Science News Thread (for articles that don't relate to ongoing discussions)

[darthgently]

I’m calling BINGO on this guess of mine

 

[Terwin]

Kind of makes you wonder if 'dark energy' is just the consequence of a plank-length type limitation on gravitational waves, limiting the effect of gravity at longer ranges much like the plank length prevents the 'ultraviolet catastrophe' with very short EM waves.

Then that might suggest that 'dark matter' is a consequence of something akin to emission spectra, but with a spectra specific to our galaxy/universal constants/etc.

Then again, that may not provide any testable predictions, making it a rather useless interpretation.

 

[Mr. Kerbin]

2 hours ago, Terwin said:

Kind of makes you wonder if 'dark energy' is just the consequence of a plank-length type limitation on gravitational waves, limiting the effect of gravity at longer ranges much like the plank length prevents the 'ultraviolet catastrophe' with very short EM waves.

Then that might suggest that 'dark matter' is a consequence of something akin to emission spectra, but with a spectra specific to our galaxy/universal constants/etc.

Then again, that may not provide any testable predictions, making it a rather useless interpretation.

 

Here’s a fun idea.

What if the big rip AND the Big Crunch happened at the same time? ‘dark energy’, rips off the outer layer of the universe, and the crunch collapses the other mass? Slowly, at some point, there is less and less mass to crunch, and then it ends.

[darthgently]

22 minutes ago, Terwin said:

Kind of makes you wonder if 'dark energy' is just the consequence of a plank-length type limitation on gravitational waves, limiting the effect of gravity at longer ranges much like the plank length prevents the 'ultraviolet catastrophe' with very short EM waves.

Then that might suggest that 'dark matter' is a consequence of something akin to emission spectra, but with a spectra specific to our galaxy/universal constants/etc.

Then again, that may not provide any testable predictions, making it a rather useless interpretation.

 

All I know is that the more information I gather about dark energy and dark matter the more it smells like epicycles — they loosely “fit” the data as placeholders but are not answering any thing real.  It  seems to point to an incorrect assumption or blind spot in our underlying understanding rather than an undiscovered particle or other

[AckSed]

Parker Solar Probe about to kiss the sun full on the corona for the first time: https://arstechnica.com/space/2024/12/were-about-to-fly-a-spacecraft-into-the-sun-for-the-first-time/

[boriz]

Is there a minimum 'quanta' of gravity? The inverse square law means gravity falls off quickly with distance, but does it ever reach zero?

[darthgently]

6 hours ago, boriz said:

Is there a minimum 'quanta' of gravity? The inverse square law means gravity falls off quickly with distance, but does it ever reach zero?

Quick search result: No direct measurements of quantized gravity or space time as is too small and fast for us to do so at this time.  But indirectly it seems to be clicking with many theoreticians.

Inverse square would still apply and asymptotes to zero (never reaches, gets closer) but I’d guess that at distances less than Planck this would change up quite a bit.  Like maybe being impossible to distinguish from the strong nuclear force or similar (dramatic music)

As for gravity going to zero for quantum reasons at the extreme that doesn’t seem intuitive to me but darn good question and would make sense.  How would one test that?  It is such a weak force to begin with

Edited December 24, 2024 by darthgently

[darthgently]

Just a reminder that the Parker Solar Probe will zip through the fires of the Sun in the wee hours tonight faster than any previous human object.  With electrical wires made of niobium sheathed in sapphire to keep them from melting.  Rudolph has to share the glory this year.

 

[boriz]

Thank you Darthgently . Another question if I may:

Is mass conserved when converted to energy? I.E. As a star loses mass, does the radiant energy (traveling at the speed of light) carry away that mass with the total conserved, but spread over a much greater volume? Or, when the anti-matter annihilated in the very early universe, did the universe have the same total mass before and after annihilation?

