The quantum physics discussion in my Holiday Dinner Table thread got me thinking about time and space, what is bendable, what isn't, whether General Relativity is a viable theory and so forth, and naturally I started considering the possibility of time travel. Here's how I know it is impossible:
Time doesn't exist. It is a manifestation of the human imagination. Things change; the world changes, we change and everything seems to be in flux somehow. Even if an object takes millenia to destruct and end, it inevitably does, similar to entropy, I suppose, in the sense that there is a systematic degradation involved in all things. Nevertheless, my point is that things are always changing, and of course distances between objects exist, but time itself does not exist. It is merely a subjective measurement system.
Prove me wrong if you must!
banned: You could speak of time as being 0.99991% on the surface of the earth, due to gravity, whereas the satellites in orbit are experiencing 0.9992% time passage. No you can't. In SR, there is no proper frame. You can choose a proper frame but it's only valid for a particular problem.
You could speak of time as being 0.99991% on the surface of the earth, due to gravity, whereas the satellites in orbit are experiencing 0.9992% time passage.
No you can't. In SR, there is no proper frame. You can choose a proper frame but it's only valid for a particular problem.
I'm not saying it's a proper frame, I'm simply taking a theoretical zero-gravity tensor area of space and saying that here, where there is absolute-zero gravity (not achievable in actuality), if we look at earth orbit vs earth surface, that statement I made would be understandable (I admit the % figures are completely made up for example's sake).
banned: Like if moving faster can actually slow your rate of time passage compared to a non-moving thing, like the planet, how does the universe know that you're moving away from the planet and not that the planet is moving away from you? It doesn't. That's the point of SR, there is no proper frame. When you are in an accelerating frame things become different, because you can tell whether one frame is accelerating relative to the other (this is also GR and requires a more complex derivation of space-time geometry that I haven't fully learned). BTW, the answer to this problem is that both the observer in the "moving" frame and the observer on the "non-moving" frame see each others clocks going slower.
Like if moving faster can actually slow your rate of time passage compared to a non-moving thing, like the planet, how does the universe know that you're moving away from the planet and not that the planet is moving away from you?
It doesn't. That's the point of SR, there is no proper frame. When you are in an accelerating frame things become different, because you can tell whether one frame is accelerating relative to the other (this is also GR and requires a more complex derivation of space-time geometry that I haven't fully learned). BTW, the answer to this problem is that both the observer in the "moving" frame and the observer on the "non-moving" frame see each others clocks going slower.
Really? Then what of the statements that the moon astronauts have "gained seconds on their life" due to the acceleration they've experienced, compared to the rest of us.
banned: It would have to be tied either to changes in inertia, which I think is increasingly possible, or there is a universal reference point of zero-speed, which physicists strongly doubt. Both are incorrect. Inertia is a frame invariant (othewise energy and momentum are not conserved in frames). And there is no such concept as an invariant zero-speed, because speed is a relationship and must necessarily be measured relative to other things.
It would have to be tied either to changes in inertia, which I think is increasingly possible, or there is a universal reference point of zero-speed, which physicists strongly doubt.
Both are incorrect. Inertia is a frame invariant (othewise energy and momentum are not conserved in frames). And there is no such concept as an invariant zero-speed, because speed is a relationship and must necessarily be measured relative to other things.
Sure, makes sense.
Time certainly exists. In fact, the universe is 4-dimensional and the past and future are just as real as the present, according to the Rietdijk-Putnam argument: http://en.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_argument
There are only two ways to argue against this that I know of. One is a kind of solipsism where you maintain that only points infinitesimally distant from you in space and time (i.e. a single point at your present location) are real; any other part of the universe is not real. The other approach is to argue against special relativity itself (you get extra points if you post using a mobile device with a GPS feature that depends on general relativistic corrections to operate properly).
AFAIK, nothing in science definitively rules out time travel. Often an electron will emit a photon and then travel backward in time, which we perceive as a positron. If a subatomic particle can undergo a deflection in its world line and travel back in time, why can't a human being? I think the main impediment is thermodynamic considerations, related to the boundary conditions of the universe. Also, GR allows metrics with time loops. There may be no macroscopic time loops in our past but it's possible we could create them in the future.
