Discussion in 'Science, Tech, & Space Exploration' started by Thomas R. Morrison, Oct 25, 2018.
If gravity isn't reletave, Does that rule out Quantum Gravity as well?
Yesterday I read a detailed response to a question raised online by a Nobel laureate physicist who asked if the radiation coming from the galaxy clusters could explain the dark energy effect. It turns out that no, that doesn't work. The electromagnetic waves and the gravitational waves which are constantly being emitted from galaxy clusters, are much too small to explain the acceleration (and of course, the intensity of those waves drops off with distance, whereas the dark energy effect gets stronger with distance).
No. None of the other forces in the Standard Model are relative either, so that's not a problem. The problem is that gravity is an acceleration - a warp in spacetime, rather than a conventional force with conventional exchange particles. So quantum field theory and general relativity speak entirely different languages, and nobody's been able to translate one into the other yet without coming up with all kinds of infinities that break the equations.
The cyclical universe model appears to be ruled out at this point, because the cosmological acceleration is increasing, not decreasing, and it's being doing so for about 6 billion years. I suppose that someday it could begin decreasing, and eventually reverse sign, but we see no reason to anticipate that.
It appears now that the universe will keep expanding until each galaxy cluster is alone and all of the others have moved beyond the cosmic horizon. Eventually all the stars will die out, radioactive decay will get slower and slower, and everything will be consumed by a single remaining black hole. And if Hawking is correct, that black hole will slowly evaporate as it emits photons, until quadrillions of years later it shrinks to a very small size and explodes in a blast of electromagnetic radiation, and that will be the end of matter for all eternity. Pretty bleak.
It makes me wonder, To someone that loves Science as I do, I look at Einstein with great esteem, He was a great man and still is, But, I wonder sometimes if we are now living in a time that we are actually seeing some of his theories disproven?
It's very tempting to think that dark energy and dark matter indicate a flaw in the general theory of relativity. But in every observational test that's been conducted, it still passes with flying colors. I saw a new test of GR using gravitational lensing, and that worked out to within observational error too.
All we really know for sure is that both the standard model and general relativity are incomplete, and even Einstein knew that, which is why he spent the rest of his life looking for a unified field theory. The universe works as a single system, so there must be a single equation to explain it all. It's maddening that we haven't figured it out yet. And it's bizarre that all of the predictions of both theories have been proven - that's why nobody knows the best path forward.
Dark energy and dark matter are the only two phenomena that don't fit into either theory. Damned peculiar, is what it is.
No that's not insane at all - in fact Manu Paranjape and his grad students published a couple of papers about this kind of thing recently. In theory, it appears to be possible to create a bubble with a high enough surface tension (aka negative pressure) that from the outside, it appears to have an effective negative mass and a negative gravitational field, while inside it still has positive gravity: sort of an inside-out gravitational dipole. Here's the paper about it:
"Negative mass bubbles in de Sitter space-time," Mbarek and Paranjape, Physical Review D, 2014
@Thomas R. Morrison
"Negative mass bubbles in de Sitter space-time," Mbarek and Paranjape, Physical Review D, 2014"
now i might be misremenbering stuff but din't daniel fry predict the dark energy effect years before it was discovered? that always made me scratch my head
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