Today E=mc^2 is Einstein's most famous equation but another thoery he published the same year is more important and more controversial ,
the special theory of relativity.
When Einstein was a teenager he enjoyed imagining what it would be like to ride a beam of light.
Now he returns to this daydream and changes his life.
In the spring of 1905 Einstein was writing on a bus and he looked back at the famous clock tower that dominates Bern Switzerland .
And he imagine what happens if that bus racing at the speed of light.
In his imagination Einstein looks back at the clock tower and what he sees is astonishing.
As he reaches the speed of light the ends of the clock appear frozen in time .
Einstein later writes the storm broken in my mind.
All of sudden all of sudden everything everything can gush in forward.
Einstein knows that back to the clock tower time is passing normally.
But on Einstein's light speed bus as he reaches the speed of light,
the light from the clock can no longe catch up to him .
The faster he races through the space the slower he moves through time.
This special insights sparks the birth of Einstein special theory of relativity which says that space and time are deeply connected.
In fact they are one in the same,
a flexible fabric called space time.