Question on Spacetime

Kevster

'Time' is just a concept that we have created to describe the world around us, just as language is. It's not real in any physical sense. It's just a concept. The Universe doesn't care less for time as it would care for a force like gravity, for example.

Turtwig

Kevster wrote: »

'Time' is just a concept that we have created to describe the world around us, just as language is. It's not real in any physical sense. It's just a concept. The Universe doesn't care less for time as it would care for a force like gravity, for example.

Em, GR kinda relies on time being physical in some sense anyways.

Kevster

That's maths though, which isn't reality. Maths is a best approximation of what our reality is (and will be). Time really isn't a physical concept... use your brain and think about it. The notion of time - I believe - introduces it's own problems into GR, such as the necessity for a beginning of time (i.e. Big Bang).

Morbert

Kevster wrote: »

That's maths though, which isn't reality. Maths is a best approximation of what our reality is (and will be). Time really isn't a physical concept... use your brain and think about it. The notion of time - I believe - introduces it's own problems into GR, such as the necessity for a beginning of time (i.e. Big Bang).

Even if time emerges from change, it is still a physical concept, just as length or height is a physical concept. The difficulty with relativity is not related to the ontology of time. Instead, it's related to the formalism, and how that formalism compares to the formalism of quantum mechanics.

I'm all for investigating the nature of time. But if it doesn't produce a new formalism then it isn't much use to scientists. Scientists are less interested in questions like "Does time exist?" and more interested in questions like "Should we treat time as a dynamical variable?"

Vergast

'Time' is just a concept that we have created to describe the world around us, just as language is. It's not real in any physical sense. It's just a concept. The Universe doesn't care less for time as it would care for a force like gravity, for example.

No, the universe most definitely needs time and gravity. Without gravity there would be no universe! Hell if any of the 4 forces were much different from thier current values then god only know what would have happened.

Turtwig

Vergast wrote: »

No, the universe most definitely needs time and gravity. Without gravity there would be no universe! Hell if any of the 4 forces were much different from thier current values then god only know what would have happened.

I think there was something recently about the electro-weak force not being needed. Not sure of how well accepted this idea is though.:)

Kevster

Vergast wrote: »

No, the universe most definitely needs time and gravity. Without gravity there would be no universe! Hell if any of the 4 forces were much different from thier current values then god only know what would have happened.

You misinterpreted what I wrote: I implied that the Universe doesn't need time and that it does need gravity. However, I can see now why time is important. Due to what Morbert wrote three posts up, I have changed my opinion about it (time).

roosh

looks like we could have a decent debate on our hands here too

Morbert wrote: »

Even if time emerges from change, it is still a physical concept, just as length or height is a physical concept.

The thing is however, that time emerges from change in much the same way that the concept of the earth being flat, emerged from a limited and incorrect interpretation of the earth, or the same way that the concept of the sun orbiting the earth emerged.

Morbert wrote: »

The difficulty with relativity is not related to the ontology of time. Instead, it's related to the formalism, and how that formalism compares to the formalism of quantum mechanics.

it has been purported, by Julian Barbour in "End of time" - among others - that the "problem of time" between QM and GR is resolvable, when time is considered to be non-existent.

Morbert wrote: »

I'm all for investigating the nature of time. But if it doesn't produce a new formalism then it isn't much use to scientists. Scientists are less interested in questions like "Does time exist?" and more interested in questions like "Should we treat time as a dynamical variable?"

Not entirely sure what kind of formalism may arise, but if it were to be considered in the same sense that measurements are considered e.g. centimetres, metres, etc.

It appears that Barbour and Niall Ó Murchadha(among others) are currently working on a Research Project with regard to the non-existence of time and its impact on General Relativity.

Kevster

mangaroosh wrote: »

The thing is however, that time emerges from change in much the same way that the concept of the earth being flat, emerged from a limited and incorrect interpretation of the earth, or the same way that the concept of the sun orbiting the earth emerged.

I think that it's a bit unfair to compare this minor debate on time with the much earlier theories on the position of the Sun and the shape of the Earth. They aren't really comparable, and any comparison is therefore false/unfair. If you are merely saying, however, that what has been commonly regarded as the truth before has been debunked later on, then I see your point. Still, I can't see 'time' being extracted from any cosmological equations for a long time. It's a fundamental concept.

