There’s no Such Thing as Gravity:
The World Just Sucks!

A slightly different approach to general relativity
for high school physics students

By Mark Sowers

Chapter 4:
Exchange Rates

The speed of light (just over 186,000 miles per second in a vacuum) is a fundamental law of the universe. Every observer in the universe, no matter where they are, no matter how fast or in what direction they are traveling, will always measure the speed of light to be 186,000 miles per second. It is a law based on those changing electric and magnetic fields. It’s based on how quickly the electric field changes into a magnetic field, and on how far away that new magnetic field is from the electric field.

When we talk about the speed of light we are not talking about a number. We are talking about a ratio. It is 186,000 miles per second, and it’s the ‘miles per second’ part that makes this a ratio. It’s just like saying you can buy 5 apples for 1 dollar.

Imagine a law that states that no matter where you go, the ratio of apples to dollars is 5:1.  The ratio of apples to dollars remains constant, just like the ratio of miles to seconds remains constant. It can never change. I live in Pennsylvania and here I can buy 5 apples for 1 dollar. If I go on vacation in California, I can still buy 5 apples for 1 dollar. Everything’s the same. It always works as expected. There are no surprises and I can plan on this.

But what happens if I take a trip to Toronto, Canada? They still have dollars, but their dollars are different. Their dollars have a different value and if I want to buy things in Canada I need to trade my US dollars for Canadian dollars using an exchange rate. Let’s say the exchange rate is 1 US dollar = 1.20 Canadian dollars. I go to the bank, hand them a dollar and they hand me 1 dollar and 20 cents (Canadian). Cool! Now I want to buy some apples. The ratio is still 5 apples for 1 dollar (remember, that’s the fixed ratio that can never change), so not only do I buy 5 apples, but with the extra 20 cents I buy an orange.

I call this extra 20 cents ‘potential money’. As long as I am in the US, my dollar can only buy 5 apples. No supermarket in the US would be willing to give me 5 apples plus 1 orange for my 1 dollar. In the US I have no way of getting that ‘potential money’ out of my dollar. But if I move that dollar from one location to another (from the US to Canada), suddenly that ‘potential money’ becomes real. The value that was locked up in that dollar has now been released and I can use it to buy things. The extra 20 cents is now ‘kinetic money’.

I hope you see why I chose the terms potential and kinetic money. They of course relate to potential and kinetic energy.

A paper weight just sitting on the 7th floor of a building has no kinetic energy. It just sits there. There is no way a person on the 7th floor can get work out of that paper weight. But to a person on the 6th floor, that paper weight has ‘potential energy’. And to a person on the ground floor, that paper weight has a lot of ‘potential energy’. Three different observers see three different values.

The potential energy of an object is relative to the location of the observer. Remember this is relativity, where different observers measure different values for the same thing.

So what is it that is different about these three locations that makes them measure different values for the same thing? It’s true that their height (elevation above the Earth’s surface) is different, but that’s not an inherent difference, it’s just a relative difference.

The inherent difference between these locations is time itself.