We generally think of numbers as a linear progression from 1 to 2 to 3, etc. We also tend to measure things around us on a linear scale. A ten hour road trip, for example, is very different from a one hour trip. In the sciences, however, it is often more useful to look at things on a logarithmic scale.
Bend and Stretch
Since space itself is expanding, the wavelength of the traveling light also stretches. This means that while the light travels, it continues to redshift due to cosmic expansion.
More Things in Heaven and Earth
Take a moment to let the profound nature of this image sink in. This image is what we got when we pointed the Hubble telescope at what looked like empty space. Each smudge of light in this image is a young galaxy, from about 500 million years after the big bang. Thousands of galaxies in a patch of sky the size of a grain of sand.
The Universe in a Grain of Sand
Suppose you picked up a grain of sand and held it at arm’s length. If you held it up in the night sky, it would block a tiny fraction of the visible heavens. Now suppose instead of of a sand grain it were a tiny window, through which you could see even the faintest light. Finally, suppose you were to take your tiny window and point it at the darkest patch of night you could find. What would you see?
Hubble’s Constant
Hubble’s constant shows a relationship between the distance of a galaxy and the speed at which it moves away from us. Its discovery was the first evidence that the universe is expanding.