Hubble Ultra Deep Field (UDF) photograph

Here we go again, one of the epic documents of our time, the Hubble Ultra Deep Field (UDF) photograph, the deepest look into space ever. A random part of the sky, so small it could be covered by a pinhead held at arm's length. A part of the sky -- as NASA says -- that you'd see looking through an eight-foot-long soda straw. A photo exposed over 400 orbits of the Hubble, a total exposure of 11.3 days. The telescope pointing precisely to the same point in space even as it whizzes around the Earth.

Here's another way to think of it. The image on your computer screen is about 10x10 centimeters. Imagine the image as a tile of that size. A survey of the whole sky -- the whole visible universe from Earth -- would encompass 12.7 million tiles, enough to cover 18 footfall fields!

And each tile shows something like 10,000 galaxies.

A typical galaxy contains as many stars as there are grains of salt in 10,000 one-pound boxes of salt. We are potentially seeing the light of more than 1,000,000,000,000,000 stars. Most, or all, of which have planets.

We've been over this before, but it's worth coming back to. It's not easy to get one's head around. Surely, discovering the scale of the universe is the greatest intellectual achievement in human history, and one of the least appreciated. We live in a universe of at least 10 billion galaxies -- maybe an infinite number -- and we go on worshiping the gods of our cave-dwelling ancestors. Gods with human faces, human qualities, human actions.

Perfectly natural to do so. The familiar is always more consoling than the unfamiliar. As for myself, I stare into those vast and almost unimaginable depths of space and I'm humbled into silence. Stunned. Ecstatic. Curious. Proud of what we have discovered. Knowing that future generations will consider our knowledge fragmentary and naive.

It would take 12.7 million such photos to cover our night sky, and there are 10,000 galaxies in this image.