Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie
Question on Spacetime
Options
Comments
-
That doesn't make sense. "Seconds" are a man-made measuring system just like the metric system, but time is perfectly equivalent to distance. You may as well be arguing that distance doesn't exist either.
Distance does not have any inherent existence, as it involves the measuring the distance between two completely arbitrary, and non-existent points. The points are non-existent that is, as one may decide to measure the distance between two real objects, using two completely arbitrary and imaginary points.
That doesn't mean that measuring distance isn't useful in our everyday lives, just like using our manmade, system of time, is useful. That does not mean that they actually exist though.How else do you quantity what you mean by change? Its the very definition of the word.
I'm sorry, but you're just not making an awful lot of sense.
an object changes with repsect to itself, not anything else. To measure the distance a car travels, one first records the details of the car in one location, and then compares it to the details of the same car in a changed position.
with regard to "time", what happens is that some phenomenon is taken as a standard unit, and change is measured against that standard unit, to guage the "time variable".
the measurement of speed in km/h is the measurement of km relative to a certain degreee of the earths rotation.0 -
I was writing a response to you, but have noticed some things you said to podge. I feel my post is more illuminating if I directly respond to them.Distance does not have any inherent existence, as it involves the measuring the distance between two completely arbitrary, and non-existent points.
That doesn't mean that measuring distance isn't useful in our everyday lives, just like using our manmade, system of time, is useful. That does not mean that they actually exist though.
This is at least progress, as you presumably accept that time is no more or less physical than distance. It also means that reading Julian Barbour's work won't be of any benefit to you.
Though I think you're confusing qantifiable standards with qualifiable properties. The metre as a unit of length is entirely arbitrary, as is the second. But you could never define the metre in terms of the second, or the second in terms of the metre, as they are both standards of different properties (spatial distance and temporal distance).
So I agree that measurement systems are entirely artificial, but the things they are applied to are not.an object changes with repsect to itself, not anything else.
The rate of change of some property with respect to itself is 1, so it cannot be speed. The rate of change of your position with respect to your position, for example, is 1 no matter how fast you walk, which is why you'll never walk away from yourself.To measure the distance a car travels, one first records the details of the car in one location, and then compares it to the details of the same car in a changed position.
So you accept that there is one location, and another, different location. Distance is the difference between these locations. The speed of the car would be the change in these locations with respect to time.With regard to "time", what happens is that some phenomenon is taken as a standard unit, and change is measured against that standard unit, to guage the "time variable".
the measurement of speed in km/h is the measurement of km relative to a certain degreee of the earths rotation.
Yes, the duration of some phenomenon is taken as a standard unit. If we use the earth's rotation to measure the speed of a car, then we are measuring the rate of change of positon of the car with respect to the earth's rotation.
But the earth's rotation itself is an angular change with respect to time, which is why it is a valid standard. If we tried to use some standard that was not a change with respect to time, it would make no sense.0 -
I was writing a response to you, but have noticed some things you said to podge. I feel my post is more illuminating if I directly respond to them.
This is at least progress, as you presumably accept that time is no more or less physical than distance. It also means that reading Julian Barbour's work won't be of any benefit to you.
Though I think you're confusing qantifiable standards with qualifiable properties. The metre as a unit of length is entirely arbitrary, as is the second. But you could never define the metre in terms of the second, or the second in terms of the metre, as they are both standards of different properties (spatial distance and temporal distance).
So I agree that measurement systems are entirely artificial, but the things they are applied to are not.
The contention is that time is a measurement system.The rate of change of some property with respect to itself is 1, so it cannot be speed. The rate of change of your position with respect to your position, for example, is 1 no matter how fast you walk, which is why you'll never walk away from yourself.
Indeed, the issue is that change is measured by recording the details of an object in a particular state/location and then comparing it against the details of the same object, in a different state/location.
This ultimately means that it is a comparison of non-realirty with reality, as the object only exists in one place, so as soon as it moves/changes from its original position, the recorded details no longer accord with reality.So you accept that there is one location, and another, different location. Distance is the difference between these locations. The speed of the car would be the change in these locations with respect to time.
The issue again is, that in reality there is actually only one location, as there is only one car, that exists in only one location. The details of the cars original location, cease to be representative of reality when it moves. This means that what is compared are the imaginary details of the cars original location, against it's current location.Yes, the duration of some phenomenon is taken as a standard unit. If we use the earth's rotation to measure the speed of a car, then we are measuring the rate of change of positon of the car with respect to the earth's rotation.
Indeed, and there is no need for the superfluous concept of time. It is just like taking a metre, as a standard unit, and measuring distance. Just because we come up with a value for the distance, it does not mean that a metre, or indeed the metric system have any inherent existence.
Similiarly, if we take the microwave emissions of electrons as the standard unit [of the measurement system called time], and measure the change in an object, it is the microwave emissions that have some inherent existence, not the superfluous concept of time.
For example, if one were to take the beeping noise from a fire alarm as a standard unit, and then wanted to measure how long it took them to walk across the room.
The measurement would be X no. of beeps, which could then be compared with another persons measurement of Y no. of beeps.
Time does not come into it.But the earth's rotation itself is an angular change with respect to time,
Apologies, but as far as I can see, that is a non-sequitur. Hiow is the earth's rotation a change with repsect to time? Where does time come into it?
The earth's rotation is a change with respect to it's [former] self.
[quote=Morbert;64095362 which is why it is a valid standard. If we tried to use some standard that was not a change with respect to time, it would make no sense.[/quote]
Again, how is any standard unit a change with respect to time?0 -
mangaroosh wrote: »The contention is that time is a measurement system.
But you are not properly defining what we are measuring. You have said, for example, that the second is a measurement of change, but you have not defined what that change with is respect to. Change can be with respect to a variety of parameters. Change with respect to itself does not make sense, for reasons mentioned before. Change with respect to its former self also makes no sense, for reasons I will address below. The only change that can be used to standardise our time measurement system is change with respect to time. This is why we can define the second in terms of rotation (something that changes with respect to time), but not local government (something that changes with respect to location).Indeed, the issue is that change is measured by recording the details of an object in a particular state/location and then comparing it against the details of the same object, in a different state/location.
And that is not enough. A car can get from point A to point B with a variety of speeds. These speeds cannot be defined simply by a difference in position. It needs to be defined by the rate of change of position with respect to something.This ultimately means that it is a comparison of non-realirty with reality, as the object only exists in one place, so as soon as it moves/changes from its original position, the recorded details no longer accord with reality.
The issue again is, that in reality there is actually only one location, as there is only one car, that exists in only one location. The details of the cars original location, cease to be representative of reality when it moves. This means that what is compared are the imaginary details of the cars original location, against it's current location
The idea of an absolute present is an idea that is no longer held by scientists. My present can include your fututre via simultaneity effects. Say there are two lights in front of you, 2 miles apart. In your present, both lights may go off at the same time. In my present, one light may go off, and the other may go off in the future. In fact, it is even possible for the order of events to reverse!Indeed, and there is no need for the superfluous concept of time. It is just like taking a metre, as a standard unit, and measuring distance. Just because we come up with a value for the distance, it does not mean that a metre, or indeed the metric system have any inherent existence.
