Physicist Jeffrey Hazboun visits WIRED to answer the internet's swirling questions about physics. How does one split an atom? Is light a wave or a particle...or both? How soon will the universe end? Is time travel is possible given physicists' current understanding?
Director: Lisandro Perez-Rey
Director of Photography: AJ Young
Editor: Marcus Niehaus
Talent: Jeffrey Hazboun
Creative Producer: Justin Wolfson
Line Producer: Joseph Buscemi
Associate Producer: Paul Gulyas
Production Manager: Peter Brunette
Production and Equipment Manager: Kevin Balash
Casting Producer: Vanessa Brown
Camera Operator: Lucas Vilicich
Sound Mixer: Kara Johnson
Production Assistant: Fernando Barajas
Post Production Supervisor: Alexa Deutsch
Post Production Coordinator: Ian Bryant
Supervising Editor: Doug Larsen
Additional Editor: Paul Tael
Assistant Editor: Billy Ward
Director: Lisandro Perez-Rey
Director of Photography: AJ Young
Editor: Marcus Niehaus
Talent: Jeffrey Hazboun
Creative Producer: Justin Wolfson
Line Producer: Joseph Buscemi
Associate Producer: Paul Gulyas
Production Manager: Peter Brunette
Production and Equipment Manager: Kevin Balash
Casting Producer: Vanessa Brown
Camera Operator: Lucas Vilicich
Sound Mixer: Kara Johnson
Production Assistant: Fernando Barajas
Post Production Supervisor: Alexa Deutsch
Post Production Coordinator: Ian Bryant
Supervising Editor: Doug Larsen
Additional Editor: Paul Tael
Assistant Editor: Billy Ward
Category
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TechTranscript
00:00 I'm Jeffrey Hasbun, I'm a physicist.
00:02 Let's answer some questions off the internet.
00:04 This is physics support.
00:06 (upbeat music)
00:09 @Pizzaz91 asks, how do black holes influence
00:15 the space time around them?
00:16 Anything that's massive will bend space time.
00:19 So if I think about this sheet of elastic
00:22 as being space time with nothing in it,
00:24 soon as I put something that has any mass in there,
00:26 it bends space time around it.
00:28 If I then take something really small like this marble
00:31 and give it a little bit of oomph,
00:33 it'll orbit around that object.
00:35 And it's that following curved space time
00:37 is why the earth moves around the sun.
00:40 So if I have a really big object
00:42 and I look at what that looks like in space time,
00:45 that bends it even more.
00:47 The key with a black hole is making something
00:49 that's really, really dense.
00:51 And as I increase that density,
00:52 that stretches this space time further and further
00:55 and further down so much that light can't escape
00:58 that curvature anymore.
01:00 And that's what we call a black hole.
01:01 @PetalsforJack asks, wait, what's space time?
01:05 Space time is the thing that we live in.
01:08 It is four dimensions, three dimensions of space
01:11 and adding to that the dimension of time.
01:13 It's what we're moving through as we sit still.
01:16 It's what we're moving through as we walk through our house.
01:19 @FrivintySmacks asks, how do you split an atom?
01:23 What you're really doing is you're splitting the nucleus.
01:25 And let's say this is the nucleus of a uranium atom.
01:29 And what you do is you shoot another particle at it,
01:32 usually a neutron, really, really fast.
01:35 And when you shoot it at the nucleus,
01:37 the nucleus breaks into pieces,
01:39 into a few different pieces that are smaller nuclei.
01:44 And when you do that, it also, as you can see,
01:46 releases a lot of energy.
01:48 And that's where the first nuclear bombs came from.
01:50 And that's where the energy we get from nuclear power
01:53 comes from.
01:54 @userAlier8203 asks, if the sun just suddenly disappeared,
01:58 it would take us eight minutes to find out,
02:00 but does earth still orbit where the sun was,
02:03 or will it go out of the orbit
02:04 immediately after it disappeared?
02:06 The answer is it's gonna keep moving around the sun
02:09 for another eight minutes.
