It’s a common belief that astronauts leave Earth’s atmosphere when they venture into space, but that’s not entirely true. Not one astronaut has fully exited the Earth’s atmosphere. Even the International Space Station (ISS), which orbits the planet, operates within this vast envelope of gases we call the atmosphere.
Doug Rowland, a NASA heliophysics expert, sheds light on this misconception. He notes that Earth’s atmosphere doesn’t just stop at the edge we often imagine. It extends much higher than the peaks of our tallest mountains, like Mount Everest, and continues to thin out as you climb. At the height of the ISS, gravity is still very much at play, about 90% of what we experience at sea level, meaning there’s enough atmospheric drag to affect its orbit. If it weren’t boosted regularly with rockets, the ISS would eventually fall back to Earth due to this drag, much like how a car slows down when you press the brakes.
The Kármán line, set at about 100 kilometers (62 miles) above sea level, is typically used to define where space begins for practical reasons, such as legal matters related to space treaties. However, this line doesn’t mark a clear cutoff. According to NASA, about 99.99997 percent of Earth’s atmosphere resides below it.
Recent research provides even more insights into our atmosphere’s reach. A 2019 study based on data from the NASA/European Space Agency Solar and Heliospheric Observatory (SOHO) found that the outermost layers of our atmosphere, including a cloud of hydrogen atoms known as the geocorona, extend far beyond the Moon—up to nearly 391,000 miles (629,300 kilometers) away. This means that when astronauts landed on the Moon, they were still technically within our atmosphere, as there are still enough hydrogen atoms present above 60,000 kilometers (37,280 miles).
Igor Baliukin, the lead author of the study, stated, “The Moon flies through Earth’s atmosphere.” This discovery highlights the intricate relationship between celestial bodies and their surrounding environments. It also points out that both Earth and the Moon are within the Sun’s atmosphere, blending our understanding of space and atmospheric science.
As Rowland explains, the question of when space truly begins is subjective. From one viewpoint, the atmosphere might seem to end around 400 miles above us, but that space beyond is still filled with many fascinating elements, defying the idea that it’s simply empty. Understanding these layers of our atmosphere and beyond gives us a greater appreciation of our planet and its place in the universe.
For anyone interested in learning more about the Earth’s atmosphere and its complexities, take a look at NASA’s insights. It’s a fascinating subject that reveals the intricate dance of gases that envelop our planet and extends far into the cosmos.
Check out this related article: Is the $10 Billion James Webb Space Telescope a Game Changer for Astronomy? Discover the Impact!
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