Do You Think Inflation Probably Happened?

I was at a meeting in Princeton a short while ago, a small and focused workshop for people who are working on fundamental questions in inflationary cosmology. I hope to talk more about the meeting once the website is up (talks were not recorded), but here’s a simple question: what is the likelihood you would attach to the idea that some form of cosmic inflation occurred in the early universe?

My answer was 75%, which I thought was generous. It’s very hard to give a high probability to a speculative theory about what happened at energy scales to which we currently have no experimental access. But I found myself on the low end of opinions at the meeting, where the median was about 90% confidence. Of course, these are people who work on inflation professionally, and have chosen to do so. When I came home to ask the same question of my lunch crowd at Caltech, the answers were more like 25%.

An interesting glimpse into the non-unanimity of scientific opinion when it comes to untested theories. So, just for fun, let’s ask what your personal likelihoods are for the following theoretical ideas.

  1. Inflation
  2. Supersymmetry
  3. String theory
  4. Some form of Higgs boson
  5. Large extra dimensions
  6. WIMP dark matter
  7. Any non-cosmological-constant explanation for cosmic acceleration

I’m not defining these very carefully, and let’s posit that we’re not interested in weaseling about what the definitions mean. We’re asking what you think the probability is that, if you were to ask an omniscient being who knew everything about the workings of Nature whether these ideas were part of how the world works, would they answer in the affirmative. What do you think? (It’s helpful if you say a bit about what kind of perspective you are coming from.)

178 Comments

178 thoughts on “Do You Think Inflation Probably Happened?”

  1. @Rhys: I think it’s an effect of physics being an interesting subject to many but requiring quite a bit of effort to actually understand in detail. Laymen have no real way of judging which theories seem likely and which don’t, so we’re reduced to appeal to authority or random emotionally motivated “I don’t believe it”-style statements. (Some variation of argument from ignorance?)

    I’ve been reading physics blogs for some time now and worry a bit that there’s no way for me to judge how likely the writings are to be correct (beyond checking a variety of sources etc.), but there’s no way I’m spending years on studying physics just because I’m interested in the current developments.

  2. Rhys: I suspect that most of the followers of this blog are (like me) just interested amateurs – particle physics and cosmology isn’t what puts bread on our tables and gas in our cars. Having invested in and been flummoxed by e.g., The Road to Reality, what are we to do? So we read Elegant Universe, Eternity to Here, et al, and see what we can glean. So, this poll perhaps has no intrinsic value, it’s just a lot of fun.

    But that doesn’t mean that the topics themselves are valueless – quite the contrary of course. The more that people like Sean can “bring fundamental physics to the masses” the better we all will be, especially in contrast to the floggers of religion and other superstitions.

  3. You should ask the same people how their percentage changes if B-mode polization is detected. That would be really interesting, given how many polarization experiments there are.

  4. 1. Inflation – 80% ( but exact mechanism may never be known )
    2. Supersymmerty – 70% ( by Dirac’s aesthetic criteria alone )
    3. String theory – 1% ( recent papers by Bert Schroer – arXiv.org – are devastating )
    4. Higgs boson – 95% ( electroweak symmetry breaking is almost a certainty )
    5. Large extra dimensions – 1% ( same as small extra dimensions )
    6. WIMP dark matter – 40% ( dark matter just as likely to be shadow matter – no weak
    just gravitational interactions )
    7. non-cosmological-constant – 5% ( ‘if it walks like a duck …’ )

    Former physicist.

  5. A question to those having SUSY much lower than WIMPs: Is your thinking on this mostly that the observations point to WIMPs but SUSY doesn’t make that much sense, or is the difference made up by a theory you consider very likely that includes non-SUSY WIMPs? I’ll go ahead and assume Garrett in #60 is of the latter persuasion, but what about the rest of you?

    Edit: I’m asking because I thought WIMPs were one of the main motivations for SUSY, while other theories don’t give you WIMPs that easily.