Yes, you are using an arbitrary standard unit (metre) to measure something that is not arbitrary (distance). Take a tape measurer as a simple example. The number on the spool closest to the casing changes with respect to the length of the tape unravelled. We have a change with respect to distance, used to standardise an arbitrary unit of distance.Similiarly, if we take the microwave emissions of electrons as the standard unit [of the measurement system called time], and measure the change in an object, it is the microwave emissions that have some inherent existence, not the superfluous concept of time.
What is the difference between something that changes, and something that remains constant?For example, if one were to take the beeping noise from a fire alarm as a standard unit, and then wanted to measure how long it took them to walk across the room.
The measurement would be X no. of beeps, which could then be compared with another persons measurement of Y no. of beeps.
Time does not come into it.
The number of beeps, like the angular position of the earth, changes with respect to time, which is why it can be used as a standard. You could not use a change with respect to distance (such as the reading on a tape measurer) as a standard unit because you would no longer be standardising a time measurement.Apologies, but as far as I can see, that is a non-sequitur. Hiow is the earth's rotation a change with repsect to time? Where does time come into it?
The earth's rotation is a change with respect to it's [former] self.
Close but no cigar. Though perhaps this is my fault, as I have not defined what I mean by "with respect to". What you are referringto is the difference between the earth's angular position in the present and some former self, but for this angular distance to be used as a measurement of something, it must change with respect to that thing. Angular distance between the earth and it's former self does not change with respect to position on the earth's surface, for example, so it could not be used to measure your position on the earth's surface. It does, however, change with respect to time, so it can be used as a standard measurement of time.Again, how is any standard unit a change with respect to time?
If it is a change, but not a change with respect to anything that isn't time. Change in the earth's rotation, for example, is not necessarily a change with respect to anything that isn't time, but it is still a change, so it must be with respect to something. We call that something time.0 -
But you are not properly defining what we are measuring. You have said, for example, that the second is a measurement of change, but you have not defined what that change with is respect to. Change can be with respect to a variety of parameters. Change with respect to itself does not make sense, for reasons mentioned before. Change with respect to its former self also makes no sense, for reasons I will address below.
I take your point about change with respect to self, and accept that the concept of change with respect to a former self is inaccurate, hopefully it can be clarified further.
With regard to change being with respect to something, the change in an object, is compared against a naturally occuring phenomenon, which is taken to be the standard unit of comparison.
With regard to the 24hr clock, what was originally measured was the position of the sun in the sky with respect to the earth.
For other changes, they are with respect to some other naturally occuring phenomenon, e.g the decay of muon, where the decay of muon is taken as the [arbitrary] standard unit, against which, things are compared.The only change that can be used to standardise our time measurement system is change with respect to time. This is why we can define the second in terms of rotation (something that changes with respect to time), but not local government (something that changes with respect to location).
The changes that are used to standardise our time measurement system are naturally occuring phenomena, which are taken as the standard unit, against which all other changes are compared.And that is not enough. A car can get from point A to point B with a variety of speeds. These speeds cannot be defined simply by a difference in position. It needs to be defined by the rate of change of position with respect to something.
Indeed, and that is the standard units of measurement. In the example of a car, the rate of change is compared against the standardised unit of the hour.
The hour however is simply the change of the position of the sun in the sky, with respect to [a position on] the earth.The idea of an absolute present is an idea that is no longer held by scientists. My present can include your fututre via simultaneity effects. Say there are two lights in front of you, 2 miles apart. In your present, both lights may go off at the same time. In my present, one light may go off, and the other may go off in the future. In fact, it is even possible for the order of events to reverse!
This is one of the great achievements of relativity, its ability to predict and explain how we will perceive the universe, it may also, however, be one of its fundamental limitations.
The issue is perhaps with the concept that all inertial frames of reference are equal. This of course is generally speaking true, with regard to what we perceive. However, depending on what is asked, or what is to be known, it may not be.
I presume the above is a rather simplified version of something like the doppler effect. Forgive my basic understanding, as I am basing my understanding on a number of documentaries that I have seen that explains the doppler effect.
If we take the example of the two lightning rods, with the man on the train and the man standing still, where lightning strikes both rods and both men perceive it differently - one seeing the lightning striking in a different order. Here relativity is superb in its explanation of what both men perceive, and all intertial frames of reference are indeed equal, because how one perceives such an event is not necessarily the truth of what happened.
With respect to the question of whether the lightning struck both rods at the same time, all inertial frames are no longer equal, as it is not a question of what each man sees. In this case, the frame of reference of each rod is superior to the frame of reference of each man - for this particular question.
So the idea of us being able to perceive the absolute present, based on vision, is indeed erroneous.Yes, you are using an arbitrary standard unit (metre) to measure something that is not arbitrary (distance). Take a tape measurer as a simple example. The number on the spool closest to the casing changes with respect to the length of the tape unravelled. We have a change with respect to distance, used to standardise an arbitrary unit of distance.
Can you clarify that a bit further, I'm just trying to make more sense of it, but to respond, the number on the tape is simply a tally of the standard units of measurement, which themselves are entirely arbitrary.
In a sense it would be like saying how long is a metre, or how does one measure a metre? It isn't the distance that dictates the number of metres, but rather the standard definition of a metre, applied to an arbitrary distance.
So if we take an unmarked tape (that is to become a tape measure), it isn't the distance of the unrolled tape, that will dictate where the markings go, rather the arbitrary units of measure.What is the difference between something that changes, and something that remains constant?
How do you mean?The number of beeps, like the angular position of the earth, changes with respect to time, which is why it can be used as a standard.
Can you explain why this is true, because it appears to be a non-sequitur.You could not use a change with respect to distance (such as the reading on a tape measurer) as a standard unit because you would no longer be standardising a time measurement.
The thing is, that time doesn't actually come into it, other than to assume that the naturally occuring standard units, are a measurement of the phenomenon of time. This is the primary assumption which is being questioned.
The natural phenomena that are taken as the standard units, do not measure anything in and of themselves. It is "with respect to" them, that change is measured.
If one takes an egg-timer as the standard unit of measurement, change would be measured against the emptying of the top compartment, into the bottom compartment.Close but no cigar. Though perhaps this is my fault, as I have not defined what I mean by "with respect to". What you are referringto is the difference between the earth's angular position in the present and some former self, but for this angular distance to be used as a measurement of something, it must change with respect to that thing. Angular distance between the earth and it's former self does not change with respect to position on the earth's surface, for example, so it could not be used to measure your position on the earth's surface.
apologies, that was my misrepresentation that lead to that confusion. The angular rotation of the earth is more than likely with repsect to the sun, or it could be measured against other planets.It does, however, change with respect to time, so it can be used as a standard measurement of time.
Again, how is this true, because it appears to be a non-sequiturIf it is a change, but not a change with respect to anything that isn't time. Change in the earth's rotation, for example, is not necessarily a change with respect to anything that isn't time, but it is still a change, so it must be with respect to something. We call that something time.
That something is the sun (or perhaps other planets)0 -
Advertisement
-
mangaroosh wrote: »With regard to change being with respect to something, the change in an object, is compared against a naturally occuring phenomenon, which is taken to be the standard unit of comparison.
The changes that are used to standardise our time measurement system are naturally occuring phenomena, which are taken as the standard unit, against which all other changes are compared.
For other changes, they are with respect to some other naturally occuring phenomenon, e.g the decay of muon, where the decay of muon is taken as the [arbitrary] standard unit, against which, things are compared.
