Full transcript
0:00hi all welcome back this week we're
0:03looking at chapter six
0:04and specifically we'll be talking all
0:06about telescopes
0:07and the data we gather from telescopes
0:10what we do with it what we get even
0:12and why it's important and how these
0:14telescopes actually work
0:16so let's get right to it the thing is
0:20obviously we can look at the night sky
0:22you go out and depending on where you
0:24are you're going to see very different
0:25things
0:26for those of us in windsor if you are
0:28near the casino you're probably not
0:30seeing very many stars at all
0:32but if you were to go out in the county
0:34really far away from light
0:36you should see roughly 4 500 stars
0:40might depend on how good your vision is
0:42and how much again light is nearby but
0:44roughly we should see about 4 500 stars
0:47in our hemisphere
0:48and the other hemisphere should have
0:50another roughly 4 500 for a total of
0:52about 9 000 stars that could be seen
0:55from earth but there's a lot more stars
0:58than that
0:59so we're going to see we want to see
1:01more than that
1:03of course you can use a nice pair of
1:04binoculars if you have a good pair of
1:06nocturs you can see a lot more stars
1:08because we're increasing how far we can
1:11see
1:12but we've kind of alluded to it before
1:15and
1:15we are not the first group of people to
1:18get interested in looking at the sky
1:20humanity's been looking at the sky with
1:22wonder for
1:24well probably ever since we came about i
1:26mean it's this huge
1:27massive vault above us it's scary at
1:30times for some people
1:32and just amazing and in many cases
1:35there was a lot of religious symbolism
1:38around this
1:39and though there was other uses as well
1:44there's a lot of cultures we've talked
1:45about it a little bit in previous
1:46chapters
1:47they might have used it to help navigate
1:49the stars but also
1:51they had very simple devices if you will
1:54stonehenge right here is one nice
1:56example this was
1:57actually used to be able to keep track
1:59of the seasons
2:01basically a really big really heavy
2:04calendar by looking at the light and how
2:08it went through a certain part
2:09of these stones at certain times we
2:11could predict the seasons
2:13and again this is an important thing to
2:14be able to do when your livelihood
2:16depends on things like growing crops
2:19so being able to predict the seasons is
2:21a very important thing
2:22and one of the early uses of
2:26these kind of astronomical devices
2:28predicting the seasons
2:30of course now we have much more advanced
2:33much more expensive
2:34ways of studying the universe and the
2:37solar system around us the stars
2:40namely a telescope this is by far the
2:43most common though again if you
2:44are just interested in looking at the
2:46night sky and seeing
2:47some of the objects we talk about some
2:49of the planets you might be able to do
2:50that with a
2:51decent pair of binoculars so if you're
2:53interested you might want to check that
2:54out
2:55there's a lot of apps out there that'll
2:56help navigate you to a certain portion
2:58of the sky and say
2:59there's mars with a pair of binoculars
3:02you might be able to see them
3:03but most people of course use telescopes
3:06if they are available
3:07and the main idea of a telescope is that
3:10we're trying to gather as much
3:11light as much radiation as possible
3:14so gathering up as much radiation it
3:16might be visible light it might be
3:17another type
3:18of radiation but we're gathering as much
3:20radiation as possible
3:22and ideally we're bringing it to a focus
3:25we're going back to this idea of a focus
3:27in a second but basically
3:29making sure we get a clear image we want
3:32to be able to get a clear image so that
3:34we can actually
3:35view it or analyze it but
3:38it's worth noting and your book talks
3:40about this idea that a telescope is
3:42really only one of the three
3:43pieces we need for studying radiation
3:46when
3:47in the modern times when we want to
3:48study radiation a telescope is an
3:50important part
3:51it helps us gather the light but we also
3:55need some way of deciding and filtering
3:58the type of wavelength we want to study
4:00that's the second piece and the third
4:02piece is some sort of detector
4:05some way of actually seeing that image
4:08and it
4:08actually detecting the image produced
4:10now it might be that the detector is
4:12your human eye
4:14or it might be that it's something we're
4:17going to look at a little bit later to
4:18help us make digital images
4:20something very important for modern
4:21astronomy
4:24but when we're talking about a telescope
4:26the most common analogy
4:28a common analogy they use is the idea of
4:31a light bucket
4:32a light bucket and why does this make
4:35sense well if we have a
4:37bucket that we're trying to gather rain
4:38water in
4:40the bigger the bucket the more rain
4:42water we're going to gather
4:43you think the bigger the mouth of the
4:45bucket more rain can fall in
4:47and we're going to gather more water in
4:49a quicker time
4:50frame well a telescope is no different
4:53a telescope the mouth is now called an
4:56aperture
4:57that is the opening of our telescope and
4:59the thing is we want that aperture to be
5:01as big as possible
5:02bigger is better we want as big a
5:04telescope as possible
5:06because we want to gather as much
5:08photons of light as possible
5:10the bigger the aperture which is really
5:13the diameter of our telescope
5:16or the diameter of the opening of the
5:18telescope anyway
5:19the bigger that aperture is the better
5:21the more light we're going to gather
5:22the better the image we can get
5:26so bigger is most definitely better and
5:30i mean it's we're going to see there's
5:32more restrictions on it than just
5:34that but keep in mind we want these
5:36bigger apertures
5:38and that's really the diameter of the
5:40telescope
5:42but most telescopes will actually have a
5:44circular opening or aperture
5:47thus the area will actually depend on
5:50the square of the radius you think a
5:52circle
5:52the formula for the area is pi r squared
5:55so
5:56the amount of light that can be gathered
5:58the amount of area we have to gather
6:00that light depends on the radius
6:02squared which of course is just half the
6:04diameter
6:05so in other words if we can double
6:08the radius we are going to quadruple the
6:12area or get four times as much light
6:14being gathered
6:16so we very quickly increase how much
6:18light we can gather
6:20by increasing the size of the telescope
6:22that aperture
6:24and we can think that's one of the
6:26reasons why a telescope is so much
6:28better than just looking
6:29up at the night sky with your human eye
6:32even look at this image
6:34the human eye pretty small we can only
6:36gather a tiny bit of light a lot of the
6:38light just flows on by us
6:39other people are seeing that same object
6:42but with a even decent sized eight
6:46inch mirror of our telescope we'd be
6:49able to actually gather a lot more light
6:51and see a much
6:52clearer better image