“We all want progress, but if you’re on the wrong road, progress means doing an about-turn and walking back to the right road; in that case, the man who turns back soonest is the most progressive.” –C. S. Lewis
Many of you are a little bit skeptical that I talk about things like the History of the Universe, Inflation, Dark Matter and Dark Energy like they are absolute certainties. After all, isn’t it true that there are an awful lot of assumptions that we make in order for these things to be true?
That’s right, I admit it. We make assumptions when we come up with these theories and pictures of how nature and the Universe themselves work.
And if these assumptions turn out to be wrong or invalid, well, our theories will…
And some of them, no doubt, will. Someday.
And perhaps there will be some great new discovery that invalidates one of the assumptions that went into it.
After all, it was Albert Einstein himself who said,
No amount of experimentation can ever prove me right; a single experiment can prove me wrong.
And that’s true! If general relativity turns out to be wrong on large scales, maybe we actually are misinterpreting all of this data.
But with the assumption that general relativity is correct, we get a whole suite of evidence that all points to dark matter.
We have precision measurements of the fluctuations in the cosmic microwave background. They occur on all observable scales at very particular magnitudes, consistent with a Universe with about 5 times more dark matter than normal matter, and not with any dark-matter-free alternatives.
(Yes, we have the assumption that in addition to general relativity being correct, the Big Bang description of the early Universe is also correct. Of course, that’s another well-founded assumption, but an assumption nonetheless.)
And the same story holds when we look at the local, large-scale clustering of galaxies! We need dark matter to make our observations match up with our predictions and simulations.
There is a plethora of other data sources we can use to test whether the Universe needs dark matter or not (that I won’t go into the details of), such as peculiar velocities of interacting galaxy pairs, baryon acoustic oscillations at high redshifts, X-ray observations of galaxy clusters, Big Bang nucleosynthesis (which limits the amount of normal matter), and the most common (but not the best) argument, the observed rotations of individual galaxies. And when you take it all together, each individual argument is not only strong enough to indicate the presence of dark matter, but gives the same quantitative abundance of dark matter.
In other words, we put the puzzle together, and despite the fact that we’re missing a piece or two, we have an extremely clear and compelling picture.
It could, however, all be wrong. It would take some extraordinary evidence to change what is presently an overwhelming scientific consensus, but it could happen. After all, the ability to challenge your assumptions, assimilate new evidence and look as objectively as possible is what makes you a good scientist.
And I do my best to explain to you what we know and how we know it, and why certain theories and ideas are superior to others. In areas of the Big Bang, dark matter, and theoretical cosmology, I am an expert.
I’m not the only expert; I’m not even the best expert in any of those areas. But very few among you out there would dare to tell me that I — and everyone in my field — was an incompetent fool who’s misreading all of the data and putting it together in this misleading way, just to promote my own Big Bang / dark matter ideology.
Now, I’m not an expert on evolution. (As you can see.) Quite to the contrary, I have the biology education of about a college junior. But just as surely as I know that the Big Bang is an excellent, valid, useful and — as far as we can tell — true scientific description of the Universe, Evolution — with natural selection as its mechanism of operation — is an excellent, valid, useful, and true scientific explanation for the diversity and development of life on Earth.
Perhaps naively, I think I have a pretty good understanding of how it works, but I recognize that — in this arena — I am not an expert. But the overwhelming majority of biologists accept evolution via natural selection as the best explanation for a compelling suite of biological phenomena, and it would be incredibly insulting and arrogant of me to believe that I — with my lack of knowledge and education — knew better than the experts.
So why do so many people do exactly this when it comes to climate science?
I was shocked — absolutely shocked — by the huge discussion that took place on my one post this year on climate change and global warming: over 350 comments! And so many of them simply dismissed the scientific consensus.
And make no mistake about it: there is an overwhelming scientific consensus in favor of anthropogenic (human-caused) global warming. From wikipedia:
No scientific body of national or international standing has maintained a dissenting opinion; the last was the American Association of Petroleum Geologists, which in 2007 updated its 1999 statement rejecting the likelihood of human influence on recent climate…
I’ve had people with no scientific training lecture me about the astrophysical causes of global warming (!), like somehow nobody’s thought of testing that hypothesis.
Let me tell you something personal.
But — apparently — I’m very unusual. I like it when I’m wrong. Instead of being the teacher, it gives me an opportunity to learn something new. It gives me a chance to improve myself and my understanding of things. It often connects me, intellectually, with a new point of view and a new set of (usually, quite admirable) people.
If you cannot be wrong, you cannot learn. And if you think that nobody else can do anything right, you are missing out on learning about everything that you yourself are not an expert in, which is most things.
So there was a lot of information here, and you probably have a lot of thoughts and opinions, and I want to hear it. Those of you who don’t trust any (or all?) of the “consensus” ideas put forth here, why don’t you? Those of you who think you know better than the experts in these fields, why do you? And those of you who think I’ve got it right today, don’t just lurk; share a story of a time when you learned something!
Because science could have it all wrong. But if it does, scientists studying it are likely going to be the ones who find the mistakes, make the corrections, and push us ahead in our understanding of the Universe.