h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Time travel has facinated us for hundreds of years, the possibilties are still being questioned today. Now heres what i already know:

Forwards: There is a way to cheat going forwards in time. The faster you travel through space the slower your body grows, so if a person can be sent trhough space faster than the speed of ligth then their body clock would come to a stand still right up until the point where they stopped travelling. Now they also reckon it's difficult to do this because of the energy involved and the heat given off, but if a person was sent into a black hole at the speed of light and their body was frozen to abolute zero then they would probably end up comin out of it oalright. The black hole makes it possible for faster than light travle, because not even light escapes the black holes clutches, bt how would you get out the blck hole?

Backwards: Now to go backwards in time you would have to create a stasis field (a field thatnt even time can penetrate) and then (here coes the very hard bit) you would somehow have to make every atom in the universe travel backwards on the path it's taken right up to the point where you wanted to be. These 2 things are very, very experimental at the moment.

Now what i'd like to ask you is if you could give me any information on time travel, both forward and backward. What do scientists know? How close are they? How long do they think it's going to take? and what other theories do they have? Please write and tell me anything you know at all on the subject.
Thanks

sorry for any mistakes in that script, i was typing too fast.

A stasis field is a field that nothing can penetrate not even time.

oooooops

For one thing, scientists don't know how to make a stasis field - that's pure science fiction at the moment.

It's my contention that time travel will never be invented, because as soon as the team working on it get it working, they'll all start travelling further and further back in time, each trying to get a sole patent on the idea, until they all get eaten by velociraptors.

It stands to reason.

From what I understand, time travel may be possible if traversable wormholes can be found (or created). The problem with traversable wormholes is that they need 'exotic matter' to keep the mouth of the wormhole open.

Exotic matter has the unfortunate property of posessing negative mass. Aparently negative mass matter can appear spontaneously in vacuum fluctuations, but it seems unlikely that it could remain stable.

An object with negative mass would repel all other objects in a similar way that objects with positive mass attract other objects (gravity).

If an object with negative mass (N) was near to an object with positive mass (P), N would be attracted to P but P would be repelled by N. This would result in N chasing P, getting faster and faster with no input of energy.


I also have a hazy recollection of another potential method of time travel which involves a neutron star about the mass of the sun, shaped into a cylinder something like 10Km in diameter, spinning very rapidly. If you were to orbit this object you would be able to travel to any point in the objects history, but no further back than that.

So visiting dinosaurs (and being eaten by velociraptors) would not be possible unless such an object had occurred naturally (or been constructed by aliens!) at least as long ago as the dinosaurs were around.

also, the thing about time travel is that if it's possible then it means it's already occurred. People from the future would have come back if it was possible, maybe they live among us.

Has anyone seen '12 monkey's' the terry gilliam film with bruce willis in? if you have you'll understand the concept that time cannot be changed even if time travel is possible.

for instance if you go back in time and kill hitler then the future would be changed and nobody would have ever known who hitler was therefore no-one would go back to kill hitler and then he's alive, but that means that someone gets sent back to kill him, but then he's never existed so nobody gets sent back to kill him so then he's alive and somebody does get sent back to kill him........

you get the picture? it is impossible to change time in this form.

anything to add?

The other popular time-travel idea is multiple universes - that if you travelled back in time and changed history, that would create a new universe with a new history, but the old universe would be unaffected. Gregory Benford's 'Timescape' is a good example of that idea.

David Deutsch goes into great detail about time travel and multiple universes amongst other things (whilst still avoiding equations 'n' stuff) in The Fabric Of Reality - 'A tremendously exciting book' Douglas Adams.

Deutsch 'is authority on the theory of parallel universes.'

What intriuges me about time travel is the way films deal with it. For example The Terminator + Terminator 2. The problem is this - Paradox. Many people find paradoxs quite difficult to get thier heads around but for some reason I don't so I'l try to explain it.
Example...
You go back in time to the year Hitler was born and kill him.
Hitler never lives to start World War 2.
Without World War 2 and Hitler you have no reason to go back in time and kill Hitler.
Hitler then is born because you don't go back in time.
World War 2 is started by Hitler.
You go back in time and kill Hitler
And on and on
The universe - or maybe just your brain - implodes with the complicity of it all.

