Atomic Core Reactions

[Light Storm]

It is well known that stars expand as they grow old. Since it is also accepted widely that the earth’s core is molten and hot like a star, it too could be going through some type of atomic process which is making it expand. This process is could explain the sudden and exponential increase of the earth during the last 200 million years.

[Florian]

Stars are thought to expand at the end of their life, because they start to fuse helium into carbon. The energy released changes the balance between gravity and internal pressure.
If the core of Earth is modeled to be as hot as the surface of a star, it is not as hot as the core of a star. So the same kind of reaction happening in a star can't take place inside Earth.
Moreover, the expansion of Earth is not so sudden. In the expanding earth theory, tectonic activity is related to the expansion.
Since geological records show that Earth has been a tectonically active planet most of its life, it follows that Earth must have been expanding most of its life.