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How Do We Know the Timeline of the Universe?

StartsWithABang writes The history of the Universe happened in a well-known order: inflation ends, matter wins out over antimatter, the electroweak symmetry breaks, antimatter annihilates away, atomic nuclei form, then neutral atoms, stars, galaxies, and eventually us. But scientists and science magazines often publish timelines of the Universe with incredibly precise times describing when these various events occur. Here's how we arrive at those values, along with the rarely-publicized uncertainties.

5 of 153 comments (clear)

  1. Re:We Really Don't by stjobe · · Score: 5, Informative

    LOL. Hypothesis is just a fancy way to say "here's my guess". Whether put forward by Joe Schmoe or Johnatan P. Schmoe, PhD it means the same thing.

    It really doesn't.

    A hypothesis has to make sense, has to be based on observation and/or our best current knowledge of the subject matter. Ideally it is testable somehow, even if only mathematically or theoretically.

    A guess doesn't have to have any of those constraints. "Aliens did it" is a guess, but it's not a hypothesis.

    --
    "Total destruction the only solution" - Bob Marley
  2. Bullshit by Anonymous Coward · · Score: 5, Informative

    Disclaimer: I work in a cosmology department. What you've just written is total bullshit.

    We make predictions, and they work. I could tear apart the nonsense you've written, but instead let me just point to the facts:

    http://xkcd.com/54/

    http://sci.esa.int/planck/5155...

    http://www.astro.virginia.edu/...

    I could go on an on posting pretty pictures and graphs matching data, but let me just say that we work incredibly hard to make predictions from our models, we test those predictions against observations and test many of our systems to over 5 sigma. To say that what we're doing is just guessing is frankly insulting to a lot of incredibly hard working people. We /predicted/ the CMB then observed it. We predicted the power spectrum then observed it. We predict the population densities of stars at certain redshifts, point telescopes and damned well count the things and find them to match. We predict galactic rotations, lensing effects, (integrated) Sachs-Wolfe effects and a hundred
    other little things, and we damned well test them, lining up our models against observations. We certainly haven't got everything right yet - there's a lot of room for investigation as to what went on before inflation, say, or exactly what type of matter dark matter is (but before you say we know nothing about it, I suggest you educate yourself - we don't know what it comprises, but we have damned good bounds on certain properties like its ratio of pressure to density). We don't know why the cosmological constant takes the value it does, but a whole host of checks all come up with the same number.

    So no, we don't have "Guesses". We have repeatedly tested hypotheses from which we observe consistent data and find heavy statistical significance. What you've done is insult a lot of incredibly hard working, very smart people who are very serious about their work.

    1. Re:Bullshit by Ken+D · · Score: 3, Informative

      It's really hard to fit model to data that hasn't been collected yet.
      Or do you not understand when they talk about why they are building a particular space observatory satellite or something like the Large Hadron Collider?

      If one of these experiments doesn't verify the model or contradicts it, and the model is changed, they then go collect even more data. They always want to verify that the model can predict something that wasn't known beforehand. And obviously the model has to match what is known already or it's just crap to start with.

  3. Re:StartsWithABang is an Idiot by Anonymous Coward · · Score: 2, Informative

    The first piece of observed antimatter was the positron and it isn't an atom. The idiot is in the mirror.

  4. Re:We Really Don't by Ken+D · · Score: 4, Informative

    You can understand it to the level of detail you are willing to spend on. So in this case "The Right Stuff" is mostly time.

    You want to spend 5 minutes understanding cosmology, you're going to understand it at the comic book level, same as any other field of study.