That something is the sun (or perhaps other planets)
Yes, but only specific naturally occuring phenomena can be used to standardise our measurement of time. What qualifies a phenomena as appropriate is it must change with respect to time.With regard to the 24hr clock, what was originally measured was the position of the sun in the sky with respect to the earth.
We need to be careful how we parse things. The position of the sun does not change with respect to the earth. Instead, the position of the sun with respect to the earth changes with respect to time. This is why such a measurmement could be used to define a day. If the position of the sun in the sky with respect to the earth did not change with respect to time (i.e. If it hung in the sky, unchanging like Charon does on Pluto), then it could not be used as a measure of time.
Coincidentally, the position of the sun with respect to the earth is an example of an observation that also changes with respect to your position on the earth. So, all other parameters being constant, you could use it to define spatial units on the earth surface.Indeed, and that is the standard units of measurement. In the example of a car, the rate of change is compared against the standardised unit of the hour.
Which is defined by some phenomenon that changes with respect to time.This is one of the great achievements of relativity, its ability to predict and explain how we will perceive the universe, it may also, however, be one of its fundamental limitations.
The issue is perhaps with the concept that all inertial frames of reference are equal. This of course is generally speaking true, with regard to what we perceive. However, depending on what is asked, or what is to be known, it may not be.
I presume the above is a rather simplified version of something like the doppler effect. Forgive my basic understanding, as I am basing my understanding on a number of documentaries that I have seen that explains the doppler effect.
If we take the example of the two lightning rods, with the man on the train and the man standing still, where lightning strikes both rods and both men perceive it differently - one seeing the lightning striking in a different order. Here relativity is superb in its explanation of what both men perceive, and all intertial frames of reference are indeed equal, because how one perceives such an event is not necessarily the truth of what happened.
I'm glad you mentioned the doppler effect, as it can help clarify how fundamental simultaneity effects are.
The doppler effect, as you probably know will result in an apparent disagreement in frequency between two observers moving at different velocities relative to the source. To understand how their readings are related to one another they only need to understand how their reference frames are related under "Galilean transformations". In laymans terms, this amounts to them sitting down and saying "This effect is weird, but if we acknowledge that in one reference frame the source is moving and in another reference frame the source is stationary, as is indicated by these mathematical relationships (Galilean transformations), then we can understand the different frequency readings.".
With simultaneity effects, however, no reconciliation is possible unless Galilean transformations are erroneous and we consider Lorentz transformations instead. I.e. both observers sit down and acknowledge that the only way their readings can be reconciled is if both events actually occured (not just 'detected') at different times in different reference frames, as indicted by the Lorentz transformations.
So it must be stressed that it's not a case of two observers detecting something at diferent moments, and hence concluding different times. It's a case of two observers detecting at different moments, sitting down and comparing readings, and concluding that the only way both readings can be reconciled is if they admit that "the present" was not the same for both of them.
This inevitably raises the question, "Maybe one reference frame is preffered then. What if observed events in the moving observer's reference frame are skewed due to some force related to speed?" You have indeed raised the question, and I will address that next.With respect to the question of whether the lightning struck both rods at the same time, all inertial frames are no longer equal, as it is not a question of what each man sees. In this case, the frame of reference of each rod is superior to the frame of reference of each man - for this particular question.
So the idea of us being able to perceive the absolute present, based on vision, is indeed erroneous.
Here, you have suggested that the rods' frame of reference is superior to that of the man on the station. The problem with this assertion, however, is a preferred reference frame is entirely undetectable. This is similar to your objection against time, only much more fundamental. Time cannot be directly observed, but it can be inferred from change with respect to it. A preferred reference frame cannot even be inferred. There is nothing which tells us that one frame of reference (The rods') is superior to another frame of reference. So if we cannot infer a preferred frame of reference, then why postulate it at all?Can you clarify that a bit further, I'm just trying to make more sense of it, but to respond, the number on the tape is simply a tally of the standard units of measurement, which themselves are entirely arbitrary.
I'll put it another way. The reading on the tape is a function of the distance of tape unravelled. By that I mean the reading on the tape depends on the distance of tape unravelled. If you've unravelled 2 metres, then the tape will indicate the number "2" on the metre side. 3 metres, "3"; 4 metres, "4" etc. If the length of tape varies, the reading varies. We therefore say that the reading varies (changes) with respect to the length of tape. Similarly the angular position of the earth, or the position of the sun with respect to the earth "varies" with respect to the "temporal length"/time considered.In a sense it would be like saying how long is a metre, or how does one measure a metre? It isn't the distance that dictates the number of metres, but rather the standard definition of a metre, applied to an arbitrary distance.
Yes, I fully accept that the metre, like the second, is arbitrary and not inherently physical. But what they are actually indicative of is not. We can measure distance by recording the change of something (Trundle wheel, number of notches on a rule, tape measurer) with respect to distance. We can measure time by recording the change of something (Angular position, position of the sun, number of periodic beeps) with respect to time. In short, the unit is arbitrary, the dimension the unit is applied to is not.So if we take an unmarked tape (that is to become a tape measure), it isn't the distance of the unrolled tape, that will dictate where the markings go, rather the arbitrary units of measure.
I agree. Time, like distance, in no way dictates the specific markings we use. But it is the very existence of time and space that allows us to make arbitrary markings.Can you explain why this is true, because it appears to be a non-sequitur.
I don't think you mean non-sequitur. Or are you disputing the claim that, if something changes with respect to time, then it follows that it can be used to measure time?The thing is, that time doesn't actually come into it, other than to assume that the naturally occuring standard units, are a measurement of the phenomenon of time. This is the primary assumption which is being questioned.
The natural phenomena that are taken as the standard units, do not measure anything in and of themselves. It is "with respect to" them, that change is measured.
If one takes an egg-timer as the standard unit of measurement, change would be measured against the emptying of the top compartment, into the bottom compartment.
Again, I must stress that I fully accept that standard units are convention. They are a convention for quantifying things. What I am saying is the metre and the second are arbitrary quantities of things that are qualitatively different. A metre can be converted to inches, miles, lightseconds, feet etc. because they are all arbitrary quantities of the same thing. A metre cannot, however, be converted to seconds because they are arbitrary quantities of different things.0 -
Yes, but only specific naturally occuring phenomena can be used to standardise our measurement of time. What qualifies a phenomena as appropriate is it must change with respect to time.
How do these naturally occuring phenomena "change with respect to time"? How do the microwave emissions of changing electrons "change with respect to time", how does muon decay "with respect to time"?We need to be careful how we parse things. The position of the sun does not change with respect to the earth. Instead, the position of the sun with respect to the earth changes with respect to time.
Can this be qualified with an explanation, as to how this change occurs "with respect to time"?This is why such a measurmement could be used to define a day. If the position of the sun in the sky with respect to the earth did not change with respect to time (i.e. If it hung in the sky, unchanging like Charon does on Pluto), then it could not be used as a measure of time.
That is circular reasoningCoincidentally, the position of the sun with respect to the earth is an example of an observation that also changes with respect to your position on the earth. So, all other parameters being constant, you could use it to define spatial units on the earth surface.
Won't challenge that, as it is a separate issue.Which is defined by some phenomenon that changes with respect to time.
Which is the phenomenon that changes with respect to time, and how does it change with respect to time?I'm glad you mentioned the doppler effect, as it can help clarify how fundamental simultaneity effects are.
