物理學家回答網路提問！光是波還是粒子？ 漫威濫用量子物理學？ 特殊相對論特殊在哪？ ｜名人專業問答｜GQ Taiwan

I'm Jeffrey hasbun I'm a physicist let's answer some questions off the internet this is physics [Music] support at Pizazz 91 asks how do black holes influence the SpaceTime around them anything that's massive will bend SpaceTime so if I think about this sheet of elastic as being SpaceTime with nothing in it as soon as I put something that has any mass in there it bends SpaceTime around it if I then take something really small like this marble and give it a little bit of umph it'll orbit around that object and it's that following curved SpaceTime is why the Earth moves around the Sun so if I have a really big object and I look at what that looks like in SpaceTime that bends it even more the key with a black hole is making something that's really really dense and as I increase that density that stretches the SpaceTime further and further and further down so much that light can't escape that curvature anymore and that's what we call a black hole at pedals for Jack asks wait what's SpaceTime SpaceTime is the thing that we live in it is four dimensions three dimensions of space and adding to that the dimension of time it's what we're moving through as we sit still it's what we're moving through as we walk through our house Afeni smack asks how do you split an atom what you're really doing is you're splitting the nucleus and let's say this is the nucleus of a uranium atom and what you do do is you shoot another particle at it usually a neutron really really fast and when you shoot it at the nucleus the nucleus breaks into pieces into a few different pieces that are smaller nuclei and when you do that it also as you can see releases a lot of energy and that's where the first nuclear bombs came from and that's where the energy we get from nuclear power comes from user aier 8203 asks if the sun just suddenly disappeared it would take us 8 minutes to find out but does Earth still orbit where the sun was or will it go out of the orbit immediately after it disappeared the answer is it's going to keep moving around the Sun for another 8 minutes we don't know here on Earth that the sun disappeared because it takes 8 minutes for the light to get to us from the Sun it also takes 8 minutes for any changes in gravity to get from the Sun to us at Mike bian asks hasn't read a goddamn thing about physics since high school hey did you hear about the gravitational wave I have heard about the gravitational waves and I helped publish some of the recent results about gravitational waves in case you haven't been paying attention gravitational waves are these expansions and contractions of SpaceTime that are traveling through SpaceTime at us from super massive black holes at the centers of far away galaxies one of the really neat things about gravitational waves is they pass unimpeded through the universe we can actually get closer to the Big Bang using observations of GRA gravitational waves so they're going to teach us all kinds of neat stuff about the early Universe at only 166 asks one question how do you detect gravitational waves in SpaceTime the first way we detected gravitational waves a few years ago was using lasers in big vacuum tubes and you split a laser you shoot it down two tubes and you keep track of how far apart the mirrors are using the lasers to tell you the distance between the mirrors that's called ligo the second way that we've learned to detect gravitational waves is by using these exotic Stars called pulsars they are really fast spinning stars that pulse every time they come into our line of sight we watch those pulses over time if the pulses arrive a little bit later or a little bit earlier we can attribute that to the expansion and contraction of SpaceTime between us and those Stars I'm part of a collaboration that looks at almost 70 of these stars in all different directions and we've been monitoring it for almost 20 years at thek hatib asks I'm genuinely paying you $1,000 if you answer this right is light a wave or a particle the answer is that light is both a wave and a particle we've known the wav like properties of light for a long time there's a classic experiment called the Young's double slit experiment let's show it to you right now let's take down the lights we're going to take a laser pointer here which is not how the original experiment was done I'm just going to take this plate that has a little tiny slit in it and point the laser through it and what happens is it splits the light into two different waves and those waves are a little separated from each other they're not quite matched up because two different waves are meeting up with each other and this is what we call interfering and that's what gives us that pattern there's actually two waves hitting there and they're constructively interfering so the black spots are actually the same as what what you get in noise cancelling headphones one of the waves is cancelling out the other wave and only a wave behaves like this lights please light is actually something bigger than a wave or a particle it's something we call a Quantum field and that Quantum field has particle like characteristics and wav like characteristics and we can measure both so I think you owe me a th000 bucks dude at Dr zgc Disney asks what's the difference between fision and fusion anyway do you want to go fision with me I don't want to be anywhere near where fision is happening fision is where you take a nucleus that's really big of an atom and you break it into pieces Fusion is where you take