The Time Machine - 2002 movie

[Pondwater]

I remember it being not bad, but I still prefer the 1960s version.

Same here.

 

[cooleddie74]

The 1960 version with Rod Taylor is far superior but the newer film does have some visually compelling aspects. At the end of the day, though, the Rod Taylor adaptation and Time After Time are far more enjoyable and memorable films.

 

[Steven P Bastien]

It is not speculation. It is prediction, which is the exact thing that theory is for. A theory is a mathematical model that explains existing data and allows you to predict new, untested scenarios that can be confirmed or refuted by later data. Think of existing data as isolated points on a graph, and a theory as the equation for a curve connecting those points. Once you have the equation, you can predict a position for any possible point on that curve out to infinity, and by taking new measurements and putting more points on the graph, you can find out which of the possible curve equations predicted those measurements correctly, and thereby rule out the wrong ones.

That's the power of theory, in that it allows itself to be tested for accuracy rather than taken on faith, and in that it points us toward new insights into physics that we never would have gotten based solely on existing data. That is the very thing that makes science work in the first place, because it is far less random and more rigorous than mere "speculation." General Relativity has made many predictions that later observation and experiment have proven true, from the precession of Mercury's orbit and the gravitational redshift of light to the existence of gravitational lensing and black holes. It's simply a matter of taking the relativistic equations that have been verified by past observations and applying them to new situations.

Once again, let's be clear: The statement I was responding to was, "we don't know any theory that definitely allows travel backwards in time." That was a comment about theory, not about practice. My point was simply that General Relativity, as a theory, definitely does include backward time travel as a mathematically allowable solution to its equations. Indeed, most of the conjectural methods of time travel we know were first predicted by GR -- wormholes, black holes, Kerr singularities, Tipler cylinders, they all come directly and specifically from that theory. Because a theory is a set of equations that allow you to predict hypothetical scenarios with mathematical rigor rather than random handwaving.




Then I'm confused that you changed the subject and started talking about experiment when I thought we were both talking strictly about theory.




As I already said, yes, they basically are, as long as we're talking about theory rather than observation. This is an enduring mystery of physics -- there is no clear "arrow of time" built into existing theories, no reason why time travel in both directions shouldn't be possible. The singular direction of time is an observation of real-world data, but the theory, the math that we use to explain how and why reality works, doesn't yet include a clear and agreed-upon explanation for why time is unidirectional. Many theoretical physicists will insist that time doesn't even exist, that it's an illusion of human perception with no objective physical meaning. Here's an article I recently read that addresses that issue, which is why it's fresh in my mind: https://www.quantamagazine.org/a-defense-of-the-reality-of-time-20170516/




The word "theory" has a very specific meaning in science that is constantly abused and misunderstood by laypeople, which is why I'm so picky about it. A theory is a mathematical model that makes predictions beyond observed data. Therefore, a theory does, by its very nature and purpose, include predictions beyond anything we've observed or tested yet in real life.




They're both solutions of the exact same equations. Those same equations predict the causality and FTL issues you raise as obstacles. So no, from a theoretical standpoint, it's not more speculative. They are both covered by the same math. Backward time travel is not beyond the theory; it is predicted and described by the theory, right down to the reasons why it's prohibitively unlikely in practice. We don't lack theoretical knowledge of how it would work if it were possible. We have very clear theoretical predictions that tell us exactly why it's probably not possible, but that also tell us a lot about how it would work if it were.

There are many things here I agree with and several that I don't agree with entirely. Theory does cover a wide range and the term is often misused, but I think you are also not describing it perfectly either. It's one of those words that you can debate about and eventually you get into semantics.