The doppler effect, as you probably know will result in an apparent disagreement in frequency between two observers moving at different velocities relative to the source. To understand how their readings are related to one another they only need to understand how their reference frames are related under "Galilean transformations". In laymans terms, this amounts to them sitting down and saying "This effect is weird, but if we acknowledge that in one reference frame the source is moving and in another reference frame the source is stationary, as is indicated by these mathematical relationships (Galilean transformations), then we can understand the different frequency readings.".
With simultaneity effects, however, no reconciliation is possible unless Galilean transformations are erroneous and we consider Lorentz transformations instead. I.e. both observers sit down and acknowledge that the only way their readings can be reconciled is if both events actually occured (not just 'detected') at different times in different reference frames, as indicted by the Lorentz transformations.
So it must be stressed that it's not a case of two observers detecting something at diferent moments, and hence concluding different times. It's a case of two observers detecting at different moments, sitting down and comparing readings, and concluding that the only way both readings can be reconciled is if they admit that "the present" was not the same for both of them.
I won't argue on the basis of the maths, but with regard to the [presumably basic] Doppler example, of lightning striking two poles, regardless of what both observers may have seen, the question of whether the lightning struck both poles at the same moment, is answerable from the point of view of the bolts of lighning and/or the poles.
Also, both observers can only experience things in the present. They may observe events in what appear to be slightly different time frames, but the only "time frame" that either of them can operate in, is the present.This inevitably raises the question, "Maybe one reference frame is preffered then. What if observed events in the moving observer's reference frame are skewed due to some force related to speed?" You have indeed raised the question, and I will address that next.
Here, you have suggested that the rods' frame of reference is superior to that of the man on the station. The problem with this assertion, however, is a preferred reference frame is entirely undetectable. This is similar to your objection against time, only much more fundamental.
The preferred reference frame is dependent on what is being measured, or asked. With regard to the Doppler lightning/pole example above, the preferred reference frame is easily detectable - it is either the bolts of lightning or the poles, with the poles being, the presumably easier detected, reference frame.Time cannot be directly observed, but it can be inferred from change with respect to it.
Time can only be inferred from change with respect to time. Again, circular reasoning.A preferred reference frame cannot even be inferred. There is nothing which tells us that one frame of reference (The rods') is superior to another frame of reference. So if we cannot infer a preferred frame of reference, then why postulate it at all?
If the question is, did the lightning hit both poles at the same moment [in the measuring system called time], then the preferred reference frame is both the lighning and the rods, with the rods being eaier to detect than the lightning (presumably).
The preferred reference frame is inferred from the question, or what is being measured.I'll put it another way. The reading on the tape is a function of the distance of tape unravelled. By that I mean the reading on the tape depends on the distance of tape unravelled. If you've unravelled 2 metres, then the tape will indicate the number "2" on the metre side. 3 metres, "3"; 4 metres, "4" etc. If the length of tape varies, the reading varies. We therefore say that the reading varies (changes) with respect to the length of tape.
The reading on the tape doesn't change, the numbers on the tape remain constant, as they are already printed on it. They simply number the graduations on it. Hopefully this point will be clarified a bit further below, with the example of the rope.Similarly the angular position of the earth, or the position of the sun with respect to the earth "varies" with respect to the "temporal length"/time considered.
Again, how does it change with respect to the "temproal length"?Yes, I fully accept that the metre, like the second, is arbitrary and not inherently physical. But what they are actually indicative of is not.
The question then is what are they indicative of. If we take a length of rope for example. If we attempt to measure the rope, what we are actually doing, is translating its length into something else.
If the rope is 1km long for example, what we are actually saying is that the rope is equal to a certain fraction of the meridian of the earth, which itself is just an imaginary line, and has no inherent existence.
The issue is that the rope itself may indeed exist, but to say that it is 1km long is simply to express its length in [standardised] imaginary terms. There could be a separate discussion on the concept of length.We can measure distance by recording the change of something (Trundle wheel, number of notches on a rule, tape measurer) with respect to distance.
It is circular reasoning to say that distance is measured, by recording change with respect to distance.We can measure time by recording the change of something (Angular position, position of the sun, number of periodic beeps) with respect to time.
Again, it is circular reasoning to say that time can be measured by recording change with respect to time.In short, the unit is arbitrary, the dimension the unit is applied to is not.
The issue is with what these measurement systems are applied to. The concept of length, with regard to the piece of rope, is the application of a measurement system to a physical object - the rope.
While the rope may have some inherent existence, it doesn't mean that the spacial dimension has inherent existence, as that would be a non-sequitur.
With regard to the concept of distance, is the application of the measurement system to an imaginary line between two imaginary points - for example, any point on the earth to a point on any other planet or star.
We may be able to imagine this line, and then apply the measurement system, but that does not mean that the line, or indeed the spacial dimension, has any inherent existence.
With regard to time, it is the application of the measurement system to the change in a physical object, i.e. the comparison of the change of one object to the change in another (which is taken as the standard unit of comparison). Both physical objects may have inherent existence, but that does not mean that time has inherent existence.
I agree. Time, like distance, in no way dictates the specific markings we use. But it is the very existence of time and space that allows us to make arbitrary markings.I don't think you mean non-sequitur. Or are you disputing the claim that, if something changes with respect to time, then it follows that it can be used to measure time?
To suggest that only something which changes with respect to time, can be used as a measurement of time, is circular reasoning, unless it can be shown how the phenomenon changes with respect to time.Again, I must stress that I fully accept that standard units are convention. They are a convention for quantifying things. What I am saying is the metre and the second are arbitrary quantities of things that are qualitatively different. A metre can be converted to inches, miles, lightseconds, feet etc. because they are all arbitrary quantities of the same thing. A metre cannot, however, be converted to seconds because they are arbitrary quantities of different things.
The issue is what exactly these conventions are actually quantifying. Lenght quantifies a physical object e.g. a length of rope, which means that the physical object has some inherent existence, not the spacial dimension.
Distance is the measurement of an imaginary line between two imaginary points.
Time is the measurement of change in physical objects, or more pointedly, the comparison of the change of one object, to the change in another object, which is taken as a standardised unit of measurement.
Both the physical objects may have some inherent existence, time does not.0 -
I appluad Morbert's patience, but I feel its ultimately pointless.Time can only be inferred from change with respect to time. Again, circular reasoning.
Its not circular reasoning, you're just framing it poorly. There is change with repect to something - that something is time.
For example - this discussion started bloody ages ago.Both the physical objects may have some inherent existence, time does not.
You can argue this all you want, but ultimately all physics we know of treats time as having an inherent existence and all physics we know of works.the preferred reference frame is easily detectable
Similarly, you can argue this point all you want, but it is undeniably and beyond question completely wrong. There is no such thing as a preferred reference frame and any theory or idea that requires one is wrong.0 -
I appluad Morbert's patience, but I feel its ultimately pointless.
Its not circular reasoning, you're just framing it poorly. There is change with repect to something - that something is time.
Simply asserting that there is change with respect to something, does not make it so. Explain how there is change with respect to something.
Also, is this "something", with regard to which change [supposedly] occurs, only measureable (or inferrable) by phenomena which supposedly change with respect to that "something"?
If the change in an object is to be measured, then it is simply compared to another object, which is taken as a standard unit of comparison.
