Does this explain what generates gravity?

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#601
system7 said:
The Energy-Momentum tensor describes the masses or energies or photon momenta that are present, I suppose.
Click to expand...

That's correct. The very early universe was dominated by photons rather than by matter,

In general relativity, the energy-momentum tensor or stress-energy tensor (T) is of central importance.

The stress-energy tensor carries information about 'pressure' (flux of mass-energy?) and general relativity describes 'pressure' as a source of gravitational fields.

Negative pressure is tension, and this is the origin of the term “tensor".

The mathematics is way above my pay grade (T is a symmetric matrix!), but we could talk about the stress-energy tensor of a stack of oranges at the grocery store, the atoms in a chunk of copper, or the galaxies forming a galactic cluster.

More here about T, the matrix: https://phys.libretexts.org/Bookshelves/Relativity/Book:_Special_Relativity_(Crowell)/09:_Flux/9.02:_The_Stress-Energy_Tensor
 
#602
Small baby steps with Tensors for me, it is a new mathematical technique to me, but I think it might be a Quaternions thingie at heart. Which are good things, IMO.

But shall read your link, Galu, since I have time today. TX.

I shall read the Carroll book. It seems more accessable than Penrose (Nobody understands Penrose) and Susskind, though I am getting something out of Susskind, The Theoretical Minimum, which is heavier maths

I did Physics at College and a postgrad in Analog and Digital signal processing, which touches closely on Information Theory and Electromagnetism.

I don't consider myself specialised enough to come up with new improved theories, but enough for me to debunk this nonsense I think:

https://faculty.humanities.uci.edu/bjbecker/ExploringtheCosmos/lecture20.html

Do you really want the UCI History department in charge of Quasar research? No. Leave it to the PROFESSIONAL Astro-Physicists and Postgrads, preferably at Caltech or Stanford!

This is descending into Philosophy, in the modern sense, which is OK in its place, but really the nature of Gravity is a Scientific and Mathematical matter.

BTW, @tonyEE and @cumbb, have you watched the Sean Carroll talk with due attention? Or are you just hostile to proper Science in general?

My current bit of Scientific Observation, available in your neighbourhood after sunset, though 95% of people wouldn't know Venus from a hole in the ground:

Phases of Venus 2020.png


Venus is currently about half moon shaped through my X80 toy telescope. Most interesting. Should be able to see a crescent with X20 binoculars in a month or so. Kepler seems to have got it right.

Best Regards, Steve in Southsea, UK.
 
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#603
#605
@cumbb

What is your point about these videos you are posting? What have you concluded about "The Electric Universe" people? All is Electric Plasma?

Reeks of unscientific nonsense to me. But I suppose even cranks can make money on youtube by peddling garbage to an ill-informed populace...

I know a bit about Mars. Its rotational axis is not stable historically, which might explain certain asymmetries in surface features. But surely meteorite impact, volcanoes and maybe even water historically is a simpler explanation?

BTW have you watched the Sean Carroll video yet? I did ask you and @tonyEE. I am also intrigued to know your scientific qualifications and background.


Might be a better use of your time in the Gravity thread. We can then talk about stuff that matters.
 
#608
system7 said:
..... No. Leave it to the PROFESSIONAL Astro-Physicists and Postgrads, preferably at Caltech or Stanford!

This is descending into Philosophy, in the modern sense, which is OK in its place, but really the nature of Gravity is a Scientific and Mathematical matter.

BTW, @tonyEE and @cumbb, have you watched the Sean Carroll talk with due attention? Or are you just hostile to proper Science in general?
Click to expand...

I was gonna lurk, but since you brought my name up

(1) I know quite a bit about Caltech. Even had lunch there quite a few times. Worked for a "lab", up in La Cañada, owned by Caltech, a few times. It's cool to have some future Nobel Prize in Modern Physics serve you lunch. "Yeah, that Graviton Professor, he served our lunch cold... pfft ".

(2) Physics is Philosophy.... Natural Philosophy. If you don't do Philosophy, you are not doing Physics, you're doing Engineering.

(3) I did. I'm not hostile to Science, quite the opposite. And what is your definition of "proper Science" anyhow? That's a loaded term. Once again, have you read about the Philosophy of Science? Khun, Wittgenstein? I honestly think you ought to read it because it digs right to the core of it. I like to point out that change in Science is revolutionary as our models and interpretation of nature change. The change is often rejected, often rather vehemently, by people who've spent their entire life working within the outgoing paradigms.

(4) I'm actually open minded. One of my professors once told me: "Tony, if someone came up with a theory of gravity that said it was caused by little men from Mars, and that theory predicted stuff that we could measure, we'd have to accept it"... I agree with Dr. Brown.
 
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#609
;-)
Phila Sophia. Love to Wisdom; Love to Science;-)

Attitude.
Can not be studied.
Unfortunately, the study of the history of philosophy is labeled as philosophy.
Unfortunately, most "academics" seem to lack this attitude. The "science business" is always only a resource pot)-; Which is why instead of science, only keeping fellow human beings away from this pot is practiced;-)

system7 said:
Small baby steps with Tensors for me, it is a new mathematical technique to me, but I think it might be a Quaternions thingie at heart. Which are good things, IMO.

But shall read your link, Galu, since I have time today. TX.

