Other than it is a property of matter and there is no particular reason to suppose it doesn''t relate in some ways to the "known" forces.
I think the current view is that Gravity is a non-linear force, which makes it difficult to formulate. It relates more to total energy than mass.
Gravity Waves create Gravity, for instance, and change spacetime and any contained particles into different quantum states when passing through it.
Everbody thinks the Graviton must be Spin 2. But Feynman, for instance, was unable to create a model for it along the lines of QED with charged particles.
The Maths is difficult with General Relativity for sure. I still don't know what a Tensor is! Or how to multiply them. 🙂
Gravity Waves create Gravity, for instance, and change spacetime and any contained particles into different quantum states when passing through it.
Everbody thinks the Graviton must be Spin 2. But Feynman, for instance, was unable to create a model for it along the lines of QED with charged particles.
The Maths is difficult with General Relativity for sure. I still don't know what a Tensor is! Or how to multiply them. 🙂
Gravity creates gravity waves may be a better description.
To be more exact, gravitational waves are generated in spacetime by accelerating masses.
It has been predicted that the passage of a gravitational wave should permanently distort spacetime, producing a so-called "memory effect".
This is exactly what I've been banging on about Galu.
If distance is simply the time between objects using our cosmic ruler, why do we have space time?
(I posted this up before, but it is a fascinating slide deck on Einstein's journey to relativity in which some of the things we have been discussing are covered https://hifisonix.com/wp-content/uploads/2022/06/Einsteins-path-to-Relativity.pdf. According to Jurgen Rnn, the author, writing elsewhere, there was quite some debate over which had primacy, matter or space - they did not use spacetime in their discussion - and they concluded space took primacy. Make of it what you will!)
Is the Higgs field only active within a gravitational field? Serious question BTW because what does it do out in deep space where there is no gravitational field? Does it activate if you were to accelerate a body out there?
The famous equation states mass relates to energy. Suggests energy can create mass if the equation can be reversed.
Gravity waves show as disturbances in our local gravity field. Gravitational force appears to reduce with distance and ?? never reaches zero. So some gravity event of some kind somewhere shows an effect here.
There is a bit of a catalogue of them on the wiki. Distances > 5gpc made me wonder if that is greater than the age of the universe? I thought they had tied it down to light speed?
https://en.wikipedia.org/wiki/List_of_gravitational_wave_observations
Gravity waves show as disturbances in our local gravity field. Gravitational force appears to reduce with distance and ?? never reaches zero. So some gravity event of some kind somewhere shows an effect here.
There is a bit of a catalogue of them on the wiki. Distances > 5gpc made me wonder if that is greater than the age of the universe? I thought they had tied it down to light speed?
https://en.wikipedia.org/wiki/List_of_gravitational_wave_observations
If the graviton were actually to exist, it would be unique since it would be the only "tensor boson" and would have a spin value of 2 because the tensor field has particles with a spin value of 2.
Enter our friend Dirac again, as the term "tensor boson" arises because of the inclusion of bosons in the tensor formulation of the Dirac theory - the quantum theory of the electron.
Links to the tensor form of Dirac's theory produce multi-page PDFs that don't make it look so easy!
Your "space time" should read "spacetime" where space and time are not separate.
Special relativity doesn't talk about distance, but about a combination of distance and time called the "spacetime interval".
The spacetime interval is a combination of distance and time that is invariant, i.e., a quantity that can be agreed upon by all observers.
I read that the Higgs field is non-zero everywhere, all the time, independently of whether anything else is present in the Universe.
There are still many questions surrounding the Higgs field, e.g., could it play some role in generating the dark-matter mass as well?
I've been looking at the concept of the "spacetime interval" as it's bitterly cold outside and I've nothing better to do!
In spacetime, an object will travel from one "spacetime event" to another. These two spacetime events are separated by a "spacetime interval".
Spacetime events can be represented on a "spacetime diagram", such as in the simple one below where the spacetime events are represented by yellow stars.
Here, the object is moving at steady speed in the +x direction.
The spacetime interval is related to the "length" of a straight line drawn between these spacetime events in the diagram.
Mathematical analysis shows:
(For (Δx)^2, you may substitute (Δx + Δy + Δz)^2 for the full spacetime experience!)
