0 Members and 2 Guests are viewing this topic.

Quote from: Hal on 27/12/2020 18:40:06My arguments so far assume uniform gravitational field and hence consider only the effect of absolute motion. Gravitational time dilation isn’t a function of the uniformity of the gravitational field. It’s a function of the gravitational potential.So for instance, a clock on Earth will run faster than one sitting on Mercury despite the stronger gravitational field on Earth. A rock in freefall just above Earth will undergo greater coordinate (absolute) acceleration than a rock in freefall just above the surface of Mercury. There’s thus a stronger field just above Earth, and yet less dilation.Another example is the uniform field inside a hollow region inside something like Earth. Completely uniform field inside that hollow (per Newton’s shell theorem), and yet clocks there will be more dilated than a clock sitting on the surface.So your assumption of a uniform gravitational field doesn’t allow your clocks to keep absolute time. To do that, you’re going to need to measure absolute gravitational potential. Is Silvertooth going to similarly just assume that Earth’s surface is at maximum potential just like he assumes Earth to be (incredibly near) the exact center of the universe?Quoteand zero gravitational field around the clock. ( But any non zero constant velocity and non zero constant gravitational field should be possible, but I just prefer zero values).Since one can move upward from a clock on Earth, it is not at zero potential. Zero potential is the potential of a universe with zero mass in it. To compute the potential at Earth then, one only needs to account for all the mass of the universe. The computation isn’t all that difficult if you assume uniform mass density above a certain scale. A few minor adjustments from there to account for the planet, sun, galaxy, and not much else. But the mistake is to wave the computation away and assume it needn’t be done.How old is the universe currently? According to Earth clock, it is about 13.8 BY old, but that clock is dilated by some percentage. So what's the real age?

My arguments so far assume uniform gravitational field and hence consider only the effect of absolute motion.

and zero gravitational field around the clock. ( But any non zero constant velocity and non zero constant gravitational field should be possible, but I just prefer zero values).

I still prefer ‘gravitational field strength’ , not ‘gravitational potential’ , description of gravitational ‘time dilation’ effect. My reason is that there is no way to have an absolute clock if gravitational ‘time dilation’ depends on gravitational potential because gravitational potential cannot be sensed/detected at a point in space.

There is no sensor to detect gravitational potential at a point in space, so that it can be used for automatic correction of clock rates.

Therefore, my absolute clocks will have gravitational field sensors onboard to automatically correct their rates by using correction tables, to stay in synch.

The question is: is it theoretically possible (according to GRT) to have an (atomic) clock that automatically adjusts its rate with altitude? For example, an onboard system senses the gravitational potential to automatically adjust the clock rate. But there is no sensor for gravitational potential at a point of space. There can only be a gravitational field sensor.

So, according to general relativity, there is no way to automatically adjust clock rates with altitude.

This raises yet another question. If there is no sensor for gravitational potential, how can the rate of an atomic clock respond to changes in gravitational potential in the first place?

In other words, general relativity predicts that gravitational time dilation cannot exist.

How old is the universe currently? According to Earth clock, it is about 13.8 BY old, but that clock is dilated by some percentage. So what's the real age?

So a question comes to mind as to which is the correct way of calculating the potential from the surface of a body ?

As i am then not sure if it makes a difference to an atomic clock when factoring in the suns time dilation for midday/midnight on the surface of a body like mercury/earth makes a difference in this regard.

There isn’t an altitude sensor either. OK, airplanes have them

There is no way to detect absolute gravitational potential, but there is a way to detect the gradient and direction.- Some of the most accurate atomic clocks have been used in an experiment where they were synchronised to each other, and then one was raised by 1 foot, and the difference in clock rates was measurable.

As you say, this is not exactly a local measurement.

There is no way to detect absolute gravitational potential, but there is a way to detect the gradient and direction.- Some of the most accurate atomic clocks have been used in an experiment where they were synchronised to each other, and then one was raised by 1 foot, and the difference in clock rates was measurable.- These accurate atomic clocks are not portable, but the next generation of optical clocks should be able to measure the gravitational gradient.As you say, this is not exactly a local measurement.So you may as well make use of other non-local measurements, like radio signals from Earth, proximity to the Sun or another planet, etc.

There’s no sensor to detect field strength at a point in space either.

Gravitational potential at a point in space can only be calculated, it cannot be physically sensed, whether by using potential gradient or by using non-local measurements (such as radar ).

Also suppose that an atomic clock is not transported from earth, but somehow built at a point in space. How can such a clock 'know' the gravitational potential at that point, so as to speed up accordingly ?

The atoms in the clock have no 'radars' to measure distance from earth and no 'calculators' to compute their potential.

So, if we claim to adjust a clock based on its gravitational potential which we calculated from non-local (altitude) measurements, it would be wrong and artificial.

Also imagine a clock that is affected by thousands of stars and planets.

It would be very difficult (according to GRT's gravitational potential) to keep such a clock in synch, whereas it can be corrected instantly based on gravitational field.

If this was the case, a stone thrown up would not fall back to the ground.

Quote from: gem on 15/01/2021 01:04:10So a question comes to mind as to which is the correct way of calculating the potential from the surface of a body ?They're all correct. None of the statements you posted are mutually contradictory. You're right, the potential goes up and down at various locations based on what's nearby. The potential difference between the sun's surface and Mercury is massively more than the potential difference between Mercury and the 'edge of the solar system', wherever that is.QuoteAs i am then not sure if it makes a difference to an atomic clock when factoring in the suns time dilation for midday/midnight on the surface of a body like mercury/earth makes a difference in this regard.The potential on one side of Mercury isn't the same as on the other. Ditto for Earth. 'Stationary' clocks at sea level run faster at night.

If what I posted is not mutually contradictory why do I get a different time dilation value for each scenario ?

I understand why clocks would run faster at night due to increased potential

it's the aspect of whether the suns potential is oriented at the bottom or top of the clock on the surface of mercury/earth makes a difference.

So what I am trying to nail down is which scenario of the velocity/gravitational red shift will the atomic clock show.(A) To edges of solar system; escape vel earth + escape vel sun from earth dist or(B) towards sun ; escape vel sun from earth distance - escape vel earth

I start by arguing that the failure of classical theories of light, ether theory and emission theory, wrongly led to the theory of relativity.

In what way have Maxwell's equations failed?

Quote from: Hal on 23/09/2019 09:22:07I start by arguing that the failure of classical theories of light, ether theory and emission theory, wrongly led to the theory of relativity.In what way have Maxwell's equations failed? When I detect individual photons, where has Planck's theory failed? If we add the relativistic correction for gravitational potential, where does the Pound-Rebka experiment fail to support relativity?

the speed of light reference