| Topic: | Reply | |
| Posted by: | Michael Ixer | |
| Date/Time: | 29/01/20 17:41:00 |
Jonathan, this isn't meant to sound flippant, but my experience of attending astrophysics and cosmology conferences is that as questions are answered more are generated - and the two you've asked - what caused the big bang and what preceded it - are the big unanswered ones, unless one subscribes to the theory of it just happening spontaneously in nothing! (Which some people do.) Other theories are available ... Einstein's general theory of relativity is used to track the expansion of the Universe back to around 1/104³ seconds where quantum theory then apparently applies to get started from Hawkins's singularity, but I don't profess to understand that ... dark enber is one of the terms in Einstein's equations that makes it works, and no one rally understands what dark energy is (unless de Rham's theory can be proven) although many are working to explain it. The expanding is broadly in line with visual astronomical observations, and in tests done so far the general relativity theory has held up pretty well. The equations are used in the GPS system to make small adjustment to ensure accuracy; the theory predicted gravity waves which have now been detected by LIGO in the US and the EGO in Europe. These just effectively measure the large (let's say dark red) gravity waves. When it launches the ESA LISA satellite system should be able to detect a wide range of frequencies (say blue to red) so one could in theory have a gravity rainbow. Gravitons are hypothetical at present but were introduced to keep gravity consistent with other forces within quantum theory; for example, the electromagnetic force has "light" waves and photons: that seems to work as we have lasers in many things and light detecting devices in our cameras etc. However, gravitons have never be detected but it's only in the past few years gravity waves have been measured. My understanding is that massive gravity isn't different to "normal" gravity but just a modification of gravitational theories to add a small mass to the hypothetical graviton which was originally defined as having no mass, like its cousin the photon which is also mass less. You are right, gravity is determined by mass and as far as I know this modification to the theories doesn't affect that. I'm not sure there is a layman's guide as this is such a fasdt moving area it would be out of date before being published, perhaps try Wikipedia? Anyway, if it's any consolation, Newton and Kepler's laws still work for most rocket science ... Yes, it's nothing liked Brexit, but it makes more sense, and most astrophysicists I've listened to seem to think Brexit is a load of "b*ll*cks" ... |