Dark Matter – Sixty Symbols


MEGHAN: Today, we’re going to talk about dark matter. PROF. COPELAND: Where is it?
Haha, it’s dark. You can’t see it. MEGHAN: We know there’s a lot of it out there, but it’s quite mysterious. PROF. MERRIFIELD: Astronomers kind of rely on light in order to figure out what’s going on in the universe, and things in the universe which inconveniently don’t give out any light, causes some problems because it’s very hard for us to actually infer very much about it apart from the fact that the material is there. MEGHAN: If I can introduce my prop here… PROF. COPELAND: About 95% of the total energy density in the universe is made of stuff that we don’t know. MEGHAN: Well, it’s dark obviously. It’s appropriate. It’s chocolate and it smells really good. If you imagine that this pie represents the entire matter and energy budget in the universe, and so the biggest slice of this pie is something mysterious – something really mysterious, called Dark Energy. Nearly three-quarters of our pie so that… Let’s say, about that much. So all of this bit here is this mysterious stuff called dark energy, but we don’t nearly have time to talk about that today So I’m going to leave this whole piece of the pie for the moment, okay? We’ll just stick it over here So what’s left is the stuff that has mass. This is all the matter in the universe. Now I’m going to divide this again. So this little slice of the pie here, which is supposed to represent about 4% of the total, this is all of the normal matter in the universe. This is all of the periodic table, so it’s all chemistry, all of biology… It’s everything that we can see, it’s all of the stuff that we’re made of, that the earth is made of, it’s all of the stars and galaxies and the gas and dust out there in the universe. Most of it is actually hydrogen, so an even tinier sliver is the stuff that makes, you know, our universe interesting. And what’s left, about… just about 23% or so of the universe is this dark matter – this mysterious stuff. We call it dark because it neither emits nor absorbs electromagnetic radiation so it doesn’t shine and neither does it cast a shadow. There’s almost certainly dark matter streaming through this room right now, but we have no way of knowing that it’s there And we call it matter because it has mass. And that’s very important because although it doesn’t interact through the rest of the normal forces it does interact with itself, and with normal matter and light, through gravity because it has mass. And that’s the only way that we can figure out that it’s out there in such large quantities. *nom* Haha, a little less of it now. PROF. MERRIFIELD: And so we can tell it’s there because we can see its gravitational influence on things we can actually see that the this dark matter was actually, you know, gravitating and pulling other stuff towards it. MEGHAN: And the first observation of that kind was made by an astronomer named Fritz Zwicky back in the 30s.
PROF. COPELAND: …who was looking at the rotation of galaxies. You know, they go around, and he was looking at the speed of the rotation as you move away from the center of the galaxy, so he’d pick some object that was emitting light and he’d look at how rapidly it was going around. MEGHAN: Think about the solar system for a moment. In our solar system, most of the mass is right in the middle – it’s made up of the sun. So the planets close to the sun, they feel a strong force of gravity. So Mercury for example is zipping around the sun while Neptune, further away, not feeling such a strong force of gravity, is just sort of pootling along very slowly. You’d expect something of the same to be happening in galaxies, because if you look at a galaxy – if you look at a spiral galaxy, it looks like it’s got this big concentration of stars in the middle and this disk that extends out even further. PROF. COPELAND: So you expect the speed to sort of rise up to a maximum and then drop off again. That’s what Newton would have told you, given what you could see. And what he noticed was that this… this speed went up to a maximum, and then stayed there. MEGHAN: They were going just as fast on the outside as they were in the inside. And what this meant was, again: What you see is not what you get. It’s not the whole story, there must be some other component. Part of this galaxy, providing enough mass to keep these stars moving. As an astronomer, I don’t know what the dark matter is. But what I can tell you is how much of it is out there, and what kind of structures it forms. And so, again it goes back to this key idea that, whatever these particles are, they interact gravitationally. BRADY: A bit of a misnomer calling it Dark Matter though, it seems like it’s almost transparent. PROF. COPELAND: Yeah, I hadn’t thought about that until I said the word transparent today. It’s dark only in that light doesn’t seem to interact with it. And so we’re inferring that there’s something there that we can’t see. The way you actually do perceive it is, light will go past it and as it goes past it, or through it, it will get bent. MEGHAN: In a sense, imagine yourself looking through a window. On a normal day, you just see right through the window you don’t even notice it’s there. On a rainy day, there might be raindrops on the window, and that kind of distorts your view, and that’s exactly what dark matter is doing. It’s distorting our view of the distant universe. Using data from the Hubble space telescope, the distortions in this case are so small you can’t actually see them, but by adding up the shapes that we observe of tens of thousands of tiny little galaxies we can measure this and reconstruct. And what my colleague Catherine Heymans has done to make this beautiful map is to use those distortions to figure out how much dark matter is in this particular part of the universe, and where it is, and we’ve color-coded it pink here. So you can see these big pink blobs of dark matter making up what is actually a super cluster of galaxies And what’s interesting is, if we look closely – and we’ve overlaid the actual pictures of galaxies here themselves, you see the galaxies are embedded in these blobs of dark matter. Dark Matter is of course invisible, so for the purposes of this picture, we’ve chosen just to color it pink so you can see it.
