My Bio: Known as "Mad Max" for my unorthodox ideas and passion for adventure, my scientific interests range from precision cosmology to the ultimate nature of reality, parallel universes, consciousness ( and the future role of life in the cosmos. I’m excited to discuss all of these questions - the bigger, the better!

I'm an MIT physics professor, author of the book “Our Mathematical Universe” (, co-founder of the Foundational Questions Institute ( and the Future of Life Institute (

UPDATE: That's all for a fascinating two hours - it's been lots of fun! I need to head off now, but I hope to check back later.

My Proof: My homepage mentions the Reddit AMA right at the top, as the last item on my book tour.

Comments: 283 • Responses: 50  • Date: 

Jokepapa27 karma

I've been wanting to ask this question for a couple of years now. Hypotetically..

You have a pair of extraordinary binoculars. You use them to look at a man standing on a planet, lets say, 10 lightyears away. Wich means you see him as he were ten years ago.

You start to travel towards the planet, still looking at the man. As your speed increase, will you see that mans life fast forward before your eyes??

MaxTegmark26 karma

Yes! :)

ChazzyPants13 karma

Hi Dr. Tegmark, I was reading "Our Mathematical Universe" last night and you said that the Mathematical Universe Hypothesis cannot include arbitrary initial conditions because it would constitute an incomplete description. If a computer program can be reduced to a mathematical object, can't you then incorporate initial conditions? What makes a mathematical description of the universe different than a computer program?

BTW, I'm really enjoying your book and thanks for doing this AMA

MaxTegmark12 karma

Thanks for your encouraging words! If a computer program has "initial conditions", then there's something unspecified about either how its variable are initialized or there's an outside world outside the computer that contains additional information that can be used as input. If the mathematical universe hypothesis is true, then the mathematical structure refers to our entire physical world, so there is no "outside" that it's in contact with.

cybis32013 karma

Hi Max, many ideas explored in your book are centered on the concept of infinity. E.g. The idea that there are infinite copies of you in an infinite number of universes, etc. But towards the end of the book you say that infinity is incompatible with the idea of a mathematical structure. You hint there might be a fine granularity to reality. I've probably misunderstood something, but isn't there a contradiction there?

MaxTegmark27 karma

Absolutely! So all those infinities might get replaces by numbers that are merely very big. If they're sufficiently small, you may even lose your duplicates, but I think that's unlikely at Level III.

I was not taking issue with infinity in mathematics, but in physics, arguing that we lack experimental evidence that there's anything truly infinite in the physical world - for example, an infinite number of particles, an infinite magnitude of something (energy, density, curvature, etc.) or a true spatial continuum with an infinite number of points. Of course I assume the contrary in every single physics class I teach at MIT, by introducing 3+1-dimensional pseudo-Riemannian manifolds to model spacetime, by introducing real-valued quantities such as the electric field components in this morning's electromagnetism class, etc. However, whereas a generic real number requires infinitely many decimals to specify, we've never measured anything to more than 17 significant digits in physics, and have good reason to think that too many significant digits don't even make sense: for example, that the continuum model of space breaks down below the Planck scale of about 10-34 meters. Moreover, many examples of where I use the continuum in my teaching are known to be fundamentally incorrect: whenever I use the concepts of temperature, density and pressure as continuous functions of position to derive the equations of fluid dynamics, the properties of sound waves, etc., I know that the continuum is merely convenient approximation, since real substances are made of individual atoms for which it doesn't make sense to speak of a temperature, say. To me, this raises an embarrassing question for us physicists: if infinity is merely a convenient approximation in some circumstances, how do we know that it isn't merely a convenient approximation in all circumstances?

As I describe in chapter 11 of the book, it is precisely the hypothesis that space is a true continuum that can expand by arbitrarily large amounts that is responsible for one of the most embarrassing problems facing physics today: the cosmological measure problem that prevents us from making reliable predictions. I therefore feel that the infinity assumption in physics must not be exempt from the list of assumptions that we question. I feel that this point deserves to be discussed independently of and separately from any issues to do with the MUH. Sorry about the length of this reply, but as you can tell, infinity is something I get pretty worked up about!