02:10 We don't know here on earth that the sun disappeared
02:14 because it takes eight minutes for the light
02:16 to get to us from the sun.
02:17 It also takes eight minutes for any changes in gravity
02:21 to get from the sun to us.
02:23 @MikeBianchi asks, hasn't read a goddamn thing
02:26 about physics since high school.
02:27 Hey, did you hear about the gravitational waves?
02:30 I have heard about the gravitational waves,
02:31 and I helped publish some of the recent results
02:34 about gravitational waves.
02:35 In case you haven't been paying attention,
02:37 gravitational waves are these expansions
02:40 and contractions of space-time
02:42 that are traveling through space-time at us
02:44 from super massive black holes
02:47 at the centers of faraway galaxies.
02:49 One of the really neat things about gravitational waves
02:52 is they pass unimpeded through the universe.
02:55 We can actually get closer to the Big Bang
02:58 using observations of gravitational waves.
03:00 So they're gonna teach us all kinds of neat stuff
03:03 about the early universe.
03:04 @Only166 asks, one question,
03:08 how do you detect gravitational waves in space-time?
03:12 The first way we detected gravitational waves
03:14 a few years ago was using lasers in big vacuum tubes.
03:18 And you split a laser, you shoot it down two tubes,
03:21 and you keep track of how far apart the mirrors are
03:24 using the lasers to tell you the distance
03:27 between the mirrors.
03:28 That's called LIGO.
03:29 The second way that we've learned
03:31 to detect gravitational waves
03:33 is by using these exotic stars called pulsars.
03:37 They are really fast spinning stars
03:40 that pulse every time they come into our line of sight.
03:42 We watch those pulses over time.
03:44 If the pulses arrive a little bit later
03:47 or a little bit earlier,
03:48 we can attribute that to the expansion
03:51 and contraction of space-time between us and those stars.
03:54 I'm part of a collaboration that looks at
03:56 almost 70 of these stars in all different directions,
03:59 and we've been monitoring it for almost 20 years.
04:02 @VatericHatib asks, I'm genuinely paying you $1,000
04:06 if you answer this right.
04:07 Is light a wave or a particle?
04:10 The answer is that light is both a wave and a particle.
04:13 We've known the wave-like properties of light
04:16 for a long time.
04:17 There's a classic experiment
04:18 called the Young's Double Slit Experiment.
04:20 Let's show it to you right now.
04:22 Let's take down the lights.
04:23 We're gonna take a laser pointer here,
04:28 which is not how the original experiment was done.
04:30 I'm just gonna take this plate
04:32 that has a little tiny slit in it
04:34 and point the laser through it.
04:36 And what happens is it splits the light
04:38 into two different waves.
04:40 And those waves are a little separated from each other.
04:43 They're not quite matched up
04:45 because two different waves are meeting up with each other,
04:49 and this is what we call interfering.
04:51 And that's what gives us that pattern.
04:52 There's actually two waves hitting there
04:54 and they're constructively interfering.
04:56 So the black spots are actually the same
04:59 as what you get in noise-canceling headphones.
05:01 One of the waves is canceling out the other wave,
05:04 and only a wave behaves like this.
05:07 Lights, please.
05:08 Light is actually something bigger
05:12 than a wave or a particle.
05:14 It's something we call a quantum field,
05:15 and that quantum field has particle-like characteristics
05:20 and wave-like characteristics.
05:22 And we can measure both.
05:23 So I think you owe me a thousand bucks, dude.
05:25 @DrZGCDisney asks,
05:28 "What's the difference between fission and fusion anyway?
05:31 Do you wanna go fission with me?"
05:34 I don't wanna be anywhere near where fission is happening.
05:37 Fission is where you take a nucleus
05:39 that's really big of an atom and you break it into pieces.
05:43 Fusion is where you take pieces of atoms
05:46 and you push them together to make something bigger.
05:48 Fusion is what happens in the sun
05:50 where really small nuclei come together,
05:53 and that is a huge explosion.
