Adam Brown is a theoretical physicist at Stanford, interested in early universe cosmology, inflation, black holes, and assorted other topics. His academic papers can be found on the arXiv.
In this episode of the Existential Hope podcast, renowned theoretical physicist Adam Brown shares his insights on the future of physics and cosmology. From his work on black holes and the early universe to his thoughts on the potential risks and opportunities for the future.
Full transcript, list of resources, and art piece: Adam Brown | A Theoretical Physicist's Take on the Future (existentialhope.com)
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The transcript below follows a question and answer format, showcasing an X-hope podcast episode. The podcast aims to shed light on what guests are focusing on currently in terms of discovery, what motivated guests to reach where they are now, what hopes or risks they envision for the future ahead, and what advice they may have for viewers. Moderators Allison Duettmann and Beatrice Erkers of the Foresight Institute spend some time talking with fellow guest Adam Brown. Adam Brown, who is a theoretical physicist specializing in an array of topics, including early universe cosmology and black holes, shares his ideas.
Allison Duettmann: Hello everyone and welcome to the Existential Hope Podcast. It is very nice to see some of our viewers physically backstage with us! To give you all a bit of a reminder, this podcast is not like our usual, technical seminars. Instead, here we aim to look out to the future of what is possible and hopefully inspire people to pursue a career in these fields or simply learn a bit of what the future potentially has in store. We are very pleased to be joined by Adam Brown for today’s episode.
Adam is a theoretical physicist at Stanford who is interested in early universe cosmology, inflation, black holes, and other assorted topics. I hope we can dive a bit into these fields throughout the hour. You also wrote a wonderful article for the Scientific American regarding mining black holes and more. At Foresight we are often known for having a long term view, which your views seem to align with as well. Overall, I am eager to discuss these topics with you, but let us start at the beginning to bring people up to speed. Could you describe in your own words perhaps what it is you are working on? What got you started? What could other folks make of your trajectory and what are you currently focused on?
Adam Brown: Thank you, Allison. I am a theoretical physicist interested in fundamental physics, such as quantum mechanics and gravity, which touches upon a number of other topics like cosmology, Big Bang, distant future of the universe, quantum computing, geometry of high dimensional spaces, and various other things in that dimension. One great thing about being a theoretical physicist is that I am like an experimental physicist. I don’t have lab equipment that needs to be reconfigured, I can just reconfigure my brain, work on a number of topics, and be light on my feet. These are the kinds of topics I get to think about. Also, I sort of had a relatively uncomplicated arc getting here as I was always a bookish boy growing up in Oxford. I went to the local university to read philosophy and physics, and then I moved to America for graduate school. Since then, I have gone to various academic institutions doing theoretical physics.
Allison Duettmann: Wow, I had no idea that you grew up in Oxford.
Adam Brown: I did, yes!
Allison Duettmann: Wonderful, that is an interesting and relatively straightforward trajectory. Perhaps you could bring people a little bit up to speed on what it is you are currently working on. If someone you know was entering the space of physics, and potentially even cosmology, what is the map of the field like so far?
Adam Brown: So in modern theoretical physics, many fields of thought are coming together. In the cosmology point of view, the history of the field has been pushing our understanding, well both backwards in time and forwards in time. From the backwards in time point of view, we are learning more sort of closer towards the Big Bang, or the singularity that happened in our past. First, people understood back to 300,000 years after the Big Bang, which was an important event because it is when the universe went from being opaque to translucent. Then, they understood to sort of three minutes, which is when the elements were made and people just kind of keep pushing those ideas back and back. So one can, like a historian, characterize oneself with a timescale. In the very early universe, we now basically understand back to sub second timescales after the notional Big Bang.
Additionally, in order to understand those timescales, we must understand how to combine these two great theories of 20th century physics. The first is that of gravity which was extremely operative at the Big Bang and it was described by Einstein's general relativity. Secondly, we must understand quantum mechanics, which is the theory that most pertains at the smallest scales as the universe in those days was absolutely miniscule. So that was the time where gravity and quantum mechanics were operative. We are now faced with many questions that are purely theoretical about how to combine these topics, or only involve thought experiments about black holes. In terms of cosmology that is where we are at, as well as various topics.
Allison Duettmann: Can you share a bit more about the singularity that apparently occurred within our past?
