Time

ronbyrne2005

What is time in laymans terms? If it flows and there is not discrete how can we know it flows at a constant rate. Whats the relationship between matter and time apart from matter bending spacetime via gravity.

Professor_Fink

The simple answer is that time is just another dimension, like the three spacial dimensions that we inhabit. It has a special property in that we treat it as an 'imaginary' dimension. By this I mean that we take distances in the time dimension to be multiplied by i (the square root of -1).

Once we take this into account, we have a four dimensional space (known as Minkowskian spacetime). In the general theory of relativity, this spacetime can be curved by the presence of matter. In non-relativistic theories, time is uneffected by matter.

Hope this helps.

Son Goku

ronbyrne2005 wrote:

What is time in laymans terms?

The direction you move in spacetime, which is the four-dimensional continuum we all live in.

ronbyrne2005 wrote:

If it flows and there is not discrete how can we know it flows at a constant rate.

It doesn't, it slows down and speeds up for different observers. In fact it doesn't even stay seperated cleanly as time and space. What's one second to me can be a meter to somebody else (to paraphrase).

ronbyrne2005 wrote:

Whats the relationship between matter and time apart from matter bending spacetime via gravity.

Matter bends spacetime to cause gravity, in fact gravity is the bending of spacetime. An example of this is seen very clearly near a blackhole. The timelines of objects are so disorted that they all bend into the hole. Things don't "fall" into black holes they "exist" into them.

In truth we simply live in a large continuum called spacetime. Imagine it to be a large country. Every object is a car and there are dozens of roads. Time is like the distance along these roads. Large objects will divert the roads towards themselves.

ronbyrne2005

Still cant conceptualise it. Does anyone think the future of everything in universe is predestined ? I read something by Roger Penrose about this , about trying to reconcile relativity with quantum stuff. Suppose I should have done physics for leaving cert

Professor_Fink

ronbyrne2005 wrote:

Still cant conceptualise it. Does anyone think the future of everything in universe is predestined ? I read something by Roger Penrose about this , about trying to reconcile relativity with quantum stuff. Suppose I should have done physics for leaving cert

Quantum cosmology isn't on the leaving cert course!

It largely depends on what you mean by predestined. If you are referring to a some wave function for the universe, including you in a superposition of states, then it does seem likely that it is completely deterministic. If you mean deterministic from your perspective, then the answer is a definite know, since measurements on quantum states are essentially stochastic.

ronbyrne2005

So every thing humans do on a day to day basis like decide to take the day off work is'nt likely to be predetermined? Even if there was infinite parralel universes I find it hard to beleive that things like comedy and fashion were pretermined at begining of universe. An individual persons life on a day to day basis is not predetermined and they are free to choose what they are gonna do at any given point in time?

Son Goku

ronbyrne2005 wrote:

Still cant conceptualise it. Does anyone think the future of everything in universe is predestined ?

You'll only confuse things if you bring in philosophical positions. The first thing to understand is time is a physical entity in itself, which was something that was only understood in 1915. When I say physical entity, I mean it reacts and responds to the presence of other physical things. It's another thing like heat or length or matter. Determinism as such wouldn't really have anything specifically to do with time, you could say that time becomes just another object that may be subject to determinism. You can understand time by understanding its properties. Things like determinism are for understanding the universe as a whole.

ronbyrne2005 wrote:

So every thing humans do on a day to day basis like decide to take the day off work is'nt likely to be predetermined? Even if there was infinite parralel universes I find it hard to beleive that things like comedy and fashion were pretermined at begining of universe. An individual persons life on a day to day basis is not predetermined and they are free to choose what they are gonna do at any given point in time?

Again, even if people do have free will, time is still time. A second still ticks away.

Professor_Fink

ronbyrne2005 wrote:

So every thing humans do on a day to day basis like decide to take the day off work is'nt likely to be predetermined? Even if there was infinite parralel universes I find it hard to beleive that things like comedy and fashion were pretermined at begining of universe. An individual persons life on a day to day basis is not predetermined and they are free to choose what they are gonna do at any given point in time?

