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I would be very interested to hear anyone's simple explanation of gravity that does not include time? Gravity is acceleration. Acceleration is time dependent.Anyone???
Time in GR is difficult - you have worldlines and geodesics situated in a metric where time is just one of four dimensions (admittedly different sign). the worldline through spacetime of a test particle follows a route that is dependant on the curvature - it does not accelerate along this world line. the position and geometry of the worldline means that in 3d space an acceleration is measured, but in spacetime the particle "moves along" the worldline with its clock ticking normally.
Quote from: MikeS on 02/04/2012 17:16:43I would be very interested to hear anyone's simple explanation of gravity that does not include time? Gravity is acceleration. Acceleration is time dependent.Anyone???Gravity is more than acceleration I think. Because objects lying still on the ground with 0 acceleration are still subjected to gravity, otherwise they'd float. Acceleration can be used to simulate gravity, but it's not the same.But that's besides the point. I can't explain gravity without time..
Gravity for me is simple. It is the presence of matter, which is the presence of curvature and is the presence of acceleration within the equations of relativity; this much he is partially correct, I've never truely doubted that. It's linking it directly with time which troubles me. I don't see time and gravity as synonymous objects. In fact, I see change, I don't see time per se. Only through the eyes of a mere human being, I can extrapolate that time is highly subjective and something I project as a ''feeling of past and future'' on the world outside. None of which actually exist.
Quote from: Æthelwulf on 03/04/2012 13:01:21Gravity for me is simple. It is the presence of matter, which is the presence of curvature and is the presence of acceleration within the equations of relativity; this much he is partially correct, I've never truely doubted that. It's linking it directly with time which troubles me. I don't see time and gravity as synonymous objects. In fact, I see change, I don't see time per se. Only through the eyes of a mere human being, I can extrapolate that time is highly subjective and something I project as a ''feeling of past and future'' on the world outside. None of which actually exist.My previous two posts explain why I believe, you can't talk about gravity without talking about time, or more correctly without talking about time dilation.It is necessary to understand time dilation in order to understand gravity. Surely, if time did not exist, there could be no time dilation and therefore no such thing as gravity. Gravity exists and so does time.
Quote from: MikeS on 03/04/2012 16:01:40Quote from: Æthelwulf on 03/04/2012 13:01:21Gravity for me is simple. It is the presence of matter, which is the presence of curvature and is the presence of acceleration within the equations of relativity; this much he is partially correct, I've never truely doubted that. It's linking it directly with time which troubles me. I don't see time and gravity as synonymous objects. In fact, I see change, I don't see time per se. Only through the eyes of a mere human being, I can extrapolate that time is highly subjective and something I project as a ''feeling of past and future'' on the world outside. None of which actually exist.My previous two posts explain why I believe, you can't talk about gravity without talking about time, or more correctly without talking about time dilation.It is necessary to understand time dilation in order to understand gravity. Surely, if time did not exist, there could be no time dilation and therefore no such thing as gravity. Gravity exists and so does time.The dichotemy is much more complicated than that. If we were talking about time as being a local phenomenon, then yes this is true. If we are also talking time being experienced by Bradyons, or particles with mass, then time truely wasn't around until matter came out of the vacuum. But time for a universe, a universal global time vanishes. What is time then from the perspective of the universe if it does not exist globally? Is it only clocks moving below the speed of light that experience time, in which case the beginning of the universe certainly had no time and the end of the universe when all matter fields have returned to radiation fields, then the very future cone of our universe is also devoid of moving clocks. Simply put, you can't have time without matter ... these moving relativistic clocks which tick off real time.
ÆthelwulfI have answered most of your points in this thread.http://www.thenakedscientists.com/forum/index.php?topic=43056.0Quote from: Æthelwulf on 03/04/2012 21:04:42Quote from: MikeS on 03/04/2012 16:01:40Quote from: Æthelwulf on 03/04/2012 13:01:21Gravity for me is simple. It is the presence of matter, which is the presence of curvature and is the presence of acceleration within the equations of relativity; this much he is partially correct, I've never truely doubted that. It's linking it directly with time which troubles me. I don't see time and gravity as synonymous objects. In fact, I see change, I don't see time per se. Only through the eyes of a mere human being, I can extrapolate that time is highly subjective and something I project as a ''feeling of past and future'' on the world outside. None of which actually exist.My previous two posts explain why I believe, you can't talk about gravity without talking about time, or more correctly without talking about time dilation.It is necessary to understand time dilation in order to understand gravity. Surely, if time did not exist, there could be no time dilation and therefore no such thing as gravity. Gravity exists and so does time.The dichotemy is much more complicated than that. If we were talking about time as being a local phenomenon, then yes this is true. If we are also talking time being experienced by Bradyons, or particles with mass, then time truely wasn't around until matter came out of the vacuum. But time for a universe, a universal global time vanishes. What is time then from the perspective of the universe if it does not exist globally? Is it only clocks moving below the speed of light that experience time, in which case the beginning of the universe certainly had no time and the end of the universe when all matter fields have returned to radiation fields, then the very future cone of our universe is also devoid of moving clocks. Simply put, you can't have time without matter ... these moving relativistic clocks which tick off real time.There is little in the above that I do not agree with but my standpoint has not changed. I agree that prior to the existence of mass, there was no time. [Others might not agree on that as photons are supposed to create gravity in which case mass would not be necessary for the existence of time.] However, one could debate whether before ,time, distance , speed and geometry all became meaningful concepts did the universe exist or was it just the quantum vacuum void?Once the Universe became recognizable as the Universe I see no problem as to why there should not be a global or universal time in as much that it would be arrived at by taking an average of all of the local times. If time is the relationship between energy and mass in the universe and the percentage of these is constantly changing then the global or universal time dilation factor is also constantly changing. As stars are constantly converting some of their mass into energy then mass is decreasing as energy increases. So one could predict that time is contracting. A second now is shorter than a second in the cosmological past.
