"How do they know that?" Modern astronomy has made some astonishing discoveries - how stars burn and how black holes form; galaxies from the edge of the universe and killer rocks right next door; where the elements come from and how the expanding universe is accelerating. But how do we know all that? The truth is that astronomy would be impossible without technology, and every advance in astronomy is really an advance in technology. But the technology by itself is not enough. We have to apply it critically with a knowledge of physics to unlock the secrets of the Universe. Each week we will cover a different aspect of Astronomical technology, matching each piece of technology to a highlight science result. We will explain how the technology works, how it has allowed us to collect astronomical data, and, with some basic physics, how we interpret the data to make scientific discoveries. The class will consist of video lectures, weekly quizzes, and discussion forums. Each week there will be five videos, totalling approximately 40 minutes. They will be in a regular pattern - a short introduction, an example science story, an explanation of the key technology area, a look at how the technology is used in practice, and finally a look at what the future may hold.
W1 Part 2 - Revolutions in Astronomy
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Del curso dictado por The University of Edinburgh
AstroTech: The Science and Technology behind Astronomical Discovery
224 calificaciones
The University of Edinburgh
224 calificaciones
De la lección
Science and Technology
Introducing the themes of the course, and a first look at the science and technology we will study.
Conoce a los instructores
Andy Lawrence
Physics and Astronomy
Catherine Heymans
Physics and Astronomy
[BLANK_AUDIO]
Hi, one thing we can be sure of is that we
know more about the universe today than we did 500 years ago.
So why is that?
Is it because there's been a
series of brilliant astronomers having brilliant ideas?
Well yes, partly it is that.
But it's also because there's been a series
of technological revolutions that astronomy has benefited from.
Now, history is pretty complicated but we are
going to boil this down to six key steps.
[BLANK_AUDIO]
Revolution number one, the invention of the telescope.
Now to a sailor,
the telescope is all about magnifying the image,
making things look bigger.
But to an astronomer, telescopes are all about catching more light.
So we want them to be big.
Now the pupil of the eye is about 5 mm across.
On the other hand if we take a
pair of binoculars like this, or a small telescope,
that lens there is about 50 mm across, so it collects a 100 times more light.
You can see things a hundred times fainter.
On the other hand here this lovely teaching
telescope that we have here at the university.
The mirror of the telescope here is about 50 cm across,
so that's another factor of a 100 in its light gathering power.
Now big professional telescopes can be anything from 2 m
to 10 m across and so they collect even more
light and right now the the world community is developing
a giant new telescope which will be 40 m across,
which with great imagination is called the extremely large telescope.
And so we can catch more and more light and see fainter and fainter objects.
This produces technological challenges however, we'll
be looking at those in week two.
[BLANK_AUDIO]
Okay revolution number two, spectroscopy.
In the 17th century Isaac Newton first took light, put it through
a prism and split it up into it's component colors, into a spectrum.
So today we tend to do the same thing with
diffraction gratings rather than prisms, but it's the same basic idea.
And in the intervening 350 years, spectroscopy has been possibly the
key technique for Physics, for Chemistry, and even for Biology.
It tells us about the structure of matter.
But it was the Victorians who first had
the idea of pointing a spectroscope at the stars.
As was first done by William Huggins at Tulse Hill in London
and also by Alberto Secchi at the Vatican observatory, in Italy.
And what they saw was a revolution.
By breaking up the light into its spectrum we
were now able to tell what stars were made of,
how hot they were, and even how fast they were moving.
It's really the point in history where astronomy became
astrophysics and it's been a key technique ever since.
But the sort of spectrographs we bolt onto the back of
telescopes now are very big and they're very tricky to design.
And that's something we'll be talking about in week six.
[BLANK_AUDIO]
So revolution number three, photography, another great Victorian invention.
Let's have a look at this photographic plate
that I've got on the light table here.
Now photography did
two things for astronomy.
The first was it enabled us to get
an objective image to record an image permanently.
So we didn't have to rely on some dodgy astronomer's sketch.
We could simply see, anybody could see what that
part the sky looked like by looking at the photograph.
So that's advantage number one.
Advantage number two is that astronomers were able to integrate, that is to keep
exposing the plate adding up more and more light to see fainter and fainter objects.
And this plate goes pretty deep.
Now the human eye when we're receiving information it
feels like a continuous movie, but actually of course we're
integrating for 1 25th of a second, on the retina.
