What is "the fabric" of space-time?

Yes, well done. You have grasped the concept of space that most had from 3000 years ago to about 100 years ago. You've only 100 years to go to catch up. It can't be that hard...Given that your understanding is so out of date, it seems a liitle superfluous trying to sort out the rest of your post line by line. If you think of an ocean as space, and waves on that ocean as matter or stuff, then you're not too far off our current understanding. I'm sorry, but GR is one of the two most successfully tested theories ever devised by mankind - admittedly not all of the evidence was gathered by Einstein himself, but does that matter???If you are interested in this evidence, you may want to look intoAdvance of the Perihelion of Mercury
Gravitational wave emission from binary neutron stars
Pound-Rebka experiment
Effect of GR on the GPS sattelite system
Gravitational lensing
Existence of black hole-like objects in galactic nuclei (including the centre of our own Galaxy)That's a start - let me know if you find any problems with any of these.Edited by cavediver, : No reason given.

Again, your understanding is a good 100 years out of date. What makes something physical? When you pick up an apple, what enable you to touch it? What stops your hand passing through the apple? What makes up the mass of the apple? The answer to all these questions is 'force'*, something unphysical according to you. How do you square this with your understanding? There is not as much difference between "physical" objects and "empty space" as you'd think...* electromagnetic force in the case of the soliidty of the apple and the hand;, and mainly the chromodynamic (strong) force in terms of giving rise to the apple's huge mass (with respect to the total of the quarks and leptons rest masses that make up the apple.)Edited by cavediver, : No reason given.

As I pointed out, you have an outdated erroneous definition of "physical", so what are you going to gain by an answer to this question? You think that physical means "having substance", "tangible", etc, which are reasonable definitons for Newtonian mechanics and gravity. And space in a Newtonian sense is obviously not "physical". But we are talking about space-time, something far beyond Newtonian concepts, and it is not something that can be described as being, or not being, something (i.e. "physical") that only relates to Newtonian concepts.So, yes, space-time is physical, but to understand this, you need to understand what physical means. In physics, we describe everything in terms of fields. Matter (electrons, quarks, etc) are one type of field, forces (photons, gluons, etc) are another type of field, and space-time (which gives rise to the sense of distance between objects in the Universe) is another type of field. These fields are so similar that we think that they are different manifestations of just one field. So matter, forces, and space-time are all physical. In my last few posts I have given you more than enough experiments and key-words for you to Google and Wikipedia your way through this information to satisfy yourself. Or you can pick up any decent advanced graduate particle-physics/relativity text book and start learning properly, assuming you have a suitable grounding in the undergard maths and physics.Feel free to ask any questions regarding this, but if you are going to simply repeat your erroneous assertions, such as then I am going to ignore you, or at least offer you my (not particularly competitive) rates for teaching annoying students advanced physics...Edited by cavediver, : No reason given.Edited by cavediver, : No reason given.

Unfortunately, you show no interest in learning anything and so I have nothing more to say to you. Enjoy wallowing in your own ignorance If anyone else is so stupid as to think that they can debate advanced science topics using everyday dictionary defintions, please think twice before posting...

What with this reply SG just submitted, and his recent reply to randman, it seems that SG's keen resolve and determined patience are starting to show the very first signs of cracks. Reminds me of someone else, much further along the road to complete dispair Edited by cavediver, : No reason given.Edited by cavediver, : No reason given.

think that should be *wrapping* Yes, this is definitely one way to think of it. It is not that we are seeing the distant galaxies and quasars moving away at velocities that they were moving away from us at that time, which would be the case if this were simply a Doppler effect. The Universe has been expanding as the photons have been travelling towards us through the billions of years, and this expansion is the reason for the red-shift.There is actually a far far simpler explanation, which I may as well mention as you brought up "light-cones", despite it requiring more insight into space-time physics. As you may know, photons actually have no "length", as the proper distance between the emission and absorption of a photon is zero (think of infinite length contraction), and there is no time between emission and absorption (think of infinite time dilation.) So how does the red-shift arise in this context? It is simply a result of the light-cone at emission pointing in a different direction to the light cone at absorption. The photon allows us to overlap the light cones (despite being separated in our minds by billions of years and billions of light-years) and take a measurement of the difference between them.Edited by cavediver, : No reason given.

Ok, let's say I have a light source - that wavelength/frequency of the light is measured relative to the time axis of my own light-cone. Relative to a light-cone that is tipped over somewhat, the light will appear to have a longer wavelength, lower frequency, and hence red-shift, because the ticks of a clock measured in the first light cone, will tick more slowly when measured against the time axis of the second light cone (and vice-versa). Cosmological curvature is what causes the two light cones to be tipped wrt each other, and the photon joining the two light cones is what enables us to compare their relative tipping.Edited by cavediver, : No reason given.

Not really, when you have done such an admirable job yourself.There is no point describing the evidence to you because there is no one simple experiment to demonstrate this to you - it is a body of work and observation built over the past 100 years. I have already mentioned gravitational lensing, which is probably the most direct evidence, but you have obviously failed to look this up - again showing your complete disinterest or inability to study.I'll tell you what - you're right, I've been wrong all this time. Space isn't physical - it is simply a place where physical things can be. You win. Also, dictionaries are the perfect learning place for scientific concepts and theories - you were right and I was wrong. I concede the debate 100% to you.

Yes John, you tell Son Goku. There's no better way to look intelligent than to tell a practising Theoretical Physicist to look up physics topics on Wikipedia Edited by cavediver, : No reason given.