[farmerben]

Mass is not conserved.  Mass can be treated as a form of potential energy, energy is conserved.

https://en.wikipedia.org/wiki/Mass–energy_equivalence

Edited December 25, 2024 by farmerben

[darthgently]

12 hours ago, boriz said:

Thank you Darthgently . Another question if I may:

Is mass conserved when converted to energy? I.E. As a star loses mass, does the radiant energy (traveling at the speed of light) carry away that mass with the total conserved, but spread over a much greater volume? Or, when the anti-matter annihilated in the very early universe, did the universe have the same total mass before and after annihilation?

Farmerben said it.  As for antimatter stuff, I’m way unqualified.  I gather the asymmetry in matter/antimatter in the universe is necessary for all we see, but I can’t recall if anyone really knows why or how this asymmetry exists.  It seems like thermodynamic laws would be challenged or something, but I’m way out of my depth on that

[JoeSchmuckatelli]

On 12/23/2024 at 3:59 PM, darthgently said:

I’m calling BINGO on this guess of mine

 

What is truly remarkable is that serious researchers are now allowed to pursue these lines of inquiry.

 

Here's an article on what's described in the video.  Wrong again? Dark energy doesn't exist, the universe is "lumpy" - Earth.com

 

...and the publication of the authors: Supernovae evidence for foundational change to cosmological models | Monthly Notices of the Royal Astronomical Society: Letters | Oxford Academic ...

...They throw down a bit of a gauntlet:

"These results provide evidence for a need to revisit the foundations of theoretical and observational cosmology."

TLDR: they challenge the 'homogeneous and isotropic' presumption of the cosmos

 

Edited December 25, 2024 by JoeSchmuckatelli

[boriz]

Thank you Farmerben , Darthgently . Another... :

Gravity 'travels' at the speed of light. So stars on the edge of, say, Andromeda are currently feeling the pull from M31* as it was over 75,000 years ago, and the universe has expanded during that time. What's the gravitational equivalent of redshift? Is there one?

[JoeSchmuckatelli]

1 hour ago, boriz said:

What's the gravitational equivalent of redshift?

That's a neat question.  @K^2 ?

" Is there one?"

[K^2]

1 hour ago, boriz said:

What's the gravitational equivalent of redshift? Is there one?

51 minutes ago, JoeSchmuckatelli said:

" Is there one?"

I don't know if there's any special name for it in context of gravity, but yeah, gravitational waves do get "red-shifted." Relativistic Doppler Effect is a general name for the phenomenon, and it will apply to any wave.^*  If you're interested in how that influences gravitational attraction, that's a much trickier subject. For electromagnetic waves, you just compute the delayed potential (the technical term will probably get auto-censored, because of its unfortunate use as a slur) but gravity is non-linear, so when sources of gravity are moving, you have to solve the field equations from scratch. You can get a good approximation in most cases by using linearized gravity, and that works exactly like electromagnetism, that is, Newtonian gravity plus gravitomagnetic terms to account for relativity.

^* Yes, any wave, including particles. But "red-shifting" a particle wave just means reducing its momentum. And you aren't surprised that a particle fired at you at 20m/s from a platform moving at 15m/s away, is going to reach you traveling only 5m/s. We don't normally think of that as a Doppler effect, but it's really the same thing.

[Nuke]

On 12/23/2024 at 11:59 AM, darthgently said:

I’m calling BINGO on this guess of mine

 

here be dragons.

On 12/23/2024 at 6:07 PM, AckSed said:

Parker Solar Probe about to kiss the sun full on the corona for the first time: https://arstechnica.com/space/2024/12/were-about-to-fly-a-spacecraft-into-the-sun-for-the-first-time/

that sounds hot.

Spoiler

il be here all week.

 

[boriz]

 

2 hours ago, K^2 said:

gravitational waves do get "red-shifted."

I kinda assumed that. I was thinking more in terms of the field itself, not the waves. Sorry, should have been clearer. Not a scientist, don't have the terminology

 

2 hours ago, K^2 said:

If you're interested in how that influences gravitational attraction, that's a much trickier subject.

