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.

Comments

We don't

[Anonymous Coward]

We pretend we do, but it was actually re-created yesterday after the reboot of God's Second Life server farm.

Re:We don't

[Z00L00K]

Which is a theological way to define what Douglas Adams described on why the universe is so elusive to explain.

Another aspect is also - how do we know that the Universe was created at Big Bang. What if it was an empty void that suffered a spontaneous mass appearance.

Or do we live on the inside of a giant black hole?

Re:We don't

[disposable60]

What if it was an empty void that suffered a spontaneous mass appearance.

And somehow that's not a big bang?

Re:Doesn't really answer the question

[viperidaenz]

Think of it as a perfect sphere.

We Really Don't

[TrollstonButterbeans]

"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"

This is the comic book version of what happened.

We do not know that it happened in that manner. This is the popular version of what our current guesswork is and no more.

It should not be taken as "canon" or "real" any more than 2001 The Space Odyssey intro with apes inventing the use of bones as tools.

Because "science" --- the one with hypothesis, testing, reproduction of results is different than the speculation one --- which is very often quite wrong. If you want a recent example, there were many theories about the surface of Titan before we landed a probe there. They were quite wrong. So were a great many of the prevaling theories about Mars before we send probes there.

Early Universe ideas? Not fact. Not "well-known". Guesses.

Humans have made bad models from guesswork fit perfectly in the past, there were very orderly models of the geocentric model of the universe that accounted for the movement of Venus and Jupiter, etc quite well. http://en.wikipedia.org/wiki/G...

Re:We Really Don't

[jandersen]

This is the comic book version of what happened.

Well, it seems to be simply a high-school essay with glossy graphics; what did you expect? It doesn't look like Stephen Hawking's style, or even Brian Cox' - it's just some guy that's mighty pleased with his ability to make his website look like an issue of the Hello magazine and who's out to attract traffic to his site, that's all.

Because "science" --- the one with hypothesis, testing, reproduction of results is different than the speculation one --- which is very often quite wrong.

Well, in a sense we know that science is ALWAYS wrong - we propose a theory, and if its predictions survive comprehensive testing, it is accepted as being not far off the mark, but we know that is it not the final truth. The scientific method has arisen on this background as a way to make the discrepancy between theory and reality ever smaller.

Re:We Really Don't

[stjobe]

Early Universe ideas? Not fact. Not "well-known". Guesses.

That's... really selling science - and the scientific method - way short.

It's not "guesses", it's hypotheses, which are by their nature our best explanations of something given our current understanding of how those things work.

Calling these "guesses" reduces all the science that's actually going on and puts it on the same level as Joe Schmoe's wild-ass guessing on subjects he's not familiar with.

There is a world of difference between Joe guessing what happened in the early days of the universe and a scientist that has devoted several years of his life studying the matter putting forth a hypothesis of what happened.

Please don't paint these as the same thing, it's just doing the anti-science folk a service, and the rest of us a disservice.

Re:We Really Don't

[AchilleTalon]

Well, the guy didn't claim at any point he is telling the Truth, with a capital T. He is telling what we know today with the knowledge we have and the understanding we have of the physical world. Of course, to a certain extent we have no facts about the early universe (first fraction of a second), however we know how matter behaves at temperatures near these fraction of a second. We know how the cooling affect the matter. We know the universe is cooling, we know about thermodynamics, etc. So, even if it is guesswork, it is pretty much on tracks. You cannot reverse the order like you seem to think, there is no way to link these events in another order.

Re:We Really Don't

[stjobe]

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.

Re:We Really Don't

[Ken D]

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.

Re:We Really Don't

[Anonymous Coward]

We don't need to scheme and manipulate to make sure our presentation of science leaves them on the poorest footing to rebut us, because, unless they are using science, their rebuttal is irrelevant.

As long as you think it is a priority for scientists to inform the public of their work, then it is necessary to some degree to address rebuttals regardless of the source of the claims. Such rebuttals become quite relevant in the minds of people who are not familiar enough with what is going on to tell the difference, especially with enough publicity. The only place it becomes completely irrelevant is if scientists should only communicate among their own spheres and journals and have no obligation to explain things to anyone outside of that.

It is the same as educating a single person, in the sense you need to adapt to their previous exposure and ideas. If trying to teach someone about black hole research who has a picture in their head of black holes that is way off, that has to be addressed regardless of if that picture has a scientific origin or not.

Re:We Really Don't

[Jason Levine]

It might seem like nitpicking, but "guess" to me always implies taking a stab in the dark with little to no evidence and ending there. A scientific hypothesis, meanwhile, usually starts with some data, builds an argument that X should be true because of the initial data, and is subjected to testing to either confirm it or disprove it.

To give an example, you are presented with a clear cube filled with gumballs. A guess would be glancing at it and saying "600?" A hypothesis would be measuring the sides, estimating the size of each gumball, figuring out that there should be 1,000 gumballs, and then opening up the cube and counting the gumballs.

Re:We Really Don't

[Ol Olsoc]

The thing is our knowledge of the universe is so infinitesimally small that really it would be far fairer to call it a guess than a Hypothesis.

How do you know it is "infinitesimally small"?

That's sound bite cosmology. We don't ever know what we don't know.

The idea that there are certain types of stars that have certain compositions, and certain sizes and will likely have a lifespan of a certain number of years is a theory that has worked pretty well. We add to it when we find something that doesn't quite fit, and we modify to it as needed. Wanna see scientists get excited? When something doesn't fit, and they have to go back to figure out why. That's a happy scientist. Wouldn't be a happy politician or theologian though

But we do know some things about the universe. We'll never know it all, thank goodness, but a lot of physics pieces are falling into place.

Bullshit

[Anonymous Coward]

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.

Re:Bullshit

[Ken D]

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.

Re:Bullshit

[Anonymous Coward]

I know I'm probably feeding the trolls here but...

Fine. I'm a post-doctoral research associate working on inflationary model fitting comparing anisotropies in the power spectrum with the anisotropies of galaxy distribution, with a side interest in the formation of stars at redshifts of about 5. In my time here I've done a host of jobs from outreach to 14-18 year olds, fundamental research, presentation to international conferences. And I've also cleaned the toilets twice, so yeah, I guess janitor could be on my CV too, if you care about that kind of thing (our janitors, for the record, are actually remarkably nice people, far more cheerful that I would be if I had their job, but I guess they only deal with literal shit that you can flush away, not the metaphorical shit that morons post on the internet).

The link to XKCD, if you know what you're talking about (which I strongly suspect that you don't) is a fit of a black body spectrum to the CMB. The point is that the data matches to such an amazing degree. The whole point of that comic is to state that our models work. They work incredibly well, far better in fact, than most of us would have thought when we first posited them.

The other links were just the beginnings of what is a very long list of ways we've tested our models against reality. I'm not your google guide - look them up yourself. What you'll find is that we see across a host of observations from different teams, different equipment, different phenomena covered that the predictions line up with observations to a very very high degree. The final result, as posited by the webcomic you so like to deride, is the tag line to that comic.

It works, bitches.