How High is “High” for Humans?

We look up at the blue sky and think it is endless, with air reaching all the way to the stars. But that’s not true—our atmosphere is not limitless.

For most people, being at sea level means our bodies get the perfect amount of oxygen. But as we go higher, like John did on Mount Everest, oxygen levels start dropping rapidly. By the time climbers hit Everest’s summit, they’re breathing just a third of the oxygen found at sea level, which is why they need oxygen tanks to survive.

Airplanes fly even higher—around 10 kilometres up, in the lower stratosphere. At this height, there’s almost no breathable oxygen, and temperatures are freezing. 

John’s experience shows how challenging it is to adapt when oxygen becomes scarce. Even the strongest climbers can only handle a few hours at Everest’s peak, and only with extra oxygen. It’s a reminder of how unique Earth’s atmosphere is—thin enough to allow us to reach the edge of space but dense enough to keep us breathing comfortably most of the time.

-

Let me tell you the incredible story of Felix Baumgartner and his amazing jump in 2012—like something out of a sci-fi movie! Felix jumped from the edge of space. He rode a special balloon all the way up to 39 kilometers (about 24 miles) above the Earth. Imagine looking down and seeing the entire planet below you—that’s what he saw!

When he jumped, he didn’t just fall. Felix hurtled back to Earth, breaking the sound barrier as he went! That means he was falling faster than the speed of sound—about 1,357 kilometers per hour (844 mph). It took him a little over 9 minutes to land, but most of that time, about 4 minutes, was just free-falling before he opened his parachute.

The whole jump was dangerous and exciting, but Felix pulled it off with skill, bravery, and a lot of preparation. People around the world watched as he became the first person to break the sound barrier without an aircraft. How cool is that?

Watch his fall in this video.

• Why didn’t Felix open his parachute earlier? Answer
• How high was Felix when he jumped? Answer
• How long did it take for him to reach the ground? Answer
• Why did Felix wear a special suit? Answer