Thread: How Many Galaxies Have We Discovered?

Astronomers think that there are hundreds of billions galaxies in the universe, however the exact number is not known. But astronomers should know how many galaxies we've actually seen and discovered, right? Well, not necessarily. “We don’t know,” says Ed Churchwell, professor of astronomy at the University of Wisconsin-Madison. “We know it’s a [...]More... (http://www.universetoday.com/2009/08...we-discovered/)

The 'average' galaxy is a colossal island of 100 billion stars, although certainly much larger and smaller galaxies exist. Estimates today run from a minimum of 50 billion up to 100 BILLION (or more) galaxies, based on numbers in photographs and multiplying and averaging.



A great analogy appears on the "Astronomy" calendar most years, that sums up the number of known galaxies quite nicely....


Called " The Universe Train "

The universe is so vast that it's difficult to establish a scale of reference, but this freight train analogy might help put it into perspective. Imagine each star in the KNOWN universe is represented by a grain of sand. A thimble would hold all the stars visible on a clear, dark summer night. A dump truck would contain the Milky Way, the galaxy in which the Sun resides. To demonstrate all the stars in the universe, we need a freight train with hopper cars filled with sand. (Keep in mind that 3-5 dump trucks would be needed to fill ONE hopper car) The train begins to pass us at a level crossing. We count the cars as they roar by at a rate of one per second (about 40 MPH computing a 55ft car which holds 120 TONS of sand).
The minutes pass...
then hours...
then days....
We would have to keep count 24 hours a day for three years before the universe train would complete its pass. The universe train would use all the sand on all the beaches on Earth and would be long enough to stretch around the planet 25 times!


Imagine being stuck at THAT crossing on your way to work!