Fact vs. Theory vs. Hypothesis vs. Law… EXPLAINED!
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Fact vs. Theory vs. Hypothesis vs. Law… EXPLAINED!

[MUSIC] We need to get something straight. Evolution by natural selection is a theory.
So is climate change. But people keep saying that like it’s a bad thing… [MUSIC] I get it, I understand your frustration. We’re
all searching for ultimate hashtag #truth, and complex, challenging ideas don’t always
fit nice and neatly in our brains. But what is truth? Are there different levels
of truth? Are some truths truthier than others? I don’t know. But I do know this: Science
is the absolute best tool we have for understanding how the universe works, and theory is not
a 4-letter word. If we’re going to trust science together,
the least we can do is speak the same language. Words like “fact” “theory” “hypothesis”
and “law” mean something totally different to a scientist than the way they’re used in
everyday speech, so let’s get them straight. Facts are really just observations about the
world around us. And we observe things every day, like that
it’s bright outside when I look out the window, and we often develop explanations
for those observations , like “okay, the sun is probably up”
Congrats! We just developed a hypothesis! But a hypothesis isn’t something you prove,
it is something you test. So… let’s walk outside! It’s bright, the sun is up, hypothesis confirmed! Way to go! We did a science! [MUSIC] We often come up with multiple hypotheses
to explain an observation, we just eliminate the ones that are wrong. What’s left over
is not a theory or a law or an “Ultimate Truth”, it’s just a possible explanation for something,
one that can lead us to new hypotheses, which may agree or disagree with the original one.
It’s a never-ending story… only without the big fluffy dragons. “That’s so good!” When enough hypotheses have gotten the ol’
scientific check mark, we can pile these all up and turn them into something greater: a
theory. A theory is the way we know something works,
based on the evidence we’ve collected and all the hypotheses that we’ve successfully
put to the test. The best thing about a theory is that we can use it to make predictions,
and not just about the way things are, but how they will be. You may have heard someone say something like,
“I have a theory about why cats purr, I think it’s because they’re actually tiny
robots, and those are their gears” Well that’s not a theory. That’s actually
a hypothesis, it’s something that could be tested. This cycle, taking facts and observations,
thinking up possible explanations, testing those explanations, and then making predictions
based upon them… that’s what this whole science thing is about! Being a theory isn’t a bad thing, it means
that idea got the gold star, the blue ribbon, a big shiny trophy that says “Countless
experiments have shown that I’m sufficient to explain all the observations that I encompass” To see if you’ve got this down, let’s
look at some examples. FACT: People get sick. I think we can all
accept that. HYPOTHESIS: People get sick because something
gets in their body and starts doing bad things. Test each hypothesis, throw out the bad ones,
and we’re left with a framework that lets us understand why we get sick and make predictions,
the Germ Theory of Disease. Let’s try another! “Evolution” is a fact. We know that it happens,
no doubt. But how does it happen? “Evolution by natural selection” is a theory.
We’ve come up with thousands and thousands of hypotheses about it, tested them, thrown
out the bad ones, and we’ve developed a pretty darn good framework for predicting
how living things change over time. So yeah it’s a theory. Stop saying it like
a bad thing. Calling it a theory means it’s passed the toughest tests that we can throw
at it, and evolution has been tested maybe more than any other theory we know of. We should really call it the Theory of (The
Fact of) Evolution What about something as fundamental as gravity?
Is that a theory? Or is it… a law? In science, a law is a detailed description,
usually using math, of how something happens, like the movement of gas molecules related
to temperature, or how mass and energy are always conserved. But a law doesn’t tell us
why it happens. Gravity, it turns out, is a law and a theory. Newton’s Law of Universal Gravitation describes
precisely how two objects will attract each other based on their masses and the distance
between them, and gives us a nice formula we can use to figure it out. Textbook “law”.
But Newton’s equation doesn’t describe what is happening, or why. To do that, we need
a theory of Gravity. FACT: If I drop this, it’ll fall. LAW: I can mathematically describe how fast
that apple and Earth will accelerate toward one another based on their masses and distance. But why is it happening? HYPOTHESIS: There is a force pulling on the
apple, or maybe there’s something about the way the universe is structured that makes
massive things fall toward one another, or maybe the apple is, like, magnetically attracted
to Earth or something? Eliminate the bad ones, and we’re left with
a theory. Thanks to Einstein, we’ve got a Theory of
Gravity… called General Relativity. But once scientists stumbled upon quantum
mechanics, they began to realize that Einstein’s Relativity didn’t account for what was happening
on the very smallest gravitational scales of the universe. General Relativity is still great at describing
the universe at the scale that we interact with it, but even the Theory of Gravity is
incomplete. Does that mean we throw it out because it can’t explain everything? No! If you get a flat tire on your car, do
you get a new car? If you change the tire, is your car a different
car all of a sudden? All of these fit together to make the scientific
machine. We’re constantly adding and taking away parts, but it keeps on running just fine.
It just means we’ve got more work to do to make Einstein’s theory even more right. Science is never done. It is always changing,
and this bothers some people. How can we trust it, how can something be strong and robust
if it could be different tomorrow? The goal of science is to devise frameworks
that describe how things work, to truly understand why things are the way they are right now,
so we can know how things will be in the future. And if we can all learn to trust science,
in all its fuzziness and incompleteness, I predict that future is going to be very bright.
I like that theory. Stay curious.