  6. Okay, just because it’s hilarious that my opinion could be included:

    1) 40%
    2) 75%
    3) 50%
    4) 20%
    5) 1%
    6) 75%
    7) If “experimental and theoretical error” counts, then 60%

    Background: I’m a law student and mediator with a good layman’s grasp of physics. I’d love to see this broken out into insider v/ outsider, to see what exactly popular science books and blogs are teaching people.

  7. I’m honestly surprised by the amount of confidence in WIMP dark matter coming from people who say they’re particle physicists of one sort or another. Axions are pretty compelling, and neutralinos decay in an awfully big subset of the SUSY models in the literature. Neither axion DM or WIMP DM (or some sort of hidden-sector DM) would surprise me in the least.

  8. 1. Inflation 80%
    2. Supersymmetry 60%
    3. String theory 40%
    4. Some form of Higgs boson 80%
    5. Large extra dimensions 1%
    6. WIMP dark matter 80%
    7. Any non-cosmological-constant explanation for cosmic acceleration 1%

    As a physics undergraduate, I worked in a cosmology lab, but graduate research was on more down-to-earth topics (geophysics:disasters). I stay on top of the literature for entertainment purposes (researcher for scifi), and want as many conflicting theories as possible to provide plausibility for the next insane plot.

  9. There is no need for Inflation Era (nor DE, nor DM, nor cosmological-constant) as one can find a new model with only one parameter (Hubble constant) at:

    A relativistic time variation of matter/space fits both local and cosmic data (arxiv astro-ph 0208365)
    http://arxiv.org/abs/astro-ph/0208365

    undiscussed, so what?

  10. Pingback: How likely do you think it is that <theory> is right? | Galactic Interactions

  11. 1. Inflation – 43%
    2. Supersymmetry – 50%
    3. String theory – 40%
    4. Some form of Higgs boson – 95%
    5. Large extra dimensions – 10%
    6. WIMP dark matter – 40%
    7. Any non-cosmological-constant explanation for cosmic acceleration – 30%

    I’m not expert in none of these topics. I’m theorist working on string Pheno… “pheno” 😉

  12. Inflation – 90% I always thought this question was settled and I never heard any other explanation
    Supersymmetry – 10% It sounds nice on paper, but since we haven’t found anything yet I’m not too hopeful
    String theory – 20% Sounds really interesting, but I doubt we’ll be able to really test it in our lifetimes.
    Some form of Higgs boson – 90% any other explanations why we have mass?
    Large extra dimensions 1% depends by what you mean by large?
    WIMP dark matter 90% The dark matter has to be something
    Any non-cosmological-constant explanation for cosmic acceleration 2% If they didn’t cancel Stargate Universe we might have found out 🙂

    A suggestion, make a histogram of all the responses, it’d be interesting to see how everyone feels. Also you could ask if there is a graviton.

  13. Warning : I am not a physicist but Physics are my only readings… I just love the subject.
    So here are my answers :
    1 – 95%
    2 – 90%
    3 – 90%
    4 – 99%
    5 – 80%
    6 – 85%
    7 – 5 %
    Best regards,
    Shannon

  14. Credentials : Smart guy that reads books 🙂

    1. Inflation – 80%
    2. Supersymmetry – 65%
    3. String theory – 50%
    4. Some form of Higgs boson – 98%
    5. Large extra dimensions – 20%
    6. WIMP dark matter – 40%
    7. Any non-cosmological-constant explanation for cosmic acceleration – 5%

  15. Pingback: Predictions of physics theories « Grok Life

  16. Based on the things we know we know, not to mention the things we know we don’t know, and ignoring the things we don’t know we don’t know, and assuming an unknown % error, in the spirit of Rummy I say…

    1. Inflation (or something like it): 70%
    2. Supersymmetry: 60%
    3. String theory: 10%, but if SUSY, 40%
    4. Some form of Higgs boson: 95% – as ‘t Hooft observes, we’ve already seen 3/4 of it.
    5. Large extra dimensions: 5% – very cute idea, but seems contrived
    6. WIMP dark matter: 65% (~ same as SUSY but with the chance of axions)
    7. Any non-cosmological-constant explanation for cosmic acceleration: 2% (but if there are large extra dimensions, 50%)

    Once a physicist, still one in spirit.