The atomic clock for example, the atoms (or electrons) may have some inherent existence (be that in the form of vibrating strings or whatever). The change in an object is then measured against that.
The change in the electrons is taken as the standard unit of comparison, they do not measure anything themselves, as it is they that is being measured.For example - this discussion started bloody ages ago.
Yet all contributions have been in the presentYou can argue this all you want, but ultimately all physics we know of treats time as having an inherent existence and all physics we know of works.
Indeed, but all physics doesn't treat time in the same manner, to the extent that the two primary physical theories - Relativity and Quantum Mechanics - treat time in very different ways.
One such postulation as to how to reconcile the difference, is to realise that time is non-existent.
Of course, to say that because time is treated as being real in physical theories, yet treated differently by the two main theories, doesn't mean that time is real, as physical theories are subject to change.
Just as physical theories changed when it was discovered that the earth was not at the centre of the universe, or that it was not flat, so too can physical theories change when it is realised time does not have any inherent existence.Similarly, you can argue this point all you want, but it is undeniably and beyond question completely wrong. There is no such thing as a preferred reference frame and any theory or idea that requires one is wrong.
I won't argue too much on this point, as I am not totally sure if my understanding of a "reference frame" is correct, however, with regard to the doppler example above, if the question is "did the lighning hit both poles at the same time (the measurement system that is), then it would seem that the reference frame of the poles (and lighning bolts) are preferred - as inferred by the question being asked.
Regardless, it doesn't change the fact that events in all reference frames exist can only be experienced in the present moment, even if the subjective perception, of persons in those reference frames, suggests that events appear to occur in a different sequence.0 -
mangaroosh wrote: »Yet all contributions have been in the present
No, all contributions were made in the present at the time they were made. They are now in the past.Indeed, but all physics doesn't treat time in the same manner, to the extent that the two primary physical theories - Relativity and Quantum Mechanics - treat time in very different ways.
No they don't, they treat it in exactly the same way. If this is the basis for your argument then I'm afraid you're on the complete wrong track.I won't argue too much on this point, as I am not totally sure if my understanding of a "reference frame" is correct, however, with regard to the doppler example above, if the question is "did the lighning hit both poles at the same time (the measurement system that is), then it would seem that the reference frame of the poles (and lighning bolts) are preferred - as inferred by the question being asked.
The question "did the lightning hit both poles at the same time" still does not give a preferred reference frame. The answer is different in different reference frames and all answers are equally valid. The answer is different for someone orbiting the earth or someone standing beside the poles. Both answers are equally valid.0 -
Advertisement
-
We live in a 3D world. To us time is not a physical manifestation. Time exists in a conceptal sense, not a physical sense.And I think a lot interpret the use of time as being evidence that it does exist, physically that is. It doesnt (imo I might add). However, if there were no universe, no expansion, then we wouldnt be here to argue its existance, cos there'd be no progression through time and time wouldnt exist either.
As regards the maths and formulas, then yes, it would affect them. They wouldnt exist. We are a result of the birth of the universe (big bang theory) and if that didnt occur, then neither would expansion (universe isnt contracting) and we wouldnt be here either.
And if time is a physical component of this universe, then where are the photographs to prove it.
Time plays an inherent role in everybodies life,and is a very useful tool in astrophysics, but that doesnt mean it actually exists, in the sense that a lot seem to think.0 -
No, all contributions were made in the present at the time they were made. They are now in the past.
They are not now in the past, the posts exist in the present, and have always only existed in the present. One may have a memory of having written the post, but that memory exists only in the persons head, and not in reality.No they don't, they treat it in exactly the same way. If this is the basis for your argument then I'm afraid you're on the complete wrong track.
Apologies, I was under the impression that there was an issue commonly referred to as "the problem of time" in physics, because "time is absolute in standard quantum theory and dynamical in
general relativity. The combination of both theories into a theory
of quantum gravity leads therefore to a “problem of time”.".
Although, that is not the basis for the argument. The basis for the argument is primarily that the present moment is all that exists, has existed and ever will exist.
This is supported by what appears to be a serious lack of evidence to support the existence of time.The question "did the lightning hit both poles at the same time" still does not give a preferred reference frame. The answer is different in different reference frames and all answers are equally valid. The answer is different for someone orbiting the earth or someone standing beside the poles. Both answers are equally valid.
If the question is, did the lighning hit both poles at the same time, then the poles and the lightning bolts are the preferred reference frames. If the question is, how would this event appear to observers in different reference frames, then all reference frames are equal.
There is the obvious issue that someone travelling away from the poles will observe something different because of the extra distance that light has to travel to hit that persons field of vision.
Although, I'm sure that is something that has been considered in depth, and again is not the basis for the argument.
The discussion could easily be resolved by answering a couple of basic questions.
If change occurs with resepect to time, then explain how.
Also, if time exists, what is used to detect/measure/test for it?0 -
mangaroosh wrote: »If the question is, did the lighning hit both poles at the same time, then the poles and the lightning bolts are the preferred reference frames. If the question is, how would this event appear to observers in different reference frames, then all reference frames are equal.
You can say it as many times as you want, but it will remain wrong. There is no such thing as a preferred reference frame.0 -
You can say it as many times as you want, but it will remain wrong. There is no such thing as a preferred reference frame.
Fair enough, I won't argue that point any further
EDIT: the other questions remain:
If change occurs with resepect to time, then explain how.
Also, if time exists, what is used to detect/measure/test for it?0 -
mangaroosh wrote: »
If change occurs with resepect to time, then explain how.
Also, if time exists, what is used to detect/measure/test for it?
Check out entropy for a thermodynamic explaination of time.
Time is not a something we can see or prove with our senses. That leaves us with experimental proof only. GR includes time (non absolute) and passed all experimental tests.0 -
Check out entropy for a thermodynamic explaination of time.
Time is not a something we can see or prove with our senses. That leaves us with experimental proof only. GR includes time (non absolute) and passed all experimental tests.
Cheers (genuinely). I was familiar with entropy, but just checked out the wiki entry on it, to be sure.
The issue with entropy as evidence for the existence of time, is that it assumes time exists, from the outset. The fact that a system tends towards increasing disorder (or remains the same) is not evidence that time exists, rather that a system tends towards increasing disorder.
The question I would have with regard to the experimental test for time in GR, would be, what was used to test for time in those experiments? What test was carried out that returned a positive result to show that time exists?0 -
mangaroosh wrote: »The issue with entropy as evidence for the existence of time, is that it assumes time exists, from the outset. The fact that a system tends towards increasing disorder (or remains the same) is not evidence that time exists, rather that a system tends towards increasing disorder.
Define "tends."0 -
mangaroosh wrote: »The issue with entropy as evidence for the existence of time, is that it assumes time exists, from the outset. The fact that a system tends towards increasing disorder (or remains the same) is not evidence that time exists, rather that a system tends towards increasing disorder.
For a system to tend towards anything time has to exist!The question I would have with regard to the experimental test for time in GR, would be, what was used to test for time in those experiments? What test was carried out that returned a positive result to show that time exists?
Every single one of them. Any test of GR that works - which is all of them - tells us that time exists. It is a fundamental aspect of GR.0 -
I dont think that people assume that time exists. We perceive our reality as a sequence of events which are occuring in an linear order - the name we have for this and its is time. Initially it was seen as an absolute but this has been overthrown by relativity and now we understand that time is not an absolute but relative.
