Time and the Light Box

by Luke Muehlhauser on November 3, 2010 in Science

One objection to the Kalam Cosmological Argument is that it requires an A Theory of time, but most physicists reject the A theory because of special relativity. Though the main idea of special relativity – that the laws of physics are the same for all observers (in uniform motion), so a microwave oven works just fine on a planet that is moving very fast relative to Earth – is simple, it has strange consequences for our concept of time. When we understand these consequences, we can see why special relativity undermines the A Theory of time.

Last time, I said that the time interval between two events must be different for two observers who are in motion relative to each other. Today I will show why this must be true, using an illustration borrowed from Richard Wolfson‘s excellent book, Simply Einstein.

Imagine you’re holding a long box with a laser at one end, and a mirror at the other end. Here’s how it works: A beam of light departs from the laser. Let’s call that Event A. The light travels “vertically” to the other end of the box, bounces off the mirror, and returns to the source. When the light returns to the source, that’s Event B.

This round trip takes some time, however small. Consider the time interval between events A and B relative to the reference frame of the light box. Let’s say that interval was 6 nanoseconds, since light travels about a foot in one nanosecond. Since you are standing at rest relative to the light box, you will observe that the interval between events A and B is 6 nanoseconds.

Now, imagine that you and the light box are floating past me in deep space, very fast. Equivalently, I am floating past you at that very same speed. Now, what interval will I observe between events A and B?

From my reference frame, the light has further to travel than it does in your reference frame, because from my reference frame, after the light departs from the laser, the box moves “horizontally” before the light beam hits the mirror. So the light beam moves vertically and horizontally to reach the mirror – a longer distance than it had to move from your reference frame. And the same is true for its return trip back to the laser:

(adapted from page 97 of Wolfson's book)

(The length of the box is L and the speed at which we are passing each other is v. The three boxes on the right illustrate that the box is in three different positions relative to me at Event A, when the light hits the mirror, and at Event B.)

Since light moves at a constant speed, but it has further to go from my reference frame than it does from your reference frame, that means that if for you the interval between events A and B is 6 nanoseconds, the interval is going to be longer than that for me.

And again, it’s not the the time interval between the two events is “really” 6 nanoseconds. There is no privileged reference frame. You are moving relative to me in just the same way that I am moving relative to you. So both time intervals are correct, with respect to each reference frame, which is the only kind of time interval there is.

Time intervals between events must always be given with respect to a chosen reference frame, because there is no “absolute” reference frame. That’s the whole point of special relativity.

Intuitively, this doesn’t make sense. How can there be two different time intervals between the exact same two events? We assume this is impossible. We assume the passage of time is absolute and consistent across the universe as a whole, so there is always one correct time interval between any two events. There is a kind of “universal clock” that ticks away forever, and after each tick the present moves one step into the past, and one moment of what was once part of the future is now the present, and the moment that had just been the present has moved into the past… across the universe as a whole.

But this is not so. Time, too, is relative. Time is different in each reference frame.

Floating clocks

One more illustration, also from Wolfson’s book. Let’s say we have three identical clocks. Two of them, C1 and C2, are floating in deep space, at rest relative to each other. A third clock, C3, is moving – relative to the reference frame of C1 and C2 – such that it passes C1 at Event A and it passes C2 at Event B.

(adapted from Wolfson's book page 103)

When C3 passes C1 (Event A occurs), it just so happens that all three clocks read the same time: noon. That is, an observer that is equally distant from C1 and C2 reads those two clocks as giving the same time, and an observer that is equally distant from C1 and C3 reads them as giving the same time.

By the time C3 passes C2 (Event B occurs), four hours have elapsed for clock C2, but only two hours have elapsed for clock C3.

What???

This is not because one of the clocks is broken, but because C3 has literally experienced less time relative to C1 and C2.

Note that Event A and Event B occurred at the same place relative to C3: namely, it happened very near the location of C3. But the interval between these two events was two hours, in C3′s reference frame.

In contrast, in a reference frame relative to C1 and C2, events A and B occurred at different times and different places. Event A occurred near C1, and event B occurred near C2. Moreover, the time interval between events A and B was four hours in the reference frame of C1 and C2.

“Moving Clocks Run Slowly”?

Why is this? Many physics textbooks say it’s because “moving clocks run slowly,” but that makes no sense. It wouldn’t be correct to say that clock C3 is moving and clocks C1 and C2 are floating still. Rather, C3 is moving relative to C1 and C2, and C1 and C2 are moving relative to C3. That’s the whole point of relativity. There is no privileged reference frame.

