October video: Is there dark matter in the solar system?
The Local Dark Matter Density by Read: https://arxiv.org/pdf/1404.1938 GNOME paper: https://arxiv.org/pdf/1807.09391
GNOME ppt 1: https://indico.cern.ch/event/672881/contributions/2819492/attachments/1584423/2504619/bristol18GB-Barontini.pdf
Comments (62)
I loved that video. The cutest thing was when you thought the audio might be ruined because of your bluetooth things. ".. oh man ..." priceless!
Yay do a live event!
Good video 👍
Does this mean MOND is ruled out? I mean if we can say it is certainly in our solar system it can not be MOND anymore because then it is not a particle or am i missing something? Also i have no idea what i am talking about so yeah maby MOND has been ruled out years ago and i just don't know
this was a fun video. understandable enough to be entertaining! when all of the things talked about in previous videos came up i could not remember a single one. Then i spiraled for a bit thinking about the implications of my pisspoor memory for science communication. i'm ok now. on the plus side me not remembering much means those videos are ripe for rewatch :)
Some "back of the envelope" calcs. If you take .005 solar masses and distribute it equally in a sq parsec you get like 3.385 × 10^-22 kg/m^3. Avg density of the universe is 9.9 × 10^-27 kg/m^3. So 1000x more dense than the universe as a whole. But 3x less dense than our galaxy 10^-21 kg/m^3. OK so lets take that mass and evenly divide it into Planck Length buckets. So you dope out the mass into little PL buckets that fill up a square parsec. How much mass is in each square PL? 2.726 × 10^-75 kg of mass. Way, way, way smaller than an electron. 9.1 × 10^-31 kg. OK so here is the leap. That's such a little scrap of mass. What is the Schwarzschild radius of that tiny tiny mass? ~4.051 × 10^-102 meters! That's tiny! Way smaller than a PL. So plausibly dark matter is hiding behind the PL?
"I need to finish the thing before I start the Zelda game because that's all I'm going to do until it's finished" is very relatable.
After her Picard video, I'd actually love to see her go full gamer review on Echoes of Wisdom
I would love to see another video while playing a game like Zelda, Angela. I find it amazing you can play while deep diving into physics topics. I also loved the Q&A video you did - I'd put my hand up for another one of those... 🙂 Or... a combination of both?? 😜
Dark matter in the solar system, my initial thought looking at that graphic was of course, but maybe it’s just sometimes because of how sparse it is and that’s why we can’t find any? In retrospect it’s a bit embarrassing given how large the solar system is, I was imagining it as being clumped instead of more uniformly distributed.
Hi Angela, great video! One (maybe silly) question that I have is: if DM is collisionless, how does it actually "lingers" into places? Like, Baryonic matter loses energy by collisions, so we get the sun and planets due to baryonic matter colliding and then becoming an every big blob of dust together. But if dark matter doesn't do that, then wouldn't it just "keep falling" gravitationally on a same place, or even just "fly away"?
Not Angela (obvs) but if I remember my galaxy simulations from undergrad: you still get structure formations even with a fully collisionless system as momentum and energy are transferred between particles. Like: 95% of particles congeal into a blob, and then 5% shoot out into infinity, carrying all that "lost energy." IIRC, that mostly happens pretty early on, so that's why at steady state, you see those massive isotropic dark matter haloes, rather than having the dark matter compress and compress into super-dense points.
Shower thought for today. With "conventional" matter you have matter as a wave-function that hasn't congealed into a thing until it's measured, then upon measuring you get collapse and have a particle, a thing. Maybe with dark matter it's similar but opposite, you have a thing but upon an attempt to measure it you lose the thing and now it's some analogue to the wave function. So we can observe its effect on a macro scale, but it's not possible to measure. It could be interpreted as something that doesn't interact, but on the contrary it's very interactive it just has exactly the opposite effect on interaction that we're looking for. Just as conventional matter wave function will always collapse on interaction every time without fail, dark mater will always "vanish" on interaction every time without fail.
I'm sorry for the completely random question but I always think about this when the Big Bang comes up. Are you philosophically a Determinist? A Compatibalist? Something else?
7:35. Yes! I'm here for Dr Collier office hours
Correction: according to Wolfram Alpha, the ratio between the local baryonic matter density and the local dark matter density is 9.1 per thousand. That's 0.91% and not 0.0091%, which is what you say in the video.
Does Dark Matter contribute to the mass of Black Holes? Perhaps, after billions of years the particles in the Dark Matter halo would "fall" into the Black Hole at the centre of the galaxy?
