# If a absolute point would exist, still relativity theory would be valid

1. Nov 29, 2011

### digi99

Consider an absolute point somewhere in one of the universes and consider our light signal with constant speed C which expresses time and distance (same in fact).

If you don't know this point, the relativity theory would be exactly the same.

If you know this point, you could say, distances are absolute but time is not. Time would be still a relative something, because you can meassure time only from an event, and an absolute point was/is always there.

So even with absolute points, you should have time dilations in all directions, because light expresses a relative time to a chosen event.

Even if a speed V could be greater than C, time would be going faster (a minus time dilation, like a negative distance), what does it mean, maybe nothing special ... no back to the past/future etc. because a negative time dilation is something like a negative distance ..

2. Nov 29, 2011

### ghwellsjr

How can you say that time and distance are the same in fact and then say that distances are absolute but time is not? Both time and space are relative. Whether or not you know or understand relativity, distances are not absolute, just like time is not absolute.

You need to learn about events and Frames of Reference and the Lorentz Transform. That's what Special Relativity is all about. When you do, you will see that an event has coordinates that are defined according to a specified Frame of Reference. When you transform that event into another Frame of Reference moving with respect to the first one, that event will have a new set of coordinates which merely means that it is called something different according to the different specification of the second Frame of Reference. Until and unless you specify a Frame of Reference, you cannot meaningfully talk about a point in the universe, absolute or otherwise.

3. Nov 29, 2011

### pervect

Staff Emeritus
Other than the "ick" factor in having an absolute point that can have no experimental basis whatsoever, it is not necessarily logically inconsistent with relativity theory to postulate an undetectable absolute point.

That said, it seems very common to go off the rails when trying to pursue this line of thought. While this line of thought might not be necessarily logically consistent, it seems to encourage misunderstandings from what I"ve seen.

4. Nov 29, 2011

### Staff: Mentor

What exactly do you mean by an "absolute point"?

If we found an absolute point, how would we know it?

5. Nov 29, 2011

### pervect

Staff Emeritus
If it's undetectable by any experiment, you'd never be able to tell if you actually had one. But you could envision it as having as much metaphysical or philosophical significance as you'd like.

6. Nov 29, 2011

### Staff: Mentor

I'm thinking this "absolute point" is defined the usual way, even though the OP didn't say it: the point against which absolute motion can be measured.

7. Nov 30, 2011

### mathman

There may be some point to this discussion. From my understanding there is an inertial frame in which the CMB is the same temperature in all directions. In some sense this a preferred frame (without a center). However it doesn't negate relativity.

8. Nov 30, 2011

### digi99

I answer all in one answer, because it is still a thought.

Firstly it was a quick thought, I am fully busy with Lorenz and frames, but if you think something, you can make errors of course. But in discussions you learn from each other.

So Ghwellsjr, I am coming back on my old topic after a while (and other topics) ..

I understand that relativity has all to do to view all from frames etc. but without the light speed C there was nothing special (under condition I know only the SRT and not the RT with accelerations). Thanks to C we know time dilations (different times in frames), that we find special.

I said even there was something absolute, for all moving objects the SRT would still be valid and time dilation would still exist. And even you should have absolute distances, thanks to the "relative time measuring" signal light there would still be time dilation, and the moving one (compared to the absolute points) should still have a time dilation (and symmetric) and should experience smaller distances and slower time. So it can proove, there is no absolute world, because how can you experience smaller distances than they are in reallity. But if there was an absolute world somewhere where we are part of, we can't detect that because of our light behavour (giving time dilation, time fields etc.).

So I mean that IF there was an absolute world (what it means is up to you), Einstein was still valid because of the behaviour of light (the question is, would an absolute world having the same light behavour).

What V > C concerning, my own thinkings are that V can be greater C, an object goes than not back in time (negative time dilation) but it will getting older as in a situation as the twin paradox. Like in the twin paradox you could coming back older and you will see during your trip the clock going backwards. Otherwise you could not see an object from two frames. E.g. you meassure the speed of a neutrino > C and you still detect the neutrino, but the neutrino itselves sees the clock going backwards and thinks to go faster than time. It does not go back in time (I find that always nonsense, science fiction, many contradictions) as in a twin paradox situation. E.g. a person can going slower older but also faster older, I think it does not mean more.

I agree with Ghwellsjr in older topics, time does not exist generally, only a relative time between two events, and that both consider the same time dilation is in fact logic, if time is going slower in one direction, it must be going slower too in the other direction (it is not something as a waterfall). To send a signal over to the other must be going even so fast as one sending back meassuring in time (otherwise not logically).

But I think you could setup a time system between places in the universe with one center (by appointment, e.g. earth) all seen from Earth around us, with the behavour of light, with computercalculations (but not really think about that) ..

