Do you believe time travel is possible?

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PinzaC55 said:
The Law Of Identity says that each "thing" is unique. So if you bring a vase back 30 years to a time when it already existed, not only is it the same collection of atoms in the same shape, each individual atom is the same one which existed 30 years ago. That's logically impossible unless somebody proves otherwise. I don't pretend to know anything about quantum physics and I doubt anybody other than a number of scientists do either. I would be interested to know what somebody like Lawrence Krauss would say.
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What about the ship of Theseus? That might work. (Also that broom from OFAH)
 
niceonemarra said:
I was just reading some of his thoughts on it and he mentioned about how a black hole is a time machine.
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Yeah, not really a time machine as such. It's just that time would pass more slowly for them than the people back home, so when they got back everything would be "a little bit into the future". It's just the relativity thing again but instead of it being near light speed slowing down time, it's being close to a large gravitational source that's doing it. It's not like they could travel "back" to their own time afterwards.

Stephen Hawking’s ‘black hole time machine’ proposal to NASA revealed
 
fyl2u said:
Yeah, not really a time machine as such. It's just that time would pass more slowly for them than the people back home, so when they got back everything would be "a little bit into the future". It's just the relativity thing again but instead of it being near light speed slowing down time, it's being close to a large gravitational source that's doing it. It's not like they could travel "back" to their own time afterwards.

Stephen Hawking’s ‘black hole time machine’ proposal to NASA revealed
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Are we not splitting hairs a bit thinking that relativity isn't time travel? To be propelled a year into the future is time travel regardless of how it happened innit?
 
PinzaC55 said:
The Law Of Identity says that each "thing" is unique. So if you bring a vase back 30 years to a time when it already existed, not only is it the same collection of atoms in the same shape, each individual atom is the same one which existed 30 years ago. That's logically impossible unless somebody proves otherwise. I don't pretend to know anything about quantum physics and I doubt anybody other than a number of scientists do either. I would be interested to know what somebody like Lawrence Krauss would say.
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I'm not sure that applies to time travel, as the new atoms are technically not the same particles. They have a different "timestamp" essentially, so they're a different particle.

Imagined quantised time, with every 3d (or multidimensional) position of every particle appearing in time-snapshots that when combined form a complete 4D (or multiD+t) image of the entire universe from the beginning to the end as a kind of 3D-printed solid object. A particle taken from later in the timeline and inserted earlier in the timeline would essentially be a different particle to the one representing the same particle further back in time. The fact that one of the particles of the "back in time" position later becomes a particle that travels back in time to the same point in time is irrelevant. The timeline of that individual particle is complete up to the point the particle goes back in time, after which it no longer exists in its "planned" (for want of a better phrase spur of the moment) existence, whereas back where it arrives, it is essentially a new particle that has a complete timeline for the rest of time after that moment. For a time, two versions of that particle exist but because of the t element, they're actually essentially different particles for the time they both exist in the same "frames".

Incidentally, in quantum physics it is quite a common thing for something to exist in more than one place at the same time. It's called Superposition.
 
niceonemarra said:
Are we not splitting hairs a bit thinking that relativity isn't time travel? To be propelled a year into the future is time travel regardless of how it happened innit?
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You're not really being propelled into the future, time is just passing more slowly for you than people further away from the gravity source.

It's exactly the same as how whenever you get on a plane you're actually travelling a fraction of a microsecond into the future compared with the folks you left at home. A black hole just increases the effect because of the increased gravity. It's no more "time travel" than going to sleep for eight hours allows you to wake up eight hours in the future compared to when you went to sleep.

For me, a "time machine" has to allow travelling back in time, or can send you to a specific point in the future and then allow you to return home to your original time period.

Just "travelling into the future" using these relativity cheats isn't really time travel in my book, any more than cryonic freezing would be "time travel" despite the fact you go to sleep now and wake up at some point in the future (in theory). You've never "ceased to exist" in the present to get where you're going.
 
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TwasOnTheFifthOfMay said:
But subatomic particles are coming into and out of existence all the time, so they might be free to time travel. And of course, the photon that's re-emitted isn't the same photon that was absorbed, and when a neutron decays you get a whole new set of particles again.

