Where in the Universe Are We?

A very brief travel guide to the universe

By Harman Smith and Laura Generosa (nee Berwin), graphic artists and contractors to NASA's Jet Propulsion Laboratory, with Pluto removed by User:Frokor — Based on Image:Solar_sys.jpg, with Pluto removed. Copied from http://en.wikipedia.org/wiki/Image:Solar_sys8.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=1535590

Size, distance, and space is a captivating idea for us humans. Some of the most common questions from kids relate to size:

How big is it?

What’s the biggest ______?

What’s the smallest _______?

Here’s the thing…. Everything’s relative.

Is a dog big or small? Is a house big or small? Is a skyscraper big or small? Is a country big or small? Is the world big or small?

It all depends on what it’s being compared to. Walking across town can be a monumental feat and yet that distance pales in comparison to flying across the country or to other parts of the world. Even when looking at distances on Earth, we start losing our basic understanding of space and distance pretty quickly.

Understanding a mile. Pretty easy. Understanding 100 miles? A little bit harder, but you know it would probably take you about an hour and a half to two hours on the highway depending on the speed limit and other factors. Going from one side of America to the other? Probably a week-long road trip or a six-hour-minimum plane ride depending on the direction of travel, number of stops, etc.

Pretty soon, the distance becomes very vague. Close. Far. Very far. Closer than x place but farther away than this place. We need things to compare to understand how far away something is.

And with space, most things are going to be bigger than we will ever encounter. It takes about three days to get to our nearest neighbor in space: our moon. To go to Mars, the next planet away from us heading away from the Sun? 6–8 months. That’s the commute time to essentially go to our neighbor’s house in space terms.

It took the New Horizon probe nine and a half years from its launch in January 2006 to reach the dwarf planet Pluto about three billion miles away. Miles start becoming meaningless when we are talking about millions and billions of them.

That’s why even when talking about the solar system, we typically use Astronomical Units (AU). 1 AU is the average distance from the Sun to the Earth, 93 million miles. Our furthest planet from the Sun, Neptune, is about 30 AU from the Sun…