No, this “time dilation” occurs because

Given uniformly moving reference frames (no acceleration), the time between two events is shortest when measured in a reference frame where the two events occur at the same place.

So, the time interval between events A and B was shorter when it was measured from C3′s reference frame (where the two events occurred at the same place) than when it was measured from the reference frame of C1 and C2, from which the two events did not occur at the same place.

The exact same thing happened with the light box. There, the time interval between events A and B was shortest when it was measured from your reference frame, because from your reference frame events A and B occurred at the same place (since you were holding the light box). The time interval was longer when it was measured from my reference frame, because in my reference frame, events A and B occurred at slightly different places, since from my reference frame the light box was moving while the light was traveling from the laser (Event A) to the mirror and then back to the laser again (Event B).

Perhaps you’re beginning to see why special relativity is a problem for the A Theory of  time, and thus for the Kalam Cosmological Argument (KCA). But we have a few more things to discuss before we explain the tension between special relativity and the KCA.

Finally, for good measure, here’s a video making roughly the same point:

Or, more abstract:

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{ 50 comments… read them below or add one }

mojo.rhythm November 3, 2010 at 4:49 am

Luke,

What speed is Clock 3 moving at? Half the speed of light?

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Lorkas November 3, 2010 at 5:04 am

The time between two events is shortest when measured in a reference frame where the two events occur at the same place.

Is this the only variable that matters?

Suppose Luke and I meet up in Florida, and Luke gets into a spaceship to make a trip to Titan and back. Luke leaving is event 1. Then, in 30 (Earth) years, Luke arrives back on Earth and I meet him at the landing site, and his return is event 2. The two events happened at the same place in both of our frames of reference, but it’s not true that we experience the same time interval between the events, is it?

Another question:
If we’re in deep space, and Luke and I are in spaceships moving at equal velocities with no acceleration (measured via accelerometers on board), and I turn on my boosters so that my spaceship moves away relative to Luke’s, then I turn my spaceship around after a half-year or so (of my time) and fly back to Luke’s spaceship, and we reunite after a year of my time. Since both of us are there at both events, will we experience the same time interval between the two?

Perhaps the answer has to do with which person is experiencing more acceleration. It is possible to demonstrate that my spaceship accelerated and Luke’s did not, since acceleration requires the application of a force (which is why I would feel like I was being pulled toward the back of my ship when I turn on my rockets, but Luke would not experience that force at all even though he is “accelerating” relative to my frame of reference). That’s the only place I can think of that could introduce the asymmetry in this problem.

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Robert Oerter November 3, 2010 at 6:07 am

Lorkas,

Yes, acceleration is exactly the problem. Luke is addressing only special relativity (so far, at least), which deals with uniformly moving reference frames. An accelerated reference frame is different, and can be dealt with using general relativity. (Though the acceleration itself can be dealt with within special relativity: you just can’t assume the laws of physics are the same in both reference frames.)

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Luke Barnes November 3, 2010 at 6:26 am

“The time between two events is shortest when measured in a reference frame where the two events occur at the same place.”

This time interval is referred to as “proper time”, and there is a sense in which it “really is” the time between any two (timelike-separated) events. The problem is that things won’t stand still – given any two events, you can define a reference frame in which they occur at the same place. But introduce a third object, and it probably won’t sit still in your frame. It will move, and establish its own rest frame.

All of this is a tad academic – even WLC admits that SR is a problem for Kalam, but that SR is not valid for our universe. He relies on cosmic time to provide a”now” for the universe. I’m sure we’ll be hearing more about that in posts to come.

P.S. please read this before commenting on SR and acceleration:

http://www.desy.de/user/projects/Physics/Relativity/SR/acceleration.html

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Márcio November 3, 2010 at 6:38 am

Time is relative!!! Let’s use that on Nascar races or F1 races. Could be a lot of fun. Each team says that a pilot finished the race on a diferent time.
ahiahiahihaahi

Didn’t understand anything. Sorry…

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Luke Muehlhauser November 3, 2010 at 7:20 am

Thanks for the link, Luke Barnes. I’m having a hard time right now figuring out how much of general relativity, or acceleration, I really want to cover in this series. Right now I’m thinking of just covering what I need to in order to give the Penrose illustration of why SR seems to contradict simultaneity, and then make a beeline for Craig’s proposed solution, again covering only what I need to.