I vaguely remember reading about one of the bonkers quantum effect experiments that seemed to show a detector affecting events earlier in the experiment depending on whether it was turned on or off. Reversing cause and effect is the essence of time travel.
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I think I see what you mean but this stuff is so deep I'm probably way off.

So in a quantum vacuum virtual particles and their opposites are coming in and out of existence all the time? Hypothetically tachyons are superluminal and travel back in time according to relativity? But that may be after the spacetime continuum has emerged with a direction to time? So in the quantum vacuum there is no direction to time and therefore forwards and backwards are possible. What time seems to indicate is a separation between cause and effect but in a quantum vacuum cause and effect can be reversed?

Is the bonkers experiment you refer to, wave function collapse due to the act of observing even with a machine?
fyl2u said:
You're not really being propelled into the future, time is just passing more slowly for you than people further away from the gravity source.

It's exactly the same as how whenever you get on a plane you're actually travelling a fraction of a microsecond into the future compared with the folks you left at home. A black hole just increases the effect because of the increased gravity. It's no more "time travel" than going to sleep for eight hours allows you to wake up eight hours in the future compared to when you went to sleep.

For me, a "time machine" has to allow travelling back in time, or can send you to a specific point in the future and then allow you to return home to your original time period.

Just "travelling into the future" using these relativity cheats isn't really time travel in my book, any more than cryonic freezing would be "time travel" despite the fact you go to sleep now and wake up at some point in the future (in theory). You've never "ceased to exist" in the present to get where you're going.
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Then again at the same scale everything we look at is dependent on the speed of light so we are forever observing the past even in our everyday life.
 
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TwasOnTheFifthOfMay said:
But subatomic particles are coming into and out of existence all the time, so they might be free to time travel. And of course, the photon that's re-emitted isn't the same photon that was absorbed, and when a neutron decays you get a whole new set of particles again.

I vaguely remember reading about one of the bonkers quantum effect experiments that seemed to show a detector affecting events earlier in the experiment depending on whether it was turned on or off. Reversing cause and effect is the essence of time travel.
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The "retrocausality experiment" that was designed to split a photon into two quantum-entangled versions of the same photon sent simulataneously down two lengths of fibreoptic cable, one much longer than the other to create a time-delay on only one of the entangled pair. The idea was that by affecting the later-arriving version of the pair, it should affect the one that already arrived due to Einstein's "spooky action at a distance" theory. Essentially, the cause would happen after the effect of that cause. Hence retro_causality.

I was a big fan of the theory. Unfortunately as far as I remember the experiment didn't work.

I still call myself "Retrocausality" as my username when I'm gaming.

(I'm so fast, you're already dead before I even pull the trigger ;) )

Mercia Blackcat said:
I think I see what you mean but this stuff is so deep I'm probably way off.

So in a quantum vacuum virtual particles and their opposites are coming in and out of existence all the time? Hypothetically tachyons are superluminal and travel back in time according to relativity? But that may be after the spacetime continuum has emerged with a direction to time? So in the quantum vacuum there is no direction to time and therefore forwards and backwards are possible. What time seems to indicate is a separation between cause and effect but in a quantum vacuum cause and effect can be reversed?

Is the bonkers experiment you refer to, wave function collapse due to the act of observing even with a machine?


Then again at the same scale everything we look at is dependent on the speed of light so we are forever observing the past even in our everyday life.
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Tachyons have never been proven to exist, and even the maths describing possibilities of them has been shown not to work.

Yes, the technique behind the retrocausality experiment involved wave collapse due to observation on the latter-arriving photon of the entangled pair, with the hoped-for reaction being the original photon's wave function collapsing "before" the affected half of the entangled pair had been observed.

