What is Time?

[klaus54]

No, every object moves through space-time.





We don't understand time yet. It seems better to say, though, that velocity effects the observer's perception of spacetime or measurements made in it.

Do you know about the Doppler Effect? It is very much related to time dilation. If you don't know, you should read up on it.




No, that's probably not the right way to view the evolution of space-time. Common sense says that photons do not think.

Affect = v. to influence

We DO understand how the reckoning of time changes for observers in different reference frames moving relative to each other. That's been stated in this thread several "times". For those calculations the philosophical notion of what time IS is irrelevant. The calculations are based on the FACT that the speed of EM radiation in vacuo is a universal constant.

[klaus54]

'Photon' doesn't have motion defined in 3D.

...

Our binoculars and telescopes are designed based on the assumption that photon trajectories are wholly in space-time (3 spatial and 1 temporal coordinates in Minkowski's model. Do the telescopes and binoculars not work well?

Yes. E.g., a photon leaving Sol's photosphere takes about 8 minutes to reach Earth. It has to travel through space and time to do this.

[seer]

OK, from what I'm getting here is that time is relative.Then how do we know the age of the universe, what is that relative to?

[Roy]

OK, from what I'm getting here is that time is relative.Then how do we know the age of the universe, what is that relative to?

The orbital and rotational periods of the planet and the vibrational frequency of caesium atoms.

The age is determined by many factors including redshift measurements, CMBR extrapolation, extent of visible universe, radioisotope presence.

I recommend this link.

[seer]

The orbital and rotational periods of the planet and the vibrational frequency of caesium atoms.

The age is determined by many factors including redshift measurements, CMBR extrapolation, extent of visible universe, radioisotope presence.

I recommend this link.

Wait, I have been told a number of times that time is relative to the observer's perception or frame of reference. Is that not true, that time is independent of the observer's perception or frame of reference and not relative?

[oxmixmudd]

Wait, I have been told a number of times that time is relative to the observer's perception or frame of reference. Is that not true, that time is independent of the observer's perception or frame of reference and not relative?

Most frames of reference on the Earth or in the space around the earth over a distance of several hundred million light years involve frames of reference where the relativistic time dilation effects are inconsequential relative to the ages measured.

Exceptions to that would found be near objects like black holes and neutron stars, or when dealing with high velocity subatomic particles.

Jim

[seer]

Most frames of reference on the Earth or in the space around the earth over a distance of several hundred million light years involve frames of reference where the relativistic time dilation effects are inconsequential relative to the ages measured.

Jim

So in reality, looking at the whole, time is not at all relative and is fixed?

[klaus54]

Wait, I have been told a number of times that time is relative to the observer's perception or frame of reference. Is that not true, that time is independent of the observer's perception or frame of reference and not relative?

Space-time intervals are independent of reference frame.

[klaus54]

So in reality, looking at the whole, time is not at all relative and is fixed?

Total botch of a "relatively" simple concept.

ETA: The relativistic time differences that Jimmy is talking about would not change a time interval of tens of millions of years into thousands, e.g.

[X6_]

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Our binoculars and telescopes are designed based on the assumption that photon trajectories are wholly in space-time (3 spatial and 1 temporal coordinates in Minkowski's model. Do the telescopes and binoculars not work well?

In QM, photon doesn't have a trajectory (in 3D). Light, photon, radiation are not synonymous. Electromagnetic waves are built up of a lot of photons. But you can't talk of a motion of a single photon, because you can't distinguish one photon from the other. Is it the same photon or the copy?.. As if a photon leaves the 3D surface, the detector loses track of it. If detector can't keep track of a thing, and can't distinguish one thing from the other, whose motion can it track? Maybe about motion of a electromagnetic wave as a whole only we can talk. But, both SR and QM are phenomenological models, they only say how certain things look like. We can have infinite number of contradictory phenomenological models, so take them all easy.

[JimL]

Okay, okay, so can anyone define time as a thing in itself? Does it move from past to future, does it stand still, or does it even, as a thing in itself, exist? If it stands still, if it is just a coordinate of space, then what exactly is meant by the "passage of time"?

[Roy]

The orbital and rotational periods of the planet and the vibrational frequency of caesium atoms.

The age is determined by many factors including redshift measurements, CMBR extrapolation, extent of visible universe, radioisotope presence.

I recommend this link.

Wait, I have been told a number of times that time is relative to the observer's perception or frame of reference. Is that not true, that time is independent of the observer's perception or frame of reference and not relative?

Ok, so you're not interested in answers, you're just doing your usual dishonest schtick of asking questions until some-one says something you can twist to support your predetermined conclusion.

[Truthseeker]

Wait, I have been told a number of times that time is relative to the observer's perception or frame of reference. Is that not true, that time is independent of the observer's perception or frame of reference and not relative?

Each frame of reference carries its own clock. Perhaps an experiment starts with synchronizing the clock in frame A and the one in B. Perhaps in the course of the experiment the clocks become unsynchronized as in the twins paradox.

Now, do we say that A's clock's tick-tocks are relative to . . . which frame of reference, A or B? That question is worthless. All we can say is, each frame of reference carries its own system of clocks. ToR experiments always involve more than one frame of reference, because ToR predicts differences between at least two frames of reference, e.g., B's ticktocks may differ in interval from A's ticktocks. Length measurement in A may differ from B.

Why do you think it's possible to infer from those experimental data that time is not relative? Maybe such a concept is not meaningful in ToR.

[oxmixmudd]

Okay, okay, so can anyone define time as a thing in itself? Does it move from past to future, does it stand still, or does it even, as a thing in itself, exist? If it stands still, if it is just a coordinate of space, then what exactly is meant by the "passage of time"?

'move', 'past', 'future', 'stand still'. All of these implicitly assume what time is, so using them to try to describe time is circular. I struggle with it too. But at this point I would define time as the most fundamental or basic element of the universe which itself enables change in the universe. And I would approach it from the standpoint of a definition. I use the word enable because time does not itself require change, but without time there can be no change.

I don't think this definition is in any conflict with the physicists definition or use of time. And I don't see any conflict with this and how time is dealt with in GR (LM?), but for me it captures more of what time is than the physicists definition of time does.

Jim

[shunyadragon]

In QM, photon doesn't have a trajectory (in 3D). Light, photon, radiation are not synonymous. Electromagnetic waves are built up of a lot of photons. But you can't talk of a motion of a single photon, because you can't distinguish one photon from the other. Is it the same photon or the copy?.. As if a photon leaves the 3D surface, the detector loses track of it. If detector can't keep track of a thing, and can't distinguish one thing from the other, whose motion can it track? Maybe about motion of a electromagnetic wave as a whole only we can talk. But, both SR and QM are phenomenological models, they only say how certain things look like. We can have infinite number of contradictory phenomenological models, so take them all easy.

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