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UPDATE: We got a couple of things wrong when it comes to gravity (particularly that it has nothing to do with photons). Check out this video from TheGentlemanPhysicis ( in which our confusion is explained. We also did a whole video about gravitation in our series on the four fundamental forces of physics, which you can watch here:

Science is working tirelessly night and day to disprove its own theories about how the universe works (or at least, that's what science thinks it's doing). Hank tells us a quick history of how we came to create and adopt the scientific method and then gives us a vision of the future of science (hint: it involves a lot more computers and a lot less pipetting).

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 Introduction (00:00)

Hank Green: Science isn't, like.... Science is more of a process, a process of learning about the universe and organizing that information so that we can build on it. And, just like most process, there is an accepted way of doing scientific investigations on everything from the movement of atoms to the mating habit of tree frogs. This technique is called the scientific method, and it's got its rules just like golf and the US postal system.

As much as we take the scientific method for granted, the fact is that it took thousands of years for us to figure out how to actually practice the discipline of science, and it served us pretty well; a lot of what we know about the world has been discovered and tested and verified through the use of the scientific method, or at least versions of the one that we use today.

But of course, not all scientific knowledge has come to us through this method. Many revelations came about because of flashes of inspiration or just plain luck, rather than by testing theories in labs. What's more, some experts say that the scientific method can only take us so far; that we as a species have reached a level of understanding that requires new methods to help us get to the finer truths of how the universe works.

So I have news for you: the scientific method is not perfect, but it's the best thing we have for now.

[intro music]

 The Scientific Method (01:16)

The scientific method is all about coming up with a plausible explanation for an observed phenomenon, and then shooting that plausible explanation with a machine gun full of facts and questions until you either (a) destroy that seemingly plausible explanation or (b) decide that it's indestructible. So science is working tirelessly, night and day, to disprove its own theories about how the world works -- or at least, that's what science thinks it's doing.

When you wanna find out something about the natural world, for example, why your dog is always dragging his butt across the floor, a scientist will advise you to go through a series of steps to find the answer.

Step 1: Ask a question. Why is my dog always dragging his butt across the carpet?

Step 2: Do some research. Checking out the pet health websites, asking other people why they think their dogs wipe their anuses on the carpet...

Step 3: Propose a possible but testable explanation, AKA a hypothesis. In this case, maybe he has worms.

Step 4: Test this hypothesis with experiments until you've disproven it. Like, put his poop under a microscope and see if there's worms under there, or give him some deworming medicine and see if he stops soiling all the floors in your house. That's called collecting data.

If he doesn't stop after you've dewormed him, you can probably consider that hypothesis disproven, so then you come up with another hypothesis and collect some more data on that. Each time you prove an idea wrong, you come up with another hypothesis and test, until...

Step 5: Your dog quits wiping its butt all over the carpet, and you can analyze the data you collected to draw a conclusion, like he was just trying to express a blocked anal gland, or he's just a bit of a perv, or whatever your data suggests.

And there you go. Science accomplished! You can go ahead and make your conclusions known to the scientific community now because you just did the scientific method.

All of this sounds pretty reasonable because that's what we're used to, but that doesn't mean that science was always done this way.

 The History of the Method (03:02)

Some people credit Aristotle with inventing the scientific method, because he was the first to say, "Hey! Truths about natural phenomena can't be discovered just by thinking really hard on your couch. You have to go experiment, like, go out there and make some observations." Aristotle basically came up with the prototype for the scientific method, but by present-day standards, he was sort of a terrible scientist. We know that because almost all of the stuff he wrote about was wrong, like that time he said that females were just anatomically deformed men. Yeah. But his idea that theories could only be proven through experimentation and observation, called "empiricism", eventually took hold.

The problem was that empiricism was really most useful when lots of people were gathering data and sharing that information. This meant that science could only grow as fast as information could spread, and back in the days before the Google machine or the Pony Express or whatever, information spread like snails on NyQuil. Slowly, is what I'm trying to say.

Like, we think of the Middle Ages as being a time when everybody just sat around getting the plague and watching the Roman Empire collapse, but in fact the dark ages of European science were actually the golden age of Arabic science. Muslim scholars preserved the knowledge that had made its way from ancient Greece and built upon it while the Europeans were mostly on intellectual hiatus.

In fact, if you wanna call somebody the father of the scientific method, the best candidate would probably be tenth century Arab scientist Ibn al-Haytham. Ibn al-Haytham did amazing work on light and optics, a topic on which he wrote seven books. He used math to prove that we see light that enters our eyes and not because light comes out of our eyes, which was the prevailing theory of the day. He also developed a method for his inquiries that was based on first gathering data through observation and measurement followed by formulating and testing hypotheses to explain what he observed. Basically, he invented a stripped-down version of what we roll with today.

By the time Europeans were back in the game intellectually, a few key figures in Europe took the mantle of empiricism and fueled the scientific revolution, a period between the 16th and 18th centuries when, finally, the scientific method had been refined to a point where actual stuff could get figured out.