BRADY: Why can’t we find this stuff? If it’s everywhere; if it’s in this room; if it makes up such a big piece of the pie, why can’t we find it? MEGHAN: Well people are looking for it, and this is again a very interesting connection where people like myself who study the universe on very very large scales interact with people who are studying it on the small scales: The particle physicists. PROF. MERRIFIELD: As with most things in astronomy, as soon as you come up with some observation there’s a whole bunch of theoretical astrophysicists who say “I have an explanation for that!” And so there are a whole bunch of possible explanations out there for dark matter. The particle physicists for example would very much like it to be some form of exotic particle, so one of these sort of supersymmetric particles that comes out of their theories. MEGHAN: And so there are actual experiments that are trying to basically catch the dark matter particle in action, as it flies by. They’re really, really, really difficult. Because as I said, the best candidate that we… that the particle theory people have for dark matter, is something called a weakly interacting massive particle. So it’s not a normal type of atom. A good candidate for the dark matter particle would be the lightest supersymmetric particle, the Neutralino. So this is something that’s been thought of in theory but hasn’t been observed. And so these dark matter experiments, they usually take place deep underground because they have to be shielded from all sorts of radiation, from neutrons, that sort of thing. BRADY: What would happen if I drove my car into a big concentrated clump of dark matter? PROF: COPELAND: Into a big concentrated clump of dark matter… That would be… you’d… That’s a good question, that I’ve not thought of the answer to. PROF: MERRIFIELD: There are a whole bunch of experiments around the world, trying to detect this. For example if it is these weakly interacting massive particles, then they’re everywhere. They’re very small, each one, but there’s millions and millions of them, and they’re, you know, they’re passing through this room at this moment. And they’re very hard to detect because they don’t really interact very much with normal matter, but once in a while they do, and so there’s a whole bunch of experiments sort of scattered around the world, trying to detect these things and when one of them… IF and when one of them gets a detection, then we’ll have an answer tomorrow as to as to what the dark matter is – or at least we’ll have detected it. BRADY: Does it frustrate you, as someone who dreams of dark matter being discovered, to know that it’s here in this room? PROF. COPELAND: Yeah, it’s amazing ’cause it is everywhere, and then… it’s just so elusive. It won’t interact it all – barely, it just passes straight through you. And indeed, in order to try and find it, you have to go to areas where you increase the chance of it interacting with something, and so that typically is to go deep underground so that you can hide it from all the other type of signals, from particles that might mimic dark matter. MEGHAN: Because we think that dark matter makes up such a huge piece of the pie in our universe it means that we can actually run very very high… very very large computer simulations to predict what a dark matter universe would be. You have to figure out what the force of gravity is between that particle and every other particle and how that’s going to make it move. And then you do it again and again and again So yeah, It does take a large amount of computing power. So this is… this is a simulation of our universe. So what you’re seeing is a slice – a chunk of the universe at very early times, when the distribution of matter was very very smooth. And let’s fast-forward through the history of universe and see what happens. We have what’s called a hierarchical universe being built up. Small bits of dark matter merged together to form larger halos. That means the force of gravity is greater there and that acts as a well. And this… Dark matter tends to drain down along these filamentary structures and collect in these increasingly larger and larger halos. You can see we’ve got this beautiful, detailed picture of a universe that’s invisible to us. BRADY: What will happen to the man or woman who discovers dark matter? PROF. COPELAND: They’ll be going to Stockholm, I think, probably. MEGHAN: We’re coming across the road from the astronomy building, to the Cripps Computing Centre. So what we’re going to see is a supercomputer. And basically some of my colleagues across the road use this computer to simulate whole universes full of Dark Matter. I’ll have to put earplugs in for health and safety reasons, because we’re told that this is going to be very very loud [very very loud ventilation system noises] So it’s really loud in here and it’s really cold, because they have to keep pumping cold air through. And I’ve just learned that if the air conditioning fails, it would get so hot so quickly, with all these machines running that things would start to basically break down within an hour. I should say that this facility isn’t just used for astronomy. It’s also used across the University by other disciplines to do simulations on protein folding in cells and all sorts of other applications that require a large amount of computing power.

