We Create History By Our Observation

"We create history by our observation, rather than history creating us."
 
-Stephen Hawking

For those that want a little more, here is the full excerpt.

"The usual assumption in cosmology is that the universe has a single, definite history. One can use the laws of physics to calculate how the history develops with time. We call this the "bottom-up" approach to cosmology."

But since we must take into account the quantum nature of the universe as expressed by the Feynman sum over histories, the probability amplitude that the universe is NOW in a particular state is arrived by adding up the contributions from all the histories that satisfy the no boundary condition and end in the state in question.

In other words, one shouldn't follow the history from the "bottom-up" because that assumes there's a single history, with a well defined starting point and evolution.

Instead, one should trace the histories from the top down, backward from the present time. Some histories will be more probable than others, and the sum will normally be dominated by a single history that starts with the creation of the universe and culminates in the state under consideration.

But there will be different histories for different possible states of the universe at the present time.

This is a RADICALLY different view of cosmology, and the relation between cause and effect. The histories that contribute to the Feynman sum don't have an independent existence, but depend on what is being measured.

We create history by our observation, rather than history creating us."

(from the Book, "The Grand Design" by Stephen Hawking).