This was science's first real heyday. Galileo studied astronomy and physics; Robert Boyle argued that it didn't matter how you felt about a theory or how beautiful it sounded, but only whether it could be backed up by experimentation; Francis Bacon argued that science was only science if it was trying to prove itself wrong; and Portuguese physician and philosopher Francisco Sanches coined the term "scientific method" in 1581 to describe the process of gathering and judging data in an attempt to understand the world.

But arguably the centuries-long revolution peaked with Isaac Newton. His laws of motion and gravitation totally changed the game, obviously, but in his famous book Principia he also laid out what basically became the official rules for scientific reason, rules like "all things that create the same effects can be assumed to have the same basic causes" and "if you observe the same qualities in different bodies through experimentation, you can assume that all bodies everywhere have those same qualities", and, last but not least, "theories based on observation should be considered accurate until they are refuted by other observations".

So, the scientific revolution made the scientific method pretty much what we know today, and as a result, scientists gradually just started being scientists, not knights who happened to write books or monks who did genetics on the side. They also began following specialized disciplines, like chemistry or biology.

 The Problems with the Method (06:24)

But here's the weird part: Even though great science was being done using the scientific method, a lot of incredible discoveries were made without it. Take Marie Curie's insights into radioactivity, Albert Einstein's theories of special and general relativity, Nikola Tesla's AC induction motor, Alan Turing and the computer, and Richard Feynman's famous Feynman diagrams.... All these scientists made discoveries either as a result of putting together pieces that had been discovered by others or just because they saw the world a little differently than everybody else. In other words, those discoveries were made not through subjecting an idea to the method but by creativity and a certain amount of serendipity, both concepts that would have made old-school empiricists kinda uncomfortable.

By the 20th century, scientists were beginning to find that the scientific method wasn't really applicable to some of the problems that we were trying to solve. By that time, scientists weren't trying to figure out where babies came from, like Aristotle was, or what made apples fall from trees; they were trying to refine our knowledge of the universe, and those finer details can get tricky to hypothesize about and experiment on.

In 1962, American physicist and philosopher of science Thomas Kuhn suggested that there wasn't necessarily anything wrong with the method, but that we were putting too much pressure on the method to do all of science's work. Kuhn suggested there were different phases of science, the first just being "normal science", which followed the scientific method and tested hypotheses with experimentation, and everybody in a particular field had a shared understanding of their discipline. Within this framework, scientists got to the bottom of what was already known with more and more precision, and when something came up that seemed to go against how they understood the world, they either put it aside or treated the anomaly like a little knot, picking at it with the scientific method, observation-hypothesis-experiment. The only problem was that these unresolved anomalies tended to pile up and become so conspicuous that some scientists began to question what they thought they knew.

Take gravity, for example. Newton figured out how it worked -- the apple is being pulled toward the Earth while the Earth is being pulled toward the apple. [see footnote] Everybody used that framework for 200 years, until the anomalies started piling up. For instance, based on how the planets interacted with each other and how light bent in space, Newton's view didn't seem to be true anywhere except here on Earth, so Einstein came along and suggested the existence of photons, which pulled less massive objects toward more massive objects, and even pulled objects with no mass toward a massive object -- all ideas which Newton would have definitely objected to. And lo! classical mechanics made way for quantum mechanics, and physics has never been the same.

So, Einstein theorized creative possible solutions where the scientific method had left us high and dry. This is what Kuhn called a "paradigm shift", where a complete change in the assumptions made about a certain area of science. During one of these shifts, scientists are willing to try anything, entertain any crazy notion, debate everything we took for granted to explain an anomaly. And in the end, there's a change in how everybody sees the world, and the old way of thinking is replaced with a new one. Then normal science takes over again, observation-hypothesis-experiment. The scientific method's equilibrium is restored.

 Computers in Science (09:23)

Since Kuhn, though, more changes have been made to how we do science, and I'm talking about computers here. Lots of them. Because at this point, a robot can actually do science all by itself.

In 2009, scientists in Wales built a robot that could successfully formulate a hypothesis, design and run its own experiments, analyze its data and decide which experiments to run next. Of course, the discoveries made by this computer were pretty modest revelations about the purpose of different yeast genes, but the point is, computers are the future of science. I mean, like, take CERN's Large Hadron Collider, that thing that's been turning out a gigabyte of data per second, enough to fill up a DVD every five seconds. That data is being sent to labs all over the world for analysis. There just aren't enough human scientists on the planet to process all that information.

So if computers were the ones actually doing the scientific method, human scientists would be freed up to do the cool stuff, the collaboration, the creative thinking, the serendipitous observing, the strategizing about what steps to take next. At the very least, they'd be doing a lot less pipetting.

And that would obviously change a lot about how we think about science. It would affect everything from the skill set we look for in a scientist to the way that science is taught in schools. It would basically change the definition of science, at least as far as humans are concerned. And as dependable and comforting as the scientific method is to have around, and as much as I love pipetting, that's kind of an exciting prospect.

 Ending (10:44)

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[outro music]

 Footnote (08:18)

On-screen annotation: Gravity is super confusing, and this explanation is over-simplified (and a little wrong) -- to see a better explanation, see our full video on gravitation in our series on the four fundamental forces of physics