Benito910 karma

Dear Max, speaking as a young human just about to apply for their undergraduate degree, do you have any concrete advice as to what decisions or areas of study in the next few years will allow me to have the greatest positive impact in the world during my life e.g. by placing myself in an good position to mitigate global risk from UFA? Feel free to assume strong mathematical skills.

MaxTegmark11 karma

Go to a college with a strong CS-department, study AI and aim to do AI safety research! (Do mainstream AI applications in parallel to get admissions, jobs and $$$ to support yourself.) In the mean time, keep in touch with the volunteers at organizations like MIRI (, FHI, CSER and FLI ( ;-)

KomodoMoses9 karma

Is there an afterlife?

MaxTegmark26 karma

I'm betting against it, unless you count getting uploaded/simulated, so I suggest living this life to the fullest! ;-)

frenzyboard9 karma

What do you think of the ten thousand year clock project? Do you think people will still be here in ten thousand years to appreciate it?

MaxTegmark18 karma

I think it ( is awesome, as humanity is way too shortsighted. Playing Russian roulette with our civilization every decade or century (by reckless use of nuclear weapons technology, for example) is a rather pathetic strategy for lasting 10000 years, not to mention the billions or trillions of years that our future universe has to offer. This project aims to draw attention to existential risks, and such attention is IMHO sorely needed: consider that there are more people on Reddit who have heard of Justin Bieber than of Vasili Arkhipov (, even though it wasn't Justin whom we should thank for us all being alive and able to do this AMA because he singlehandedly stopped a Soviet nuclear attack in 1962. This motivated me to co-found - you're welcome to join!

frenzyboard7 karma

Well I think it's only fair for people to be short sighted. They only live for 70 years or so.

Do you think technology will allow us to stretch that life expectancy into significantly longer periods any time soon?

MaxTegmark17 karma

As a father, I think it's not fair for us to be so short-sighted that we ignore future generations. :)

VerumInInanis9 karma

Hello Pr. Max.

Have you ever done psychedelic substances? If so have they affected your view on consciousness or any other science you are engaged in? If not, why not?

What hope do you have for the alcubierra drive?

MaxTegmark22 karma

Not yet! My current plan is to postpone such experimentation until I'm old enough that my brain is getting fried anyway... :)

STOpandthink9 karma

Max, really glad to see you supporting and advocating for x-risk reduction, particularly in the field of AI. What do you think are the biggest challenges in that field? What do you think we can do to address them? What's your personal confidence 50% interval for arrival of smarter-than-human AI?

MaxTegmark13 karma

It's really hard to give confidence intervals, but I won't be too surprised if it happens in my lifetime. A challenge today is that the debate has become overly polarized: scaremongering headline hunters can antagonize AI-builders to the point that they become reluctant to engage in a constructive level-headed discussion. aims to reclaim the middle ground by asking: what can we do today to reap the future benefits of AI while avoiding pitfalls?

grkles8 karma

What do you make of the current standard in reporting astronomy news? i.e., press conference before refereeing?

MaxTegmark16 karma

For better or worse, that's actually emerging as the new standard in most of physics, and was also done for the Higgs Boson announcement. I think it's a reaction to refereeing being so slow, and to the fact that some experiments are so complicated that it's hard for a referee to singlehandedly vet it anyway. There's still a strong incentive against jumping the gun, since people are putting their reputations and careers on the line.

Doctor_Mod8 karma

Do you think there will an AI with consciousness in our lifetimes and is there any real danger of a 'rogue' AI?

MaxTegmark15 karma

I think superhuman AI in our lifetime is plausible - there's certainly nothing in the laws of physics saying that intelligence requires carbon atoms. Here's what I think about potential risks: This was one of the key reasons I co-founded - if you're interested in these issues, please surf over and join us!

Azog7 karma

Good evening from Amsterdam, sir. I have a question in connection with your recent statement saying that the "consciousness is the way information feels while it is being processed". Soon enough some of our most advanced computers will have met all 4 requirements for a physical system to be conscious - in the light of the above, do you foresee any significant advances in the AI field within next 5-10 years?

