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Five minute snippet of Discovery Science channel show on a time machine. Pretty cool, but the writing suffers from the misuse of the phrase "begs the question" as in "This begs the question of what happens when the machine is first turned on." Which should be, "This raises the question of what happens when the machine is first turned on." It might be pedantic of me to point that out, but hey, those shows are supposed to educate not stupify.

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Original post by LessBread ">linkified Five minute snippet of Discovery Science channel show on a time machine. Pretty cool, but the writing suffers from the misuse of the phrase "begs the question" as in "This begs the question of what happens when the machine is first turned on." Which should be, "This raises the question of what happens when the machine is first turned on." It might be pedantic of me to point that out, but hey, those shows are supposed to educate not stupify.

I really wish I'd never found out that "begs the question" doesn't mean what it seems to mean, because now I get annoyed whenever I see it misused, which is almost always. [flaming]

Sorry. Be certain then, not to ever read this: George Orwell, "Politics and the English Language," 1946 [grin]

I don't agree with any of this. I'm not qualified to disagree since I have no credentials but I'll supply my own justification and hope that's enough.

1. Time is not a constant in the universe. The faster you travel, the slower time proceeds. (so its said anyways)
2. Time and gravity are closely related to each other. A person passing into the event horizon of a black hole would experience a time shift (slowing down) compared to a person outside the influence of the black hole.

What I made up and believe:
3. The methods we humans use to measure time creates an illusion regarding the nature of time. We break time into small increments such as seconds, or even smaller, into milliseconds. You would then reason that you could break down time into even smaller increments then a millisecond (provided you have instruments capable of measuring it). Unlike matter, there is not a "smallest size" for time. There is not a window of time which spans between one instant to another.

The nature of time is such that there is an infinite number of continuously happening instances happening in an infinitely small window...at a non-constant rate.
I shouldn't use the word "instances" since it creates the same misconception of time I'm arguing against. Time "flows", we just create the moments in time which it flows between and define them as milliseconds, seconds, minutes, hours, days, weeks, etc.

It may be easier to explain the nature of time using the concept of the limit in calculus.

another made up belief:
4. Time has always existed and always will exist. Stephen Hawking says that time didn't exist before the Big Bang, but I disagree: The big bang couldn't exist without time. (assuming the big bang existed)



So, here's what I'm wondering:
If light gets bent when it goes through a strong gravitational field such as the Sun, is it being bent due to the gravitational field or the warp in the space-time continuum? I really don't know. :(
If the space-time continuum is proportionate to the gravitational field, then you'd really need a strong force of gravity to warp time. How anything could survive something like that is beyond me.

How the heck does this video justify using light as a means for time travel??? If E=MC^2, then pure energy must have gravity; Yet, the energy released in atomic bombs from a teeny bit of mass is extremely high, so the gravitational energy would be equivalent to the few grams of the mass of the uranium. To have gravity strong enough to bend light, you'd need a laser beam with more energy then several hundred million atomic bombs. By the explanation in this video, you'd need hundreds of such laser beams. How could you sustainably power such laser beams, and how would you absorb the energy from such a powerful laser? That's like...a death star beam!!! I don't understand the video so it must be false, impossible or wishful thinking.

Time travel: Logically possible? but technologically impossible.
(Logically possible: We don't understand the nature of time or gravity yet to make a logical assessment of whether time travel is possible or not)

[wow] slayemin, that didn't make any sense.

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Original post by twix [wow] slayemin, that didn't make any sense.

Hmm, you're right. It makes perfect sense to me but I can see how it makes no sense to other people. Arg, my mistake. I'll do my best to clarify.

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I don't agree with any of this. I'm not qualified to disagree since I have no credentials but I'll supply my own justification and hope that's enough.

I don't think I'm smart enough to make good critiques on the video but I'll try.

First, the idea of a Time Machine sounds crazy. It's something that goes back or forwards in time. The whole idea of a time machine relies on our idea of what time really is: past, present and future. But we really don't know what time is if we think its just "a few hours ago" or "a few days ago". I try to define time without using time to define itself. If I can define the nature of time, then this idea of a time machine becomes even more crazy.

These explanations towards the nature of time were from my astronomy textbook.

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1. Time is not a constant in the universe. The faster you travel, the slower time proceeds. (so its said anyways) 2. Time and gravity are closely related to each other. A person passing into the event horizon of a black hole would experience a time shift (slowing down) compared to a person outside the influence of the black hole.