pieces of atoms and you push them together to make something bigger Fusion is what happens in the sun where really small nuclei come together and that is a huge explosion and we've been trying to build something like that on Earth to make energy we haven't been able to to figure out how to control it yet shivanu 21212 asks how will the universe end the universe will end in the heat death of the universe which just means that over time the universe is expanding and all of the light that we know about is going to get degraded and absorbed by black holes it just gets really cold and really dark we won't be able to see anything in the distance and just nothing the heat death of the universe is not something to worry about because it's going to happen 40 to 50 billion years in the future and we're only about 14 billion years from the beginning of the universe at clown Prince Charlie asks wait are black holes slw wormholes actually spheres watching Interstellar black holes are pretty much perfect spheres if they're spinning they are a little bit more expanded around their equator where they're spinning than at their poles but pretty much spheres so in that classic image from Interstellar you see this pretty much spherical black hole at the center and then you see all of this light which is the light from the other side of the black hole getting bent around it and that disc that you see across the front that tells you that the black hole is actually spinning and every black hole that we know of is spinning like every other star in the universe at 52x Max asks what's so special about special relativity well that's relative Einstein probably special relativity is special for a few reasons number one it gives us a universal speed limit which is the speed of light nothing can go faster than the speed of light and that's unique to Einstein he figured this out in 1905 and no one had really thought that there was any kind of universal speed limit a couple other things that are really special about special relativity are that it tells you if you're moving close to the speed of light time dilates it gets longer so if you're moving really fast you experience time more slowly than someone who's not moving really fast at Cowboy vard asks can someone explain the twin paradox to me in simple terms you have two twins both on Earth one of the twins decides to be an astronaut she takes off in a spaceship going super fast almost the speed of light it takes her 50 years to go out to a star and come back when the astronaut comes back the twin that remained she's 50 years older the other twin might only be 20 years old depending on how fast she was going and so it's the person in the rocket that will see time move more slowly and will only age 20 years at AES Force One asks the speed of light as constant is falsehood what's the speed of light in water slower the speed of light as a constant is not a falsehood we have a glass of water and I'm going to put this pencil in there and when I put the pencil in the pencil looks bent the light that's coming out that you're seeing is bent that bending comes from the fact that as the light hits it at some angle it sort of veers in that direction the light's interacting with the water it's getting absorbed and reemitted it's seeing a little bit longer paths as it gets scattered and it's that that makes the light look like it's bent those interaction ACS take a little bit of time and that's why we say that it's effectively moving more slowly between one interaction and the next the speed of light is the speed of light at Aquarius donek asks the question is how does time dilation work long story short time dilation is the fact that when you're moving really close to the speed of light time passes more slowly it's pretty simple to write down the time that passes for someone who's moving at some speed is proportional to how time is passing for someone who's not moving at that speed and there's this funky square root down here and what matters is the comparison of how fast that person's moving that's what V is as compared to the speed of light and in that line there and as you go faster and faster and faster that factor of delta T Prime gets longer and longer and longer so time is passing more and more slowly when you get to the speed of light time no longer passes at Neil Cameron 78 asks are black holes really wormholes or are wormholes really black holes eh eh # science we know black holes exist we can see evidence for them out there we've seen light around these black holes and what it looks like we've seen the silhouette of a black hole wormholes are a shortcut through SpaceTime from one place to another the first idea of a wormhole is something called an Einstein Rosen Bridge it would take moving faster than the speed of light to travel through and we have no evidence whatsoever that wormholes exist some physicists have posited that if we use some of the special characteristics of quantum field theory that maybe we can create tiny tiny little wormholes that we can send a signal through from one place in SpaceTime to another and while these have been successful as thought experiments and successful as computer simulations it's not yet been seen in the real world in a real life experiment at Matt P1 1949 asks you think time travel is possible under current physics understanding no probably not at least not from what we understand right now there's a couple of ways to think about how we might travel in time one way is using a wormhole some physicists have done this thought