The logic of science-13: How ‘good sense’ emerges in science

(For other posts in this series, see here.)

The philosopher of science Pierre Duhem said in his book The Aim and Structure of Physical Theory (1906, translated by Philip P. Wiener, 1954) that despite the fact that there is no way to isolate any given theory from all other theories, scientists are saved from sterile discussions about which theory is best because the collective ‘good sense’ of the scientific community can arrive at verdicts based on the evidence, and these verdicts are widely accepted. In adjudicating the truth or falsity of theories this way, the community of scientists are like a panel of judges in a court case (or a panel of doctors dealing with a particularly baffling set of symptoms), weighing the evidence for and against before pronouncing a verdict, once again showing the similarities of scientific conclusions to legal verdicts. And like judges, we have to try to leave our personal preferences at the door, which, as Duhem pointed out, is not always easy to do.
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Tests of the existence of other universes

When Louis de Broglie first proposed in 1924 that particles had wavelike properties, the technological challenges to investigating the idea were so immense that the prospects for testing it seemed to lie very far into the distant future, if at all. But one of the features of science is that however incredible an idea may seem when it is first proposed, if it gains credibility and acceptance from the scientific community as a whole, it will only be a matter of time before someone finds an ingenious way to try and test it. So it was with de Broglie’s idea. It was such so beautiful in the way that it unified waves and particles in a symmetric way in quantum mechanics, that it spurred creative thinking and within just three years C. J. Davisson and L. Germer were able to construct an experiment that confirmed it, resulting in de Broglie receiving the Nobel Prize in 1929, an incredibly rapid pace of advance.

So it is with the multiverse idea, that entire universes can be created spontaneously from the vacuum and thus our own universe may be just one of an enormous number (as many as 10500) of universes, each having their own laws and structure. This idea not only does not violate the laws of science, it is not even a new theory, being in fact a prediction of other theories.

As with de Broglie’s hypothesis, when the multiverse idea was initially proposed there seemed to be no way to test it. But now people have come along with suggestions of how to do it, by looking for disk-like patterns in the cosmic microwave background that may be the telltale relics of collisions of other universes with our own.

Science is such fun.

Radioactive heating of the Earth

Recent measurements show that about half of the 40 trillion watts of heat radiated continuously by the Earth comes from radioactivity taking place in its mantle and crust, while the remainder is due to the primordial heat that was created at the formation of the Earth and is located mainly in the core.

Historians of science are aware of the importance of the discovery of the radioactivity as an ongoing source of the heating of the Earth. Before the immense amount of heat associated with radioactive decay was discovered around 1903, physicists like Lord Kelvin had calculated the age of the Earth by treating it as an initially hot body that was steadily cooling. They concluded that it could not be older than 100 million years and could be as low as 20 million years. This made it very difficult, if not impossible, for the theory of evolution by natural selection, because it was a slow process that required long time scales. This was seized upon by religious people to argue against the evolution and in favor of the special creation of species by god. (See my series on the age of the Earth for a more detailed discussion of this.)

The discovery of radioactivity had two revolutionary impacts. It created an awareness that radioactivity was an ongoing source of the heating of the Earth that undermined all the earlier calculations of Kelvin and others, and it provided an important new tool for measuring time that opened the gates to new discoveries that rapidly pushed the age of the Earth to more than four billion years, giving plenty of time for evolution to take place.

The logic of science-12: The reasoned consensus judgment of science

(For other posts in this series, see here.)

The previous post illustrated a crucial difference between science and religion that explains why scientists can resolve disagreements amongst themselves as to which theory should be considered true but religious people cannot agree as to which god is the one true god. In competition between scientific theories, after some time the weight of evidence is such that one side concedes that their theory should be rejected, resulting in a consensus verdict. In religion, since evidence plays no role, and reason and logic are invoked only when they support your own case and discarded by appealing to faith when reason goes against you, there is no basis for arriving at agreement. It would be unthinkable for a scientist to argue in favor of his or her theory by denying evidence and logic and telling people that they must have faith in the theory for it to work.
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Is there anything that makes humans special?

