Newton vs Einstein

newtonMy all-time favourite scientist was Isaac Newton. Newton was very clever. In fact he was a genius. He discovered lots of interesting and important things. Unfortunately, most of them turned out to be wrong. That doesn’t make him a bad scientist, of course. Finding wrong answers is an important way that science makes progress.

One of the reasons we know that Newton was a genius is that it took a very long time before anyone proved that he was wrong. Around 200 years, in fact. Then Albert Einstein (my second favourite scientist) showed that Newton was wrong, by coming up with some better explanations.

In science, things can get nasty, and Einstein really put the boot into Newton by proving each one of Newton’s theories wrong. In fact, it’s almost as if Einstein’s goal in life was to trash Newton’s achievements.

First, Einstein gave Newton a bloody nose by showing that light wasn’t simply a wave, as Newton had believed – Einstein showed that light can behave like a particle. Secondly, Einstein gave Newton a thorough kicking by disproving Newton’s celebrated Laws of Motion, with his own Special Theory of Relativity. And not yet satisfied with that, Einstein took a baseball bat to Newton’s Universal Theory of Gravitation, replacing it with his General Theory of Relativity.

Poor old Newton. Everything he thought was wrong. Or was it?

The reason why it took 200 years for anyone to think up a better explanation of the universe was that Newton’s laws seemed to work so well. In fact, NASA still uses Newton’s laws to plan spacecraft trajectories like the New Horizons mission to Pluto. But that doesn’t mean Newton’s laws are correct. They work well in certain circumstances (speeds that are slow relative to the speed of light; frames of reference that don’t accelerate too much; gravitational masses that aren’t too big.) In mathematical terms, Newton’s laws are linear approximations to Einstein’s laws.

Newton’s laws are an extremely useful mathematical tool. They even allow us to make calculations of spacecraft journeys. But they don’t describe reality, except in an approximate way. The world doesn’t really work the way Newton thought it did.

There are plenty of similar examples where a simple mathematical rule allows us to make predictions about the world. For instance, I can estimate the volume of an apple by assuming that it’s a sphere. That doesn’t mean that apples are spherical. They have much more interesting shapes, and each one is different. Nevertheless, my simple approximation enables me to estimate the volume of an apple, by measuring its “radius”. I can even estimate the volume of a cow by assuming that cows are spherical – the approximation isn’t as good in this case, but is still reasonable.

It’s the same with Newton’s laws. Newton’s fundamental model is wrong. Mass isn’t a fixed quantity. Space isn’t flat. Time doesn’t move forward at a constant rate. Yet under certain circumstances, assuming that they do is a pretty good approximation.

These equations are not the same!

Newton’s and Einstein’s equations are not the same!

So Newton was wrong. He didn’t explain how the world works. What he did do was invent some incredibly useful rules that enable us to make detailed calculations of how the world behaves in many cases of interest. He also dismissed a lot of previous misunderstandings. It took a genius to do that, and I don’t want to cast the slightest doubt on his achievements. As I say, Newton’s my favourite all-time scientist.

As for Einstein, he was wrong too. He even knew that he was. The Theory of Relativity doesn’t explain how the universe works either. It’s another approximation, that’s all. Inside a black hole, or in the moments before and after the Big Bang, it all breaks down. What we need next is a theory of quantum gravity. That might be string theory, or loop quantum gravity, or asymptotic safety, or one of many ideas being bounced around the physics world right now.

Of course, these might all be wrong. Eventually some theory will emerge, but even this might be wrong. It may not explain everything.

Ultimately, we have to wonder whether the universe really is mathematical, or if these mathematical theories are all mere approximations of what’s really going on.

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24 responses to “Newton vs Einstein

  1. “Wrong” sounds so black and white. Can we say that Newton and Einstein are geniuses that clarified our view of the universe, paving the way for the next genius to go one step further up the ladder and make adjustments to the previous vision? Didn’t Newton say as much with his “standing on the shoulders of giants” analogy? Maybe also the mathematical view of the universe isn’t right or wrong but one instructive way of looking at it – a way of illuminating the objective aspect of lived reality from a particular orientation point (the mathematical). Kant, Jung, Blake, and the Dalai Lama might give alternative angles, equally illuminating, on what lived reality is all about. But, judging from Newtona and Einstein, physicists stand alone when it comes to “hair” as a tool for the advancement of fashion anarchy.

  2. All that is true, of course, but inclusiveness and fairness don’t drive science forward. Scientists must put their ideas out there, and wait for them to be shot down. Physicists in particular have a reputation for ruthlessness and precision. Newton, in fact, was a rude and inconsiderate bastard 🙂

  3. Perhaps, scientific theories should not be labeled as “right” or “wrong”, but rather judged by how useful they are to predict results. No instrument can provide a 100% accurate measurement and when you measure the same value multiple times with the best instrument in the world, your measurements will vary. Even if 100 measurements produce the same value, there is no guarantee that 101st measurement will be the same. In statistics, they talk about intervals, the probability of error, and the confidence level. Sometimes, being wrong in 10% cases is acceptable – all depends on the application.

    • You’re right that predicting results is the test of a scientific theory’s value. For example, Quantum Theory is mad and bad, but is accepted because of its ability to make predictions that match reality.

      Newton’s theories still enjoy enormous predictive value, as I discussed, and so do Einstein’s. But both fail when applied to the most extreme situations in the universe.

      However, the best scientific theories do more than simply predict – they explain why. For instance, heredity has been well understood since Darwin’s time, and the rules of heredity were discovered by Mendel in 1866. But it wasn’t until DNA was discovered that the mechanism of heredity was explained, and then it became clear why the rules were true.

      • Science doesn’t explain why. Science discovers rules “if A then B”. You might say that the rule explains that B exists “because” A exists. But science does not explain why the rule exists in the first place. It may discover that rule X exists because rule Y exists, but that’s just another rule.

        Also, the question why can have multiple meanings. It can be about cause or about purpose or intent. Certainly, science cannot say anything about intents and purposes.

        • Science is natural science, so it has nothing to say about intents and purposes. It does not attribute desires to inanimate objects in the way that many people seem to do. It is naturalistic.

          Does science seek to explain? I think that is its goal. It uncovers causes and effects and the rules that govern them. That is a better explanation than not understanding the causes, but it is not a full explanation. That is why science is an ongoing project.

  4. I knew Jonathan Swift (known to be cranky himself) had it out for Newton (something about the Irish and Newton’s role at the Mint), but et tu, Steve Morris? In any event, I hold fast to my “hair” comment. https://shakemyheadhollow.wordpress.com/2012/05/12/letter-from-a-fashion-anarchist/

  5. If we claim that Newton explained the world, then of course his explanation is wrong. But then so is every other explanation we know. There is no explanation of the world so far.

    The fact is, as you admit yourself, Newton’s description of how the world behaved was right enough for NASA to accomplish all it has (not to mention all the other places Newton’s laws apply). Typically a good test of whether something is right or wrong is to use it, and Newton’s laws have stood the test of time.

    Of course Einstein extended our understanding about how the world behaves into realms we don’t normally experience. But in the realms in which we do operate, Newton’s laws perfectly. I really don’t understand how you label laws that apply to a specific case “wrong.” Is special relativity “wrong”?

    To me, to say someone got it “wrong” requires they had some chance of getting it right. I don’t see that Newton had that chance, and considering the era he was pretty amazing. (When you assert, “most of them turned out to be wrong,” are you including his work in optics and calculus?)

  6. I am not trying to belittle anything Newton did. As I say, he’s my hero! His work stood the test of time, and explained every phenomenon known at the time.
    I am not trying to be combative, but to illustrate a fundamental difference between models of reality and reality itself. Ultimately I am interested in exploring whether the world really is mathematical, or if mathematics is simply a useful tool for making predictions about the world.
    Newton’s and Einstein’s theories are simplified models of how the world works. They are extremely useful and powerful models. But they are not complete explanations. The universe works in some different way that we don’t yet understand. That’s all I’m saying. You’re saying that too, so I think we agree in all but emphasis.
    When we do have a complete theory, it will agree to a high degree of accuracy with Einstein and Newton in the areas where those models are valid. But it will not match them precisely. There will always be discrepancies, however small.

