Measuring the Universal Gravitation Constant

Vertical section of Cavendish balance

In 1798, the English physicist and chemist Henry Cavendish was the first to measure Newton's universal gravitational constant (G) using a spectacularly ingenious method, which has been scarcely improved later. The method was devised by John Michell, who died without being able to carry it out, so Cavendish performed the experiment. In fact, his objective was not to measure the constant, but the mass of the Earth, but the value of the constant could be inferred from the result.

Cavendish’s instrument was a torsion balance from which two identical balls of lead hung. Next to these balls, one on one side and one on the other, hung two much larger lead spheres, 175 kg each, which attracted the first two, producing a slight twist of the balance, which Cavendish could observe by means of a small telescope located outside the enclosure, to avoid observer interference. He thus detected a displacement of about 4 mm, which he measured with a precision of ¼ mm. This allowed him to calculate that the density of the Earth is 5.448 times greater than that of water, from which it is possible to deduce the mass of the Earth and the value of G:

G=6.674×10^-11N.m²/kg²

This is the official value, which is known with quite a low accuracy (1 in 10,000), compared with other universal constants.

Science or philosophy

Pierre Teilhard de Chardin

In a previous post, speaking about intelligence, I mentioned that there are four incompatible philosophical theories that try to explain the phenomenon of human consciousness. I summarize them briefly here:

1.     Reductionist monism or biological functionalism: The mind is completely determined by the brain and by the network of neurons that makes it. The human mind is an epiphenomenon. Freedom of choice is an illusion. We are programmed machines.

2.     Emergent monism: The mind is an emergent evolutionary product with self-organization, which has emerged as a complex system from simpler systems made up by neurons. Some argue that the underlying structures cannot completely determine the evolution of the mental phenomena. These, however, would be able to influence the underlying structures.

3.     Neuro-physiologic dualism: Mind and brain are different, but they are so closely connected that they make up a unit, two complementary and unique states of the same organism.

4.     Metaphysical dualism: Mind and brain are two different realities. The first is spiritual and non-spatial, capable of interacting with the brain, which is a material and spatial substance. Both entities can exist independently of one another, although the body without the mind eventually decomposes.

Interview with Manuel Alfonseca in a Spanish Newspaper

On February 23, 2018, a Spanish Newspaper (La Opinión, El Correo de Zamora) published this interview with me, performed by Ana Arias, which I am now translating into English. The interview was re-published a few days later (March 10) in the website ReligionEnLibertad (ReligionInFreedom). This is the translation of the interview:

He took an interest in science since he was quite small, as he says. At age 16 he wrote a book of zoology in two volumes that was never published. Anyway, whenever he has to consult information about some little known animal, he consults his book. "And I can find almost everything there," he adds. Now, at 71, he is an honorary professor at the Autonomous University of Madrid.

He believes in science. And also in God. Under the sponsorship of the Caja Rural Foundation and the Science-Religion University Forum held yesterday at the University College, Manuel Alfonseca gave a lecture about The Faith of Contemporary Atheist Scientists.

What is the faith of those scientists?

That God does not exist.

Cyclic Time and Linear Time

Stephen Hawking

In an article published in 1999, in volume 879 of the Annals of the New York Academy of Sciences, Pier Luigi Luisi speaks about the two traditional models of time that have been considered by traditional philosophy and the mythologies of various historical civilizations. They must not be confused with the two philosophical models originated in the twentieth century, the time A and time B of which I spoke in another post of this blog.

• Cyclical time, predominant in Asian civilizations and the Greco-Roman world until the Christian world view took root there. The origin of this model is evident, for many natural phenomena are cyclical: sunrise and sunset; the phases of the moon; the annual movements of the stars, synchronized with the seasons and with many biological phenomena...
• Linear time, prevailing in the three religions who consider themselves descendants of Abraham: Judaism, Christianity and Islam. Linear time can be compared with the course of the life of a living being, which begins at birth, goes on with changes during a certain period, and ends with death.

What does science say about miracles?

Victor Hugo

In his work Quatrevingt-Treize, a title usually translated as “Ninety-three” (it refers to 1793, the year of the Reign of Terror and the Vendée), Victor Hugo introduces a character named Cimourdain, a former priest who has lost his faith because of science:

Science had demolished his faith; the dogma had vanished in him... He knew everything about science and he knew nothing about life.

Apart from the fact that the second sentence is quite debatable (no one can know everything about science), the first raises the confrontation between science and faith, which began with the Enlightenment and reached its maximum philosophical effect in the nineteenth century, Victor Hugo‘s time. He is probably projecting his prejudices into a historical anachronism.

Conan Doyle’s mistake

Sir Arthur Conan Doyle

Sir Arthur Conan Doyle is famous as the author of the character Sherlock Holmes, the detective who relies on logic to solve the most abstruse cases, as in the famous quote from the story The adventure of the blanched soldier, included in the collection The Case-Book of Sherlock Holmes:

When you have eliminated all that is impossible, then whatever remains, however improbable, must be the truth.

Apart from his mystery books, one of his science fiction novels is also very well known: The Lost World, published in 1912, whose protagonist is Professor Challenger, an unbearable scientist, who also appears in other stories by Doyle. This is the plot of The Lost World:

A group of explorers manages to reach an almost inaccessible mesa, lost in the Amazon rainforest, so isolated that dinosaurs and other extinct animals survive there, as well as two races of humans or primitive pre-humans (Pithecanthropus and Homo sapiens). After they manage to escape and return to England, Challenger gives a lecture about his findings, which nobody takes seriously until he exhibits a specimen of Pterosaur that he managed to take from the mesa in the form of an egg, later incubated.

Irreversible time: illusion, or simplification?

Ilya Prigogine

We know Einstein believed that the passage of time is an illusion. In a letter of condolence he wrote in 1955 he said: ...the distinction between past, present and future is only a stubbornly persistent illusion. To assert this, he relied on the fact that Newton’s equations of gravitation, his own equations of General Relativity, Maxwell’s equations (which apply to electromagnetic waves) and Schrödinger’s equation (which gives the wave function of a particle in quantum mechanics) are all symmetric with respect to time.

How then can we explain the fact that it seems so obvious that time goes from the past to the future? Usually, physicists who believe that time is an illusion explain it by saying that, at the microscopic level, time is actually reversible, but when we move to the macroscopic level, new, emerging phenomena appear, one of which is the irreversibility of time. Let's give an example:

According to the usual theories, the movement of the molecules of a gas is perfectly reversible. If we reverse the direction of time, all the particles behave exactly the same and continue colliding with each other, only they would move in the opposite direction. However, when we consider all the trillions of particles that make up a gas, we see irreversible phenomena arising, such as the fact that the gas always tends to occupy as much space as possible, while its accumulation in a corner of the container is much less likely.

The problem is that our physical theories are based on approximations. Mathematics is a very important tool for physics, but in mathematics there are several kinds of very different problems, which differ in their difficulty to be solved. Let us look at a few: