WEBVTT - BrainStuff Classics: What Is Light?

0:00:01.840 --> 0:00:07.600
<v Speaker 1>Welcome to brain Stuff, a production of iHeartRadio. Hey brain Stuff,

0:00:07.600 --> 0:00:10.400
<v Speaker 1>I'm Lauren vogel Bomb, and this is another episode from

0:00:10.480 --> 0:00:13.720
<v Speaker 1>the Vault. This one goes into the history of how

0:00:13.760 --> 0:00:17.120
<v Speaker 1>people have thought of light. After all, our planet runs

0:00:17.120 --> 0:00:19.800
<v Speaker 1>on it. But it's actually a pretty weird phenomenon right

0:00:19.880 --> 0:00:25.400
<v Speaker 1>up through today's scientific theories for how it works. Hey

0:00:25.440 --> 0:00:26.720
<v Speaker 1>brain Stuff, Lauren vocal Bomb.

0:00:26.800 --> 0:00:30.000
<v Speaker 2>Here, light, in addition to being a bright patch of

0:00:30.000 --> 0:00:33.720
<v Speaker 2>sunshine on your windowsill, is a metaphor for enlightenment and exploration,

0:00:34.360 --> 0:00:37.120
<v Speaker 2>which is a bit paradoxical for a phenomenon that, even

0:00:37.200 --> 0:00:41.080
<v Speaker 2>after thousands of years of inquiries and endless experiments, scientists

0:00:41.120 --> 0:00:44.120
<v Speaker 2>still can't quite explain. Is it a particle or a

0:00:44.159 --> 0:00:47.120
<v Speaker 2>wave or both or neither? Do we need a new

0:00:47.159 --> 0:00:50.240
<v Speaker 2>word for it? Your eyes tell you a lot about

0:00:50.280 --> 0:00:53.040
<v Speaker 2>the way light behaves. It travels so fast that it

0:00:53.080 --> 0:00:56.400
<v Speaker 2>seems instantaneous, about one hundred and eighty six thousand miles

0:00:56.480 --> 0:00:59.840
<v Speaker 2>or three thousand kilometers per second. It blazes through air

0:00:59.880 --> 0:01:03.880
<v Speaker 2>and space and laser like straight lines. But it also bounces, reflects,

0:01:03.880 --> 0:01:06.760
<v Speaker 2>and refracts, and when it interacts with the right medium

0:01:06.880 --> 0:01:10.319
<v Speaker 2>like a camera lens, it may curve. We know that

0:01:10.319 --> 0:01:12.560
<v Speaker 2>it's made up of tiny units that we call photons,

0:01:12.600 --> 0:01:15.120
<v Speaker 2>and we know that the term waves can describe its movements,

0:01:15.360 --> 0:01:19.520
<v Speaker 2>but neither of these words really encompass light's oddities. In

0:01:19.600 --> 0:01:22.520
<v Speaker 2>ancient times, the Greeks used philosophy to attempt to address

0:01:22.600 --> 0:01:26.080
<v Speaker 2>light's wide range of behaviors. Perhaps they thought light is

0:01:26.080 --> 0:01:28.560
<v Speaker 2>actually composed of little bits of stuff that bounced to

0:01:28.640 --> 0:01:32.000
<v Speaker 2>and fro. The idea never really caught on. Then, in

0:01:32.000 --> 0:01:35.560
<v Speaker 2>the sixteen hundreds, French philosopher Renee des Cartes became convinced

0:01:35.600 --> 0:01:38.039
<v Speaker 2>that light was essentially a wave, one that moved through

0:01:38.040 --> 0:01:41.880
<v Speaker 2>a mysterious substance that he called plenim Isaac Newton thought

0:01:41.880 --> 0:01:43.600
<v Speaker 2>that light was a particle, but he was at a

0:01:43.640 --> 0:01:45.840
<v Speaker 2>loss for a way to explain many of its properties,

0:01:46.000 --> 0:01:48.040
<v Speaker 2>like the way it refracted and could be split by

