Modeling the Universe

A Very Brief Note by Kip Hansen — 13 September 2023

If one reads widely and freely enough, not paying attention to the norms of one’s interest-boundaries, one can find oneself surprised and charmed by some unexpectedly found gem of wisdom.

I only vaguely follow the hubristic attempts of cosmologists and advanced theoretical physicists to “model” the universe.  My reasons are my own – but deeply held.

Nonetheless, I stumbled on a priceless bit that interested me in an article by Dennis Overbye in the Science section of the New York Times titled: “Don’t Expect a ‘Theory of Everything’ to Explain It All”.   

Overby recounts:

“That was the question that occurred to me on reading an article in The Guardian by Andrew Pontzen, a cosmologist at University College London who spends his days running computer simulations of black holes, stars, galaxies and the birth and growth of the universe. His point was that he and the rest of us are bound to fail.

“Even if we imagine that humanity will ultimately discover a ‘theory of everything’ covering all individual particles and forces, that theory’s explanatory value for the universe as a whole is likely to be marginal,” Dr. Pontzen wrote.”

Personally, I don’t expect any theory-of-everything coming out of cosmology or advanced physics to explain much at all.  Science rules out far too much of the possible, starting with all religious/spiritual topics, denying them any consideration whatsoever.  Even when physics stays within its artificial boundaries, it has to admit, according to NASA,  that it only understands the 5% of the universe it can see and detect.  

Pontzen puts it this way:

“In cosmology, a plausible explanation of the history of the universe has formed by making simple assumptions about stuff we know nothing about — dark matter and dark energy — but that nonetheless makes up 95 percent of the universe. Supposedly this “dark side” of the universe interacts with the 5 percent of known stuff — atoms — solely through gravity.”

Pontzen has a book:  “The Universe in a Box: Simulations and the Quest to Code the Cosmos” which may interest some of you.  I haven’t read it  and don’t plan to. 

Pontzen does say interesting things: “….by way of the so-called butterfly effect of chaos theory. …. in practice, we cannot predict either the future or the past.”  He is referring to the past and future of the larger playing field, the physical universe, but I believe that his statement is correct in smaller arenas, such as Earth’s climate.

Overby goes on, giving the bit of wisdom that caught my eye and made my day:

“Dr. Pontzen quotes an oath suggested by Emanuel Derman, a particle physicist who became a quantitative analyst for Goldman Sachs and is now a professor at Columbia: “I will not give the people who use my models false comfort about their accuracy. I will make the assumptions and oversights explicit to all who use them.”

In his email, Dr. Pontzen added: “This is, I suggest, sometimes a good maxim for physics, too, especially in domains as complex as cosmological simulations.”

And to this I add my voice:  Derman’s Oath should be adhered to in all fields of science – whenever and wherever mathematical models are used in any research or study in any way whatever:

Bottom Line:

For all models used in any scientific endeavor, Assumptions and Oversights must be made explicit by model developers to all who use the model. 

As a corollary, I would add that no model should ever be used by persons who do not fully understand the assumptions, oversights and limitations of the model.

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Author’s Comment:

Well, this is a Pretty Brief Note…read the linked references for the full impact.

But Pontzen and Derman get right to the nut of the Models Problem.  Models are often wildly inadequate for purpose: full of unfounded assumptions, contain untold numbers of oversight (things left out) resulting in limitations that are never admitted. 

And as William Briggs is wont to preach:  Models Only Say What They’re Told to Say.

Thanks for reading.

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