Fringe

Interesting. I think I'm understanding your point a bit more now. I think though, regardless of its existence or not, we still experience time as an effect and our theories are consistent with this effect. For example, in a rotating reference frame, we experience centrifugal/coriolis forces but these do not really exist in a way yet we acknowledge their effect. In the same way, time exists because it has an effect on us.

Morbert

mangaroosh wrote: »

The thing is however, that time emerges from change in much the same way that the concept of the earth being flat, emerged from a limited and incorrect interpretation of the earth, or the same way that the concept of the sun orbiting the earth emerged.

This is a very large claim. It may turn out to be true, but to show that it is true, you would need a "timeless" formalism of the laws of physics which explain phenomena that current formalisms can't. Until then, while I certainly won't dismiss it, I won't accept it either.

It has been purported, by Julian Barbour in "End of time" - among others - that the "problem of time" between QM and GR is resolvable, when time is considered to be non-existent.

It appears that Barbour and Niall Ó Murchadha(among others) are currently working on a Research Project with regard to the non-existence of time and its impact on General Relativity.

A different treatment of time may yield fruitful results, and a timeless theory of quantum gravity has its advantages, though it's important to qualify what they mean by timeless. From what I gather, Barbour's work is closely linked to the ADM formalism of General Relativity, where local time-evolution can apparently be determined by a structure of foliated spacelike "moments". Time lapse, in other words, emerges from such structures. It is certainly exciting work, but it doesn't "kill" time in the manner you seem to be inferring. Nor has it yet solved the problem of quantum gravity. Quantization is still an issue, and there are approaches that don't treat time in this manner which are just as potentially valid.

Kevster

Sorry to slightly deviate, but if 'time' is something that is real, then shouldnt' we be able to manipulate it? I still hold the view that it's merely a 'figment of our imagination' - i.e. a concept and consequence of mere language and thought - and that it's simply something that can never be altered.

I mentioned earlier at how the introduction of a time variable necessitates the need for a beginning and end. Our brains cannot seem to interpret that there was 'always' a Universe. We rthink in terms of time and this requires a start/end.

...thoughts?

Kevin

Podge_irl

Kevster wrote: »

Sorry to slightly deviate, but if 'time' is something that is real, then shouldnt' we be able to manipulate it? I still hold the view that it's merely a 'figment of our imagination' - i.e. a concept and consequence of mere language and thought - and that it's simply something that can never be altered.

Can people manipulate space? Anything you do to "manipulate space" - i.e., curve it or bend it, also has an effect on time.

Our brains cannot seem to interpret that there was 'always' a Universe. We rthink in terms of time and this requires a start/end.

I'd argue the opposite. People seem to have an issue with dealing with nothingness and are prone to asking questions such as "what happened before the bang", even if such questions don't make sense.

Morbert

Kevster wrote: »

I mentioned earlier at how the introduction of a time variable necessitates the need for a beginning and end. Our brains cannot seem to interpret that there was 'always' a Universe. We rthink in terms of time and this requires a start/end.

Just to clear up some possible confusion. GTR is already, in a sense, timeless, as the spacetime manifold "always" exists. Time, according to relativity, is simply a dimension, like space, and time-evolution is determined by timelike paths through spacetime. What Barbour is suggesting is removing time as a dimension and re-introducing it as a parameter deriveable through local spatial variables.

Myrddin

Isnt it proven, that the faster something approaches light speed, that the passage of time changes for that object relative to a stationary object? (Relativity)

If so, then isnt time then proved as existing? Its nature changes, given interaction. It might be our definition of time which is right/wrong, but it is a reality of sorts, which is intertwined with space.

roosh

Kevster wrote: »

I think that it's a bit unfair to compare this minor debate on time with the much earlier theories on the position of the Sun and the shape of the Earth. They aren't really comparable, and any comparison is therefore false/unfair. If you are merely saying, however, that what has been commonly regarded as the truth before has been debunked later on, then I see your point. Still, I can't see 'time' being extracted from any cosmological equations for a long time. It's a fundamental concept.

apologies, the tone may have been somewhat derogatory, but they are meant to be taken as illustrative examples.

essentially the concept of time arises out of a misperception of our obeserved environment.

roosh

Morbert wrote: »

This is a very large claim. It may turn out to be true, but to show that it is true, you would need a "timeless" formalism of the laws of physics which explain phenomena that current formalisms can't. Until then, while I certainly won't dismiss it, I won't accept it either.



