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Thread: two kinds of expansion.

  1. #1

    two kinds of expansion.

    I know there is a good chance that I am confused about this but I really need someone to clear it up.

    Expansion or contraction of space could happen 2 different ways.

    1) Space is added so that there was 1 meter and now there is 3 meters 2 meters of space was created. All observers see the new realestate.

    2) Space is stretched, 1 meter gets stretched. Locally ( relative to something in the stretched space(-time) 1 meter is still equal to a meter but for an observer outside they would see 3 meters.

    In the second stretching I would argue that if space is stretched then time also needs to be stretched relative to the observer OR the speed of light will not stay constant at all points.

    In the first time and space are independant. In the second they are related.
    Can we agree?

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    Quote Originally Posted by tommac View Post
    I know there is a good chance that I am confused about this but I really need someone to clear it up.

    Expansion or contraction of space could happen 2 different ways.

    1) Space is added so that there was 1 meter and now there is 3 meters 2 meters of space was created. All observers see the new realestate.
    Ok.


    Quote Originally Posted by tommac View Post
    2) Space is stretched, 1 meter gets stretched. Locally ( relative to something in the stretched space(-time) 1 meter is still equal to a meter but for an observer outside they would see 3 meters.
    Incorrect.

    Quote Originally Posted by tommac View Post
    In the second stretching I would argue that if space is stretched then time also needs to be stretched relative to the observer OR the speed of light will not stay constant at all points.

    In the first time and space are independant. In the second they are related.
    Can we agree?
    Cannot agree.

    Explain, clearly, why you think that time must be stretched?

    Grant H. Answered this repeatedly- the best example he gave was that it took 13.7 billion years for light to travel 40 million light years.
    If Time stretched in the manner you describe, it would not have taken 13.7 billion years.

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    Tommac, will you please, please, please, please quit this business of starting new threads for each tiny new bit of puzzlement that crosses your mind. It's a recipe for confusion, because individuals will inevitably track through your many similar threads in different orders, and answer your questions in different ways, unaware of other answers that have already been given. Most of us now have absolutely no idea where to find any significant previous post that we've read somewhere in this chaotic network you've created.
    I, for one, am not going to dodge around after you. I'm prepared to conduct a single conversation on this thread, where we seem to be making some progress.
    Otherwise, I wish you luck in your endeavours.

    Grant Hutchison

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    Quote Originally Posted by Neverfly View Post
    Explain, clearly, why you think that time must be stretched?
    I think better terms for "stretched" when referring to time would be something like speeds up, accelerates, runs faster, or quickens. Semanticly speaking, you can stretch space but not time since "stretched" refers to an increase in distance. When space stretches, time must quicken if we are to use Einstein’s c as our constant. Meter sticks grow longer relative to the past as space expands while clocks simultaneously run faster. There appears to be some confusion about what you mean by "stretched" time. Would it be safe to say that stretched time means that clocks run faster?

    If Einstein’s c is a constant and c=s/t , then "stretching" the value of s requires that we also "stretch" the value of time. The words may be vague but I don’t understand why the concept is so hard to explain.

    Quote Originally Posted by grant hutchison View Post
    Tommac, will you please, please, please, please quit this business of starting new threads for each tiny new bit of puzzlement that crosses your mind.
    Good suggestion.

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    Quote Originally Posted by grant hutchison View Post
    Tommac, will you please, please, please, please quit this business of starting new threads for each tiny new bit of puzzlement that crosses your mind. It's a recipe for confusion, because individuals will inevitably track through your many similar threads in different orders, and answer your questions in different ways, unaware of other answers that have already been given. Most of us now have absolutely no idea where to find any significant previous post that we've read somewhere in this chaotic network you've created.
    I, for one, am not going to dodge around after you. I'm prepared to conduct a single conversation on this thread, where we seem to be making some progress.
    Otherwise, I wish you luck in your endeavors.