    • I’m not sure whether you’re replying to me, someone else, or just in general, although you did use “you” in a way that makes me think this is a reply to my comment above.

      “His work stood the test of time, and explained every phenomenon known at the time.”

      I think a key disconnect comes from the word “explained.” As I said above, I think the better word is “described.” I’ve never viewed either scientist as having explained anything.

      You mentioned F=ma, for example. That formula doesn’t explain anything, but it does describe a relationship between force, mass, and acceleration. The domain of that description is restricted, but so is the domain of SR.

      “Newton’s and Einstein’s theories are simplified models of how the world works. They are extremely useful and powerful models. But they are not complete explanations.”

      The thing is, I don’t know that anyone, including those scientists themselves, have ever claimed either set of theories are explanations let alone complete ones.

      “The universe works in some different way that we don’t yet understand. That’s all I’m saying. You’re saying that too, so I think we agree in all but emphasis.”

      Well, yes, I think we do, except where you’re also boldly declaring that ‘Newton was wrong’ (and having Einstein trash him with a baseball bat). I definitely don’t see it that way. 😄

      (Put it this way: If Newton was “wrong” then what should NASA have been using all these years?)

      Just to be clear, I’m not offended or spitting nails that someone dared to call Newton “wrong” — I’m not invested in history to any extent, let alone that. And I know what you mean. (Do you understand what I mean when I say I see neither man as being “wrong”?)

      This all seems to come from the comment conversation you and I had previously where you asserted “Newton was wrong” and I objected and you objected to my objection and I supported my objection against your objection and here we are having at this point, I think, beat this horse to a sodden unrecognizable mess with vaguely horse-like chemistry!

      Thing is, my “point of order” was a little tongue-in-cheek over a passing comment. I knew what you meant and was only being cute objecting to the word “wrong.” It’s funny how things like that grow and become their own topic. Maybe I should have stuck a 🙂 at the end of that original comment.

      • Sorry, Wyrd, I was splitting hairs. That horse DNA is now totally pulped. Let me conclude by saying 🙂

        BY the way, you have impressed me with your use of bold and italics in comments. Is that done using HTML tags, or something else?

  7. Oh my god, did not expect the philosophical tangent you spoke of in the conclusion.

    Recognised Newton’s equation from junior college days, woohoo!

    Superb post!

  8. Do scientific theories reflect reality or are they merely useful? Most scientists are scientific realists, motivated to discover reality, not to find useful predictive instrumentalist frameworks. But it does help to periodically take off the realist hat and put on the instrumentalist one when trying to find hidden assumptions.

    On mathematics and reality, after reading something Graham Priest wrote about logic, that it’s essentially a theory about reality that we build other theories on top of, I’m starting to consider mathematics (quantitative logic) to be the same thing.

    But if they are theories, then we should be prepared to see them revised over time, a notion many will find intolerable.

    • After many years of thinking about this, I have come round to the same opinion. But I’m optimistic we will one day explain reality in all its details.

      • Unless Gödel’s and Turing’s discoveries about how some things can never be proved or decided turns out to apply to reality in general.

        Especially if reality does turn out to be mathematical, then it sure seems Gödel would apply.

        I do wonder sometimes if the goal of fully understanding reality doesn’t turn out to be as illusive — even impossible — as Hilbert’s similar hope regarding mathematics.

        • Yes, those are definitely warning signs! But if mathematics really is something that we created ourselves, perhaps we shouldn’t be too worried if it is incomplete or broken. Reality definitely seems to exist externally of us, so it doesn’t necessarily come with the same baggage. But I am also wondering if science will eventually run out before we reach the ultimate goal of explaining everything. For me, that would be more intellectually satisfying than the currently popular “it’s a multiverse, anything can happen” approach that pervades certain types of thinking in physics and cosmology.

          Excellent point though – not something I had previously considered, although seems obvious now that you mention it.

        • (Thanks.) I’m completely with you on not being a fan of multiverse theories! (Nor, for that matter, many-worlds theories.)

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