, , , ,

Post navigation

96 thoughts on “Dark Matter – Sixty Symbols

  1. Q : does the massive black hole in the center of our galaxy influence light & time as we experience it ?
    I bet it is because we are orbiting it. Which means, all our measurements & the things we can see will be distorted. How do we account for this ?

  2. A recent paper (2017Nov) claims that "scale invariance of empty space" might have the same effect as dark matter/energy. There are also ideas about Modified Newtonian Dynamics (MoND) which is another alternative to dark matter

  3. Most of Astronomy is not science, but a playground of speculation and hypothesis. This is evidenced by the fact that astronomers have no idea what "dark matter" is and even the most basic laws of physics don't appear to match observations. Astronomical research on the solar system is useful for humankind. Research beyond the solar system serves no useful purpose, other than intellectual masturbation by a small group of overfunded geeks It is time to put an end to this madness and stop all public funding of extra-solar system astronomy. If there are private funders who wish to continue to fund such research then let them do so.

  4. It bothers me that they call it dark MATTER. I haven’t heard any evidence that it has any substance. It really should be called something like the long-range gravitational anomaly.

  5. Wouldn’t it be something if dark matter is like ghosts? Cuz it’s something we can’t see yet it at times interacts with us

  6. I wonder if, in the dark matter universe, there are dark matter astro-physicists wondering where 1/4 of thier dark matter chocolate pie went…

  7. Since dark matter only seems to interact through gravity with bosonic matter, how does it fare near or inside black holes? According to the ratios discussed, dark holes should contain 5 times as much dark matter vs. regular. I never hear dark matter discussed in conjunction with black holes.

  8. Dark matter is the mass in the hypervolume of the proton and neutron. If the normal 3D volume of a proton is 1.00 then its hypervolume is 4.71. (The part of the proton's volume in 4D space. Yes, space is 4D, too. Welcome to the 21st century.) The total 3D volume of a proton then is 1.00+4.71=5.71. They think dark matter is 85% of matter. It is actually 4.71 / 5.71 =  82.48%, which is the ratio of hypervolume to total volume. The proton and all other elementary particles are 4D objects, not 3D as has been believed for over 2000 years. See the  video, "The proton is a four dimensional object", for proof  that the proton is anyway. Why the mass in the hypervolume is expressed gravitationally only starting at thousands of light years distance is unknown physics. This is a new unexplained phenomena, and, very confusing as are all new phenomena before they are explained.

  9. One of the speakers are talking very fast, like he is coding a telegram.!

    Explaining some thing to public,requires speaking normally, or even, slowly.!

  10. Wait . . . Dark matter would not be spread about the universe. It, like all other resident mass, would tend to collect in black holes at the center of galaxies, would it not? But the math is already worked out for these and there's no room for Dark Matter-right?

  11. on this day Monday 12th of February I unified QUANTUM MECHANICS AND GENERAL RELATIVITY! now can someone please tell me who requires the answer and what do i get it to them.

  12. The bigger question in this case should be how could there be any form of matter which we cannot see or anything that light cannot interact with. Our understanding of light is very limited and the definition is very convoluted as it is and getting involved in things like this makes everything more complicated. Dark Matter simply could be everything that we have in Space other than from things that we can see and this should explain why Outer Space is dark, given that we accept that Dark Matter does not interact with light. But all this is very confusing for me, it could be that many of our theories are wrong.

  13. Is it possible that dark matter and dark energy are really the stuff of the other spatial dimension and that we humans are simply a part of some kind of precipitate out of the other dimensions? An analogy might be like the snow that precipitates out of the winter sky. The humid air is invisible to us, but the snow that falls is 3 dimensional. This might be a particularly naive question, but it would answer a lot of questions.

  14. Do they have galaxy full of gold with little bit something on edge. Maybe pure radioactive materials are dark matter.

  15. I think Dark Matter is not a physical particle, but a region or regions of permanently deformed space time. Ie if the earth creates a gravity "well" in spacetime , this is what we call gravity. Now take the earth away but keep the well.

    Whats left is the determinant imprint of a massive body that has the characteristics of mass without the matter. Hence A: it will attract other mass and other dark matter or " gravity wells" B: it will cause light to be bent when passing by/through it C: It will have no Charge, strong or weak interaction, etc or any other characteristics of the 4 fundamental forces other than gravity.