    Grant Hutchison
    Tommac please listen to Grant and just take a step back, we are all struggling to keep up. I enjoy most of the questions you pose because we have similar mis-understandings and are both keen for answers & solutions! But i have just spent the last 2 hrs reading through threads posted on Q&A and ATM and we seem to be going back and forth. Please m8!!

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    Quote Originally Posted by Bob Angstrom View Post
    The words may be vague but I don’t understand why the concept is so hard to explain.
    Because people (including myself) keep giving vague descriptions to something that may be impossible to describe with words. We inevitably end up confusing him, especially if someone writes something that can be misinterpreted or is just plain misleading.


    I think better terms for "stretched" when referring to time would be something like speeds up, accelerates, runs faster, or quickens.
    It would, but unfortunately we are talking about the expansion of the universe over time, where time does not speed up. At least I think the OP might be referring to the expansion of the universe. He might also have mixed in something about the Lorentz transformation from SR, I'm not sure. Whatever, time doesn't accelerate. Wherever or whenever you experience a second in this universe, whatever you are doing, a second is a second and is the same length as everybody else's seconds. Observers in different places simply experience different amounts of seconds depending on what they are doing.


    When space stretches, time must quicken if we are to use Einstein’s c as our constant.
    No, c is always measured as c in meters per second. Light emitted at a distance of around 40 million light years away travelled 13.7 billion light-years to reach us here. Meters are always the same length and so are seconds. New meters were being introduced between that light and this point in space as the light moved.


    Meter sticks grow longer relative to the past as space expands while clocks simultaneously run faster.
    No. Meter sticks and clocks stay the same whilst the distance in meters between co-moving coordinates increases.


    There appears to be some confusion about what you mean by "stretched" time. Would it be safe to say that stretched time means that clocks run faster?
    So there does. It would not be safe to say that, as time isn't thought to be stretching anywhere, due to cosmic expansion. Even on a purely conceptual level, if time were to "stretch", then a second would now be longer so time would be running slower, not faster. But it isn't.

    Now if we are talking pure SR, pure relative motion between two observers in different inertial frames, one might see the other as length contracted along the direction of motion, and see the others time running slower than their own. The other would see them as contracted and time-dilated in the same way, looking shorter along the direction of motion, and with their time running slower. In the end it they would work out (if they met up) that both ships were always as long as they had ever been and both had experienced time at the normal rate, but one had experienced less seconds than the other.

    In GR, you experience different amounts of seconds, relative to another observer, depending on the gravitational conditions around you. But all seconds are the same length.

    You might like to think of it like time is running faster or slower, but in science, seconds and meters stay the same throughout, you just get more or less of them!

  7. #7

    Lightbulb Does the speed of light change?

    Quote Originally Posted by tommac View Post
    2) Space is stretched, 1 meter gets stretched. Locally (relative to something in the stretched space(-time) 1 meter is still equal to a meter but for an observer outside they would see 3 meters.
    An obvious question arises: Exactly how does one go about the task of looking, in order to "see" 3 meters instead of 1 meter, from a distance? This goes to the heart of the question: How do you know that two different observers will measure two different distances?

    Quote Originally Posted by tommac View Post
    In the second stretching I would argue that if space is stretched then time also needs to be stretched relative to the observer OR the speed of light will not stay constant at all points.
    And I will refute that argument. It is a simple matter of basic physics, for all waves including light, that velocity = wavelength*frequency. So let space stretch. If the velocity in fact remains constant, then the necessary consequence of that would be that the product of wavelength and frequency would have to remain invariant. That means that the stretching of space could stretch the wavelength (which gets larger) while the frequency gets smaller accordingly. This is in fact exactly what is observed in cosmological redshifts. Therefore, observation implies that the speed of light in fact remains constant, throughout the entire range of observed redshifts, which implies (in the standard cosmology) all the history of the universe excepting perhaps the first ~800,000,000 years.

