This image represents an expanding Universe. The arrows show that the movement is outward from the center. The spirals represent galaxies.
Hubble Flow: The Expanding Universe
In the 1920's the famous American astronomer Edwin Hubble made a startling discovery that forever changed our view of the Universe. He found that, no matter which direction he looked into space, distant galaxies appeared to be moving away from us. The farther away the galaxy is from our galaxy the faster its recession speed. What could be causing this curious effect? Does our galaxy smell bad? Not at all. In fact, Hubble was observing the expansion of the Universe.
An expanding universe was actually predicted by Albert Einstein's theory of general relativity. But Einstein believed that the Universe should be static because that was more perfect, and many people agreed. But when Hubble made his discovery they were all forced to accept the reality that we live in an expanding universe.
What does it mean that the Universe is expanding? Well, a simple way to think of it is to imagine baking a loaf of raisin bread. As the bread rises it also expands. All of the raisins move farther apart from one another. Every single raisin would see all of the others moving away from it. So to complete the analogy, all of the galaxies in the universe are like the raisins in the bread.
But of course the analogy is not quite complete. Raisin bread has only 3 dimensions: height, width, and depth. However, the Universe has 4 dimensions: height, width, depth, and time. They are bound together in what is known as spacetime. The universe is not only expanding in space but also in time. However, it is really difficult to visualize 4-dimensional raisin bread, so don't try, it'll just hurt your brain.
Shop Windows to the Universe Science Store!
The Fall 2009 issue of The Earth Scientist
, which includes articles on student research into building design for earthquakes and a classroom lab on the composition of the Earth’s ancient atmosphere, is available in our online store
You might also be interested in:
After eight long years, the Hubble Space Telescope Key Project Team finally revealed what they believe is the real Hubble Constant. The Hubble Constant is the speed which the Universe is expanding at....more
The NASA Hubble Space Telescope has recently found some spectacular mirages produced by gravitational lenses in space. These lenses act as giant magnifying glasses for the Universe. A lens is produced...more
According to the Big Bang theory, the universe began about 12-14 billion years ago. Right after the Big Bang, the universe was really hot! But, as the universe has expanded, the particles within the universe...more
Some of the best news of the week is that the Microwave Anisotropy Probe (MAP) was launched successfully last Saturday! Liftoff on its Delta II rocket occurred on time at 15:46:46 EDT, June 30, 2001. So...more
In the 1960's, the United States launched a series of satellites to look for very high energy photons, called Gamma Rays, that are produced whenever a nuclear bomb explodes. These satellites soon detected...more
The introduction of telescopes to the study of astronomy opened up the universe, but it took some time for astronomers to realize how vast the universe could be. Telescopes revealed that our night sky...more
Neutron Stars are the end point of a massive star's life. When a really massive star runs out of nuclear fuel in its core the core begins to collapse under gravity. When the core collapses the entire star...more