Finally, this theoretical means of transportation based on GR could someday allow superluminal travel, which is to say travel into the past with respect to some observers, http://en.wikipedia.org/wiki/Alcubierre_drive . Apparently NASA is researching this http://techland.time.com/2012/09/19/nasa-actually-working-on-faster-than-light-warp-drive/
Yes, but mathematical derivations of actually possible time-travel or faster-than-light travel rely on the ability to create negative gravity.
Which we have no reason right now to think will ever be possible.
"negative gravity... Which we have no reason right now to think will ever be possible."
But it is possible. See http://en.wikipedia.org/wiki/Casmir_effect
"Morris, Thorne and Yurtsever pointed out that the quantum mechanics of the Casimir effect can be used to produce a locally mass-negative region of space-time,[29] and suggested that negative effect could be used to stabilize a wormhole to allow faster than light travel" - http://en.wikipedia.org/wiki/Casmir_effect"
The only thing I see from "science" forbidding time travel is this conjecture, which looks like mere wishful thinking: http://en.wikipedia.org/wiki/Chronology_protection
"The chronology protection conjecture is a conjecture by the physicist Professor Stephen Hawking that the laws of physics are such as to prevent time travel on all but sub-microscopic scales"
But "negative gravity" is possible. See wikipedia on the Casimir effect:
"Morris, Thorne and Yurtsever pointed out that the quantum mechanics of the Casimir effect can be used to produce a locally mass-negative region of space-time,[29] and suggested that negative effect could be used to stabilize a wormhole to allow faster than light travel."
Don't call something "impossible" just because you lack the imagination or means to do it. The only thing I see from "science" forbidding time travel is the "Chronology protection" conjecture, which looks like mere wishful thinking:
P.S. Is it just me, or is posting on these forums nearly impossible? I keep getting weird errors.
Someone please shoot me. To say "time exists" is to bludgeon language to death. Negative gravity? Time travel? "Locally mass-negative region of spacetime"?? My god, this is not science, it's not even science-fiction, it's just fiction...
Clayton -
I think the term you are looking for is negative fiction.
Clayton, liking Austrian Economics is no reason to make fun of or be ignorant of the inductive sciences like physics.
See von Mises "He who wants to achieve anything in praxeology must be conversant with mathematics, physics, biology, history, and jurisprudence" - http://mises.org/books/ultimate.pdf
If Hawking and Feynman think "time travel" is an appropriate topic for discussion in science, and Clayton doesn't, I think I know whom I'm going to listen to.
baxter:But "negative gravity" is possible. See wikipedia on the Casimir effect: "Morris, Thorne and Yurtsever pointed out that the quantum mechanics of the Casimir effect can be used to produce a locally mass-negative region of space-time,[29] and suggested that negative effect could be used to stabilize a wormhole to allow faster than light travel." Don't call something "impossible" just because you lack the imagination or means to do it.
Don't call something "impossible" just because you lack the imagination or means to do it.
That's only one interpretation of the Casimir effect, and one I will be quite surprised to find true. I prefer the quantized van der waals forces explanation. Seems far more likely. Could even have something to do with the strong force.
baxter: The only thing I see from "science" forbidding time travel is the "Chronology protection" conjecture, which looks like mere wishful thinking:[/
The only thing I see from "science" forbidding time travel is the "Chronology protection" conjecture, which looks like mere wishful thinking:[/
I doubt that the 'present' will be leavable. I subscribe to the idea that the past and future do not exist longer exist. The one has passed away, and the other must be produced by the present. There cannot be travel outside the present. Even in SR, to move forward in time can be achieved only by making it appear so: by slowing your own referential time-frame via strong gravity. You could never go 'back' to the past, for you merely found a way to advance the present moment without experiencing much time passage in your own frame.
baxter: P.S. Is it just me, or is posting on these forums nearly impossible? I keep getting weird errors.
The forum doesn't like javascript blocks, I'll tell you that much. It assumes you're a bot and errors you. I once got locked out of the forum for months, till I figured out it was caused by a cookie it set me. Anyway, now I only get errored out once in a blue moon.