Well spotted, that's exactly what I'm interested in. I'm just spitballing some thoughts on the galactic rotation curve anomaly. Never liked the dark matter idea. Not that I reject it, just that until there's some direct evidence, I prefer explanations that fit better with established science than conjure new science. (I'm looking at you String Theory. Eleven dimensions?)

For example, what if gravity had two components, one much weaker than the other. The strong component follows the inverse square, the other does not, and falls off much slower, but it's effect is so small it is swamped by the stronger component over shorter distances?

Also, while we're here... We now know that Hubble's constant is not constant. Could the speed of light be similarly 'constant'? I.E. Could C be somehow correlated to the speed at which space expands? (Is it even theoretically possible to measure a change in C when your rulers are changing proportionally? *). If C were different in the early universe it would have huge implications for our estimates for the distance of deep objects, and the age of the universe, and other things besides.

*If you made a perfect 1m ruler, and you had a snail that always moves exactly 1m/hour, it would take exactly one hour to traverse the ruler. Now fast forward a billion years, space has expanded, the same ruler is now longer but still reads 100cm. You run the experiment again, and according to this ruler, the snail is moving 1m/hour, but this snail has actually covered a greater distance, so it's actually moving faster, isn't it? I think perhaps in order to observe this, you'd have to be outside the universe looking in, if that even makes any sense

[farmerben]

1 hour ago, boriz said:

 

For example, what if gravity had two components, one much weaker than the other. The strong component follows the inverse square, the other does not, and falls off much slower, but it's effect is so small it is swamped by the stronger component over shorter distances?

 

*If you made a perfect 1m ruler, and you had a snail that always moves exactly 1m/hour, it would take exactly one hour to traverse the ruler. Now fast forward a billion years, space has expanded, the same ruler is now longer but still reads 100cm. You run the experiment again, and according to this ruler, the snail is moving 1m/hour, but this snail has actually covered a greater distance, so it's actually moving faster, isn't it? I think perhaps in order to observe this, you'd have to be outside the universe looking in, if that even makes any sense

Modifying the law of gravity so that it has more terms is a very possible solution to the dark energy problem.  Dark energy relates to the problem that while the size of atoms, molecules, crystals, and planets remains fixed (assumption*), the space between galactic clusters expands.  If you do not assume fixed sizes, there are less elegant approaches with different assumptions like the laws of physics evolving with the age of the universe.

Dark matter relates to the problem of galactic spin.  A whirlpool spins fast in the center and slower with radius.  A disc spins at one rotational speed, with faster linear velocities at increasing radius.  Galaxies are not whirlpools, the outer rims spin too fast.  The effect varies from galaxy to galaxy suggesting that different galaxies have different amounts of dark matter.   Dark matter is much less a mystery than dark energy IMHO.

[K^2]

2 hours ago, boriz said:

Well spotted, that's exactly what I'm interested in. I'm just spitballing some thoughts on the galactic rotation curve anomaly. Never liked the dark matter idea. Not that I reject it, just that until there's some direct evidence, I prefer explanations that fit better with established science than conjure new science. (I'm looking at you String Theory. Eleven dimensions?)

For example, what if gravity had two components, one much weaker than the other. The strong component follows the inverse square, the other does not, and falls off much slower, but it's effect is so small it is swamped by the stronger component over shorter distances?

Having two forces would introduce more "new science." In fact, we know that additional forces would require new degrees of freedom. Extra dimensions, if you will. Gravity arises naturally from just the dimensions we have and can directly observe - space and time. It's part of what makes gravity so much nicer than other forces - I don't have to take it as a postulate that there is such thing as time or a spatial dimension. Unlike, for example, the spin degree of freedom, which gives rise to the weak nuclear force. That one's weird.

People usually talk about General Relativity and gravity in early 20th century terminology, because the idea of "there is a force due to curvature," is a lot easier to sort of get the vague idea of than the actual math under the hood.  But we've advanced quite a bit in our understanding of where gravity, as well as all the other forces, come from.  For gravity to work differently than our equations describe, there would have to be a very big elephant in the room that we're not spotting. It would involve new dimensions, violation of conservation of energy and momentum, and a need to explain why the equations described everything else so perfectly.