Now, I have to be honest when I say that I'm making this stuff up. It makes sense to me and someone else has probably already thought of it and explained it better then I have. I regret not researching for a better explanation; it would have been the scholarly thing to do.

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What I made up and believe: 3. The methods we humans use to measure time creates an illusion regarding the nature of time. We break time into small increments such as seconds, or even smaller, into milliseconds. You would then reason that you could break down time into even smaller increments then a millisecond (provided you have instruments capable of measuring it). Unlike matter, there is not a "smallest size" for time. There is not a window of time which spans between one instant to another. The nature of time is such that there is an infinite number of continuously happening instances happening in an infinitely small window...at a non-constant rate. I shouldn't use the word "instances" since it creates the same misconception of time I'm arguing against. Time "flows", we just create the moments in time which it flows between and define them as milliseconds, seconds, minutes, hours, days, weeks, etc.

okay uhm, how to explain this...

Time is like this: --------------------------------------------------
A straight, flowing line without segments. It can't be broken down to a "smallest" segment because time is infinitely small and connected.

We make time look like this: ---|---|---|---|---|---|---|---|---|---
Each "|" is a marker which ticks off a portion of time. Maybe a second, millisecond, minute, etc.

Now, I have to account for time not being constant. It changes based on gravity and speed of the observer. So, Time can look like this:
------|------|------|------|------|------|------
or like this:
-|-|-|-|-|-|-
and they can both be the same measurement of time; seconds, milliseconds, minutes, etc.

Anyways, how we measure time creates an illusion that time is segmented when its really not. We create the segments. I may not actually understand time, but I wonder... if the representation of time is an invention, then is a time machine impossible since its relying on a model of how we see time? I get lost when I think too hard on hypotheticals like this.

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It may be easier to explain the nature of time using the concept of the limit in calculus. another made up belief: 4. Time has always existed and always will exist. Stephen Hawking says that time didn't exist before the Big Bang, but I disagree: The big bang couldn't exist without time. (assuming the big bang existed)

There was a question: "What was time like before the big bang?" and Stephen Hawking replied that time didn't exist before the big bang. The big bang was the beginning of time. He made an analogy: looking for time before the big bang is like trying to go north of the north pole. I don't agree on this; the nature of time seems to make it infinite and outside the context of our universe.
Interestingly, if the big bang did happen and if time began at the same instant as the big bang, then the big bang did not happen instantaneously like scientists seem to claim. Logically, if the big bang has all matter in the universe and all matter has gravity, and large amounts of gravity cause time to slow down, then the big bang did not happen instantaneously and its actually impossible to say how long it took. We have no relative measure of time to measure the big bang against.

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So, here's what I'm wondering: If light gets bent when it goes through a strong gravitational field such as the Sun, is it being bent due to the gravitational field or the warp in the space-time continuum? I really don't know. :( If the space-time continuum is proportionate to the gravitational field, then you'd really need a strong force of gravity to warp time. How anything could survive something like that is beyond me.

The beginning part of the video was referencing black holes and how you could possibly use a black hole to alter your time. We don't know for sure if thats what really happens around a black hole; we have no way of finding out. We can observe gravity bending light by seeing stars behind the sun. I'm speculating that the same gravity that bends light is probably the same force that bends time and perhaps the amount that time is bent is proportionate to the gravitational strength of a massive object. The sun would slow down time only slightly while a black hole would have a bigger impact on time.

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How the heck does this video justify using light as a means for time travel??? If E=MC^2, then pure energy must have gravity; Yet, the energy released in atomic bombs from a teeny bit of mass is extremely high, so the gravitational energy would be equivalent to the few grams of the mass of the uranium. To have gravity strong enough to bend light, you'd need a laser beam with more energy then several hundred million atomic bombs. By the explanation in this video, you'd need hundreds of such laser beams. How could you sustainably power such laser beams, and how would you absorb the energy from such a powerful laser? That's like...a death star beam!!! I don't understand the video so it must be false, impossible or wishful thinking.

Now this is the main reason I'm so skeptical about using light as a time travel method. The video didn't give a technical explanation for how light would play a role in time travel; it just mentioned that we have really strong lasers that can burn really hot and made some pretty graphics with laser beams and a hypothetical particle.

