Why time travel may not be possible

[Ken H]

I was inspired for this by a cartoon I saw somewhere, but I can't find it now.

Say you have a time machine and desire to go back (or forward) to another time. You set the time machine for say, 6 months in the past. Press the big red Go button and POP!, you are in space and immediately explode into bits. The reason for that is the Earth is on the other side of the sun and hadn't reached the point from which you started. Not only that, but you would have also wound up closer to the center of the universe than the Earth was when you left it. Of course, if the time machine was also a space ship, you might be okay, if you planned carefully and had not arrived where a star or other object would be!

The above may be true if time is real. If time is an illusion then you may still find yourself on Earth. If time is an illusion merely in your brain, then you might not be able to travel back further than your birth date (unless there is a collective of memories from past generations). Also, time may have already started and ended and we are merely experiencing a very short section of it in our minds. In that case, time travel may be done safely.

Any ideas on this?

[Dave B]

Der, my brain hurts . . .

[Alan C.]

It always baffled me (when I used to watch Dr Who) Why he didn't just travel through time, but to a completely different place.
Surely he should still have been on a street in London (or wherever) but just in a different time?

Ken, I wouldn't rule out going forward in time (though it's vanishingly unlikely) I would say going back in time is not possible.

[Fia]

"Time is an illusion - lunchtime doubly so"
Douglas Adams

[Ken H]

Actually, Alan, I believe that travel backwards in time would be more likely possible. We know that the past has occurred (or at least we think so), but since the future might not have happened yet, I don't see how one could travel there.

@Dave B: Take two aspirin. Some whisky might help also.

[Dave B]

The whisky certainly helped . . .

Um, if this were a problem in the space/time continuum that NASA and other clever people use when navigating their space ships hither and yon in the Solar System I cannot see any prob in the class of re-appearing in free space or some other nasty place.

It might constrain our travels but surely it would be possible to calculate the position of any point on the surface of the Earth at some time in the future or past (ignoring all paradoxical probs for the moment)? OK, there is a degree of accuracy required here, emerging with merely one tiny part of our anatomy or equipment trying to occupy the same piece of space as, say, the arm of a chair, might result in some interesting effects. Or we might emerge at a point that should be solid ground, only to find some sod has dug a big hole.

So, technology to the rescue: our time ship should be sealed and able to fly, launching itself across time from a point in the air that, hopefully, will not be occupied by a building some time hence.

Wells never had this problem, bugger ignored it . . .

[Alan C.]

Ken
Actually, Alan, I believe that travel backwards in time would be more likely possible. We know that the past has occurred (or at least we think so),

I'm interested to know how you think that would be possible Ken? Some kind of reversal of the laws of physics?

but since the future might not have happened yet, I don't see how one could travel there.

If one could travel faster than the speed of light? Maybe?

Reading this before posting...............Nah! Time travel is a load of bollox And I feel ashamed for even getting drawn into it

X posting with Dave B. And going to my bed Goodnight all.

[Lifelinking]

Ken, I wouldn't rule out going forward in time (though it's vanishingly unlikely) I would say going back in time is not possible

Actually, Alan, I believe that travel backwards in time would be more likely possible. We know that the past has occurred (or at least we think so), but since the future might not have happened yet, I don't see how one could travel there.

I seem to remember Steven Hawking arguing that time travel back in time might be theoretically possible, but not forward in time, in the Brief History of Time.

G'nite Alan

[Dave B]

G'night all.

[Paolo]

A time machine may work, but it would only be able to operate within the time span it had been operational for and it could only transmit information by utilising quantum entanglement.

Transmitting matter through time is implausible at best.

[Ken H]

The whisky certainly helped . . .

Umm, Dave, what whisky did you have? I may need it to understand Paolo's link!

[Alan H]

Um, if this were a problem in the space/time continuum that NASA and other clever people use when navigating their space ships hither and yon in the Solar System I cannot see any prob in the class of re-appearing in free space or some other nasty place.