As far as we know, Einstein got it almost right. He discarded torsion terms. It appears that he was vaguely aware of them showing up in the math, and chose to ignore them, because they don't have an analog in Newtonian Gravity. Einstein was a very practical sort, and he just hammered at the math until it cooperated. This might have been one of the casualties. And the funny thing is, torsion terms factor into gravity when it involves massive rotating bodies. You know, like galaxies. I'll come back to that in a moment.

We've actually known about the discrepancy since the early 1920s (see Einstein-Cartan Theory), but I'm not sure how much attention was paid to it until a few decades later, when physicists started to understand forces as gauge field interactions, and quickly figured out that gravity is just one of these, but with an extra spicy gauge symmetry. Namely, Poincare group. Long story short, if our universe has three spatial dimensions plus time, and the natural symmetries of translation and rotation hold, then Einstein-Cartan Theory is the correct theory of gravity, and anything else would have to involve "new science." Like, in a radically new sort of way.

So back to the torsion terms and dark matter. Yeah, that was one of the first things people jumped to, but the problem is that if the torsion in Einstein-Cartan theory is responsible for the "dark matter", there is still an associated particle that we're looking for. And we're doing that anyways. From perspective of cosmology, it doesn't matter if that new particle is due to a gravitational effect, or is some completely new kind of particle that happens to be abundant, heavy, and almost completely non-interacting. So unfortunately, it doesn't save us from there being "dark matter," and merely points to the flavor of dark matter we might get.

And that's sort of the crux. Whatever the hell is going on with galaxy rotations is backed up by what we see in gravitational lensing, and either way, it behaves exactly like some sort of an abundant source of matter that's not directly associated with stars. So dark matter. Whether it's literal matter or not, whether it's a side effect of gravity or not, it behaves like a whole lot of non-luminous matter.

A quick search on keywords led me to this paper, by the way, which I'm mentioning in part because it has absolutely choice title. Einstein-Cartan Portal to Dark Matter. The abstract's worth reading. It says a lot of what I just mentioned in the last two paragraphs. Paper seems to be good too, in so far as I can tell with my limited cosmology background - but it's also full of very dense math.
 

2 hours ago, boriz said:

Is it even theoretically possible to measure a change in C when your rulers are changing proportionally?

You just hit the nail on the head. Speed of light is just the way for us to put the same ruler against time and space. It's a unit conversion, nothing more. Can proportions between time and spatial dimensions change? Absolutely. That's what the whole spcace-time-can-curve is all about. But we don't care about the absolute change. We just care how this relates to nearby regions of space, and how would you absorb the speed of light changing? Well, you probably know from optics that as the beam of light enters glass or water or any other optically dense medium, it slows down, and that cause the beam to be refracted at an angle. What if you wanted to keep the "speed of light" in air and the optical medium "the same"? Well, you'd have to bend the space itself along the interface, so that the beam can travel along the "straight" path.

When you get right down to it, there is no real difference between there being a curvature in the space, and proportions between different distances changes. And in fact, the latter is the actual math we use to describe gravity. In General Relativity we don't talk about the forces, and we rarely even talk about the curvature directly. Instead, we talk about the metric tensor, which is sort of like that yard stick, but it's recorded as a 4 by 4 matrix, because it has to account for all the different ways the ruler can get distorted as you move and rotate it. Metric is what we solve for when we try to figure out what "shape" the space-time around a massive body is, and it's also what we use to compute trajectories, figure out how time is dilated, and so on.

[boriz]

Thank you so much for indulging me guys. Having this opportunity to pick at bigger brains is a tonic, even if half of it goes woosh, over my head. I think my problem stems from a poor grounding in maths. I was the only person in my year that passed Physics but failed Maths LOL. My curiosity exceeds my capacity I'm afraid. But I'm a firm believer that a man's reach should exceed their grasp. I could keep going too...