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mojo.rhythm November 3, 2010 at 7:30 am

BTW folks, here is a nice 10 min YouTube clip by a physics teacher explaining SR basics and time dilation w/a whiteboard. I found it very helpful.

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Luke Muehlhauser November 3, 2010 at 7:47 am

mojo.rhythm,

There are lots of confusing sentences in that video. I found it difficult.

For example, he began with “moving clocks run slowly”, which makes little sense unless you specify a reference frame.

He then said the height of the clock is the distance that light travels in one second, and later labeled this distance with ‘c’, which is used for the speed of light. Not only do these two things differ greatly in their value, but also in their unit of measurement!

and so on…

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Luke Muehlhauser November 3, 2010 at 7:50 am

Lorkas,

Thanks for your question! I added the necessary clarification: uniformly moving reference frames.

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Charles November 3, 2010 at 8:11 am

If your goal is to demonstrate the relativity of simultaneity, then why not do so directly? Time dilation is a distraction. We don’t need to understand it.

If you need a good example, see Knight. He does it all with pictures in two and a half pages.

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Charles November 3, 2010 at 8:16 am

This video looks about right.

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Charles November 3, 2010 at 8:26 am

Sorry. Link was broken. Try this.

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Luke Muehlhauser November 3, 2010 at 8:27 am

Charles,

The Knight link is broken, and so is the ‘video’ link. Where are you wanting to point?

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Charles November 3, 2010 at 8:35 am

Meh. Knight.

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Luke Muehlhauser November 3, 2010 at 9:55 am

Charles,

Do you have the page number, or a keyword I can search for?

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Daniel Weston November 3, 2010 at 10:04 am

There are lots of confusing sentences in that video. I found it difficult.For example, he began with “moving clocks run slowly”, which makes little sense unless you specify a reference frame.He then said the height of the clock is the distance that light travels in one second, and later labeled this distance with ‘c’, which is used for the speed of light. Not only do these two things differ greatly in their value, but also in their unit of measurement!and so on…

I think these criticisms are rather fastidious.
Firstly, is it not clear that the statement “moving clocks run slowly” should be interpreted as “clocks run slowly in reference frames in which they are moving”? Secondly, as for labelling the distance that light travels in one second by c, it is of course the case that the numerical value used to represent this distance is equal to the numerical value used to represent the speed c, provided that we stick to one set of units of length and time. If one supresses all units and uses dimensionless quantities, it would thus be correct to label the distance in question by c.
Finally, you write “and so on…”, but it is not obvious to me how the sequence of criticisms should be continued.

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Bill Maher November 3, 2010 at 10:39 am

on a sidenote, here is a fun video on the topic.

http://www.youtube.com/watch?v=BB1B42HYvZg

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cl November 3, 2010 at 12:31 pm

Luke,

Perhaps you’re beginning to see why special relativity is a problem for the A Theory of time, and thus for the Kalam Cosmological Argument (KCA).

Actually, I’m not, but you’ve piqued my interest for further posts.

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Charles November 3, 2010 at 2:43 pm

Luke,

I couldn’t find a preview of Knight online or I would linked. His discussion of simultaneity begins on page 1164 of the 1st edition. If you want to borrow, I can lend you my copy, or if you can wait a few weeks, I can send you my lecture notes. E-mail me privately.

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Shane McKee November 3, 2010 at 3:43 pm

Hi Luke,
Actually, I am led to believe that it *is* possible to formulate special relativity within an A-theory of time in a cellular-automata system; the only proviso is that *within* the system, you can’t tell the difference between motion in *space* and motion in *time*, so no reference frames are privileged from within. However, from the outside, you *can* specify a privileged “god’s time” reference frame, to which the universe will obligingly submit as a whole. I don’t know if this works for General Relativity.
Of course, that is not in any way to undermine your point that WLC does not know his physics, nor can it give any succour to the twitching corpse of the Kalam.

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Lorkas November 3, 2010 at 3:52 pm

He then said the height of the clock is the distance that light travels in one second, and later labeled this distance with ‘c’, which is used for the speed of light.

I caught that too. He should have listed the distance as 1 light second.

Still, I liked the video, and I understand why he used c to represent 1 light second, since it makes the math a bit cleaner.