Clayton:Someone please shoot me. To say "time exists" is to bludgeon language to death. Negative gravity? Time travel? "Locally mass-negative region of spacetime"?? My god, this is not science, it's not even science-fiction, it's just fiction... Clayton -
I love to see people's brains warped thus ^_^
Personally I do think negative gravity \ negative mass is fiction, or will be unrealizable.
But then again, we do calculations all day long with the set of imaginary numbers, and they work just fine. Many problems have proved impossible to solve without them.
If negative mass is possible, it exists on a level of reality far underneath even quantum mechanics, which so far we have been unable to manipulate.
We know that gravity itself may be generated at the very lowest of the low levels of reality, far, far, far below quantum effects.
As scientists, Hawking and Feynmann are merely describing phenomena and their causal relations. But the very problem with modern science is the ridiculous language chosen to discuss mere phenomena. For example, scientists will say something like "there are many, parallel universes" or "there are 26 dimensions that are all curled-up" and other such nonsense (and journalists only make it worse). In the case of many-universes, scientists don't even realize they are committing a petitio principii, a philosophical mistake so elementary that it's embarrassing to even have to point it out. In the case of the Universe having all these "hidden" dimensions, scientists forget to keep the mathematical dimensions in proper perspective - human science has three spatial dimensions and human geometry is Euclidean. The formal mathematics that may be piled on top of this in order to explain the phenomena within the three-dimensions of Euclidean, perceptual space are all fine and wonderful but the mathematical dimensions should never be confused with the three dimensions of perceptual space.
Modern science needs to overcome its obsession with the "counter-intuitive", oohing-and-aahing the public with a picture of a Star Trek universe, filled with "wormholes", "black holes", "teleportation" and other, fictional nonsense. It's great for the History channel. Not so good for progress.
Wow. I completely misread you, sorry.
But acceleration is not a frame invariant. We can tell when a frame is accelerating or it is not and that is how "the universe knows" who's clock is moving slower. The paradigms of SR are only applicable when acceleration is 0.
Let me say it another way that will maybe help clarify the problem with modern science.
What is the most powerful telescope/microscope? Nope, not Hubble. No, not the Very Large Telescope in Chile. No, not the Large Hadron Collider (this is nothing more than a giant microscope!) The most powerful microscope/telescope is the human brain itself. The human brain builds extensions to the human body in order to increase its resolving power. But even more powerful than the raw resolving power is the power of inference, our capacity to invent conceptual descriptions (formal models) of microscopic/telescopic phenomena - it is this power of inference that guides our quest to build more and more powerful resolving devices.
But what we are ultimately describing are not the phenomena "way out there" or the phenomena "way down there"... we are describing the numbers on the screen. That's it. To "observe" the "shadow" of the Higgs boson, the LHC performed a high-energy particle collision and then looked for a number on the output that was in the expected energy level for the boson. What is really being observed is not "a boson", but its effect - the number on the screen. The rest is just wild imagination.
Clayton: As scientists, Hawking and Feynmann are merely describing phenomena and their causal relations. But the very problem with modern science is the ridiculous language chosen to discuss mere phenomena. For example, scientists will say something like "there are many, parallel universes" or "there are 26 dimensions that are all curled-up" and other such nonsense (and journalists only make it worse).
As scientists, Hawking and Feynmann are merely describing phenomena and their causal relations. But the very problem with modern science is the ridiculous language chosen to discuss mere phenomena. For example, scientists will say something like "there are many, parallel universes" or "there are 26 dimensions that are all curled-up" and other such nonsense (and journalists only make it worse).
Well, frankly, I have never accepted either of those conjectures. You're talking theoretical explanations now, not stuff we know for sure to be true. We do know SR is true. I don't think you should conflate conjectures with observable reality.
Also, I laugh every time string-theorists get disappointed. I've always thought that was particularly bunk.
Clayton:In the case of many-universes, scientists don't even realize they are committing a petitio principii, a philosophical mistake so elementary that it's embarrassing to even have to point it out.
And what would that be, explicitly? I don't accept the many-universes conjectures, but am interested in your critique of it.
Clayton:In the case of the Universe having all these "hidden" dimensions, scientists forget to keep the mathematical dimensions in proper perspective - human science has three spatial dimensions and human geometry is Euclidean. The formal mathematics that may be piled on top of this in order to explain the phenomena within the three-dimensions of Euclidean, perceptual space are all fine and wonderful but the mathematical dimensions should never be confused with the three dimensions of perceptual space.
