—
Welcome to the first episode of Crash Course Astronomy. Your host for this intergalactic adventure is the Bad Astronomer himself, Phil Plait. We begin with answering a question: “What is astronomy?”
—
—
Transcript Provided by YouTube:
00:03
Hello, and welcome to Crash Course Astronomy! I’m your host, Phil Plait, and I’ll be
00:06
taking you on a guided tour of the entire Universe. You might want to pack a lunch.
00:21
Over the course of this series we’ll explore planets, stars, black holes, galaxies, subatomic
00:27
particles, and even the eventual fate of the Universe itself.
00:31
But before we step into space, let’s take a step back. I wanna talk to you about science.
00:36
There are lots of definitions of science, but I’ll say that it’s a body of knowledge,
00:40
and a method of how we learned that knowledge.
00:42
Science tells us that stuff we know may not be perfectly known; it may be partly or entirely
00:47
wrong. We need to watch the Universe, see how it behaves, make guesses about why it’s
00:53
doing what it’s doing, and then try to think of ways to support or disprove those ideas.
00:57
That last part is important. Science must be, above all else, honest if we really want
01:03
to get to the bottom of things.
01:05
Understanding that our understanding might be wrong is essential, and trying to figure
01:09
out the ways we may be mistaken is the only way that science can help us find our way
01:14
to the truth, or at least the nearest approximation to it.
01:17
Science learns. We meander a bit as we use it, but in the long run we get ever closer
01:23
to understanding reality, and that is the strength of science. And it’s all around us!
01:28
Whether you know it or not, you’re soaking in science.
01:31
You’re a primate. You have mass. Mitochondria
01:34
in your cells are generating energy. Presumably, you’re breathing oxygen.
01:38
But astronomy is different. It’s still science, of course, but astronomy puts you in your place.
01:43
Because of astronomy, I know we’re standing on a sphere of mostly molten rock and metal
01:48
13,000 kilometers across, with a fuzzy atmosphere about 100 km high, surrounded by a magnetic
01:54
field that protects us from the onslaught of subatomic particles from the Sun 150 million
02:00
km away, which is also flooding space with light that reaches across space, to illuminate
02:05
the planets, asteroids, dust, and comets, racing out past the Kuiper Belt, through the
02:10
Oort Cloud, into interstellar space, past the nearest stars, which orbit along with
02:14
gas clouds and dust lanes in a gigantic spiral galaxy we call the Milky Way that has a supermassive
02:20
black hole in its center, and is surrounded by 150 globular clusters and a halo of dark
02:25
matter and dwarf galaxies, some of which it’s eating, all of which can be seen by other
02:29
galaxies in our Local Group like Andromeda and Triangulum, and our group is on the outskirts
02:34
of the Virgo galaxy cluster, which is part of the Virgo supercluster, which is just one
02:38
of many other gigantic structures that stretch most of the way across the visible Universe,
02:43
which is 90-billion light years across and expanding every day, even faster today than
02:48
yesterday due to mysterious dark energy, and even all that might be part of an infinitely
02:53
larger multiverse that extends forever both in time and space.
02:57
See? Astronomy puts you in your place.
03:00
But what exactly is astronomy? This isn’t necessarily an obvious thing to ask. When
03:04
I was a kid, it was easy: Astronomy is the study of things in the sky. The sun, moon,
03:10
stars, galaxies, and stuff like that. But it’s not so easy to pigeonhole these days.
03:15
Take, for example, Mars. When I haul my ‘scope out to the end of my driveway and look at
03:20
Mars, that’s astronomy, right? Of course! But what about the rovers there? Those machines
03:25
aren’t doing astronomy, surely. They’re doing chemistry, geology, hydrology, petrology…
03:30
everything but astronomy!
03:32
So nowadays, what’s astronomy? I’d say it’s still studying stuff in the sky, but
03:36
it’s branched out quite a bit from there. Borders between it and other fields of science
03:41
are fuzzy… a theme I’ll be hitting on several times over this series. Humans might
03:45
like firm, delineated boundaries between things, but nature isn’t so picky.
03:49
And that brings us to our first edition of “Focus On…”
03:52
This week’s topic: Astronomers! Who are we? What do we do?
