Suppose that you have an idea. Not necessarily a wonderful, awful idea, but an idea that seems like it could completely change science as we know it. And why not? It’s been done before.

My advice to you is to be very very careful. Because if you’re not careful, your revolutionary idea might force you to explain much much more than you expect.

Let’s consider an example. Suppose you believe that the universe is only six thousand years old, in contrast to the 13.772 ± 0.059 billion years that scientists who study the subject have calculated. And furthermore, imagine that you’ve gone one step further: you’ve found evidence!

Being no slouch at this sort of thing, you read the Wikipedia article linked above, and you figure you’ve got two problems to deal with: extrapolations from the expansion of the universe, and the cosmic microwave background. Let’s say your new theory is good enough that you can address both of these: you can explain why calculations based on both of these methods give 14 billion years, while you still assert that the universe is only six thousand years old. You’ve managed to explain away all of the tests that scientists used to establish the age of the universe. If you can manage that, you’re done, right?

Not quite. Explaining all the direct tests may seem like great progress, but it’s only the first step, because the age of the universe can show up indirectly as well. No stars have been observed that are 13.772 billion years old, but every star whose age has been calculated has been found to be older than six thousand years! And even if you can explain why every attempt to measure a star’s age turned out wrong, there’s more to it than that, because the age of stars is a very important part of how astronomers model stellar behavior. Every time astronomers make a prediction about a star, whether estimating its size, it’s brightness, its color, every time they make such a prediction and then the prediction turns out correct, they’re using the fact that the star is (some specific number) much much older than six thousand years. And because almost everything we can see in space either is made of stars, or orbits a star, or once was a star, changing the age of the universe means you have to explain all those results too. If you propose that the age of the universe is only six thousand, you need to explain not only the cosmic microwave background, not only the age of stars, but almost every single successful prediction made in the last fifty years of astronomy, none of which would have been successful if the age of the universe was only six thousand.

Daunting, isn’t it?

Oh, we’re not done yet!

See, it’s not just astronomy you have to contend with, because the age of the Earth specifically is also calculated to be much larger than six thousand years. And just as astronomers use the age of stars to make successful predictions about their other properties, geologists use the age of rock formations to make their own predictions. And the same is true for species of animals and plants, studied through genetic drift with known rates over time, or fossils with known ages. So in proposing that the universe is only six thousand years old, you need to explain not just two pieces of evidence, but the majority of successful predictions made in three distinct disciplines over the last fifty years. Is your evidence that the universe is only six thousand years old good enough to outweigh all of that?

This is one of the best ways to tell a genuine scientific breakthrough from ideas that can be indelicately described as crackpot. If your idea questions something that has been used to make successful predictions for decades, then it becomes your burden of proof to explain why all those results were successful, and chances are, you can’t fulfill that burden.

This test can be applied quite widely. As another example, homeopathic medicine relies on the idea that if you dilute a substance (medicine or poison) drastically then rather than getting weaker it will suddenly become stronger, sometimes with the reverse effect. While you might at first think this could be confirmed or denied merely by testing homeopathic medicines themselves, the principle would also have to apply to any other dilution, meaning that a homeopath needs to explain everything from the success of water treatment plants that wash out all but tiny traces of contaminants to high school chemistry experiments involving diluting acid to observe its pH.

This is why scientific revolutions are hard! If you want to change the way we look at the world, you need to make absolutely sure you aren’t invalidating the success of prior researchers. In fact, the successes of past research constrain new science so much, that it sometimes is possible to make predictions just from these constraints!

So whenever you think you’ve got a breakthrough, ask yourself: how much does this mean I have to explain? What is my burden of proof?