Lots of people believe it. Lots of people believe lots of things. Lots of important, authoritative people have believed things and offered their beliefs as evidence that the things were true. Upon testing, many things that many people have believed have been proven untrue. Examples abound throughout history. People have been executed for being right when lots of people believed otherwise. People have been called idiots (recently) for not accepting what other people believe without evidence.

The world is flat, and there is an eastern edge to the Atlantic Ocean beyond which one will fall into an abyss. The square root of two does not exist. The earth is the center of the solar system. These are but a few of the beliefs that have been strongly held by many people.

Other things that people believed without evidence have since been proven true. This may be true. But true or not, an untested hypothesis is conjecture.