  • Stormspark

    It's very rare for a theory to be proven wrong, because they have to pass so many tests to get to that point. What IS common, is for a theory to be incomplete. Look at Newtonian gravitation. It seemed to be right, it passed all kinds of tests, but didn't work when high speeds or large gravitational wells were involved. Does that mean it was wrong? No, it was just incomplete. It perfectly described the situations we encounter in every day life. GR superceded Newtonian gravitation. But…in the GR equations, if you make certain assumptions about conditions, it reduces to Newtonian gravitation. Some day GR will be superceded by M-theory or something else that explains quantum gravity. Does that mean GR is wrong? No, it just means it's incomplete. Indeed, right, M-theory reduces to GR if you make certain assumptions about conditions. M-theory is a long way off because it's still extremely incomplete, it probably won't be completed in the lifetime of anyone living today, but it will be.

  • Ahmed Osman

    What made evolution by nature selection a Fact ?! …. People get sick that something we can observe but how did we observe evolution by nature selection ?! I know we have observed evolution by adaptation but that is not the same thing

  • Salman Ahmed

    How can evolution be a fact as observing a broad day light. If we are not sure of the mechanism how can that leads to the fact. Evolution suggest changes in kinds over a period of time from a single organism that is a huge claims if it was really true we would have to worry about to go in labs to test it because many of the species still be in the process of evolution which can be easily observable every where this is what Darwin suggest in this "difficulties: why there are not so many species in intermediary stages". If thing has to take millions of years how are we gonna test it if we cannot test it how can we be sure this is the fact. Since we have both live can we make a cockroach into a centipede in lab with all the knowledge we have if we are so certain this is the truth. Remember they both are insects this will be an easy test. even easier can be turn E.Coli into Gardia Histolaycia there both are microorganism. Stop calling it a fact this is not a fact but an ancients myth goes back to Hindu mythology to Pythagoras and in the end to Darwin.

  • Bob

    FACT: There is a lot of people born without a brain. This results in their comments to go against the definition of logic and intelligence.

  • Bob

    FACT: people with a chemical imbalance in the brain or lack of are often attracted to spew their nonsense on social media sites such as Twitter.

  • Rodney lee

    Still wrong ,sounds good 4 mind controll parrots of same old explanation are faith in programming by so called scientists.

  • phillip king

    CO2 (AGW) proved wrong … i.e. the computer models proved wrong
    Algae as a climate effect would be much better proposition for science


    Evolutionists assume that the small, horizontal Microevolutionary changes (which are observed) lead to large, vertical macroevolutionary changes (which are never observed). The Latter which {i suppose } they are making reference of at @3:32 is NOT a FACT suffice to say macroevolution does not and did not happen.

  • Mr. Caligos

    You forgot about that, that after the theory comes again fact when the theory is proved to be true and then it is not just about predictions but about the real reality. You can call it proved theories or scientific facts, laws or whatever (depends what it is). Then those proved theories which came to be facts can be again used for another hypothesis. It's a neverending circulation. But the humanity is so dumb that there were no circulations yet. 😉

  • Mr. Caligos

    fact: That thunderstorm created a fire!
    hypothesis: I could maybe create it too!
    theory: The wooden sticks and some straw should do the magic!
    fact: It did!
    hypothesis: Now I could use this advantage for something else!
    theory: I should be able to cook the meat in it!
    fact: I did and it is delicious!
    hypothesis: What if I add some ingredients?
    theory: The weed should make it spicy!
    fact: It didn't but I can't control myself anymore!

    PS: But you know what. Some crazy scientists would even consider the effect of the weed as hypothesis even if they tested it on themselves. And actually everything started with hypothesis when the braindead zombies didn't know how to describe or explain those things around them which they perceived.

  • sparkyy0007

    Evolution is a fact, We observe the positive effects of mutations all the time like aging…causing…err…death….. never mind.

  • David Sims

    Geoenginers spray heavy metals into the atmosphere to reflect the sun. One being aluminum. Humans then breath eat and ultimately absorbs these metals. They in turn end up in your brain and cause Alzheimer's Parkinson's and dementia. Germ theory explodes. Theory is just like saying I think when you don't. Theory of evolution has never been documented.

  • Ron Kreike

    Q: If there would be a redshift because of distance, then galaxies that are moving away seem to move away with increasing velocity…
    If so, it is a fact that has been overlooked for some years?

  • TheMessage2011

    another government funded you tube channel with beautiful graphics, gravity is only a theory, earth is level, just like the natural physics of water

  • Lazar Gajicic

    Can someone please explaion this to me. I don't understand how can multiple hypothesis become a theory? Isn't a theory made from single hyposthesis after it's been tested?

  • John Carboni

    a theory is just a theory, get over it – https://www.google.com/search?q=theory+definition&rlz=1C1NDCM_enCA842CA842&oq=THEORY&aqs=chrome.5.69i57j0l5.5222j0j8&sourceid=chrome&ie=UTF-8

  • Sam Ryan

    Notice how he says ”throw out the bad ones”? Really what he's saying is when ideas are put in front of you take the ones that sound good, claim them as fact, whether or not it is true, and throw out the ideas that make you uncomfortable even if they are true.
    Example: cows throw up their first course then make it they're second. It's gross but why cause cows are not humans.

  • Justin Aime

    Only the simplest people reference evidence for evolution by natural selection. You don't need any evidence. If you can't reason how evolution by natural selection is inevitable, then you lack either a correct understanding of the relevant concepts, any analytic ability whatsoever.

  • ahmed hussein

    Facts are [[observations]] about the world around us
    Macro evolution is a [[fact]]
    يا سلام إنما قصة بنت متناكة بصحيح

  • François Cardinaud

    The problem is that many people aren't intellectually honest enough to accept certain facts, and dismiss them as opinions :'(

  • The Conservative

    So basically you still didn't prove that "theory" equates to absolute truth.

    So basically evolution is still not truth and could be completely revoked later on with a better understanding of the universe

  • Sunix

    So, it should be called the "hypothesis of evolution" given that there isn't any evidence for evolution which is testable or repeatable. Perhaps the "wishful thought of evolution" would be a better title for the hypothesis.

  • allah satangod

    It's Ok To Be A Dumbass.
    I'm a skeptic. I need videos of macro evolution taking place…
    I love evolution in my sci-fi.

  • rubiks6

    I can trust science just fine. What I cannot trust are scientists. They are human and chock full of reasons to be dishonest.


    This is stupid. He first says it's a fact because he can see people get sick: observable. Then claims evolution is a facr; not observable. This video should never be in a school.

  • betaneptune

    Well, there are a number of problems with this video. Scientists have been somewhat sloppy with the terms theory and law and such. What about theories like phlogiston theory, geocentric theory, and string theory? Phlogiston theory is simply wrong. Geocentric theory is empirically correct, but it is not consistent with Newton's laws of motion and it cannot make predictions of or about undiscovered phenomena. String theory is certainly not well substantiated by any standard, and it has yet to make any testable predictions. But it is still called a theory. But it's a working theory. A theory in development. A complicated hypothesis. And it comes in more varieties than there are string theorists (or so the joke goes). But it's still called a theory, as are phlogiston and geocentrism! (There's also flat earth theory and the stork theory of where babies come from. They're theories, but they're bogus theories.)

