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The Most Energetic Mystery in the Universe

March 25, 2009 on 1:05 pm | In Astronomy, Physics, black holes | 25 Comments

When we look out at galaxies, we find the most energetic particles we’ve ever found anywhere in the Universe coming from their centers. Why?

Because as far as we can tell, all galaxies, at their centers, have huge, supermassive black holes! When matter (like a star, globular cluster, intra-galactic gas, etc.) gets too close to one of these black holes, it gets ripped apart, and settles into a disk around the black hole. This disk is called an accretion disk:

Like everything in a strong gravitational field that moves, these particles radiate (give off high-energy photons), fall in towards the center of the black hole, and sometimes get accelerated and shot out of the galaxy!

For a galaxy like ours, with a black hole a few million times as massive as our Sun, we can get extremely energetic particles out: up to 1018 eV, which is 70,000 times more energetic than the LHC!

But our black hole is kind of a commoner — a weakling, even — when you look at other galaxies. There are huge galaxies out there, such as active galaxies and quasars, where instead of a few million times as massive as our Sun, their black holes are billions or even tens of billions times as massive as our Sun:

Well, in theory, the energies of these particles can be thousands or even tens of thousands of times higher than what our galaxy can produce! We’re talking about energies of 1022 eV, which is not only insane, it’s impossible!

Why? Because there’s a maximum energy that particles traveling through the Universe can have. There’s a bath of leftover light from the Big Bang permeating the entire Universe: the CMB. If you smash a particle with too much energy into one of these CMB photons (which is unavoidable as you travel millions of light years), it causes these high-energy particles to slow down until they’re below the “speed limit”. (Okay, it’s an energy limit, but it’s really close enough.)

And unlike cops that pull you over, the light that fills outer space slows you down until you’re below the cosmic energy limit: 5.7 x 1019 eV. Well, do we see a cutoff there?

Maybe. The AGASA experiment says no, there is no cutoff, but the Pierre Auger Observatory says yes, there is one. Who’s right? On one hand, we’ve definitely seen events where we’ve measured more energy than should be allowed. It may mean our theories need revising, or it may mean that there’s something super-energetic happening in our own backyard that we don’t know about. Or — on the other, more boring hand — perhaps we’ve just done a bad job of measuring things at very high energies. Whatever the case, explaining these events that exceed the cosmic energy limit of the Universe is, in fact, the most energetic mystery in the Universe!


Between Bird and Mammal Lies the 6th Sense…

March 23, 2009 on 1:45 pm | In Evolution, Life | 37 Comments

This Australian “mammal” is one of the most bizarre creatures on Earth, having many of the characteristics usually reserved for either birds only or mammals only:

Ladies and gentlemen, the duck-billed platypus! Its most notable features are as follows:

1. It lays eggs. This is usually reserved exclusively for birds, reptiles, dinosaurs, etc. And these eggs are tiny! Mammals gestate with the eggs inside of them, giving birth to live young, but here’s a mammal that lays eggs!

2. It’s furry. Like mammals are — no feathers for this guy — the platypus is not only covered in fur, it’s got such a nice coat that it has historically been hunted for its fur!

3. It is venomous! This is extremely rare for mammals, and the platypus itself has three venomous compounds in it that are unique in all of nature to the platypus itself. The venom is emitted through a spur in the platypus’ foot, right around its ankle. And speaking of feet…

4. It has otter-like feet. Totally mammalian, you got it. On the other hand…

5. It has a duck-like bill. Totally bird-like, of course. On the other hand…

6. It has a beaver-like tail. Mammalian, I got it. I suppose we can go on and on, listing all the ways this animal is neither bird nor mammal, all of which I find fascinating. But this animal can do something that you and I cannot, no matter how hard we try. Your skin, your epidermal layer, is fantastic for sensing temperature, pressure, and pain. These three types of sensor suit us remarkably well, and allow us to experience all sorts of interesting sensations, like itch and ticklishness. But the platypus has us beat, because in addition to these, the platypus can detect electricity!

That’s right, the duck-billed platypus has the most sophisticated sense of “electroreception” of any mammal, allowing it to track its aquatic prey by locating where an electrical stimulus resulting from muscle contraction came from. Normally, we only see this in predatory fish, like I’ll show you in the image below:

But here it is, in a platypus! How cool of a sense is that?! So the next time someone tells you about “the sixth sense,” don’t think of ESP and don’t think of Bruce Willis, think about the platypus, an animal with a real sixth sense: the ability to detect electricity!

Because I want a sense like that…


Weekend Diversion: f my life

March 22, 2009 on 11:16 am | In Random Stuff | 12 Comments

Schadenfreude (IPA: [ˈʃaːdənˌfʁɔʏ̯də]) — largely unanticipated delight in the suffering of another which is cognized as trivial and/or appropriate.