Primatologist Frans de Waal’s latest book The Age of Empathy (2009) argues against the idea that we humans have some special quality that separates us from all the other animals. Some people, especially those who are religious, seem to be very reluctant to accept that idea that other animal species share pretty much all the same basic physical and emotional characteristics that we humans have.

There is an interesting passage in the book (p. 206-208) where he says that this wrong idea in Christianity, Judaism, and Islam originated because the part of the world in which those religions originated were those that did not contain our closest non-human relatives.
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The logic of science-11: The problem with falsification

(For other posts in this series, see here.)

In the previous post, I discussed Karl Popper’s idea of using falsification as a demarcation criterion to distinguish science from non-science. The basic idea is that for a theory to be considered scientific, it has to make risky predictions that have the potential that a negative result would require us to abandon the theory. i.e., declare it to be false. If you cannot specify a test with the potential that a negative result would be fatal to your theory, then according to Popper’s criterion, that theory is not scientific.

Of course, I showed that falsification cannot be used to identify true theories by eliminating all false alternatives, because there is no limit to the theories can be invented to explain any set of phenomena. But steadily eliminating more and more false theories surely has to be a good thing in its own right. This is why falsificationism is highly popular among working scientists because it enables them to claim that science progresses by closing down blind alleys.
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The logic of science-10: Can scientific theories be proven false?

(For other posts in this series, see here.)

In the previous post in this series, I wrote about the fact that however much data may support a theory, we are not in a position to unequivocally state that we have proven the theory to be true. But what if the prediction disagrees with the data? Surely then we can say something definite, that the theory is false?

The philosopher of science Karl Popper, who was deeply interested in the question of how to distinguish science from non-science, used this idea to develop his notion of falsifiability. He suggested that what makes a theory scientific was that it should make predictions that can be tested, saying that “the criterion of the scientific status of a theory is its falsifiability, or refutability, or testability.” (Conjectures and Refutations: The Growth of Scientific Knowledge, 1963, p. 48)
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The logic of science-9: Can scientific theories be proven true?

(For other posts in this series, see here.)

In mathematics, the standard method of proving something is to start with the axioms and then apply the rules of logic to arrive at a theorem. In science, the parallel exercise is to start with a basic theory that consists of a set of fundamental entities and the laws or principles that are assumed to apply to them (all of which serve as the scientific analogues of axioms) and then apply the rules of logic and the techniques of mathematics to arrive at conclusions. For example, in physics one might start with the Schrodinger equation and the laws of electrodynamics and a system consisting of a proton and electron having specific properties (mass, electric charge, and so on) and use mathematics to arrive at properties of the hydrogen atom, such as its energy levels, emission and absorption spectra, chemical properties, etc. In biology, one might start with the theory of evolution by natural selection and see how it applies to a given set of entities such as genes, cells, or larger organisms.< [Read more…]

How yogis ‘levitate’

Hindu mystics have long been claiming that they can, by sheer will and/or the intervention of god, levitate off the ground. Here is one way it is done.

A good rule of thumb is that if something violates the laws of science, it is not a miracle, it is not by ‘harnessing the energy field’ or some such Deepak Chopraesque mumbo-jumbo, and it is not due to a god. It is merely a trick. The only question to be explored is how the trick is carried out.

The logic of science-8: The power of universal claims in science

(For other posts in this series, see here.)

In the previous post in this series, I argued that in the case of an existence claim, the burden of proof is upon the person making the assertion. In the absence of a preponderance of evidence in its favor, the claim can be dismissed. As has often been said, “What can be asserted without proof can be dismissed without proof”. The basis for this stance is the practical one that proving the non-existence of an entity (except in very limited circumstances) is impossible. Hence if we do NOT have a preponderance of evidence in favor of the existence of an entity, we conclude that it is not there.

In the case of a universal claim, however, the situation is reversed and the default position is that the claim is assumed to be true unless evidence is provided that refutes it. So in this case, the burden of proof is on the person disputing the assertion, again for eminently practical reasons.
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