0:01:48.040 --> 0:01:50.400
<v Speaker 2>a prism from a single beam of white light into

0:01:50.440 --> 0:01:54.400
<v Speaker 2>a rainbow of many colors of light. This was largely

0:01:54.400 --> 0:01:57.200
<v Speaker 2>before the rise of empirical studies in science, wherein we

0:01:57.200 --> 0:01:59.680
<v Speaker 2>attempt to answer questions about the world around us by

0:01:59.680 --> 0:02:04.200
<v Speaker 2>design any experiments that demonstrate well how stuff works. Back

0:02:04.200 --> 0:02:07.480
<v Speaker 2>in the day, science was a matter of philosophy, people

0:02:07.480 --> 0:02:10.080
<v Speaker 2>coming up with ideas about how stuff works and basically

0:02:10.240 --> 0:02:15.320
<v Speaker 2>arguing about the idea's merit to be fair. Our modern microscopes, computers,

0:02:15.320 --> 0:02:19.600
<v Speaker 2>and other equipment help. Just for example, light's behavior becomes

0:02:19.639 --> 0:02:22.760
<v Speaker 2>more evident depending on where you're observing it. In the

0:02:22.800 --> 0:02:25.520
<v Speaker 2>vacuum of space, light zips long at the aforementioned one

0:02:25.600 --> 0:02:27.960
<v Speaker 2>hundred and eighty six thousand miles or three hundred thousand

0:02:28.000 --> 0:02:31.000
<v Speaker 2>kilometers per second. But point a beam of light at

0:02:31.040 --> 0:02:33.720
<v Speaker 2>a very dense bit of matter, say a diamond, and

0:02:33.760 --> 0:02:36.800
<v Speaker 2>it can slow to only around seventy seven thousand miles

0:02:36.880 --> 0:02:39.320
<v Speaker 2>or one hundred and twenty four thousand kilometers per second,

0:02:39.800 --> 0:02:44.120
<v Speaker 2>much easier to observe relatively. To try to explain in

0:02:44.160 --> 0:02:47.480
<v Speaker 2>these are modern times, what light is, let's first remember

0:02:47.560 --> 0:02:51.560
<v Speaker 2>some science basics. Waves are not a thing or a substance.

0:02:51.600 --> 0:02:54.320
<v Speaker 2>They're a property of a thing. A wave is a

0:02:54.360 --> 0:02:57.600
<v Speaker 2>compressing and stretching of a particular medium, like an ocean

0:02:57.600 --> 0:03:00.240
<v Speaker 2>wave that drives toward the shore, or the rip that

0:03:00.280 --> 0:03:01.960
<v Speaker 2>spreads out across the surface of a pond.

0:03:02.000 --> 0:03:03.360
<v Speaker 1>When you toss in a rock.

0:03:03.960 --> 0:03:06.080
<v Speaker 2>You can see the waves with your eyes, feel them

0:03:06.120 --> 0:03:08.840
<v Speaker 2>with your body, and sometimes when a sound wave happens

0:03:08.880 --> 0:03:12.280
<v Speaker 2>in the air, you can hear them with your ears. Particles,

0:03:12.320 --> 0:03:15.000
<v Speaker 2>on the other hand, are not quite so easy to define.

0:03:15.400 --> 0:03:18.000
<v Speaker 2>A particle can be a tiny bit of matter, a

0:03:18.040 --> 0:03:21.680
<v Speaker 2>matter broken down into its smallest and most basic units. Water,

0:03:21.760 --> 0:03:24.560
<v Speaker 2>for example, is made up of countless particles particles that

0:03:24.600 --> 0:03:28.160
<v Speaker 2>are affected by waves. What's really happening when you watch

0:03:28.160 --> 0:03:29.680
<v Speaker 2>a wave in the ocean or a ripple in a

0:03:29.720 --> 0:03:32.600
<v Speaker 2>pond is that each particle or molecule in this case

0:03:32.639 --> 0:03:35.640
<v Speaker 2>of water, is being moved, and thus the medium of

0:03:35.640 --> 0:03:39.000
<v Speaker 2>the ocean or pond is being compressed and stretched in sequence,

