@MichaelKingsfordGray Did you drink your cup of vinegar today yet?

I agree. Btw. She's called Dr. Maggie.🙂

Yeah, and she's really cute too.😎

;)

Paredolia kicked in pretty fast there.

It's called the Cheshire Cat galaxy group

Immediately made me think of the Majora's Mask Moon

I only have a bachelor in physics and astronomy but yeah it really depends on the model used. It is one of the reasons why there is a relatively big focus on neutrinos and neutrino detection since maybe the weakly interacting neutrino's will shed some light on it.

To clarify that statement, it means that a WIMP is a particle which interacts gravitationally and any other force no stronger than the weak nuclear force. Currently the only known force (other than gravity) which meets that criteria is the weak force, so unless there is another unknown force then the only type of WIMP is those that interact via the weak force. We shouldn't necessarily expect dark matter to interact via the weak force, but it has been favoured as a theory thanks to dark matter self annihilation cross section predictions and supersymmetric weakly interacting particle predictions having the same mass range. While there are astronomical differences between WIMP dark matter and other candidates (such as axions), detecting these differences is very difficult. One such difference would be an excess of gamma rays from regions with lots of dark matter. Gamma ray observations have been used to constrain dark matter theories for this reason.

@@lewribaedi5997 No "dark matter" has ever been discovered, let alone authenticated. It baffles me that lay people, graduate students, & professional scientists alike all keep talking about "dark matter" like they've already known much about "it." They know ZERO about "it." It's just a hypothetical "particle" reversed engineered to explain something they can't explain, when it comes to large STRUCTURAL behaviors or properties in the Cosmos... Anyway... growing up --- especially as I was going through college --- the one name I hated/disliked to hear or to read about the most was "Henry Kissinger." Now, the one thing I hate to read about, or hear, the most is this so-called dark matter. As a middle aged person, with a decent education from a research university with the 5th or 6th largest R & D in America.... I hope before I die, in the next 30 - 40 years, that the "James Webb" telescope (or perhaps the same instrument by another name) and/or other instruments (to be constructed & deployed, in the up coming years) prove that this so-called dark matter is nothing more than one of the latest Planet Vulcan or ether "theories" that everyone --- especially "experts" --- seem to think they know almost inside out (e.g. know nothing about). Fact of the matter is, there is absolutely no imperative, or logic, that says there had to be something like "dark matter" for matter & energy or large scale structures to act the way they do. Large scale structures --- e.g., black hole, galaxies, clusters of galaxies, walls or sheets of clusters of galaxies that span tens to hundreds of millions of LIGHT YEARS --- could simply be behaving in some unfamiliar (to humans), large-scale structural manner that current astrophysical and astronomical theories haven't described or ironed out, in their description of the cosmos. Further, if Einstein's GR is right, than the "gravity well" or the distortion of space-time at the galactic scale & up.... around the "local space" of each galaxy or clusters of galaxies.... is the very reason why "stars and galaxies" don't go "flying every which way" into space-time, in the first place... That is, there's no need for "dark mater" to exist, as the "reason" for HOW stars & galaxies are not violating the underpinning for General Relativity: the distorted local space-time, ITSELF, around large structures of the universe (e.g. Black Holes, galaxies & their rotational velocities, etc) is what is preventing "stars and galaxies from flying every which way." Mass & energy were NOT put there (in some local space), first, with space-time being erected, at a later date, as a fence... to keep stars & galactic structures from "flying every which way," ad nauseam. BTW, while tutoring high school students up in the Twin Cities, I exchanged two very short emails with the mathematician Gordon L Kane.... about 12 years ago... on Super-Symmetry, a subject on which he had written a book. Kane thought it "would be discovered within a few years." Over a dozen years is, in my estimation, more than "a few years." And in some ways "Supersymmetry" is even better articulated than "dark matter."

This was already clear to many people

We can never prove something *doesn't* interact with a force, just like we can't prove the photon is massless. We can only ever determine experimental upper bound on those interaction strengths or masses.

It's evidence against the Dark Matter of the parameters used in the simulations. For all we know, it could be multiple types of matter, modified gravity or a combination of them. It may even be that the Dark Matter(s) modifies gravity somehow. If it is, we're pretty much screwed unless we can either produce some Dark Matter candidate at a collider, or make enough astronomical observations at better accuracies to actually figure out the numbers.

