If many people think something is true, is it true?

My answer shall be short and sweet: Not necessarily
I can prove this in one example but that would come later. I shall first start by elaborating why I feel so.
When people think something is true, its what they feel, there is no proof and that is what is really important in deciding if something is true. Why, then, do Scientists conduct experiments? If you can change the laws of Science just by getting the majority to think something is true, what would that make us? Gods? Quite obviously, we are not, so how can our thinking change the world and the laws that control everything on it? That makes no sense.
All that our thinking controls is our actions and beliefs, other than that, I doubt it can control anything. It is our actions that can change the thinking of others but that is the only thing one can control - our thinking. It is our thinking that affects the human race but nothing more. Our thinking can change the world but there are several things that cannot be changed.
The above may not have made any sense to you with regards to the question, but it just states that our thinking can change somethings but not others. Those things that we cannot control are the things which possibly control our thinking.
A simple conclusion: When we think something is true, sometimes it is, but other times it is not.
An example to prove each part of the conclusion:
Humans used to believe that the Earth was flat, almost everyone believed that but it is untrue.
Everyone thinks that humans will die. It is true, live with the fact.

"If something is true, it is true. If something is false, it is false. If everyone thinks something is true and it is, it is true. If everyone thinks something is false and it is, it is false."
-Conclusion Guy