    Meanwhile, we know that according to special relativity, the speed of light should be constant for all inertial frames of reference. Since special relativity is strongly supported by observation (What is the experimental basis of Special Relativity?), then one must take seriously the requirement that the speed of light be constant. Time dilation specifically requires this constancy. Observation indicates that time dilation works as predicted on Earth (Muon Experiments in Relativity; Bailey, et al., 1979, Coan, Liu & Ye, 2005; Field, 2006). Observation also indicates that time dilation works in the same way, which implies the same speed of light in a local inertial frame, in high redshift environments of type Ia supernovae (Foley, et al., 2005; Blondin, et al., 2008), and apparently for gamma ray bursts (i.e., Chang, 2001). This is direct observational evidence that the speed of light has not changed over most of the history of the universe. This is consistent with the analysis of cosmological redshifts shown above.

    So not only in there no observational support for the claim that the speed of light does vary as the universe expands, there is positive observational support to the contrary.

  8. #8
    yes stretched time means clocks run faster


    Quote Originally Posted by Bob Angstrom View Post
    I think better terms for "stretched" when referring to time would be something like speeds up, accelerates, runs faster, or quickens. Semanticly speaking, you can stretch space but not time since "stretched" refers to an increase in distance. When space stretches, time must quicken if we are to use Einstein’s c as our constant. Meter sticks grow longer relative to the past as space expands while clocks simultaneously run faster. There appears to be some confusion about what you mean by "stretched" time. Would it be safe to say that stretched time means that clocks run faster?

    If Einstein’s c is a constant and c=s/t , then "stretching" the value of s requires that we also "stretch" the value of time. The words may be vague but I don’t understand why the concept is so hard to explain.



    Good suggestion.

  9. #9
    I disagree.

    Quote Originally Posted by speedfreek View Post
    Because people (including myself) keep giving vague descriptions to something that may be impossible to describe with words. We inevitably end up confusing him, especially if someone writes something that can be misinterpreted or is just plain misleading.




    It would, but unfortunately we are talking about the expansion of the universe over time, where time does not speed up. At least I think the OP might be referring to the expansion of the universe. He might also have mixed in something about the Lorentz transformation from SR, I'm not sure. Whatever, time doesn't accelerate. Wherever or whenever you experience a second in this universe, whatever you are doing, a second is a second and is the same length as everybody else's seconds. Observers in different places simply experience different amounts of seconds depending on what they are doing.




    No, c is always measured as c in meters per second. Light emitted at a distance of around 40 million light years away travelled 13.7 billion light-years to reach us here. Meters are always the same length and so are seconds. New meters were being introduced between that light and this point in space as the light moved.




    No. Meter sticks and clocks stay the same whilst the distance in meters between co-moving coordinates increases.




    So there does. It would not be safe to say that, as time isn't thought to be stretching anywhere, due to cosmic expansion. Even on a purely conceptual level, if time were to "stretch", then a second would now be longer so time would be running slower, not faster. But it isn't.

    Now if we are talking pure SR, pure relative motion between two observers in different inertial frames, one might see the other as length contracted along the direction of motion, and see the others time running slower than their own. The other would see them as contracted and time-dilated in the same way, looking shorter along the direction of motion, and with their time running slower. In the end it they would work out (if they met up) that both ships were always as long as they had ever been and both had experienced time at the normal rate, but one had experienced less seconds than the other.

    In GR, you experience different amounts of seconds, relative to another observer, depending on the gravitational conditions around you. But all seconds are the same length.

    You might like to think of it like time is running faster or slower, but in science, seconds and meters stay the same throughout, you just get more or less of them!

  10. #10
    Quote Originally Posted by Tim Thompson View Post
    An obvious question arises: Exactly how does one go about the task of looking, in order to "see" 3 meters instead of 1 meter, from a distance? This goes to the heart of the question: How do you know that two different observers will measure two different distances?
    You have a redshift without a change in distance.