Every once in awhile, everyone has a bad day. I had one on Wednesday, where nothing seemed to go right the entire day. And sometimes, immature though it is, it just makes you feel like you’re not alone when you realize that other people are having lousy days as well. Some of those people’s days get so bad they’re absurd, and when that happens, it can even make you laugh! Right, Nelson?

Well, I’d like to introduce you to the newest addition to my links section — fmylife.com — where you can get your daily dose of schadenfreude in categories such as love, money, kids, work, and health. You can also vote on whether the person deserves your sympathy or whether they got exactly what they deserved. Some of them are sad, some of them are disgusting, and some of them just make you squirm. And some of them really make you think, “Man, I’m glad that’s not me.”

Today, I saw an elderly man fall in a crosswalk, so I jumped off my bike to help. As I helped him across, the light turned green. At that point I noticed my phone had fallen out of my pocket in the street and was run over by several cars. I then watched across a 6 lane street as someone stole my bike.

Today, I was reported to my principal because someone caught me shooting up at the cafeteria lunch table and as a result I have been suspended from school. I am a diabetic, I was giving myself insulin before I ate crappy school food.

Today, I texted my college boyfriend to tell him how terrible I felt about cheating. He replied saying he was so relieved because he had been cheating on me with a girl in his dorm. I was talking about my math exam.

And some of them make you think, “Wow, you’re a total fool, and this is your comeuppance!”

Today, I was a TA for a history class and the class was taking a test. About halfway through, I noticed one kid had a small piece of paper in his hand. I ran up the row, grabbed his test, and ripped it into four pieces. Then I took the note from him. It said “I believe in you, -Mom.”

Today, I went to a movie with my boyfriend. In the lobby, I asked why the glasses were not working. I said, “Do they only work inside the theater?” My boyfriend replied, “3-D glasses just work inside the movie, everything else in the World is pretty much 3-D.”

Today, my mom came to me and asked if I had drank her wine. I’m 16, so I lied and said “no”. The next morning there was a DVD on my bed labeled “pool house security cameras- love mom.” It was a video of me downing two bottles of red wine and having sex with my boyfriend.

And for whatever that says about me, sometimes it makes me feel a little bit better for having read these. Have a great, schadenfreude-filled weekend!


A Little Sun in Your Life… Dire Consequences?

March 20, 2009 on 1:18 pm | In Astronomy, Physics | 20 Comments

I really get a kick out of reading The Straight Dope. What started as a weekly column in a Chicago newspaper has grown into a nationwide phenomenon and a small empire, and is often full of fascinating questions and extremely well-researched and knowledgeable answers.

But doesn’t anyone there know to contact me if you’ve got an astrophysics question? Today’s column, which will be nationally syndicated, declares that they cannot answer the following question:

If the pink grapefruit sitting in my fruit bowl spontaneously turned into a grapefruit-sized sun, what would happen to my flat, London, and the rest of the world? If I put it somewhere safe, could I enjoy not paying for central heating? Or would it end life as we know it by melting through my floor, into the African textile shop, through the subway system, and finally to a fiery chasm in the middle of the earth where it would make all volcanoes erupt and kill everything, before coming out the other side and changing the way all the planets spin?

Well, I may be no Cecil Adams, but I can certainly answer this one. Let’s take a look at how our Sun actually works, and then scale it down to be grapefruit-sized.

The Sun is a giant ball of mostly hydrogen gas. It’s extraordinarily massive — about 300,000 times as massive as Earth — and tremendous powerful. The Sun gives off what most people would call an unfathomable amount of energy, but in scientific notation, it’s about 4 x 1026 Watts, which is at least fathomable, although it’s absolutely tremendous. This means that even at the surface of the Earth, 150 million kilometers away, that means we have 129 Watts of solar energy striking us over every square foot that receives sunlight.

But what’s truly exciting, at least for me, is the way the Sun creates its energy. To understand it, we have to go down to the tiniest atomic levels, and look at the hydrogen atoms themselves:

Because the pressure at the center of the Sun is so high, due to the gravitational pressure of having 300,000 Earths pushing in at the core, the nuclei of these hydrogen atoms, protons, get pushed together with a tremendous force. The force is so large that it causes these nuclei to fuse together, in a process called nuclear fusion. With a little math, I can figure out that in order to create the amount of energy the Sun gives off, it has to fuse together about 3.6 x 1038 atoms of hydrogen every second! That little atomic reaction, happening over and over, trillions of times every nanosecond in the Sun’s core, is what produces all the heat, light, and energy we’ve ever received from the Sun.

Now, the person who asked this question wanted to know about having a little stable grapefruit-sized Sun.

Well, here’s a big downer for you: this thing ain’t gonna be stable. If you want to have nuclear fusion going on at the core of this grapefruit-sized ball of hydrogen, you’re going to need a tremendous amount of pressure to push the atoms at the center together. There are only two ways to handle it that we know of, and neither one of them will give you an answer that you’ll like, although they’re both fascinating.

The first way is to artificially increase the pressure, like lasers (shown here) would do. Practically, you wind up getting less energy out than you have to put in to increase the pressure to obtain fusion, which is another disappointment. Scientists working on this call it inertial confinement fusion, and so far, it has never yielded more energy than it took to get it going. So this way looks like a dud. But there’s another way to get nuclear fusion…

You can increase the pressure tremendously — albeit for a very short time — by setting off a small explosion around the hydrogen core, compressing it and causing ignition. There’s a problem with this way, too. The resulting fusion reaction is uncontrolled and runs away, igniting everything. This is commonly known as a hydrogen bomb.

Either way, you give off a tremendous amount of energy, your initial “grapefruit” gets blown apart like a super-powerful exploding grenade, and depending on how much of the hydrogen in there actually managed to fuse would determine what happened. If you scaled down the Sun so that the grapefruit worked on exactly the same scale, you’d only get about 100 million atoms fusing together, or about 100 microJoules of energy. Enough energy to push the hydrogen gas away, but not even enough energy to light a match. But, if you managed to fuse the entire grapefruit into helium, you’d get the energy equivalent of a 160 kiloTonne explosion, or about 11 times the energy of the atomic bomb dropped on Hiroshima, in your fruit bowl.

Without the entire mass of the Sun to insulate this nuclear explosion from the rest of the Solar System, this grapefruit-sized ball isn’t going to last long. Either way, you’re better off getting a heat lamp for your desk, and paying your electric bill.


Unsolved Mysteries? When like charges attract!

March 18, 2009 on 2:29 pm | In Physics | 27 Comments

Attraction and repulsion are two of the simplest concepts in electricity and magnetism: like charges repel and opposite charges attract. (Two steps forward, two steps back.) For electricity, this is how positive and negative charges work:

Two positive charges will repel each other, two negative charges will repel each other, but one positive and one negative charge will attract one another. Simple enough, right? Except, everything is made up of atoms, which have positive and negative charges all throughout them. Certain materials are excellent conductors, which means that positive and negative charges are relatively free to move throughout a material. So if I bring a negatively charged rod close to a neutral conductor, the following happens:

The positive charges line up on the side closest to the rod (because they’re attracted to it) and the negative charges line up on the side farthest from the rod (because they’re repelled). Since the “opposite” charges are closer and the “like” charges are farther, this means that the force from the opposite charges is slightly stronger, and so overall, the negatively charged rod attracts the neutral conductor.

Now, here’s the weird thing: what if you charged up the metal with some negative charges? Would it repel the rod, since negative charges repel? Or would it still attract the rod, since the “opposite” charges are closer than the “like” charges? Well, the answer is both! Check it out!

What I’ve graphed here is Force vs. distance for a negatively charged rod brought close to a negatively charged conducting piece of metal. When the distance is large, they repel each other. But when you bring them close enough, the fact that the opposite charges are closer becomes more important than the fact that there are more like charges, and they attract! There’s even one perfectly balanced point where the force is exactly zero!

And of course, that’s just for electricity. Do magnets do the same thing?

Absolutely! North repels north, south repels south, but north and south attract each other. Magnets make powerful magnetic fields; the stronger the magnet, the stronger the field. What’s really neat, though, is that if you apply a strong enough magnetic field to some materials, like iron, they magnetize, too!

Well, if you bring a weak iron magnet’s North pole close to a strong magnet’s North pole, what do you think will be more important? The fact that the weak magnet is made of iron, and can be magnetized, or the fact that the North pole repels the other North pole? Let’s go down to the molecular level to find out…

Weak magnets have little tiny molecular magnetic moments pointing in many directions. Overall, though, there will be more pointing in one direction than any other, and that’s how your material is “magnetized.” But if you bring a strong magnet close enough, it applies a strong enough magnetic field, and will re-magnetize the weak magnet material to attract the strong magnet! So, is it the same deal as the electric charges? Let’s have a look:

It’s exactly the same! Far away, they repel, close in, it magnetizes and attracts, and yes, there’s a point right in the middle where it balances perfectly, and the force is exactly zero!

So the next time someone tells you that like charges repel each other, you’ll know the exception to the rule!


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