Do you now understand why time travel will probably never move beyond a theoretical possibility?
If not sit down have a really hot cup of tea get some sleep and read this again. After that I can't help you.

sadly, i already used that example in a previous reply

and you thought it was difficult to understand for some?

if time travel is possible, and it all does fit together (which it probably doesn't) then anything you do when you go back in time changes history. just the fact that your there means you've changed the way things run. if a taxi driver drops you off at a station then your only stopping him piscking up the person he originally picked up therefore making them late to there job interview. this prson then doesn't go on to run the company and get married to the previous bosses daughter. so the children they would have had were never born.

the thing is though, as i've already discussed) if at some point you are going to visit the past (saying it's now your visiting) then you should already be here, shouldn't you?
if time travel is possible at some point then all you have to do is remember to travel back to this point in time and walk through the door to your study, wait a minute..............

no, i didn't walk in the door. not going to happen in my lifetime then.............

think about it.

But if you had travelled back in time to tell yourself that time travel existed then you would have never posted that forum entry and therefore you would not remember to come back to tell yourself....

If you take the multiple universe viewpoint, then the past that you travel back to is not necessarily YOUR past. If you go back and kill Hitler, then you go back to a point in time in a universe where Hitler was/is killed by you. You don't change your history, you change events in the present of a different universe which then goes on to develop in a different way to your own.

To quote David Deutsch: "Time travel may or may not be achieved one day, but it is not paradoxical. If one travels into the past one retains one's normal freedom of action, but in general ends up in the past of a different universe."

Ok, here goes. This is one of the biggies, isn't it?

Start by considering how we all define time. It's linear. We all know that. Or rather, we all percieve it as linear. We live most of our lives by following a system of measured cyclical patterns that occur within time, but are not time itself. Interestingly, the concept of linear time seems to be pretty new on the evolutionary scale: take away the clocks and the calendars and time becomes simply cyclical, not linear at all- measured by the naturally occuring cyclical phenomena of sun and moon and seasons.

There is linear progression, however- but in a circle. Every pass through a given cycle is part of a larger one, and contains many smaller cycles. Similarly, a clock contains cogs, or quartz crystals these days, operating at much higher frequencies, and displays a pattern of nested cycles- seconds, minutes, hours, days, years...

Time is therefore definitely linear, and definitely cyclical. Furthermore, everything that lives, sleeps, breathes, breeds, and dies... and everything inorganic, vibrating at a molecular level... can be thought of as a clock. Every entity keeps its own time- the human mind has days and hours, the heart has its beat, trees grow in great year-long pulses. So time is a field, existing at all points in the universe where matter exists- and even void space is filled with electromagnetic radiation whizzing about the place- at specific frequencies...

When we talk about time travel, what are we talking about? Frequently, almost always, we percieve it in linear terms. The example was used in this thread of 'what would happen if you went back and assassinated Hitler?' Assuming you could, what *would* happen? Hitler would die. Yet there was more to the Holocaust than one man. Not all Nazis could claim they were only obeying orders. Not all Fascists were German. There were British Fascists too- Owsley and co. Fortunately, humanity's luck held- just. Our view of history is that certain individuals somehow create history, and the rest of us tag along. I would suggest that it's the result of a field effect- a mass movement- being idenfified and focused in one individual or small group. Only perceptually, mind, but perceptions are hugely powerful.

'Aha!' I hear you cry. 'Wouldn't the history books be wrong all of a sudden?' Well, what's to say they're right now? What's to say that there aren't thousands upon millions of narrative anomalies, continuity errors, in history? After all, it consists of a collection of memories that agree up to a certain point, and that have been made to tally by historians trying to find a clear narrative past- to establish what happened on the available evidence. When the fake Hitler Diaries were serialised, most people were quite ready to forget the way they'd been told his story and absorb the 'new version.'

Time is not a direction. You cannot travel in it. There is only now. Time is a property of the universe. Now manipulations of that property are certainly possible- Einstein's theories suggest as much. What could we discover about time simply by changing our perception of it?

Whoo. Sorry to go on, folks. Major spliff last night.

There is an episode of Star Trek: Voyager, (its the one in an early season where they go to investigate the destruction of a civilisation by a catastrophic powerstation explosion, only to find they caused it while they were investigating....) where B'ellana Torres puts all the bridge crew straight on these time travel paradox questions: she says something like, "The usual laws of cause and effect do not apply when you are dealing with Temporal Mechanics". So there. In other words, "OK you clever viewers, we know its impossible, but its a darn good plot device and we're not giving it up for anybody".