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Luke Muehlhauser November 3, 2010 at 3:55 pm

Charles,

I have access to a later edition. What is the section heading? I’ll try to find it in the new edition.

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Luke Muehlhauser November 3, 2010 at 3:56 pm

Shane McKee,

My point is not at all that Craig doesn’t know his physics. He knows physics way better than I do. He knows quite well that the standard interpretation of special relativity rules out absolute simultaneity, which would defeat the KCA. He just rejects the standard interpretation of special relativity, and has written at length about why he does so.

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Tarun November 3, 2010 at 4:17 pm

It is a common misconception that acceleration is the key to the twin paradox, so it cannot be fully explained without moving to general relativity.

First, special relativity can deal with accelerated observers. It wouldn’t be much of a theory if it didn’t. As Robert Oerter observes, we can’t assume the laws will have the same form in an accelerated frame of reference, but you need not go to an accelerated frame of reference to handle accelerated observers. In the case of the astronaut taking off from Earth and returning later, special relativity itself delivers the verdict that the astronaut would have aged less than her twin on Earth. She traverses a greater space-time interval than an Earth-bound observer, so the proper time along her trajectory will be shorter. There is no need to move to an accelerating frame of reference or consider general relativity in order to get this result.

Second, the acceleration of the astronaut is not required either. Suppose space-time is cylindrical, so that someone who sets off from Earth in a particular spatial direction with a constant velocity will eventually wrap around and return to Earth without any acceleration. This allows the Earth-bound twin to compare his age with the astronaut without either of them accelerating. Special relativity still tells us that the astronaut will have aged less than her twin. The fact that the space-time is cylindrical does not take us outside the domain of special relativity because a cylindrical space-time is still flat (i.e. it can be described by the Minkowski metric).

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Shane McKee November 3, 2010 at 4:17 pm

Hi Luke, OK, maybe you’re not making that point, but you can take it from me that WLC does not know his physics. But leaving that aside, the point remains that although *within* the universe there is no privileged reference frame, from the *outside* there still can be, and there can even be universal time with a proper t=0, so the KCA (I feel) can actually survive this attack.

That’s not to say that I think the KCA is sound – it isn’t. If we view the universe as a structure of information, which is an increasingly popular view, then it is fully groundable in mathematics, and effector gods are not required for *anything*.

At best, WLC can only say that the universe is a system that required a “state” at t=0, but we know that mathematical structures such as the Fibonacci Sequence do not require a state at t=-1. Again, this gets back to the Tegmark notion of the mathematical universe; I’m partial to that explanation, and I think it kills Kalam stone dead.

Cheers,
-Shane

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Tarun November 3, 2010 at 4:21 pm

To summarize my previous comment: the central issue in the cases raised by Lorkas is not the acceleration of one of the two observers, but the fact that the space-time intervals traversed by these observers is different, even though they start and end at the same space-time point. Special relativity tells us that the path corresponding to the shortest space-time distance between two points experiences the longest time.

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Tarun November 3, 2010 at 4:30 pm

Luke,

I think the easiest way to establish the relativity of simultaneity is to think about a box with a light-bulb in the middle. In the frame of the box, when the bulb is switched on, the light reaches both ends of the box at the same time. However, in a frame moving relative to the box the light will hit one end first and then the other end (since the speed of light is constant and one end of the box is moving away from the light while the other end moves towards it). Bam, you have two events that are simultaneous in one frame but not in another. No need to detour through time dilation.

Still, I like the way you’re explaining these things, and it can’t hurt to give people a more thorough idea of the counter-intuitive consequences of special relativity. In my opinion, relativity is absolutely devastating to the A theory, and it is somewhat of a scandal that so many philosophers still adhere to it. I understand that Craig has some sort of neo-Lorentzian interpretation, but I really don’t see how such an interpretation could be made to generalize to gravitational phenomena. Does Craig just reject general relativity? I’m following your series with interest to find out.

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mojo.rhythm November 3, 2010 at 5:09 pm

Luke,

Really? Huh. I remember watching his video a month ago, and it really helped clarify it for me.

Lemme try again. Here is a really good illustrated guide to relativity by Sander Bais; a professor of theoretical physics at the University of Amsterdam. This was the first thing I ever read on special relativity, and it uses very little equations, mostly making use of space-time diagrams and so on. Very useful stuff!

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mojo.rhythm November 3, 2010 at 5:35 pm

Cl,

Actually, I’m not, but you’ve piqued my interest for further posts.