Angular Momentum? Ok...
When you mentioned the Super-Kamiokande I thought, wait, "kami o kande"? (Which my rusty Japanese translated as 'bite God'?) Like finding a neutrino is like taking a little bite of God? How cute would that be! Except it turns out it's just a nickname based on Kamioka (the region it's in) NDE (Neutrino Detection Experiment). Oh well!
Nice video, thanks, communicated the essence successfully I would say..
Video was great. I would have wanted to call it the Super Kamehameha detector so much
It wouldn't have even occurred to me that there wouldn't be dark matter in the solar system. I can see now that if it isn't a particle then it might not be here.
So there seems to be some connection between the dark matter is a particle, how much mass it has, and if it has rare interactions with other matter. How can we assume that these hypothetical particle properties are tied to observables? That part is not clear to me.
I answered "No" to the Any Dark Matter in the Solar System. What a dunce! Then again .. surely Dark Matter must still be theoretical if it has never been detected? Not just that, there are wildly different percentages of the amount of the said material dancing away in text books and podcasts. Yet, i love everything you broadcast, Angela. Best science communicator. There's just no hope for the D- brigade . Sorry to be one of them..
Except that dark matter has been detected - that's why it's not a theory. It's an experimental observation that there's stuff with mass that we detect on a large scale, but it doesn't seem to interact with the electromagnetic field, so we can't see it as anything other than this nebulous mass. What hasn't been done is observation of DM in isolation from our usual matter. We detect the mass, we just don't see any other characteristics of it.
Awesome video Angela, I really enjoyed it! (And happy birthday 🎉)
oh thats cool the main GNOME team is really close to where I live. I wonder if they let random people look at their smol magnetometers
yes live stream would be fun! I used to live stream to a bunch of nerds on YouTube for a good while. If there is anything that can help take the anxiety out of it for you am happy to help
I would like to make clear how very much fun and interesting it is when you go down into the weeds, its great if it ends up being 3h. You are a fun rambler, don't be afraid to ramble if your brain wants to go on a tangent!
Very much down for a Zelda video
Mama dark matter behind you
I'll be setting some money aside for some "Big honkin’ star boys" merch. I'm serious, Angela could commission an artist and get some funny cartoon stars with the words around them or something like that.
I got confused by a couple of things that seemed contradictory to me: * How come neutrinos can travel _faster_ than light in the water? It was my understanding that nothing travels faster than light... What am I getting wrong? * If dark matter particles don't interact electromagnetically (the property that makes them "dark"), how are the magnetometers going to detect them, if they look for magnetic perturbations...?
The speed which light travels changes through different mediums, so it travels slower in water than in a vacuum. Neutrinos are not very interactive with the water, so they are traveling faster than light will travel in water. Nothing can go faster than C, the speed of light in a vacuum.
Yay! It's my topic. Thanks to all the patrons who voted for it, and thanks to Dr. C for answering the question in a way that a community college dropout like me can understand. Happy birthmonth!
I really loved the video! You and Contra are the two creators whose patreon content I really look forward to every month.
The explanation was clear enough for me. I got a BS in Math and took physics as part of that. I also had a lot of friends in the physics department and would make them explain terms so I could at least follow the conversation. Does the video you did with The Binding Of Isaac mean nothing to you? Do you think it means nothing to us? Bring on the video where you discuss the pros and cons of popular scientists like Sagan and Hawking while you clear out a dungeon in Zelda!
Do you ever worry that physicists have become too comfortable with the notion that dark matter is unexplained? Like, its effects are so well measured and understood, that it can just be conjured mathematically / numerically / empirically to describe observations that people forget that they don't actually know what it is and maybe have given up trying to explain what it is? Not sure if I got that across properly but hopefully it made sense.
I just bet most physicists would be very keen to understand what Dark Matter actually is, primarily because it will add to the completeness of our knowledge. Uncovering such mysteries has to be one of the most rewarding things about being a scientist, surely?
do zelda video i mean i discovered you via binding of isaac so it wouldnt be too off. although i imagine it might not work its way harder to solve puzzles and talk physics.
“Big honkin’ star boys” is exactly the kind of technical jargon I love to sprinkle into casual conversation.
Is dark matter around us question: really tough to say. I’m not sure how uniform it is, how evenly distributed or how it behaves. My instinct is, yes, if it contributes to the mass of our galaxy, and we’re in a giant halo, it’s here, too.