Pretty soon astronomers with, their glass plates were keeping
them bolted to the telescope and exposing them the whole night.
Now today we don't use photographic plates
anymore, but we use another solid state detector.
This is what we use most often.
It's a CCD.
This is pretty much the same as the detector in
your phone camera, but it's considerably bigger and also more efficient.
So that's a CCD camera.
Now, astronomers now like to make even bigger cameras
by putting lots of them together in a mosaic.
You can see that in this picture here of the PanSTARRS camera in Hawaii.
That's a gigapixel camera and covers a large amount of sky in one go.
CCD is also very efficient.
They catch more of the light and so we can go deeper and deeper.
We also have similar detectors that for example work at infrared wave lengths.
And this picture you're seeing here, this is
the ultra deep survey made on the UKIRT telescope.
That involved adding up data effectively exposing for hundreds of nights.
[BLANK_AUDIO]
Revolution number four, is a 20th century revolution.
The revolution of multi-wavelength astronomy.
Now light, is an electromagnetic wave in space.
And the lengths of the waves can be very different.
They can be little tiny nanometer length
waves or they can be great big long, meter long waves.
It covers a bit range.
Now what we refer to as light normally, visible light, just happens to be
a small range of wavelengths that we can detect with the retina of our eye.
But there's a lot more out there.
Radio waves.
Infrared, ultraviolet, x-rays, they're all light,
but they have very different wave lengths.
Now if we're going to detect those
different kinds of light with something other
than our eye we need completely
different technologies for each of those wavelengths.
So the story of the 20th century was one of.
opening up wavelength windows and seeing the universe in a different way.
In the ultraviolet and x-rays, and radio and so on.
And every time we opened up a new window, we
saw completely different objects and the universe seemed very different.
We discovered relativistic jets spinning neutron stars,
gas at millions of degrees -
Something weird every time we tried something new.
[BLANK_AUDIO]
Revolution number five, space astronomy.
Arguably, since the 1960s, this is the thing that's made more difference than
anything else to our understanding of the universe -
the ability to launch things into space.
So here's a picture of the Hubble
space telescope being launched on the space shuttle.
And here is another picture of the
Hubble space telescope in orbit taken from the space shuttle.
So it makes an enormous difference.
But, it's very, very expensive.
So why do it?
For the same amount of money we could
build a much bigger telescope on the ground.
So why launch things into space?
It's because the atmosphere is our enemy.
So the atmosphere does three very bad things which annoy astronomers.
The first thing is that it blocks some of the light.
Some particular wavelengths, for instance x-rays,
don't get through the atmosphere at all.
So in order to do x-ray astronomy, we have
to launch rockets into space there's, there's no choice.
The second bad thing that the atmosphere does is to distort
the light as it comes down through the atmosphere, it wiggles about.
And it blurs our images, so it means that our pictures are not sharp.
And that's the biggest reason why the Hubble space
telescope was put into space, is to take sharper pictures.
The third thing is that the atmosphere glows.
We're trying to see extremely faint things in astronomy and when there's
a background glare from the sky, it makes seeing faint things extremely hard.
So, even though space astronomy is expensive it
pays dividends once we get things up there.
We'll talk more about space astronomy
in week three.
[BLANK_AUDIO]
So, revolution number six is the one we're in right now.
That's the computer revolution.
So this started in the 1960s, but really started to take off in the 1980s.
Now remember we talked about photographic plate
here that enabled us to record images permanently.
And the modern version of that is the CCD detector.
But the additional thing about the CCD is that it's electronic.
So when you take the electronic signal, and we combine that
with a computer, it means that we store the information
as numbers on a computer.
Once they're numbers on a computer, we can do anything.
We can do calculations.
We can play with it.
We can just do just whatever we want to.
So that's when things really took off for computers.
Now at the same time, as the observers were playing with
their detectors and computers, the theorists
were going into computers, as well.
They took extremely big computers and ran calculations based on their theories
of how they thought the universe should look if their theories were correct.
They simulated entire universes and they're still doing that today.
And so a lot of astronomers do this.
This movie that you're looking at now is a simulation of
the universe made by the Virgo Consortium and the challenge is
to try and compare that, to our observations in the real
universe to try and work out, if the theories are correct.
So, the stage we're at now is trying to join together data sets,
including theoretical data sets, from across the whole worldwide
web and to turn them into one giant seamless whole.
And that challenge is known as the virtual observatory.
[BLANK_AUDIO]
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