Full transcript
0:00now over time these observations and
0:02these theories will get better and
0:04better we will actually be able to make
0:08a more solid theory as we see if the
0:10evidence fits it and eventually
0:12reinforces to a more solid theory and
0:14what we might end up with is a so-called
0:16scientific law something we believe to
0:19be true and it's again through many many
0:22observations many hypotheses many times
0:24that you will have something proved
0:26wrong and then revised theory over time
0:29and it will be many scientists over time
0:31often that lead to a better theory it's
0:33not often that one person manages to
0:36come up with a beautiful scientific law
0:38it takes revision over time and also it
0:42takes better equipment over time the
0:44scientific laws change over time because
0:46hey few hundred years ago we didn't have
0:49the kind of technology the observational
0:50techniques and telescopes we have now
0:52especially in astronomy so theories get
0:55better laws the scientific laws get
0:58better over time
0:59now one of the most important parts of
1:01these scientific laws is that we think
1:03they will also be true elsewhere not
1:07just near here sure we observe gravity
1:09here on earth and we've dropped things
1:10but we believed that same gravitational
1:13laws would apply elsewhere and we've
1:16been finding they do in our solar system
1:18but we also believe they'd be true in
1:20other solar systems other galaxies and
1:22this is incredibly important in
1:24astronomy because we're not gonna be
1:26going to these objects you're not gonna
1:28travel to another galaxy at least any
1:29time soon in fact you're not going to be
1:31travelling to another solar system any
1:33time soon unless our technology advances
1:36quite considerably so when we are
1:39observing and making conclusions about
1:42these distant objects we are doing it
1:44based on these scientific laws and it's
1:46because we know those same scientific
1:49laws should be applying there so when we
1:51use gravity to help us learn about a
1:54distant object maybe we use the
1:56gravitational pull of a planet and how
1:58it causes the faraway star to wobble
2:01well that's because we think Robbie
2:04works the same way there it should work
2:06the same way there so that's what's
2:08important about these laws is knowing
2:10that they will apply equally to these
2:11distant objects and
2:13thus we can actually learn about them as
2:16well even though we're not travelling to
2:17them and that's why we consider them
2:20universal laws these are universal laws
2:24because again they apply to these
2:26distant objects as well throughout the
2:29universe these laws are applied before
2:39we really started looking at some of the
2:41astronomy discoveries that have been
2:42made we have to look at how that might
2:45be reported how some numbers might be
2:47reported and how we actually learn about
2:50it and actually read it and one of the
2:52more important aspects is the idea of
2:54units units is what's reported kind of
2:58at the end of a measurement just like
3:00this one scale over here on the right
3:02I'll talk about that more in a second
3:04but units to tell you what it is you're
3:07measuring as a simple example let's say
3:10you were new to a city and you're trying
3:12to figure out how to get to school
3:14tomorrow and how much time to give
3:15yourself
3:15well if someone was to tell you yeah
3:18that's about 500 away
3:20they'll be useless by woodruff what away
3:24I mean are we talking 500 centimeters I
3:26mean you live next door and thus you can
3:28just walk on over to the school we're
3:30talking 500 kilometers in which case you
3:32probably moved to the wrong city because
3:34it's gonna take a really long time to
3:35get there or is it some other made-up
3:38unit maybe that's five hundred I don't
3:41know
3:41cat lengths from this person so you need
3:45to know what the units or what the
3:47actual scale of measure is and in
3:50science we use the SI units which is the
3:54system International which has been
3:57established and agreed upon by the kind
4:00of the world for most part I mean a lot
4:03of the when if you look down to South in
4:05America a lot of them still use some odd
4:07units but most people if you're
4:10reporting something in science you're
4:11using SI units which allows everyone to
4:14understand it and compare if one
4:17person's talking about meters someone
4:18else talking about meters it makes it
4:20easy to compare those two quantities
4:21because we know we just look at the
4:23numbers not having to worry about the
4:25units I mean you still report the units
4:27and that's where something like this
4:29Dumbo is useful because you can see it
4:31says 1 kg which dancer one kilogram
4:33which is the SI unit of measure for
4:36weight so we all know we're using the
4:39same units and that's important when
4:40comparing numbers and reporting results
4:43but in astronomy these numbers are
4:47usually huge and actually these two
4:49numbers I put on the slide are a great
4:50example of not having units and thus we
4:52have no idea what these are but in this
4:54case I just made up couple numbers to
4:56demonstrate the idea of scientific
4:58notation which is really just
5:02representing numbers in a different way
5:04in a condensed form if I look over on
5:07the left here and I'm gonna pull up the
5:09highlighter or the laser pointer look at
5:11this number this is some huge ugly big
5:13number well if I was to compare two
5:16really big ugly horrible numbers it'd be
5:19difficult I mean I'd have try and line
5:21them up and I might accidentally miss
5:23count the number of zeros and thus
5:25comparing two numbers would be more
5:26difficult because it'd be easy to make a
5:29mistake and it just also awkward it's so
5:31huge so what we do is condense it down
5:34using this idea of scientific notation
5:36basically it's representing a number in
5:39a different way rather than having this
5:41huge long number with many zeros we
5:43write it like this and these are
5:45equivalent because we've got this
5:47exponent here this 10 to the power of 24
5:50means we're gonna multiply this number
5:52by 1 with 24 zeroes after it and which
5:56would give us back this number right
5:58here but again it makes it much easier
6:02to compare if I was to compare two
6:04numbers and one was the power of 23 and
6:06one was power 24 it'd be very easy to
6:08tell that dot 224 is bigger so it's just
6:11another way of representing the number
6:13but how do we go about it well the power
6:16to 24 is actually just telling us how
6:19many decimal places we've moved the
6:21number over and in this case you don't
6:23actually see a decimal but remember it
6:25would be at the very end we could think
6:26of this as point 0 if we wanted so
6:29there's a decimal here and if we were to
6:30count over how many places that have to
6:33get to be here we could think 1 2 3 and
6:37keep going well 4
6:39six seven eight nine 10 11 12 13 14 15
6:4516 17 18 19 20 21 22 23 24 that's what
6:52this is telling us we have moved the
6:54decimal place 24 spots to the left so if
6:59it's a positive number we've moved the
7:00decimal place 24 spots to the left and
7:02again it's just a nicer way of
7:04representing it and with the scientific
7:06notation the way it works is we should
7:08have a number then a decimal just one
7:12number in front we shouldn't have it as
7:13450 we shouldn't have this written s a
7:16forty five point seven times ten to
7:18twenty three technically they'd be
7:20equivalent but in science we generally
7:22have this convention where it should
7:23just be one number and then the decimal
7:25but we can also use this scientific
7:28notation to represent very small numbers
7:30and that's what we've done over here you
7:32can see this is a very very tiny number
7:34many many places over to the decimal
7:37well you can see now the same scientific
7:39notation is used but it's a negative so
7:42now what we're doing the negative tells
7:43us how many decimal places it has moved
7:46to the right so in this case we'd be
7:48counting over and we'd find it's gone 13
7:51spots to line up here so scientific
7:54notation just allows us to write these
7:56really big numbers that were in a
7:58counter in astronomy in a much more
8:00succinct much more compact way making it
8:03easier to compare them and not having to
8:05write a ton of zeros