I have a reasonable understanding of time travel and all of it's paradoxes, and I am very interested in one point which never seems to get discussed.

Here goes:

If mankind gets to the point where he has the ability and technology to go back in time, and, assuming the 'will I alter the future?' glitch has been sorted once and for all; where do all the displaced molecules of air go when he/she arrives at chosen destination/time.

ie. If you got into your time machine or matter transporter and decided to pay a visit to London/1956, as you 'appear' into that place/time, your mass of matter will materialise there. What happens to the human shape piece of air (or even water)?

Is it squeezed to one side? (like dropping a rock in a lake, the water is displaced)

Or is it mixed with your flesh molecules in a nightmarish mess of human/air coctail?

Also what about the missing matter in your present universe/time?

This minor problem is worse when people start to zip all over time and space, leaving matter holes and vacuums everywhere throughout the fabric of space/time.

Why does nobody ever mention this? Am I being just ignorant?

Surely you can not ADD 200lb of human flesh matter to an already infinitely large universe without causing problems.

Maybe all these 'worm holes' are just 'over-flow' pipes in space from very popular space/time destinations into more duller times. Are there millions of people travelling from the year 3220 back to interesting times like 1865 mid-west states (cowboys 'n' injuns). Is there an over-flow worm hole taking matter from that universe back to prehistoric times.

Does anybody reading this follow me?

Here's a thought. If man could travel back in time ('man' as in 'anybody'), why don't we see lots of visitors coming back telling us how to do stuff better, how to cure cancer, and even how to travel in time. Answer - We don't because time travel, although probably possible, may never be acchieved because mankind will blow the shit out of himself in the next 40 or 50 years in a catastrophic nuclear war, wiping out all life. (Mmmm)

Please discuss.

in your argument about matter i think you gave a great little idea, but to be honest what difference will a few million atoms make difference to a universe? matter is constntly being sucked in by black holes all over the universe, and although it isn't really destroyed, its place in the universe is now free.

another good point you made was the displacement of those air/water molecules. now there are arguments which say that if you can travel back in time then it means the person who travels from the future would have already visited this side of the time leap. simply meaning that as you also said if people could travle back intime at some point in the future then they would already be here. now to go back to your first point, even if a person travels back in time and tries to make no effect on an already set past the dissplacement of those air/water molecules is a change enough.

once again we reach the point that says you cannot change the future if you travel back. if you take time as a staright line then you move backwards on this line. now if it's definite that at some point you do travel back in time, then it means it's already happened, so rather than changeing time you become part of it. time travle mayt at one point be possible, but i don't think it's going to happen in our lifetimes. all that can be said is that if time travel is possible then it cannot be changed, because it is constantly happeneing, whether your there in time originally or not. do time travellers walk among us? i doubt they'd tell us if they did.

humans will move onto a new evolutionary stage soon, but because human beings create their own evolution the only thing thats going to chag us will proabably be as you said some catastrophic war. one day it will happen, but they question is when? but thats a totally different question for 'ask h2g2'.............

Apparently a popular theory at the end of the sixties went as follows;

If mankind develops time travel he will want to visit some of the most momentous moments in history.
Mans first steps on another planet are pretty damn momentous.
Therfore, if time travel is possible, there should be a hoard of tourists watching Neil Armstrong getting out of that tin can.
There were no tourists.
Time travel is not possible.

Interesting, huh?

Personally, as to your other comments, I'm for the multiple universe theory. It was good enough for Einstein, so I ain't going to complain.

>>the thing about time travel is that if it's possible then it means it's already occurred. People from the future would have come back if it was possible, maybe they live among us.<<

Not necessarily. Maybe they decided to keep the risks at a minimum by only traveling forward in time.

I read a time-travel novel once where every time someone jumped through time, there was a soft pop as air rushed in to fill the space left behind....Seems to me that that's what would happen, resulting simply in a slightly lower air pressure. But if enough people did it, it might indeed have serious consequences....

I absolutely agree with Ben the Hippy, "Time is a property of the universe".

If one were able to travel in time, why is it assumed that you would end up on earth? If you travelled back one day, for instance, you would look out of your time machine and probably see the Earth a day away. Go forward a day and a day later the Earth would smash into you. But even that is assuming you are still stationary with relation to the sun. If you were stationary with relation to the centre of the universe, the whole solar system would have moved.

If anyone understands what the hell I'm talking about, could they please explain?