Speaker 1: Welcome to brain stuff from how stuff works, Hey, brain
Speaker 1: stuff luring vocal bomb here. All things considered, our atmosphere
Speaker 1: is pretty great. This blanket of nitrogen, oxygen, and other
Speaker 1: gases keeps the world's temperature nice and habitable while protecting
Speaker 1: us from harmful UV radiation. To say nothing of this
Speaker 1: space debris vaporizes for us. Oh yeah, and without all
Speaker 1: that oxygen in our atmosphere, animal life couldn't survive on
Speaker 1: planet Earth. Not a bad resume. But despite its many
Speaker 1: good qualities, the atmosphere can be a nuisance to astronomy buffs.
Speaker 1: That's because it distorts light. At night, the atmosphere makes
Speaker 1: some heavenly bodies appeared to flicker and shimmer. The technical
Speaker 1: term for this phenomenon is astronomical scintillation. You probably know
Speaker 1: it by a different name, twinkling like an onion. The
Speaker 1: atmosphere is made up of layers. At the bottom is
Speaker 1: the troposphere, which starts right here at ground level on
Speaker 1: the planet's surface. Standing about five to nine miles that's
Speaker 1: eight to four point five kilometers tall, It's where most
Speaker 1: of Earth's weather events take place. The other layers are
Speaker 1: in ascending order, The stratosphere mesosphere, thermosphere, and exosphere. There's
Speaker 1: also a region called the ionosphere, which encompasses parts of
Speaker 1: both the mesosphere and the thermosphere. These layers have different temperatures.
Speaker 1: In addition, the air's density varies from level to level.
Speaker 1: When starlight enters our atmosphere, it runs into pockets of
Speaker 1: cool and warm air. The pockets act as big lenses,
Speaker 1: causing the light to change direction or refract as it
Speaker 1: passes through them. Yet the lenses are not fixed in place.
Speaker 1: They move around and change shape as they shift. So
Speaker 1: does starlight refraction. That's why the stars appear to twinkle.
Speaker 1: Scintillation affects planets to Mercury, Venus, Mars, and the other
Speaker 1: planets in our Solar system do twinkle when viewed from
Speaker 1: Earth on a clear night. So does our moon. However,
Speaker 1: the planets twinkled to a barely noticeable degree distance is
Speaker 1: the main reason stars twinkle more conspicuously than the planets
Speaker 1: in our Solar system, because the former are so far away,
Speaker 1: each star looks like a single pinpoint of light, a
Speaker 1: single pixel. You might say. It's a different story for
Speaker 1: Earth's moon and our neighboring planets, being a lot closer
Speaker 1: they're less affected by the atmosphere. Planets and moons appear
Speaker 1: as tiny disks up in the sky. The light they
Speaker 1: emanate comes not from a single point, but from many
Speaker 1: individual points, all clustered together. These rarely scintillate in unison,
Speaker 1: which is why planets and moons don't twinkle as dramatically
Speaker 1: as the stars, So twinkling can only happen when an
Speaker 1: atmosphere is present. It's for this reason that photos taken
Speaker 1: by the Hubble telescope looks so clear. There aren't any
Speaker 1: atmospheric air pockets to refract the starlight. Earth Bound astronomers
Speaker 1: use telescopes with adaptive optics systems to compensate for twinkling,
Speaker 1: making the stars look more stable. Today's episode was written
Speaker 1: by Mark Mancini and produced by Tyler Clang. Brain Stuff
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Speaker 1: that stuff at t public dot com slash brain Stuff.
Speaker 1: For more on this and lots of other bright topics,
Speaker 1: visit our home planet how Stuff works dot com.