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Let's Talk Physics | Ethical Biscuit

Let's Talk Physics

Rutherford Scattering

Let’s start by going on a journey through time. And possibly space, because what I’m going to talk about took place in a particular locale. Anyway, we’re in the year 1909. Atoms are pretty much the bomb, but no one really knows that much about them. They know that there are positive and negative charges in them, because Ben Franklin said so (simplification), but the prevailing theory at the time was what was called the “plum-pudding” model: the charges were distributes more or less evenly throughout the structure. If you’ve made it through some science today, you know that they were dead wrong, and it’s ok to laugh at them, because it’s fun to laugh at people when they’re wrong. But, since no one had eyes good enough to see how atoms were composed, they were just basing it on what amounted to a wild-ass guess.

Enter Hans Geiger and Ernest Marsden. In Ernest Rutherford’s laboratory (Ernest was just a great name to have then. There was tremendous importance placed upon being Ernest) they used a radioactive isotope to shoot alpha particles (which are just Helium nuclei—so only positive charges, not electrons) at a really, really, really thin sheet of gold foil. Why gold, you ask? Well, no one had come up with a way of making aluminium cheap and malleable like we have today. That wouldn’t come about for a long time, and they used tin before that, which was rather difficult to work with (but the name “tin foil” has obviously stuck). Either way, the gold foil was a good idea because gold is pretty damn dense. And, what Geiger and Marsden noticed was that not all the alpha particles were making it through the gold.

This, of course, surprised absolutely no one, because if you shoot particles at something, you don’t expect them all to make it through. If you throw sand at a screen door, some of it will be stopped, even though all of it could technically make it through the spaces. This is the sam

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Distances in Space

One thing you should know about space: it's huge. Mind-bogglingly huge. If you were to think of the biggest thing you could possibly image, it would still be more than a billion times bigger than that (and don't say you imagined infinity, because you can't. And stop being clever). The problem with just saying "the universe is huge" is that it doesn't really convey the distances involved. We can talk all we want about light-years and parsecs (unit of distance, not time, sorry George Lucas), but it doesn't really mean much. They're just words. And, as wonderfully evolved as language is, a lot of scientific terms fail to covey conceptual content with them, because our brains simply didn't evolve to deal with this sort of stuff. So today, I'm going to try to take a stab at this comprehension, let's see if you can follow.

How far away is the Sun? Well, you could say it's one Astronomical Unit (AU), or that it's about 150 million kilometers, or about 93 million miles. Well, those are big numbers, but they really don't paint much of a picture. Even saying that the Sun is actually 860,000 miles across, but only appears to be about the size of a quarter because we're so far away doesn't help. So let's undergo a gedankenexperiment (a thought experiment): Let's say that you have decided to go on a vacation with your family to the sun, because you operate on the principle that the ideas you have at 2 am are completely reasonable. Lucky for you, the highway committee also operates on the same principle, and just recently built, at great expense and headaches, a highway straight to the sun. The toll's outrageous, but you can still drive there. Let's assume that the highway is the same boring sort of highway we see normally in America, with a speed limit of 65 mph. Let's also assume that you drive on it much like you drive on a normal hi

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Black Holes

A black hole is a misnomer. It is neither a hole, nor is it technically black. The primitive name for them, “Dark Stars,” would be technically more accurate, but not as sci-fi sounding. Here’s the best way to think about a black hole:

Picture yourself on the surface of the Earth (should be easy). Now, if you were to toss something up in the air, it would be pulled back down due to gravity. Obviously, if you were to toss it with a large enough initial velocity, it could escape the Earth’s gravity (this is called escape velocity). Now, let’s say the mass of the Earth was just increased to that of Jupiter, but the size is still the same. Now the gravity is inordinately larger, and, in the instant before you become liquefied by it, you notice that the initial velocity of an object would have to be even higher to escape here. Now, you could keep increasing the mass of the planet without increasing the radius, and eventually reach a mass where, at the radius you are at, the escape velocity needed exceeds the speed of light. If you were to shine a light upwards from the surface at that point, it would never be seen outside the planet. You are now inside a black hole (you are also dead).

See, every massive body (read: a body that has mass) in the universe has what is called a Schwarzschild Radius. This is the radius at which the escape velocity of the body is greater than the speed of light. For a relatively small (mass-wise) body like the Earth, that radius is minuscule. However, the technical definition of a black hole is a body whose Schwarzschild Radius is greater than its actual radius—that is, the radius at which light cannot escape is further out than the surface of the body. This radius is also called the black hole’s Event Horizon, the “invisible” line which denotes the beginning of the black hole. The mass itself is called a singularity, a tiny point of insanely huge density. To in

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