Here you go Cl, I’m sure you will find this very useful. It’s a fairly long article but it explains very clearly why the standard interpretation of Special Relativity implies a block theory of space-time, which as you probably know is very damaging to the Kalam.

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Lorkas November 3, 2010 at 6:43 pm

“the space-time intervals traversed by these observers is different”

Could you explain this to me more clearly? I’m not sure what you mean by “space-time intervals”, so I can’t see how you can make this statement without assuming a privileged frame of reference.

I’d like to know more but my field is biology, not physics, so alot of what is said is a little inaccessible to me without more preliminary study.

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Charles November 3, 2010 at 7:02 pm

I have access to a later edition. What is the section heading? I’ll try to find it in the new edition.  

In the 1st edition, the relevant material is in Chapter 36 (“Relativity”). You want section 36.5 (“The Relativity of Simultaneity”). Knight uses firecrackers, but I think its equivalent to what’s described in the video. In my edition, the section is between 36.4 (“Events and Measurements”) and 36.6 (“Time Dilation”). In the 2nd edition, he seems to have added a new chapter. Look in Chapter 37 (still, “Relativity”).

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Tarun November 3, 2010 at 7:53 pm

Lorkas,

Special relativity tells us that both spatial and temporal intervals are relative to reference frames. The distance between two events and the time between them cannot be defined in a frame-independent manner. But there is a kind of interval, a space-time interval, that does remain constant. This is kind of a mixture of spatial and temporal intervals.

If the two events are A and B, then the space-time interval between them is just the time between them measured by an observer in whose reference frame the events occur at the same place. While different frames will disagree about the temporal intervals they measure between the events, they will NOT disagree about the temporal interval measured by an observer in this frame. This is an absolute interval of considerable importance in special relativity.

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Luke Muehlhauser November 3, 2010 at 8:01 pm

Charles,

Found it; firecrackers and a railroad car. Thanks!

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bossmanham November 3, 2010 at 9:06 pm

This is all true for events that are relative to, say, us as observers of different frames of reference here in the universe, but you’re simply assuming there is no privileged frame of reference, and then make the metaphysical conclusion that, therefore, time is truly relative (which then leads to your grand metaphysical leap into the equal ontological reality of all moments in time, which is really weird).

I’ll grant that physical clock times are relative, but this does nothing to prove that time itself is segmented or is a block and is a physically distinguishable dimension. But, I’d like to know what evidence supposedly proves that. All of these experiments show that clock times are relative to different reference frames, but it does nothing to show that there isn’t a privileged frame.

It seems intuitively obvious to me that, as I am writing this, there are events happening on one of the moons of Jupiter simultaneous to my tapping on the keys on the computer. To tell me that light rays may reach these events at different times and then reach me later than you, or vice versa, is completely irrelevant. We’re not talking about light signals or the time it takes for them to travel, we are talking about what happens at a moment of time.

It seems to me that this continued endeavor to “disprove” the A theory of time using SR is to either be ignorant of the true discussion, or to be ignoring the counter arguments being offered. My contention is that there is a universal time by which distant events actually are simultaneous with each other and which does pass moment by moment. I’ve already cited several empirical evidences of that on previous posts, and there are good philosophical reasons to reject a B-theory and to accept an A-theory. It just isn’t the case that special relativity disproves the A-theory.

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bossmanham November 3, 2010 at 9:08 pm

Tarun,

Special relativity tells us that both spatial and temporal intervals are relative to reference frames

Special relativity doesn’t really show this, but rather it assumes it.

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bossmanham November 3, 2010 at 9:15 pm

Shane McKey,

Of course, that is not in any way to undermine your point that WLC does not know his physics

Of course, you must be ignorant of Craig’s several works on relativity theory, found:

here and here and here, among others.

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Tarun November 3, 2010 at 9:29 pm

bossmanham,

Special relativity only assumes two things: (1) The laws of physics take the same form in all inertial reference frames, and (2) The speed of light is fundamental constant. Based on these assumptions, it tells us that spatial and temporal intervals are relative to reference frames.

