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People are going to ask, so this is here, and public, so I can point people at it.
I left the Maelstrom game part way through the latest event (Appropriation, Easter weekend 2012), and I don't particularly expect to be coming back. I have absolutely no hard feelings for the team at Profound Decisions (who are the company running Maelstrom), and I expect to continue playing Odyssey and am looking at Empire with interest.
The Maelstrom game I played for three years was a game of exploration and intrigue, and I played a character with some pretty serious emotional baggage and a past he wanted to escape. He came to the New World, found people of like mind and founded a church. It was a good life for a bit. Then, the rumblings of apocalypse sounded under the surface. For the next couple of games things got bleaker and darker, and my character and a load of others fought against it, and it was good fun. The Undead rose, my God told me to fight them, and I did so to the best of my ability. Then, on friday, three quarters of the characters I play with were either killed or driven off the field for the weekend.
All of the above is fine. Interfactional tension is a fine thing, and it's been simmering along, grounding in little scuffles and scraps for years. We've all been expecting a fight like that, half the field against the other half, and now it's happened. And it's just driven home that the game as it is now isn't really the game I want to play.
Two data points:
Maelstrom continues to be a great game. It's a different game from the one I started playing in 2009, and the game as it stands is not one I wish to play. So I'm leaving, and reallocating my time to games I enjoy more. See y'all on the field in the future.
So, it's been a while.
Three whole months since a useful entry, in fact. So it goes. As you may have guessed, Advent Science totally imploded fairly early on when I realised I really needed to write the sessions in advance, not on the night. I have no doubt it's possible to put out that volume of information each night for 24 days and have it be correct, complete and coherent, but I wasn't able to do it. Maybe next year I'll actually do the prep :)
Work is work, and continues apace. My department has me doing a lot of XSLT and Python at the moment, and I'm finding that the latter isn't the terrible language I was sure it was a while ago. Syntactic whitespace still bugs me somewhat, but at least it isn't Perl... It's maintaining my interest without any trouble, and while it's a really big job, it breaks down into small achievable sections such that I get a sense of progress, which is nice.
At home, the house is pretty much sorted out now, though it could use a spring-clean. Everything works, there isn't too much mess around and I'm slowly getting used to the idea of having a living room for, you know, living in. I still spend most of my time in my bedroom, which seems like a waste of a space. Have to address that.
LARP is mostly going well (although see the following post). CUTT will start back up soon, I'm looking forward to the next Odyssey game, and I await more details on Empire with interest.
Anything else? Not much of significance. I have a new bicycle, which is nice for the commute (the gears and brakes work properly!). It's a Raleigh Oakland in British Racing Green, with aftermarket Schwalbe Marathon Plus tyres. The latter have taken my puncture rate down from two or three a month to zero in three months, and I highly recommend them for use on harsh commutes. My commute isn't too bad: cross the river by footbridge, cycle along beside the Cam for a bit, cross Newmarket Road and then follow Coldhams Lane to Cherry Hinton, then down the High Street and left at the crossroads. Thirty minutes / four miles each way, which has to be good for me, and it's all the nicer now it's still light when I get out of work in the evening.
Hello again. In the last session, I talked a bit about electrons and charge, and tried to hook them up to concepts you're probably familiar with, like voltage and current. Now, I'm going to talk about conduction, and resistance, and semiconduction (this last being pretty vital for transistors, and the integrated circuits that are made out of them). I'm going to skim over them to some extent, because of all the material in this "course", the physics of conduction is the area in which I have least knowledge.
An atom, as I said in the last advent science session, can be considered as a nucleus (containing protons and neutrons) and a series of orbiting electrons. But those electrons don't all orbit at the same "altitude". It turns out that there are set "altitudes" (energy levels) at which electrons can orbit around the nucleus, and a certain number of electrons can fit in each. The energy levels aren't called energy levels for nothing, as an electron can move between them by gaining or losing energy - the more energy an electron has, the higher altitude it orbits around the nucleus, the higher its energy level. The terminology all kind of makes sense (although this is a massive simplification on the actual physics).
Different elements have different energy levels, and the spacing between the levels varies. The energy levels tend to be occupied from the nucleus out, as with time electrons will lose energy and fall inward to the lowest unoccupied level. An electron that has enough energy to transition to a higher level is said to be "excited". The highest energy level in which unexcited electrons are normally found for a particular element is called the Valence Band. The energy level immediately above it (which is "normally" empty of electrons) is called the Conduction Band. Electrons in this level can be exchanged between atoms moderately freely, as they are highly energised and loosely bound to their nucleus, but because electrons are drawn to positive ions (such as those created when an electron leaves an atom), it tends to be more a case of atoms swapping electrons with their neighbours than of electrons migrating freely around the material. As a rule, electrons in the Valence Band are too strongly fixed in place to move around like this.
As I said a while back, an electron must take in energy (and become excited) in order to step up to a higher energy level. This is ... mostly true. The trouble is, an energy level isn't just a single, clearly defined circle around a nucleus, it's a fuzzy band within which electrons can have one of several excitation levels, all very close together. So the bands can be different widths, and different elements have different distances between their bands... can you see where this is going?
