What is the size of the observable universe? How do scientists know how big the invisible portion is if they can't see it?

The universe's apparent infinite size is based only on the number of stars and planets that it can support; scientists have no idea how big the universe actually is.

What you are saying may be true because scientists believe that the size of the universe's unseen regions is infinite. An astronomer, for example, discovers a new galaxy almost every hour when looking through a telescope.

Almost every assertion made regarding the space is merely a hypothesis!

The size of the observable universe is estimated to be about 93 billion light-years in diameter. Scientists infer the size of the invisible portion through mathematical models based on observations of the visible universe's expansion rate and distribution of matter, using tools like the cosmic microwave background radiation and measurements of cosmic structures.