Also, it is true that you can consistently maintain that there is a privileged rest frame while still acknowledging the empirical adequacy of special relativity. This rest frame will be epistemically inaccessible, so postulating it seems otiose, but I will grant that it is an available move. But this seems to get far more complicated when we move to the general theory of relativity, where spacetime itself plays a dynamical role (not just space but *spacetime*). If you don’t grant the existence of any times except the present (or the present and the past) it is completely unclear to me how you could possible account for this dynamical role. It seems you would require a quite radical revision of our best theory of gravitation. Again, you could postulate a preferred foliation of spacetime (although again this seems otiose), but I don’t see how you can claim that only one slice of this foliation actually exists.

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bossmanham November 3, 2010 at 9:52 pm

And #1 assumes what we just said, does it not, since that would not be the case it there were a privileged frame, as I understand it.

I agree, special relativity certainly is empirically viable even under the form of relativity I adhere to. While I don’t think it’s the case that it’s epistemically inaccessible any longer, with the advent of general relativity that introduces the hypersurface of isotropy and cosmic time, I would add that even if we didn’t have that, we’d have the issue of Einstein’s SR not really being completely empirically adequate. The length contraction and clock retardation that is observed is left unexplained, and is simply derived from the equations. On forms that retain a privileged frame, these are explained (see Prokhovnik’s Light in Einstein’s Universe as I am completely unqualified to explain the fine details).

My main complaints are not the empirical data, as the model of relativity theory I think is correct is empirically equivalent to Einstein’s, but the philosophical assumptions that underly the status quo interpretation.

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Bram November 4, 2010 at 1:48 am

Interesting to mention is that this effect has been experimentally shown to be true by loading a bunch of atomic clocks in airplanes and flying them around the world.

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Charles November 4, 2010 at 1:21 pm

Not to mention each and every time you use GPS.

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Eugene November 4, 2010 at 1:37 pm

Why do you state in this post that “most physicists reject the A theory,” presumably in favor of a B-theory block universe, when, just last month, you linked to an article by Hrvoje Nikolic that stated, “most physicists, even many relativists, do not find [the B-theory of] time acceptable?” Is this equivocation merely to score a point?

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Luke Muehlhauser November 4, 2010 at 1:48 pm

Eugene,

Not sure what you mean… to my knowledge most physicists do reject the A theory. What’s your question?

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Eugene November 4, 2010 at 2:21 pm

Luke,

On September 27, 2010 you published an article on this blog entitled “Time and the Kalam Cosmological Argument”. In that article you linked to an article by the physicist Hrvoje Nikolic entitled “Block time: Why many physicists still don’t accept it?” In that article Nikolic wrote, “So, from the point of view of current knowledge in physics, it seems reasonable that every physicist should adopt this block-time picture of the universe. Nevertheless, most physicists, even many relativists, do not find such a picture of time acceptable.” (emphasis added) In other words, Nikolic explictly states that most physicists reject a B-theory of time.

Given that you linked to Nikolic’s article, given further that you are even hosting it on your site, it seems reasonable to assume that you’ve read it, including that excerpt.

Yet, despite all this, in this blog article you make the exact opposite statement declaring that “most physicists” reject the A-theory.

Given your almost direct contradition of Nikolic, a professional academic theortical physicist, I have to wonder at the cause: Did you merely forget what Nikolic said about the current consensus view among physicists? Or do you disagree with his anaylsis on the basis of some greater personal familiarity with the field? Or have you consciously chosen to ignore him so as to cast the KCA in an exaggeratedly bad light for strategic purposes?

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Luke Muehlhauser November 4, 2010 at 5:33 pm

Eugene,

I appreciate your detail, but I’m just confused. Saying that most physicists reject the A theory is not the ‘exact opposite statement’ as saying that most physicists reject the B theory. Both of those statements are compatible, and in fact if forced to guess, I would guess (very tentatively) that both are true.

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Eugene November 4, 2010 at 7:34 pm

Luke,

As I understand it, views of time divide into two major classifications: the belief that temporal becoming is a real phenomenon of objective reality (A-theory) and the belief that temporal becoming is merely an illusion of subjective perspective and that all moments of time exist with an equal degree of ontological reality in some sort of tenseless state (B-theory, or, as it’s sometimes called, the “block universe”).

On such a view, to reject the block universe, the B-theory, is neccesarily to commit oneself to the ontic reality of temporal becoming and thus to some form of A-theory. So if, as Nikolic says, most physicists reject the B-theory, then it would seem that most physicists are at least implicitly A-theorists, contrary to what you’ve written in this post.

