Avi Loeb | Department of Astronomy

Physics is stuck — and needs another Einstein to revolutionize it, physicist Avi Loeb says

Harvard professor Avi Loeb says the potential for a great mind to revolutionize physics is greater than ever

SEPTEMBER 6, 2020 11:30PM (UTC)

Albert Einstein's work so revolutionized physics that it is difficult to discuss him without slipping into hagiography. Indeed, his brilliance is so storied that his surname has become synonymous with "genius," and his brain preserved for study. 

And yet, while Einstein was undeniably a smart cookie, one cannot look back at the course of history without noticing that the dominoes were all there, set up, and waiting for someone like him to start toppling them. Part of Einstein's brilliance was merely realizing this. Avi Loeb, a professor of physics at Harvard University with a regular a column in Scientific American, told me that he thinks that Einstein's physics revelations would have been developed by others even if Einstein hadn't been born. "It would take maybe a few more decades," Loeb clarified. "Many of the things that Einstein personally was responsible for — there at least 10 touchstones in physics where each of them is a major intellectual achievement — you know, they would be discovered by different people, I think," Loeb continued. "illustrates his genius." 

Loeb is advising on a public project celebrating Einstein's life and work at Hebrew University, which hosts an archive of Einstein's documents. The project, "Einstein: Visualize the Impossible," is slated to be an interactive online exhibition to That the public with Einstein's work. As a fellow physicist, Einstein's work and his life have weighed on Loeb's mind for years, which is why he was interested in helping curate.

In considering Einstein's legacy, though, Loeb says we have to reckon with what has and hasn't changed about the physics world. In the 1890s, when Einstein was in college, physics knowledge was a shell of what it is today. Quantum mechanics, dark matter, nuclear physics and most fundamental particles were unknown, and astronomers knew little about the nature of the universe — or even that there were other galaxies outside our own. Nowadays, many of the biggest physics discoveries happen by virtue of some of the largest and most expensive scientific instruments ever built: gravitational wave observatories, say, or the Large Hadron Collider at CERN.

Given the landscape of physics today, could an Einstein-like physicist exist again — someone who, say, works in a patent office, quietly pondering the nature of space-time, yet whose revelations cause much of the field to be completely rethought? 

Loeb thought so. "There are some dark clouds in physics," Loeb told me. "People will tell you, 'we just need to figure out which particles makes the dark matter, it's just another particle. It has some weak interaction, and that's pretty much it.' But I think there is a very good chance that we are missing some very important ingredients that a brilliant person might recognize in the coming years." Loeb even said the potential for a revolutionary physics breakthrough today "is not smaller — it's actually bigger right now" than it was in Einstein's time. 

I spoke with Loeb via phone about Einstein's legacy, and how physics has become "stuck" on certain problems; as always, this interview has been condensed and edited for print. 

To start, let's talk about some of Einstein's contributions to science. What compelled you to help curate this celebration of Einstein's legacy?

Well, to start, Einstein's special theory of relativity revolutionized our notion of space and time. The fact that space and time are entities that are lumped together and that the speed of light is the ultimate speed, and, and that you can convert mass to energy, which is demonstrated by nuclear energy in particular. Then later on, he made the extremely important contributions to quantum mechanics, and of course developed the general theory of relativity that he published in November 1915, 105 years ago. And amazingly, exactly a hundred years later, in August, 2015, gravitational waves were detected by the LIGO experiment — and they demonstrated that not only do gravitational waves exist, which are ripples in space and time that Einstein's theory forecasted, but also that the forces of these gravitational waves are black holes, which are also a prediction of Einstein's theory.

Obviously Einstein was very visionary, but also in a sense, he had peers — people like Karl Schwarzchild and Edwin Hubble — who were doing work that would help him test and correlate his theories. I've wondered, say, if Einstein were born 30 years later, would someone else have figured out relativity, and the photoelectric effect, and so on? 

That's a good question. Physics is about nature, right? So we're trying to learn about nature. We're trying to understand nature and you know, so, in that sense, we collect data and eventually someone comes up with the right idea. The question is, how long does that take? What I'm saying is, I believe that the same ideas would have been developed. I don't know how close to the time that Einstein and thought about them, but eventually. . . . it would take maybe a few more decades or something. But the most important thing is, I think it would have been fragmented. So, you know, many of the things that Einstein personally was responsible for — like there at least 10 touchstones in physics where each of them is a major intellectual achievement — they would be discovered by different people. So the fact that he came up with with all of them illustrates his genius.

But you know, if you look at people that got the Nobel prize, there are many people — examples of people that got it once for one major discovery, that's pretty much what they did for their life. Either they did it early on in their life or late, but doesn't matter. And that's not true about Einstein. So he didn't only deviate from the beaten path and, and come up with original ideas, but he did it multiple times. And by that, you know, it contributed to humanity. A great deal, I should say, like for example, his a general theory of relativity — this idea that space and time and gravity are connected.

It seems like physics has changed between Einstein's day and now. Most of the underlying physical principles of our universe appear to have been well-defined and tested by now — say, the standard model of particle physics, or relativity and gravitation. And a lot of advances happen now because of data from huge teams working on government-funded instruments. Given the landscape of physics, is it actually possible that there could be somebody else like Einstein nowadays, someone who revolutionizes the whole field? Or do you think things have sort of fundamentally changed — both in terms of funding of experiments and of our understanding of the universe — so that such a thing is no longer possible? 