MaxTegmark14 karma

Yes, I foresee huge advances in AI during the coming decade. But we still don't understand with confidence what makes an information-processing system feel conscious (have a subjective experience) as opposed to simply behaving as if it were conscious, and there's great controversy here. For example, my neuroscientist friend and consciousness pioneer Giulio Tononi thinks that if you simulate me perfectly on a regular computer, I won't be conscious, but rather a zombie whose behavior is indistinguishable from mine. I'm fascinated by these questions and look forward to doing further research on them.

jim23107 karma

Hi Max, You subbed in for Tali once during an 8.02 lecture this past semester, and you had some really interesting things to say about the current state of physics research.

What do you think of the Alcubierre drive and Q-thrusters for interplanetary/interstellar travel?

Do you think you will be able to buy a ticket to Mars within your lifetime?

MaxTegmark14 karma

Go MIT go! I'm betting against the Alcubierre drive but for the Mars ticket. I think the way to do Mars travel is to send people who volunteer to go on a one-way ticket, which is way cheaper. The current NASA obsession with bringing everyone back home safely makes it dramatically harder and costlier, and goes against the traditional spirit of exploration. I don't think it will be that hard to find volunteers.

zaikanekochan6 karma

We haven't been back to the moon in ages. We need to go back, right?

MaxTegmark12 karma

If we want to go to Mars and beyond, going back to the Moon is the logical first step. I know it's now as sexy ("been there, done that"), but it's a great way to perfect required technologies and WAY easier.

Jo_Tschaena6 karma

Hi Mr. Tegmark,

do you think we will ever be able to find a Theory of Quantum Gravity?

MaxTegmark3 karma

I think we have a good shot at it, even though it won't be easy: watching this gave me one of my very best laughs of 2014! ;-)

brannmark4 karma

Hi Max,

I very much enjoyed reading your book. I suppose you are familiar with the writings of Douglas Hofstadter (in particular, Godel, Escher, Bach). What is your opinion on his thoughts about consciousness, and did Hofstadter in any way have an influence on your work?

Greetings from Sweden

MaxTegmark5 karma

Heja Sverige! I read Gödel, Escher, Bach back in Stockholm in the 80s, and found it very inspiring. That's where I first learned about formal systems, so it had a direct influence on my book ;-)

ohheyitswes3 karma

Do mathematicians or physicists know of any mathematical structures that when computed would approach the level and type of complexity observed in our Level I Multiverse? Level II? Level III? I don’t mean things like the square root of 2, or a Mandelbrot fractal – but a mathematical structure that would produce the type of complexity we observe. Thanks!

MaxTegmark6 karma

Short answer: maybe. String theorists of course hope that string theory has precisely this property, but they still haven't fully defined exactly what the mathematical structure is supposed to (to the standards that a mathematician would accept as rigorous), and they also haven't managed to make detailed testable predictions. The top competitor loop quantum gravity is in a similar situation.

Azog3 karma

Mr. Tegmark, do you believe that there will be a "bypass" of the theory of relativity that would enable us to reach remote destinations at apparent superluminal speeds? Maybe via such hypothetical technologies such as Alcubierre Drive or something similar?

MaxTegmark12 karma

I'm betting against it. I used to think that this was a pity, but I've changed my mind: it's actually very convenient for us if malevolent extraterrestrials are unable to reach us for billions of years even if their technology is way ahead of ours, simply because the laws of physics ban bypasses. :)

saktens3 karma

Hi there Max, I immensely enjoyed your Mathematical Universe! It has been giving me food for thought for quite some time now. Something that keeps popping up in my mind (and the minds of my doppelgangers in the Level I Multiverse):

In the chapter "Are We Living in a Simulation?", on page 349, in the footnote, you write:

*Indeed, as pointed out by Ken Wharton in his paper "The Universe Is Not a Computer," at, our laws of physics may be such that the past doesn't uniquely determine the future, so the idea that our Universe can be simulated even in principle is a hypothesis that shouldn't be taken for granted.

My questions/thoughts, then, are:

If the world is considered a 4D object, what is causality? Can I write up the analogy and compare the slope of a mountain to the speed of a falling raindrop? The slope can be estimated around a known point, or you can find some geological rule to help you, but it certainly can't be predicted/simulated all the way from valley to peak!

Is the change of an object through time analogous to the change of an object through space?