05:55 And we've been trying to build something like that on Earth
05:57 to make energy.
05:58 We haven't been able to figure out how to control it yet.
06:00 @Shivanshu21212 asks, "How will the universe end?"
06:05 The universe will end in the heat death of the universe,
06:08 which just means that over time,
06:10 the universe is expanding and all of the light
06:13 that we know about is going to get degraded
06:15 and absorbed by black holes.
06:17 It just gets really cold and really dark.
06:20 We won't be able to see anything in the distance
06:23 and just nothing.
06:24 The heat death of the universe
06:25 is not something to worry about
06:27 because it's gonna happen 40 to 50 billion years
06:30 in the future, and we're only about 14 billion years
06:33 from the beginning of the universe.
06:34 @ClownPrinceCharlie asks, "Wait, are black holes/wormholes
06:39 actually spheres?"
06:40 Watching "Interstellar."
06:41 Black holes are pretty much perfect spheres.
06:44 If they're spinning, they are a little bit more expanded
06:48 around their equator where they're spinning
06:50 than at their poles, but pretty much spheres.
06:53 So in that classic image from "Interstellar,"
06:55 you see this pretty much spherical black hole at the center,
06:59 and then you see all of this light,
07:00 which is the light from the other side of the black hole
07:02 getting bent around it.
07:04 And that disc that you see across the front,
07:07 that tells you that the black hole's actually spinning.
07:09 And every black hole that we know of is spinning,
07:12 like every other star in the universe.
07:15 @52xmax asks, "What's so special about special relativity?"
07:19 Well, that's relative.
07:21 Einstein, probably.
07:22 Special relativity is special for a few reasons.
07:25 Number one, it gives us a universal speed limit,
07:27 which is the speed of light.
07:29 Nothing can go faster than the speed of light.
07:31 And that's unique to Einstein.
07:32 He figured this out in 1905,
07:34 and no one had really thought
07:36 that there was any kind of universal speed limit.
07:38 Couple other things that are really special
07:40 about special relativity are that it tells you
07:42 if you're moving close to the speed of light,
07:44 time dilates, it gets longer.
07:46 So if you're moving really fast,
07:48 you experience time more slowly
07:49 than someone who's not moving really fast.
07:51 @cowboyvard asks, "Can someone explain the twin paradox
07:55 "to me in simple terms?"
07:57 You have two twins, both on Earth.
07:59 One of the twins decides to be an astronaut.
08:01 She takes off in a spaceship going super fast,
08:04 almost the speed of light.
08:05 It takes her 50 years to go out to a star and come back.
08:08 When the astronaut comes back,
08:10 the twin that remained, she's 50 years older.
08:12 The other twin might only be 20 years old,
08:15 depending on how fast she was going.
08:17 And so it's the person in the rocket
08:18 that will see time move more slowly
08:21 and will only age 20 years.
08:23 @aresforce1 asks, "The speed of light
08:26 "as constant is falsehood.
08:28 "What's the speed of light in water?
08:29 "Slower?"
08:30 The speed of light as a constant is not a falsehood.
08:33 We have a glass of water
08:34 and I'm gonna put this pencil in there.
08:36 And when I put the pencil in, the pencil looks bent.
08:39 The light that's coming out that you're seeing is bent.
08:42 That bending comes from the fact
08:44 that as the light hits it at some angle,
08:47 it sort of veers in that direction.
08:48 The light's interacting with the water.
08:50 It's getting absorbed and re-emitted.
08:52 It's seeing a little bit longer paths as it gets scattered.
08:55 And it's that that makes the light look like it's bent.
08:58 But those interactions take a little bit of time.
09:00 And that's why we say
09:01 that it's effectively moving more slowly.
09:03 Between one interaction and the next,
09:05 the speed of light is the speed of light.
09:07 @AquariusDonk asks, "The question is,
09:10 "how does time dilation work?"