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Time travel: Logically possible? but technologically impossible. (Logically possible: We don't understand the nature of time or gravity yet to make a logical assessment of whether time travel is possible or not)

In philosophy, there are three categories of possibility/impossibility moving down in a hierarchy of sorts
Logical possibility
Physical possibility
Technological possibility

"Pigs can fly"
Logically, its possible. Physically, pigs can't fly.

"Man can fly"
Logically, its possible. Physically, we can fly. Technologically, it wasn't possible until we invented flying craft (balloons, airplanes, blimps, helicopters, gliders, rockets, etc)

"We can send stuff back in time"
Logically, we don't know if its possible. You got the big paradox of what that could mean if time travel was possible. (Can you go back in time and kill your father before you were born? etc) Physically and technologically, its currently impossible and may never be possible.

"We can get stuff from our future selves"
The video tries to explain this, but its a logical impossibility because it would create the same paradox as if we were sending stuff back in time. If we could communicate with our future selves, the future us would send the present us technology and that would change our future and the future's present. They could send us quantum computing technology. Suddenly, we know how to make quantum computers. Then we've got say, 100 years to improve quantum computers and our future selves send back 100 years of improvements to the technology. It can happen infinitely. Ethically, thats probably like giving cavemen nukes.
Logically, that would mean that the present time is a window of time in a parallel universe with many parallel universes. The future is fated to happen. I don't believe time has a future, only we have the capacity to predict a future which makes us think time goes forward beyond the present.

I hope this makes some sense... let me know if I am still unclear.

I think time is just a name human beings created to understand the world around them.Time,motion and change all go relative together.Think of it,if everything in the universe stops then what we call time does not exists.You won't age you wont die etc.
Human mind understands time as the "passage" between two events.And calls it time to organize everything.I guess our brains are created in a linear fashion so we can't understand that in fact time does not exists its just universe is changing constantly.So I don't believe going back forth in time etc. can be possible because the past and the future does not exists :)We only got present which is always changing.

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Original post by Black Knight I think time is just a name human beings created to understand the world around them.Time,motion and change all go relative together.Think of it,if everything in the universe stops then what we call time does not exists.You won't age you wont die etc. Human mind understands time as the "passage" between two events.And calls it time to organize everything.I guess our brains are created in a linear fashion so we can't understand that in fact time does not exists its just universe is changing constantly.So I don't believe going back forth in time etc. can be possible because the past and the future does not exists :)We only got present which is always changing.

I think you almost got it. Time has existed long before humans existed, how time is measured is a human invention.

I also think time continues regardless of whatever events happen in the universe. We wouldn't be able to observe the progression of time if all clocks, motion and universal forces were suspended, but time would continue since it is outside the universe we're in.

Here's an interesting scenario for fun :)
Judge: "You were clocked at 100 miles per hour!"
Me: "But your honor, how can you be sure? If speed is a measure of distance over time, and the nature of time is unknown, can we even use speed?"
Judge: "What is this nonsense?"
Me: "I shouldn't get this speeding ticket because speed requires time to be constant. Time is not constant since the space-time continuum is warped around high gravitational fields such as a black hole or the sun."
Judge: "So what are you saying son? That a black hole popped up and made time go faster right as you were being clocked by a police officer with a radar gun?"
Me: "No sir, all I'm saying is that speed relies on distance and time. Distance is a concretely knowable subject while time is still mysterious."
Judge: "But not mysterious enough on earth. Here's your fine! Pay at the door."
---whoo, its 3:30am...time for bed...

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Original post by slayemin Unlike matter, there is not a "smallest size" for time. There is not a window of time which spans between one instant to another.

While quantum time doesn't fit into current established theories, it is a possibility.

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Original post by slayemin I shouldn't use the word "instances" since it creates the same misconception of time I'm arguing against. Time "flows", we just create the moments in time which it flows between and define them as milliseconds, seconds, minutes, hours, days, weeks, etc.

Time doesn't "flow" any more than space "flows". Our perception of the passage of time is due to entropy.

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Original post by slayemin If light gets bent when it goes through a strong gravitational field such as the Sun, is it being bent due to the gravitational field or the warp in the space-time continuum? I really don't know.

Both, since gravity is the curvature of space-time (General Theory of Relativity).

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Original post by slayemin How the heck does this video justify using light as a means for time travel??? ... To have gravity strong enough to bend light, you'd need a laser beam with more energy then several hundred million atomic bombs.

Keep in mind that the experiment is done on sub-atomic particles.

Time travel in the classic sense has no place in rational theory, but temporal distortion does exist on the quantum level, and more importantly it can be controlled.