@@kwanarchive except it's not. Please read my reply above.

@@lewribaedi5997 KZfaq shows your coments first. So for me, your reply is not above.

They only do it once every few billion years, they have time to build up their no-claims discount in the interim

Astronomy level maths isn't in anyone's skill set naturally, you have to build up to it. maths is just logical steps to find a solution, you can do it.

So say we all

Kinda hate it when people talk like this.. really devalues the work people put in to actually learn the maths. No one is born with a full set of mathematical logic, you learn it

@@Twitchi I know, right?

Don’t give yourself that excuse; if I made it through you could - it just takes a little more work for some of us.

My self see ahead just a few more years.

Me too. It really triggers way too many questions but maybe the answer is as simple as: these galaxies have no, low or unevenly distributed dark matter, something we know that does happen.

1st part: no not really. The problem with the Trainwreck cluster is that it appears to have a "dark core", that is to say it appears as if the dark matter has clumped together. This goes against the idea that dark matter is collisionless (as seen with the bullet cluster). The solution is more likely that it is an anomaly in the lens reconstruction. Newer research using a different algorithm resulted in a lens map which is not inconsistent with current theory. As for some physicists claiming that the bullet cluster is against dark matter, they base that off of the fact that a simulation found the cluster velocity to be unusually high to the point where it is extremely unlikely. This was later resolved by more up to date simulations which found the bullet cluster to be consistent.

@@lewribaedi5997 - Thank you very much, Lewri. So basically "negationist physicists" are clinging to burning nails, grasping at straws, in order to keep the search for non-Einsteinian gravity alive? That's somewhat worrisome.

perhaps the same way that the accretion disk of a black hole heats up but on a much larger scale. or tidal forces?

I think it's only the gas in the intergalactic medium and the galaxies themselves behave normally

The gascloud has a gravitational center, but the molecules are scattered far from it, thus they have high potential energy. As they are pulled together by gravity this energy transforms first to kinetic energy(as they speed up towards the gravity center) then to thermal energy by collisions and friction. Not an expert, feel free to correct me.

There's a thing in mechanics called the _virial theorem_ which relates the average kinetic energy of a bound system of particles to its total potential energy. Roughly stated, we find that a system with total potential energy _V_ has average kinetic energy _T_ = 1/2 _V_ .So the greater the total potential energy, the greater the average kinetic energy of the constituent particles. And average kinetic energy of particles is what we mean by temperature.

It's precisely not gravity what causes it, gravity does nothing: the stars and the dark matter just go through unscathed because their inertia is much bigger than whatever gravitational drag they experience in the galactic collision. On the other hand, gas is scattered all around and thus experiences *electromagnetic friction* with the other gas cloud and thus gets heated and also slowed down in its movement.

Th red parts or gas sides is just an effect of somthing like a quasar right side as the light hits the electromagnetism that all systms have.

write a paper on it and send it to journals, then it can get peer reviewed and you can see what others in the field think of your hypothesis

​@@thomasorwell7628 Better Idea pay $2 for SpaceTime discord and bring it up there. All the high level scientific discussion of your hypothesis you might need. 👍

Unless I'm misunderstanding, your analogy sounds like the normal behaviour of gravity. But, I believe a cosmological constant (or as you say 'spacetime tension', which is equivalent) is still very much a possible explanation for Dark Energy - although this is something with a repulsive effect (not an attractive effect like Dark Matter). However nonlinear gravitational effects are now pretty much ruled out as an explanation for Dark Matter due to observations of the bullet cluster collision and others - briefly mentioned at 3:42 is the observation that the dark matter from these clusters seems to be continuing to move past the collision site, like inertial masses, along with the stars in the clusters, while the gas from each cluster has smashed into each other and has been left behind in a heated blob at the site of the collision. If we were looking at a spacetime phenomenon, some of this phenomenon would now be associated with the mass of the blob of gas left behind, but there is none. Therefore Dark Matter does seem to be some sort of 'stuff', rather than being some sort of feature of spacetime.

