The stars that you see in the night sky are part of the Milky Way, our home galaxy. But the Milky Way is not all around us because we do not live in the middle of the Milky Way; our solar system resides midway between the edge and the center of the Milky Way galaxy. If we could travel at the speed of light (186,000 miles per second), it would take us about 25,000 years to reach either the rim or the center of the Milky Way.
Our solar system makes up only a tiny part of the Milky Way. To compare, if the entire Milky Way would be the size of the United States, our solar system would only be the size of an American penny.
It’s not that Earth is that small. Earth weighs 6 sextillion, 600 quintillion tons. Yet, 764 planets the size of Earth will fit into Saturn, the second largest planet in our Solar System and our farthest planet visible by the naked eye.
At the same time, Saturn – named after the Roman god of agriculture – is small compared to our sun. You can fit 1,700 planets the size of Saturn into the sun. It takes Saturn 29½ years to orbit the sun. Even so, compared to other suns our sun is small (the biggest known sun, VY Canus Majoris, is 2,000 times the size of our sun) and only one of an estimated 200 billion stars (and more planets) in the Milky Way.
It takes our sun 250 million years to complete one rotation of the Milky Way.
But consider that the Milky Way is only one of 200 billion+ galaxies, each with billions of stars, in the known universe. Our Milky Way is not even the biggest galaxy, being only 100,000 light years across (and 1,000 light years in thickness). The Milky Way is a spec in the universe: the size of the universe is estimated to be 13,7 billion light years in size.
A tiny ship
Earth is a tiny ship in a vast ocean. The famous astronomer Carl Sagan constantly tried to remind us of our fragile place in the universe. In 1990, he requested that the space craft Voyager 1 take a picture of us at a distance of 3.7 billion miles (6 billion km) away from Earth. The picture tells the story: Earth is a Pale Blue Dot in the galaxy.
Our humble home
70% of the earth’s surface is covered in water. We live on a small part of earth. We live on a spec of a spec in the universe. Honestly, it shouldn’t be that difficult to reach out to each other.