Except with the twin paradox, I understand now too, that if both moving persons have a time dilation, it has nothing to do with their age, but only with the time needed to transport something to each other like a signal expressed in times belonging to their frames. It is not important to see a clock in another frame (it is not your situation, but you can calculate his clock time and the other way).

We messure in our frame a speed > C (the neutrino's frame speed), the neutrino has a negative time dilation, and compared to the neutrino we too. So we can calculate times for sending signals to each other. Maybe it would be possible that the speed above C can be at a maximum 2C (bot not equal 2C). Something we send is immediately there.

It are all only thoughts, I am not studying physics .. only to read about subjects and to think about that ...

9. Nov 30, 2011

### atyy

There is no absolute point in special relativity, because it is an affine space, not a vector space (which has an absolute point).

10. Dec 1, 2011

### digi99

I think an absolute object or something else, is that what is left after removing all moving objects. So maybe our space would be empty. If you have only absolute objects, relative time is even not existing and Einstein has nothing to do in such environment. As soon something is moving, Einstein relativity comes in view and as long a light signal is the same as for us, time dilation is there too and relative times are existing. Even when distances are absolute between the absolute objects, for the moving objects distances are different (just an effect of moving, but real distances can be recalculated).

So IF there was something absolute elsewhere, we don't know ...

By the way what I said in my last answer, something we send is immediately there is not true, it takes just the time meassured in its own frame.
I think time V=C is also not possible too (e.g. a person would not be alive at time V=C I think), it's a step to be taken.

11. Dec 18, 2011

### sandu123

I think absolute object,and absolute time are itself misnomers.
The last statement,about a person being alive at v=c is not important,i think ,because,we need not be in the accelerating frame in order to measure the speed then.
Recent experiments at Gran Sasso have hinted towards neutrinos violating the photovelocity limit.I believe that even if the so called 'tachyons' and other particles faster than photons are being discovered,it need not violate the relativity theory completely.
If I am being wrong,would someone please explain in detail to me??I am a physics student and I am extremely interested in such discussions

12. Dec 18, 2011

### my_wan

I can't really be sure be sure just exactly in what sense digi99 intends the term "absolute point", but if restricted properly is not to entail a point against which absolute motion can be measured the consequences of the supposed absoluteness can be characterized. In fact the thought experiment digi99 proposed essentially entails an inability to use such an absolute characterization of a point as any sort of reference against which absolute motion can be measured. In that sense all points have the character being described.

To illustrate you merely need to associate the symmetries of an affine space with a non-physical coordinate choice. Then supposing the individual points have some form of absolute character, independent the apparent relational character among sets of points imposed by a coordinate choice, it would entail that observables, however unique to a given coordinate choice, must be relational by some transform which is valid for all coordinate choices. This is precisely the first postulate of special relativity, i.e., the physical state and dynamics of the physical system, or absoluteness of the individual points, are unaffected by our coordinate choice used to characterize it. Likewise the laws of physics are the same for all inertial frames, irrespective of any apparent incongruence between a pair of observers.

To prove individual points do not have any sort of absolute character requires showing the observation in one frame cannot be consistent with an affine transform of space as viewed by another. That requires a violation of the principle of relativity. Also, another effect is that no such transform can result in a rearrangement of the sequence in which an event set are observed. Only the rate at which they progress through that sequence and the apparent geometry in which they occur.

To say that a vector space has absolute points distinct from an affine space is misleading. A classical vector space undergoes the same affine transforms as an affine space, hence Lorentz invariant QFT. Yet observed experimental results are always consistent just like the end result of modeling the consequences of the relativity of rigidity is always exactly the same as if you presumed no such transforms ever took place. What is wrong with a classical vector space is not the reality of the points, but the notion that positions, velocities, and recoil angles share a common absolute affine free metric under any coordinate choice. An observer, defined not in but by a vector space, must always perceive their own state as normalized to a self referential standard, regardless of how distorted they may appear to another self referential standard. Vector spaces are NOT free of affine transforms even if we can often pretend they are much like we can ignore the relativity of rigidity in predicting end results.

----
Given that the absoluteness of a given coordinate choice went the way of the dodo bird in 1905 while maintaining the reality of the individual points, why is it that every time somebody mentions reality it is immediately thrown in the same category as a coordinate choice? When Einstein opined that the moon existed when nobody was looking it wasn't a purely philosophical objection. It went straight to the heart of how relativity defined reality as a distinct and absolute thing that was distinct and independent of any given absolute coordinate choice. The same distinction between physical state and coordinate choice upon which the principle of relativity was posited. To then reject the absoluteness of a physical state on the grounds that the coordinate choice used to characterize it is purely relational and demonstrably without any absolute meaning is a strawman. Einstein wasn't simply being obstinate in his clinging to reality, yet every counterargument involves throwing in the very coordinate dependence that he explicitly demonstrated was an observer dependent perspective of the relations or between states. It's like saying libraries can't be real because the Dewey decimal system is not a physical thing.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook