Baby born with three arms

Though perhaps calling it one and two halves would be more accurate, as neither of the two left arms is fully functional. I find it nauseating that the Chinese doctors are contemplating arbitrarily chopping off one of the "extra" arms just so the child will fit in, despite the fact that they have no idea which arm is "better."

Science goes boom!

Good science should be exciting. Check it.

Issues-based shopping

I feel like I've posted about IdealsWork before, but it was a while ago and I just stumbled across them again. If issues such as human rights, women's issues, and the environment matter to you, IdealsWork helps you pick which company has the best track record on those issues. HINT: You probably want to check OFF Nuclear Energy, since as far as I can tell they're saying that companies that use nuclear energy get a LOWER rating, while nuclear energy is significantly better for the environment than coal or oil or natural gas. You can also pick the "advanced" tab to weight different issues more heavily. Vote with your money!

Speaking of sound...

There's an article briefly highlighting age-related hearing loss. In short, as people get older, they start to lose the upper range of frequencies that they can hear, and this starts as young as in your twenties. If you want to test your hearing, there's a high frequency sound here.

I wonder though, whether all computer speakers are capable of producing that sound in the first place. I'm sure there's a way to look up the high-frequency cutoff for any given speaker, but I'm too lazy to check on mine. :-P As for why older people can't hear it, there's a little info here and and here, but it appears that the cause isn't all that clear, or else isn't clearly known.

Thanks to the_xtina for the head's-up.

The Physics of Sound

Inspired by a post by galbinus_caeli about singing off-key.

Sound is a type of wave perceived by the human ear. Sound waves travel through air (or water and other materials) by compressing (squishing together) the air molecules. The air actually jiggles, alternating moving slightly towards and away from you. (If it moved in a big clump towards or away, that would be wind or a breeze.) When the air next to our ear drum gets moved one way and another, the material of our ear drum gets pushed in and out correspondingly. Nerves and the brain then interpret this and we hear things around us.

[As an aside, hearing loss can be caused by damage to the ear drum (as in old age or a "blown" ear drum), or by nerve damage, or by damage within the brain itself. Damage to the ear drum can be fixed I believe, or sounds amplified by a hearing aid. Hearing aids can also be useful for some forms of nerve damage, but not all.]

How "fast" the air "jiggles" is described by scientists as the frequency of the sound wave - technically it's the number of jiggles or cycles per second. Our brain interprets this as pitch. A high pitch is a big number for frequency, while a low pitch is a small number for frequency. Of course, there is more to sound than this.

When a sound is generated by a simple machine (a frequency generator), it will have only a single frequency, meaning the air only jiggles at one rate, and it will sound "simple" or "pure" to our ear-brain combination. This single frequency is sometimes called the fundamental. However, sound (music) is usually created by some (musical) instrument, and this is not simple: we do not get out only one frequency. Similarly to how the ocean has tides, and on top of the tides are waves, and on top of the waves are ripples, sound will have layers of waves. In the water comparison, tides are the lowest frequency, and ripples the highest. In sound, the fundamental has lowest frequency/pitch, and higher frequencies are added on top of it, called harmonics.

When you pluck a guitar string with no fingers on it, the full length of the string vibrates in one lump (called a node). This vibrates the air around it and the human brain most easily perceives this lowest frequency or the fundamental, and we perceive it as the "note" or "pitch." In addition, the string vibrates at the same time in two lumps/nodes, giving the first harmonic. It also vibrates with three nodes, four nodes, and so on. Some of these harmonics vibrate more strongly than others, and which ones depends upon the specific instrument. Most humans don't consciously observe the harmonics, we just put them all together. How strong (loud) the various harmonics are compared to each other and the fundamental is perceived by the brain as the quality or timbre (pronounced "TAM-burr") of the instrument, and what distinguishes one instrument from another (and one person's voice from another).

To change what note is being played on the guitar string, you would then put your finger down somewhere, changing the length of the string, and therefore how fast it vibrates, which means the frequency of sound. For guitars and other stringed instruments, the pitch of each note is also affected by the tension in the string (how tightly the string is wound, changed with tuning pegs) and the density of the string (how thick the string is and what it's made out of, which is why there are multiple strings).

In reed instruments (clarinet, sax), you first vibrate a bamboo or plastic strip, which then vibrates air inside the instrument, and the fundamental is determined by the distance between the reed and the first open hole, and the thickness of the tube of the instrument (that is, the tube the air is traveling through). In wind instruments (flute, piccolo) you're more directly vibrating the air. In most brass (trumpet, tuba) you vibrate a little diaphragm or plate in the mouthpiece and then it follows as above. Percussion instruments you vibrate the material that you're hitting - the face of the drum, wood on the xylophone, cow bell, whatever.

As for what makes a chord, or music, that is cultural, and there's no way I get that, let alone being able to explain it! :-P

How to cheat on papers

From a college prof, this list of common, easily caught, cheating mistakes is amusing. I tend to give less papers and more problems, so I don't see all of these, but they're definitely similar to things I have seen. *Sigh* As a commenter says, if you're good enough to cheat right, you probably don't need to cheat. It's probably more effort to actually do those things, than to do the work in the first place!

ETA: Whee, I just got to delete a spam comment for an essay writing webpage! (Same as someone legitimately commented about below, but this one was clearly spam.)

The Firefox Nebula

A group of researchers using the HST have recently discovered the Firefox nebula.

I don't really get why a blog hosted at a Uni has Google ads though...