Son Goku raises a good point, that this is a different set of questions, which will not help you understand time.

If you are worried about determinism, the short answer is that there is no known physical mechanism to provide free will. Physics as it stands does not allow for free will, while at the same time the laws governing measurements of quantum systems demand that quantum events appear non deterministic (Although we can calculate the probabilities of observing an event). In many interpretations, however, we can view the universe as being deterministic as a whole, but what we are aware of is in some ways random.

But interpretations is a whole other can of worms.

ronbyrne2005

But everything I do isnt predestined down to every thought feeling and every sub atomic particle in the universe? I am free to choose what to do this afternoon? If not "free will" do I have "free choice" within my innate and learned abilities constraints etc?

As time is a physical entity i assume its massless, can it eventually rip apart? I heard recent theories suggesting inflationary theory of the univesr may not be completely accurate.

Professor_Fink

Ok, you seem to be including a whole load of seperate issues here, so I'll try to seperate them out:

ronbyrne2005 wrote:

But everything I do isnt predestined down to every thought feeling and every sub atomic particle in the universe?

This is a little hard to answer, and largely depends on what you mean by predestined. All of what we know about physics says that given some initial state, the state some finite time later is completely determined. In this way you can say that the universe appears to be completely deterministic.

The way humans experience the universe is a little different. When we measure a quantum system it appears to us to collapse in a probabilistic manner. So from our point of view it does not appear to be deterministic. If we treat the whole system (us and whatever system we are observing) as quantum mechanical, then we recover the determinism.

Baring this in mind, whether the universe can be called deterministic or not largely depends on your perspective.

ronbyrne2005 wrote:

I am free to choose what to do this afternoon?

No, not as far as we can tell. There are no known physical mechanisms which could give rise to free will.

ronbyrne2005 wrote:

If not "free will" do I have "free choice" within my innate and learned abilities constraints etc?

I'm not quite sure what you mean by this, but if you are proposing a slightly restricted form of free will, the same problem applies.

ronbyrne2005 wrote:

As time is a physical entity i assume its massless, can it eventually rip apart?

Think of time as a distance. Does it make any sense to ask whether a distance has mass? Can you rip a distance apart? These questions just do not make sense in the context. Mass is not a property ascribed to time, and so it makes no sense to ask questions about whether or not it's mass is zero. It's much the same as asking what colour is gravity.

Time can be distorted by the presence of matter or energy, but it is neither.

ronbyrne2005 wrote:

I heard recent theories suggesting inflationary theory of the univesr may not be completely accurate.

The universe underwent, and continues to undergo rapid expansion. Of this we are certain.

The rates of expansion however, have turned out to be somewhat unexpected. In recent years we have discovered that the rate of expansion of the universe is actually increasing, rather than decreasing as was predicted by many theories. Perhaps this is what you are referring to.

ronbyrne2005

Professor_Fink wrote:

Ok, you seem to be including a whole load of seperate issues here, so I'll try to seperate them out:



This is a little hard to answer, and largely depends on what you mean by predestined. All of what we know about physics says that given some initial state, the state some finite time later is completely determined. In this way you can say that the universe appears to be completely deterministic.

The way humans experience the universe is a little different. When we measure a quantum system it appears to us to collapse in a probabilistic manner. So from our point of view it does not appear to be deterministic. If we treat the whole system (us and whatever system we are observing) as quantum mechanical, then we recover the determinism.

Baring this in mind, whether the universe can be called deterministic or not largely depends on your perspective.


No, not as far as we can tell. There are no known physical mechanisms which could give rise to free will.



I'm not quite sure what you mean by this, but if you are proposing a slightly restricted form of free will, the same problem applies.