In any event, this detail (while interesting) goes beyond what I was trying to say. I just wanted to say (as a passing point) that forward and backward travel are not on the same footing in physics, which is definitely true because one is accepted scientific fact and the other is unverified prediction and speculation. There are many good reasons to doubt any predictions about backward time travel, but of course we keep asking the question and exploring the possibility. We do this because we are curious, we like to speculate and the predictions from theory are calling us too. Also, as a main point, i wanted to mention the known idea that space-time is the important concept when people are worrying about a time-machine appearing stationary when everything is really moving. This is a key result of physics and when people are worrying about a (apparently) stationary time machine moving in time relative to the local surroundings, they are worrying about the important fact that this is contradictory to what Einstein's theory would say can happen. Generally (pardon the pun) one needs to move into different reference frames to change the time dimension.

 

[Christopher]

In any event, this detail (while interesting) goes beyond what I was trying to say. I just wanted to say (as a passing point) that forward and backward travel are not on the same footing in physics, which is definitely true because one is accepted scientific fact and the other is unverified prediction and speculation.

And I'm trying to point out that the actual physics conflict with that common-sense assumption in some ways that are interesting to contemplate if you're willing to open your mind to them. As I've said, there is no clear "arrow of time" in physics as we currently formulate it, no clear answer for why time shouldn't be reversible. As the article I linked to points out, if you treat time as a dimension as in General Relativity, then it follows that it should be as bidirectional as the spatial dimensions -- though the scientist who's the focus of the article is arguing for an alternate view that disagrees with that long-held conventional wisdom among physicists. That's the interesting and surprising part -- laypeople assume that unidirectional time is the default expectation and movement backward in time is the anomaly that needs justifying, but in theoretical physics, it's the other way around, with most physicists asserting that time has no inherent direction, so that the people saying it does are the oddballs met with skepticism.

The thing about common sense is that it's derived from everyday life experience. A lot of theoretical physics is about situations wildly outside the conditions we encounter in everyday life, so it can diverge massively from our common-sense expectations about how the universe should work. So while a statement like "forward time travel is more physically real than backward" fits perfectly with everyday, common-sense expectations, the actual theories and equations of physics paint a surprisingly different picture, at least as currently formulated.

This is a key result of physics and when people are worrying about a (apparently) stationary time machine moving in time relative to the local surroundings, they are worrying about the important fact that this is contradictory to what Einstein's theory would say can happen. Generally (pardon the pun) one needs to move into different reference frames to change the time dimension.

That's basically right, but of course, Wells was writing before Einstein. What he was portraying was more a form of extreme time dilation, with the machine's internal time flow greatly slowed down relative to an outside observer, so that it was basically frozen in place while time moved forward around it -- and the reverse time travel was basically negative time dilation. So it's not quite the same as most later portrayals of time travel.

Although, as someone mentioned above, that does create the paradox of why outside observers perceived the Time Machine as absent rather than frozen in place -- although Time After Time seemed to imply that it had remained in place so that it was available to be moved to San Francisco (though I think it was inconsistent about that, since it did disappear when it went back at the end).

 

[Steven P Bastien]

And I'm trying to point out that the actual physics conflict with that common-sense assumption in some ways that are interesting to contemplate if you're willing to open your mind to them. As I've said, there is no clear "arrow of time" in physics as we currently formulate it, no clear answer for why time shouldn't be reversible. As the article I linked to points out, if you treat time as a dimension as in General Relativity, then it follows that it should be as bidirectional as the spatial dimensions -- though the scientist who's the focus of the article is arguing for an alternate view that disagrees with that long-held conventional wisdom among physicists. That's the interesting and surprising part -- laypeople assume that unidirectional time is the default expectation and movement backward in time is the anomaly that needs justifying, but in theoretical physics, it's the other way around, with most physicists asserting that time has no inherent direction, so that the people saying it does are the oddballs met with skepticism.

The thing about common sense is that it's derived from everyday life experience. A lot of theoretical physics is about situations wildly outside the conditions we encounter in everyday life, so it can diverge massively from our common-sense expectations about how the universe should work. So while a statement like "forward time travel is more physically real than backward" fits perfectly with everyday, common-sense expectations, the actual theories and equations of physics paint a surprisingly different picture, at least as currently formulated.