You're describing gravity, things like 'frame dragging' around spinning black holes are a manifestations of this. The problem is that it produces the gravity we see in normal matter, nothing extra. Your mechanism would need a process that allows large things like galaxies to manifest this extra force, but not 'small' things like our solar system. (The sun is a heavy object and this 'dark matter effect' would amount to 4-500% extra gravity from mass.) Another issue is that soem galaxies seem almsot devoid of dark amtter while others are more than 99% dark matter. That kind of variance shouldn't really occur if DM is an effect rather than stuff.

Irregularity in dark matter findings (some galaxies appear to have no or very low dark matter, while most do have the normal amount) strongly suggests that general reformism of gravitational knowledge is not going to solve the problem at all, that some sort of actual dark matter must exist and be overly abundant. However it does not need to be WIMPs, it can still be MACHOs, specifically black holes, primeval or otherwise smallish, if the late Hawking is to be given any credibility (he argued for them, at least as a possibility, in 2014).

I don't think so, mostly because we expect gas to be in and around galaxies and not just floating in the middle of nowhere for the greatest part, that gas is the gas that was in the galaxies and frictioned with each other as they "hit" each other, creating such a fascinating heating, drag and shock bow. I wonder if that left-behind gas can explain galaxies without dark matter, as such heated gas should eventually produce stars but without DM, they would be only weakly integrated in galactic clusters gravitationally.

Intercluster gas is extremely low density. The intracluster gas is much higher density and is what is observed here.

@@lewribaedi5997 - The blue blobs are not gas, they are gravity or mass. They are only denser in that sense of mass but not at all in terms of gas (red zones), which they seem to have been stripped of by the collision.

@@LuisAldamiz I realize it would be unlikely for the gas to be outside of a galaxy or cluster but the universe is so big it seems like it could still happen..maybe. it's our only example of this system, only visual proof of dark matter other than gravitational lensing, so it's already an outlier among the rest of our observations. I've been having trouble with the sun formation model and maybe you can help me. I know how its explained to happen but when I "model" it in my head I'm having some disconnect. Ok, how does the lightest atoms, hydrogen, manage to coalesce into stars in a vacuum such as space? Wouldnt the atoms want to naturally spread as far apart as possible and seek a uniform distance from each other in the vacuum? Even inside earths gravity well but in a vacuum chamber, the atoms will dissipate rather than gather together. I've heard nebulas described as practically vacuums on this channel and yet they're creating stars. Wouldnt all gas clouds need bow shock running through them at some point in time in order to get enough concentrated mass for gravity to be able to take over enough and bring the hydrogen together?

Underrated comment.

It's called the Cheshire Cat cluster 😊

So beautiful!

Dont forget about the cluster guys. Its beautifull too!

. . . . .. .... .

@@Cole-jb5ip How could I argue with that?!

yes it will be intresting

I'm also curious about this especially since they're always happening and yet everything around us is red-shifted... until it's not. So for us the Andromeda Galaxy is blue-shifted (coming at us) and basically nothing else (which I guess somehow also includes all those proto and dwarf galaxies the Milky Way is consuming right now). Go figure.

Just because the universe at its largest scales is expanding doesn't mean gravity stops pulling objects together. Currently, the effects of dark energy only *begin* to be felt at 1000 megaparsecs or so. The Earth still pulls us to it, the moon still orbits, galaxies still attract each other and collide, and in structures as massive as the Bullet Cluster, gravity far outclasses dark energy.

@@KevinVanOrd You know how I know that you have no clue what you're talking about? 1000 megaparsecs is roughly 3.085*10^22 km. The Milky Way is only 120 million light years in diameter roughly 36,971 kilo Parsecs... So somehow our galaxy's formation is beholden to an effect that is only really able to be enacted on objects that are nearly 30 times larger than our galaxy? Try again.

@@VariantAEC The Milky Way's diameter is of the order of 100,000 light-years (30,000 parsecs).

@@denmaroca2584 My bad, I made a typo. The comma in 36,971 should be a read as a period making it 36.971 kiloparsecs this also assumes the upper bounds for the diameter of the Milky Way at 120 million light years. Knowing that does it change what I said? No.

If you know Celsius, you're fine. Any number that large in Kelvin will be indistinguishable from its counterpart in Celsius, since the two scales have equal-sized units, just shifted by about 270 degrees.