I believe the spacetime interval squared remains invariant under Lorentz transformations, but truthfully the full analysis bamboozles me! 🤓
https://phys.libretexts.org/Courses/University_of_California_Davis/UCD:_Physics_9HB__Special_Relativity_and_Thermal_Statistical_Physics/2:_Kinematics_and_Dynamics/2.1:_Spacetime_Diagrams
In spacetime, an object will travel from one "spacetime event" to another. These two spacetime events are separated by a "spacetime interval".
Spacetime events can be represented on a "spacetime diagram", such as in the simple one below where the spacetime events are represented by yellow stars.
Here, the object is moving at steady speed in the +x direction.
The spacetime interval is related to the "length" of a straight line drawn between these spacetime events in the diagram.
Mathematical analysis shows:
(For (Δx)^2, you may substitute (Δx + Δy + Δz)^2 for the full spacetime experience!)
I believe the spacetime interval squared remains invariant under Lorentz transformations, but truthfully the full analysis bamboozles me! 🤓
https://phys.libretexts.org/Courses/University_of_California_Davis/UCD:_Physics_9HB__Special_Relativity_and_Thermal_Statistical_Physics/2:_Kinematics_and_Dynamics/2.1:_Spacetime_Diagrams
Gravity related. There are various comments about how things were expansion wise in the past so picked one
When the universe was half its present size, nuclear reactions in stars had produced most of the heavy elements from which terrestrial planets were made. Our solar system is relatively young: it formed five billion years ago, when the universe was two thirds its present size.
https://www.scientificamerican.com/article/the-evolution-of-the-universe/
Does this mean that orbits or gravity have changed during this period and the expansion has had no effect at all?
CBM would also be at a different f than it is now.
An odd ball video popped up. Rubbished by Ask Ethan but dark energy and black hole related. Rather long video
When the universe was half its present size, nuclear reactions in stars had produced most of the heavy elements from which terrestrial planets were made. Our solar system is relatively young: it formed five billion years ago, when the universe was two thirds its present size.
https://www.scientificamerican.com/article/the-evolution-of-the-universe/
Does this mean that orbits or gravity have changed during this period and the expansion has had no effect at all?
CBM would also be at a different f than it is now.
An odd ball video popped up. Rubbished by Ask Ethan but dark energy and black hole related. Rather long video
You will know that expansion does not occur where there are forces such as gravity that can overcome it.
What if an object doesn’t travel at all, just sits there as time goes by, like the model Time Machine in The Time Machine? Space x, y, z remains the same but time moves forward. The model Time Machine disappears because it is ahead of those in the room time wise, as it were.
The video probably relates to this article: https://iopscience.iop.org/article/10.3847/2041-8213/acb704
The idea that black holes are the source of dark energy follows from this hypothesis:
Squeezing as much matter as possible into a black hole without breaking Einstein’s equations produces vacuum energy and avoids the need for a singularity. With singularities absent, the combined vacuum energy of black holes produced in the deaths of the universe’s first stars agrees with the quantity of dark energy we currently measure in our universe.
This hypothesis has been interpreted as suggesting there is no need to add anything new to the universe as a source for dark energy - black holes are the dark energy!
Bunkum or serious astrophysics? I would listen to Ethan on this: "It’s an interesting idea and one that I can’t say is definitely wrong. But despite the asserted "0.02% chance of it being a fluke," I’d definitely bet against this as not only being the explanation for dark energy, but that any sort of significant cosmological coupling exists at all."
https://bigthink.com/starts-with-a-bang/black-holes-dark-energy/ (Warning, long and involved article!).
I don't think we need to discuss "The Time Machine" any further. My Artist friend Martin was telling me tonight that Einstein's first Paper was completely WRONG! It Brownian motion wasn't it? Or is he thinking of the Cosmological constant?
He also told me a satellite has returned to Earth with the finding that some stars predate the Big Bang. The man also told me my knowledge of Physics is outdated and gleaned from the old-fashioned BBC.🙄
I amazed him with my knowledge of the ancient 5 Platonic solids, since he finds Pyramids interesting. The Great Pyramid is half an Octogon. He was unaware of the 24-cell in 4 Dimensions.
I am enjoying my current Physics book by John Charap. You can just read the chapters that interest you and it is good on Cosmology:
The 4x4 matrix or tensor that describes Spacetime has a diagonal of -1,1,1,1. What this means is the first time term is a negative Scalar and the Spacelike squared terms are Vectors.