NASA can't actually predict locations accurately. I can't remember the details, but their calculations of future positions of spacecraft (the ones going a long way, at least) have been a small amount out and they've not worked out why yet. There was an article in new Scientist a few months ago...

[Paolo]

The whisky certainly helped . . .

Umm, Dave, what whisky did you have? I may need it to understand Paolo's link!

In simple terms, quantum entanglement is a relationship between objects that means one reacts to a change in the state of the other at a faster-than-light rate (I think it's at least 10,000 times faster than the speed of light). From what I can tell, the implication is that if two entangled objects are separated by accelerating one away at high speed (esp. near light-speed) while the other is kept stationary, the usual laws apply and the one that travels will experience a slowing of time. The assumption is that since the quantum entanglement between objects should remain, despite the temporal offset. So when the one that has travelled returns, it should be transmitting information back in time and the stationary piece should be transmitting forward in time. Hence you have a two-way information time machine, but it's only operational within the constraints of the first separation of the entangled objects.

[Dave B]

NASA can't actually predict locations accurately. I can't remember the details, but their calculations of future positions of spacecraft (the ones going a long way, at least) have been a small amount out and they've not worked out why yet. There was an article in new Scientist a few months ago...

Interesting that they can't work out why the error occurs - but my post was just a little tongue in cheek really.

After time travel and Paolo's quantum entanglements the subject of teleportation will probably raise its head. I watched Mikio Kaku's piece which included that the other day. Something else that would be nice except for collecting all the teras of terabits of info in even a small object instantaneously so that a perfect copy can be translated.

Might get instant (or as near as makes no difference) communications out of it though.

[Daniel P]

You set the time machine for say, 6 months in the past. Press the big red Go button and POP!, you are in space and immediately explode into bits. The reason for that is the Earth is on the other side of the sun and hadn't reached the point from which you started. Not only that, but you would have also wound up closer to the center of the universe than the Earth was when you left it.

I don't think there is such a thing as absolute distance and position within the universe, though. It's all relative within the space-time framework.


Dave - Verry funny cartoon. It had me laughing my heart out!

[Alan H]

Interesting that they can't work out why the error occurs - but my post was just a little tongue in cheek really.

Ah!

Earth's rotation may account for wayward spacecraft

[Dave B]

Interesting that they can't work out why the error occurs - but my post was just a little tongue in cheek really.

Ah!

Earth's rotation may account for wayward spacecraft

Thanks, Alan, I now sort of think I might have an iota of an inkling as to what they are talking about . . .

[grammar king]

I was inspired for this by a cartoon I saw somewhere, but I can't find it now.

Say you have a time machine and desire to go back (or forward) to another time. You set the time machine for say, 6 months in the past. Press the big red Go button and POP!, you are in space and immediately explode into bits. The reason for that is the Earth is on the other side of the sun and hadn't reached the point from which you started. Not only that, but you would have also wound up closer to the center of the universe than the Earth was when you left it. Of course, if the time machine was also a space ship, you might be okay, if you planned carefully and had not arrived where a star or other object would be!

The above may be true if time is real. If time is an illusion then you may still find yourself on Earth. If time is an illusion merely in your brain, then you might not be able to travel back further than your birth date (unless there is a collective of memories from past generations). Also, time may have already started and ended and we are merely experiencing a very short section of it in our minds. In that case, time travel may be done safely.

Any ideas on this?

Ah, depends though. If you need a time machine at both ends, then you could travel through time and space, and end up wherever the second machine is.

[bobb]

Well, here I am in the future, and I discover that after Grammar King's post on September 5, no-one posts on this thread for over a month.

[animist]

a common objection to backward time travel is that one might alter the past (eg by killing an ancestor) in a way which would result in one's own non-birth. A friend who is keen on time travel (the idea that is) gets over this using the multiverse theory. If one went back and killed the ancestor one would indeed produce a universe where one did not exist - but this would be a new universe, additional to rather than replacing the "existing" one. Any ideas?