Le 29 décembre 2015, 07:09 dans Humeurs • 0
detect gravitational waves directly Gravity affects the shape of space and time. Paths of light and massive bodies curve under its influence. When something churns spacetime with enough energy say a supernova explosion or two black holes in orbit around each valentino shoes other the distortion spreads out in ripples, like a rock dropped in a pond. Those ripples are called gravitational waves. These are very weak but, if the accelerating object has enough mass, it should be possible to spot them.
At least, that what we suspect. Gravitational waves were predicted by Einstein's general theory of relativity in 1916, and we been trying to detect them ever since. While we've never measured these waves directly, we have lots of indirect evidence. In 1974, student Russell Hulse and his supervisor Joseph Taylor calculated that a pair of burntout stars spiralling towards one another were radiating gravitational waves at exactly the rate predicted by Einstein. This earned both researchers a Nobel prize around twenty years later.
Any object in orbit around another will emit gravitational radiation, but in most cases this won't be a lot. Gravitational waves ripple out from Earth as it orbits the Sun, but the amount of energy it loses over a period of billions of years is too negligible to be measurable. However, denser objects in the Universe remnants of stars like black holes, white valentino shoes sale dwarfs, or the pulsars that Hulse and Taylor spotted can have much stronger gravity and much smaller orbits, and therefore the energy loss can be very large.
In fact, any sufficiently nonsymmetrical valentino shoes online body can make gravitational waves. A spinning smooth sphere (or even a squashed sphere, as long as it's symmetrical) won't make them, but a lumpy sphere will. If a pulsar has even a tiny mountain distinctly possible if it is in a binary system then the rapid rotation would noticeably produce gravitational radiation. Certain supernova explosions from extremely massive stars are also nonspherical, and would generate gravitational waves. In other words, we expect this radiation to be everywhere. So, why have we not detected it?
Catch a wave A major part of the problem is that gravity is weak: even the strongest gravitational wave will only nudge an atom by a tiny amount. Additionally, the wavelength of gravitational radiation the distance over which a wave repeats itself is often similar to the size of the objects emitting it. So, while radio waves from pulsars may have wavelengths measured in centimetres, the gravitational radiation emitted could have wavelengths measured in kilometres. Which means that you most likely need detectors of a similar size to detect them.