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The Michelson–Morley experiment was a scientific experiment to find the presence and properties of a substance called a ether, The experiment was done by Albert A. Michelson and Edward Morley in Since waves in water need something to move in (water) and sound waves do as well (air ), it was believed that light also needed something to move in. Scientists in the 18th century named this substance a ether, after the Greek god of light . They believed that a ether was all around us and that it also filled the vacuum of space . Michelson and Morley created this experiment to try and prove the theory that a ether existed. They did this with a device called an interferometer.

So how do astronauts float in space if the pull of gravity is so strong? Astronauts don t actually float. They are being pulled by the Earth s gravity just the same as the rest of us. But they are also orbiting the Earth, or moving sideways. This is known as centrifugal force. This sideways movement actually is pulling them away from the Earth at the same time that the Earth is pulling them down, so it appears as if they are floating. place. When an object floats on the top of water, gravity is still in play. For an object to float, it must displace enough water to make up the same mass as the object itself. Once that happens, the remaining mass then sits on top of the water. For example: if a boat has a mass of 45 grams, it will displace 45 grams of water and if that has happened before the whole thing has sunk below the surface level of the water, the boat floats. Helium balloons are pulled by gravity, as are all objects with mass. The reason they don t fall is that there is another force acting on them, a buoyant force from air pressure that is equal to the weight of the air displaced by the balloon. Does gravity act on helium balloons?