mikeShriver

…A man who can still find awe in the bigness of things.

On Mission India and the Size of the Universe

During our conversations, you expressed a rare wonder at the expanse of the universe. My whole life I have been confronted by astronomical charts, and the enormity of the universe has become familiar idea. After I got back from my trip to India, I looked up some information about out place in the universe, and I think you might be interested in some facts I have taken for granted. This stuff always amazes me when I stop to think about it.

A few years back, an astronomer with some spare time on his hands took the most powerful telescope that we have available to us, The Hubble Space Telescope, and pointed it at a completely black patch of the night sky. He was curious about what he would be able to see if he left it focused on the blackness of space, and the image he came up with is called the Hubble Ultra Deep Field:

It is an incredibly striking image by itself, but just seeing it doesn’t really reveal all of its implications. To fully understand it, you need some background information. The relative sizes of the objects in our galaxy can provide a good starting point.

First, our own home. The earth is about 40,000km around at the equator. I know you fly halfway around the world with regularity, and so you have an easy reference point for the size of the blue marble (the flight from Chicago to Mumbai is 12,978 km, and about 16 hours).

In comparison, the Moon is 10,921km in circumference, and about 3,475km through the middle. That is about the distance from the top of India to it’s southmost point in Tamil Nadu. The moon orbits at a distance of about 405,700km. If you were travelling the same speed as that Mumbai-bound jumbo jet, it would take you about three weeks to arrive at the Moon.

The Sun is about 100 times the diameter of the earth and is 152 million km away, which would take you 21 years to reach in your airplane.

Here is where things get really big. We are out of the range of kilometers, and have to switch to a larger unit, the lightyear. One lightyear is defined as the distance that light travels in a single year, and it is approximately 9,461,000,000,000 (nine and a half trillion) km. Which is a way bigger number than I can even comprehend. In comparison, it takes the light from the Sun only 8 minutes to travel the distance from the Sun to the Earth. It takes that same light about 6 hours to get to Pluto, at the edge of our little solar system.

Our sun is one of about 100 billion stars that make up the Galaxy we reside in, known as the Milky Way. The Milky Way is shaped like a flat disk of two outwardly spiraling arms. The disk is about 100,000 lightyears across, and about 1,000 lightyears thick. The closest star in the Milky Way to our sun is 4 lightyears away, a distance that is practically impossible for humans to cross. We will likely never even travel outside our own little solar system, past Pluto.

I have to admit that I have a hard time visualizing the distances that I’ve described so far, because they are so vastly outside my range of experience.

Now, go back and look at the first image. The original of this image is pretty large, but it covers a small portion of the sky. If you walked outside under a full moon and looked up, this image would cover a patch of sky about 1/10th of the size of the moon. The image is so small, it would take 13 million of them to cover the entire sky. There are no single stars in the image. Every single speck in the image is a galaxy like our own Milky Way. That means that thousands of galaxies fit into that tiny little speck in the night sky.

The first time I saw that image was a moment of epiphany for me. I can’t fathom the sheer insignificance that even our own unfathomably huge galaxy commands in the universe, not to mention our own tiny planet.

I hope that this information is interesting to you. It certainly has made me wonder at the enormity of everything. My understanding of it all is pretty limited, but feel free to ask me any questions you have, and I will answer them to the best of my knowledge.

–Mike

Note:  A full version of the Hubble UDF image can be found here:

http://hubblesite.org/newscenter/archive/releases/2004/07/image/a/

Tags: astronomy, epiphany, rimi, saji, universe.