Dark Matter Isn't Just Dark. It's Invisible.

take this particle make it the opposite charge turn it the other way but it's not the anti-particle it's the other it's the other anti-particle right it's this other one but then you gotta take it flip it around shove it in a hole right and then we have a cute little acronym that we call it right [Music] hey crazies welcome to another installment of wife reacts this is my wife awkward m hello today i'm gonna be explaining dark matter to her let's see how this goes let's okay so first off i guess what exactly do you know about dark matter so we can get a bass line here it doesn't emit light there's a lot of it yes i know that vera rubin who's an important lady that i think that's it that's about it okay but before i get into this because i know there's going to be a bunch of people that are going to mention this in the comments you know who you are it is entirely possible that we don't understand gravity as well as we think we do sure that is possible but the ways in which we would have to change our models of gravity to explain all of the things that dark matter explains is it it's absurd it is actually less work to just accept dark matter right and so it's it's possible that we don't understand gravity and it's possible that maybe one of the things that we attribute to dark matter is just could just be explained by modified gravity like one thing but not all of them sure and so most models that include some kind of modified version of gravity also include dark matter because they know that it can't explain everything okay so we're not saying that modified gravity doesn't exist at all right it just is not a full explanation of all of the effects of dark matter correct okay all right so then the question remains what exactly is it prepare yourself for some acronyms oh love a good acronym here we go oh they're the silly ones aren't they yes oh no okay candidate number one machos right which stands for massive and compact halo objects okay the halo is a region of the galaxy outside of the disk side of the disk the galaxy is spun into a disk a spiral disk which is where most of the luminous matter is and then the halo is everything outside of that now there are things out there like i didn't know there were things out there there are things out there like they're called globular clusters it's these clusters of stars that are really densely packed there are these objects that are in the halo of a galaxy and they're massive and compact so we're talking things like rogue planets white dwarfs neutron stars black holes yes comfortable with that those are all considered massive and compact halo objects or machos okay okay so that okay these are all very ordinary things right we wanted dark matter to be ordinary things that we just weren't seeing sure the problem is we can do rough estimates right ballpark order of magnitude estimates of how many of those things we expect to find and it's nowhere near enough the rest of it the rest of the 84 of matter that is dark matter has to be something more exotic based on our evidence of dark matter it has a few properties that we can say conclusively about it now we call it dark matter but it should really be called invisible matter it's actually legit invisible it doesn't interact with light at all it does not block out the light if the light is behind it right like you would expect for like a planet or something like that exactly or some like dense dark nebulous cloud it's not like that it must not interact with light we usually say at all but technically it could a little bit but in a way that's below our ability to detect which is weird yeah that's weird and it's a lot lower than normal matter would interact with light sure and if it doesn't interact with light it's not electromagnetic at all that means we can't put it in a container either why because the reason that your hand doesn't go through things is because of electro electric repulsion right the electrons in your hand from your subatomic particles exactly okay we know that if it doesn't interact electromagnetically then it doesn't do that and so you couldn't put it into contain it'll just pass right through the walls of your container not only can it not be seen it also can't be held do we have dark matter in our galaxy absolutely we have dark matter in our solar system so i think that already shows us that like we can't interact with it right that's apparently here and yet now there isn't much of it we know what density we should expect it to have and that density is extremely small we're talking like if you took all the dark matter and our entire solar system out to neptune's orbit and you collapsed it into an object okay it would have the mass of a medium-sized asteroid which is very small okay astronomically bigger than i was anticipating based on what you were saying that's pretty small astronomically speaking okay but if it doesn't interact electromagnetically then it wouldn't ever form an asteroid right why would it that electromagnetism is what slows things down and generates heat and like saps energy away and so if it doesn't interact electromagnetically then it doesn't slow down which means it can't clump the best we can do is just a diffuse cloud of it a cloud of stuff that can't be seen and doesn't interact with anything except gravity invisible hence invisible so we can only see it based on its gravitational effects i mean but have we actually found its gravitational effects in the solar system no no because there's not enough of it okay that makes sense asteroid mass isn't gonna do much to our solar system which is why we don't see it here and we don't see it on a you know a stellar scale either it has to be an interstellar galactic scale before we start to see its effects okay before the scale is large enough that there's enough mass to actually do something while technically the dark matter is here and it is gravitationally affecting things it's not really that much there's much much bigger influences okay our next category next candidate for dark matter they're called wimps okay who named these right you needed like i think they're the coolest acronyms in in astrophysics hands down nick's over here like so wimps are weakly interacting massive particles they're not big compact objects they're little tiny particles and there's just a lot of them you know what i think i'm really struggling with massive how can something have a mass if it doesn't interact electromagnetically what gives you the impression that something has to interact electromagnetically to have mass because generally we say that things that have mass are made up of particles i'm thinking that in order to have mass you need some protons neutrons and electrons which is not true it doesn't have to be electrons neutrons and protons or quarks or whatever right there are a lot of particles in the standard model which is going to be a big deal today this the yes okay the big chart you want to throw that up for them definitely definitely going to happen so there's a short list of elementary particles and then there's a whole long list of particles that are made from those particles like protons and neutrons are not on the elementary particles list fair enough i'm a biologist okay that's as far as i need to go they're made of smaller particles called quarks but those quarks only represent about one percent of the mass of a proton the other 99 is actually made up of massless particles called gluons i don't like it at all 99 of the mass of a proton is from massless things the whole concept of mass it's it's very different on a quantum level than it is on a normal level