Notes: The discovery of Uranus, Neptune, and Pluto

Let's take stock. We started out confident in our belief that it was just us, Sol, Luna and the fireflies. Now, we have knocked ourselves down a few pegs. We're not in the centre of the universe, there are other things orbiting the Sun (and not us, the bastards) and we have a bunch of equations that tell us how they move. We also have a brilliant device using lenses and tubes that let us see these things much more easily. Yes, telescopes were a particularly brilliant invention. They allowed us to observe the sky with unprecedented accuracy. Looking around our 5 neighbouring planets, the Moon, the stars, that odd comet...Yes, that one. No, it's definitely a comet, I'm sure. No, no tail as of yet but it's a comet, I'm certain of it.

Comet.

The discovery of Uranus is quite a pleasant one as it happens. It had been seen so very many times over the years but most put it down as being a star. Then a German fellow going by the name William Herschel moved to England, built himself a telescope and had a marvellous time with it until one March night in 1781 he noticed a fuzzy thing and thought to himself "Ah, a comet". Specifically he noted

"In the quartile near ζ Tauri ... either [a] Nebulous star or perhaps a comet"

He claimed as much to the Royal Society and the Astronomer Royal, the latter replying to him not knowing what to call it at all.

 "I don't know what to call it. It is as likely to be a regular planet moving in an orbit nearly circular to the sun as a Comet moving in a very eccentric ellipsis. I have not yet seen any coma or tail to it

Herschel continued to refer to it as a comet, albeit cautiously. By the end of the year however he had concluded that, as others had already begun to suspect, it was a new planet. The happy ending to this story, King George III threw money at Herschel on the condition that he move to Windsor and let the Royal family have a look through his telescopes. There is some more drama to be had about it's name but I'll let you discover that for yourself. It was discovered to have a really very long orbital period. 84 of our Earth years, in fact. Further observation also unearthed some rather interesting data. There was some anomalous factor in the orbit. Now we have dealt with this before. Something is going against our view of the universe and we need to sort it out. Thus we come up with some possible explanations:

• Poor quality observations. This is the favourite of the theorists. Those bloody experimentalists fucking up the data collection. Look at it again, our way is law. Newton's Law.
• Does the gravitational force really obey the inverse square law? Yes, on the other side of the coin, could it be the theorists at fault? Certainly this has been true before. Remember geocentricism, eh theorists? Yeah, choke on that.

Theorists and experimentalists are like that, in the same harmless way that Physicists pick on Chemists pick on Biologists for being a somehow lower form of science. And everyone picks on Psychology. Anyway, the debate raged on, until a couple of people, one French Urbain Jean Joseph le Verrier, one English John Couch Adams, proposed another idea. What if there is another planet, beyond Uranus, who's gravitational force was affecting the orbit of Uranus? Calculations were made, observations done, and low and behold, a "star" making planet like motions was observed. Le Verrier, being the one who actually saw the bloody thing (Seems that Adams did something of a hash job with his data) called it Neptune, and after years of debate, the credit was split between the two. Thus, in some small way, two nemeses came closer, as people, as humans. Yes, we the British could focus on making everyone else hate us instead.

Once again did history repeat itself, it seems, as Neptune's orbit also did not seem to conform to expectation. Ah, but we knew the tricks now. A new "Planet X" was predicted (Planet IX, surely), and eventually, in 1930 something was found. It was named, adorably, by an 11 year old schoolgirl with an enthusiasm for both astronomy and classical mythology. Venetia Burney figured that the name of the god of the underworld was an apt name for such a cold, dark planet. After the name was chosen by unanimous vote Venetia received £5 for her trouble. Adjusted, that is roughly £234 of our Pounds Sterling. Given to an 11 year old.

Fair play

Incidentally, it should be noted that the apparent mass of Pluto was no way near what would have been required to mess with Neptune's orbit. No, Pluto was not the Planet X everyone was looking for. A search for a 10th planet was made but this was all but abandoned following the discovery that the discrepancies in Neptune's orbit were due to a slight overestimation of it's mass. An overestimation of 0.05% in fact, comparable to the entire mass of Mars.

I would like to end the post by reminding everyone that 2012 is not yet over, and there is still every chance that our modern day Planet X, aka Nibiru will swing through the the solar system fucking some serious shit up as it goes before the year is out. Ignore any of those "scientists" or "astronomers" who might tell you that it is kind of impossible for it to actually exist. They're all just in on the conspiracy.

