1 00:00:02,040 --> 00:00:06,760 Speaker 1: Welcome to brain stuff from how stuff works, Hey, brain 2 00:00:06,800 --> 00:00:10,640 Speaker 1: stuff luring vocal bomb here. All things considered, our atmosphere 3 00:00:10,720 --> 00:00:14,480 Speaker 1: is pretty great. This blanket of nitrogen, oxygen, and other 4 00:00:14,520 --> 00:00:18,320 Speaker 1: gases keeps the world's temperature nice and habitable while protecting 5 00:00:18,400 --> 00:00:21,239 Speaker 1: us from harmful UV radiation. To say nothing of this 6 00:00:21,320 --> 00:00:24,720 Speaker 1: space debris vaporizes for us. Oh yeah, and without all 7 00:00:24,760 --> 00:00:27,960 Speaker 1: that oxygen in our atmosphere, animal life couldn't survive on 8 00:00:28,040 --> 00:00:32,080 Speaker 1: planet Earth. Not a bad resume. But despite its many 9 00:00:32,080 --> 00:00:36,000 Speaker 1: good qualities, the atmosphere can be a nuisance to astronomy buffs. 10 00:00:36,360 --> 00:00:40,440 Speaker 1: That's because it distorts light. At night, the atmosphere makes 11 00:00:40,479 --> 00:00:44,000 Speaker 1: some heavenly bodies appeared to flicker and shimmer. The technical 12 00:00:44,080 --> 00:00:48,320 Speaker 1: term for this phenomenon is astronomical scintillation. You probably know 13 00:00:48,400 --> 00:00:51,680 Speaker 1: it by a different name, twinkling like an onion. The 14 00:00:51,760 --> 00:00:54,640 Speaker 1: atmosphere is made up of layers. At the bottom is 15 00:00:54,680 --> 00:00:57,720 Speaker 1: the troposphere, which starts right here at ground level on 16 00:00:57,760 --> 00:01:01,160 Speaker 1: the planet's surface. Standing about five to nine miles that's 17 00:01:01,200 --> 00:01:04,640 Speaker 1: eight to four point five kilometers tall, It's where most 18 00:01:04,680 --> 00:01:08,080 Speaker 1: of Earth's weather events take place. The other layers are 19 00:01:08,120 --> 00:01:13,920 Speaker 1: in ascending order, The stratosphere mesosphere, thermosphere, and exosphere. There's 20 00:01:13,959 --> 00:01:16,960 Speaker 1: also a region called the ionosphere, which encompasses parts of 21 00:01:17,000 --> 00:01:22,400 Speaker 1: both the mesosphere and the thermosphere. These layers have different temperatures. 22 00:01:22,720 --> 00:01:26,080 Speaker 1: In addition, the air's density varies from level to level. 23 00:01:26,520 --> 00:01:29,840 Speaker 1: When starlight enters our atmosphere, it runs into pockets of 24 00:01:29,959 --> 00:01:33,600 Speaker 1: cool and warm air. The pockets act as big lenses, 25 00:01:33,760 --> 00:01:36,920 Speaker 1: causing the light to change direction or refract as it 26 00:01:36,959 --> 00:01:40,440 Speaker 1: passes through them. Yet the lenses are not fixed in place. 27 00:01:40,520 --> 00:01:44,319 Speaker 1: They move around and change shape as they shift. So 28 00:01:44,400 --> 00:01:48,160 Speaker 1: does starlight refraction. That's why the stars appear to twinkle. 29 00:01:49,040 --> 00:01:53,400 Speaker 1: Scintillation affects planets to Mercury, Venus, Mars, and the other 30 00:01:53,480 --> 00:01:56,440 Speaker 1: planets in our Solar system do twinkle when viewed from 31 00:01:56,440 --> 00:01:59,720 Speaker 1: Earth on a clear night. So does our moon. However, 32 00:01:59,800 --> 00:02:04,040 Speaker 1: the planets twinkled to a barely noticeable degree distance is 33 00:02:04,080 --> 00:02:07,840 Speaker 1: the main reason stars twinkle more conspicuously than the planets 34 00:02:07,840 --> 00:02:11,320 Speaker 1: in our Solar system, because the former are so far away, 35 00:02:11,639 --> 00:02:14,720 Speaker 1: each star looks like a single pinpoint of light, a 36 00:02:14,800 --> 00:02:17,800 Speaker 1: single pixel. You might say. It's a different story for 37 00:02:17,840 --> 00:02:21,560 Speaker 1: Earth's moon and our neighboring planets, being a lot closer 38 00:02:21,600 --> 00:02:25,360 Speaker 1: they're less affected by the atmosphere. Planets and moons appear 39 00:02:25,400 --> 00:02:27,880 Speaker 1: as tiny disks up in the sky. The light they 40 00:02:27,919 --> 00:02:30,320 Speaker 1: emanate comes not from a single point, but from many 41 00:02:30,360 --> 00:02:35,240 Speaker 1: individual points, all clustered together. These rarely scintillate in unison, 42 00:02:35,320 --> 00:02:38,320 Speaker 1: which is why planets and moons don't twinkle as dramatically 43 00:02:38,360 --> 00:02:42,080 Speaker 1: as the stars, So twinkling can only happen when an 44 00:02:42,120 --> 00:02:45,360 Speaker 1: atmosphere is present. It's for this reason that photos taken 45 00:02:45,360 --> 00:02:48,119 Speaker 1: by the Hubble telescope looks so clear. There aren't any 46 00:02:48,160 --> 00:02:52,239 Speaker 1: atmospheric air pockets to refract the starlight. Earth Bound astronomers 47 00:02:52,320 --> 00:02:55,919 Speaker 1: use telescopes with adaptive optics systems to compensate for twinkling, 48 00:02:56,160 --> 00:03:04,280 Speaker 1: making the stars look more stable. Today's episode was written 49 00:03:04,280 --> 00:03:07,440 Speaker 1: by Mark Mancini and produced by Tyler Clang. Brain Stuff 50 00:03:07,440 --> 00:03:09,840 Speaker 1: has merch now. You can get phone cases, tote bags, 51 00:03:09,960 --> 00:03:12,679 Speaker 1: and of course T shirts. Every purchase helps keep the 52 00:03:12,680 --> 00:03:15,280 Speaker 1: show going and supports us directly. You can find all 53 00:03:15,280 --> 00:03:18,600 Speaker 1: that stuff at t public dot com slash brain Stuff. 54 00:03:18,680 --> 00:03:20,800 Speaker 1: For more on this and lots of other bright topics, 55 00:03:20,919 --> 00:03:34,640 Speaker 1: visit our home planet how Stuff works dot com.