  11. #11
    Quote Originally Posted by Tim Thompson View Post


    And I will refute that argument. It is a simple matter of basic physics, for all waves including light, that velocity = wavelength*frequency. So let space stretch. If the velocity in fact remains constant, then the necessary consequence of that would be that the product of wavelength and frequency would have to remain invariant. That means that the stretching of space could stretch the wavelength (which gets larger) while the frequency gets smaller accordingly. This is in fact exactly what is observed in cosmological redshifts. Therefore, observation implies that the speed of light in fact remains constant, throughout the entire range of observed redshifts, which implies (in the standard cosmology) all the history of the universe excepting perhaps the first ~800,000,000 years..
    This is proof of number 2 not number 1. If space expanded so that 1 meter stretched to 3 meters but time didnt stretch. then the speed of light would travel 1 meter in 1 unit and 3 meters in 1 units. So speed of light is not constant. your refute ... is what I have been trying to say ... maybe I am not saying it correctly. But your proof is correct for #2

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    Quote Originally Posted by speedfreek View Post
    Light emitted at a distance of around 40 million light years away travelled 13.7 billion light-years to reach us here. Meters are always the same length and so are seconds. New meters were being introduced between that light and this point in space as the light moved.
    If we ignore the possibility that introducing "new meters" to meters makes no sense, do you understand that one would need to introduce one "new second" for every 300,000,000 "new meters". Or as previously stated, stretching space requires that we stretch time if c is to remain constant.
    Quote Originally Posted by speedfreek View Post
    In GR, you experience different amounts of seconds, relative to another observer, depending on the gravitational conditions around you. But all seconds are the same length.
    I didn't know Einsteins clocks all ran at the same speed. They just add or subtract seconds. This is enlightening.
    Quote Originally Posted by speedfreek View Post
    You might like to think of it like time is running faster or slower, but in science, seconds and meters stay the same throughout, you just get more or less of them!
    This is an amazingly astute observation I'll have to write it down.

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    Quote Originally Posted by Bob Angstrom View Post
    If we ignore the possibility that introducing "new meters" to meters makes no sense, do you understand that one would need to introduce one "new second" for every 300,000,000 "new meters". Or as previously stated, stretching space requires that we stretch time if c is to remain constant.
    It is quite simple really. If the photons from the CMBR that we receive today were emitted when the surface of last scattering was only 40 million light years away, and both meters and seconds "expanded" with the expansion of the universe, then according to that thinking the universe is now only 40 million years old and 40 million light years in radius....

    Those photons took 13.7 billion years to reach us, so if light travels at around 300,000,000 meters per second, it must have travelled many more meters and taken many more seconds in order for it to take that long to reach us.

    So distances increased (thus more meters were added) and seconds kept ticking away at the same speed (thus more seconds passed). If a distance was once only 1 meter and is now 2 meters, you have more meters, not expanding meters.

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    Quote Originally Posted by tommac View Post
    So speed of light is not constant. your refute ... is what I have been trying to say ... maybe I am not saying it correctly. But your proof is correct for #2
    This is the way I read it too. Tim Thompson's excellent "refutation" of your statement concludes by supporting your position.

  15. #15
    Quote Originally Posted by Neverfly View Post
    Grant H. Answered this repeatedly- the best example he gave was that it took 13.7 billion years for light to travel 40 million light years.
    If Time stretched in the manner you describe, it would not have taken 13.7 billion years.
    huh? I need to read this again. What are you basing this on? what is the proof that light travelled 13.7 years to traverse 40 million light years of space? relative to who?

    I will read whatever you send me on this. Please show the post or sources of this claim. I may have skipped over this by accident.

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    Quote Originally Posted by Bob Angstrom View Post
    This is the way I read it too. Tim Thompson's excellent "refutation" of your statement concludes by supporting your position.
    Not quite.
    Tim Thompson clarified what Tommac had said. Tommac did get some things correct but others incorrect. So it appears to support Tommacs statements- but actually it stands on its own.
    Tommac got some parts right but not others.