Suggestions for further reading would also be very much appreciated, hilsen fra Norge:)

MaxTegmark3 karma

If the world is considered a 4D object, what is causality? Causality is then the ability to compute all of it from just a single thin 3D slice. For a mountain, you can't compute it all from a slice, but if its shape obeyed a particular kind of equation (known by the nerdy name "partial differential equation with the Cauchy property"), then you could!

moybien3 karma

I've heard physicists say that our universe is probably infinite or that it probably doesn't have an edge. If the multiverse in the context of cosmic inflation is right, then does our "pocket universe" or "bubble universe" have an edge?

MaxTegmark6 karma

A great question with a very subtle answer: general relativity + inflation can actually start with a small and finite volume of space and create an infinite pocket universe inside of it. If you want to dig deeper, I explain this in detail in chapter 5 of my book (

pv993 karma

What are Neutrinos and how are they formed?

MaxTegmark4 karma

Neutrinos are a ghostlike particles that have been around since the cosmic dawn. They're so shy that they typically fly right through earth without interacting - but once in a blue moon we can catch them in our detectors. If you want to delve deeper:

jkeyc3 karma

How do you feel about death?

MaxTegmark14 karma

Sounds really boring... :)

timothygale3 karma

Hi Max. I never understood this. If nothing travels faster than the speed of light, then the expansion after the big bang is not possible. That would have to expand fast than the speed of light? Am I getting the wrong?

MaxTegmark9 karma

According to special relativity, nothing can travel faster than light. But general relativity is more liberal: nothing can travel faster than light through space, but space itself can expand as fast as it wants to. Indeed, our universe is expanding in such a way that some galaxies are currently moving away from us much faster than the speed of light. If you want to delve deeper, I explore this in great detail in chapter 3 of my book (

-Chazz-3 karma

Hi there; are you a believer in extraterrestrials?

MaxTegmark12 karma

To me, the most interesting question isn't if extraterrestrials exist, but how close our nearest neighbors are. The former is essentially guaranteed if (as inflation suggests) space is infinite and has infinitely many planets. However, as I argue in chapter 13 in my book (, I'm betting that the nearest extraterrestrial neighbors with telescopes are more than 1026 meters away, i.e., outside of our observable universe, which means that their existence has no influence on us in practice. Beware that mine is a controversial minority view - that said, the common counterargument that "there are just so many stars that there's gotta be life somewhere" isn't a quantitative one, and we need to work the numbers!

stevenue3 karma

Hi Max, What are your thoughts concerning the announcement by NASA researchers that they have some unexplained success with the EmDrive? Is it a fluke, could it have something to do with quantum non-locality, or could it be something else?

MaxTegmark8 karma

I'm still waiting for a detailed technical report that I can read.

JamesSamuelson1112 karma

Hello Mr. Tegmark

Are you interested in consulting on film and television projects that are about parallel universes?

MaxTegmark3 karma

Sure: I've often done that in the past - at least in this particular universe. :)

Frozenfire422 karma


For an Physics undergrad with a few years off from school aspiring to go back, what would you recommend to help with trying to get into a top tier physics grad program?

MaxTegmark4 karma

Go talk with professors near where you live and try to get involved as a research volunteer or intern. And keep reading. And apply to MIT! ;-)

ohheyitswes2 karma

Do the experiments at the Large Hadron Collider at CERN tell us about the ultimate fate of our place in the Multiverse, and does this have any implications for the MUH ? Thanks!

MaxTegmark3 karma

The ultimate fate of our universe depends on the nature of dark energy, and the LHC might shed light on this by discovering/not discovering supersymmetry, teaching us more about unification physics, dark matter, etc. Also, the Higgs boson is in my opinion the most spectacular thing yet to be successfully predicted using mathematics, and therefore another feather-in-the-hat for the idea that our universe is deeply mathematical.

colinnolt7172 karma

If, as you suggest, the universe and all that we perceive to be reality ultimately turns out to be a mathematical construct, then in your opinion, is what we experience as reality the process of solving the equation, or the product of an already balanced equation?

MaxTegmark6 karma

Equations are simply descriptions of the mathematical structure that is our reality. That's IMHO why we find that equations describe our physical world so well. For example, a planet orbits in an ellipse described by an equation (x/a)2 + (y/b)2 = 1.

foodeater1842 karma

I sent you a private message on here yesterday but I'm not sure if you saw it. Essentially, my questions are: What should I study to reach the forefront of consciousness "theory", and do you know of any way to study it in a graduate school kind of setting?