@@OlleLindestad I was joking around. Hundreds of millions is, effectively, the same on any scale.

I believe the first major evidence for dark matter was in the work Vera Rubin did in looking at the rotation rates of galaxies. The speeds of stars orbiting the centers of galaxies were very different than you would expect given the 'normal mass' in those galaxies.

@@maitland1007 ah I maybe that is what I was trying to remember.

Hubble saw stretched galaxies and some one said, "hey that isn't right." Then scientist started taking images in different wavelengths and got all excited.

The Sun does bend light. Gravitational lensing was first seen in the solar eclipse of 29 May 1919. Dark matter wouldn't affect the Sun's gravitational lense because dark matter doesn't clump around stars or planets

Deep sky videos is another channel from brady, there are more videos with her

Not too different from what we see now, at elas to the naked eye. Recall the andromeda galaxy is quite close and quite big in our sky, but not very noteworthy. (Indeed sad to say even the milky way, that strip of stars across the sky, is not often seen by many people who lack a clear sky.) Some of the galaxies nearer the center have quite a few andromedas in their sky, enough to have a scatter of impressive galaxies across their celestial sphere, but nothing more spectacular than our celestial sister here.

It would look pretty much the same except that all the dust and gas would be not in the galactic plane as it is now but above or below it, that's exactly what the red blobs are: gas and dust dragged behind the collision because electromagnetic friction with each other. We'd probably have a much better look of the galaxy as such thanks to that.

Ah. It’s not Deepsky videos.

This is Sixty Symbols

@@Zveebo Yes, I saw the thumbnail and assumed it was Deepsky.

Surely you can agree it's messier than other objects.

@@kolyaschaeffer5760That pun never gets old. And gives me a merry feel. :D

Even that would be overcooking the stew. The bullet cluster may be inconsistent with some versions of MOND, and maybe consistent with some versions of dark matter is about as accurate (but still biased) as you can be and not step outside of "truth" (whatever that is)

Later analysis supports the dark matter explanation with lower velocities.

It's only the gas that's interrupted. The stars and planets have enough space to pass through each other.

I can’t unsee it now

If you ask me this 'dark matter' is actually giant galactic bar magnets. Once you embrace the amgnetic universe you have no need for all this so-called 'science' they keep going on about!

No. It either explains everything or explains nothing about DM.

Thanks for sharing, Brett.

The bullet cluster is evidence of dark matter; the trainwreck cluster cannot be explained by dark matter

@@chriswarburton4296 Didn’t seem complicated to me either….

@@droppedpasta Be nice...

The bullet cluster is evidence that dark matter is “stuff” that moves independently of normal matter. If dark matter was actually just a missing parameter in the equation for the strength of gravity at cosmic scales then it would still cause lensing around the center of visible mass of the galaxies, only the strength of the lensing would change. But in the bullet cluster the lensing is occurring far away from the visible mass, indicating most of the mass of the cluster isn’t anywhere near the visible portions. Hence the lensing is caused by something that exists but isn’t being detected like the rest of the cluster. The trainwreck galaxy doesn’t disprove that dark matter is “stuff”, it just raises questions about the exact nature of how that stuff behaves like does it interact with itself and other matter at all, how weak or strong is that interaction, and so on.

Have to admit, beyond the experimental data and explanations, the description of space-time is "odd". Has hints of aether from the past, and although the "why" has been given, the "how" seems incomplete (it seemingly has physical characteristics but no mass or wave to carry those characteristics, just is like another substance of yore). Too bad we all end before the story is complete (if ever).

Are gravitational waves really a distortion of spacetime? No.

Me me me

Some prefer the term "dark gravity" because it doesn't make assumptions about its source. Some physicists (a minority) entertain the idea that it is a manifestation of deviations of gravity from Newton's law at large distances from the gravitating body.

Dark matter was originally a term coined to describe apparent gravity from unknown sources. Matter "is gravity" (somehow causes it, nobody knows exactly how) and dark matter is the huge load of matter we can't see (hence "dark" although "invisible" or "transparent" is technically more correct) because, unlike regular matter, does not interact with other stuff, or even itself, via electromagnetism (hence no bouncy photons tha can tell us more).

Some people say so, but I suspect that 'quacking' is just the wind disturbing water. I'm a believer in POND.