Yuri Gagarin, Neil Armstrong, and Katy Perry Have Something in Common: None of Them Left the Earth’s Atmosphere

Every so often, NASA reminds us through anecdotes or studies that things aren’t always what they seem, or that they can often be questioned and may have more than one answer. The agency recently presented a simple yet startling explanation for why we can’t find aliens. It also clarified why humans haven’t returned to the Moon.

More recently, NASA explained why, technically speaking, no human has ever fully left the Earth’s atmosphere.

Controversial but true. Claiming that no astronauts have completely exited our atmosphere may sound like a joke or a conspiracy theory. However, from a scientific viewpoint and based on current atmospheric models, it’s quite accurate.

This means iconic figures such as cosmonaut Yuri Gagarin and astronaut Neil Armstrong have remained within the most extreme (though diffuse) limits of the Earth’s atmosphere. The key lies in defining the boundary of that atmosphere, which is more complex and nuanced than people usually think.

Far beyond. Doug Rowland, a heliophysics expert at NASA, recently elaborated on this concept. Scientists previously believed that the atmosphere ended at a defined layer before reaching Earth’s orbit. The reality is that there’s not a clearly defined “line.” Instead, the atmosphere becomes progressively thinner as it expands.

Rowland explains that even at hundreds of miles above the Earth’s surface, where the International Space Station orbits, there’s still enough air density to gradually slow the station down. In fact, if the ISS weren’t periodically boosted with rockets, it would eventually descend due to atmospheric drag.

The Kármán line. To establish a practical boundary for legal and treaty purposes, the scientific community has widely adopted the Kármán line, located 62 miles above sea level, as an international convention. This line marks the point where space theoretically begins.

This boundary serves as a technical threshold, given that more than 99.99% of the Earth’s atmospheric mass lies below it. However, the Kármán line is primarily useful for regulations and classifications rather than for describing the actual physical limits of the atmosphere with precision.

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The geocorona. In 2019, a study revealed that the Earth’s exosphere (a diffuse cloud of hydrogen atoms known as the geocorona) extends up to 390,000 miles. This is beyond the Moon’s orbit. The study was based on data from the Solar and Heliospheric Observatory, a European Space Agency spacecraft.

However, there are still about 0.2 hydrogen atoms per cubic centimeter at that boundary. This means that, technically, even the Apollo missions that landed on the Moon in the 1960s and 1970s never completely left Earth’s atmosphere. Study author Igor Baliukin even suggested that “the Moon flies through the Earth’s atmosphere,” highlighting the unexpected extent of this invisible layer.

The Sun’s role. Things become more complex when considering that both the Earth and the Moon are also within the solar atmosphere. This solar atmosphere extends to the edge of the heliosphere, which is the boundary beyond which interstellar space begins. Between the Earth’s atmosphere and that of the Sun, there’s no vacuum. Instead, there exists a structure of progressively superimposed layers that contain particles, energy, and electromagnetic dynamics.

So, where does space begin? According to Rowland, the answer depends on your perspective. Practically speaking, you might define the end of the atmosphere at about 250 miles above the Earth, where air density becomes too low to significantly affect objects.

However, from a scientific standpoint, the atmosphere doesn’t simply disappear. It continues to dissipate and dilute to levels that are barely measurable, without vanishing altogether. As such, “outer space” isn’t an empty void but a continuous environment filled with particles, fields, and subtle structures.

In this sense, all human space travel, including Katy Perry’s recent flight, has occurred within an extended area that’s still part of Earth.

Image | Niketh Vellanki

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