Can we make a standard Universe clock?

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Discussion Overview

The discussion centers around the feasibility of creating an absolute standard Universe clock, exploring the implications of gravity, velocity, and the nature of time as described by general relativity. Participants consider theoretical and practical challenges, as well as the influence of cosmic phenomena on time measurement.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants argue that creating an absolute standard Universe clock is difficult due to the need to eliminate the effects of gravity and velocity.
  • One viewpoint suggests that a point in space without gravity and motion could allow for precise time measurement, but this scenario is hypothetical.
  • Another participant emphasizes that achieving a state of rest with respect to the Cosmic Microwave Background (CMB) is only possible approximately, not perfectly, and requires significant adjustments to account for cosmic motion.
  • Some researchers are noted to promote Modified Newtonian Dynamics (MOND), indicating that time is relative and that a unique coordinate system cannot be assigned under general relativity.
  • One participant argues that without gravity, there would be no mass or reference points to define coordinates, complicating the establishment of a standard clock.
  • Another contribution discusses the concept of being at rest relative to the CMB, suggesting that this could serve as a standard for time measurement in cosmology.
  • Participants mention the need to correct for various motions, including the Earth's motion around the Sun and the Sun's motion relative to the CMB, to achieve a standard clock.

Areas of Agreement / Disagreement

Participants express differing opinions on the possibility of creating an absolute standard Universe clock, with no consensus reached on the feasibility or methodology. Multiple competing views remain regarding the nature of time and the implications of general relativity.

Contextual Notes

Limitations include the unresolved nature of assumptions about gravity and motion, as well as the dependence on definitions of rest and standardization in cosmological contexts.

physalpha
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Is it possible to make an absolut standard Universe clock?
I think it's not easy to make that knid of clock.
The effects of gravity and velocity should be removed.
If there were a point not moved and no gravity in the Universe, we could measure the time exactly.
In the Earth, are we able to do that work?
Moreover recently some researcher say physical constants have been varied.
 
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physalpha said:
Is it possible to make an absolut standard Universe clock?
I think it's not easy to make that knid of clock.
The effects of gravity and velocity should be removed.
If there were a point not moved and no gravity in the Universe, we could measure the time exactly.
In the Earth, are we able to do that work?
Moreover recently some researcher say physical constants have been varied.

only approximately, not perfectly.

Get way far out away from any galaxy or cluster of galaxies so that you don't have the effect of being down in a gravity well.

Then adjust your motion so that when you measure the microwave background (the most ancient light, from about year 380,000) there is no Doppler hotspot in the sky. That is, you are not moving with respect to ancient light. This adjustment is only possible to within about 1/1000 of one percent, I guess. You can only say that you are approximately at rest.
 
Some reserchers are still promoting MOND. Time is relative. There is no way to assign a unique coordinate system to any 'clock' under general relativity.
 
I don’t think it’s possible to make an absolute standard Universe clock.

If there was no gravity in the Universe, then there would be no matter. Mass defines space-time. If you were a point in empty space and you had no mass and no volume, then there would be no reference points to establish x, y, z coordinates, and no way to establish how those coordinates change with time.

Imax
 
Last edited:
Then which one is correct?
The standard is the same velocity state as the Universe expansion.
The standard is not moving state.
 
marcus said:
only approximately, not perfectly.

Get way far out away from any galaxy or cluster of galaxies so that you don't have the effect of being down in a gravity well.

Then adjust your motion so that when you measure the microwave background (the most ancient light, from about year 380,000) there is no Doppler hotspot in the sky. That is, you are not moving with respect to ancient light. This adjustment is only possible to within about 1/1000 of one percent, I guess. You can only say that you are approximately at rest.

physalpha said:
Then which one is correct?
The standard is the same velocity state as the Universe expansion.
The standard is not moving state.

there is no difference. In Cosmology, the ancient light of the CMB is the standard of rest.
If you have no doppler hotspot in the CMB sky, then you are at rest with respect to the ancient matter that emitted the ancient light.
It has been called "comoving with the expansion" or "comoving with the Hubble flow" but those are just words that mean the same thing as being at rest relative to the Cosmic Microwave Background.

In cosmology one does a change of coordinates so that the data is recorded as if from an observer at rest. We deduct for the Earth motion around sun and we deduct for the the sun motion relative to CMB. We know that the sun is going 380 km/second in a certain direction relative to CMB (because can see doppler hotspot around constellation Leo the Lion.)
So before recording the other CMB data or the redshift data we can correct for the sun's 380 km/second motion. Then the data is AS IF SEEN BY OBSERVER AT REST.

To make a standard clock you should also correct. In effect you should locate the clock on a body which is at rest relative to the universe's ancient light.

Do not think of expansion as motion outwards from a center. Expansion is the increase of distance between objects which are at rest with respect to CMB. It has no center. There is no "outwards" motion, only increase of distance between objects at rest.

Think of points on a balloon surface---each one stays at the same latitude longitude, each one is at rest, but distances between them grow. They do not know of another dimension. Each one can only observe his neighbors on balloon surface. He can not observe another direction inside or outside the balloon. Nor can we observe any other direction besides our 3. And so for us the distances between stationary points can increase and that is just how it is. General Relativity allows geometry to change so it is not too strange that this happens.
 

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