It is interesting that any whole or discrete number can be expressed as the sum of 4 squares (Legendre). This might be your quantum with a little play on signs. But nobody honestly knows, as I admitted.
So a good day. I also arranged a date with a Pompey lovely....win, win. 🙂
He also told me a satellite has returned to Earth with the finding that some stars predate the Big Bang. The man also told me my knowledge of Physics is outdated and gleaned from the old-fashioned BBC.🙄
I amazed him with my knowledge of the ancient 5 Platonic solids, since he finds Pyramids interesting. The Great Pyramid is half an Octogon. He was unaware of the 24-cell in 4 Dimensions.
I am enjoying my current Physics book by John Charap. You can just read the chapters that interest you and it is good on Cosmology:
The 4x4 matrix or tensor that describes Spacetime has a diagonal of -1,1,1,1. What this means is the first time term is a negative Scalar and the Spacelike squared terms are Vectors.
It is interesting that any whole or discrete number can be expressed as the sum of 4 squares (Legendre). This might be your quantum with a little play on signs. But nobody honestly knows, as I admitted.
So a good day. I also arranged a date with a Pompey lovely....win, win. 🙂
See the spacetime diagram on the left, which is reproduced from my earlier link.
In this diagram and the others, the spacetime events have been joined together to form a "world line" - a "spacetime trajectory" which shows the passage of the object through spacetime.
Close examination reveals that the slope of the world line equals c/u where c is the speed of light and u is the speed of the object as measured by the observer.
The inverse of the slope of the world line is u/c, i.e., the fraction of the speed of light that the observer measures for that object - with the sign representing the direction of motion.
For light the slope is ±1 leading to the concept of the "light cone". Objects can only follow world lines within the light cone because they cannot travel at or beyond the speed of light.
On the above diagram, "elsewhere" represents an undefined, inaccessible region because one would have to travel faster than light to reach it.
In other words, all of physical reality is contained inside the light cone.
There, I feel much better having got that off my chest! 🤓
The video gets into how they formulated the idea fairly early on. Nothing but standard astroohysics techniques but used on selected galaxies,
I really don't know what is wrong with many people, who mostly shuffle down the street gazing down at their mobile phones. I was out and about tonight making practical upward observations of the Universe with my eyes and to confirm, on inferior Canon camera equipment...
Excellent. A Moon-Jupiter conjunction visible in even Portsmouth's wretchedly light-polluted skies! A modest telescope revealed to Galileo 4 Jovian moons. Clearly the Moon's orbit is inclined to that of Jupiter. Otherwise we might have had an eclipse. You heard it here first.
As a Mathematician of the Ilk of Kepler, I calculate the Moon moves its own width in an hour, because it looked different 3 hours ago. All driven by Gravity. 😀
Excellent. A Moon-Jupiter conjunction visible in even Portsmouth's wretchedly light-polluted skies! A modest telescope revealed to Galileo 4 Jovian moons. Clearly the Moon's orbit is inclined to that of Jupiter. Otherwise we might have had an eclipse. You heard it here first.
As a Mathematician of the Ilk of Kepler, I calculate the Moon moves its own width in an hour, because it looked different 3 hours ago. All driven by Gravity. 😀
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I've been keeping an eye on Jupiter and its closeness to the Moon in the sky.
I read there's four conjunctions we can look forward to seeing - tonight's (Jan 18) then February 14, March 13, and April 10.
https://www.timeanddate.com/news/astronomy/moon-jupiter-conjunction-2024
It is my opinion that Black Holes & Dark Energy ARE RELATED.
A BH tears apert 'Type A' and 'Type B' Pure Energy (all that enters).
One type is absorbed & sent to its singular/universal destination,
and the other type is 'spewed out' as Hawking Radiation > OR >
https://www.skyatnightmagazine.com/space-science/accretion-disk
Here is something 'newish' & interesting >
A BH tears apert 'Type A' and 'Type B' Pure Energy (all that enters).
One type is absorbed & sent to its singular/universal destination,
and the other type is 'spewed out' as Hawking Radiation > OR >
https://www.skyatnightmagazine.com/space-science/accretion-disk
Here is something 'newish' & interesting >