MaxTegmark5 karma

I recommend getting to it from either the neuroscience side or the AI side. Since it's still considered non-mainstream, it's important that you also do something else in those fields to guarantee a career where you can keep enjoying your consciousness research. Here's some of what I'm excited about regarding consciousness:

janstrukelj2 karma

So, what role do you think we have in the universe, what it will be in 20 years and when do you think the role will get much bigger than it is now?

MaxTegmark6 karma

I think we have a very significant role in our universe. IMHO, it's not that our universe is giving meaning to us, but that we are giving meaning to our universe. If nobody was consciously aware of all those galaxies out there, they wouldn't be beautiful or meaningful, but just a giant waste of space as far as I'm concerned. I think our generation has reached a fork in the road we're well either go extinct or help life flourish in our cosmos for billions of years to come. More on this at

Peter_Jennings_Lungs2 karma


MaxTegmark10 karma

A black hole is a region of space from which light can't escape because of gravitational pull. For example, if you compressed the Sun down to a radius smaller than 3 kilometers, it would form a black hole. Don't fall into one!

escherbach2 karma

Is inflation unitary?

MaxTegmark3 karma

Yes, that's what I think (because quantum mechanics is unitary).

amennen2 karma

Two questions: first, I know that if you start randomly changing physical constants, you get a dead universe, but might there be other configurations of the physical constants distant from ours that would also allow for life to evolve? If so, what might living in such a universe be like?

Also, do you have opinions on what the correct way to interpret anthropic evidence is (the self-sampling assumption, the self-indication assumption, or something else)?

MaxTegmark5 karma

Yes, there might very well be other "islands of habitability"; we don't know much about them yet, and I think that's a fun area for future research. Regarding the self-sampling assumption, the self-indication assumption, etc., I go into my views on them in detail in chapter 11 of my book (

moybien2 karma

I've heard physicists say that the gravitational force is carried by the graviton. I know that in general relativity the gravitational field is spacetime itself. So is the graviton the fundamental constituent of spacetime or is it a particle in spacetime?

MaxTegmark3 karma

Great question. We often think of gravitons as small ripples in the fabric of spacetime, but once we have a complete theory of quantum gravity (which we still embarrassingly lack), we'll probably realize that even this fabric itself is merely an approximation, emerging from a soup of gravitons akin to how the seemingly smooth water in the ocean emerges from the soup of water molecules.

pv992 karma

Hello Dr. Tegmark, I'm currently reading your book, Our Mathematical Universe and I just finished reading the section discussing World Lines. However, I'm a bit confused about what exactly World Lines are. What are World Lines and do they link us human beings with spacetime itself?

MaxTegmark2 karma

A worldline is a curve through the 4-dimensional spacetime, so your personal worldline specifies your position in space at each instance. Here's more:

dansplain2 karma

Let's say FLI successfully develops A.I. regulations that would mitigate risk. Now, assume that these regulations cut into the profits of A.I. corporations. How do you expect to enact these regulations in the current political climate? Look at climate change for a somewhat analogous scenario.

MaxTegmark6 karma

I think it's premature to talk about regulations: what we need first is more AI safety research, to shed light on what direction we'd hope to see things go. Currently, almost all AI research is focused in improving AI capability (since that's where the near-term profits are), not on safety.

Pamunkey2 karma

What was the happiest moment of your life Max? Is there a formula to express it?

Thanks for all your work. It's always thought-provoking.

MaxTegmark5 karma

I've been fortunate to get to experience many. Meia saying "I do" in our back yard will be hard to top... :)

RyanAHixon2 karma

What do you think is a more viable choice for a career in science? Astrophysics or Particle Physics. I am interested in both and I want to choose the one that I am most likely to get a job in. I'm dream job would be to work at CERN.

MaxTegmark2 karma

You can have your cake and eat it if you go into astroparticle physics! My advice is to study the basics (in both astro- and particle physics) and seize whatever the most enticing opportunity is later on.

