DParlevliet

In the new exibition of the museum Boerhave in Leiden (Netherlands) I saw the MiniGRAIL, a gravitational wave measuring device which prooved to be not sensitive enough. It was based on mechanical resonance in a copper ball. So gravitational waves loose energy in mass.

I think this part of a publication gives the answer. Only free masses will follow the gravity wave, with solid mass the atomic forces prevent this mostly (except elastic):

I have been looking for a scientific description of LIGO and gravitywave detection (difficult to find) and found a probably misunderstandig from me. According Wikipedia: "measure gravitational-wave induced motion between separated 'free' masses" and another website: "uses widely-separated test masses freely suspended as pendulums". So the mirrors are not fixed on a solid base as I expected, but can freely move and therefore follow the gravity wave, without interatomic forces preventing it. But there is still the question of a solid metal ruler and: Simple answers "no" and "different phenomena" are no science. Explain what is the physical effect on space of space expansion and gravitywave and differs in what. I think only in the shape. Expansion/scrinking of space results in large/smaller distances in space and a gravitywave does the same. So why would in one case interatomic forces prevent this in a solid mass and in the other case not?

Or a better question: suppose the arms of the LIGO are made of solid iron on with de detectors/mirrots etc. are build. If a gravitywave passes this iron, why would the interatomic forces not prevent the space expansion or contraction of the wave?

Is a gravity wave also a natural expansion/contraction, but now in ~~sinus schape? Or: what is the difference?

But if the universe would be solid iron.

So when the universe would be fully (homogeneous) massive mass, this mass would expand with space and the distance between atoms would be expand too? When this type of universe would be half the present size, the distance between atoms would also be half the present distance?

Nothing, but the difference of theory is important. As a result of StringJunky's answer: LIGO measures an invariance in licht speed during a gravity wave, so not a constant light speed. I have never realised that. So when we were there when the universe was half the present size, we would measur a different light speed: twice faster or slower (not sure yet what).

Why? What is the diference between expanding universe, and expanding during a gravity wave. Both are expanding space. I think the arms are not expanding/shrinking, but the space in between. Only light is effected by that. Now I understand why one cannot measure a gravity wave with a ruler: it would measure no expanding/shrinking of the arms because there is none. It's the space between the detectors which expands/shrinks.

Brian Greene mentioned it as being a force. So a ruler will not expand with space and so will not follow a gavity wave, which essentially expands/schrinks in sinus form.

But what about the size of a planet. I have read that a planet does not expand, because the force of the expanding universe is very small compared to the atomic forces. Then I would expect that a ruler also does not expand. Or an other example: at the time the univers was half its present size, would the earth (and distance between atoms) also be half the size?

A gravity-wave expands/schrinks space. If a mechanical ruler would expand/schrink in the same way, it is not possible to measure the gravity wave with a mechanical ruler (in theory, in practice it is not possible anyway of course). Or simple: if space expands, does a ruler expands with it?

On the radio I heard the explanation of a scientific writer about measuring gravity waves (or better: space waves). He told that in principle one could not measure these with a ruler, because this would follow the wave (therefore it is measured with light). However I also read that while the universe (space) is expandig, that matter does not expand in the same way because the forces between atoms is much larger then the expension forces of space. But to my understanding a gravitation wave is an expension/shrinking of space in sinusform. So why would a mechanical ruler follow these waves?

I suppose that in Einsteins equations there is time, which always proceeds, and that is the "movement" in the fourth dimension we are talking about. In the model that is visualised by multiply time by c, then all four axis have the same dimension space in which there is always (invisable) movement in the time axis. In the model of Migl the same: the travel North is the movement in time. A model without movement would be a model without time, and that is really not reality.

It was a reply to studiot, not to you. Indeed if two objects does not move relative to each other then gravitation (by curvation of spave) can only be explained in a model with movement in time. Thats is what the video showed. That is what Migl showed if one of its axis is time. But studiot did not agree with the video. Then explain how gravity exist in the case Sooryarikan proposed.

There is a curvation in 2D, but without movement there will be no approaching each other. The approaching is caused by the travel North (combined with curvation), so by a movement. Wich movement? I don't think a 3D has properties that do not exist in 2D as long as there are no movements in the 1D which is disregarded. That follows also from the relativity. Properties does not change is a 4D rotated of displaced. That can only be true if all properties exist equal for all axis of subset of axis.

Indeed Sooryakiran was more accurate then me, but that does not change the subject. If both masses (and observer) does not move relative to each other there is gravitation. That cannot be explained by (relative) movements in space-3D. Multidimensional systems can be simplified to 2D dimensions without any change in effects as long there are no movements in the other dimensions. So that is no model, it is a simplification with follows all relativistic rules.

Indeed, but that supposes there is a movement in the time axis, like in the video. I agree with you answer earlier but oppose MigL and Studiot. Their explanation supposes movement in the time axis and that is the analogy they don't agree.

But the question of Sooryakiran was about the situation where there is no movement (in 3D), no travelling to North.

According Einstein the gravity is caused by curvation of Spacetime. I understood that the formula of this curvation is the Riemann curvation tensor. So should this formula with the proper approximations result in Newton formula of gravity? Or how is it mathematical proven that gravity is caused bij curvation?

Decay is not fully random. It has a distribution around a certain decay time, specific for that decay. This time must be determined by something. Real random times has to pattern or predictability, so cannot be used to measure time.

It is useless talking about items we don't know. As long as there is no prove that quantum effects are related to movement, it is a different way of time measurement. However the decay C14 is not purely accidental. It has an average time. So something in the atom is determining this time. I cannot think of any other fundamental natural unit then movement (for instance as oscillation deep inside the atom). But that is my guess, no proof.

Thanks for the explanation. So the same as for C14 timing, from quantum effects we don't know the cause, so don't know where it depends on. Deep down it could be related to distances, but we don't know. I relaised that you can measure time by any fundamental natural unit which changes in time. This is mostly length (distance), perhaps quantum effect, or a clock could be based on changing temperature. I should not know any other.

Why are relativity (and kwantum) fora always so angry. What a dreadful profession it must be, where discussions are not possible without personal attacts within a few posts. See the question-mark in my first post,. A question-mark means I am asking, because I don't know (am not sure). If I knew, I would not post it. There is not a single post in which I pronounce myself an expert, because I am not. I just discuss with arguments. Regarding atom clocks, Wiki tells: "it uses the microwave signal that electrons in atoms emit when they change energy levels." So it depends on energy levels of electrons, which I think is potential energy depending on the electron (average) position/distance from the atom core In an oscillation crystal the movement of the cystal is measure, determinded by the distance and elastic properties. This is done multiple times in two directions. It does not matter if all those add up or not, that is the way of measuring. Also mechanical clocks have an oscillating net movement, but by its construction it adds up in moving wheels. A mechanical clock without pendulum also measures time, but inaccurate. The pendulum provides accuracy, and indeed also depends on length.

Indeed, that is what I mean. The fourth time dimension is impossible to see directly by us, so it is measured by its effect in 3D space, so by the only other dimension in there: distance. In the example one measures the movement of water (in the restriction). Often time measurements depends on energy decrease, analog or in steps. But energy is potential or kinetic, both depending on distance. - Atomic clocks are based on the wavelength of radiated photons, which is determined by the jump of electrons between orbits inside the atom. - I don't know charge clocks, but (dis)charging is caused by moving electrons over a distance in a field. - A pendulum clock measures the rotation distance of wheels. - As geordief told: if you don't know the cause of decaying muons, you don't know if distance is involved or not. The same for C14 dating. - The time measuring part of a talking clock is the same as any other clock - How do you measure time with spin flip?