Gravity - is it really there?

[SelfSim]

What is dark matter Kylie


It’s a mystery!

Isn't that just wonderful?
.. A mystery!

 

[JohnEmmett]

What is dark matter?

Dark matter is the mysterious stuff that fills the universe but no one has ever seen.

space.com

 

[JohnEmmett]

Isn't that just wonderful?
A mystery!

…

 

[JohnEmmett]

real science

The spirit of science is inquiry

 

[Kylie]

What is dark matter Kylie


It’s a mystery!

You only consider it a mystery because you don't understand cosmology. If you'd done even the slightest bit of looking, you would have found a wealth of sources that tell you what dark matter is and the evidence for it. https://www.pnas.org/doi/10.1073/pn...tence,in the universe, gravitational lensing,

 

[JohnEmmett]

If you'd done even the slightest bit of looking

From your link…

However, what is the dark matter? This is one of the most fundamental open questions in cosmology and particle physics.​

 

[Mark Quayle]

Okay. Here's a video that explains it very well. It's got animations and everything.

Very interesting. Thank you. But the "Huh?'s" continue. Being ignorant of the math, I don't find his 'explanation' yet, intuitive. Nor, I'm sorry, do I find it explanatory. It seems rather circular (and I meant no pun there) to say that the distortion of Space-Time causes the gravity, just as it would sound circular to say that gravity causes the distortion to Space-Time. If Gravity IS the distortion of Space-Time, then all they have said is that Gravity is Gravity, and this is how it acts, or this is what it does.

To me, anyway, he has not explained gravity, but merely described how it acts —more intricately and detailed than Newton, no doubt— but not explained what it is, nor even how it 'exists'. Perhaps Quantum relationships can 'bring it closer' to us, idk. (Now that pun, I intended, once I started to put the words down, lol.)

 

[essentialsaltes]

It seems rather circular (and I meant no pun there) to say that the distortion of Space-Time causes the gravity, just as it would sound circular to say that gravity causes the distortion to Space-Time.

It's only circular if you say both of those things simultaneously. But that's not the case here. Mass and Energy cause the distortion to space-time. And consequences of the curvature of spacetime is what we experience as the 'force' of gravity.

 

[JohnEmmett]

"A gravitational field cannot be in two places at once," said Sabine Hossenfelder, a theoretical physicist …

According to Einstein, space-time is warped by matter and energy, but quantum physics says matter and energy exist in multiple states simultaneously — they can be both here and over there.

"So where is the gravitational field?" asks Hossenfelder. "Nobody has an answer to that question. It's kind of embarrassing," she said.


The case against space-time theory

 

[Mark Quayle]

It's only circular if you say both of those things simultaneously. But that's not the case here. Mass and Energy cause the distortion to space-time. And consequences of the curvature of spacetime is what we experience as the 'force' of gravity.

I suppose you have a point, since they didn't get into a full discussion of what that distortion entails or implies —such as the potential energy of the distance per the attraction of bodies in motion through that field of space-time. Yet to my ignorant mind, it still sounds circular.

Is not the very 'existence' of the fabric of space-time, to include the distortions, not 'caused' by the existence of masses and energies? According to general relativity, there was neither time nor space before the BB, no? Other than the singularity, there was no emptiness nor somethingness. No distance. According to some, no reality.

 

[essentialsaltes]

Is not the very 'existence' of the fabric of space-time, to include the distortions, not 'caused' by the existence of masses and energies?

No, I really don't think so.

According to general relativity, there was neither time nor space before the BB, no?

The singularity is where GR breaks down and no longer works. We don't know what the laws are that govern that situation, so GR has nothing to say about the actual singularity or what may or may not have come before. Our understanding of cosmology only begins a short time after the BB.

 

[JohnEmmett]

Our understanding of cosmology only begins a short time after the BB.

“Try and use general relativity and quantum theory together, and it doesn't work.”

-Colin Stuart

 

[Kylie]

From your link…

However, what is the dark matter? This is one of the most fundamental open questions in cosmology and particle physics.​

No one is saying we have all the answers. But it's a far cry from the complete unknown you were making it out to be.

 

[JohnEmmett]

No one is saying we have all the answers. But

Yes the truth is in the middle.

 

[Kylie]

Very interesting. Thank you. But the "Huh?'s" continue. Being ignorant of the math, I don't find his 'explanation' yet, intuitive. Nor, I'm sorry, do I find it explanatory. It seems rather circular (and I meant no pun there) to say that the distortion of Space-Time causes the gravity, just as it would sound circular to say that gravity causes the distortion to Space-Time. If Gravity IS the distortion of Space-Time, then all they have said is that Gravity is Gravity, and this is how it acts, or this is what it does.

To me, anyway, he has not explained gravity, but merely described how it acts —more intricately and detailed than Newton, no doubt— but not explained what it is, nor even how it 'exists'. Perhaps Quantum relationships can 'bring it closer' to us, idk. (Now that pun, I intended, once I started to put the words down, lol.)

I agree, if it said that gravity distorts spacetime, and this distortion creates gravity, that would be circular logic.

But it's not saying that. It's saying MASS distorts spacetime, and this distortion created by mass is what creates gravity.

 

[Kylie]

According to general relativity, there was neither time nor space before the BB, no? Other than the singularity, there was no emptiness nor somethingness. No distance. According to some, no reality.

There are two things incorrect here.

First of all, no one is saying that there was nothing before the Big Bang. The simple fact is we don't know. It's quite possible that our universe existed before that (in whatever sense the word "before" can be said to apply here), but the Big Bang was some kind of rest switch. This of it like a bronze statue. You can examine it and get an incredibly detailed history of it by looking at the wear patterns, analyzing any gas trapped in microscopic bubbles in the metal, etc., but you can only go back to the moment the metal was poured. That metal might have been sitting around as ingots for a hundred years before that point, but you can never learn anything about that, because the act of melting the bronze and pouring it destroyed any evidence of that time.

Secondly, general relativity doesn't apply to cases where the distortion is as great as it was during the Big Bang. So it's incorrect to say that GR makes any predictions about what was before the BB.

 

[Neogaia777]

Gravity is the attraction of everything that has mass.

Except dark matter maybe, etc...?

That could or might be having the opposite effect maybe, etc...?

God Bless!

 

[Kylie]

Gravity is the attraction of everything that has mass.

Except dark matter maybe, etc...?

That could or might be having the opposite effect maybe, etc...?

God Bless!

Dark matter most definitely has a gravitational effect.

 

[Neogaia777]

Dark matter most definitely has a gravitational effect.

Is it in the opposite? Or does it pull or attract just like everything else?

 

[JohnEmmett]

Is it in the opposite? Or does it pull or attract just like everything else?

There is gravity.