Time Travel is Science Fiction

http://www.theweek.co.uk/health-science/59106/time-travel-may-be-possible-says-new-research

Physicists banish the 'grandparent paradox' with successful time-travel simulation
LAST UPDATED AT 13:42 ON Mon 23 Jun 2014
Physicists studying the behaviour of single particles of light say they can now discount one of the main theoretical objections to time travel.

During research published in Nature Communications, scientists at the University of Queensland designed an experiment that simulated the effect of a photon – a particle of light – travelling back in time and interacting with its older self.

"Time travel was simulated by using a second photon to play the part of the past incarnation of the time-travelling photon," said University of Queensland physics professor Tim Ralph.



Read more: http://www.theweek.co.uk/health-sci...y-be-possible-says-new-research#ixzz3JPJ7VQCH
 
http://arxiv.org/abs/1405.1283v1

ABSTRACT:
We calculate the Casimir energy-momentum tensor induced in a scalar field by a macroscopic ultrastatic spherically-symmetric long-throated traversable wormhole, and examine whether this exotic matter is sufficient to stabilise the wormhole itself. The Casimir energy-momentum tensor is obtained (within the R×S2 throat) by a mode sum approach, using a sharp energy cut-off and the Abel-Plana formula; Lorentz invariance is then restored by use of a Pauli-Villars regulator. The massless conformally-coupled case is found to have a logarithmic divergence (which we renormalise) and a conformal anomaly, the thermodynamic relevance of which is discussed. Provided the throat radius is above some fixed length, the renormalised Casimir energy-density is seen to be negative by all timelike observers, and almost all null rays; furthermore, it has sufficient magnitude to stabilise a long-throated wormhole far larger than the Planck scale, at least in principle. Unfortunately, the renormalised Casimir energy-density is zero for null rays directed exactly parallel to the throat, and this shortfall prevents us from stabilising the ultrastatic spherically-symmetric wormhole considered here. Nonetheless, the negative Casimir energy does allow the wormhole to collapse extremely slowly, its lifetime growing without bound as the throat-length is increased. We find that the throat closes slowly enough that its central region can be safely traversed by a pulse of light.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""

As I have said, and as most sensible people will agree, achieving time travel is not going to be easy, if it can be done at all.
But by the same token, no one with any sense can logically say categorically that it will not, or cannot be done.
 
What with all the excitement and mindless repetition of moot points, I never yet have had a chance to ask:

If time travel is someday, some how invented (and, of course it never will be), but let's pretend, - why don't we know about it? Why haven't we seen any time travlers? Are they as shy as the aliens who come her ein UFOs? Why hasn't some evil doctor from the future come back and set up a sports betting empire or just kicked our collective ass with his superior firepower technology and settled in to rule the world like General Zod in the Superman movie?

Is it because of the temporal directive? Are the time travelers of the future so gentle, genteel and enlightened that they will have set up a time prime directive (prime time directive?) that (har har) forbids them from interfering with primitive, past imperfect cultures?

It's puppy-dog, cute baby kitty cat dreamy-eyed enough to believe in traveling back in time, but to suppose there are no bad guys in the brave new world that has such machines in it is just too naive.

We know there never will be time machines because if there were some 45th century butthole would have gone back to, say, Germany 1936 and armed the Nazis with 45th century weapons because people like him in 4647 still cannot abide Hebrews and Poles and he'd like to go back in time and hack at the root.
 
Well, we still have no evidence that there are other intelligent civilizations in the universe.

Would you propose that SETI is a waste of time?
 
Landau Roof said:
If time travel is someday, some how invented (and, of course it never will be), but let's pretend, - why don't we know about it? Why haven't we seen any time travlers?
Click to expand...

Because:
1) You may need a mechanism at both ends. Thus we will never travel back in time past where the device is invented.
2) Humans as a race may kill themselves off before they develop one.
3) We may be the forked reality in which no one travels back from the future, at least until our present time.

We know there never will be time machines because if there were some 45th century butthole would have gone back to, say, Germany 1936 and armed the Nazis with 45th century weapons because people like him in 4647 still cannot abide Hebrews and Poles and he'd like to go back in time and hack at the root.
Click to expand...
They may have done that - and again, we might just not be in that reality.
 
billvon said:
Because:
1) You may need a mechanism at both ends. Thus we will never travel back in time past where the device is invented.
2) Humans as a race may kill themselves off before they develop one.
3) We may be the forked reality in which no one travels back from the future, at least until our present time.
Click to expand...
Three very good points, but there is a fourth.