experiment and written down all of the pieces you would need so you build a wormhole that somehow changes and tunnels through SpaceTime back into the past you write down the math for what that Wormhole looks like the kind of matter that you would need to hold that Wormhole open does doesn't exist in our current understanding of physics the type of matter that you would need to hold a wormhole open is called exotic matter things like negative energy density which what does that mean it means like thinking of something with negative Mass so I don't know if we're going to be building a time machine anytime soon unless we can figure out how to find and make this exotic matter Brad Alexandre asks is there anything infinite in the real world or is infinity just a concept in our minds Infinity is not just a concept in our minds the most important Infinity that I study is that the universe is infinite so that's a great example of something that's infinite we use Infinities all the time when we're making predictions in physics and it turns out that the size of the universe is infinite the amount of time the universe will be around is also infinite at one day wellbe okay asks quick question does anybody know the difference between particle physics and quantum physics please particle physics is a small part of quantum physics and quantum physics is the area are of physics that really studies small stuff and the interactions on really really small scales but particle physics focuses on the particles that make up atoms the fundamental particles that make up everything around us at Cipher 707 asks I thought quantum physics was a fanfic absolutely not quantum physics is how the world works but you have to look at a really small scale to understand what's going on if I throw a ball up in the air it comes down back into my hand that's classical physics quantum physics acts in surprising ways so instead of having pure predictions about what's going to happen at a Quantum level we just get probabilities there's a 50% chance that this thing is going to happen a 20% chance that this other thing is going to happen if you watch a lot of Marvel movies I could see why you'd think it was fanfic because it gets used anytime you don't know how to explain the science that you want to do at Raven biter asks lecturer just asked what Heisenberg contributed to physics and loads of people answered crystal meth that's a different Heisenberg the Heisenberg that we know is a very famous Quantum physicist he worked with the German government during World War II but he's really well known for being one of the people who figured out all of these rules of quantum mechanics really early on he came up with something called the uncertainty principle basically if I know one aspect of a particle like where it is I can't know how fast it's moving very well or if I know how fast it's moving I can't know where it is at Tim amberie asks I just learned about quantum entanglement and I'm shook how can two particles be so connected that they affect each other even when they're light years apart is this the secret to long-distance relationships # Quantum love two particles Lighty years apart can absolutely be connected if we've set them up in a entangled State and what that means is we take two particles where the measurement has something to do with chance so if I roll this dice whatever value I get on that face I'm going to get the same value on the other dice if that's how I've set up the entangled system and these two particles can be very very far apart from each other and this is just how nature works the weird part about this is the chance that no how matter how I roll the dice whatever it lands on the other dice will land on the same exact value this is just a fundamental way about how the universe works at UTB asks what the hell does the large hyron collider do anyways the Large Hadron Collider is the largest particle accelerator in the world world it is a huge 10 km Circle in Switzerland where we take two streams of protons protons are a kind of hadron hadrons are really heavy particles takes those two streams of protons and aligns them just right they're going almost the speed of light not quite but almost a speed light and smashes them into each other the faster you can get those protons to go the more stuff comes out of that explosion when you smash them together we're making new particles that we haven't seen before they're part of nature but they take so much energy to make that they haven't been around since the big bang when the universe was really tiny and really really energetic so not only are we learning about these fundamental forces we're also learning about physics right at the beginning of our universe at physics in history asks is string theory really a dead end no it's not a dead end string theory is a theory that says instead of the fundamental pieces of the universe being particles they're strings and these strings can vibrate in different ways you can have strings that are long you can have strings that in loops and not only does it describe all of particle physics and quantum mechanics some pieces of this actually predict what quantum gravity would look like gravity on a really small scale which is not a theory that we have right now so those are all the questions for today thanks for such insightful questions thanks for watching physics support

Channel: GQ Taiwan

Views: 54,815

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Id: PR_gKUpgr54

Length: 16min 21sec (981 seconds)

Published: Sat Dec 16 2023