An Astrophysicist Reveals What Space Is Actually Made of : ScienceAlert | Space

What comes to mind when you think of space? Imagine a friend boasting about a spacious building, stadium or museum they recently visited. Do you envision the building as vast and expansive? Is it simply very large, or does it seem empty?

The word spacious does not necessarily mean empty. It simply indicates that there is enough room to move around the objects inside it. Similarly, outer space is not completely empty. It is vast and forever expanding, but there’s a lot of stuff in it.

As a kid, I used to wonder about questions like how far away the clouds are, what lies beyond Earth and how vast space is. This curiosity led me to pursue master’s and Ph.D. degrees in astronomy. I have been teaching about these very concepts for two decades as a physics instructional professor at the University of Texas, Arlington.

Where does space begin?

Earth is surrounded by different layers of various gases. At sea level, Earth’s atmosphere contains about 100 billion molecules per cubic centimeter. As we ascend, the atmosphere becomes thinner and thinner.

At an altitude of about 50 to 62 miles (80 to 100 km), there isn’t enough air for airplanes to fly. This boundary, which separates the Earth’s atmosphere from outer space, is called the Kármán line, named after the Hungarian-American engineer…