CONDUCTORS are materials, such as metals, in which the valence band and the conduction band actually partially overlap. Electrons can swap in and out between the two bands freely. As a result, the conductor can be considered as a virtual sea of electrons, coexisting with a virtual sea of positive ions, despite the fact that the material as a whole is approximately neutral. Electrons within the conductor have a drift velocity (on the order of millimetres per second), which is the speed at which they move about, trading between atoms. Note, however, that electricity moves much more quickly than this (about 0.75 light-speed in vacuum). This is because electrons are traded, not moved - the whole thing behaves a bit like a Newton's Cradle. Push an electron in one end, and all the electrons jump forward one place in line, and an electron comes out the other end almost immediately. It's not the same electron, but it may as well be.
INSULATORS are materials, such as glass or rubber, in which the valence band and the conduction band are widely separated. Electrons need to gain a great deal of energy to move between bands, and they rarely manage it. As a result, attempting to push electrons in one end of a insulative material (or pull them out) has minimal effects, BUT it can cause charge buildup at the end. This is why insulative materials can hold a static charge - electrons are added to or removed from the material, but because it isn't conductive they can't go anywhere. The "not-electrons" that are left behind when electrons are removed are called Holes. They'll be useful later.
Finally, SEMICONDUCTORS are materials (like silicon) in which the valence band and the conduction band are close together. Electrons don't need a lot of energy to hop the gap, but they can't do it spontaneously. Semiconductors, it turns out, are really useful if you're smart in how you prepare them and lay them out - all integrated circuits are made from semiconductors. If a semiconductor is "doped" with other materials, it can be made to have a slight excess of electrons or holes, and when the two types of semiconductor are laid out in certain patterns, you can use a flow of electrons in one area to control the flow of electrons in a nearby area very precisely. But that's transistors, which is another session, yet to come.
I can't promise to post every day, as you've noticed, but I'm trying. The next session is on other fun particle physics trickery that's used in the field of electronics, then we'll move on to the actual machinery involved, starting with the transistor and moving on from there.
Hello, and welcome to Advent Science 2011, the pewterfish edition. This is a little experiment being performed by myself, pufferfish and duckbunny: we rather suspect we can teach our readership something interesting in the month of December, and we've each chosen a subject we know fairly well. It's kind of like an advent calendar, but each door conceals awesome knowledge instead of chocolate or paintings or Lego. Not that such things are bad, of course.
Pufferfish is talking about genetics, and duckbunny about the history of the atmosphere. In the next 24 days, I hope to lead you on a journey from science to engineering, and beyond, in one very narrow field.
Computers are everywhere these days, on our desks, in our pockets, in the back rooms behind companies like Google, and Facebook, and Oracle. They cook our food, wash our clothes, and guide our aircraft. But to many people, the computer is a magic box, a Thing within which humankind is not meant to peer.
That's nonsense. They're machines, just like everything else, the parts are just smaller and less obvious in function. I happen to know my way around them quite well, so I'm going to impart some of that knowledge to you, if you keep reading. I'll necessarily have to gloss over details from time to time, but I mean to touch everything important, and leave a trail of links for you to follow if you want to learn more.
Join me, then, as we wander from Electrons, to Email.
If we're going to go from Electrons to Email, I guess we'd better start at the beginning. Time for some particle physics.
The electron is a particle with a unit negative charge. That is, it is a particle with the smallest negative electrical charge known to exist - there's no such thing as "half an electron's worth of charge". An atom consists of protons and neutrons in the nucleus, and orbiting electrons: a proton has a unit positive charge, an uncharged atom has an equal number of protons in the nucleus as it has electrons orbiting it.
Opposites attract, as well we all know, and electrons are no different. Electrons, being negative, are drawn towards positively charged objects. But what's charge? It's the presence or absence of "the right number" of electrons. When I said that an uncharged atom has an equal number of electrons and protons a paragraph ago, I didn't mention what happened if the numbers weren't equal. If an atom has less electrons than protons, it is positively charged. If it has more, it is negatively charged. A charged atom is called an ion. Positive ions "want to" gain electrons, and achieve neutrality. Negative ions "want to" lose electrons. I put "want to" in quotes because there is, of course, no desire involved. Equally, it's not something I can easily explain without going deeper into partical physics than I really want to, so you kind of have to accept it.
Electrons are drawn to positively charged objects, and repelled by negatively charged objects. This is as true at the macroscopic level as it is at the atomic: a positive electrode will attract electrons, and negatively charged objects, to itself.
It follows that given a difference in charge, electrons will tend to flow from a negatively-charged object to a positively charged object, until the charges are equalised. This flow is called electricity. The chemical reactions within an AA battery cause one end to become more positive and the other more negative as they proceed, and it is possible to extract energy to light lamps, sound buzzers and so on by placing the item to be powered between the positive and negative ends: the electrons flow and, on their way, they power the item. Given enough time, the chemical reactions within the battery will cease as their fuel is consumed and the electrons will slowly drift back to equal out across the battery - this is what happens when a battery is discharged, or "flat".
The difference in charge between two objects is called the Voltage, or potential difference, that exists between them. The number of electrons per unit of time that flow between them is called the Current. Current is measured in Amperes, or "amps", and a single ampere is 6.241x10^18 electrons per second.
Given that that's an awful lot of electrons (roughly six quintillion), it should come as no surprise that in electronics, it is normal to deal with thousandths or millionths of an amp, or even smaller amounts.
So, that's the electron, more or less. I've glossed over some bits, because down at the tiny tiny scale of particle physics, it can be a bit too easy to get sucked down the rabbithole of detail, but that's enough that I can explain the next bit with. See you tomorrow.
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