03:55
I used to look through telescopes for a living, or at least study the data that came from
03:59
detectors strapped onto them. But now I talk and write (and make videos) about astronomy,
04:05
and relegate my viewing to my personal backyard telescope. But I still consider myself an
04:10
astronomer, so that should give you an idea that there’s a lot of wiggle room in the profession.
04:14
In fact, when I worked on Hubble Space Telescope, I was actually hired as… a programmer!
04:19
I coded in the language used by the folks helping to build and calibrate a camera that
04:24
was due to launch into space and be installed onto Hubble by an astronaut.
04:27
Once the data from that camera are taken and analyzed, you have to know what to do with
04:31
them. Do the observations fit the physical model of how stars blow up, or how galaxies
04:36
form, or the way gas flows through space? Well, you better know your math and physics,
04:40
because that’s how we test our hypotheses. And someone who does that is generally called
04:45
an astrophysicist.
04:46
Of course, those telescopes and detectors don’t create themselves. We need engineers
04:50
to design and build them and technicians to use them.
04:53
Most astronomers don’t actually use the telescopes themselves anymore; someone who’s
04:57
trained in their specific use does that for them.
05:00
Some of those instruments go into space, and some go to other worlds, like the moon and Mars.
05:05
We need astronomers and engineers and software programmers who can build those, too.
05:09
And then, at the end of all this, we need people to tell you all about it. Teachers,
05:14
professors, writers, video makers, even artists.
05:16
So I’ll tell you what: If you have an interest in the Universe, if you love to look up at
05:21
the stars, if you crave to understand what’s going on literally over your head, then who
05:26
am I to say you’re not an astronomer?
05:27
However you define astronomy, humans have been looking up at the sky for as long as
05:31
we’ve been humans. Certainly ancient people noticed the big glowy
05:35
ball in the sky, and how it lit everything up while it was up, and how it got dark when
05:39
it was gone. The other, fainter glowy thing tried, but wasn’t quite as good as lighting
05:44
up the night. They probably took that sort of thing pretty seriously. They probably also
05:48
noticed that when certain stars appeared in the sky, the weather started getting warmer
05:52
and the days longer, and when other stars were seen, the weather would get colder and
05:57
daytime shorten.
05:58
And when humans settled down, discovered agriculture, and started farming, noticing those patterns
06:03
in the sky would have had an even greater impact. It told them when to plant seeds,
06:07
and when to harvest.
06:08
The cycles in the sky became pretty important. So important that it wasn’t hard to imagine
06:13
gods up there, looking down on us weak and ridiculous humans, interfering with our lives.
06:18
Surely if the stars tell us when to plant, and control the weather, seasons, and the
06:22
length of the day, they control our lives too… and astrology was born.
06:27
Astrology literally means “study of the stars”; as a word it’s been used before
06:32
science became a formal method of studying nature. It irks me a bit, since it got the
06:37
good name, and now we’re stuck with “astronomy,” which means “law or culture of the stars.”
06:42
That’s not really what we do! But what the heck. Words change meaning over time, and
06:47
now it’s pretty well understood that astronomy is science, and astrology… isn’t.
06:53
Millennia ago, astrology was as close to science as you got. It had some of the flavors of
06:58
science: astrologers observed the skies, made predictions about how it would affect people,
07:03
and then those people would provide evidence for it by swearing up and down it worked.
07:07
The thing is, it really didn’t; the fault of astrology lies in ourselves and not our
07:13
stars. People tend to remember the hits and forget the misses when predictions are made,
07:17
which is why they sometimes sit in casinos pumping nickels into machines that are in
07:22
proven to be nothing more than a method for reducing the number of nickels you have.
07:26
But astrology led to people to really study the sky, and find the patterns there, which
07:31
led to a more rigorous understanding of how things worked in the heavenly vault.
07:35
It wasn’t overnight, of course. This took centuries. Before the invention of the telescope,
07:40
keen observers built all sorts of odd and wonderful devices to measure the heavens,
07:45
and in fact it was before the telescope was first turned to the sky that a huge revolution
07:50
in astronomy took place.