A different treatment of time may yield fruitful results, and a timeless theory of quantum gravity has its advantages, though it's important to qualify what they mean by timeless. From what I gather, Barbour's work is closely linked to the ADM formalism of General Relativity, where local time-evolution can apparently be determined by a structure of foliated spacelike "moments". Time lapse, in other words, emerges from such structures. It is certainly exciting work, but it doesn't "kill" time in the manner you seem to be inferring. Nor has it yet solved the problem of quantum gravity. Quantization is still an issue, and there are approaches that don't treat time in this manner which are just as potentially valid.

I'll have to hold my hands up and say that I wouldn't have much of a clue how it would affect any of the scientific theories, so apologies for just regurgitating what I have read myself.

I know I asked the question with regard to General Relativity, but that was largely because of my perception of how time is handled in General Relativity. It appears that it is given some intrinsic existence, as making up "the fabric of reality", as opposed to being a man made concept.


The core question is on the existence of time, whether it is a real "thing" or just a human concept. Again, the contention is that it is just a human concept based on our perception of the universe.

I presume this would have some impact on those scientific theories that treat time as though it exists in reality, although I am not in a position to say what that would be, exactly.

roosh

EnterNow wrote: »

Isnt it proven, that the faster something approaches light speed, that the passage of time changes for that object relative to a stationary object? (Relativity)

If so, then isnt time then proved as existing? Its nature changes, given interaction. It might be our definition of time which is right/wrong, but it is a reality of sorts, which is intertwined with space.

Is it time dilation that is referred to above?

Kevster

Also in response to that (what EnterNow said), is that anything to do with the 'twins' paradox? - i.e. where if one twin grew up on Everest and the other at ground level, the one on Everest would age quicker? I never understood this in any sense.

Morbert

Yes, that is time dilation. Electromagentism demands that everyone observes the speed of light to be "c". This is only possible if we discard the notion that time has a fixed rate of passage for everyone.

As for the twin paradox: A twin on everest would age more, but typically speaking, the twin paradox is normally presented with one twin travelling a great distance and returning to earth, while the other twin remains on earth. According to relativity, the passage of time acts somewhat like an odometer for our journey through spacetime. The longer a path through spacetime, the more time experience by someone on that path. The geometry of spacetime is a weird kind, called "pseudo-riemannian", and it tells us, oddly enough, that the twin that stayed on earth actually travelled a longer path through spacetime, and hence experienced more time, than the twin that left earth and came back. The reason it's called a paradox is there are some issues with the symmetry of time dilation that take a little thinking to overcome.

There are other strange features of relativity as well, like simultaneity. To use Roger Penrose's example, in my "now" an alien fleet could be on their way from the andromeda galaxy to take over earth, while in your "now" they could still be debating amongst themselves whether to invade earth. All of these features fall out of the geometry of spacetime described by relativity.

Kevster

So it's not actually that time has moved more quickly for one and not the other? Rather, that is just what is perceived by them? Time is universal, after all, and we cannot change it's progress. Even if that's what this paradox is about, it still doesn't hold much practical sense - i.e. it doesn't seem likely that it would actually happen in reality.

Morbert

Kevster wrote: »

So it's not actually that time has moved more quickly for one and not the other? Rather, that is just what is perceived by them? Time is universal, after all, and we cannot change it's progress. Even if that's what this paradox is about, it still doesn't hold much practical sense - i.e. it doesn't seem likely that it would actually happen in reality.

GPS systems must incorporate these relativistic effects to work. Such effects have also been observed in a variety of experiments ranging from clocks in planes to particle physics.

Myrddin

Kevster wrote: »

So it's not actually that time has moved more quickly for one and not the other? Rather, that is just what is perceived by them? Time is universal, after all, and we cannot change it's progress. Even if that's what this paradox is about, it still doesn't hold much practical sense - i.e. it doesn't seem likely that it would actually happen in reality.