    I beg to differ with your claim that Newton's Universal Law of Gravity is not a theory. It most certainly is. It is well substantiated and makes predictions. Some of these predictions cleared up mysteries of what were already known phenomena. Others tell us about things yet to be discovered. The prediction of Neptune was a triumphant victory for Newton's theory. It was based on the fact that Uranus's orbit was slightly off from Newton's predictions. A couple of people independently used the theory to calculate where and with what mass an undiscovered planet would have to be to cause Uranus's slight deviations from the initial predictions. They told their respective observatories where to look to see Neptune. "Point your telescope there and you will see a planet." One of the observatories did just that and there was Neptune! Geocentric theory cannot do anything like these things. Still called a theory, or at least a model. So I think a fair definition of a theory is a model that makes predictions, be they verified or not, our even outright refuted.

    Newton's theory of gravity also makes predictions about the motion of stars. It makes predictions about the behavior of things we haven't seen. If we discover a new planet, or a new moon, or a new comet or asteroid, Newton's laws will tell us how it moves. The theory also explains what were previously mysteries, like the precession of the equinoxes, the tidal bulge of the earth, tides, and more.

    So how dare you say that Newton's Universal Law of Gravity is not a theory!!! (^_^) It is very well substantiated and makes predictions. Yes, it fails in extreme cases, which is where Einstein's theory comes in, but in most ordinary situations, Einstein's theory becomes Newton's theory, and Newton's theory then works extremely well.

    No, we don't know how masses create a force, but at the same level we also don't know how matter curves space and how space tells matter where to go! So both Newton's law of gravity and Einstein's are on the same footing in this sense, making both of them theories.

    Perhaps the worst part of this video is that it asks why we should trust science, and then just bails out when in fact that are excellent reasons to trust science: Science works. Cars go. Planes fly. Medicines cure. Electric generators generate electricity. Lasers and transistors do their wonders. And so much more. Most of our technology is based on science, and it works because science works. Too much attention is paid to the latest epidemiological studies about diet and disease. These things are at the forefront of science, where things are still being figured out. And they are probably published on slow news days. This is why they seem to contradict each other. But there is a vast trove of established science in many areas, ando not just about diet and disease. And notice that at least the press is honest when they say, "such and such MAY cause so and so." Note the word "MAY." This means it's in the hypothesis or development stage. It is not yet to be taken as fact. Oh, and epidemiology is very difficult. It takes a lot of work and often requires multiple studies to glean anything useful. And the "after correcting for . . ." always adds some doubt — in my mind, anyway.

    Here's an interesting segment of a video in which Steven Pinker gives us other reasons to trust scientists (and thereby science):


    (FF to 5:56 to hear Pinker's spiel on this. The feature to include that in the URL somehow doesn't work for this video.)

    As for evolution, I think it's fair to say that it is a FACT that evolution has occurred and is still occuring. The theory of evolution explains how it works, but the notion that evolution is fact is now well beyond any reasonable doubt. The evidence in its favor is overwhelming, even without the fossil record! Now, we don't understand it in every detail, but we don't understand anything in every detail. So we shouldn't let that stop us from concluding that evolution is a fact, just like the earth is rotating and orbiting the sun.

    For better or worse, initial names tend to stick. You dial a phone number because the first phones had — you guessed it — a dial! And we would dial a phone number using that dial! Now we tap the screen of our phone to call a number, but we still call it dialing. Newton's law of gravity might be called Newton's theory of gravity if it were developed today. But it wasn't and for whatever reason it is called a law. So people should stop taking the exact word used too seriously. The particular names used are really just historical accidents, so to speak.

    Laws are another thing. You have Newton's laws, which need modification in extraordinary situations. You have the laws of thermodynamics. You have conservation laws.

    Oh, there's another kind of theory. Things in math like "group theory". This is a totally different kind of theory. It's a math thing. See https://en.wikipedia.org/wiki/List_of_mathematical_theorieshttps://en.wikipedia.org/wiki/List_of_mathematical_theories for a big list of them.

  • wujidao

    Wrong from the outset and seemingly all the way through. All your theories are hypotheses, some of them have become laws based on the weight of empirical evidence, but none of them are theories/theorems which may be "proved" mathematically or otherwise.

  • LogicalNotes

    Where’s the list to test the hypothesis of evolution? And where’s the “fact” for it? Because Darwin says so?

  • Rick Knight

    Uniformitarianism versus catastrophism.
    Macro evolution is not a fact .
    Creationists believe in micro evolution which is all we witness in science.
    Creationism is just giving credit how it all began.
    Naturalism just gives random chance the credit..

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