    Think about space time as a fabric that can be permanently damaged or changed in various areas. What does this who knows, but instead of thinking that spacetime can only be deformed by mass or slowly stretched by the expansion of the universe, think more of a highway with worn out grooves in the asphalt where the tires have eroded it. Mass or matter being the cars, the road being space time. Ie space time is inelastic, or non uniform locally.

  16. So if there's dark matter all around us, going right through us like Dr Gray says, how much effect is it having on, say, the orbit of the Moon around the Earth? If the solar system obeys Newtonian mechanics but a galaxy does not, then surely that means that there must be very little dark matter within the confines of our solar system, it's all in interstellar space.

  17. Couldn't be that Dark Matter doesn't "exist" at all? I mean could it be that just the gravity force is seeping into our 4 dimensional membrane from higher dimensions? i'm asking i'm not a physicist!^^

  18. What is dark matter is that they are extremely dense material traveling at bullet speeds. Slicing the entire galaxy they always cut through galaxies.

  19. Doesn't this mean that the measured mass of the Sun should be a factor of 20 higher than the estimates of the amount of hydrogen and helium than we "see"?

  20. Alternate history: If there were significant densities of dark matter in our Solar System, Newton's equations would not have worked, and it would have been virtually impossible for astronomers to tell why. Would there still have been a Scientific Revolution?

    Something else to ponder: if dark matter is at least as interesting (in terms of mutual interactions, ability to form compounds, and so on) as visible matter, there could be vast ecosystems of invisible (and to us, incorporeal) life.

    That is, assuming that someone doesn't rearrange the equations in some clever new way so that it turns out "dark matter" and "dark energy" were mistaken epicycles used to patch holes in a limited understanding of physics. 🙂

  21. How can it 'stream through the room' if it clumps ,like normal matter ,into lumps capable of gravitational lensing? If gravity was affected by a invisible lump surely you would feel it at close quarters???

  22. If gas clumps by gravity , so would darkmatter , unless there is a force that keeps the darkmatter separate, but if that is the case , how would it ever clump into somethkng large enough to lens???

  23. There's something ironic about explaining dark matter to people who you apparently believe need a visual aid for understanding 3/4 😛

  24. Dark matter is a HOAX because your cant figure out the math for galaxies that have a gravity and TIME that is NOT the same as ours.

  25. so is Einstein's theory of gravity "The Theory" i.e. "The Truth" and there is no other way gravity could be imagined because Einstein has explained everything that there is to it? At least at the macroscopic level?

  26. This doesn't really seem to make sense. If dark matter were really just particles (which only react with gravity) floating around, what's limiting their density? Or might they just accrete until eventually forming a black hole? Shouldn't everything be getting heavier all the time if this is how it works? It must be that they bounce off each other to keep that from happening, but they shouldn't be able to bounce out of a black hole, right – so shouldn't black holes continuously accrete mass in that way?

  27. "What's dark matter?"
    -"No clue. But we see some stuff that doesn't fit with our maths, so we came up with this concept to make our maths fit our observations."

  28. 5:30 "Dark matter is distorting our view." It surely is when they come up with horseshit like dark matter and dark energy just to make their sums add up.

  29. perhaps there is a property of space-time we do not know on large scales…. it doesn't have to be hidden mass… but that doesn't mean we shouldn't stop looking for it.

  30. Comparing this; to what i would label “a normal job,” i’m left wondering who pays these people to worry about this nonsense.

  31. The electric universe explains this simply and rationally.
    Black matter and black energy are simply "plug factors", to make the standard theory seem to work.
    It doesn't.

  32. Proof of Dark Matter can be found by gazing up at the stars in the night sky. Dark Matter is the media which carries the energy wave of starlight. Just as the energy of an earthquake which can travel thousands of miles across an ocean to form a tsunami, lightwaves also require a media to propagate. Without Dark Matter the night sky would appear to be nothing but empty blackness. Dark Matter is the ocean of the Universe.

  33. How can one reasonably compare the laws governing the solar system to those ruling the movements of billions of stars in a galaxy? In my opinion the faster than expected motion of stars in the galaxies can have so many different reasons ( one is : do we know how should stars move in a complex system like a galaxy? )than the existence of DM and same applies to gravitational lending.

  34. Dark matter is the darkness shield, like a curtain, the mechanical elves use to conceal themselves as they constantly work with their little space hammers to fine tune the universe and to tug on the strings connected to all the cosmic bodies.

  35. what if dark matter and dark energy didn't existed , would it had affected planets stars and even our solar system or even our earth

  36. There is no such thing as an entire energy/mass budget of "the universe". Also we cannot really talk about a universe since it would have borders…and there are none the more we look farther and deeper (scale dimension up and down).

Leave a Reply

Your email address will not be published. Required fields are marked *