09:12 Long story short, time dilation is the fact
09:15 that when you're moving really close to the speed of light,
09:17 time passes more slowly.
09:19 It's pretty simple to write down.
09:21 The time that passes for someone who's moving at some speed
09:25 is proportional to how time is passing
09:29 for someone who's not moving at that speed.
09:31 And there's this funky square root down here.
09:34 And what matters is the comparison
09:36 of how fast that person's moving.
09:38 That's what V is as compared to the speed of light.
09:41 And in that line there.
09:42 And as you go faster and faster and faster,
09:45 that factor of delta T prime gets longer
09:48 and longer and longer.
09:49 So time is passing more and more slowly.
09:52 When you get to the speed of light, time no longer passes.
09:56 @NeilCameron78 asks,
09:58 "Are black holes really wormholes?
10:00 "Or are wormholes really black holes?"
10:03 Eh, eh?
10:04 Hashtag science.
10:05 We know black holes exist.
10:07 We can see evidence for them out there.
10:09 We've seen light around these black holes
10:12 and what it looks like.
10:13 We've seen the silhouette of a black hole.
10:15 Wormholes are a shortcut through space-time
10:19 from one place to another.
10:20 The first idea of a wormhole
10:22 is something called an Einstein-Rosen bridge.
10:24 It would take moving faster than the speed of light
10:27 to travel through.
10:27 And we have no evidence whatsoever that wormholes exist.
10:31 Some physicists have posited that if we use
10:35 some of the special characteristics of quantum field theory,
10:38 that maybe we can create tiny, tiny little wormholes
10:41 that we can send a signal through
10:43 from one place in space-time to another.
10:45 And while these have been successful as thought experiments
10:49 and successful as computer simulations,
10:52 it's not yet been seen in the real world
10:54 in a real life experiment.
10:56 @mattp1949 asks, "You think time travel is possible
11:00 "under current physics understanding?"
11:02 No, probably not.
11:04 At least not from what we understand right now.
11:07 There's a couple of ways to think about
11:09 how we might travel in time.
11:11 One way is using a wormhole.
11:13 Some physicists have done this thought experiment
11:15 and written down all of the pieces you would need.
11:18 So you build a wormhole that somehow changes
11:20 and tunnels through space-time back into the past.
11:23 You write down the math for what that wormhole looks like.
11:25 The kind of matter that you would need
11:27 to hold that wormhole open
11:28 doesn't exist in our current understanding of physics.
11:31 The type of matter that you would need
11:32 to hold a wormhole open is called exotic matter.
11:35 Things like negative energy density,
11:37 which what does that mean?
11:38 It means like thinking of something with negative mass.
11:40 So I don't know if we're going to be building
11:42 a time machine anytime soon,
11:44 unless we can figure out how to find
11:47 and make this exotic matter.
11:49 @bradalexandru asks, "Is there anything infinite
11:52 "in the real world, or is infinity just a concept
11:55 "in our mind?"
11:56 Infinity is not just a concept in our minds.
11:59 The most important infinity that I study
12:01 is that the universe is infinite.
12:03 So that's a great example of something that's infinite.
12:05 We use infinities all the time
12:07 when we're making predictions in physics,
12:09 and it turns out that the size of the universe is infinite.
12:13 The amount of time the universe will be around
12:15 is also infinite.
12:16 @onedaywellbeok asks, "Quick question.
12:19 "Does anybody know the difference
12:20 "between particle physics and quantum physics, please?"
12:24 Particle physics is a small part of quantum physics,
12:27 and quantum physics is the area of physics
12:29 that really studies small stuff
12:31 and the interactions on really, really small scales.
12:34 But particle physics focuses on the particles
12:37 that make up atoms, the fundamental particles
12:40 that make up everything around us.
12:42 @cypher707 asks, "I thought quantum physics was a fanfic."
12:46 Absolutely not.
12:47 Quantum physics is how the world works,
12:49 but you have to look at a really small scale
12:51 to understand what's going on.
12:53 If I throw a ball up in the air,
12:54 it comes down back into my hand.
