Why the theories of Einstein, climate change or evolution can never be proved right
Timothy Wotherspoon says the nature of scientific inquiry means that a theory is only as correct as the result of its last experiment – thus ensuring a truly open-minded quest
There have been many headlines over the past week excitedly announcing that scientists at the Laser Interferometer Gravitational-Wave Observatory (Ligo) have detected microscopic undulations in the fabric of space-time caused by gravitational waves sent off from two black holes colliding 1.3 billion light-years from earth. Newspapers around the world reported that the much-anticipated announcement showed that the “100-year journey to prove Einstein’s theory” had finally come to an end. Gravitational waves are predicted by Einstein’s theory of general relativity. Although many predictions have long been observed, gravitational waves had proved elusive.
As a physicist, I am always glad to see public interest in science, but headlines such as “Theory of Einstein’s Proved Right – Again” (Wall Street Journal) give me pause, in no small part because this one appeared three years ago in reference to an entirely different experiment.
Scientific news followers may also recall that, in March 2014, scientists at the Bicep2 telescope near the South Pole reported the detection of gravitational waves in the form of a primordial artefact of the Big Bang. Careful readers may be confused not as to what exactly is general relativity, but how they can be detected for the first time twice in a two-year span and how both of them finally “prove Einstein correct”?
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Ligo co-founders and physicists Rainer Weiss (left) and Kip Thorne embrace as they announce their discovery, observing the ripples in the fabric of space-time called gravitational waves, in Washington this month. Photo: AFP
When scientific breakthroughs are announced, the scientific community reacts with both celebration and scepticism. If other scientists can’t reproduce similar outcomes with similar experiments, then something has gone awry. This is what happened to the results announced by the Bicep2 experiment. By early 2015, it was shown that the signal that they detected could not be isolated from the effect of interstellar dust, confounding their findings. The result had to be discarded. Some might find this disappointing, but it demonstrates the greatest power of the scientific method – knowing when you’re wrong.
When scientific breakthroughs are announced, the scientific community reacts with both celebration and scepticism
Einstein’s theory will never be proven correct. No scientific theory ever will be. Anyone who tells you differently does not understand the scientific method. As the late physicist Richard Feynman once eloquently explained, “We can always prove any definite theory wrong. Notice, however, we can never prove it right. Suppose that you invent a good guess, calculate the consequences, discover that every consequence you calculate agrees with experiment. The theory is proved right? No. It is simply not proved wrong.”