I think the rate of time DOES change, the nearer to lightspeed you get. Its the perception of time that doesnt. Say astronaught A is travelling at 95% of C, and astronaught B is stationary, well astronaught A would perceive nothing strange at all, but if astronaught B was somehow able to observe A - he would appear to be fozen in time (moving really slowly) - at least thats how I think it works.

The two atomic clocks on in the Concorde experiment was another good one. One clock was placed in a fixed location, whilst the other was flown around the world at supersonic speeds. Upon re-uniting the two clocks, it was found the the clock which was travelling was slower than the fixed one by a very very tiny amount. These were two atomic clocks, and yet for one of them, the passage/flow of time was altered - albeit on a very small scale.

roosh

EnterNow wrote: »

I think the rate of time DOES change, the nearer to lightspeed you get. Its the perception of time that doesnt. Say astronaught A is travelling at 95% of C, and astronaught B is stationary, well astronaught A would perceive nothing strange at all, but if astronaught B was somehow able to observe A - he would appear to be fozen in time (moving really slowly) - at least thats how I think it works.

Is it possible to take a similar example, but on a more local scale. For example, if one were to stand at the start of a runway say, and a car were to drive aware from the person. After a certain point, the car driving away from the person on the runway would not really appear to be moving (assuming a very long runway), or at least would appear to be moving less, the more it accelerated.

EnterNow wrote: »

The two atomic clocks on in the Concorde experiment was another good one. One clock was placed in a fixed location, whilst the other was flown around the world at supersonic speeds. Upon re-uniting the two clocks, it was found the the clock which was travelling was slower than the fixed one by a very very tiny amount. These were two atomic clocks, and yet for one of them, the passage/flow of time was altered - albeit on a very small scale.

The base assumption that an atomic clock actually measures something called time, is questionable, as opposed to the microwave emissions of the changing electrons, being a unit of the measurement system called time.

i.e. the microwave emissions are to time what nanometres (or cm, or m, or other) are to the metric system.


It would be more plausible, that the effect of flying at supersonic speeds, had a physical impact on the microwave emissions of the changing electrons, as opposed to the notion that the passage of the "thing" called time actually changed, which itself is a non-sequitur.

In a similar sense that increased pressure on ice lowers its melting point, as opposed to speeding up time.

Kevster

I just don't understand it... That 'concorde' thing, for example. I cannot see how one atomic clock would show a different time unless it somehow absorbed more radiation than the other (and therefore decayed more quickly).

Kevin

Turtwig

Kevster wrote: »

I just don't understand it... That 'concorde' thing, for example. I cannot see how one atomic clock would show a different time unless it somehow absorbed more radiation than the other (and therefore decayed more quickly).

Kevin

Atomic clocks are very precise, even a small relativistic time difference is measurable.

Kevster

That's not really what I was asking. Im aware of their accuracy, but what I was implying was that I don't 'buy' this notion of time moving at different paces, and that this 'concorde' example with atomic clocks can be explained by one clock simply absorbing slightly more radiation than the other (and therefore decaying faster and giving a different time).

If the experiment was repeated a number of times, I doubt the results would be consistent.

roosh

Kevster wrote: »

I just don't understand it... That 'concorde' thing, for example. I cannot see how one atomic clock would show a different time unless it somehow absorbed more radiation than the other (and therefore decayed more quickly).

Kevin

the physical effect of travelling at speed, would have a physical effect on the microwave emissions.

again, however, the assumption that a clock measures something called time is questionable.

Kevster

mangaroosh wrote: »

the physical effect of travelling at speed, would have a physical effect on the microwave emissions.

again, however, the assumption that a clock measures something called time is questionable.

That's exactly the comment/answer I wanted to hear. Thanks dude.

Kevin

ZorbaTehZ

That is the thing about relativity, there is nothing intuitive about it due to the simple fact that we do not have day-to-day experience with bodies that travel at an appreciable fraction of the speed of light - classical mechanics seems almost obvious for the opposite reason.

There seems to be confusion about what the Twin Paradox is - it says nothing about living on a mountain (or at least no version I've come across has) Instead it highlights a (non-existant) problem with the STR and frames of reference. I'm not sure though if it's useful for this discussion.