British physicist and science popularizer Phil Halper emailed me about two new surveys he and others had conducted with 1675 physicists, asking their views about fundamental questions in the field. This is not, of course, a guide to the truth, but simply a snapshot of where physicists stand on things like quantum gravity, black holes, and the Big Bang. The links to the surveys are in the text below, sent by Phil. I’ll highlight a few of their stands on interesting (to me) issues. Phil’s words are indented:
My co-authors and I just released the largest survey of physicists ever done. In conjunction with the American Physical Society we got more than 1600 replies to our Big Mysteries Survey.
What’s relevant for debates between believers and non believers is that we only got a large consensus on one topic and that is the Big Bang should be understood only as a theory that says the universe evolved from a hot dense state that says nothing at all about a beginning of time . Interestingly, we got 68% in both this large survey of a broad cross section of physicists and for a smaller scale survey we did of leading physicists in Copenhagen with the Niels Bohr Institute. This seriously undermines William Lane Craig’s Kalam cosmological argument which is defended by claiming that physicists agree that the Big Bang has shown that the universe had a beginning, we now have strong empirical evidence that physicists think no such thing.
On the fine tuning argument the most popular answer was that constants are brute facts that need no explanation. This was found in both of our survey and in the Phil papers survey of philosophers.
You can see the results here
And the Copenhagen Survey is here.
JAC: The Copenhagen Survey involved views of 151 physicists attending a conference on black holes in 2024.
And there is a video with Sean Caroll, Niayesh Afshordi, and Ghazal Geshnizjani discussing the results here. [JAC: I’ve put the video below.]
You might also enjoy the recent debate I did on science, cosmology and faith with Stephen Meyer here.
I haven’t yet watched the videos, but I did look at the big survey; you can access the pdf for free by clicking on the screenshot below:
First, a bit of methodology from the paper:
In the summer of 2024, a survey was conducted at the Black Hole Inside Out Conference in Copenhagen to assess physicists’ views on a range of ongoing controversies [1]. Eighty-five scientists responded. One year later, the authors collaborated with the American Physical Society’s Physics Magazine on a substantially larger follow-up survey, which polled 1,675 participants from the magazine’s readership and the members of the American Physical Society. The Physics Magazine survey therefore provides a broader view of attitudes within the physics community and allows comparisons with the more focused conference-based Copenhagen sample.
Taken together, the two surveys make it possible to compare views expressed in a specialist conference setting with those expressed by a much larger and more heterogeneous respondent pool. On some topics, the results are remarkably similar; on others, the differences are substantial. This paper presents the Big Mysteries Survey results, offers commentary on their interpretation, and highlights points of agreement and divergence relative to the Copenhagen survey
Here are a few bar charts from the paper. First, what the Big Bang implies (Sean Carroll explains this at the beginning of the video below). A big majority of physicists think that the Big Bang says nothing about whether it marked the ‘beginning of time”:
Of course tyros like me have no idea why the Big Bang doesn’t imply the beginning of time, but so be it: all of this is above my pay grade but I’m happy to see where physicists stand on these issues now.
What about cosmic inflation? A bit more than half of physicists think that cosmic inflation (the expanding universe) explains “an unexpected uniformity” of the universe.
Dark matter: does it explain anomalies in the rate of rotation of galaxies? No consensus:
Also no consensus on whether dark energy explains the accelerating expansion of the Universe:
There’s no consensus on why the universe’s physical constants appear to be “fine-tuned” for the existence of worlds that can produce life. (This is a favorite theological argument for God.) The “brute facts” explanation brings a stop to searching for explanations, but only 26% of physicists hold it. 20%—and I think this includes Carroll—think it’s explained by a multiverse.
There are more graphs, but I’ll show just one more. What kind of picture of the Universe is provided by quantum mechanics? The Copenhagen explanatoin, which people like me can’t reconcile with physical reality, is the favored explanation. I believe it was Feynman who said that if you think you understand quantum mechanics, you don’t. I’m still baffled by the issue of quantum entanglement, and don’t even understand the experiments buttressing it.
