From a reply to a comment on treehugger on 6/1/10

As a card carrying  scientist (PhD Harvard Physics) you are quite right that science does not work by consensus. One insight by Einstein is worth a thousand opinions by run-of-the mill PhDs, let alone a million un-informed but passionate lay comments regarding “common sense”. You can’t overturn conservation of energy by majority vote…

BUT, after the initial insight, consensus DOES eventually matter. There is a natural ebb and flow in science, carrying new ideas from hypothesis to fact. Any competent  scientist can “feel” the quality of the debate  and judge if both sides are converging on a new insight, or if the hypothesis is unraveling and doomed to the rubbish bin of failed ideas.

Consider these two concrete examples: In 1989 Pons and Fleischmann proposed that electrochemical cells could initiate fusion at room temperature. World changing if true, and skepticism (and hope) were rampant. Within weeks, experts in every field- with much stronger technical abilities and experience than P&F in everything from nuclear physics to thermodynamics, tried to repeat and extend their initial findings. But they concluded the initial experiments were flawed, and the proposal baseless. While a few groups still muddle around the fringes of cold fusion, consensus (by action and experiment, not by mere opinion) rules the day.

On the other hand, in 1986 Müller and Bednorz at IBM in Switzerland claimed, based on some rather indirect measurements, that they had discovered the route to a new, higher temperature superconductor.  A surprising assertion in light of the informal consensus that superconducting temperatures were doomed to plateau at around 16K- where they had languished for a decade.  But within months Japanese material scientists, after reading their work,  quickly doubled the world record superconducting temperature to 30k. Weeks later, experts in every field- with much stronger technical skill and experience than M&B and the Japanese in everything from materials to thermodynamics tried to repeat and extend their initial findings. Amazingly, these other groups were not only able to reproduce the initial findings, but doubled the temperature limit AGAIN, and years later, AGAIN. Eventually leading to a Noble prize.

It is very rare that an entirely new concept can upset the last hundred years of scientific progress. Modern science is accretive- built by millions of smart people, with often independent approaches, and the edifice is bound together by a mesh of interlocking cross-checks. The germ theory of disease overthrew thousands of years of superstition, but since then, new findings about viruses and epigenetics only enhance Pasteur’s insights. They don’t overturn his great discovery. Einstein’s Law of General Relativity is an improvement on Newton’s Law of Gravity, not a repudiation.

So again, consensus eventually matters in the context of scientific progress. But you don’t get to vote, you have to put up the evidence, or shut up.

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See also this article on the scientific method and Darwin's Law of Evolution
And this proposal for a moderated, community-based ranking of scientific truth.