That's basically right, but of course, Wells was writing before Einstein. What he was portraying was more a form of extreme time dilation, with the machine's internal time flow greatly slowed down relative to an outside observer, so that it was basically frozen in place while time moved forward around it -- and the reverse time travel was basically negative time dilation. So it's not quite the same as most later portrayals of time travel.

Although, as someone mentioned above, that does create the paradox of why outside observers perceived the Time Machine as absent rather than frozen in place -- although Time After Time seemed to imply that it had remained in place so that it was available to be moved to San Francisco (though I think it was inconsistent about that, since it did disappear when it went back at the end).

That's fine. I'm not trying to interfere with what you are trying to point out. You are free to express this opinion. Again, I agree with much of what you say. Some of the wording I'm not 100% comfortable with, but I don't want to split hairs. I believe I understand what you are saying. Open minds are good to have in science. But, it's also important to draw the distinction between unverified predictions and "scientific fact". I'm a scientist and engineer by lifelong training and I've run through the full gamut of viewpoints about "scientific fact", "scientific theory", "speculation" etc. I see clearly now that mathematical models and physics theories have a dual aspect to them. They are "approximate models" always and do not have a necessary objective reality on their own. They are also a "human language" which can express ideas that are not always easy to express in words. This latter aspect opens the viewpoint that the math/theory can be speculation, especially since the "model" aspect of that is definitely an approximation. You seem to not like me using that word speculation, but since theories/math/models are the thing I deal with constantly on a daily basis, I need to be open to using this word and I'm not the only one in science to have this viewpoint. But, I don't want to argue about semantics and definitions, so I tried to also express my thoughts in different words too.

 

[Christopher]

But, it's also important to draw the distinction between unverified predictions and "scientific fact".

Now you're just being insulting. I never said anything about "scientific fact." "Fact" is a word that has no meaning in science -- and you're not the only one in this conversation with a physics degree.

I have said this over and over again: I was responding to your statement about theory. I was speaking specifically about what the theory said, and how that differs from a discussion of observations or results. I was not asserting an "opinion" on the truth of the theory. I was merely describing what the theory says and how it differs from lay expectations. Description or discussion is not endorsement or polemic. As a scientist, you should understand that.

 

[Steven P Bastien]

Now you're just being insulting. I never said anything about "scientific fact." "Fact" is a word that has no meaning in science -- and you're not the only one in this conversation with a physics degree.

OK, now I'm just confused, honestly. I'm not trying to be insulting. I never said you said anything about it. I was making my own point that it is important (at least in my opinion) to make the distinction. In responding you you, I was trying to clarify my original message which I could see in hindsight was not clear.

There is a concept of "scientific fact". It simply means things that are considered so well-known that they attain this label. For example, the fact of "gravitation". We have theories of gravitation to describe the fact of gravitation. For time travel, we have Relativity Theory that describes the fact that forward time travel happens.

I know I'm not the only one with a physics degree, or that has an understanding of physics. That's probably why I was lazy and unclear in my original post, because I just thought everyone would understand what I was trying to say.

Anyway, I don't want to be insulting, but this conversation has somehow taken an unpleasant turn, and I will just leave it. I'm not looking to argue with or insult people.

 

[Spot261]

I'm willing to suspend my disbelief that any fictional characters who figure out how to travel through time also figure out how to lock their position relative to the Earth.

Would make for a very different show if anyone who time travelled ended up embedded in rock or lost in the vacuum of space...

 

[Maurice]

Now you're just being insulting.

If so: pot, meet kettle.

 

[cooleddie74]

This burrito is AMAZING.

 

[RJDiogenes]

Nobody expects the Spanish Inquisition!

If it wants to make light of itself.

Maybe it could just wave at itself.

 

[Gov Kodos]

Nobody expects the Spanish Inquisition!


Maybe it could just wave at itself.

It could function that way sort of like a pilot. It can wave so it doesn't collapse.

 

[RJDiogenes]

It could function that way sort of like a pilot. It can wave so it doesn't collapse.

I feel like it's just stringing us along.

 

[cooleddie74]

Wave at the light, kids.