And here’s the video with Sean Caroll, Niayesh Afshordi, and Ghazal Geshnizjani. Carroll, as usual, gives some very succinct and lucid explanations. The other physicists are good as well.
Have a look at the paper for more opinions, including about what black holes mean and what they do.
Interesting that 9% believe in an intelligent designer.
Superb overview of thought in physics.
This title comes to mind :
The Meaning of it All : Thoughts of a Citizen Scientist
Richard Feynman
1998
Addison-Wesley
Some great quotes in there – e.g. I think this one might fit the theme of this posting :
“It is surprising that people do not believe that there is imagination in science. It is a very interesting kind of imagination, unlike that of the artist. The great difficulty is in trying to imagine something that you have never seen, that is consistent in every detail with what has already been seen, and that is different from what has been thought of; furthermore, it must be definite and not a vague proposition. That is indeed difficult.”
(I have not 100.0% confirmed this quote or page number – waiting for a copy from the library)
Ok, but I think that at the surveys were designed to result in less consensus on some pretty basic points bc it parsed them into smaller versions.
For example, the low scores about the very existence of dark matter is compromised bc it is broken into different versions of what dark matter might be. Why not just straight up ask if you think that dark matter explains the rotation of galaxies, and the cosmic web, and the strong bending of light from distant galaxies? I am surprised that the existence of dark matter is highly doubted, even so.
Also, if they simply asked if there was dark energy, we’d get 50% agreement. But here it is split by different forms of dark energy. Still, I am surprised about it being supported by 50% at best.
About dark matter you will find some reason that explains why it is highly doubted here
https://tritonstation.com/
Best.
Very interesting. I find dark matter particularly interesting, in that so much depends on this as yet unobserved and mysterious stuff—if it’s stuff at all. It seems to me that dark matter is an ad hoc construction uniquely invented to make the gravitational math work out. Ad hoc though it may be, it may also be true. Let’s find some and put it in a box!
And quantum mechanics. When I was taking p-chem in college, I made the mistake of asking what it all means. My professor told me that chemists don’t worry about meaning. All that matters is that the math comes out correctly and that the wave equation works. Many chemists of course do worry about meaning, but mine was one of those whose approach was apparently to “Shut up and calculate!”*
*quote attributed to physicist David Mermin
It’s because the Big Bang model says nothing about whether that was the start of everything, or whether the Big Bang arose out of a pre-existing state.
The scenario most in line with what we currently know about physics is that the Big Bang arose as a quantum-gravity fluctuation in a pre-existing state.
Just a quibble. “Cosmic inflation” does not refer to the general expansion of the universe as observed today. It’s a specific proposal that, very early on in the Big Bang (about 10^-33 secs to about 10^-30 secs), the universe went into an “inflationary” state, very unlike the state of the universe today, causing the proto-universe to expand by a huge factor of about 10^30. This is postulated to explain several facts about the universe as we observe it today that would be puzzling otherwise.
Note that it’s a survey of Americans and Americans are quite religious (by developed-world standards).
Not a physicist or cosmologist here, but I can’t resist having opinions on these matters. The Eternal Inflation Model has long seemed to me to be the best model for the cause of the Big Bang. I am not sure how well this is accepted, though, and I don’t see it named in the above surveys. I find this puzzling since it is not an obscure model.
Anyway, with this model in mind, I don’t then see why our Big Bang has to be the beginning of space and time itself. Asserting that it was the beginning of space and time is a bit like asserting that there was no such thing before you were born.
You are right that Eternal Inflation is a favoured model (indeed it’s pretty hard to have inflation that doesn’t give the eternal-inflation outcome), though note that this implies that the universe is future-eternal but not necessarily past-eternal (in principle one could have the eternal-inflation scenario with a starting point). For that reason this would come under the third option in the above question about time, which is why it is not listed separately.