Think of time as a distance. Does it make any sense to ask whether a distance has mass? Can you rip a distance apart? These questions just do not make sense in the context. Mass is not a property ascribed to time, and so it makes no sense to ask questions about whether or not it's mass is zero. It's much the same as asking what colour is gravity.

Time can be distorted by the presence of matter or energy, but it is neither.



The universe underwent, and continues to undergo rapid expansion. Of this we are certain.

The rates of expansion however, have turned out to be somewhat unexpected. In recent years we have discovered that the rate of expansion of the universe is actually increasing, rather than decreasing as was predicted by many theories. Perhaps this is what you are referring to.

Your not saying that every thing that happens to us as humans is predetermined though? It was'nt predestined that my parents would meet at a given point in time and I would be born at a given point in time?

Professor_Fink

ronbyrne2005 wrote:

Your not saying that every thing that happens to us as humans is predetermined though? It was'nt predestined that my parents would meet at a given point in time and I would be born at a given point in time?

I'm saying that it depends on your perspective. It largely depends on how you choose to interpret quantum mechanics. But, yes, physics does allow for another situation to have arisen.

ronbyrne2005

Say for instance every single thing in universe is predetermined including me typing this message here and you reading it etc. Would there be any way around this? Using quantum generated randomness to choose from a list of several alternative course for your life? Im probably, misinterpreting the implications of this determinism/free will lark on my life. Does extreme causal determinism make existence any less real or valid? Could the initial conditions of the big bang meant every single thing we experience and do is predtermined? Why the illusion of "free will" in such a scenario then? I personally beleive that somehow the uncertainty at differnet stages and levels of the universe mean that the universe is'nt complately predetermined/predestined and that we as humans have a cetain level of freedom to determine our future/destiny. Does the quantum mechanical effects recently observed in photosynthesis in plants ahve any implications for out universe hypothetically being 100% predetermined/predestined down to every thought ,feeling and action?

Professor_Fink

ronbyrne2005 wrote:

Say for instance every single thing in universe is predetermined including me typing this message here and you reading it etc. Would there be any way around this? Using quantum generated randomness to choose from a list of several alternative course for your life?

Certainly quantum mechanics allows for you to experience something else, but you do not have an active role in this. There is some randomness, but you do have any control over the outcome. From a scientific perspective, all current evidence points to free will being an illusion.

ronbyrne2005 wrote:

Im probably, misinterpreting the implications of this determinism/free will lark on my life. Does extreme causal determinism make existence any less real or valid? Could the initial conditions of the big bang meant every single thing we experience and do is predtermined? Why the illusion of "free will" in such a scenario then?

That seems like a very philosophical question. The rules of the universe, as we understand them, leave no room for free will. I don't see how causal determinism has any effect on what is real and what is not. That's a somewhat fluffy philosophical question that doesn't have an objective answer, since there is no infallible way of determining what is really real.

The initial conditions of the big bang certainly shape the relative probability of certain events occurring, but quantum mechanics adds an element of randomness to what we will observe.

As far as I can see, we experience free will because there is a causal link between our desires and our actions. If we decide to do something, and it is possible, we do it. So from our perspective we were able to do exactly what we wanted. If, however, the desire was determined by some other event, then you didn't actually have a free choice.

ronbyrne2005 wrote:

I personally beleive that somehow the uncertainty at differnet stages and levels of the universe mean that the universe is'nt complately predetermined/predestined and that we as humans have a cetain level of freedom to determine our future/destiny.

The first part of that statement is correct, but the claim that "humans have a certain level of freedom to determine our future/destiny" is scientifically indefensable.

ronbyrne2005 wrote:

Does the quantum mechanical effects recently observed in photosynthesis in plants ahve any implications for out universe hypothetically being 100% predetermined/predestined down to every thought ,feeling and action?

No. The effect in photosynthesis is interesting because it suggests that nature may have discovered how to exploit quantum computation, something that was previously believed not to be the case. It in no way changes the underlying physics.