EG: Is there a Lagrange point, that no-one mentions, at the center of the Earth? A zeroth, or L0 point perhaps?

(Bear with me). 'Down' is the direction of the CofG of the Earths mass right? And on the opposite side of the planet, this would be in the opposite direction. But near the center of the earth, there is a point where there is exactly as much mass in one direction as in another, the masses kinda cancel and the sum of gravitational 'pulls' reduces to zero, and will increase as you move away from this point towards the surface where the effect switches* and the 'pull' begins to reduce again?

(*Would this be called a manifold? Sorry, but my nomenclature lags my understanding somewhat)

Now zoom out a bit, so that instead of looking at a single clump of matter, you're looking at something more lumpy, like a galaxy. Wouldn't the same principal apply? So the 'sum pull' experienced by the innermost stars would be proportionally less than those a little further out? With a radius where this switches and the 'pull' begins to reduce again? Wouldn't it also apply to a black hole? Could this principal be extended further, say, to a cluster of galaxies, or even the observable universe?

Edit1: Would objects in this reduced pull region, in rotating bodies, be disproportionately effected by centripetal forces?

Edit2: And there's more *rolls eyes*: Any school physics book will tell you that as you raise a mass from the ground, you are adding potential energy to it, but what about if you keep raising it? Like 1000miles, or a million miles, surely this function peaks at some point then drops off at a rate proportional to the inverse square of the 'height'?

Edited December 26, 2024 by boriz

[magnemoe]

7 hours ago, boriz said:

 

I kinda assumed that. I was thinking more in terms of the field itself, not the waves. Sorry, should have been clearer. Not a scientist, don't have the terminology

 

Well spotted, that's exactly what I'm interested in. I'm just spitballing some thoughts on the galactic rotation curve anomaly. Never liked the dark matter idea. Not that I reject it, just that until there's some direct evidence, I prefer explanations that fit better with established science than conjure new science. (I'm looking at you String Theory. Eleven dimensions?)

For example, what if gravity had two components, one much weaker than the other. The strong component follows the inverse square, the other does not, and falls off much slower, but it's effect is so small it is swamped by the stronger component over shorter distances?

Also, while we're here... We now know that Hubble's constant is not constant. Could the speed of light be similarly 'constant'? I.E. Could C be somehow correlated to the speed at which space expands? (Is it even theoretically possible to measure a change in C when your rulers are changing proportionally? *). If C were different in the early universe it would have huge implications for our estimates for the distance of deep objects, and the age of the universe, and other things besides.

*If you made a perfect 1m ruler, and you had a snail that always moves exactly 1m/hour, it would take exactly one hour to traverse the ruler. Now fast forward a billion years, space has expanded, the same ruler is now longer but still reads 100cm. You run the experiment again, and according to this ruler, the snail is moving 1m/hour, but this snail has actually covered a greater distance, so it's actually moving faster, isn't it? I think perhaps in order to observe this, you'd have to be outside the universe looking in, if that even makes any sense

Universe expanding don't affect local stuff like galaxies or even gravitational bound clusters of them. 
If it affected local stuff it would include stars who would get dimmer as pressure in core went down and we know ancient supernovas work as expected
Example earth curvature is so large it only affect long ranges, laser or microwave towers, artillery fire and sniper rifle shooting at an km or more, making 20 km long tunnels but you want the center to be higher anyway for drainage. Initially it was just useful for navigation, 

[darthgently]

7 hours ago, boriz said:

or example, what if gravity had two components, one much weaker than the other. The strong component follows the inverse square, the other does not, and falls off much slower, but it's effect is so small it is swamped by the stronger component over shorter distances?

Sounds MOND related.  I think the timescape model works more simply for this as we already know that time moves more slowly as a gravity well deepens.  So the galactic core will experience time more slowly than the periphery possibly leading to the galactic rotational curve anomaly

I am no expert, far from it, but I’ve learned to trust Occam’s Razor along with trusting my BS detector and the dark energy hypothesis has always reeked of epicycles to me: fits data to a broken model in an illusory way.

