Mach's Principle

Mach's Principle is based on the following : how do you measure a moving object? Well, you gotta measure it moving relative to a stationary object. But nothing is really stationary, so what do you use?

An idea, proposed by Bishop George Berkeley and popularized by Ernst Mach, is to use the most distant star possible. That is Mach's Principle, version 1.0 - you measure acceleration relative to the most distant point you can measure. Simple enough, right?

Now, when you accelerate something, it produces 'inertial forces' - i.e. it wants to stay at rest, so it pushes back against the force that's pushing it. Where does this force come from? If you take the acceleration relative to a distant star, then you must account for the star's actions on the accelerating object. That led people to think about how other masses in the universe affect each other. What was theorized - that everything else in the universe affects (by gravitation) the object that is being measured. That's what creates the inertial force. And this idea became Mach's Principle, version 2.0.

Einstien applied his theory of relativity to the equation (while it still had that new-theory smell about it) and verified that an object accelerating will feel a slight gravitational force from everything else in the galaxy, even though other parts of the theory of relativity refuted Mach's Principle.

So, in short : When you feel like you can't get out of bed in the morning, that's because all the gravitational forces in the universe are acting on your wretchedly tired body. When things seem too tough to work against, that's because the rest of the universe is acting on the things you want to do, making sure they have plenty of inertia so you have to do more work to get anything to happen. And that's how, scientifically, the rest of the universe is against you.