07:51
It is patently obvious that the ground you stand on is fixed, rooted if you will, and
07:57
the skies turn above us. The sun rises, the sun sets. The moon rises and sets, the stars
08:03
themselves wheel around the sky at night. Clearly, the Earth is motionless, and the
08:08
sky is what is actually moving. In fact, if you think about it, geocentrism
08:12
makes perfect sense that all the objects in the sky revolve about the Earth, and are fixed
08:17
to a series of nested spheres, some of which are transparent, maybe made of crystal, which
08:22
spin once per day. The stars may just be holes in the otherwise opaque sphere, letting sunlight though.
08:28
Sounds silly to you, doesn’t it?
08:30
Well, here’s the thing: If you don’t have today’s modern understanding of how the
08:34
cosmos works, this whole multiple-shells-of-things-in- the-sky thing actually does make sense. It explains
08:41
a lot of what’s going on over your head, and if it was good enough for Plato, Aristotle,
08:45
and Ptolemy, then by god it was good enough for you. And speaking of which, it was endorsed
08:50
by the major religions of the time, so maybe it’s better if you just nod and agree and
08:55
don’t think about it too hard.
08:56
But a few centuries ago things changed. Although he wasn’t the first, the Polish mathematician
09:01
and astronomer Copernicus came up with the idea that the sun was the center of the solar
09:06
system, not the Earth. His ideas had problems, which we’ll get to in a later episode, but
09:11
it did an incrementally better job than geocentrism.
09:14
And then along came Tycho Brahe and Johannes Kepler, who modified that system, making it
09:19
even better. Then Isaac Newton – oh, Newton – he invented calculus partly to help him
09:26
understand the way objects moved in space. Over time, our math got better, our physics
09:31
got better, and our understanding grew. Applied math was a revolution in astronomy, and then
09:37
the use of telescopes was another. Galileo didn’t invent the telescope, by
09:40
the way, but made them better; Newton invented a new kind that was even better than that,
09:46
and we’ve run with the idea from there.
09:47
Then, about a century or so ago, came another revolution: photography. We could capture
09:53
much fainter objects on glass plates sprayed with light-sensitive chemicals, which revealed
09:58
stars otherwise invisible to us, details in galaxies, beautiful clouds of gas and dust in space.
10:04
And then in the latter half of the last century, digital detectors were invented, which were
10:09
even more sensitive than film. We could use computers to directly analyze observations,
10:14
and our knowledge leaped again. When these were coupled with telescopes sent in orbit
10:19
around the Earth – where our roiling and boiling atmosphere doesn’t blur out observations
10:23
– we began yet another revolution.
10:26
And where are we now?
10:27
We’ve come such a long way! What questions can we routinely ask that our ancestors would
10:32
not have dared, what statements made with a pretty good degree of certainty?
10:36
Think on this: The lights in the sky are stars! There are other worlds. We take the idea of
10:43
looking for life on alien planets seriously, and spend billions of dollars doing it. Our
10:48
galaxy is one of a hundred billion others. We can only directly see 4% of the Universe.
10:55
Stars explode, and when they do they create the stuff of life: the iron in our blood,
11:00
the calcium in our bones, the phosphorus that is the backbone of our DNA. The most common
11:06
kind of star in the Universe is so faint you can’t see it without a telescope. Our solar
11:10
system is filled to overflowing with worlds more bizarre than we could have dreamed.
11:16
Nature has more imagination than we do. It comes up with some nutty stuff. We’re clever
11:21
too, we big-brained apes. We’ve learned a lot… but there’s still a long way to go.
11:26
So, with that, I think we’re ready. Let’s explore the universe.
11:29
Today you learned what astronomy is, and that astronomers aren’t just people who operate
11:33
telescopes, but include mathematicians, engineers, technicians, programmers, and even artists.
11:39
We also wrapped up with a quick history of the origins and development of astronomy,
11:43
from ancient observers to the Hubble Space Telescope.
11:46
Crash Course is produced in association with PBS Digital Studios.
11:50
This episode was written by me, Phil Plait. The script was edited by Blake de Pastino,
11:54
and our consultant is Dr. Michelle Thaller. It was co-directed by Nicholas Jenkins and
11:58
Michael Aranda, and the graphics team is Thought Café.
—
This post was previously published on YouTube.
—
Photo credit: Screenshot from video.
.