[magnemoe]

28 minutes ago, boriz said:

Thank you so much for indulging me guys. Having this opportunity to pick at bigger brains is a tonic, even if half of it goes woosh, over my head. I think my problem stems from a poor grounding in maths. I was the only person in my year that passed Physics but failed Maths LOL. My curiosity exceeds my capacity I'm afraid. But I'm a firm believer that a man's reach should exceed their grasp. I could keep going too...

EG: Is there a Lagrange point, that no-one mentions, at the center of the Earth? A zeroth, or L0 point perhaps?

(Bear with me). 'Down' is the direction of the CofG of the Earths mass right? And on the opposite side of the planet, this would be in the opposite direction. But at the center of the earth, there is a point where there is exactly as much mass in one direction as in another, the masses kinda cancel and the sum of gravitational 'pulls' reduces to zero, and will increase as you move away from this point towards the surface where the effect switches* and the 'pull' begins to reduce again?

(*Would this be called a manifold? Sorry, but my nomenclature lags my understanding somewhat)

Now zoom out a bit, so that instead of looking at a single clump of matter, you're looking at something more lumpy, like a galaxy. Wouldn't the same principal apply? So the 'sum pull' experienced by the innermost stars would be proportionally less than those a little further out? With a radius where this switches and the 'pull' begins to reduce again? Wouldn't it also apply to a black hole? Could this principal be extended further, say, to a cluster of galaxies, or even the observable universe?

Edit: Would objects in this reduced pull region, in rotating bodies, be disproportionately effected by centripetal forces?

I don't think so as the gravity gradient is so weak outside of the black hole in the center. Earth gravity is not uniform, Starlink and probably others uses this to change inclination. 
Moon is so lumpy, I assume because all the metallic asteroids hitting it (mining locations) so low orbits are not stable. Its couple of degree at worse so you watch an string with an weight at noon and it visible don't point down. 

[darthgently]

12 hours ago, K^2 said:

I don't know if there's any special name for it in context of gravity, but yeah, gravitational waves do get "red-shifted." Relativistic Doppler Effect is a general name for the phenomenon, and it will apply to any wave.^*  If you're interested in how that influences gravitational attraction, that's a much trickier subject. For electromagnetic waves, you just compute the delayed potential (the technical term will probably get auto-censored, because of its unfortunate use as a slur) but gravity is non-linear, so when sources of gravity are moving, you have to solve the field equations from scratch. You can get a good approximation in most cases by using linearized gravity, and that works exactly like electromagnetism, that is, Newtonian gravity plus gravitomagnetic terms to account for relativity.

^* Yes, any wave, including particles. But "red-shifting" a particle wave just means reducing its momentum. And you aren't surprised that a particle fired at you at 20m/s from a platform moving at 15m/s away, is going to reach you traveling only 5m/s. We don't normally think of that as a Doppler effect, but it's really the same thing.

Something you are saying here is confusing me so I’d like to take the opportunity to get educated if it isn’t too much a bother.  Embracing the “there are no stupid questions” stance:

I thought both gravity and EM followed the inverse square with distance.  What am I missing here? Is it related to gravity’s more fundamental relationship to space time that leads to this relative non-linearity in the gravity case?

[magnemoe]

4 minutes ago, darthgently said:

Something you are saying here is confusing me so I’d like to take the opportunity to get educated if it isn’t too much a bother.  Embracing the “there are no stupid questions” stance:

I thought both gravity and EM followed the inverse square with distance.  What am I missing here? Is it related to gravity’s more fundamental relationship to space time that leads to this relative non-linearity in the gravity case?

Inverse square or rather cube x^3  affect any point source like a star, double the distance and its 6x dimmer. 10 times the distance and its 1000 times dimmer. 
Red shift is unrelated, think sounds of an train or ambulance passing you. Or you moving away from sound who it probably more of an bomber crew sound.