Landau Roof said:
Why hasn't some evil doctor from the future come back and set up a sports betting empire or just kicked our collective ass with his superior firepower technology and settled in to rule the world like General Zod in the Superman movie?

Is it because of the temporal directive? Are the time travelers of the future so gentle, genteel and enlightened that they will have set up a time prime directive (prime time directive?) that (har har) forbids them from interfering with primitive, past imperfect cultures?

It's puppy-dog, cute baby kitty cat dreamy-eyed enough to believe in traveling back in time, but to suppose there are no bad guys in the brave new world that has such machines in it is just too naive.

We know there never will be time machines because if there were some 45th century butthole would have gone back to, say, Germany 1936 and armed the Nazis with 45th century weapons because people like him in 4647 still cannot abide Hebrews and Poles and he'd like to go back in time and hack at the root.
Click to expand...

Let's create a law and not a way to enforce it, said no civilization ever.

If you want to take things to that sort of ridiculous extreme, there's a further ridiculous extreme, or point that you must also consider - law enforcement. Maybe the reason why the 45th century butthole hasn't come back in time and armed the Nazi's is because the 45th century temporal continuity police traveled back in time to a point before the 45th century butthole travelled back in time but that was after a morally and ethically acceptable amount of evidence of his intent to commit the crime could be gathered him and stopped him from ever being able to travel back in time.
 
Trippy said:
If you want to take things to that sort of ridiculous extreme, there's a further ridiculous extreme, or point that you must also consider - law enforcement. Maybe the reason why the 45th century butthole hasn't come back in time and armed the Nazi's is because the 45th century temporal continuity police traveled back in time to a point before the 45th century butthole travelled back in time but that was after a morally and ethically acceptable amount of evidence of his intent to commit the crime could be gathered him and stopped him from ever being able to travel back in time.
Click to expand...

Conspiracy theorist!
 
Landau Roof said:
What with all the excitement and mindless repetition of moot points, I never yet have had a chance to ask:
Click to expand...


And all good and valid points that just seem to sail over the head of those that just wont face the fact that time travel is not forbidden by the laws of physics or GR.
So the possibility will always be open, as difficult as it may seem to achieve.

The rest of your post as others have noted is just extreme drivel...not worth commenting on.
 
Trippy said:
Three very good points, but there is a fourth.
Let's create a law and not a way to enforce it, said no civilization ever.
If you want to take things to that sort of ridiculous extreme, there's a further ridiculous extreme, or point that you must also consider - law enforcement. Maybe the reason why the 45th century butthole hasn't come back in time and armed the Nazi's is because the 45th century temporal continuity police traveled back in time to a point before the 45th century butthole travelled back in time but that was after a morally and ethically acceptable amount of evidence of his intent to commit the crime could be gathered him and stopped him from ever being able to travel back in time.
Click to expand...
Firstly, I appreciate that you appreciate that I am taking the issue to a ridiculous extreme. Secondly I appreciate that you said 'maybe'; however, I would opine that your 'maybe' is misplaced. Maybe there are no 45th century temporal continuity police. Maybe they accept bribes from butthole super villains. Maybe they are allied with him because they dislike gypsies and the Dutch. What I meant to emphasize in my ridiculous scenario is that there's no reason to think the future (if our species even has one) as a place were people are moral and good just because they have advanced technology. We ourselves live in a society that has relativity advanced technology compared to people in earlier times. Has it made our society more moral? The least bit wiser or benevolent? In your ridiculous scenario the future is a constant battle of time cops and 'time bandits' (great film). All very entertaining, and even almost possible, but if we get out that dull Occam's razor we sometimes use here on the forum, we know that it's simpler to surmise there isn't and never will be such a thing as time travel.

And while I am talking about the moral implications of this sci-fi favorite, maybe the most edifying and intelligent time travel stories are the ones in which the time machine's inventor dismantles his contraption and burns his notes. So if any one is going to appeal in the good and wise heart of civilized humanity, I'd say all righty then - that's one more reason time travel will never be. Even if it were technically possible, people would realize it's mucho bad mojo and lock it away somewhere.
 
Beer w/Straw said:
Well, we still have no evidence that there are other intelligent civilizations in the universe. Would you propose that SETI is a waste of time?
Click to expand...
I think you've strayed from the topic, but briefly, no it's not a waste (Personally, I find their work intriguing, but I don't 'hope' they find something soon simply because I realize that my hoping or not isn't going to change a thing). However, it may be unwise to be summoning this particular genie. Steven Hawking and L. Ron Hubbard, among others, consider it foolish to be letting advanced civilizations know of our whereabouts and our resources.