Your "nature of the direction of time within zero point space" question is a little beyond my understanding for me to answer for certain with confidence and clarity, but certainly at the quantum level things are "a bit weird" compared with the macroscopic level, with things coming in and out of existence and sometimes existing in more than one place at once.

i don't think it's quite the case of "time not existing" but more that it doesn't necessarily work in a linear fashion. I could be wrong though.
 
fyl2u said:
The "retrocausality experiment" that was designed to split a photon into two quantum-entangled versions of the same photon sent simulataneously down two lengths of fibreoptic cable, one much longer than the other to create a time-delay on only one of the entangled pair. The idea was that by affecting the later-arriving version of the pair, it should affect the one that already arrived due to Einstein's "spooky action at a distance" theory. Essentially, the cause would happen after the effect of that cause. Hence retro_causality.

I was a big fan of the theory. Unfortunately as far as I remember the experiment didn't work.

I still call myself "Retrocausality" as my username when I'm gaming.

(I'm so fast, you're already dead before I even pull the trigger ;) )



Tachyons have never been proven to exist, and even the maths describing possibilities of them has been shown not to work.

Yes, the technique behind the retrocausality experiment involved wave collapse due to observation on the latter-arriving photon of the entangled pair, with the hoped-for reaction being the original photon's wave function collapsing "before" the affected half of the entangled pair had been observed.

Your "nature of the direction of time within zero point space" question is a little beyond my understanding for me to answer for certain with confidence and clarity, but certainly at the quantum level things are "a bit weird" compared with the macroscopic level, with things coming in and out of existence and sometimes existing in more than one place at once.

i don't think it's quite the case of "time not existing" but more that it doesn't necessarily work in a linear fashion. I could be wrong though.
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John Wheeler:

"Of all obstacles to a thoroughly penetrating account of existence, none looms up more dismayingly than “time.” Explain time? Not without explaining existence. Explain existence? Not without explaining time. To uncover the deep and hidden connection between time and existence, to close on itself our quartet of questions, is a task for the future. "
 
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Havent read the whole thread, but, I dont believe they are or will be.

We've never seen anyone from the future yet in our times, so suggests to me there wont ever be.

Surely if they are to be invented in the future then someone would come back to prevent 9/11 or some other atrocities.
 
Mercia Blackcat said:
John Wheeler:

"Of all obstacles to a thoroughly penetrating account of existence, none looms up more dismayingly than “time.” Explain time? Not without explaining existence. Explain existence? Not without explaining time. To uncover the deep and hidden connection between time and existence, to close on itself our quartet of questions, is a task for the future. "
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Sounds a bit flowery for a physicist. Was this towards the end of his life? ;)
Malloy said:
Havent read the whole thread, but, I dont believe they are or will be.

We've never seen anyone from the future yet in our times, so suggests to me there wont ever be.

Surely if they are to be invented in the future then someone would come back to prevent 9/11 or some other atrocities.
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Maybe they came back in time to cause 9/11?

Maybe someone on one of the planes was going to be the next Hitler?
 
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I've heard a lot of wacky 9/11 theories but this 'time travellers did it' is a new one.
 
fyl2u said:
Sounds a bit flowery for a physicist. Was this towards the end of his life? ;)
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From the mid 1980s I think. An interesting quote though from the man who coined the terms black hole and wormhole.
fyl2u said:
You'd think they would have aimed it for Trump's house if that was the case. Unless they were Russian, Indian or Chinese time travellers. That would make more sense.
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It has been claimed that you only need a reading age of 6 to be able to read the Sun newspaper. I think to Trump even the Sun may be a bit intellectual judging from the way he talks so is Trump an example of internal forward movement through time. He jumps from a 5 years old's mind into an adult body? Reminds me of a film with Tom Hanks?
 
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Mercia Blackcat said:
From the mid 1980s I think. An interesting quote though from the man who coined the terms black hole and wormhole.


It has been claimed that you only need a reading age of 6 to be able to read the Sun newspaper. I think to Trump even the Sun may be a bit intellectual judging from the way he talks so is Trump an example of internal forward movement through time. He jumps from a 5 years old's mind into an adult body? Reminds me of a film with Tom Hanks?
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Captain Phillips?
 
Could some of the ufo's that are seen be time machines?

Im sure I rad recently that when Columbus crossed the atlantic he saw lights in the sea as well as Apollo11 supposedly watched on the moon.

Im sure people in the future would like to come back, if they could, and watch history being made.
 

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