Adam Brown: Yes, this was one of the surprising discoveries. It is sort of a natural consequence of Einstein’s theory of gravity, general relativity, which is one that he missed. He sort of did not like it from a philosophical point of view, so he rejected it. Nevertheless, the theory seems to be correct. It states that if you look out into the universe today, all of the galaxies are moving away from us, except for very close ones. The further away they are, the faster they are moving away from us. If you play the tape backwards for 18 billion years, it looks as though the galaxies are in the same place, which is the Big Bang. That is compelling theoretical evidence with Hubble and many people starting in the beginning of the last century. A big project in cosmology is simply to understand physics as you get closer to the Big Bang with everything getting hotter, more quantum mechanical, and all of these other things. Trying to understand that becomes harder the closer you get to the Big Bang. That is one of the big projects.
There was a great experiment about the W map, as well as a few others. They sent satellites up and looked at the imprint of the Big Bang, called the cosmic microwave background. In any direction you look in space you see a faint buzz that is a few degrees Kelvin. By reading the patterns in that buzz, we have learned a fantastic amount that did not seem possible when people first wrote down these theories. For instance, years ago these writings included caveats, such as “Of course, we will never actually see this.” Yet, here we are seeing it. We have built cryogenic satellites to look at it and we have now seen these echoes of the Big Bang in which we can infer a huge amount of information regarding what was going on in those early moments.
Allison Duettmann: Wonderful. You already referenced Einstein in there, but have there been new fields or significant culture shifts in terms of what theories have become okay to believe? Or even in terms of conceptual things that could turn physics or cosmology upside down? Have there been any notable historic events where we have had to scrap everything we believed at that point in time and kick start something new?
Adam Brown: There have been shifts in the way physics is done, involving information technology. The internet revolutionized the mechanics of doing physics. Physicists were early adopters and inventors of internet repositories, which kind of revolutionized the mechanics of spreading ideas within physics. That has been a big cultural shift. Now, in terms of a big discovery, one of the biggest for cosmology was in 1997. The discovery was that of the cosmological constant, and while compatible with Einstein’s theories, it was also initially rejected. It was somewhat astonishing that the cosmological constant was there, because if you read papers from the 70’s with people writing about the long term future of the universe, they came to assume ways of the past that are now irrelevant with the finding of the positive cosmological constant. It was a big discovery, but from another point of view, it was the worst discovery ever made for our descendants.
Basically, the field of dark energy, which is still barely understood, causes the expansion of the universe. The expansion of the universe is not slowing down, but speeding up by some metric. The reason that is depressing is because if you have very distant galaxies that are about 10 billion light years away, we would like to meet the people living there or harvest their resources. If the universe was slowing down, we could technically reach that end goal with no deadline. However, with the cosmological constant telling us the universe is expanding at an ever accelerating rate, we no longer have forever to do that. Instead, we must move now, and for some of those galaxies, it is too late. Since we are confined to move at the speed of light, they would just be ripped away from us with the expansion of the universe. In terms of what experimental cosmology taught us about our future, that was the most revolutionary point. In many ways it seemed like bad news, but also maybe not. If anything, I do think that discovery should induce theoretical physicists some humility about making long-term plans as this past advice has become null and void with the constant.
Allison Duettmann: I think there is a really interesting paper on astronomical weights that was one of Boston’s very early papers. I believed it talked of how many subjective light years we are losing by delaying colonizing the universe per second. So, I think he tried to calculate this. Probably many of the assumptions that were made, even in that paper, are also somewhat outdated in terms of how fast you can emulate humans and so forth. Nonetheless, the opportunity is at least appreciated. Further, one interesting thing at the vision weekend panel that we had you on, was that you said the potential end goal could be escaping the heat of the universe. I wanted to dive into that a bit more. Could you just describe what the heat of the universe entails? In the long run, when can we expect to hit that? Of course, we take that with a grain of salt. Nevertheless, as far as we currently know, what is it that we are escaping with heat death, alongside any potential strategies for avoiding it?