Thank you for providing these insights, Coel. They helped much in increasing my understanding of the material in the post.
I very much enjoy reading these scientific-type posts, even though (or maybe, because) they challenge my comprehensive abilities.
The ‘brute facts’ explanation for fine-tuning makes me want to pull my hair out. It’s the equivalent of denying that there is any question that needs answering. Huh???
I suspect some physicists resort to “brute facts” as way of shutting up the ID people. If so, I wish they wouldn’t. These two things can be true at the same time: There are some things we can’t explain, and God is never the explanation.
Oh, and btw, the correct explanation for fine tuning IS the multi-verse (in some form).
There’s a joke that a cosmologist died and went to Heaven. First thing he does he asks God why the fundamental constants are the values they are. God hands him a sheaf of dog-eared, coffee-stained papers covered with mathematical formulas and marginal notes. “Here. Read this. It’s all in here.”
The cosmologist avidly digs into the papers and after a few minutes he grabs God’s elbow and exclaims, “Hey! Page 56! You made a mistake here!”
(My recollection is that the joke was specifically about the permittivity of free space — don’t ask me why I remember that — and the scientist was somebody who had made contributions to working it out. But it was many years ago and the trail has gone dead.)
I vaguely recall a version of the joke in which God explains away the mistake by saying, “I wasn’t very careful because I was pretty sure humans would invent the multi-universe to explain it all away.” Or something like that.
HAHA! Excellent Leslie.
I file this under “stuff way above my pay grade.”
best,
D.A.
NYC 🗽
ISTM that “just the brute facts ma’am” is not only incurious but plays right into the claws of the ID-ers. Who, after all, is considered the greatest ever maker of brute facts just because he decided to? (Hint: not iDJT, even though he aspires to the role).
The choice offered by the poll is “Explained by anthropic selection in a multiverse” (20%). I fully agree with anthropic selection (WAP, the Weak Anthropic Principle): if this universe were not appropriately tuned for us then we wouldn’t be here to notice that. This is cosmic-scale sampling bias¹. So far, so good.
Where I strongly disagree has not found favour with the small number of actual physicists I’ve tried to discuss this with: the multiverse is sufficient for the WAP to apply, but it is not necessary; it is a needless rhetorical add-on.
Hypothetically, suppose that this one universe is all there is, and that its tuning is arbitrary (like each of the many differently-tuned universes in a multiverse). That implies that we were extraordinarily unreasonably lucky that it has the particular fine tuning it does. It is, essentially, a miracle that we’re here.
So bloody what? Almost all species we know of are extinct. Many orders of magnitude more never lasted long enough to even leave a trace of their former existence for us to notice. It is very exceptional that we have survived long enough to notice that we’re here.
Please draw the logical conclusion for yourselves.
(Logical, but not comfortable. In my very limited sampling, most people think they have a much better chance of winning a prize draw of 100 tickets than winning a bet that a particular 2-digit number they choose comes up randomly on a 100-slot wheel-of-fortune. ISTM that the only salient difference it that it feels safer if someone has to win; if no-one wins then they surely don’t, but if someone has to win then it could be them².)
…………
¹ One of my hobby horses. Some people (certainly no more than 90%) do not share my enthusiasm for the topic.
² I may get a chance to actually do this experiment with a class of 25 or so high school seniors. Stay tuned.
As for the question of the correct interpretation of quantum mechanics in the Big Mysteries Survey (p. 14), the “Copenhagen Interpretation” is the winner with 36%.
Here’s what Tim Maudlin (a distinguished philosopher of physics) thinks about it:
“By far the most controversial aspect of this book is not what it contains but what it omits. There is detailed discussion of the Ghirardi-Rimini-Weber spontaneous collapse theory, of the pilot wave theory of the Louis DeBroglie and David Bohm, and of Hugh Everett’s Many Worlds theory. But there is no discussion—indeed aside from here no mention—of the most famous “interpretation” of quantum theory of all: the Copenhagen Interpretation ascribed to Niels Bohr and his colleagues. Why is that?
