Investigate the origin of the theory relativity with a mesmerizing interactive exercise.
The happiest thought of Albert Einstein's entire life is a man falling from the roof of a house!
But the reason this thought made Einstein so happy is that within it, he could see the key to a generalized version of relativity that would embrace the force of gravity.
Here's how I can think about it: Imagine that I am the guy who in just a moment Einstein will see falling from that roof.
But just before that, I'm on the roof standing on my bathroom scale.
I look down at the scale, and it reads 160 pounds.
Then, with the scale, velcro'd to my shoes, I jump.
And as I'm falling, I again look down at the scale, what will it read now? Well because the scale is falling right with meI'm unable to press down upon it, so the reading on the scale will drop all the way to zero.
By going into free-fall, I feel weightless.
And it's not just the scale --if I were to empty my pockets, everything will also fall right with me, so as I look over itll all be hovering right next to me exactly as it would if there were no gravity.
So in this sense, from my perspective, I have cancelled gravity out.
What about from your perspective?
Watching this from the ground?
You would surely say that there is gravity, right?
That's what's pulling on me, causing me to fall faster and faster, causing me to accelerate downward.
It's not as though one perspective is right and the other is wrong.
Both perspectives are right.
Yours and mine.
And therein lies the power.
By putting the two perspectives together, Einstein realized that there is a profound connection between acceleration and gravity.
You see accelerated motion --my falling faster and faster, and I see gravity being cancelled.