Adam Brown: So what is heat death? Heat death is when you use up all of your free energy. It is when the usable energy in a system has been used. If you want to do practically anything, you burn free energy. People talked about whether it would happen before. Here is the theorem: If the cosmological constant is truly constant, and the laws of physics as we understand them are correct, then we only have a limited amount of free energy. Why? We only have a certain number of galaxies in our physical universe. Also, we can extract all of the free energy, but we cannot extract more than the finite energy available. We run the calculations, and there is rather a lot. Nevertheless, it is not infinite and we are getting less every minute. That’s a theorem. If we cannot evade the cosmological constant, then our long term future is to end in a heat death after some finite amount of processing and utility has been released. From the point of view of fundamental physics, that is the number one obstruction we have to overcome if we want to live forever and have an infinite amount of utility in the future. Ultimately, this is both uplifting and depressing.
Theoretical physics thinking to the long term future is uplifting given the amount of problems it is able to obstruct away. The only big problem that presents itself is this heat death of the universe. We have to hope that the cosmological constant, which we call a constant but is in fact able to be manipulated, will be able to be handled appropriately. The good news is that the cosmological constant can in fact be manipulated, changed either discretely or continuously by an advanced-enough civilization. For example, a theory I try to think of often is that of string theory. It is a self-consistent extension of the observed laws of physics. If string theory is correct, then there does not seem to be any fundamental obstruction to us manipulating the cosmological constant once our civilization advances to the appropriate level. Taking it down from its troublesome value towards zero then encourages that all will not be lost. We could control the expansion of the universe and extract energy from the constant itself. So the good news is that the most plausible extension of the laws of physics does encourage that the constant can be manipulated.
Allison Duettmann: Yes, I believe I have read something similar that is called the Final Question. It basically tries to solve this future problem through AI where the AI is always pondering that it does not have enough data to answer this question. I will not give the prompt away, but it is very similar. So, I think we are transitioning into the existential hope part of the interview as well. I will hand it over to Beatrice to speak on the existential hope scenarios for this portion.
Beatrice Erkers: Yes, so thank you for joining us in this experiment Adam. Also, thank you for trying to make what you are doing a bit more accessible for people who are not as immersed into the field. We are trying to communicate the work scientists, like yourself, are doing and how that can help us create a better future. The first question I have is a bit more philosophical. Do you have a positive vision for the future, one of existential hope rather than existential angst?
Adam Brown: Yes, I think physics basically has only good news with the sole exception of the possibility of heat death, which could still be transcended nonetheless. If you read some of these non-hopeful books with global catastrophic risks, and books in that domain, it can be a bit depressing. It is about what man can do to man, which is concerning. The non depressing chapters are those of physics. We realize that there are no fundamental obstructions to us exploiting the incredibly rich resources our universe has sent us. This is with the possible exception of the cosmological constant, but I think of that as surpassable as well. In terms of negative scenarios - such as vacuum decay in which space and time ceases to exist - where they are theoretically possible, it is incredibly unlikely. Even if we wish to go there, we could not. That continues with all of the negative possibilities being incredibly unlikely.
The positive possibilities, however, help us realize the possible hope. There are numerous discoveries that could further technological progress. For example, at CERN we have built a massive collider, which was quite expensive. It seems as though the scaling of building ever bigger colliders in that form is not very attractive. That is only subject to the laws of physics as we currently understand them. It is easy to imagine such a particle that would revolutionize our ability to build bigger particle accelerators, which is what physicists would probably first go to. It would also advance our ability to implement technological progress and facilitate many realizations. For instance, not to get too technical, there are particles called electrons as well as muons, which are heavier versions of the electron. Muons are heavier so they can be accelerated much more energetically in comparison. Also, in being much heavier than electrons, there is a thing called muon catalyzed fusion where you can build a fusion reactor even easier by replacing electrons in some fusible atom with muons.
Now, those things are great, but there is a problem. Muons decay very rapidly in a small fraction of a second. People dream of muon catalyzed fusion and people dream of muon colliders, which may both be possible but there are technical obstacles nonetheless. The decay makes it hard to get them up to speed or catalyze before they decay. As such, it is not really worth the cost. Nevertheless, you could definitely imagine that something similar could be discovered, which could unlock huge numbers of discoveries. Perhaps from that you could create bigger colliders and reach even higher energies and so forth. Overall, there are plenty of possibilities for the laws of physics to be extremely friendly and hopeful moving forward.
Beatrice Erkers: Yes, you sound very hopeful, but there is still so much we do not know. I take it that you do sound very optimistic about the future. Would you say that you are? If so, what got you there? Is it all of the possibilities, are all the risks too far away, or what do you think?