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Notes: Kepler's Laws and the Repercussions

Now where were we? As yes. Imagine you're an avid 16th century astronomer. You make extensive observations of the positions of the planets, and have a fairly comprehensive view of it all. You're even pro-copernicus, though having taken such staggeringly accurate data this isn't much of a surprise. Unfortunately you're also a bit protective of your work (Not an unreasonable stance during the time)  so you don't really tell anyone about it. Congratulations, you're Tycho Brahe. Good news, you have a bitching moustache, and your assistant uses your data to come up with a set of laws that would revolutionise astronomy. Bad news, he does so after you die from a kidney/bladder ailment having refused to go to the toilet at a banquet because it would have been a breach of etiquette. Or you were poisoned with mercury, so there's that.

Speculation aside, your assistant, Johannes Kepler now has access to your lab and notes, and man does he go to town. Within a couple of decades of Tycho's death he had worked out 3 laws of planetary motion:

           1. Planets orbit the sun in ellipses with the sun at one focus

Some maths now. An ellipse, in layman's terms, is a squished circle. If that's good enough for you then just go ahead to the second law now. See you there in a bit.

Mathematically, an ellipse is a set of points that satisfies the equation:

• ^x2⁄_a² + ^y2⁄_b² = 1

Ellipses have an eccentricity 'e', which is basically to what degree they are squished.

• e ≡ √1 - ^b2⁄_a²

Do please ignore the godawful overline job there. That's meant to be all square rooted. But as you can see, if  a=b then eccentricity is 0, and you get a circle. On the other hand as e approaches 1, through oversized a or undersized b, then we're more or less getting a line.

Here is the eccentricity of the planets we've discovered so far:

Earth - 0.017
Venus - 0.007
Mars - 0.093
Jupiter - 0.048
Saturn - 0.056
Mercury - 0.206

Clearly most of our neighbours are fairly normal. Venus is practically Ned Flanders. Mercury on the other hand is down right ovular in it's travels, and this was something that had baffled astronomers who had previously believed that everything moved around in nice polite circles.

This was the equivalent of not thanking someone after they hold a door open for you.

         2. "Equal area" is swept out in "equal time".

This one is simple enough. See the orbit below?

During a value of time t, wherever the planet is in the orbit, the area cleared between it and the star will be area A. Next.

         3. The relationship between period p and distance from the star is:

a³ = p²

^{There's not much more to say on that matter so have some data on it.}

Ah but I wish you could make decent tables in Blogger. 

Now I've already said a lot on the subject of Galileo and his life including the fact that he didn't invent the telescope, as is so often claimed. Thus I shall not dwell for too long on such matters. I did mention that he made a number of discoveries with his telescope however, and I shall briefly expand upon a few of them.

• He discovered mountains on our own moon.
• He had a good look at the celestial Thursday that is Jupiter, and observed that it had four moons of it's own; Io, Europa, Ganymede, and Callisto. These are known as, understandably, the Galilean moons.
• He worked out that the moons satisfy a "Kepler-like orbit", that is to say that the cube of the distance between them and Jupiter is proportional to the square of the orbital period.

All in all everything he discovered kinda fought against the idea of geocentricism. After that, well, like I say, I've gone into it already. Let's briefly move onto someone New...ton.

Sorry. Anyway, Kepler's laws were pretty observation based. They worked, absolutely, but the maths behind it was lacking. So the story goes, having had a crack at it himself this bloke called Christopher Wren made what is known in the business as a Scientific Wager, offering 40 shillings to anyone who could deduce Kepler's Laws from the inverse square law. Alas, while Newton had a stab at it, by the time he had finished he was too late. His only consolation was that his work grew into one of, if not the most important pieces of work in science. The 40 shillings would have been nice though.

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Notes: Epicycles and Planetary Orbits

So far you're pretty sure that you're place is the centre of the universe, and that means that everything in the sky is circling you, as well it should, god's own image, Joshua 10:13 etc etc. However you found something that didn't quite agree with that. The strange wandering stars were moving in a way that didn't exactly suggest  a nice clean orbit around us. So you did what anyone who's sense of place in creation was threatened would do. You made it fit your theory.

What you decide is that the planets are still orbiting you, calling that orbit the deferent, however they're also moving in small circles around that deferent. You call these little circles epicycles, literally 'on the circle'. Alright, everything is sorted. These circles account nicely for the changes in direction, velocity and what not that these planets take when orbiting you.