Academician Prokhor Zakharov
"For I Have Tasted The Fruit"

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Original post by JohnBolton Our perception of the passage of time is due to entropy.

Care to expand?

An interesting detail that was left out of the video is that if someone in the future sent a particle back in time to be observed by a modern day observer, the observer would not see the particle, but the particle's antiparticle counterpart. That is, if the person in the future sent an electron back in time, it would appear to the observer in the past (with respect to the instigator's time) as a positron moving forward through time. Or if the future lab worker sent a positron into the past, then the past observer would see an electron moving forward through time.

What happens when you see a message coming through the machine, and then you prevent the people in the future from sending that message (eg by turning off the machine and destroying the plans)? Then in the real future the message was never sent and what you received was thus not from the real future. Is this some kind of paradox? If this thing is real, what really happens if you prevent the people in the future from sending in what you received? Is it impossible to prevent that? Or are there "alternate realities"?

[Edited by - Lode on June 23, 2007 6:06:18 AM]

I just watched the video and maybe I don't know enough about this stuff I don't see nearly enough proof of how this would work. I guess I understand the concept of spinning something to/beyond C sending it back in time, but I don't see the jump between that and shooting particles between a bunch of lasers sending it back in time.

Not to mention the fact that even if you can coax particles beyond C and send them back in time you will be sending them backwards in time but to the same location. In other words we would never get the message because of the movement of the Earth, Sun, Galaxy, Universe(?). The particles would appear in our time at some empty point in space that the Earth occupied when the particles were sent back, not very useful.

I haven't read the white papers on it, so perhaps they provide an answer, but I see a problem that would appear to make such a machine highly impractical, if not impossible. The problem being, if a person at space-time coordinates (x₁,y₁,z₁,t₁) sends a PCM encoded stream of electrons back in time to (x₀,y₀,z₀,t₀), where of course t₀ < t₁, how would the observer in the past arrange to be at those coordinates when the Earth, indeed the solar system, and galaxy itself are in constant motion with respect to distant galaxies? It would seem the person in the past would need information from the future just in order to know where and when to look to see the message from the future, which is obviously paradoxical. I suppose the person looking for a message from the future could keep meticulous records of when and where he was looking for a message and then the person in the future could send the message back to those coordinates but then the person in the past would have already made a note that the message was or was not received. So the person in the future would need to find in the notes the time and place the person in the past says the message was received. But then, what if the person in the future decides not to send that message? Do we then compel a person even further in the future to send the message back? What if the person in the past left explicit instructions to not have it sent back and all abide?

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Original post by Mastaba An interesting detail that was left out of the video is that if someone in the future sent a particle back in time to be observed by a modern day observer, the observer would not see the particle, but the particle's antiparticle counterpart. That is, if the person in the future sent an electron back in time, it would appear to the observer in the past (with respect to the instigator's time) as a positron moving forward through time. Or if the future lab worker sent a positron into the past, then the past observer would see an electron moving forward through time.

a) What is the science behind that?

b) So if I sent myself through a time machine then my anti-matter self would appear in the past?

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a) What is the science behind that?

CPT symmetry.

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b) So if I sent myself through a time machine then my anti-matter self would appear in the past?

Indeed. So be sure to not touch or be touched!

If you are interested on this particular time machine, here are some interesting resources:

http://www.physicsforums.com/showthread.php?t=42834
http://www.physicsforums.com/showthread.php?t=147946
http://arxiv.org/abs/gr-qc/0410078
http://en.wikipedia.org/wiki/Ronald_Mallett#Objections

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Original post by Alpha_ProgDes Quote: Original post by Mastaba An interesting detail that was left out of the video is that if someone in the future sent a particle back in time to be observed by a modern day observer, the observer would not see the particle, but the particle's antiparticle counterpart. That is, if the person in the future sent an electron back in time, it would appear to the observer in the past (with respect to the instigator's time) as a positron moving forward through time. Or if the future lab worker sent a positron into the past, then the past observer would see an electron moving forward through time. a) What is the science behind that? b) So if I sent myself through a time machine then my anti-matter self would appear in the past?

It's like pressing the rewind button on the electron. A reversal of spin direction would (have to) occur.

I do not have the equipment to verify the claims of the paper. :)

Personally, I think that even if you change the spin direction of something, it is still travelling into the future. It's just different.

Anyone seen those videos on String Theory? Now THERE’S a mind bender!