12:56 That's classical physics.
12:57 Quantum physics acts in surprising ways.
13:00 So instead of having pure predictions
13:03 about what's gonna happen at a quantum level,
13:05 we just get probabilities.
13:06 There's a 50% chance that this thing is gonna happen,
13:09 a 20% chance that this other thing is going to happen.
13:12 If you watch a lot of Marvel movies,
13:14 I could see why you'd think it was fanfic,
13:15 because it gets used anytime you don't know
13:18 how to explain the science that you wanna do.
13:20 @ravenbiter asks, "Lecturer just asked
13:22 "what Heisenberg contributed to physics,
13:24 "and loads of people answered crystal meth."
13:26 That's a different Heisenberg.
13:28 The Heisenberg that we know
13:29 is a very famous quantum physicist.
13:31 He worked with the German government during World War II,
13:34 but he's really well known for being one of the people
13:37 who figured out all of these rules of quantum mechanics
13:40 really early on.
13:41 He came up with something called the uncertainty principle.
13:43 Basically, if I know one aspect of a particle,
13:48 like where it is, I can't know
13:50 how fast it's moving very well.
13:52 Or if I know how fast it's moving, I can't know where it is.
13:56 @timambergy asks, "I just learned about quantum entanglement
14:00 "and I'm shook.
14:01 "How can two particles be so connected
14:03 "that they affect each other
14:04 "even when they're light years apart?
14:06 "Is this the secret to long distance relationships?
14:08 "#quantumlove."
14:10 Two particles, light years apart,
14:12 can absolutely be connected
14:14 if we've set them up in a entangled state.
14:17 And what that means is we take two particles
14:20 where the measurement has something to do with chance.
14:23 So if I roll this dice, whatever value I get on that face,
14:27 I'm gonna get the same value on the other dice
14:30 if that's how I've set up the entangled system.
14:32 And these two particles can be very, very far apart
14:35 from each other.
14:36 And this is just how nature works.
14:37 The weird part about this is the chance
14:39 that no matter how I roll the dice,
14:42 whatever it lands on, the other dice will land
14:44 on the same exact value.
14:46 This is just a fundamental way about how the universe works.
14:49 @utb asks, "What the hell does the Large Hadron Collider
14:52 "do anyways?"
14:53 The Large Hadron Collider
14:55 is the largest particle accelerator in the world.
14:58 It is a huge 10 kilometer circle in Switzerland
15:02 where we take two streams of protons.
15:05 Protons are a kind of hadron.
15:06 Hadrons are really heavy particles.
15:09 Takes those two streams of protons
15:11 and aligns them just right.
15:12 They're going almost the speed of light, not quite,
15:14 but almost the speed of light.
15:15 And smashes them into each other.
15:17 The faster you can get those protons to go,
15:19 the more stuff comes out of that explosion
15:21 when you smash them together.
15:22 We're making new particles that we haven't seen before.
15:25 They're part of nature,
15:26 but they take so much energy to make
15:29 that they haven't been around since the Big Bang
15:31 when the universe was really tiny
15:33 and really, really energetic.
15:34 So not only are we learning about these fundamental forces,
15:37 we're also learning about physics
15:38 right at the beginning of our universe.
15:40 @physicsinhistory asks, "Is string theory really a dead end?"
15:45 No, it's not a dead end.
15:46 String theory is a theory that says
15:48 instead of the fundamental pieces
15:51 of the universe being particles, they're strings.
15:53 And these strings can vibrate in different ways.
15:55 You can have strings that are long.
15:57 You can have strings that are in loops.
15:59 And not only does it describe all of particle physics
16:02 and quantum mechanics,
16:03 some pieces of this actually predict
16:05 what quantum gravity would look like.
16:07 Gravity on a really small scale,
16:09 which is not a theory that we have right now.
16:11 So those are all the questions for today.
16:13 Thanks for such insightful questions.
16:16 Thanks for watching Physics Support.
16:17 (thudding)