Adam Brown: I would say I am optimistic about the future. First of all, as I said, there does not seem to be any fundamental obstruction to being optimistic. I would say from an emotional point of view, the reason I am optimistic is because, if you look at the last 400 year’s history, there is a clear positive gradient. Now that does not mean it will continue. However, learning about that time frame and progression makes it hard to waiver from that optimism. I believe technology will continue to progress, more people will come out of poverty, and we will have a better future ahead.
Beatrice Erkers: Also, one thing we ask in this interview is the aspect of why. It is very hard for many people to envision positive scenarios. Do you have any guesses as to why that is? How do you think we could improve on that as well?
Adam Brown: I think it is easy to actually be optimistic. There has been so much progress on all fronts basically. So it does not necessarily require imagination to be optimistic, but more so trusting this history. Maybe a way to make people more optimistic is to turn a lot of our energy to focus on how many great successes of the past there are. It is sort of backwards looking optimism for having hope for our future.
Beatrice Erkers: I agree. There is a lot of literature that has come out recently showcasing these progressions that have occurred since industrialization. In terms of that type of literature, would you have any recommendations for someone listening to this? It could be sci-fi, movies, nonfiction, anything. What do you think?
Adam Brown: Maybe I should stick to physics for this question. There are many positive accounts of physics from the past. I think some of the best books not only capture what was discovered, but also the excitement behind discovering it. Kip Thorne, a physicist, wrote a book called Black Holes and Time Warps. I think it is fantastic at capturing the excitement of thinking to black holes. He won the Nobel Prize for the discovery of gravitational waves a few years ago as well. Also, Roger Penrose wrote The Road to Reality. It is not necessarily a personal book, but wonderful for people interested in physics regarding the way a phenomenal mind thinks of these topics. I think he just doesn’t realize how phenomenal he is. As a working theoretical physicist, I will sometimes use it as a reference book to see his take on certain topics, yet it also has an element to where anyone can read them. Those would be my two recommendations.
Beatrice Erkers: Those sound like great recommendations! I have not read either of them, but I will now. Backing up a bit, you spoke about a lot of the long-term risks, such as heat death and bubbles of nothingness. What are the most undervalued risks we should be thinking about right now that you can think of?
Adam Brown: I think the most undervalued risks are probably not coming from physics. Physics doesn’t have many risks for us to worry about. The main thing that people did worry about in physics was before they turned on the Large Hadron Collider at CERN in Geneva. There was some concern that it would create various catastrophic scenarios that could end the world. There was some discussion about how likely could it have been and basically it was 10 to the minus 30, which seems to be unduly optimistic. Nevertheless, the biggest risks I think at the moment are just old school, documented risks that deal with biology and some older 1930’s physics.
Beatrice Erkers: In terms of what technology or science we should be advancing in right now, would that not be physics?
Adam Brown: Physics nowadays is quite exciting, but it has been a while since advances in fundamental physics really impacted the cutting edge of technology. Depending on how you count things, you probably have to go back to 1930’s physics where nuclear energy at the time was cutting edge and impacting day to day technology. Those instances were more so lifting the human condition from a material point of view. That doesn’t mean it couldn’t continue, such as breakthroughs with immediate impacts. Nevertheless, it is generally the case that physics is getting further from breakthrough and fundamental physics, towards technological application. That time scale is more so stretched.
Beatrice Erkers: Perhaps you have a bias towards suggesting physics, but if I were to ask what focus should someone go into if they want to work on creating a better future, what do you think? Do you have any recommendations as to someone new wanting to work on positive futures? What should they specialize in?
Adam Brown: I do not think there is one size fits all advice, so it depends on your interests. I certainly wouldn’t recommend people specialize in physics if it is not interesting to them. I think it is plain that the current revolutions in artificial intelligence and synthetic biology are going to be things that are driving technological progress for better or ill over the next decade or so. If you are interested in an impact on that timescale, those would be fields that I would agree with the consensus going into.
Beatrice Erkers: I appreciate your honesty. This is a complete left turn, but the last question I will ask. It is more so on the life advice for our viewers. What is the best advice you ever got personally?
