Does this explain what generates gravity?

[Galu]

@TNT

Like spacetime, your mattress becomes warped by the mass of your body, making it difficult to climb out of the resulting gravity well.

Don't blame ageing, blame Einstein! 😀

 

[Fast Eddie D]

Maybe if designers applied relativistic physics to mattress design instead of Newtonian mechanics, they could come up with the ultimate support mattress! It would be like sleeping on a cloud.

And while we're talking about mattresses, it's time to flip them before they become black holes.

 

[Galu]

I'm working on the Tachyon Mattress™.

The anti-mass tachyon particle should have the opposite gravitational effect to particles of normal mass.

With a Tachyon Mattress™, you would simply float out of bed in the morning! 😉

 

[Fast Eddie D]

I could sure use that, and a time machine too since we're screwing with relativity.

 

[Galu]

Well, time does seem to go fast when we are sleeping!

 

[benb]

Things to know about String Theory....

1) 95% of (funded) tenures (aka Professorships in Physics) at American Universities are teaching posts on String Theory. No, I don't know why either...

2) People with alternative interesting ideas like the Loop Quantum Gravitists or Gravistar folks feel they are underfunded...

...

5) Why would you build a Multiverse of 10^47 Universes just to create our one? It is far too complicated, aka Occam's Razor.

With the appearance of "funded" I have to think there's got to be some economic observation akin to Occam's Razor that could apply.

"What theory/hypothesis provides the most employment and research funding for the people that are widely regarded as the experts in the field?"

"What about alternative hypotheses?" "Oh, well, let's ask the experts ..."

6) I say this as someone who has read Brian Greene's "elegant Universe", which is the seminal popular book on String Theory:

I recall reading that too, and I've also seen his three-hour NOVA series with all the sci-fi special effects. It reminds me of that "What The Bleep Do We Know?" movie where the scientists were taken out of context to make it look like they agreed with the woo stuff.

 

[indianajo]

I watched the Nova string theory series. I don't recall any proposed tests of the theory. No predictions, no way to prove validity. Hot air until they propose a test that previous models would fail.
Whereas I was shocked that Einstein's Faster Than Light simultanety prediction about partical parameters (photons) passed a test at two observatories in Spain. Another Nova program. I don't understand why photons received at two different locations from the same star at the same time should be interlocked, but the journal reviewers seem satisfied. Aren't they different photons since they took different paths?

 

[Galu]

Einstein's Faster Than Light simultanety prediction...passed a test...

Can you supply a link to the mentioned journal? I'm not sure what to search for.

 

[Galu]

I did find "A Conversation with Brian Greene": https://www.pbs.org/wgbh/nova/elegant/greene.html

"For string theory to have the kind of acceptance of general relativity, it's got to do the same thing. It's got to make a prediction that is borne out by some experiment. And as yet, we haven't quite gotten to the stage where we can make definitive predictions which, if they're found, the theory was right, and if they're not found, the theory was wrong."

 

[indianajo]

Can you supply a link to the mentioned journal? I'm not sure what to search for.

I don't read physics journals, they are expensive & above my head. But the Nobel Prize committee does, I hope. https://en.wikipedia.org/wiki/Anton_Zeilinger who is a nobel prize winner for work in quantum entanglement.

 

[Galu]

Another Nova program.

Thanks for your edit. Can you identify the episode in question from the link below?

https://www.pbs.org/wgbh/nova/series/the-fabric-of-the-cosmos/

 

[Galu]

Now that I know we are talking about quantum entanglement, I've found this from 2017:

https://www.space.com/35676-einstein-spooky-action-starlight-quantum-entanglement.html

 

[system7]

An interesting half-hour BBC UK Radio 4 show about Quantum Gravity and Black Holes:

https://www.bbc.co.uk/sounds/play/m001hp2p

Jim Al-Khalili talks to Professor Clifford Johnson about Physics and Life.

You need to log in with an account, which is an email and password. But no TV licence required.

I don't know if it works worldwide. But I was fascinated. Clifford Johnson is a very top guy in Quantum Gravity.

Best Regards from Steve in Portsmouth UK.

 

[system7]

I am not sure whether all this String Theory Gravity Stuff exactly floats my Personal Physics boat... but interesting.

Like Richard Feynman, am keen to do experiments. You know, test it! This is what Science is all about.

I was out and about last night with my toy telescope. Keen to observe "The Green Comet". Somewhere near Alpha Ursa Minoris, aka Polaris.

https://www.bbc.co.uk/news/science-environment-64388483

Unfortunately, the UK skies were the usual cloudy mess. I had to rely on simulation to have any idea what is going on.

Have got a couple of books about Classical Mechanics and Gravity out from Portsmouth Central Library.

Specifically French's book about Classical Mechanics, and Feynman's Lectures on Gravitation.

(Due to a Computer Software glitch, no image as yet. But I am sure I can fix that later.)

So far, so Good. Even discovered a Lost Feynman Lecture! It's about multidimensional Phase Space.

Such Geometric Symmetry. I love this stuff!

 

[system7]

File conflict fixed! This is what Engineers do.

10 lectures on Classical Mechanics. 16 on Feynman Gravity Mechanics. About a Month's reading for serious Physicists. One Lecture a Day. I can do this! 😛

 

[Galu]

The BBC link says that even using binoculars the "green comet" will appear only as a "faint white blur".

Apparently a digital camera will be able to pick up the green colour.

Equipped with your starter telescope, trusty digital camera and a roll of gaffer tape, Steve, you could potentially supply us with some interesting amateur images! 😎

 

[Bigun]

I think it's all about energy. Einstein showed us that gravity is a consequence of curved space time and this curvature is created by energy density (from E = mcc in which m is an emergent property). Gravity is detectable only because it acts on such energy density (from F = ma) so it's really just an expression of the interaction / transfer of energy between energy-densities (aka particles etc.).

 

[Galu]

10 lectures on Classical Mechanics.

You just can't beat reading about good old classical mechanics before it, along with classical electromagnetism, became imbedded in relativistic quantum mechanics or quantum field theory.

Even discovered a Lost Feynman Lecture! It's about multidimensional Phase Space.

I read that classical mechanics includes the concept of phase space which mathematicians use in the study of differential geometry and differential topology - topics right up you street, Steve! https://en.wikipedia.org/wiki/Phase_space

 

[Bigun]

that looks like a brown paper groceries bag to me

 

[Galu]

Gravity is ... really just an expression of the interaction / transfer of energy between energy-densities (aka particles etc.).

I see some questioning on the intertwit of whether there is an energy density associated with a gravitational field.

Here's something from NASA: https://www.grc.nasa.gov/WWW/K-12/Numbers/Math/Mathematical_Thinking/possible_scalar_terms.htm

"Energy density is a measure of the energy stored in the field per unit volume of space. While eq. 3 represents the energy density for the electric field, and a similar expression represents the energy density for the magnetic field, no such energy density term has ever been defined for the gravitational field. But one suspects that it could be, and possibly even should be."

I'd like to find out more about the present state of play, but it's bound to rely on mathematics that is impenetrable to me!