The story of physics is, for the most part, a tale of ever-increasing confidence.
For 300 years, physics was all about observing and measuring —finding out how stuff works.
In the early 1600s, an Italian got the ball rolling, by measuring and observing
balls rolling.
Galileo, also timed pendulus, and dropped different-sized objects
off the leaning tower of Pisa to see what would happen.
And, despite upsetting the Pope —his ideas had apparently made God very crossed—,
Galileo's work became the rock on which modern physics is founded.
Later, free from angry Popes, Isaac Newton moved things on by abandoning balls
and embracing apples.
Why, he wondered, did they always fall downwards? Not sideways, or up.
By 1687, he had an answer; it was a force called gravity, which worked on balls
and apples. And planets, holding them in nice predictable orbits around the sun.
In the 1800s, James Clerk Maxwell cast his eye over more mysteries.
He showed how electricity and magnetism are related, and can be combined as
one force: electromagnetism. And that light had electric and magnetic parts,
and traveled in waves, like water.
Physics was now on a roll. New discoveries built on earlier ones,
and some even had practical uses: Newton's laws predicted the existence of Neptune;
Maxwell's work gave us radio and tv, and there's nothing much more useful than that.
Physicists seemed to have mastered the universe;
all that was left was to plug a few remaining holes.
But, by 1900, the holes were getting bigger. The latests discoveries didn't build on
the old ones. Things like X-Rays and radioactivity were just plain weird, and in a bad way.
All was not well in the world of physics. Top scientist Lord Kelvin saw dark clouds
hanging over the subject.
Then, in 1905, a Swiss patent clerk started a full-on storm.
26-year-old Albert Einstein tore up the script. First, he claimed that light is
a kind of wave, but also comes in packets, or particles. In the same year, he published
his famous equation: E = mc^2. It says that mass and energy are equivalent.
And if that wasn't shocking enough, he released the mind-blowing results of a
thought experiment. So, hold on to your heads.
It starts with the assumption that the speed of light in a vacuum is constant.
Now, imagine that someone watches a spaceship flying very fast. What they would see
is the ship's clocks running slower than their own watch; and the ship will actually
shrink in size.
But, for the astronauts inside, all would be normal.
Einstein said that time and space can change. They are relative depending
on who's observing them. This is special relativity.
Now, special it might have been, but it wasn't enough.
Albert had only just started. Next he showed how balls and apples weren't
the only things subject to gravity. Light, time, and space were also affected.
Gravity slows down time, and it warps space. The stronger it is, the more space is warped
and the more light is bent. Einstein called this "general relativity."
His ideas shattered traditional physics. He'd opened the door onto the weird world
of the quantum, where cats can both be alive and dead, where good plays dice,
and where everything is uncertain.
His famous equation lead to nuclear energy.
Without special relativity the Large Hadron Collider would be pointless.
General relativity predicted both black holes and the Big Bang, an idea now endorsed
by both Church and science.
Galileo would have been pleased. Well done, Albert.