    Now, Tommac is obviously intelligent and I've noticed he will put out some profound things- If he could just settle his pace down to an effective learning curve- he could accomplish quite a lot.

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    Quote Originally Posted by speedfreek View Post
    It is quite simple really. If the photons from the CMBR that we receive today were emitted when the surface of last scattering was only 40 million light years away, and both meters and seconds "expanded" with the expansion of the universe, then according to that thinking the universe is now only 40 million years old and 40 million light years in radius....
    No, according to "that thinking" it works the opposite way but that is another issue.
    Quote Originally Posted by speedfreek View Post
    Those photons took 13.7 billion years to reach us, so if light travels at around 300,000,000 meters per second, it must have travelled many more meters and taken many more seconds in order for it to take that long to reach us.

    So distances increased (thus more meters were added) and seconds kept ticking away at the same speed (thus more seconds passed). If a distance was once only 1 meter and is now 2 meters, you have more meters, not expanding meters.
    If I understand correctly, you are saying the universe does not expand by stretching like a balloon. It expands like a melon by adding more space-time "cells". Is that the general idea?

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    No, we are talking about the same thing in different ways, and managing to confuse people in the process by coming at it from different angles. This is the point I am making, due to your statement earlier in this thread, that:

    Meter sticks grow longer relative to the past as space expands
    The scientific method is usually that an observers rulers (meter sticks) always remain the same length, which is why they measure the universe to be getting larger as time goes on. Your frame of reference is defined by your meter stick. If meter sticks grew longer relative to the past, as you are saying, then we would say meters used to be shorter, but we definitely do not say that. We say the universe was smaller - there were less meters in it then, compared to now.

    The balloon stretches and expands, but points (or rulers) on that balloon do not stretch with it. Of course. So saying things like "meter sticks grow longer" is very misleading. I did it myself in another thread as it is easy to think of it in that way, but when you start actually looking at the numbers it leads to many problems.

  19. #19
    Neverfly, you complete me!

    Quote Originally Posted by Neverfly View Post
    Not quite.
    Tim Thompson clarified what Tommac had said. Tommac did get some things correct but others incorrect. So it appears to support Tommacs statements- but actually it stands on its own.
    Tommac got some parts right but not others.

    Now, Tommac is obviously intelligent and I've noticed he will put out some profound things- If he could just settle his pace down to an effective learning curve- he could accomplish quite a lot.

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    Now, Tommac is obviously intelligent and I've noticed he will put out some profound things- If he could just settle his pace down to an effective learning curve- he could accomplish quite a lot.
    I totally agree. I haven't seen such enthusiasm and so many insightful questions in a long time. That, to me, makes it obvious that, despite Tommacs earlier protestations, he really wants to understand it all.

  21. #21
    Quote Originally Posted by speedfreek View Post
    It is quite simple really. If the photons from the CMBR that we receive today were emitted when the surface of last scattering was only 40 million light years away, and both meters and seconds "expanded" with the expansion of the universe, then according to that thinking the universe is now only 40 million years old and 40 million light years in radius....
    No. In fact ... this is my basis of proof against the big bang. Space can expand forever and extrapolation backwards does not necessarily yield a singularity. this could hint at either an infinitely expanding universe OR a totally different starting point than the current big bang theory ( I think )

    and ... This is part of the root of me questioning the CMBR.

    I know that you disagree with me ... and these are two of the main reasons why we disagree.

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    But there is nothing in the Big-Bang theory that states the universe cannot expand forever, or that it started with a singularity. All it currently states is that the universe has been expanding for as far back in time as we can see, and will continue to do so for the foreseeable future, it does not make predictions for the origins of the universe. There are theories compatible with the Big-Bang theory that propose different forms of origin (M-theory, loop quantum gravity etc), none of which are currently testable, as far as I know.

