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Why do physicists seek to study and explain more fundamental qualities of matter as opposed to stopping at a certain point and testing more predictions of macro-level models? What benefit does the "first-principles-thinking" have? Is there a tradeoff? Or is it a trend based on historical value?

I apologize if this question sounds a bit simplistic. What motivated me to ask this question is looking at the relationship between this quality and the other sciences.

  • I don’t understand. Could you explain more? If it makes sense to phrase it that way do you mind modifying my question? – Jonesn11 May 16 '18 at 1:58
  • Scientific reductionism is the mainstream approach of physics because of its success. – Nick May 16 '18 at 2:16
  • Because every theory has some "limitations" : inconsistencies, facts that are impossible/difficult to explain, and so on. – Mauro ALLEGRANZA May 16 '18 at 7:00
  • Because people have inner desire for knowledge. And knowledge in this case means how the world is arranged. And it is unclear how do these forces work altogether. Therefore, knowledge is Theory of Everything (and, well, if someone discover new force, it won't be ToE anymore, but still more powerful model). – rus9384 May 16 '18 at 9:00
  • Similar to physics.stackexchange.com/questions/406169 ??? – John Forkosh May 16 '18 at 11:24
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You have to realize that the physicists running around in laboratories is only the absolute tip of the iceberg of a far larger social system. They don't spend more time testing predictions on macroscopic systems because they already have a group that does that: industry. For example, the steel industry tests theories about crystallization in metals thousands of times a day. Civil engineers test material strain theories in every structure that is built. Scientists do have to eat, and nobody is going to pay them find ways to test things when the industry can test them in ways that pay for themselves.

Scientists are always pushing the limits of what is known. You don't get much credit for demonstrating what is already known. You get credit for stretching the boundaries. In particle physics, much of the effort is to explore higher and higher energy systems. When we increase the energy, they don't always behave in obvious ways, so there's something to be explored. As it happens, this currently lends itself to studying fundamental aspects of matter, such as subatomic particles.

  • I don't understand your distinction between physics and engineering. "Industry" doesn't only deal with low-energy "macroscopic systems", and physicists don't only deal with high energy microscopic systems. – Geremia May 20 '18 at 4:57
  • @Geremia I specifically targeted particle physics because that seemed to be where the OP was coming from. In other domains in physics, the boundaries are elsewhere, but the pattern of having to stretch the boundaries still holds true. And the difference between physics and engineering is that physics pushes the bounds of what is known, while engineering seeks to build products affordably using the information we learned from the scientists. – Cort Ammon - Reinstate Monica May 20 '18 at 6:09
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Because modern physics is dominated by atomism.*

Pierre Duhem's Energetics program,** which promoted a generalized thermodynamics from whose first-principles all physics sub-fields should derive, criticized the "Cartesian method" of unnecessarily bringing metaphysical constructs like atoms into physical theories.

See his

Regarding the first principles of physical bodies, see

  • Cosmology by Édouard Hugon, O.P., pp. 140-144, and his
  • refutation of atomism, pp. 145-155.


*a concise refutation of atomism:
introducing a least quantity, he [Democritus/atomists] overthrew the most important propositions of mathematics — for example, that any given line can be cut into two halves.
—St. Thomas Aquinas, In De caelo lib. 1 l. 9 n. 4 [97.], quoted in this answer to "Interpretation of the butterfly effect"

**cf. Rankine's Outlines of the Science of Energetics

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The incentive for an individual scientist is to (1) do research that is deemed worthy and will be supported by institutions or grants, but also (2) make meaningful contributions to the field of knowledge. Lots of physicists work with macro-level systems, but scientists will naturally distribute themselves across the whole potential set of problems for which solving would grant professional acclaim. There was a time, about a hundred years ago, when physicists didn't have formal explanations for subatomic systems. Once those were described rigorously, it opened up a new field of research, and the pioneers who opened those doors are today some of the most highly regarded thinkers of all human history.

So to answer the question, all scientists do stop at some point (really, scientists are human), either because of social or professional pressure, they lose interest, retire, etc. Some might go work for industry, some might go teach high school chemistry. A few continue to question first principles beyond even what their teachers taught them to question, and very, very rarely (yet ultimately inevitably), that kind of questioning leads to a whole new way of thinking about the world.