I'd unironically love a zelda video, maybe as a livestream where you play it and answer physics questions.
Second this!
I think you present at an appropriate level of assumed knowledge. I took some 300-400 level physics in college 15 years ago but got Cs. If anything trips me up, I roll with it because I eventually get back on track. If you want to do something liveish, maybe just prepare some topics and riff with a form of text chat. What you have planned, what you are struggling to put too video and a couple physics questions/demos you prepared. On TV, a few feet from where I am working, I never notice those chair noises except while attention is called to them (and then I go back to not noticing them).
I followed fine, but I read physics papers for fun. The thing that's interesting about the superfluid proposal (at least IIRC) was that it made predictions about the behavior at the boundary which could - theoretically? - be measured.
Yes, absolutely. I increasingly think that we are facing the "nightmare scenario" and that the "particles" (quantum fields/waveforms) interact ONLY via gravity. Unless it's all really slow neutrinos. And Happy Birthday! While you're camping would you rather run into (a) a man, (2) a bear, or (iii) a man in a bear costume? Anybody know where I can rent a bear costume? RAAR!
October birthdays represent! 🎂 🎃 🙂
I probably need to think for some hours and read up enough to learn what a mass per unit area means in the context 3D space, but my gut reaction is to be a little surprised (because it's so high) at ~0.01% of the solar system matter being dark matter. That's a lot more than the earth, albeit spread over a much larger volume than the earth. But I don't know, maybe the density's too low to have any observable effect on orbits.
may be helpful to think of the solar system as a sphere-- all the baryons are spread out in a disk but that teeny tiny percentage of dark matter has a spherical distribution. So we don't even get close to all the dark matter in the solar system
This was fine, and I understood your point I think! Happy birthday for when it happens! I was also thinking maybe I could build a magnetometer for the GNOME project right when you said that you sort of do too! Though I'm probably better off funding the local university to do it.
But, we're here for the weeds ... aren't we?
There's a great topic, communal recreational drug use among 1970s Graduate Physics Students. How much and what kinds of drugs. Pot? Hallucinogens? Beer? Nitrous Oxide?
Okay, I don't know if this was a joke but there was a huge cocaine problem with physicists in the 80s. And there are tons of stories....I don't know if the public knows about it...
This video is perfect in its imperfection. I'm here a little bit for the sensation of struggling to understand and push back the limited boundaries of my physics. I was doing struggling like this 50 years ago reading Scientific American, more like wrestling with than just reading. There was a Quantum Chromodynamics article (sometime around early '70s?) wich I understood just enough to blow my mind and be in awe of how much I do not know. And also the feeling of "These physicist must be getting high and making stuff up." I think it was the first time Sci American tried this topic. I was 16 and had High School physics. Zero Math above Algebra. Anyway, I am here, a great fan of you and what you do, a little bit for that sensation of wrestling with my ignorance and squeezing out little drops of AHA!. Mostly I'm here to soak in you, your personality, the way you project yourself and let little glimpses of how you think out. This video is not a gleaming structure of organized, coherent perfect logic. It is exactly how it is supposed to be, a reflection of you and your personality. Thank You for your creativity and your work. I look forward to your next releases. Erica
I found the explanation very understandable, even though I have very little physics knowledge. Btw I would love a live stream! P.S. I left the Nobel prize video comment, I’m sorry I didn’t mean to shame you 😭
I thought the comment was very funny!
Loved this thanks! Don’t turn into a gaming channel ;) I have a question about the dark matter density — you said right at the end about the density getting higher the nearer the centre. At what rate does the dark matter fall into Sag A*? Can we estimate that? Can we measure the increase in mass of Sag A* (or another galaxy’s SMBH)? How long before ALL the dark matter in our halo ends up in Sag A*? Or is just a question like the density of dark matter in the Solar system, I.e yeah all that happens but at a tiny rate compared to the total amount of mass of the halo, it would take on order of 10^10^6 years? Thank you for a great video once again!
I think the answer to those questions would depend on the actual dark matter particle and what its properties were. But dark matter should not be falling into the black hole at some crazy rate because it's pretty cold and slow and supported by these huge structures. More likely the expansion of the universe will rip the dark matter off of our galaxy and every other galaxy until...the cold cold end.
Yes, there is dark matter in the solar system. How could there not be? Is there something special about inside the Galaxy or inside the Solar System?
Dark Matter? I'd say it does
Everyone is asking whether dark matter, but no one is asking how dark matter.