There were no tests for time in GR experiments. It was another variable in the equation.
You seem to be looking for an absolute clock but there is none. We measure the passage of time in S.I. unit of a second and that is linked to say an atomic clock.0 -
mangaroosh wrote: »How do these naturally occuring phenomena "change with respect to time"? How do the microwave emissions of changing electrons "change with respect to time", how does muon decay "with respect to time"?
Asking how something changes with respect to time is like asking how something exists. All we care about is the observation that things change with respect to a parameter we call time. You seem to simply be asserting that things change, but have not defined any parameters, which makes little physical sense.Can this be qualified with an explanation, as to how this change occurs "with respect to time"?
If we consider some property x that is a continuous function of some parameter 't', then the change of the property with respect to the parameter 't' is defined as the limit of x(t) + x(t+dt)/dt as the parameter interval 'dt' approaches 0.I won't argue on the basis of the maths, but with regard to the [presumably basic] Doppler example, of lightning striking two poles, regardless of what both observers may have seen, the question of whether the lightning struck both poles at the same moment, is answerable from the point of view of the bolts of lighning and/or the poles.
Also, both observers can only experience things in the present. They may observe events in what appear to be slightly different time frames, but the only "time frame" that either of them can operate in, is the present.
But I explicitly said that the doppler effect can be understood by considering galilean transformations, but that simultaneity could not. In otherwords, yes, the doppler effect can be understood under a framework where everyone's present is the same, even if things are not always detected at the same time for every observer. But simultaneity is an effect that cannot be understood unless we reject the notion of an absolute present shared by everyone. It is relativistic.The preferred reference frame is dependent on what is being measured, or asked. With regard to the Doppler lightning/pole example above, the preferred reference frame is easily detectable - it is either the bolts of lightning or the poles, with the poles being, the presumably easier detected, reference frame.
<snip>
If the question is, did the lightning hit both poles at the same moment [in the measuring system called time], then the preferred reference frame is both the lighning and the rods, with the rods being eaier to detect than the lightning (presumably).
<snip>
The preferred reference frame is inferred from the question, or what is being measured.
It isn't at all. The laws of physics do not change with respect to lorentz transformations. In fact (if my understanding of General Relativity is correct) they are invariant with respect to all smooth one-to-one transformations. This means there is absolutely no way of distinguishing a better reference frame from a poorer one regardless of the question being asked.That is circular reasoning
<snip>
Time can only be inferred from change with respect to time. Again, circular reasoning.
<snip>
It is circular reasoning to say that distance is measured, by recording change with respect to distance.
<snip>
Again, it is circular reasoning to say that time can be measured by recording change with respect to time.
<snip>
To suggest that only something which changes with respect to time, can be used as a measurement of time, is circular reasoning, unless it can be shown how the phenomenon changes with respect to time.
What I am saying is not circular reasoning. What I am saying is that we observe change with respect to some parameter. We assume that parameter is actually a dimension of a manifold called spacetime, and produce a physical theory of space and time. This theory is a very good theory, so we are confident in the assumption that spacetime is physical.
What you are saying is "Let's remove the assumption that time exists, and instead assume that a plethora of unobserved and unexplained, undescribable physical interactions exist to accommodate the success of quantum field theory and relativity". Both points of view involve assumptions. Ours just involves fewer assumptions.The issue is what exactly these conventions are actually quantifying. Lenght quantifies a physical object e.g. a length of rope, which means that the physical object has some inherent existence, not the spacial dimension.
Time is the measurement of change in physical objects, or more pointedly, the comparison of the change of one object, to the change in another object, which is taken as a standardised unit of measurement.
Both the physical objects may have some inherent existence, time does not.
These are massive assumptions.0 -
Advertisement
-
antiselfdual wrote: »Define "tends."
goes or moves in a particular direction e.g. from order to disorder, or disorder to increasing disorder0 -
For a system to tend towards anything time has to exist!
Why?Every single one of them. Any test of GR that works - which is all of them - tells us that time exists. It is a fundamental aspect of GR.
How is the existence of time tested in these experiments, or what is used to represent time?0 -
I dont think that people assume that time exists. We perceive our reality as a sequence of events which are occuring in an linear order - the name we have for this and its is time. Initially it was seen as an absolute but this has been overthrown by relativity and now we understand that time is not an absolute but relative.
This is one of the issues, namely that the concept of time arises from our subjective perception of the universe. It is our perception of change that lead to the creation of the concept of time, rather than time having any inherent existence.
That we perceive our reality as a sequence of events which occur in linear order, is part of the problem, because our concept of time is largely based on our [mind made] concepts of past and future, which themselves never exist in reality, but only in our minds.There were no tests for time in GR experiments. It was another variable in the equation.
which presumably was represented using a clock?You seem to be looking for an absolute clock but there is none. We measure the passage of time in S.I. unit of a second and that is linked to say an atomic clock.
The issue is that the atomic clock,or any other clock, does not measure something that has any inherent existence, in and of itself.
All clocks are simply standard units of comparison, against which other things are compared. What the measurement instrument in the atomic clock actually measures, is the microwave radiation of electrons, not something called time.
These microwave emissions are then taken as a standard unit of comparison, against which other things are compared. It is the use of these standard units of comparison that mean time is a manmade measruement system, as opposed to an inherently existing entity/force/energy/etc./etc.0 -
mangaroosh wrote: »goes or moves in a particular direction e.g. from order to disorder, or disorder to increasing disorder
Why can you not just think of time as then being the "direction" along which change happens?0 -
Asking how something changes with respect to time is like asking how something exists. All we care about is the observation that things change with respect to a parameter we call time. You seem to simply be asserting that things change, but have not defined any parameters, which makes little physical sense.
I may have been confusing the issue a little, so hopefully this can clarify it somewhat. The issue is with regard to the nature of the parameter.
Change may still occur "with respect to time", the question is whether time has any inherent existence, or is it a manmade system of measurement.
If we consider what change is, we can consider an object, and examine how it is said to change.
If we take the example of an orange, and see how it changes as it decays. First one would have a ripe orange, full bodied, orange in colour.
As the orange decays, it will shrink somewhat in size, the colour of its skin will darken and ruen brown, and it will appear more withered than full bodied.
Now, if we ask the question, has the orange changed? Then the answer will be based on a comparison of the current state of the orange, to how the orange was at the beginning of the experiment.
The question may then be asked, and this could be where the concept of time comes in, how long did it take for the orange to decay? The answer to this question will involve the comparison of the decay of the orange to some other naturally occuring phenomenon e.g. the microwave emissions of electrons (under certain conditions).
Here the orange can be said to change with respect to time, however it is the nature of time that is in question. In this case it is simply a system of measurement/comparison.If we consider some property x that is a continuous function of some parameter 't', then the change of the property with respect to the parameter 't' is defined as the limit of x(t) + x(t+dt)/dt as the parameter interval 'dt' approaches 0.
There is an assumption that x is a continuous function of 't'.
These are the assumptions that are being questioned, so again, that is circular reasoning.But I explicitly said that the doppler effect can be understood by considering galilean transformations, but that simultaneity could not. In otherwords, yes, the doppler effect can be understood under a framework where everyone's present is the same, even if things are not always detected at the same time for every observer. But simultaneity is an effect that cannot be understood unless we reject the notion of an absolute present shared by everyone. It is relativistic.
