What does space lack that is commonly found on Earth?

Space lacks atmospheric pressure, which is a fundamental difference from conditions on Earth. On Earth, the atmosphere exerts pressure due to the weight of the air above us. This pressure is essential as it affects various physical phenomena, including the boiling point of liquids, the behavior of gases, and even the functioning of our bodies.

In contrast, space is a near-vacuum, where the density of matter is immensely lower and atmospheric pressure is essentially zero. This lack of pressure can lead to several implications, such as the inability to breathe without a spacesuit or the fact that liquids boil at much lower temperatures because of the absence of pressure.

While light, sound, and oxygen are also significantly different in space, the absence of atmospheric pressure is a defining characteristic that fundamentally changes how objects and beings behave in that environment. Sound, for instance, cannot travel through the vacuum of space because it requires a medium (like air) to propagate, but that is a specific consequence of the lack of air rather than atmospheric pressure itself.