Slashdot Mirror
Alien Solar System Much Like Ours
MrGort writes "Wired News reports that British astronomers say they found the first sun-like star with a giant gas planet in an orbit similar to Jupiter's, which leaves plenty of room for worlds like Earth and Mars. This system is a quick 90 light years away. The similar solar system to ours means that this gas giant could attract most of the debris, allowing smaller planets closer to the sun to develop like ours did!"
(a) Most physicists think gravity is transmitted at light speed. Very few (and none who believe in General Relativity) think gravity is instantaneous.
(b) (I Am A materials scientist) "Solid" matter is composed of atoms bound together by electromagnetism. When you "push" a solid object, displacement waves (essentially sound waves), travelling from atom to atom inform the material that you are pushing it. For sufficiently fast pushes and short timescales, even a block of carbon steel looks like a wobbly jelly. This is important in impact engineering, for example, and mechanical engineers and materials scientists deal with stress waves in solids all the time (plastic torsion waves are the most "fun"). Nothing is perfectly solid.
Your "stick to europa" would have to have unphysical infinite rigidity for instantaneous transmission. In real life, assuming you could make a stick to europa (not in itself unphysical, just extremely unlikely), a wave train would travel down the stick when you displaced one end, displacing the material of the stick. This would happen at the speed of sound in the stick, which is always significantly lower than light speed (since it is determined by interatomic interactions, themselves subject to light speed) So yes, conceivably, the drum would make a sound, but the sound would come some time after you pushed the other end of the stick, since the stick would be acting like a wobbly jelly on such a scale, as all atomic matter must.
You can even see this in action - surely you've seen the high-speed movies of bullets hitting apples, with deformation waves crisscrossing the surface? All solids behave that way, it's just the waves travel very quickly (but not nearly as fast as light...) in some solids such as hardened metals.