As in my post just above, why this assumption that advanced technological ability is hand in glove with moral goodness? That's quite an assumption really. Or is someone going to say there is nothing in modern physics or GR to forbid the possibility? :biggrin:
 
Landau Roof said:
That's quite an assumption really. Or is someone going to say there is nothing in modern physics or GR to forbid the possibility? :biggrin:
Click to expand...


The childish frivolous nature of your posts, do nothing to get away from that fact...well two facts in fact....:)
Time travel is not forbidden by the laws of physics and GR....
And any sufficiently advanced civilisation could achieve it.
 
No. I didn't stray off topic. Why do you assume that people aren't already aware of the weird paradoxes involved in time travel? You're just lambasting them as if they were only starry-eyed day dreamers. Hence, I asked if that opinion would be the same for people that think alien life could exist. They would have called you mad if you talked about aliens in the Middle Ages Are you a narrow minded hypocrite?

On the quantum mechanical scale, our universe is a total head spin itself, or do you deny it?


Landau Roof said:
As in my post just above, why this assumption that advanced technological ability is hand in glove with moral goodness?
Click to expand...
I didn't say it did.
 
Last edited:
Landau Roof said:
but if we get out that dull Occam's razor we sometimes use here on the forum, we know that it's simpler to surmise there isn't and never will be such a thing as time travel
Click to expand...
Of course; and it is simpler to surmise that we will never get people to Mars, since that will be a complex effort, and a simple view of that effort makes it appear way too hard. That we will never cure cancer, since that would take a lot of work. That we will never build efficient desalinators. Etc etc.

However, the smart money is on us accomplishing technically possible but challenging goals.
 
billvon said:
However, the smart money is on us accomplishing technically possible but challenging goals.
Click to expand...


A great war time PM once was quoted as saying.....
“A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty.”
Winston S. Churchill:

Of course he had no way of knowing about the future, and forums such as this that would be a magnet in attracting people that had no other methodology in spewing their nonsense to the world.
 
Beer w/Straw said:
No. I didn't stray off topic. Why do you assume that people aren't already aware of the weird paradoxes involved in time travel? You're just lambasting them as if they were only starry-eyed day dreamers. Hence, I asked if that opinion would be the same for people that think alien life could exist. They would have called you mad if you talked about aliens in the Middle Ages Are you a narrow minded hypocrite?
Click to expand...
I don't see much of a connection, and I've given my view. If you've followed this conversation from the beginning you'd see that even those who started out as starry-eyed day dreamers have either admitted it'll be a long haul to achieve time travel and it remains mere fiction.
Beer w/Straw said:
On the quantum mechanical scale, our universe is a total head spin itself, or do you deny it?
Click to expand...
Please explain yourself better. Elaborate.
As in my post just above, why this assumption that advanced technological ability is hand in glove with moral goodness?
Click to expand...
Beer w/Straw said:
I didn't say it did.
Click to expand...
No, you didn't. I was addressing the general tendency on this forum of many to see science as a new faith. Somehow smaller computers, Mars probes and more wi-fi hot spots translates into a future high-tech utopia to them. I blame the sci-fantasy show Star Trek.
 
Landau Roof said:
No, you didn't. I was addressing the general tendency on this forum of many to see science as a new faith. Somehow smaller computers, Mars probes and more wi-fi hot spots translates into a future high-tech utopia to them. I blame the sci-fantasy show Star Trek.
Click to expand...

I think this is a perception that exists only in your head - unless you want to get into a metaphysical discussion in another thread about why improving technology is, or should be, expected to lead to an increasingly civilized society.

My point was that for every far-fetched absurd scenario you can dream up, there is an equally far-fetched absurd scenario that could explain why time travelers don't interfere with history if time travel was possible.

The corollary of this is that the whole discussion could be regarded as being virtually meaningless, and if discussing the objection is an exercise in meaningless speculation, how can the initial objection be regarded as anything other than meaningless speculation.

Especially when perfectly good physical reasons (for example those outlined by BIllvon) exist as to why we might not expect to see time travelers now even if time travel is possible.
 
Has anyone here read "End of Eternity" by Isaac Asimov? We probably wouldn't know if time is being interfered with...
 
You must log in or register to reply here.
Back
Top