I agree. A fourth physical dimension (not time) actually would mean... well it's hard to explain, but I'll refer you to Dr. Quantum and the Flatland story:
Clayton: Modern science needs to overcome its obsession with the "counter-intuitive", oohing-and-aahing the public with a picture of a Star Trek universe, filled with "wormholes", "black holes", "teleportation" and other, fictional nonsense. It's great for the History channel. Not so good for progress. Clayton -
Between the lay reader and the pro, there's is an incredible amount of misunderstanding. I'll say that much.
At the same time, I'm still wrapping my head about the idea that there cannot be a hidden variable in the entanglement phenomena and how we know there cannot be.
But you see popular misrepresentation of this all the time, like in Mass Effect 3 and other stories which purport to use entanglement to pass message faster than light, the idea being you somehow control which way an entangled quanta comes out on one end and the other entangled quanta will then be forced to come out the same way in some far off place.
But that's not how it works in reality at all. In reality, the outcome is already decided at the moment they've been entangled--at least that's my understanding. The difference is, there's no way to know what state the entanglement will decay into until you actually go to measure it, and at that point when you decay its state the end-state is revealed, and both entangled particles will reveal the same state.
Some of that explanation may reflect my persistent bias towards 'hidden variable' understandings of entanglement tho :P But what definitely can't be done is passing info faster than light using entanglement such as in the fiction.
As I already said, there is no doubt that the mathematics of SR describe the physics of the world. The problem is that the mathematics of SR do not necessarily imply a speed-limit of light.
The point of explaining phenomena is to eliminate possibilities. Any explanation that invokes all possibilities is a non-explanation in disguise - it is begging the question.
But that's not how it works in reality at all. In reality, the outcome is already decided at the moment they've been entangled--at least that's my understanding. The difference is, there's no way to know what state the entanglement will decay into until you actually go to measure it, and at that point when you decay its state the end-state is revealed, and both entangled particles will reveal the same state. Some of that explanation may reflect my persistent bias towards 'hidden variable' understandings of entanglement tho :P But what definitely can't be done is passing info faster than light using entanglement such as in the fiction.
As Ron Garret explains in the YT video linked above, entanglement is causality.
>Anenome: I subscribe to the idea that the past and future do not exist longer exist.
It sounds like you haven't considered or answered the Rietdijk-Putnam Argument. In that case, your uninformed opinion adds little to the discussion.
>Anenome: At the same time, I'm still wrapping my head about the idea that there cannot be a hidden variable in the entanglement phenomena
Non-local hidden variables are not ruled out. In particular, in the perfectly valid Bohmian interpretation of quantum mechanics, particles possess "beables" rather than observables and they have precise positions, momenta, and trajectories. Particles are coordinated by the so-called pilot wave.
>Clayton: In the case of the Universe having all these "hidden" dimensions, scientists forget to keep the mathematical dimensions in proper perspective - human science has three spatial dimensions and human geometry is Euclidean.
No. I refer you again to Mises's "The Ultimate Foundation of Economic Science":
"praxeology is not geometry. It is the worst of all superstitions to assume that the epistemological characteristics of one branch of knowledge must necessarily be applicable to any other branch. In dealing with the epistemology of the sciences of human action, one must not take one's cue from geometry, mechanics, or any other science... The assumptions of Euclid were once considered as self-evidently true. Present-day epistemology looks upon them as freely chosen postulates, the starting point of a hypothetical chain of reasoning."
>Clayton: What is really being observed is not "a boson", but its effect - the number on the screen. The rest is just wild imagination
Wrong again. It sounds like, when you encounter something you don't like, you childishly adopt some kind of idealism to dismiss the unliked thing. But we know bosons are real because we can manipulate them. See this analysis of Mises's and Hoppe's neo-Kantianism. http://mises.org/journals/qjae/pdf/qjae10_2_4.pdf
"The fact that we can act on existing entities—be those our own organisms or entities external to us—implies that we can know something about those entities, enough to act on them. The fact that some of our actions are successful—i.e., the means utilized have indeed achieved the ends aimed at—means that some of the knowledge of external reality we used has indeed been correct."