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    Quote Originally Posted by speedfreek View Post
    The balloon stretches and expands, but points (or rulers) on that balloon do not stretch with it.
    Yes, you can look at it from the point of view where the balloon stretches while points (or rulers) on the balloon do not stretch with it but this is not a matter of inserting "new" meters because it involves changes in BOTH space and time. The stretching of space requires the stretching (or quickening) of time because our measurements of space, time, and c are all mutually defined. Meter sticks are cut to a standard defined as the distance that light travels in a vacuum in exactly 1/299,792,458th of a second so the "stretching" of space makes our rulers grow longer while the "quickening" of time makes them grow shorter and the two balance out. Rulers grow shorter because our faster ticking clocks shorten the distance that light can travel in 1/299,792,458th of a second.
    Clocks tick faster as the universe expands because expansion reduces the gravitational density of the universe and this is a general relativistic effect.

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    I'm a little puzzled with the 40 million in 13.7 billion figures.

    My understanding is as follows...

    - nothing physical can exceed the speed of light.
    - a short time after Origin, something we call Inflation grabbed the Universe & stretched it so that galaxies & current physical structure became possible. This occurred over s short space of time.
    - for something like 7 billion years, there was 'ballistic' expansion going on.
    - about 5 billion years back, something changed & the rate of expansion changed from slowing to speeding up.

    I don't understand how this process yields a possibility of a 34x expansion of the space between us and something 40 million light years off. Particularly as that 13.7 billion figure puts things back in the period where all mass was close enough that, apparently, spatial expansion could not have been a factor.

    I'm not antagonistic to the view, just it seems logically wrong that such a factor could be used.

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    Bob, we are talking about the same thing, you know. I know exactly what you mean and understand these implications of GR and SR for rulers and clocks. My problem is with the way that some of these issues are described.

    I know about the time-dilation between clocks in areas of different gravitational density as described by GR, of course, and I am not denying any such effects. Nor am I denying that one twin returns having aged less than the other in the twins paradox (using SR).

    If we send a clock to Jupiter, leave it there for a while and then bring it back again, we will find it is running behind clocks that stayed on Earth. Less seconds will have elapsed for the clock that went to Jupiter, when compared to a clock on Earth. This is fully accepted.

    The clocks on GPS satellites seem to us to run 7 microseconds per day slower than ours on Earth due to SR, and 45 microseconds a day faster due to GR, giving an overall difference of an extra 38 microseconds a day.

    But the key to relativity is to remember that where the clock is, time runs at the normal speed. A second to that GPS satellite (or you sitting on it) is actually the same length as a second here on Earth, but the difference in their relative rates is due to their relative movements through space-time, their "worldlines".

    There is no experiment that the twin on the moving ship can do that will confirm that his seconds are running any slower than they were on Earth. To the twin on the ship, a second is still the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. On the ship, atoms "vibrate" at the same speed as they always have, isotopes decay at the same rate as ever, and the twins beard grows at the same rate. Any science the twin does within the ship, within his frame of reference as defined by standard meters and seconds, will show him that everything is normal in his frame of reference. It is when he makes measurements of the universe around him that he finds the differences.

    The only way in which seconds run at different rates is relatively, but it is not strictly true to state simply that "time runs at a slower rate" on the ship. If both twins can observe each other using super-telescopes throughout the journey, and they subtract any "speed of light" issues from their calculations, this is what we find:

    On the outbound journey whilst the ship is cruising at a constant speed, the twin on Earth sees the twin in the ship looking as if his time is running slower. But the twin on the ship looking back at Earth sees clocks down here running slower by the same amount. Time-dilation is symmetrical between observers in inertial frames.

    On the return journey, they both see each other time-dilated in a symmetrical way too (although this time they both see other running "faster").

    Their clocks are actually running at the same rate at all times, but they are moving on different worldlines. Your worldline describes how your definition of "now" moves through space-time, and as two observers take different paths through space-time their definitions of "now" move out of synchronisation. This is known as a shift in simultaneity.