Source

Except they'd go out and observe a bit more and it didn't quite fit. So they'd add more epicycles. Still not quite right. More epicycles! Still no? Just keep changing stuff until it fits our established theory gorramit!

These days epicycles is something of a swearword in science. I can tell you this with certainty because two lecturers in entirely different parts of the world have told me just that. If a theory comes along that builds into something really unnecessarily and ridiculously complicated it may well be compared to epicycles. Then someone gets punched.

Incidentally, this is where one of those fables I keep writing about come in. In fact this is the first one in that first lecture series where I got the whole idea. Basically the idea that they kept making things more complicated is true, but they didn't so much keep adding epicycles as they did arbitrarily change the velocities of the planets, or make the epicycles move side to side, anything that might help get it to work. The end result is the same though. An arcane mess of a theory that you just want to curl up and ignore.

Kitten break.

So you do. You decide you're fed up with this nonsense. Clearly something is wrong, and a new theory is needed. So thought a fellow named Copernicus, who had a look at the data and thought "Ok, this needs some work". So he proposed Heliocentric cosmology, and published his theory in a book called De revolutionibus orbium coelestium, On the Revolutions of the Heavenly Spheres. Initially it didn't sell so well. Copernicus has made it really rather technical, so that only the most learned of astronomers could really understand it. This allowed it to disseminate into their ranks before it roused any of the more zealous geocentric types. Eventually however it did become fairly popular, enough so that the pope had it put on the Index of Forbidden Books in 1616. Copernicus didn't really mind so much at the time, though mainly because he was dead. Probably best. If he was still alive when it was banned he might have been taught the error of his ways, as it were. And then died.

Now this theory works, you think, though probably only in your head, lest you be put on trial for heretical thinking or whatever. It fits the data. The planets all orbit in the same direction, the outer planets take ages to get anywhere, everything fits. What this also means is that we can take a decent stab at working out how far away the other planets are:

I'm tired, hungry, and have been at this all day. You be happy with my illegible scribbles.

So finally, we have some proper idea of our universe. There's us orbiting the sun, along with other planets, and the fireflies that got stuck up on that big bluish black thing.

Next time, the uneventful adventures of Tycho Brahe.

Not that one.

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Notes: Stars and Planets

So far we have made some basic observations, and come to a conclusion about our place in the universe that, as far as we're concerned, is flawless, and frankly kind of gratifying. Centre of the universe huh? Who'd have guessed it. Enough back patting for now though, we have more looking at stuff to do.

For example, the fathomless depths of my eyes.

You may have noticed that while the moon is floating about, it's joined by a bunch of other tiny points of light. To save you the trouble of counting I will tell you now that there are roughly 4000 stars visible to the naked eye. Almost all of these move across the sky in a fixed pattern that, if you were of a type, you might want to sort into patterns and what not.

I am momentarily amused that iTunes, in an act of solidarity has just shuffled in Metallica's 'Orion'. Simple things. Excellent track though.

Alas, things are not as perfect as you might have liked. There are 5 points that don't seem to want to stay in place with the rest. And because you're an ancient Greek, you go ahead and call them astēr planētēs which sounds lovely until you realise it literally means 'Wandering star'. You decide to stick with 'planets' because you're English now and frankly we seem to have a properly hard time not nicking other cultures' words. They are named:

• Mercury
• Venus
• Mars
• Jupiter
• Saturn

Now I'd like to point a little something out. It's not quite so obvious in English where our days of the week are fairly Germanic in origin (There is something quite enjoyable about going to lectures on 'Thor's Day') but some of you may know the more Latin based, French  Check out their names for the days of the week starting on Monday:

• Lundi
• Mardi
• Mercidi
• Jeudi
• Vendredi

Now switch back to English for the weekend and we have:

• Saturday
• Sunday

It all has the same kind of root which is why I'm being fairly inconsistent with language. Point is that our 7 day week is based on the 7 key objects observable in the sky with the naked eye. Some languages name them with their Germanic roots, some Latin, some Gaelic, but on the whole they're all from the same thing, showing just how far back this astronomy business goes.

Right, enough linguistics¹. Back to the observational SCIENCE! So, these wanderers pique your curiosity, and you devote some time to observing them. What you notice is odd. They really do wander, sometimes completely randomly.

A composite view of Mars from Earth

It looped. Mars bloody looped around in the sky. This is nuts. This completely goes against your world view. Everything is meant to be nicely orbiting us and there is Mars pissing off doing it's own thing. What a wanker.  But nonetheless, you have new data to be interpreted. If it's not circling around us neatly it can only mean one thing.