Adam Brown: Ah, the best advice I ever got I didn’t listen to so that may not count! However, for someone going into this field, I would say dive deep. Don’t feel like you need to know everything, but choose something of particular interest to you and go into depth with that. You can get to the frontier reasonably quickly.
Beatrice Erkers: Thank you, I really appreciate that. It is quite interesting to talk to someone who is used to thinking about these larger time scales. It is also very refreshing! I will hand it over to Allison to ask a few final questions and nuggets of wisdom from you.
Allison Duettmann: Thank you, Beatrice. So we always wrap up with two questions that are a bit more creative. Imagine you are in a creative writing class with these questions. There is one paper from Toby Ord and Owen Cotton-Barratt introducing the term existential hope and the idea of eucatastrophe. We currently have a bounty out for viewers who may be interested in trying to rephrase a similar term, as eucatastrophe can be a bit confusing to people first hearing it. If you happen to have a better term for eucatastrophe, feel free to introduce that as well. We have had a few interesting ones already submitted from a plethora of individuals.
Nevertheless, in terms of thinking about a very specific event, what do you think? When you reference the idea of the cosmological constant, that is almost in terms a catastrophic event. However, if you could think of the opposite right now, what would be a discovery after which you would feel even more hopeful about the long term future? Can you think of a specific event?
Adam Brown: The first thing is I agree with the sentiment in your question. Eucatastrophe more so sounds like a catastrophe happening to you. If it were to be etymologically correct, it should be something like anastrophe. You would still probably have to explain that latter term a lot. We already have the term “breakthrough” or “elevation.” Those would be my recommendations. As for what a breakthrough I could think of, there could be many. For the last few hundred years we have had breakthrough after breakthrough that improves the human condition. As such, there is a certain amount of the idea that if current trends continue, that in itself is a miracle. To me, current trends continuing would be enough of this sort of hopeful event for me, where technology continues advancing and poverty continues decreasing.
Allison Duettmann: Now, imagining a day of the life in this breakthrough, how would you realize that we have reached this trajectory?
Adam Brown: I would say something just like the day when we eliminated polio. In application, I envision a similar day of lifting the last person out of poverty. I just imagine this similar technological progress moving forward.
Allison Duettmann: I like that. You phrased it earlier as backwards looking optimism which seemed to encompass that idea as well. Wonderful. We will try to visualize this with either an art piece or writing. So I think to our viewers, this is a day in the life similar to what we are already living. I find it very interesting because Robin Hanson mentioned a similar concept of dream time. It basically highlighted that, in hindsight, it can be overwhelming to notice the advantages we already had. It is sort of the idea that you do not appreciate something as much until it is gone. As such, remembering this hope that you mention of continuing what we currently have is refreshing.
While we have you here for a few more minutes, I would love to touch on a question mentioned in the chat. You touched upon it a bit already. One of our participants is wondering what you think of the great stagnation in physics, specifically nuclear physics? Also, do you have any other examples along the lines of catalyzed fusion and other technologies as well that may be accessible in the near future?
Adam Brown: Yes, so to a certain extent there has been stagnation in nuclear physics. However, this is only because certain parts of physics are not making progress. I think the reason for this statement is because we have technically won at understanding those areas of physics. Once you understand something, it is hard to understand it a second time, so there is no progress left to be made. We discovered circulation of blood and then it ceased because we understood it. Now, what it looks like to see stagnation is when the topic has been won.
For physics, we basically understand nuclear physics. We put together a standard model of particle physics in the 1970s. The thing about it is that it is great. It explains everything that has ever come out of a collider for decades. From one point of view that means you are a winner. However, the downside looks as though you are no longer discovering anything new so they are no longer hot topics. There are still some question marks like dark matter and other various topics. For the second part of the question, there is just an endless array of potentially useful particles or other technology that could be extremely handy. For instance, if we could discover a manufacturable string that had incredible strength that would be fascinating. That is another example if we could do it, then that would be an extremely useful technology with great applications.
Allison Duettmann: That is a great recipe and answer overall. I think that is an interesting, action-oriented field people could look into to wrap their heads around. Are there any specific bids you think we should discuss that we didn’t?
Adam Brown: Not that I can think of.
Allison Duettmann: Wonderful. We really appreciate it. Thank you, Adam, for your time. Thank you everyone for joining. I hope you all have a lovely Friday and weekend.
Adam Brown: Thank you!