Apologies, I will have to do a bit of homework on some of the concpets mentioned above.
But a point that may perhaps be relevant, is that people's perception of events, is not necessarily the reality of them. So if people observe events differently, and any subsequent attempt to explain the difference in those observations, has no bearing on whether or not there is a universal present. It rather means that people observe/perceive reality/the present differently.It isn't at all. The laws of physics do not change with respect to lorentz transformations. In fact (if my understanding of General Relativity is correct) they are invariant with respect to all smooth one-to-one transformations. This means there is absolutely no way of distinguishing a better reference frame from a poorer one regardless of the question being asked.
I won't try to argue this any further, but will rather ask a few questions to try and get a better understanding.
What is the basis for stating that there are no preferred reference frames?
Just to ask using an example. If we imagine that a star, in another galaxy, burns itself out, and the question is asked, is that star still burning, does that mean that due to our distance from the star, that the star is still burning in our reference frame, but not in the stars reference frame?What I am saying is not circular reasoning. What I am saying is that we observe change with respect to some parameter.
And that that parameter is only detectable by things which change with respect to it - that is circular reasoning.We assume that parameter is actually a dimension of a manifold called spacetime, and produce a physical theory of space and time. This theory is a very good theory, so we are confident in the assumption that spacetime is physical.
The issue is that, with regard to time, the assumption is propped up by a self-contained system, so the assumption is never falsifiable.
If a clock is assumed to measure something called time, then its use in an experiment as a measure of time, will simply support an incorrect assumption.What you are saying is "Let's remove the assumption that time exists, and instead assume that a plethora of unobserved and unexplained, undescribable physical interactions exist to accommodate the success of quantum field theory and relativity".
No, that may be what you imagine that I am saying, what is actually being said is that time does not exist. Whatever repercussions that might have, have absolutely no bearing on the truth (or otherwise) of that statement.Both points of view involve assumptions. Ours just involves fewer assumptions.
There are no assumptions with regard to the statement that time does not exist.
The other point of view is largely based on a fundamentally flawed assumption.
It is a logical fallacy to suggest that theThese are massive assumptions.
again, there is no assumption, rather a logical conclusion0 -
You'll notice I've stopped responding, and I suspect it won't be long before the others stop too. The XKCD comic posted earlier in the thread is a pretty good summary of what's going on here.
This will be my last post on the subject, so let me just point out the absurdity of accepting length or distance as physical, but not time. Given the finite speed of light, it you are not actually measuring distance. To take an extreme example, when you look out at a start you are looking maybe 10 years into the past. Even looking at the sun, you are not seeing the sun, but rather the suns position 8 minutes prior. You are measuring not a spacelike interval, nor a timelike interval, but rather a lightlike interval which you then use to infer distance in much the same way as we infer time. To accept space but not time as physical is inconsistent, and frankly silly.
Now hang on while I dig out the email address for the president of physics for you...0 -
mangaroosh wrote: »I may have been confusing the issue a little, so hopefully this can clarify it somewhat. The issue is with regard to the nature of the parameter.
Change may still occur "with respect to time", the question is whether time has any inherent existence, or is it a manmade system of measurement.
And while your argument that the "second" is a man made system of measurement, your argument that time is manmade is not compelling.
If we consider what change is, we can consider an object, and examine how it is said to change.
If we take the example of an orange, and see how it changes as it decays. First one would have a ripe orange, full bodied, orange in colour.
As the orange decays, it will shrink somewhat in size, the colour of its skin will darken and ruen brown, and it will appear more withered than full bodied.
Now, if we ask the question, has the orange changed? Then the answer will be based on a comparison of the current state of the orange, to how the orange was at the beginning of the experiment.
The question may then be asked, and this could be where the concept of time comes in, how long did it take for the orange to decay? The answer to this question will involve the comparison of the decay of the orange to some other naturally occuring phenomenon e.g. the microwave emissions of electrons (under certain conditions).
Here the orange can be said to change with respect to time, however it is the nature of time that is in question. In this case it is simply a system of measurement/comparison.
Then you would have to make an argument as to where the time parameter emerges from. With Julian Barbour's work, for example, the time parameter emerges from the structure of spacelike surfaces, which means accepting the existence of past present and future. Would you accept such a construct? If not, then it is no good to simply claim things change with respect to time but time is artificial. As we have no reason to accept your claim that it is artificial.There is an assumption that x is a continuous function of 't'.
These are the assumptions that are being questioned, so again, that is circular reasoning.
It is not circular reasoning because what you quoted was not an argument for the existence of time. If I said, we assume t exists therefore t exists then that would be circular reasoning. I have not done this. Instead I have shown you how change with respect to time is classically defined.But a point that may perhaps be relevant, is that people's perception of events, is not necessarily the reality of them. So if people observe events differently, and any subsequent attempt to explain the difference in those observations, has no bearing on whether or not there is a universal present. It rather means that people observe/perceive reality/the present differently.
Yes, but the claim that there is a universal present is just as much an assumption as the claim that there is no universal present. Relativity, which assumes the latter, has helped us to not only understand phenomena, but also predict new phenomena. If relativity did not predict phenomena, or made incorrect predictions, then we would not have confidence in the assumption that time exists.I won't try to argue this any further, but will rather ask a few questions to try and get a better understanding.
What is the basis for stating that there are no preferred reference frames?
The basis is that the laws of physics are indistinguishable from reference frame to reference frame. It is therefore impossible to distinguish between a reference frame where phenomena are real, and one where they are false/the result of a bad reference frame. And if all reference frames are indistinguisable then that means the assumption that there really is a preferred reference frame is superfluous, with no evidence to back it up.Just to ask using an example. If we imagine that a star, in another galaxy, burns itself out, and the question is asked, is that star still burning, does that mean that due to our distance from the star, that the star is still burning in our reference frame, but not in the stars reference frame?
No. The reason we "see" the star still burning is (as you know) information can only travel at the speed of light. So that's a case of "We see the star still burning, but we don't know if it has presently burned out because that info has not reached us yet.". Simultaneity is much more fundamental. With simultaneity, you could be walking down the street and pass me on a bench, and in my reference frame the star will still be burning, but in your reference frame the star will have already burnt out. This would not be a case of limited info, it would be the actual scenario.And that that parameter is only detectable by things which change with respect to it - that is circular reasoning.
You split my paragraph in half. You'll miss the point if you do that.The issue is that, with regard to time, the assumption is propped up by a self-contained system, so the assumption is never falsifiable.
If a clock is assumed to measure something called time, then its use in an experiment as a measure of time, will simply support an incorrect assumption.
Relativity is easily falsifiable. If relativity was incorrect, for example, then the doppler shift exhibited by high speed particles would be completely different.No, that may be what you imagine that I am saying, what is actually being said is that time does not exist. Whatever repercussions that might have, have absolutely no bearing on the truth (or otherwise) of that statement.
There are no assumptions with regard to the statement that time does not exist.
"Time does not exist." is an assumption. From that assumption, we end up with a variety of messy postulates, far more dubious than the postulate that time exists.0 -
Professor_Fink wrote: »You'll notice I've stopped responding, and I suspect it won't be long before the others stop too. The XKCD comic posted earlier in the thread is a pretty good summary of what's going on here.
