Thursday, September 23, 2010

The Kids Are Far Out - part three

The final set of questions from the kids of Cosmic Carnival may be last, but they’re certainly not least. In fact, I think these three budding scientists asked questions which we should all consider. To do so is to begin to have some understanding of our place in the universe.

Ryan from Albuquerque, age 9, pondered this:

“I was wondering how thick the atmosphere is on Earth.”

A real brain teaser of a question, Ryan! There is no straightforward answer to this question because our atmosphere does not have clearly defined borders. As we go up in altitude, Earth’s atmosphere very gradually becomes thinner and thinner until it merges with outer space. So we could say the answer is 800 miles thick if we include the outermost layer, the exosphere, where the air is extremely thin.

Or we could use the altitude where space is officially considered to begin: 62 miles (100 kilometers) above sea level. So, the answer could also be 62 miles thick, since around 99% of the mass of our atmosphere is found below this point. You can read more about Earth’s atmosphere here.

The layers of Earth's atmosphere, bottom to top:
Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere

Image source: NOAA/National Weather Service

Scott from Rio Rancho, age 8, posed this question:

“How does the Earth spin around the Sun?”

Scott, we generally say that Earth spins (or rotates) on its axis, the way a top spins. We also say it orbits (or revolves) around the Sun. 24 hours a day, 7 days a week, our home planet is spinning like a top and traveling in an orbit around the Sun, at the same time.

Whenever you look east (the direction of the rising Sun), you are looking in the direction toward which the Earth is spinning, as well as the direction in which Earth is traveling as it circles the Sun.

Sophie from Albuquerque, age 9, was looking way beyond the solar system when she asked:

“If we’re in the Milky Way, how do we have pictures of the Milky Way?”

It’s a puzzle, isn’t it, Sophie? It’s true: we do reside in the Milky Way galaxy. In fact, every star you see in the night sky is in the Milky Way galaxy.

If you go stargazing out in the country, away from city lights, you will probably see what looks like a long, glowing cloud arching overhead from horizon to horizon. It’s actually a collection of billions of stars too numerous and faint to be resolved (separated into distinct points of light) with the naked eye, so we see it as a hazy band of light. We call this object the “Milky Way” too, even though it’s just part of our home galaxy. This is probably what you have seen in photographs, as it’s a popular target for astrophotographers.

The glowing “cloud” is an edge-wise view of the star-packed spiral arms of our platter-shaped galaxy. Even though we are in one of those arms (the Orion Arm), we can look across space at neighboring arms. The diagram below will give you a better picture of your place in space.

Diagram of the spiral arms of the Milky Way

Image source: Richard Powell

In conclusion, I have to admit that I seriously doubt I could have formulated any of these questions at the tender age of 8 or 9. I was a science ignoramus for my entire childhood and, indeed, much of my adult life. So, I am awed and inspired by the far-out kids I met at Cosmic Carnival, who are already looking up and wondering about the universe in which they live. I hope they never lose that sense of wonder.

Have you looked?