I shall read the Carroll book. It seems more accessable than Penrose (Nobody understands Penrose) and Susskind, though I am getting something out of Susskind, The Theoretical Minimum, which is heavier maths

I did Physics at College and a postgrad in Analog and Digital signal processing, which touches closely on Information Theory and Electromagnetism.

I don't consider myself specialised enough to come up with new improved theories, but enough for me to debunk this nonsense I think:

https://faculty.humanities.uci.edu/bjbecker/ExploringtheCosmos/lecture20.html

Do you really want the UCI History department in charge of Quasar research? No. Leave it to the PROFESSIONAL Astro-Physicists and Postgrads, preferably at Caltech or Stanford!

This is descending into Philosophy, in the modern sense, which is OK in its place, but really the nature of Gravity is a Scientific and Mathematical matter.

BTW, @tonyEE and @cumbb, have you watched the Sean Carroll talk with due attention? Or are you just hostile to proper Science in general?

My current bit of Scientific Observation, available in your neighbourhood after sunset, though 95% of people wouldn't know Venus from a hole in the ground:

View attachment 1183706

Venus is currently about half moon shaped through my X80 toy telescope. Most interesting. Should be able to see a crescent with X20 binoculars in a month or so. Kepler seems to have got it right.

Best Regards, Steve in Southsea, UK.
Click to expand...
No argument;-)
system7 said:
@cumbb

What is your point about these videos you are posting? What have you concluded about "The Electric Universe" people? All is Electric Plasma?

Reeks of unscientific nonsense to me. But I suppose even cranks can make money on youtube by peddling garbage to an ill-informed populace...

I know a bit about Mars. Its rotational axis is not stable historically, which might explain certain asymmetries in surface features. But surely meteorite impact, volcanoes and maybe even water historically is a simpler explanation?

BTW have you watched the Sean Carroll video yet? I did ask you and @tonyEE. I am also intrigued to know your scientific qualifications and background.


Might be a better use of your time in the Gravity thread. We can then talk about stuff that matters.
Click to expand...
No argument;-)

No science;-)
Again and again;-)
 
#611
Re "Cosmic Lightning On the Moon", the nearest conventional physics that relates in any way is discussed here:

https://www.trebuchet-magazine.com/...ion of planetary surfaces in the solar system.

"Periodic storms of solar energetic particles may have significantly altered the properties of the soil in the moon’s coldest craters."
Click to expand...

1686932025201.png


Stuart Talbott (he of Cumbb's video) prefers to live in an "Electric Universe".

Here is the essential guide to the Electric Universe from Cumbb's "Thunderbolts University": https://www.thunderbolts.info/wp/2011/08/18/10609/
 
#612
Lightning on the Moon fits the description of a "Transient Lunar Phenomenon", a term created by the late Patrick Moore of "The Sky at Night" fame.

1686933659713.png


During the Apollo 17 mission in December 1972, Lunar Module Pilot Harrison Schmitt observed a bright flash-like phenomenon north of crater Grimaldi while in orbit around the Moon.

It is possible that the triboelectric charging of particles within a gas-borne dust cloud could have given rise to an electrostatic discharge.
 
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#613
This is going to be Brutal for the Philsophers.


See the Physicists like Dick Feynman and Lenny Susskind are Scientificing whilst you Philosophers are doing whatever you do:

Kuhn said:

  1. Accurate – empirically adequate with experimentation and observation
  2. Consistent – internally consistent, but also externally consistent with other theories
  3. Broad Scope – a theory's consequences should extend beyond that which it was initially designed to explain
  4. Simple – the simplest explanation, principally similar to Occam's razor
  5. Fruitful – a theory should disclose new phenomena or new relationships among phenomena
Surely a Child of Ten can see that?

And as for Wittgenstein? Surely a failed Engineer?

https://en.wikipedia.org/wiki/Ludwig_Wittgenstein

He and Popper and Russell just ended up arguing. No conclusion whatsoever.

No, I stick to the Science!

Betelgeuse Red Giant Dimming.jpg


I must admit, I worry about erratic Betelgeuse. Top left corner. Could go Supernova tomorrow! 🙂
 
#614
Can't it wait till Monday? 😀

Betelgeuse, has been getting increasingly bright, hitting 142 percent of its usual luminosity at the end of May, leading scientists to suggest it might be fixing to go supernova.

Look out for a huge bright patch in the sky during both the day and night, around the same brightness as the full moon at its peak.

https://www.msn.com/en-us/news/tech...ill-be-visible-with-the-naked-eye/ar-AA1cDXjI
 
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#619
MSN site locked my op system up as it always does.
It is 2200 in GMT5 western edge of EDT. There is a big bright thing due west, where the sun goes down. (my stupid coleman compass says that is 20 deg e of north). Was visible at 2100 too, not even dark. Is that a planet or Beteguese? I have 7x35 binoculars, can't see a disk. It is not red. My Peterson field guide to stars & planets shows no Orion on June 15 Northern Horizon. On October page there is orion on south horizon to the left (east?). If west object not Orion which way compass heading? Thanks
 
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#620
That's likely to be Venus which has been bright in the western sky for some time now.

It's brighter than all sky objects apart fom the Sun and the Moon.

At the moment it will be moving from "half-moon" into its crescent phase, so maybe that's why you don't see a disk.
 
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