So let's see if I can lay this out some more.There is perhaps what we would call a ''fundamental time'' and a ''geometric time'' according to Markoupoulou. I add that fundamental time does not really exist, but a geometric time does for a late evolution of the universe. Here I add a new concept: ''induced time'', meaning time is really an emergent phenomenae late on the universes history which is why the universe is devoid of a fundamental time.
Quote from: Æthelwulf on 04/04/2012 12:21:45So let's see if I can lay this out some more.There is perhaps what we would call a ''fundamental time'' and a ''geometric time'' according to Markoupoulou. I add that fundamental time does not really exist, but a geometric time does for a late evolution of the universe. Here I add a new concept: ''induced time'', meaning time is really an emergent phenomenae late on the universes history which is why the universe is devoid of a fundamental time.I would argue that time is not an emergent phenomena 'late in the universes history. 'Late' implies that there was an earlier period. Without the backdrop of space-time there could have been no earlier period. Therefore, talking about what happened when and where before the creation of time is pretty meaningless. The history of the Universe can only date back to the creation of time.
Quote from: MikeS on 04/04/2012 15:24:49Quote from: Æthelwulf on 04/04/2012 12:21:45Late may imply there is an order. I may not be implying there could be time before matter - we may describe evolution in a different way. A purely static order before that order was broken, perhaps induced by a type of symmetry breaking.I can't agree with that. Late and order imply causality. Before the creation of time there was neither. Talking about before time is a minefield as we are limited by language. I have just used the word 'before' which is meaningless without time.I agree that something must have happened prior to the creation of matter but it happened outside of time and therefore outside the history of the Universe.Initially, as I understand it all that existed was energy in the void. Energy, travels instantaneously so any amount could appear here, there or anywhere at any time, if 'any amount', 'here', 'there', 'anywhere' and 'any time' were meaningful but they are not. What it does demonstrate is that in the Universe entropy rules. In the void without time there was no entropy.
Quote from: Æthelwulf on 04/04/2012 12:21:45Late may imply there is an order. I may not be implying there could be time before matter - we may describe evolution in a different way. A purely static order before that order was broken, perhaps induced by a type of symmetry breaking.I can't agree with that. Late and order imply causality. Before the creation of time there was neither. Talking about before time is a minefield as we are limited by language. I have just used the word 'before' which is meaningless without time.I agree that something must have happened prior to the creation of matter but it happened outside of time and therefore outside the history of the Universe.Initially, as I understand it all that existed was energy in the void. Energy, travels instantaneously so any amount could appear here, there or anywhere at any time, if 'any amount', 'here', 'there', 'anywhere' and 'any time' were meaningful but they are not. What it does demonstrate is that in the Universe entropy rules. In the void without time there was no entropy.
Late may imply there is an order. I may not be implying there could be time before matter - we may describe evolution in a different way. A purely static order before that order was broken, perhaps induced by a type of symmetry breaking.
Quote from: Æthelwulf on 04/04/2012 15:27:43Quote from: MikeS on 04/04/2012 15:24:49Quote from: Æthelwulf on 04/04/2012 12:21:45Late may imply there is an order. I may not be implying there could be time before matter - we may describe evolution in a different way. A purely static order before that order was broken, perhaps induced by a type of symmetry breaking.I can't agree with that. Late and order imply causality. Before the creation of time there was neither. Talking about before time is a minefield as we are limited by language. I have just used the word 'before' which is meaningless without time.I agree that something must have happened prior to the creation of matter but it happened outside of time and therefore outside the history of the Universe.Initially, as I understand it all that existed was energy in the void. Energy, travels instantaneously so any amount could appear here, there or anywhere at any time, if 'any amount', 'here', 'there', 'anywhere' and 'any time' were meaningful but they are not. What it does demonstrate is that in the Universe entropy rules. In the void without time there was no entropy.You seem to be forgetting however, that I have no problem with change. Orders may imply a change. Change does not necesserily mean time however. Take Barbours approach as a prime example. He says there is no time, only change.
Quote from: MikeS on 04/04/2012 15:24:49Quote from: Æthelwulf on 04/04/2012 12:21:45Late may imply there is an order. I may not be implying there could be time before matter - we may describe evolution in a different way. A purely static order before that order was broken, perhaps induced by a type of symmetry breaking.I can't agree with that. Late and order imply causality. Before the creation of time there was neither. Talking about before time is a minefield as we are limited by language. I have just used the word 'before' which is meaningless without time.I agree that something must have happened prior to the creation of matter but it happened outside of time and therefore outside the history of the Universe.Initially, as I understand it all that existed was energy in the void. Energy, travels instantaneously so any amount could appear here, there or anywhere at any time, if 'any amount', 'here', 'there', 'anywhere' and 'any time' were meaningful but they are not. What it does demonstrate is that in the Universe entropy rules. In the void without time there was no entropy.You seem to be forgetting however, that I have no problem with change. Orders may imply a change. Change does not necesserily mean time however. Take Barbours approach as a prime example. He says there is no time, only change.
ÆthelwulfJust because you keep quoting Barbours approach saying there is no time only change, does not make it true. So far I haven't seen the slightest evidence that time does not exist whereas there is plenty of evidence that it does.