Is Earth expanding?

The answer, simply put, is no, we are not expanding! If you think the reason for this is gravity, then you’re correct, though only partially. Here, we are going to discuss the other forces at play that prevent us from expanding.

Examining gravity

We learn in basic science that gravity is what causes things to fall down on Earth. As we take higher physics classes, we then realise that gravity does not only cause things to fall down to Earth, but it also provides stability for the orbits of planets in the Solar System (due to the gravitational pull of the Sun and the planets). However, gravity is more than these concepts, and further understanding of gravity is needed to understand why we are not expanding.

Space is not entirely flat, but it is woven together with time in a so-called space-time fabric. The video above (courtesy of Kurdistan Planetarium) shows the space-time fabric as curved due to the presence of the Sun, which defines a mass. The Earth revolves around the Sun because of this curved space-time caused by the Sun. This is Einstein’s interpretation of gravity in his General Theory of Relativity.

So back to the question, the main reason why we are not expanding, is because expansion does not rule over the other forces in smaller scales. Gravity rules over versus expansion in the scales of planets and stars, while in very miniscule scales (atomic scales), other forces like electromagnetic and nuclear forces dominate versus the expansion of the universe. At very huge scales (comparable to the observable universe), expansion rules over versus gravity. This is also the reason why the galaxies in the Local Group do not move away from each other.