3 ms·

As someone who doesn't have a very good grasp of these things, can you explain the difference between the Big Bang and inflation to me? It seems like the Big Ba

As someone who doesn't have a very good grasp of these things, can you explain the difference between the Big Bang and inflation to me? It seems like the Big Bang is the explosion of all matter that would be in our universe, and inflation is the rapid expansion of the universe itself. And inflation is believed to have taken place almost immediately after the Big Bang. Is that sort of accurate?

wbhart 13y ago
The Big Bang theory is not about the "explosion" of our universe from a point. Firstly, the universe may have always been infinite in size. It's just that every small piece of that infinite universe has been expanding since about 14 billion years ago. Secondly, "explosion" is a misnomer. The universe is expanding, not exploding. As a theory, the Big Bang theory makes various predictions, such as the cosmic microwave background radiation, the relative abundance of elements in the universe and of course the expansion of the universe. But it doesn't predict that the universe will be the same in all directions. There just isn't time for energy fluctuations to have evened themselves out due to the transfer of energy from hot spots to cold spots. That process can only happen at the speed of light (energy is transferred at the speed of light). Because of the way space is expanding, the speed two points move away from each other depends on how far apart they are. Thus, very distant points on opposite sides of the sky are actually moving apart faster than the speed of light. What this implies is that there's no way they can have had time to reach thermal equilibrium (i.e. have reached the same temperature)! But satellite observations tell us the observable universe is very nearly the same temperature in every direction! The problem is resolved by the Theory of Inflation. This is a time of exceedingly(!!) rapid expansion which occurred before the time described by the Big Bang theory (remember the Big Bang theory is not about the "explosion" of the universe from a point, but about the subsequent expansion of the universe after inflation). The reason inflation solves the problem is that a very, very tiny region of space (subatomic scale) expanded exceedingly rapidly in a tiny fraction of a second, smoothing out any temperature fluctuations. What we see as our observable universe is just the temperature fluctuations in a subatomic sized piece of universe from before inflation happened. After that tiny fraction of a second, inflation stopped, and normal Big Bang physics took over. Moreover, inflation explains the formation of galaxies. Tiny quantum fluctuations became the seeds of galaxies, clusters, superclusters and giant strings of clusters that make up our universe today. Note that almost everything written in the current Slashdot summary of the breakthrough is completely wrong!

wbhart 13y ago

The Big Bang theory is not about the "explosion" of our universe from a point. Firstly, the universe may have always been infinite in size. It's just that every small piece of that infinite universe has been expanding since about 14 billion years ago. Secondly, "explosion" is a misnomer. The universe is expanding, not exploding. As a theory, the Big Bang theory makes various predictions, such as the cosmic microwave background radiation, the relative abundance of elements in the universe and of course the expansion of the universe. But it doesn't predict that the universe will be the same in all directions. There just isn't time for energy fluctuations to have evened themselves out due to the transfer of energy from hot spots to cold spots. That process can only happen at the speed of light (energy is transferred at the speed of light). Because of the way space is expanding, the speed two points move away from each other depends on how far apart they are. Thus, very distant points on opposite sides of the sky are actually moving apart faster than the speed of light. What this implies is that there's no way they can have had time to reach thermal equilibrium (i.e. have reached the same temperature)! But satellite observations tell us the observable universe is very nearly the same temperature in every direction! The problem is resolved by the Theory of Inflation. This is a time of exceedingly(!!) rapid expansion which occurred before the time described by the Big Bang theory (remember the Big Bang theory is not about the "explosion" of the universe from a point, but about the subsequent expansion of the universe after inflation). The reason inflation solves the problem is that a very, very tiny region of space (subatomic scale) expanded exceedingly rapidly in a tiny fraction of a second, smoothing out any temperature fluctuations. What we see as our observable universe is just the temperature fluctuations in a subatomic sized piece of universe from before inflation happened. After that tiny fraction of a second, inflation stopped, and normal Big Bang physics took over. Moreover, inflation explains the formation of galaxies. Tiny quantum fluctuations became the seeds of galaxies, clusters, superclusters and giant strings of clusters that make up our universe today. Note that almost everything written in the current Slashdot summary of the breakthrough is completely wrong!