BRickANDstONe2 karma

Hey Professor Tegmark, I read your book this summer and just wanted to let you know how much I enjoyed it. Do you do the dinner with students program at MIT? (I'm currently a student, although not course 8)

MaxTegmark3 karma

Thanks for your encouraging words! Yes, I love that dinner and attend as often as I can. Go MIT!

moombathon2 karma

What has been the weirdest/most interesting thing you've seen/heard of happening on MIT's campus?

MaxTegmark9 karma

The undergrad pranks are mindblowing. One morning, I looked out my office window to see a life-size replica of the Apollo 11 Lunar Lander atop the great dome.

fusionftw2 karma

What are the most exciting areas of physics being explored right now?

MaxTegmark4 karma

Personally, I'm extremely excited by the interdisciplinary science of consciousness at the interface between neuroscience, AI and physics.

YUHDEW2 karma

What is your opinion on consciousness, do we perceive the world as it is? or at least for the most part?

MaxTegmark5 karma

Here's what I think about consciousness (TEDx): If I've learned anything in my career as a scientist, it's that the ultimate nature of reality, whatever it is, is very different from how it seems. That's one of the main themes of my book:

tigerplasticity2 karma

Hello, Mr. Tegmark! I really enjoyed your book “Our Mathematical Universe.” I have two questions. In your book you say that “Surely You're Joking, Mr. Feynman!” changed your life. Have you read any fiction or sci-fi that has had a lasting impact on your psyche? As a proponent of the Consciousness as a form of matter theory do you ever envision a “space-race” between governments, but in the realms of exploring the boundaries of consciousness?

MaxTegmark4 karma

As to your sci-fi question, I love Greg Egan’s “Permutation City”, whose explorations of the ultimate nature of reality blew my mind and inspired my own research. I view a race between governments in the area you mention as quite unlikely, given how tiny fraction of their budgets are spent on fundamental questions research. That's why we founded

JackNahmias2 karma

Professor, do you think that, maybe someday, math could be able to explain everything? everything include us, people, our behaviour, our feelings. And if your answer is yes, do you think that formula could help us to improve ourselfs?

MaxTegmark3 karma

Yes to your first question. But I think we need to be humble and acknowledge that there are many ways for us to improve our behavior and reckless management of this planet even today, without waiting for a deeper understanding of physics! :-)

MultiverseIV2 karma

If there is a problem with inflation where does that leave Level II multiverse?

MaxTegmark3 karma

My guess is that we'll end up with a Level II multiverse that's smaller (not infinite), but still big, and that even if inflation wasn't eternal or precisely the way we usually teach it at MIT, it still happened in some form.

TegUrit2 karma

Do you have any fun predictions about advances of quantum computing ? ( So far computing has been limited to a binary system, where information can be either classified as a ‘yes’ or ‘no’, or 0 and 1-but now things are going to change completely)

MaxTegmark3 karma

We did a poll at the quantum computing session at our January conference of, and most people predicted that quantum computers would be able to do things classical computers cant by 2050.

YoureAllCoolFigments1 karma


MaxTegmark9 karma

1) Even though, as Einstein pointed out, the distinction between past, present and future may be merely an illusion, with time being merely the fourth dimension in an unchanging spacetime, the fact that nothing seems able to travel faster than the speed of light prevents us from seeing more than a small fraction of it all (our backward lightcone). I explore this in much greated detail in chapter 11 of my book (

2) I had a fun and spirited debate about this with Stuart Hameroff at a consciousness conference he organized in April, and I enjoy following the latest development. Of course evolution will take advantage of quantum tricks whenever it can, to transport energy faster in chlorophyll, say, but there's IMHO no evidence that it's been able to take advantage of this by making our brain a quantum computer.

3) Connecting physics with the neuroscience of consciousness.

joebob8011 karma

Who would win in a fist fight: you or Neil Degrasse Tyson?

dansplain0 karma

Excellent question. Max is pretty tall, so he's got reach.

MaxTegmark3 karma

But he's got both brain and brawn! I think I'd need to momentarily distract him, perhaps with a sexy exoplanet image off to the side... :)

Shouldbeworking22-3 karma

What did you think of the last episode of Lost?

MaxTegmark4 karma

I've unfortunately only seen it in a parallel universe, and haven't managed to figure our what that Max thought of it... :)