A Photon from the Sun

Here's something rather interesting about the sun, and stars in general, in regard to light. A single photon (a particle of light) takes about 8 minutes and nineteen seconds to travel from the surface of the sun to the surface of the Earth. The photon, is, of course, traveling at the speed of light through space, and the earth is about 8.3 light-seconds away from the sun (and light travels at a staggering 670,600,000 miles per hour). However, after that photon is created at the center of the sun as a result of fusion at the sun's core, it takes somewhere between one hundred thousand to ten million years to make it to the sun's surface.

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How Empty is Space?

Oh, man, is space big. I get upset thinking about it sometimes. It's just too big (then again, my general reaction to the largest living thing on the planet, the General Sherman Tree, was to get angry). But it's not that space is just so large, it's also that it's so empty. And that is what I'm here to talk about today.

The visible universe is about 93 million light-years from one side to the other. That means we can see about 46 million or so light-years in any given direction, if we look hard enough (you'd need impossibly good eyes, though, or you could just use a really powerful telescope and also be in space because the atmosphere really gets in the way of seeing that far)...

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Quantum Entanglement

Oh what a tangled state we weave,
When first we practise to deceive!

(With apologies to Sir Walter Scott)

Quantum Entanglement. Spooky action at a distance. Quantum teleportation. Instantaneous transfer of information. Oh, man, does the science media love to talk about this. As does everyone who read a few articles and starts thinking of the wild possibilities. But quantum mechanics is a very, very tricky subject, which may be why I've held off on talking about it until now. No doubt someone will find something wrong with what I say, because I don't have any sort of advanced degree in the subject, and hoo boy is it complicated. Today, though. we're just going to talk about entanglement, one of the fun aspects of quantum mechanics that doesn't really mean what most people think, in its simplest form (because it gets complex fast)...

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Moon Facts

This week marks the 47th anniversary of the first human steps on the moon (July 20th, 1969), so we're going to celebrate with some cool physics facts (fizzix phacts) about the moon.

First of all, let's get a sense of how far away the moon is. On average, the moon is 238,855 miles away from us (384,400 km). That's all fine and dandy, but as humans, we're absolutely terrible at understanding very long distance, as I sort of covered with far larger distances previously. So, let's give ourselves a sense of scale...

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A Brief History of the Universe, Part I

Time is a tricky thing. The idea of the Big Bang has become common knowledge, but a question many still have as to the birth of the universe is what came "before" it, or indeed what was the "cause" of the Big Bang. While one might answer these questions with "nothing," that's not really correct, because the answer is actually much simpler and at the same time so much harder to grasp in any intuitive sense. The answer, which I understand intellectually but still makes no sense to me in an intuitive way, is that there was no before, nor a cause, because time itself, which the idea of before and causation is predicated upon, began its existence synchronously with the Big Bang. I find this nearly impossible to grasp in a fundamental way, because our entire existence is based around and upon a notion of time as a strict linear progression of one thing to another, with every event having a causation and time preceding it.

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The Galaxy's Dark Secret

Let's talk a little bit about our galaxy. You probably know that it's a spiral galaxy, with several "arms" reaching out from a central bulge, and is shaped like a disk. Most of our galaxy's mass is centered in that central bulge, with is about 13,000 light-years from top to bottom (which is really, really big), and has a density of around 1,600 stars per cubic light-year. To put that in perspective, out where we are in the Milky Way it's only a few thousand light-years thick (which is still really big), and the stellar density is closer to 0.004 stars per cubic light-year.

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It's About Time

Time is a funny thing. It's passage may seem constant, but it totally isn't. And I'm not just talking about how boring or tedious days drag by. See, this pretty obscure physicist by the name of Albert Einstein managed to codify a new area of physics back in the early 1900's which we call Special Relativity. He was the main reason the idea of the luminiferous aether (which I talked about in my post on Light) was discarded, because it showed the speed of light to be an absolute, universal constant, regardless of reference frame. Which is cool and all, but what does light have to do with time?

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All These Other Planets

For a long time (well, relatively) astronomers believed they had this whole "solar system" thing figured out. They had this theory which governed its formation, called the "core-accretion theory," which described stellar and planetary formation. Basically, as all the dust and gasses that make up a star star coalescing into a star, they also begin spinning. As they spin faster, the gasses condense into a kind of spinning disk which is thicker at the center (like spinning our a blob of pizza dough, but a lot more complicated). Finally, this central mass gets hot and dense enough to trigger fusion, and the proto-star becomes a real star. Around this time, as the star is finishing its formation, the heavier elements in the spinning disk start clumping together, with the denser elements forming the smaller, rocky planets we see as the "inner planets" in our solar system, and lighter elements and compounds forming gas giants further out.

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The Cat is Out of the Box

Many of you have probably heard of the thought experiment known as Schrödinger's Cat. The basic premise of it is that you have a cat in a box. Also inside that box are a flask of poison gas, a radioactive element, and a detector hooked up to a small hammer to smash the flask. Now, if the radioactive element, well, radiates, the detector will detect it, smash the flask, and the poison will kill the cat. It is important to note that this experiment has never been performed, and actually performing it may get you labeled as a psychopath (or just someone who really, really hates cats). While the box is sealed, there is no way for an observed to know if the cat is alive or dead—that is, if the radioactive element has triggered the detector. The goal behind this experiment is the idea that, at some point during this experiment, the cat is both alive and dead—that is, a superposition of those states. Erwin Schrödinger himself came up with this scenario to demonstrate...

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Some Light Reading

Light is maybe one of the more important things in the universe (though this is debateable—some sensible people rank chocolate above it). It also has a rich history of people not really knowing what it was, how fast it moves, or even how it moves. So, in order to better understand it, let's turn back time, and cover a bit of light history (these puns never get old).

For a very long time, people believed light to be instantaneous, and for good reason. When is the last time you could see light move from place to place? Some folks disagreed, including a man born on February 15th in 1564 by the name of Galileo Galilei. Galileo attempted to measure the speed of light much like one might measure the speed of sound. In fact, you and another person could get a rudimentary measurement of the speed of sound using this method, so let's cover the sound applications first:

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