Epicycles.

[1] If I wasn't a physicist I would absolutely go into studying linguistics and etymologies and what not, and not just so I could make hi-LAR-ious oral sex jokes.

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Notes: The Moon

Back onto the astronomy thing. As mentioned last time, we are moving onto the second most obvious thing in the sky, The Moon.

To begin with, it's worth knowing a little about something called the ecliptic. This is basically the path the sun took during the day. Secondly, you need to know that everything has an angular position. There is a brilliant rule of thumb for this. I urge you to try it, it works for damn near everyone. Simply hold your arm out in front of you, with your hand up straight, like a traffic cop telling you to stop or something. Your finger is roughly 1°. With this in mind, know that the Moon can be found within 5° of the ecliptic.

Incidentally, both the Moon and the sun are roughly 0.5°, meaning you can more or less cover them with one finger, though if you want to test this one I'd recommend trying it on the Moon first. The Sun is very formal, and pointing is quite rude.

Alright, so you see the Moon, you observe it over some time, and you notice it changes shape with a certain regularity. These are called the phases of the moon and proceed like so:

Incidentally, in the same manner as with Dara O'Brien's slip up, I had my reservations about the accuracy of this particular advert that some of you may remember from our youth.

That clearly should be "Full moon, Waning crescent, No moon", but I guess marketing departments have no time for scientific accuracy.

Anyway, distraction aside, this cycle repeats itself more or less every 29 days.

Interpretation of the Data

Ok, so you're a blank sheet of potential human observation. Telescopes and what not have yet to be invented and all you have seen so far is the Sun and the Moon, going around and around in an eternal game of celestial kiss chase, one full of fiery passion, the other kinda turning invisible half the time. I don't know, I never played kiss chase.

Using this data you try to craft a model of the universe, and eventually settle on one that fits your Sun-Moon-Earth data perfectly. Thus came about the Ptolemiac system, from which arose much of Geocentric cosmology, a view that persisted for a good 1400 years, and one that has clouded much of western philosophy, religion and science.

This incidentally is fine. It's all very well to look back and scoff about how uneducated past folk are, but do remember that given the data they had, this view fit perfectly  They were using what we might now call a "non-inertial reference frame", which in this case is kind of a nice way of saying they didn't know the Earth was also moving.

I'm not strictly holding to the lecture by lecture notes thing at this point instead opting to separate them into similar sub-subjects. So, I'll cut these notes half way through and next time I'll say a little about stars and what not.

Now if you'll excuse me, I need to go buy some Jaffa Cakes.

Heaven.

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Notes: The Sun

Part of what makes science kinda great is that it's constantly being worked on and improved, tempered in the forges of experimentation. Astronomy is one of those odd sciences, in that we can't exactly go out and do that. Going up to stars and measuring stuff poses certain logistical problems. So instead what we do is look at stuff. A whole lot. And would you believe that looking at stuff is really gorram interesting? Think about it, it's one of the oldest sciences and it still has a pretty massive presence. Something about the vast expanse of unknown is still sparking the old human curiosity...thing.

Ok, so let's explore what we can observe with just our naked eyes. I mean let's face it, not everyone has an awesome 8" reflective equatorial telescope. And while that is a shame, it's not the end of the world.

For starters if you look up during the day, and are not in Wales, then you may see an incredibly bright thing. We call this The Sun, or Sol, if you're the kind of person who calls the Earth Terra in casual conversation. If you give it a while, you may also notice that the sun takes a path across, and further careful observation reveals that the path the sun takes is a little different every day. In fact this happens all year around, the path being a little bit shorter each day at this time of year until the 23rd of December, or the Winter Solstice.

Source

Side note: You may notice that that is a fairly familiar date. That is no coincidence. Fun fact, the Bible doesn't actually give a specific date for Jesus' birth. Thing is that at their most expansionist, the Roman Catholics decided they needed a date to celebrate the event of their saviour's birth, and they also wanted to get rid of the pagan celebrations of the solstice. And as my lecturer so put it, you don't get popular by cancelling parties. So, the logical thing to do was to co-opt the existing "unholy" celebrations for their own righteous and godly one.

Ok, so that's one glowy orb seen, how about the other? During the night, when they sky is arguably at it's most stunning we have the bright white disk we call the Moon, and that's what we shall cover next time.

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