This will be my last post on the subject, so let me just point out the absurdity of accepting length or distance as physical, but not time.
Apologies, I'm not sure where I gave the impression that I accept that space is a physical thing. That is perhaps the subject for another discussion.Professor_Fink wrote: »Given the finite speed of light, it you are not actually measuring distance. To take an extreme example, when you look out at a start you are looking maybe 10 years into the past. Even looking at the sun, you are not seeing the sun, but rather the suns position 8 minutes prior.
This is an interesting point that is often mooted, but is surely entirely incorrect, as what one sees is not 10yrs into the past, rather the rays of light that left the star 10yrs previously that are reaching the earth (or our retinae) in the present. These rays of light have travelled for 10yrs traversing outer space, and when we see them, we see them in the present.
That may indeed be what the star looked like 10yrs previously, but what we are seeing are the rays of light that have travelled across the galaxy, for 10yrs to reach the earth.
The same goes for the sun, what we see are the rays of light that left the sun 8mins previous. This may indeed be what the sun looked like 8mins previously, but it is still the rays of light that have travelled 8mins to hit the earth.
So just to re-iterate, we are not magically seeing into the past.Professor_Fink wrote: »You are measuring not a spacelike interval, nor a timelike interval, but rather a lightlike interval which you then use to infer distance in much the same way as we infer time. To accept space but not time as physical is inconsistent, and frankly silly.
Again, apologies if you seemed to have picked up that impression.Professor_Fink wrote: »Now hang on while I dig out the email address for the president of physics for you...
That may perhaps be a more productive way to spend your "time"!0 -
If there is no such thing as distance then why does it take light from some sources longer to reach us than others?0
-
Advertisement
-
Then you would have to make an argument as to where the time parameter emerges from. With Julian Barbour's work, for example, the time parameter emerges from the structure of spacelike surfaces, which means accepting the existence of past present and future. Would you accept such a construct? If not, then it is no good to simply claim things change with respect to time but time is artificial. As we have no reason to accept your claim that it is artificial.
I haven't read Barbour's book yet (still waiting for the sister to send it to me).
The time parameter emerges simply from our capacity to remember, and from our capacity to imagine.
The present moment is all that ever exists. All of human existence takes place in the present, even if there is a different present for everyone, this still holds true i.e. all the events in your life take place in your present, and all the events in my life take place in my present, so the present (even if it is personal) is all that exists for anyone.
It is the present that is ever changing. Events will occur and pass, always in the present. It is the fact that we can remember events that have occured [and passed by] that leads to the concept of "the past".
The issue is that "the past" does not actually exist, it is simply a memory of what used to be the present, and therefore exists only as a thought or memory in a persons mind.
The concept of the future is based on our ability to imagine that change will continue to occur, so that what we experience as the present will change, and will be confined to the memory (non-existence).
We imagine that the present will change, never completely accurately, although we may be able to make predictions as to how it will manifest itself, at least in part (never in totality).
Of course, when it comes "time" to guage our predictions against reality, this will occur by comparing the present to what we predicted.
The act of making the prediction will reside only in the memory, while the predictions (if on paper perhaps) will always only exist in the present. The comparison of our predictions to the manifest events, will take place in the present.
It is because of our ability to remember the present (after it changes and ceases to exist) and our capacity to imagine the present (when it will change and come into existence), that we get the concept of a "time line" or the "river of time".
If one can picture time as a road, along which one walks, where the only part of the road that exists is the part under ones feet. A person may take a step forward on the road, and the part in front of them will come into existence, while the piece they just stepped off from will fall away into non-existence.It is not circular reasoning because what you quoted was not an argument for the existence of time. If I said, we assume t exists therefore t exists then that would be circular reasoning. I have not done this. Instead I have shown you how change with respect to time is classically defined.
The question was, to show how things change with resepect to time.Yes, but the claim that there is a universal present is just as much an assumption as the claim that there is no universal present. Relativity, which assumes the latter, has helped us to not only understand phenomena, but also predict new phenomena. If relativity did not predict phenomena, or made incorrect predictions, then we would not have confidence in the assumption that time exists.
If we leave the discussion on the universal present for now, we can say that all that exists for anyone is the present, even if it is a personal/relative present.
This would mean that there is no universal reality, rather an individual reality, but the same arguments will hold, on an individual basis.
As for the predictions of GR, the issue isn't their accuracy, or their usefulness, rather the basic assumption upon which they are based, and the possible self-contained system that seems to support the assumption through experiments.
More clearly, while the predictions of GR may indeed be well supported, if there is a self-contained system within the experiments, then the assumption will neve be falsified, due to this self-contained system.
This self-contained system is, that time exists, and that a clock measures time.
Examination of a clock shows that what is being measured is not something called time, rather a physical phenomenon. That is the measurement device measures the change in the physical phenomenon.
The contention is, that the physical phenomenon changes with regard to time, however, there doesn't appear to be a logical reason as to why this is true.
Indeed to simply state this, without showing how, or why it is true, is a non-sequitur.The basis is that the laws of physics are indistinguishable from reference frame to reference frame. It is therefore impossible to distinguish between a reference frame where phenomena are real, and one where they are false/the result of a bad reference frame. And if all reference frames are indistinguisable then that means the assumption that there really is a preferred reference frame is superfluous, with no evidence to back it up.
No. The reason we "see" the star still burning is (as you know) information can only travel at the speed of light. So that's a case of "We see the star still burning, but we don't know if it has presently burned out because that info has not reached us yet.".
The issue of information only being able to travel at the speed of light, should then surely apply to the question of the lightning hitting the rods. Where the man in the train is travelling away from the rods, it means that the information has a longer distance to travel. As one rod will be closer to him than the other, the information from that rod will reach him before the other rod, making it appear that the lightning hit one rod before the other, when the reality of the event, may indeed have been different.
The laws of physics won't change in either reference frame, so on that basis there would be no preferred reference frame, but depending on the question that is asked, one reference frame may be more suitable to answering the question than the other.
With regard to the example of the star burning itself out, then the reference frame of the star is more suitable for answering the question "has the star burned itself out".Simultaneity is much more fundamental. With simultaneity, you could be walking down the street and pass me on a bench, and in my reference frame the star will still be burning, but in your reference frame the star will have already burnt out. This would not be a case of limited info, it would be the actual scenario.
The issue however, would not be that the star was still burning (if we assume in this case that the star has burned itself out), rather that the information that the star sent out, before it burned out, is only reaching you now, while it would have already reached me on its way to you.
I would of course have to be walking towards the star, or rather the information from the star.You split my paragraph in half. You'll miss the point if you do that.
It was just to make the point that the contention thus far had been that objects/events change with respect to time, but that time is only measureable by those objects which change with respect to it.
With no explanation of how objects change with respect to time.Relativity is easily falsifiable. If relativity was incorrect, for example, then the doppler shift exhibited by high speed particles would be completely different.
If there is a self-contained system used in experiments, then certain things (not all) will not be falsifiable, namely those that depend on the self-contained system"Time does not exist." is an assumption. From that assumption, we end up with a variety of messy postulates, far more dubious than the postulate that time exists.
"Time does not exist" is not an assumption, rather a logical conclusion, based on the examination of the assumptions, upon which times existence is based.
What we end up with, if time does not exist, is a fallacious argument for the eixstence of time. It has no bearing on the truth of the statement, or the reality of the situation.0
Advertisement