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When scientists talk about the expansion of the universe, they mean that it has been growing since its beginning with the big bang.
Galaxies outside our own are moving away from us, and the ones further away are moving faster. this means that no matter what galaxy you are in, all other galaxies are moving away from you.
however, galaxies don’t move through space, they move in space, because space also moves. in other words, the universe has no center; everything moves away from everything else. if you imagine a grid of space with one galaxy every million light-years or so, after enough time passes, this grid will spread out so that galaxies spread out every two million light-years, and so on, possibly up to infinity.
The universe encompasses everything that exists, from the smallest atom to the largest galaxy; since it was formed about 13.7 billion years ago in the big bang, it has been expanding and can be infinite in scope. the part of the universe that we know about is called the observable universe, the region around the earth from which light has had time to reach us.
A famous analogy to explain the expansion of the universe is to imagine the universe as a loaf of raisin dough. as the bread rises and expands, the raisins move further away from each other, but are still trapped in the dough. In the case of the universe, there may be raisins out there that we can no longer see because they have moved away so fast that their light has never reached earth. Fortunately, gravity has control of things locally and holds our raisins together.
who discovered this?
American astronomer Edwin Hubble made the observations in 1925, showing that there is a direct relationship between the velocities of distant galaxies and their distances from Earth. The observation that galaxies are moving away from Earth at speeds proportional to their distance has traditionally been known as Hubble’s Law, although it should be noted that, in 2018, the International Astronomical Union (IAU) voted to recommend changing the name to Hubble. -lemaître law, in recognition of the contributions of both hubble and belgian astronomer georges lemaître to the development of modern cosmology. The Hubble Space Telescope was named after Edwin Hubble, and the single number that describes the rate of cosmic expansion, relating the apparent recession velocities of external galaxies to their distance, is called the Hubble constant.
so the universe is infinite?
It might be easier to explain about the beginning of the universe and the big bang theory than to talk about how it will end. the universe may last forever, or it may be crushed out of existence in a reverse big bang scenario, but that would be so far in the future that it might as well be infinity. Until recently, cosmologists (scientists who study the universe) assumed that the rate of expansion of the universe was slowing down due to the effects of gravity. however, current research indicates that the universe can expand into eternity. But research continues and new studies of supernovae in remote galaxies and a force called dark energy may change the possible fates of the universe.
published: 11/19/2019. author: scientific reference section, library of congress