Part of it is a gamble, how much do you value your sanity, how much are you willing to risk professionally, how much do you want to make an impact, how much are you willing to sacrifice for no guarantee at success? This is life, everyone has a different approach but how you choose to play is a reflection of who you are.

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Finding more-and-more fundamental parts of matter, as with SLAC, ALS, NIF, CERN, etc. provides insight into matter that only exists above a certain energy density. A bigger machine will reveal higher energy-density matter.

The Big Bang's energy density is theoretically infinitely high, so physicists can be sure that a higher energy density machine will tell them new stuff about reality, that has never been known before.

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It's in the idea of 'reductionism'. A kind of principle that says that we should look to explain the physical world in terms of more simple and fundamental parts. The reason this idea seem attractive to physicists, I think, is a combination of how 'successful' it's been in the past (however you want to define success in the sciences) and how intuitive it is.

It's been successful in that, ever since Newton, we have moved on to try and explain more complex systems such as gasses and the dynamics of energy (thermodynamics) and those physicists who were able to develop the most predictively viable theories were those who considered the system as the sum of some smaller constituent parts. The first of its kind was probably kinetic theory. It just worked. We were able to explain behaviour on a macroscopic scale as the sum of smaller parts which, later down the line, we were then able to undeniably detect through the invention of more powerful cameras since, previously, we could only judge the existence of these objects through the power of their ability to predict what would happen in gas systems and things like that. And science is really in the business of aiming to explain things about the natural world in terms of models that are helpful for this purpose. Perhaps the hardest phenomena to understand in terms of the sum of some smaller parts today is consciousness but some scientists argue that it emerges in just the same way that other very complex phenomena do. It's just so complex that we can't really understand it yet.

Ever since we have moved on to the much more (extremely more) successful enterprise of quantum and particle physics since Einstein aimed to describe the macroscopic behaviour of 'brownian motion' (the random motion of pollen in water) and the 'photoelectric effect' (how electrons would be emitted from the surface of a metal plate when light is shining on it) in terms of the atoms of water and 'photons' of light. Also how the Rutherford experiment was able to explain the macroscopic behaviour of materials by positing that the atoms within these materials had a certain structure where physicists thought that atoms were more like 'hard balls'. I.e. indivisible hard balls which simply exist and undergo 'hard ball' interaction. Which just means that they bounce off of one another and transfer energy/momentum to one another without loss of energy due to deformation. It's a good approximation of what we now thing actually happens. Imagine atoms like billiard balls. That's usually the analogy which is used.

Also, I say it's intuitive because ever since ancient Greece we have had 'atomists'. Philosophers that posited some most fundamental building block of nature which could explain everything. It's intuitive because it's simple. And because in life generally, perhaps we have an affinity to studying the parts of something to understand its whole.

You can find this idea online that reductionism is completely opposed to emergentism. They're not completely dissimilar. Sean Carroll (read his books they're very good) likes to discuss how 'higher level' and more complex phenomena can emerge in a non-obvious way from smaller parts. I.e. how atoms emerge from fundamental particles, how cells emerge from atoms, how orgaisms emerge from cells, how intelligence emerges from organisms, how communities emerge from intelligence etc... Ockham's razor is a powerful thing.

Edit: Oh also, I forgot to mention. Trying to understand systems that are very complex at large scales (the opposite to a reductionist method) becomes difficult because of the practicality of computation. I.e. what do you compute and how. Massive approximations are made in order to receive a model that looks anything like the complex at large and makes our understanding much less specific and more general.

Perhaps it's more intuitive to understand how one of the most fundamental parts works in its own and in the presence of other fundamental parts and then extrapolate outwards to have the most detailed understanding possible.

Like I said, science is in the business of creating theoretical frameworks that explain things. Describing a complex whole is useful but I'm not sure how you could consider it explanatory. For something to be explanatory, it seems like to have to extrapolate to new knowledge. In most cases, knowledge of something you can't see because it's so small.

I direct you here for more information:

http://www.preposterousuniverse.com/blog/2011/04/21/avignon-day-3-reductionism/

This is Sean Carroll's blog and there are many more articles on here about the debate between reductionism and anti-reductionism.

  • Why do you (it seems) equate atomism with reductionism? – Geremia May 19 '18 at 5:51
  • Because atomism was an attempt to explain higher level phenomena in terms of more fundamental, microscopic constituents. – Joe Lee-Doktor May 20 '18 at 10:03

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