What would happen if someone discovered the world wasn't real?

What if the world/universe/everything was just an illusion?

Someone discovers that we aren’t really here, but we are a part of something much bigger than anything our minds have ever been able to comprehend.

Or say someone discovers that the world we experience when we are awake is actually not reality, but the world we experience when we are asleep is…

Is there even a way of discovering this?
Could there ever be?

Are we even living? What if the after-life is the real life, and this is just a dream from our deceased selves? Oh man.

Would discovering something like that change life as we know it? What do you think would happen as a result?