![]() ![]() Sometimes, the Aurora Borealis and Aurora Australis occur in the lower part of the exosphere, where they overlap into the thermosphere. Hence why the majority of Earth’s satellites orbit within this region. It is here that Earth’s atmosphere truly merges with the emptiness of outer space, where there is no atmosphere. The atoms and molecules are so far apart that the exosphere no longer behaves like a gas and the particles constantly escape into space. This layer is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules (nitrogen, oxygen, CO²). The outermost layer, known as the exosphere, extends out to an altitude of 10,000 km (6214 mi) above the planet. The International Space Station also orbits in this layer, between 320 and 380 km (200 and 240 mi), and needs to be constantly boosted because friction with the atmosphere still occurs. Hence, this is where the phenomena known as Aurora Borealis and Aurara Australis are known to take place. The lower part of the thermosphere, – from 80 to 550 kilometers (50 to 342 mi) – contains the ionosphere, which is so named because it is here in the atmosphere that particles are ionized by solar radiation. Credit: NASAThe Thermosphere, the second highest layer of the atmosphere, extends from an altitude of about 80 km (50 mi) up to the thermopause, which is at an altitude of 500–1000 km (310–620 mi). The orange layer is the troposphere, the white layer is the stratosphere and the blue layer the mesosphere. Space Shuttle Endeavor silhouetted against Earth’s atmosphere. But in truth, Earth’s atmosphere is made up of five main layers – the Troposphere, the Stratosphere, the Mesosphere, the Thermosphere, and the Exosphere – the latter of which extend pretty far out into space. When we talk about Earth’s atmosphere, we tend to think of the region where air pressure is still high enough to cause air resistance, or where the air is simply thick enough to breath. These varying definitions are complicated when one takes the definition of the word “atmosphere” into account. And in 2012, when Felix Baumgartner broke the record for the highest freefall, he jumped from an altitude of 39 kilometers (24.23 mi), less than halfway to space (according to NASA’s definition).īy the same token, space is often defined as beginning at the lowest altitude at which satellites can maintain orbits for a reasonable time – which is approximately 160 kilometers (100 miles) above the surface. ![]() This altitude was later adopted as the Karman Line by the World Air Sports Federation (Fédération Aéronautique Internationale, FAI). Shortly after that definition was passed, the aerospace engineer Theodore von Kármán calculated that above an altitude of 100 km, the atmosphere would be so thin that an aircraft would need to be traveling at orbital velocity to derive any lift. Credit: NASAĪny NASA test pilot or astronaut who crosses this altitude is awarded their astronaut wings. ![]() The Bell X-1, in which Chuck Yeager “broke” the sound barrier in 1947. This was the altitude that airplane control surfaces could no longer be used, and corresponded to roughly 81 kilometers (50 miles) above the Earth’s surface. The first official definition of space came from the National Advisory Committee for Aeronautics (the predecessor to NASA), who decided on the point where atmospheric pressure was less than one pound per square foot. But exactly how far away is that? How high do you need to travel before you can actually touch space? As you can probably imagine, with such a subjective definition, people tend to disagree on exactly where space begins. So it is quite literally all around us.īy definition, space is defined as being the point at which the Earth’s atmosphere ends, and the vacuum of space begins. And if you think about it, Earth is little more than a tiny island in a sea of space. Astronomically speaking, space is really quite close, lingering just on the other side of that thin layer we call an atmosphere. Look up at the night sky, and what do you see? Space, glittering and gleaming in all its glory. ![]()
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