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QWhich is the smallest muscle in the body? Which is the largest?

The smallest muscles in the body, like the smallest bones in the body, are in the middle ear. Called the stapedius and the tensor tympani, these tiny muscles allow the delicate hearing apparatus to move so that we can hear sounds clearly.

Identifying the largest muscle is more difficult. The most powerful muscle is probably the gluteus maximus - the muscle that makes up the bottom; the longest is the sartorius, which runs from the hip to the knee; and the largest in surface area is the latissimus dorsi, the broad muscle that covers the back.

Q Why do apples go brown?

Tannins in the apple react with the air, which oxidises them and turns them brown. Tannins are found in tea, too. Tannin is actualy a rather loose definition for a chemical that includes a group of compounds called phenolics - containing one or more benzene rings with an -OH (hydroxyl) group on it. All of the phenolics taste bitter, and are found in petals and some fruits.

Q What are wormholes, and do they really exist?

In modern physics and cosmology, wormholes are at present just a theory rather than a proven phenomenon. The theory describes them as short cuts in space, associated with black holes. Imagine you leave your house and go for a walk from Wembley to Aberdeen. At Wembley is a black hole into which you disappear. You then immediately appear out of a wormhole in Aberdeen and continue your journey to the local pub. The distance actually travelled in our space is simply the distance from your house to the black hole plus the distance from the wormhole to the pub. The bit of the journey between Wembley and Aberdeen is never actually travelled. Because you're not actually going very far, it doesn't take very long. To an outside observer though, you have travelled from Wembley to Aberdeen, and very quickly. That observer, calculating the speed of the journey, would suggest that you had travelled faster than the speed of light. In reality your speed was no faster than your normal walking speed; you just shortened your journey. So wormholes don't actually speed you up, they just make your journey shorter.

Q We know that staying out in ultraviolet (UV) light can cause skin cancer; but is infra-red light hazardous too?

UV light has a shorter wavelength than visible light, and infrared light a longer wavelength. In general, the shorter the wavelength, the more energy a photon imparts when it hits a molecule. UV photons (say, from the sun) can carry enough energy so that if they hit a DNA molecule, they can change the chemical structure of a piece of the genetic code so it does not work properly. This can lead to mutation and cancer. Infrared light carries far less energy (less even than visible light) because it has a longer wavelength. This energy warms rather than damages, and is dissipated as heat. Thus infrared light should only damage us by overheating us, and you tend to notice when this is happening. Although UV is far more dangerous, it takes a while for the sunburn it causes to become apparent, so that we can cause ourselves quite a lot of damage without being aware of itn

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