A physical theory should clearly and forthrightly address two fundamental questions: what there is, and what it does. The answer to the first question is provided by the ontology of the theory, and the answer to the second by its dynamics. The ontology should have a sharp mathematical description, and the dynamics should be implemented by precise equations describing how the ontology will, or might, evolve. All three of the theories we will examine meet these demands.
The Copenhagen Interpretation, in contrast, does not. There is little agreement about just what this approach to quantum theory postulates to actually exist or how the dynamics can be unambiguously formulated. Nowadays, the term is often used as shorthand for a general instrumentalism that treats the mathematical apparatus of the theory as merely a predictive device, uncommitted to any ontology or dynamics at all. That predictive device is described in Chapter 2 under the moniker “the quantum recipe.” Sometimes, accepting the Copenhagen Interpretation is understood as the decision simply to use the quantum recipe without further question: Shut up and calculate. Such an attitude rejects the aspiration to provide a physical theory, as defined above, at all. Hence it is not even in the running for a description of the physical world and what it does. More specific criticisms could be raised against this legacy of Bohr, but our time is better spent presenting what is clear than decrying what is obscure.”
(Maudlin, Tim. Philosophy of Physics: Quantum Theory. Princeton, NJ: Princeton University Press, 2019. pp. x-xi)
Things get fuzzy when you get down to infinitesimally tiny scales. The observer vs. observed distinction appears to break down, perhaps revealing a fundamental unity.
Fine tuning has an obvious simple possible explanation.
With our present understanding of physics we can’t calculate these fundamental constants. Many fundamental problems exist which we don’t understand. For example, the natures of dark energy and dark matter, as well as an understanding of quantum mechanics, and how it works with general relativity. With deeper understanding, and better theories, calculations might show that the fundamental constants are required to take the observed values.
Physicists are generally more careful about degrees of knowledge and certainty when talking to each other than when writing for the laity. Good expositions of physics written for lay people such as Steven Hawking’s “A Brief History of Time”, or anything by Steven Weinberg are carefully written and contain plenty of caveats. But other popular writings on physics are less careful about this.
I am an off-and-on barfly and occasionally meet people who have read popular accounts of physics in bars. They often think that physicists have proved for certain that the universe started from a primordial singularity and that there are singularities at the center of black holes, and that the existence of dark matter is a certain thing even if its nature is unknown, and many other such things.
They are often disappointed when I explain that such things are not known. A singularity is a mathematical gadget. If we extrapolate the mathematics of general relativity to the center of a black hole, we get a singularity. But nobody knows what, if anything, a mathematical singularity might actually correspond to in physical reality (whatever that is). Maybe there is no singularity. Maybe the math simply becomes wrong when you get to close to the center of a black hole. Who knows? I’ve always liked a saying of the physicist/cosmologist Ralph Alpher: “Our best mathematical understanding of physical reality resembles reality only as much as a good map of London resembles the city of London.”
Regarding QM: For what it’s worth, I am somewhat partial to Carl Rovelli’s interpretation that goes by the name of “relational quantum mechanics”. Wikipedia has a decent page with that title.
The vastness is ineffable and that adds to the beauty. We are like mayflies that blink into existance, perhaps grasp (or perhaps not) the insane bigness of it all, but then are gone with whatever we grasped or wanted to grasp, or didn’t grasp a thing, but, ouch. Dead end, indeed. Does the Multiverse await? I liked the splash bang new(ish) movie Project Hail Mary and smirked when the head of the project was asked: Do you believe in God? and she answers: better than the alternative. What? some kind of Pascal’s wager? Oh man, it didn’t ruin it for me since she kareoked that killer Styles tune, but c’mon! That was some wishy washy faitheist bs you ask me. Burning in eternal hell fire is never a good alternative.