Three Mind-Blowing Facts about Magnetism - Ask a Spaceman!

I'm about to tell you three things about magnetic fields that I'm I'm guessing I'm just throwing this out here that you probably didn't know and these are three these are like three surprising tricks of magnetic fields trick number one how can a black hole you know black holes how could a black hole have a magnetic field black holes the very definition of a black hole is that nothing can come out not even light which is electromagnetic radiation so how can a black hole have a magnetic field if nothing can come out well here's the thing this is the exact same question as asking how can a black hole have mass how can black hole how could a black hole you emanate the force of gravity if nothing can come out of the black hole how can a black hole emanate the force of magnetism if nothing can come out of the black hole here's the thing when you're in the vicinity of a black hole and you're feeling its mass and you're feeling its magnetic field you're not feeling the mass or magnetic field of the black hole itself you're feeling the mass in the magnetic field of the ghost of its parent star remember what happens when you fall into a black hole if you were to fall into a black hole you would just sail through the event horizon then you would die horribly bla bla bla and it's all hilarious but me watching you fall into the black hole sees a different picture I never get to watch you cross the event horizon that boundary that point of no-return you never cross it from my perspective you just approach it approach it approach it approach you approach it and you get slower and slower and slower more and more redshifted slower slower more and more redshifted I never see you actually cross this is the exact same thing that happens to the star itself that becomes a black hole once that event horizon forms there is material falling in continuing to fall in and it does fall in the black hole grows everything but from our perspective it appears glued onto the surface it appears glued onto the surface and it still has an effect on the outside world because it's not through the black hole yet and we feel the mass that shadow of the Dead star we feel its magnetic field because that star was made of charges electric charges that were spinning around really fast had a great magnetic field that magnetic field persists to the present day this is one of the consequences of this weird thing where special relativity and general relativity tell you that different observers have different perspectives one of the extreme examples of this is around a black hole now the second weird thing about magnetic fields is this isn't the surprising part that there's no such thing as a North Magnetic Pole or a South Magnetic Pole by itself if you have a magnet you get north and south together you chop that thing in half you don't get a North Pole over here in a South Pole very you just get a tiny north-south thing magnet over here in a tiny north-south magnet here you keep chopping it up you just keep making these pairs of north and south there is no reason why our universe can't have isolated magnetic charges what we call the mono pulls a single North Pole a single South Pole there's nothing there's nothing for baiting it in our universe we simply don't observe it and we haven't observed it for so long that it's baked into our equations of electromagnetism itself they just state no magnetic monopoles in our universe but that's that's like an assumption based on observation so all the magnetic fields that we see in the universe are generated by moving charges not by having a monopole existing independently but something interesting happens if there was at least one magnetic monopole in our universe just one if you're just played the mind game this is just a thought experiment life let's just have fun this was first cooked up by Paul Dirac one of the founders of quantum mechanics he was looking at a system and playing around and say okay let's say you have a magnetic monopole a north-north charge right there and then you bring around an electric charge say a positive charge right here you ask what do they do turns out they start orbiting around each other they start spending there is an angular momentum associated with that system you know momentum going in a circle that's no big deal what he found surprising is that this effect doesn't matter how far away these particles are they could be over here and they'll rotate they could be like this out of frame of my camera you know do this they could be on the other side of the Milky Way galaxy same deal okay that's kind of cool but we know from quantum mechanics that angular momentum is quantized angular momentum momentum going in a circle comes in discrete chunks you can only have one package of angular momentum or two packages or three or four or five million and five million and one and five million in - you can't five million and a half you can't have six and three-quarters you can't have I'm sure you can imagine other fractions you can't have fractions of this fundamental unit of angular momentum which we call Planck's constant so these two particles the north charge and the positive charge orbit each other there is angular momentum there a fundamental limit to the angular momentum due to the quantization of nature itself this means that the electric charge must also be quantized this is an explanation for why electric charge is also quantized in our universe you can only have one unit of electric charge or two or three or five dozen you can't have half you can't have three quarters and I'm ignoring the quarks for now if you're interested in the physics course that's another episode but it's the exact same argument applies electric charge in our universes is quantized comes in screed packets again there is no explanation for that there's no reason for that we simply observe it in nature but if one just one magnetic monopole existing in our universe that would be the reason for the quantization of electric charge which that's a pretty powerful trick but that's not all magnetic fields have three surprising properties I've only got two here's the last one if you take a charge an electric charge it has an electric field in you're really bored what if you start running by it though what if you start you know chugging along and you're watching it all right from your perspective you're not the one who's moving everything else in the universe is the one that's doing the moving right so from your perspective you're staying still and the electric charge is doing this but what do moving electric charges do they create magnetic fields so if you're staying still you see an electric field if you're moving you see a magnetic field are you looking at fundamentally an electric field or a magnetic field yes you're looking at both at the same time it is impossible to think of electric fields and magnetic fields as being separate things they must be united under a common framework that we call electromagnetism as discovered by James Clerk Maxwell in the mid-1800s what does this sound like two things that appear to be different by really just two sides of the same inner woven coin does this sound like space-time does this sound like energy and mass I hope it does because it's supposed to because electricity and magnetism were the precursor for general special relativity they were the precursor for special relativity almost said general relativity general tivity comes from special relativity so I wasn't technically wrong but just slightly confusing so I'm gonna leave it in I'm not gonna even edit that the unity of electricity and magnetism led Albert Einstein to flesh out to figure out special relativity it was Wu is an examination of the interlocking nature of electricity and magnetism that he was able to uncover the connectedness between space and time and energy and mass and all the special relativity so as thinks to magnetic fields it's thanks to magnetic fields in the impossibility of separating them from electric fields and considering them as separate things that we have a cornerstone of modern physics so there you go magnetic fields they led us down the road of special relativity they have some surprising impossible possibly very interesting explanations for a fundamental charge of on the electron and they can come out of a black hole even though nothing can come out of a black hole so there you go three things three reasons why magnetic fields are the best fields thank you so much I hope you enjoyed this video don't forget to Like and subscribe and make sure notifications are turned on so you know when I come live and you can go to patreon.com/scishow ver there I don't really remember where you can help keep these videos coming thanks so much for watching

Channel: Dr. Paul M. Sutter

Views: 63,856

Keywords: space, cosmos, universe, astronomy, physics, astrophysics, cosmology, science, magnetism, magnets, special relativity, quantum mechanics, quantization, charge, electric charge, black holes

Id: 7cozCZAhsE0

Length: 10min 22sec (622 seconds)

Published: Wed Sep 12 2018