    Now when the observer on Earth sees the ship during the turnaround phase between constant movement away and constant movement back again, this is when the big difference in the twins ages occurs. At turnaround, the twin on Earth sees the moving twins clock suddenly slow right down when compared to its apparent rate during the outward leg of the journey. Conversely, the moving twin sees clock on Earth speed up immensely during this phase.

    The largest shift in simultaneity happens at the turnaround phase (although there are small shifts during the initial acceleration when leaving and the final deceleration when returning). The more their worldines diverge, the larger the shift in simultaneity between the two, during any non inertial movement.

    The same principles apply in GR - time is running at the same speed wherever you are, but your definition of "now" changes differently depending on the conditions you find yourself under.

    One of the basic principles of relativity is that the laws of physics are equivalent, they apply equally, wherever you perform your experiments. Meters and seconds are always the same length. Expanding rulers and slowing clocks are merely relative, but moreover, they are misleading. The universe expands around rulers and clocks, as science uses them as an invariant frame of reference. Meters don't expand, the universe expands causing spaces to contain more meters.
    Last edited by speedfreek; 2008-Apr-26 at 11:39 AM. Reason: clarification.

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    Quote Originally Posted by Acolyte View Post
    I'm a little puzzled with the 40 million in 13.7 billion figures.

    My understanding is as follows...

    - nothing physical can exceed the speed of light.
    - a short time after Origin, something we call Inflation grabbed the Universe & stretched it so that galaxies & current physical structure became possible. This occurred over s short space of time.
    - for something like 7 billion years, there was 'ballistic' expansion going on.
    - about 5 billion years back, something changed & the rate of expansion changed from slowing to speeding up.

    I don't understand how this process yields a possibility of a 34x expansion of the space between us and something 40 million light years off. Particularly as that 13.7 billion figure puts things back in the period where all mass was close enough that, apparently, spatial expansion could not have been a factor.

    I'm not antagonistic to the view, just it seems logically wrong that such a factor could be used.
    If I were to put it simply, I would say the limit of the speed of light only applies to objects moving through the universe, not the way the universe can stretch around them.

    I think this question would be better suited to a search through the Q&A forum.

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    Quote Originally Posted by Acolyte View Post
    I don't understand how this process yields a possibility of a 34x expansion of the space between us and something 40 million light years off. Particularly as that 13.7 billion figure puts things back in the period where all mass was close enough that, apparently, spatial expansion could not have been a factor.
    The regions of space which emitted the cosmic background radiation we see now were receding from us at 50 times the speed of light when these photons decoupled. Because of this, the photons have spent most of their travel time moving towards us at lightspeed through regions that are moving away from us at greater than lightspeed. Hence the slow progress.
    You'll find further detail in Lineweaver and Davis's SciAm article.

    Grant Hutchison

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    From Ned Wrights Cosmology FAQ

    Is the Universe expanding or is it just that our definitions of length and time are changing?

    The definitions of length and time are not changing in the standard model. The second is still 9192631770 cycles of a Cesium atomic clock and the meter is still the distance light travels in 9192631770/299792458 cycles of a Cesium atomic clock.

  29. #29
    Cool ... I thought there was some sort of singularity involved. All of the stuff that I have read included it ... however if there is no singularity and it does not state that there was a starting point / ending point then I am cool with it. I am now pro-BB

    Quote Originally Posted by speedfreek View Post
    But there is nothing in the Big-Bang theory that states the universe cannot expand forever, or that it started with a singularity. All it currently states is that the universe has been expanding for as far back in time as we can see, and will continue to do so for the foreseeable future, it does not make predictions for the origins of the universe. There are theories compatible with the Big-Bang theory that propose different forms of origin (M-theory, loop quantum gravity etc), none of which are currently testable, as far as I know.

  30. #30
    Quote Originally Posted by speedfreek View Post
    Meters don't expand, the universe expands causing spaces to contain more meters.
    You have such a great post then end it with this piece of utter nonsense

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