0:03:39.160 --> 0:03:43.680
<v Speaker 2>and we see waves. But light, as experiments have proven,

0:03:44.000 --> 0:03:46.960
<v Speaker 2>also consists of particles that we call photons that behave

0:03:47.320 --> 0:03:51.760
<v Speaker 2>like waves. Let's unpack that. There was a famous nineteenth

0:03:51.840 --> 0:03:55.440
<v Speaker 2>century double slit experiment in which researchers beamed light through

0:03:55.440 --> 0:03:57.840
<v Speaker 2>two slits and observed the way the light struck a

0:03:57.880 --> 0:04:00.560
<v Speaker 2>screen behind the slits. What they say saw was that

0:04:00.560 --> 0:04:03.320
<v Speaker 2>the streams of light affected each other like two hands

0:04:03.360 --> 0:04:05.680
<v Speaker 2>splashing water in the same sink, as if they were

0:04:05.720 --> 0:04:09.800
<v Speaker 2>waves interfering with one another. But then in the twentieth century,

0:04:09.880 --> 0:04:14.240
<v Speaker 2>scientists began their pioneering explorations into subatomic particles like neutrons

0:04:14.240 --> 0:04:17.440
<v Speaker 2>and electrons. Albert Einstein wondered what would happen if you

0:04:17.480 --> 0:04:20.159
<v Speaker 2>emitted light one photon at a time in the double

0:04:20.160 --> 0:04:25.159
<v Speaker 2>slit experiment. What scientists saw dumbfounded them. The single photons

0:04:25.200 --> 0:04:27.520
<v Speaker 2>went individually through the slits, but the way that they

0:04:27.600 --> 0:04:31.000
<v Speaker 2>struck the screen over time showed the same interference pattern

0:04:31.040 --> 0:04:33.520
<v Speaker 2>that occurred with full scale beams of light streaming through

0:04:33.600 --> 0:04:37.280
<v Speaker 2>both slits. This behavior can't be explained by the physics

0:04:37.360 --> 0:04:39.800
<v Speaker 2>we use to describe particles and waves in the macro

0:04:39.960 --> 0:04:43.160
<v Speaker 2>world around us. It's in the realm of quantum mechanics,

0:04:43.360 --> 0:04:45.560
<v Speaker 2>the physics theories that describe what goes on at the

0:04:45.720 --> 0:04:49.200
<v Speaker 2>very smallest subatomic levels and which we humans still don't

0:04:49.240 --> 0:04:53.039
<v Speaker 2>really understand. So ultimately, if you want to answer the

0:04:53.080 --> 0:04:55.320
<v Speaker 2>question what is light, you could call it both a

0:04:55.360 --> 0:04:58.560
<v Speaker 2>particle and a wave and you'd be correct. But as

0:04:58.600 --> 0:05:01.880
<v Speaker 2>for fully explaining why and how it works, we're still

0:05:01.880 --> 0:05:08.640
<v Speaker 2>working on it. Today's episode is based on the article

0:05:08.839 --> 0:05:11.359
<v Speaker 2>Ray of Enlightenment Is Light a wave or a Particle?

0:05:11.440 --> 0:05:14.000
<v Speaker 1>On How Stuffworks? Dot Com? Written by Nathan Chandler, who

0:05:14.120 --> 0:05:16.960
<v Speaker 1>drew from the podcast Daniel and Hlurge Explain the Universe,

0:05:17.040 --> 0:05:19.839
<v Speaker 1>which is a pretty cool one. Brain Stuff is production

0:05:19.920 --> 0:05:22.240
<v Speaker 1>by Heart Radio in partnership with how stuffworks dot com

0:05:22.279 --> 0:05:25.040
<v Speaker 1>and is produced by Tyler Klang. Or more podcasts my

0:05:25.160 --> 0:05:28.520
<v Speaker 1>heart Radio, visit the iHeartRadio app, Apple Podcasts, or wherever

0:05:28.520 --> 0:05:30.000
<v Speaker 1>you listen to your favorite shows.