different it's such a polite word for it try to leave some of those preconceptions you know try to set them aside you can take that and no all right all right i'll accept it i will accept that it is massive even though it is not made up of particles or it's made maybe made up of particles that don't have mass or whatever or they do have mass but they don't have any charge and if they don't have any charge then they can't interact electromagnetically oh so they could be neutral yes okay i'm comfortable with that now neutrons do interact electromagnetically even though they're neutral because their parts aren't the quarks have charge even though together they form a neutral particle that makes sense if we want dark matter to be one of these wimps one of these weakly interacting massive particles we need to make it a massive particle that's an elementary particle okay that isn't made of charged parts right okay i accept this it is made of particles yes just a neutral particle that is not made up of any other charged smaller bits like neutrinos neutrinos could be dark matter because they are massive they have mass not very much but they have mass and they don't have any charge their neutral is why we call them neutrinos okay but they do interact with something because we can detect them that's the word i'm looking for right we do have neutrino detectors and these they're the big tanks full of oil basically these neutrinos are tiny they're tiny amount of mass and they are very weakly interacting so even though we have these giant tanks full of oil they only detect one or two neutrinos a day but there are a hundred trillion neutrinos passing through your body every second that's uh invasive just passing out neutrino i did not consent to this okay but they're not just passing through your body they're passing through the earth right right so these neutrino detectors detect neutrinos from all directions including down some of these neutrinos pass straight through the earth and then hit a molecule in the oil and based on what that interaction eventually emits we have detectors around the outside of the tank and we can determine not only the energy of that neutrino but what direction it came from so we can know if it came from up or down we've got something built into the standard model that could be dark matter so it's not that it doesn't interact it is that it weakly interacts on such a small scale that it's not meaningful until it's until you have a lot of it right we've got these things called neutrinos right and they sort of they fit the bill they they match what we expect dark matter to be right almost oh no most neutrinos are traveling very very fast like near the speed of light and so they're carrying a lot of energy kinetic energy and that is not something we expect dark matter to do carry kinetic energy or a lot of connecticut carry a lot of kinetic energy anything that has mass and moves around i mean anything that moves around at all has kinetic energy even photons of kinetic energy when we model what we expect dark matter to look like we expect it to be something we call cold dark matter and by cold we just mean not moving fast interesting use of words it's kind of analogous to how thermal energy works when things are moving really fast it's hot and when things are moving slowly it's cold and so it's kind of just reusable to that yeah we're using hot and cold analogously like that and so it makes sense at absolute zero on the kelvin scale can i say that yeah kelvin scale is a complete absence of movement right aside from some weird quantum uncertainties yes because nothing can ever be exactly zero but yeah so we expect most dark matter to be cold not moving very quickly so most of the neutrinos we see don't actually fit the bill they might be dark matter but they're not cold dark matter now this doesn't rule out neutrinos though there are slow-moving neutrinos we can't detect them because in order for them to actually like the the more energy they have the more likely they are to interact in our detectors fair enough and so we can't actually detect the slow ones but the idea checks out mathematically right and we do expect them to exist we know that whether or not a neutrino is affected by with the weak interaction is determined by whether or not it's spinning clockwise or counterclockwise whether or not it's right-handed or left-handed okay so only one like only left-handed or only right-handed right will interact with the weak interaction interaction yes okay you're familiar with that that matter has an anti-matter partner sure okay well each one of those the matter and the anti-matter can spin two different directions you can have that matter spin clockwise or counterclockwise you can have the antimatter spin clockwise or counterclockwise only one from each set is affected by the weak nuclear interaction left-handed regular matter is affected by the weak nuclear interaction and right-handed anti-matter is affected by the weak nuclear interaction but the left-hand anti-matter and the right-handed regular matter are not sure they're called sterile okay because they don't interact with the weak force got it what's complicated is that we've talked about so many particles at this point that my brain is like i don't even know what particles we're talking i was i was worried about that i am particle overloaded this is why people are like that's ridiculous because this is what it's not there's so many different like little things you're like take this particle make it the opposite charge turn it the other way but it's not the anti-particle it's the other it's the other anti-particle right it's this other one but then you gotta take it flip it around shove it in a hole right and then we have a cute little acronym that we call it right yes and it may or may not be real we don't know no no these are real these are real okay thanks for letting me get that off yes but if the sterile neutrinos don't interact with the weak force and we already know they don't interact electromagnetically they're only going to interact gravitationally they'd be considered a weakly interacting massive particle and we do have a tiny tiny bit of evidence from our neutrino detectors that they do exist there's enough evidence to hint that they do there's enough evidence to say that we should study that more yes absolutely but the point is we know that dark matter has to be there it doesn't have to be one thing it could be a combination of all of these things but the point is that the overwhelming majority of this effect must be matter we know that it's matter because it's massive right when things are massive and they can move around that's what matter is right right and so we know that it's matter we just don't know exactly what type of matter it is and it could be a combination of things but in terms of the two broad categories in terms of machos and wimps we expect dark matter to be overwhelmingly wimps thanks for liking and sharing this video a special thanks goes out to all my generous patreon patrons and youtube members for making all this possible don't forget to subscribe if you'd like to keep up with us and until next time remember it's okay to be a little crazy if the earth could fit in your hand it would be heavy yeah i mean subjectively sure if you kept the earth the same density it would be a fairly smooth sphere with a weight somewhere between aluminum and steel some people might call that heavy anyway thanks for watching

Channel: The Science Asylum

Views: 216,636

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Id: cncCu7iJE24

Length: 16min 22sec (982 seconds)

Published: Sun Oct 17 2021