What Do We Know and How Well Do We Know It

"Consensus" is an absurd word to apply to science.  It is more accurate to say that we have a series of hypotheses about the universe with varying levels of confidence.  LuboÃ…¡ Motl has a post to get all you physics geeks arguing:  His estimate of the probability certain hypotheses about the universe are correct.  Some examples:

  • 99.999% - String theory is a mathematically consistent theory
    including quantum gravity, even non-perturbatively, at least in some
    highly supersymmetric vacua
  • 99.999% - General relativity
    correctly predicts phenomena such as frame dragging and classical
    gravitational waves in the real world
  • 99.995% - Black holes exist  ...
  • 60% - At very high energy scales, a GUT theory with unified gauge
    interactions becomes more natural zeroth approximation: GUT is correct
  • 50% - Supersymmetry will be found at the LHC
  • 40%
    - The Hartle-Hawking wavefunction or its generalization that will
    require the author(s) to cite Hartle and Hawking correctly predicts
    non-trivial features of the initial conditions of the Universe...
  • 0.0001% - Loop quantum gravity, with the metric as the only and
    well-defined degree of freedom and with quantized area, is a correct
    description of gravity in the real world at the Planck scale
  • 0.00001%
    - One of the ESP phenomena measured in the Princeton lab actually
    exists and can be measured again with a similar equipment

Many more here.

Here are some of my own:

  • 95% - Probability that the Raiders, Browns, and Lions will all botch their first draft picks next weekend
  • 85% - Probability someone will introduce legislation in Congress in the next 7 days in direct response to the Va Tech shooting rampage
  • 80% - Probability that man-made CO2 is contributing a non-zero effect to global temperature
  • 70% - Probability that Barry Bonds will break the home run record this season
  • 60% - Probability that Prince Charles will ever serve as King of England
  • 50% - Probability that all-electric vehicles will make up more than 10% of the auto market in the US in ten years
  • 5% - Probability that man-made CO2 will contribute more than 2 degrees C warming in the next 50 years
  • 5% - Probability of meaningful earmark reform getting passed in Congress
  • 5% - Probability that ethanol or other bio fuels will make any measurable reduction in oil imports.
  • 1% - Probability that the costs of CO2 reduction will be less than the benefits of CO2 reduction
  • 1% - Probability that a true libertarian candidate will be elected president in the next 20 years


  1. Dan:

    Your Prince Charles probability is certainly too low. So long as he outlives his mother, he'll inherit the crown. He won't abdicate. It's better than 60% odds. At least 70.

    And remember how long it took hybrids to break into the mainstream. It'll likely take all-electric vehicles 15 or more years to get 10% market share. I'd put that one down at 15-25%

  2. Knox:

    I always find your posts interesting. I'm responding here to the first line because I first read it here, although I plan to go look at the source. My impression as layman is that string theory hasn't yet made a testable prediction so how could it possibly have the same number of 9's as general relativity which has had thousands, maybe millions of tests? Millions if you include GPS's, anyway.

    On the CO2 causing 2 degree change, my personal guess is 50%. Even if it's somewhat lower than 50%, we still ought to do something about it, and my main reason is so that we dramatically reduce the role of the middle east in world affairs. Go Nukes.

    On the ethanol issue, this is a huge crock and your 5% is too high. I understand that Ethanol is basically break even energy wise, meaning it takes just as much energy to get the corn out of the field and crack it so it's usable. On further reflection, you're probably including some of the more speculative technologies like termite guts and then I would agree with your 5%.

  3. eddie:

    It is more accurate to say that we have a series of hypotheses about the universe with varying levels of confidence.

    Or rather, in this particular case, varying levels of Luboš Motl's confidence. It's not like there's a confidenceometer that you can take objective readings from. The best you can do is ask various individuals what their subjective confidence levels are. And, of course, because nobody accurately estimates their own confidence levels unless something really important is on the line, ask them to put money on it.

    Get those answers from enough individuals and you can start talking about "our" levels of confidence.

    Come to think of it, I guess there is a confidenceometer after all. Maybe someone should ask Motl to put up some contracts on the Hartle-Hawking wavefront. I can see those getting a lot of action.

  4. Ric:

    Your Lions percentage is too low, and will unfortunately remain in the high 90's until the Ilitches sees some pressing need to rebuild yet another Detroit sports team into perennial contenders. I don't think Bill Richardson will live long enough to buy the Lions and make it happen, so our hope rests with Mike and Marion.

  5. mjh:

    1% - Probability that a true libertarian candidate will be elected president in the next 20 years

    Wow. That seems a pretty optimistic. If you'd said next 20 elections, maybe. But in the next 20 years there will only be 5 presidential elections.

  6. rufus:

    We are presently using about 400,000 Barrels of ethanol/day. Is that measurable?

  7. markm:

    rufus: One question is whether ethanol is a net + or - after all the energy used to make fertilizer and pesticides, grow and harvest corn, turn it into ethanol, and ship fertilizer, pesticides, corn, and ethanol around the country.