I mean, we do have much bigger experiments as you said, and much more data in some fields. But we still need people that think about the blueprint of physics, that think about the fundamental assumptions that everyone else is making that might be wrong. We need critical thinking. And there are some dark clouds on the horizon, just as they were 150 years ago. You know, back then, back then it was the blackbody radiation. And people at the time thought, "well, we just need to clarify that dark cloud, and then we finish physics." [Editor's note: in the 1890s, the fact that objects glowed different colors as they heated up was one of the great mysteries of physics. It turned out to be related to quantum mechanics, the study of which prompted an ongoing revolution in physics.]

And right now there are some dark clouds, too, you know. Like, there is the nature of dark matter, or the nature of the cosmological constant, or that we don't know where the vacuum gets its energy from. People will tell you, "oh, these are just minute details. You know, we just need to figure out which particles makes the dark matter, it's just another particle. It has some weak interaction, and that's pretty much it. And the dark energy, you know, it's just the vacuum energy density, you know, for some reason it's more maybe, because otherwise we wouldn't exist here." You know, we can give each other awards and celebrate the end of physics.

I think it's pretty much similar [to the 19th century situation]. And I think there, there is a very good chance that we are missing some very important ingredients that a brilliant person might recognize in the coming years, in the coming decades.

What are some of the "dark clouds" in physics, as you say? 

One of the challenges is unifying quantum mechanics and gravity. So you have this huge contingency of string theories that agree among themselves that they are leading the frontier, but nevertheless, they haven't provided any concrete predictions that can be tested by experiments over the past 40 years. [Editor's note: String theory unifies quantum mechanics and gravity, but it is, as Loeb mentions, not testable as far as anyone knows.]

[String theorists] are still advocating that they're the smartest physicists — although they're not doing physics, because in my book, physics is about testing your ideas against reality, with experiments. And, you know, I very much believe that put your theory to the guillotine of experimental data, and it may cut its head off. But if you don't risk your theory by testing it, you can be very proud of yourself. The only way that you maintain your humility is by recognizing that there is something superior to your ideas, which is nature. And it's a learning experience where you're not supposed to know everything in advance.

And that's unfortunately not popular these days. Today, it's all about impressing each other. And that's part of social media, you know, trying to impress other people to say things that look smart, that look very intelligent, that completely align with what everyone else is saying so that they will like you, that you would have more likes on Twitter. Okay. So that's the motivation, so that you can get more awards, more grants so that you can get a tenure appointment and everyone would respect you. 

That's wrong. That was clearly not the motivation of Einstein. He was not trying to be liked, and that's why he was working in a patent office. But his ideas happened to be right. And in a way he was naive in that sense, but that's the right approach — you should be always learning.

So I would say there is the same potential — even greater now — because we are at a time when we recognize the success of physics. It has a huge impact on the economy, on politics, and so forth. So we recognize that — but if you look at the frontiers of physics, which is blue sky research, you know, it's supposed to be open minded — but it's not open-minded. There are groups of people, entrenched in ideas that will never be tested and they believe that they're leading the frontier.

Right. So are you saying that the premise of the some of the major experiments might even be wrong? Like, all the prominent dark matter experiments are trying to find this weakly-interacting, supersymmetric particle, but even that assumption may be wrong?

So here is an example: Supersymmetry, you know, that was an idea advocated for decades now. [Editor's note: Supersymmetry is the theory that for every fundamental particle, there is a "partner" particle; so for the electron, there would be a supersymmetric "selectron," and for the top quark, there would be a supersymmetric "squark," and so on. Dark matter is theorized to be made of one of these particles. Yet none of the supersymmetric particles have ever been observed.] And people celebrated this idea, and gave each other awards. The Large Hadron Collider in CERN was supposed to detect the lightest supersymmetric particles — and it didn't. There's no evidence for supersymmetry.

So obviously what people say is, "oh, maybe it's around the corner." But it's already ruled out — the most natural versions of supersymmetry are ruled out. So here's an idea that was celebrated as part of the mainstream — not only celebrated, but it was the foundation for string theory. So they put it as a building block: "We know it exists, put it as a brick at the bottom of the tower that we are building called string theory, called superstring theory. And let's assume that we know it it's completely trivial, experimentalists will eventually find it, we don't even need to think about it — let's put it as a building block of our tower."

Doesn't exist. LHD [Large Hadron Collider] didn't find it. So then, people say, "okay, weakly interacting massive particles are dark matter — but for decades, they haven't found anything. [Editor's note: One prominent theory to explain dark matter is that it consists of particles that are heavy but rarely interact with normal matter, though they bounce off of themselves and have a gravitational interaction. Most of the major experiments searching for dark matter are attempting to find this type of weakly interacting massive particle, or WIMP for short.]

And so I asked the experimentalists, "how long will you continue to search for WIMPs, these weakly interacting particles, since the limits are orders of magnitude below the expectation?" And he said, "I will continue to search for WIMPs as long as I get funding."

So in the mainstream approach, there is this stubbornness — like, we stick to the ideas that we believe in. And then anyone that deviates from that will be sidelined. You know, anyone that considers any other theory for unifying quantum mechanics and gravity through string theory is sidelined, even though there is no reasonable evidence for string theory. So I would say the potential now for a breakthrough that will be really revolutionary is not smaller — it's actually bigger right now [than it was in Einstein's]. It's just, the social pressure is stronger.

So we do need — we desperately need another Einstein. There is no doubt.


Keith A. Spencer is a senior editor for Salon. He manages Salon's science, tech, economy and health coverage. His book, "A People's History of Silicon Valley: How the Tech Industry Exploits Workers, Erodes Privacy and Undermines Democracy," was released in 2018. Follow him on Twitter at @keithspencer, or on Facebook here.