Wave theory In the 1660s, Robert Hooke published a wave theory of light. Christiaan Huygens worked out his own wave theory of light in 1678, and published it in his Treatise on light in 1690. He proposed that light was emitted in all directions as a series of waves in a medium called the Luminiferous ether. As waves are not affected by gravity, it was assumed that they slowed down upon entering a denser medium. Thomas Young's sketch of the two-slit experiment showing the diffraction of light. Young's experiments supported the theory that light consists of waves. The wave theory predicted that light waves could interfere with each other like sound waves (as noted around 1800 by Thomas Young), and that light could be polarised, if it were a transverse wave. Young showed by means of a diffraction experiment that light behaved as waves. He also proposed that different colours were caused by different wavelengths of light, and explained colour vision in terms of three-coloured receptors in the eye. Another supporter of the wave theory was Leonhard Euler. He argued in Nova theoria lucis et colorum (1746) that diffraction could more easily be explained by a wave theory. Later, Augustin-Jean Fresnel independently worked out his own wave theory of light, and presented it to the Académie des Sciences in 1817. Simeon Denis Poisson added to Fresnel's mathematical work to produce a convincing argument in favour of the wave theory, helping to overturn Newton's corpuscular theory. By the year 1821, Fresnel was able to show via mathematical methods that polarisation could be explained only by the wave theory of light and only if light was entirely transverse, with no longitudinal vibration whatsoever. The weakness of the wave theory was that light waves, like sound waves, would need a medium for transmission. A hypothetical substance called the luminiferous aether was proposed, but its existence was cast into strong doubt in the late nineteenth century by the Michelson-Morley experiment. Newton's corpuscular theory implied that light would travel faster in a denser medium, while the wave theory of Huygens and others implied the opposite. At that time, the speed of light could not be measured accurately enough to decide which theory was correct. The first to make a sufficiently accurate measurement was Léon Foucault, in 1850. His result supported the wave theory, and the classical particle theory was finally abandoned.
When the bird's head is in the water, the cool water soaks into the felt head. This causes the liquid inside the bird to contract, making the tail end denser. This causes the bird to tip the head out of the water. The air is warm enough to heat up the thin layer of water, causing the water to evaporate, and the liquid inside to expand. This makes it rise up the inside tube and tip the bird back into the water, and the cycle begins again. So, in short, I suppose the energy in the bird is stored as heat.
No airplane goes faster than the speed of sound wich is 1000km per hour due to safety reasons.
You can rub a magnet along the metal in one direction for a bunch of times (the more the better), and that will magnetize it to some degree, but its not permanent and will demagnetize if it is hit hard with something.
Also, to magnetise something like a nail, if you point one end north, and hit the other end with a hammer it should weakly magnetise it. Unfortunately it doesn't work every time. By creating an electromagnetic field using electricity and then taking a ferromagnetic material and placing it in that field, the material will pick up some of the magnetism. And for more effect, create a bigger field. Plus, if the material to be magnetized is heated really hot (above its Curie point, TC) and then put in the field and then allowed to cool while in the field, it will really pick up the magnetism! This is how commercial permanent magnets are usually made.
1. It depends on the conditions of course, but if dry ice is kept in a closed container it will sublimate (change from solid to gas) at a rate of about 5-10lbs every 24 hours.
2. If you put dry ice in a bottle with water and close the lid it will expode in about 10-20 seconds.