  17. 1. Inflation: 85% (I’ve thought of cosmology in terms of inflation for so long that giving it this high of a probability may be mostly due to lack of imagination on my part)
    2: Supersymmetry: 15% (though I’d also give this probability my largest error bars)
    3: String Theory: 5%
    4: Higgs: 97% (The aesthetic value of the theory probably influences my willingness to claim that it’s true, at least a little bit. Plus, we find new particles all the time–what’s one more?)
    5: Large extra dimensions: 1%
    6: WIMP dark matter: 92% (see 4.)
    7: non-cosmological-constant: 15%
    I’m almost disappointed in the low probability I assign for (7), since that would be most interesting to me professionally. I’m currently working in observational cosmology and astroparticle physics.

  18. Not even an educated guess, but sensibilities lead me to guess
    1. Inflation – 55% Only slightly more likely than Penrose’s latest story, which I like.
    2. Supersymmetry – 75% Seems so likely
    3. String theory – 80% Almost certain that quarks are only higher organizations of energy
    4. Some form of Higgs boson – 05% Give it to hidden dimensions of #3 and #5
    5. Large extra dimensions – 70% Assuming, of course, we’re not the most intelligent creatures at the center of the universe.
    6. WIMP dark matter – 90%
    7. Any non-cosmological-constant explanation for cosmic acceleration – ??% you mean ANY? Sure, then, make it 100%

  19. Inflation — don’t know
    Supersymmetry — 95%
    String theory — String theory in current state: 0%, Some evolution of string theory: 80%
    Some form of Higgs boson — 98% (inclusive of composite models etc)
    Large extra dimensions — 2%
    WIMP dark matter — don’t know
    Any non-cosmological-constant explanation for cosmic acceleration — 2%

  20. Oh oh oh! I love polls like this, gets me away from doing actual science!

    Since I subscribe to the Colbert “if you don’t know the answer to a mystery, it must be 50-50”, I vote 50% to all of the above.

    My background : I was Sean’s student! So it was all his fault if you don’t like my answer.

  21. @111. Chris

    You referenced Stargate: Universe as your “Appeal to Authority.” That makes me your authority. Thank you! I’ll count this as yet more proof that credible science in entertainment serves a purpose.

    The remainder of this season does give hints as to a few of the Stargate scientists’ views on some of these topics. The actors were pretty adamant about what their characters would think! Watch the backgrounds carefully, since it’s non-explicit in the scripts.

  22. Inflation – 95% There is pretty compelling evidence for some sort of an inflation to have happened.
    Supersymmetry – 65% I want this to be true more than I actually think it might be.
    String Theory – 50% (Composed of 100% as in, there is nothing really wrong with it, and 0% as it will never be a “useful” theory)
    Higgs – 75% As much as I dislike the idea, I can’t think of many viable alternatives.
    Large extra dimensions – 0% No, just no.
    WIMP dark matter – 95% We should know this one for sure soon. I don’t think WIMPs will make up all of the dark matter though.
    Any non-cosmological-constant explanation for cosmic acceleration – 100% A number is not an explanation 😉 1% for the actual meaning of the question 🙂

  23. You can have a strong opinion that something’s a B.S. explanation without having an alternative in mind, and you can have strong opinions about things you don’t spend your whole life studying. For example:

    String theory sucks.

    QED

    I just think scientists have this underlying notion that physics is constantly on the brink of “understanding everything” (if we could just find that next boson!), and I don’t think that’s justified.

Comments are closed.

Scroll to Top