What is the currently accepted answer to the question, "what is gravity"?
That which maketh the apple bonk the skull most uninvitedly.
Military Has Been Researching "Anti-Gravity" For Nearly 70 Years
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Re: Military Has Been Researching "Anti-Gravity" For Nearly 70 Years
#42What is the currently accepted answer to the question, "what is gravity"?
Gravity is one of the essential forces in nature. If you want to explain it in simpler terms it is not possible because gravity is the simpler thing. You can use gravity to explain other things, but you cannot use other things to explain gravity.
Re: Military Has Been Researching "Anti-Gravity" For Nearly 70 Years
#43What is the currently accepted answer to the question, "what is gravity"?
Einstein believed gravity isn't really a force in the same sense as the other three fundamental forces, but a property of space-time. That seems to be a problem because it causes some kind of "incompatibilty" with the others. Trying to reconcile those, efforts has been made to create quantum gravity theories, that view space itself as quantized and in this direction you find strings and quantum loop gravity.
Disclaimer: I'm no expert, just parroting what I found in Wikipedia.
Re: Military Has Been Researching "Anti-Gravity" For Nearly 70 Years
#44Physicists have been searching for variations in the coupling of materials to gravity for more than a century, and by some measure, for more than a millenium. https://en.wikipedia.org/wiki/Equivalence_principle#Tests_of... Every experiment anyone has ever tried has come up empty. The equivalence principle is a postulate (Einstein's "happiest idea") that underlies General Relativity, making it essential to test. (Sour…
Assuming we find dark matter, do you think it will represent some departure from our current understanding of gravity and how it relates to mass? Or do you think it will just be some boring dust clouds?
Re: Military Has Been Researching "Anti-Gravity" For Nearly 70 Years
#45Earlier quoted context omitted.
> Physics, as currently understood from available experimental evidence, 100% allows time travel to the past, paradoxes included. General Relativity, which is where the term "closed timelike curve" is used, does not allow paradoxes. A spacetime with closed timelike curves in it (for example, the Godel universe) still has only one thing happening at each event. The real problem conceptually with such solutions is that…
Luckily "free will" as would fit a layman's interpretation of the term is already incompatible with physics, so the existence of CTCs doesn't pose additional problems.
I think most people would interpret free will to mean something that is perfectly compatible with any definition of determinism.
If I decide to raise my right hand, I raise it. Don't get pedantic in regards to disabled people. It doesn't matter if the universe is completely deterministic, that doesn't mean that I'm not the entity that decided to raise my right hand. The deterministic universe may have produced me, but the software I'm running is me. The reason I raised my hand is because of me. Sure there are an infinite number of factors that have fed into the circumstances of my birth, and everything that's happened to me, but everything that I do is specifically as a consequence of my free will. I am the software, deterministic or not.
Re: Military Has Been Researching "Anti-Gravity" For Nearly 70 Years
#46Physicists have been searching for variations in the coupling of materials to gravity for more than a century, and by some measure, for more than a millenium. https://en.wikipedia.org/wiki/Equivalence_principle#Tests_of... Every experiment anyone has ever tried has come up empty. The equivalence principle is a postulate (Einstein's "happiest idea") that underlies General Relativity, making it essential to test. (Sour…
How much money does society need to spend supporting the work you do before we can safely conclude that Einstein was actually correct and we don't need to test it any more?
Re: Military Has Been Researching "Anti-Gravity" For Nearly 70 Years
#47Physicists have been searching for variations in the coupling of materials to gravity for more than a century, and by some measure, for more than a millenium. https://en.wikipedia.org/wiki/Equivalence_principle#Tests_of... Every experiment anyone has ever tried has come up empty. The equivalence principle is a postulate (Einstein's "happiest idea") that underlies General Relativity, making it essential to test. (Sour…
Assuming we find dark matter, do you think it will represent some departure from our current understanding of gravity and how it relates to mass? Or do you think it will just be some boring dust clouds?
We have already tested the equivalence principle toward dark matter [1]. It appears to fall like everything else, at the 1% or better level.
It is extremely difficult for modifications of gravity to simultaneously fit the cosmic microwave background, big-bang nucleosynthesis, galactic rotation curves, and the Bullet Cluster. The safe bet these days is on some sort of non-baryonic dark particle (which is why so many people are looking for them). Most other loopholes are closed or in the process of being closed.
The coming decade or two should have something significant to say about dark matter. We will either discover its nature or severely constrain its properties through a plethora of varied experiments and searches.
Re: Military Has Been Researching "Anti-Gravity" For Nearly 70 Years
#48Physicists have been searching for variations in the coupling of materials to gravity for more than a century, and by some measure, for more than a millenium. https://en.wikipedia.org/wiki/Equivalence_principle#Tests_of... Every experiment anyone has ever tried has come up empty. The equivalence principle is a postulate (Einstein's "happiest idea") that underlies General Relativity, making it essential to test. (Sour…
How much money does society need to spend supporting the work you do before we can safely conclude that Einstein was actually correct and we don't need to test it any more?
Assuming Einstein is correct is not the end, because we still have so many questions. For instance, why is Einstein correct?
Re: Military Has Been Researching "Anti-Gravity" For Nearly 70 Years
#49To really be able to manipulate gravity, you would also need to manipulate mass, and so far nuclear is the only way I know of, in which we do that, but uhh.. I don't think we'll get anti gravity until we can control mini stars... Little nuclear engines.
It is a common myth that nuclear reactions "turn mass into energy". What actually happens is that the products of the reaction have less binding energy than the initial nucleus. Since energy gravitates, this reduces the mass of the products. The exact same thing happens in chemical reactions. If you burn something, the product are lighter than the initial substances by the mass equivalent of the energy released.