Physics stories ⚛️ Dirac, the large numbers, and two anecdotes The physicist Dirac, pioneer of quantum theory, discoverer of the Dirac equation and Nobel Prize winner, pointed out the following remarkable facts in 1937: 1/10 - ThreadSky

gernot-muenster.bsky.social • 42 days ago

Physics stories ⚛️

Dirac, the large numbers, and two anecdotes

The physicist Dirac, pioneer of quantum theory, discoverer of the Dirac equation and Nobel Prize winner, pointed out the following remarkable facts in 1937:

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gernot-muenster.bsky.social•42 days ago

1. The age of the universe divided by a typical atomic time scale is approximately 10^40 (a 1 with 40 zeros). The exact value doesn't matter here; it's about the order of magnitude.

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gernot-muenster.bsky.social•42 days ago

2. The gravitational force between the proton and electron, divided by their electrical attractive force, is approximately 10^(-40).

3. The total mass contained in the universe divided by the proton mass is approximately 10^80.

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gernot-muenster.bsky.social•42 days ago

This led him to two hypotheses:

I. The "gravitational constant" is not constant, but decreases inversely proportional to the age of the universe.

II. The total mass in the universe grows proportionally to the square of time.

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gernot-muenster.bsky.social•42 days ago

Pascual Jordan took up these hypotheses and proposed modifications of Einstein's general theory of relativity that fit Dirac's hypotheses. He also postulated that the Earth has expanded over the course of Earth's history due to decreasing gravity.

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gernot-muenster.bsky.social•42 days ago

Anecdote 1: When Wolfgang Pauli heard of Jordan's theory that the mass of the universe increases quadratically with time, he commented on it with regard to Jordan's ever-increasing corpulence with the remark that it was pure anthropomorphism: Jordan was projecting his own development onto space.

gernot-muenster.bsky.social•42 days ago

Anecdote 2: In the 1950s, the physicist and philosopher Carl Friedrich von Weizsäcker proposed a theory of the universe that is based on so-called quantum theoretical "ur-alternatives". An alternative is a yes-no question.

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