# Is the atmosphere a part of Earth?

My question is quite simple, but I can't seem to find any answer to it: how do we define the limit of the object "Earth"? More specifically, can we consider the atmosphere a part of it? Or even the oceans, for that matter? I was going for a no at first glance, but that would mean that you are actually leaving the Earth when you fly on a plane. That feels weird. How do scientists define the limit of the Earth?

• The density of the atmosphere gradually gets smaller as we move away from earth. To draw a line anywhere will anyways be artificial. In earth sciences earth is divided to spheres (like hydrosphere, atmosphere) and the outermost layer that is named (and thus can be thought as an attribute of earth) is exosphere and its upper limit isn't defined other than: where objects are still bound to earth's gravitation. – Communisty Apr 13 '18 at 13:02