No one person is considered to have discovered Mars. As it is very bright in the night sky, it has been visible since the first humans gazed up to the heavens. What we do know is that it was named after the Roman god of war- presumably because of its red color which may have [...]
I saw a couple of good posts on this from astronomycafe.net on their ask the astronomer page. The general consensus of all the answers out there seems to be that we do not know exactly, but there are at least a hundred billion, and possibly several hundred billion. The following is quoted from Astronomy Cafe: [...]
Actually, the intensity of the stars themselves doesn’t fluctuate, rather it is the light they emit that appears to brighten and dim as it passes through the air in our earthly environment. Were you to look at the stars from an airless environment, say the moon, you would see them as solid luminous points of [...]
Mathematical theory suggests that most comets may come to the solar system from very far away, as far away as 100,000 Astronomical Units. In this picture, the solar system is buried deep within the cloud. An Astronomical Unit (or AU) is the distance from the earth to the sun and is equivalent to about 93,000,000 [...]
First, the simplest definition of density: it is how heavy something is relative to its size. A pound of rocks weighs the same as a pound of ping pong balls. But the ping pong balls take up a lot more space. Hence, the rocks are much more dense. Another way to look at density is [...]
Hubble’s Constant is the rate ratio of the speed at which a galaxy is moving away from Earth divided by its distance from Earth. Note, this is obviously not our galaxy, but other galaxies in the Universe.
Most scientists estimate the time between the Big Bang and current day somewhere between 13 and 20 billion years ago. Estimates are derived from Hubble’s Constant, a rate of expansion ratio calculated by dividing the speed at which a galaxy is moving away from the Earth by it’s distance from the Earth.