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Luke Muehlhauser November 4, 2010 at 8:17 pm

Eugene,

Oh, I see where you’re coming from. Yeah, I don’t think that to reject A-theory is to commit oneself to B-theory or vice versa. I suspect most physicists just do physics according to the equations, and don’t take a ‘professional stance’ on A theory or B theory or another alternative. Still, my own reading of physicists is indeed different than Nikolic’s: if physicists were forced to guess at either A theory or B theory with no other options, I think most physicists would point at B theory. But someone should really do a survey! Maybe European physicists are more A-theoretic and American physicists are more B-theoretic? Hell, I don’t know.

Also, you might wonder how there could be other options besides A or B theory, but it depends how you break it down. Sometimes the two are mutually exclusive, sometimes not.

Cheers,

Luke

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Muto November 4, 2010 at 8:21 pm

Eugene,
All physicists I know reject the notion of simultanuity, hence they are not A-theorists, but I think it is fair to say that they are not B-theorists either.

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chroma November 4, 2010 at 11:44 pm

bossman:

What do you and/or Craig mean by ‘preferred’ frame? Do one or both of you mean the frame is just cooler than other frames? {I have read some tens of pages from Craig on the subject, but got carried away in other things when disappointed he wasn’t supplying anything.} Because, regardless of whether there’s a unique way under the FLRW metric to foliate spacetime into leaves exemplifying homogeneity and isotropy (i.e. nice looking), there will always be other ways to section off spacetime into hypersurfaces of simultaneity according to different observers.

Declaring that a geometrically simple way is logically superior to other ways, and hence absolute simultaneity exists, is akin to declaring that since there’s a unique torsion-free affine connection preserving Riemannian metric on a manifold, that whether two vectors from two distinct tangent spaces of a manifold are parellel is a query with an absolute answer reflecting an intrinsic relationship! Naturally, false. Does Craig really understand this stuff? He has given perhaps solid evidence to the contrary. (Imagine a philosopher back in the day proposing that speed is absolute, because there exists a frame in which it is absolute. This is literally Craig’s argument today, applied to a different conclusion.) In the meantime, I will continue scouring his writing when I feel up to it, including at least of one the links you gave, to find reason to believe otherwise, and hopefully finding him providing a valid and competent argument.

I admire your courage to go against the grain and to question the prevailing dogmas, but I can’t admire your haste to suggest epistemological superiority while grounding oneself in incompetent misunderstanding of the physics. It seems, ostensibly to me, you are clinging to your intuitions in the face of contradictory information, and therefore swimming upstream so to speak. Mathematically (and thus ontologically and metaphysically if they are in fact instantiated), manifolds have an absolute, intrinsic differential structure, independent of our coordinate systems designed to represent them. It just so happens that many of our conceits about space and time, such as the simultaneity of events, are no more intrinsic to these exotic objects than whether one thing is ‘behind’ another (which is, come to think of it, a natural spacelike analogue of simultaneity).

For an example of your naivete and bias exhibited here, you say that special relativity cannot explain length contraction or time dilation. What have you been smoking? There’s a geometric explanation with the aid of pictures on so niche and inaccessible a place as *Wikipedia*, after all! Plus, you said that special relativity simply ‘assumes’ that time and space intervals are relative to reference frame – epistemic libel born from ignorance. Moreover, you think that a preferred frame – whatever that is – would make simultaneity absolute, but fail to recall that absolute is short for not dependent on frame of reference, and thus are oblivious to simple fact that the question of good-looking frames is moot for the relativity or absoluteness of simultaneity. On top of this, you ask where the ‘proof’ is of the idea the universe is a spacetime block, while failing to recognize the fundamental purpose of the entire idea is its immense explanatory power. How does this neo-Lorentzian ‘interpretation’ explain all the things (basically everything to do the Lorentz factor) which special relativity does with with ease? Where is the proof or evidence of an (a)ether? Given this level of misconception coupled with your level of (still apparently tentative) confidence, I suspect you might be operating or partially operating on an agenda with regards to this issue.

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chroma November 5, 2010 at 12:10 am

It would make more sense if I had said not *variant* with frame of reference, instead. Simultaneity is determined, by definition, by frame of reference, but does not necessarily vary from frame to frame.

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Kyle Key November 6, 2010 at 1:45 pm

chroma: “I suspect you might be operating or partially operating on an agenda with regards to this issue.”

Nah, it’s probably just coincidence that a Christian would hold an extreme minority physics view propagated only because of its applicability to Christian preconceptions.

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