extreme time dilation effects round a spinning black hole with lasers and opening a wormhole to the past and flying through. Because time stands still relative to an observer, and is all so compressed as it spins round, it's apparently possible to travel backwards but not beyond the time when the machine was built. So time travel may be a thing of the future only and you might actually get people popping back with cures for things. But given the difficulty of getting near enough to a black hole to work on it with being destroyed yourself it seems like the last thing anyone is going to consider a good investment. And Stephen Hawking thinks that the wormholes would collapse as soon as you entered them anyway, so it looks like history will continue to be just one damn thing after another...
