Section 3–5 Geology

(The conditions of air / Mountain-forming processes / Earth’s interior)

Feynman opines that physicists have not worked out a satisfactory theory of meteorology and they have been unable to get a good theory as to how dense a substance should be at the pressures that would be expected at the center of the earth. In this section, the three interesting ideas discussed are the conditions of air, mountain-forming processes, and earth’s interior.

1. The conditions of air:

“… So if we know the condition of air today, why can’t we figure out the condition of the air tomorrow? (Feynman et al., 1963, section 3.5 Geology).”

According to Feynman, one problem of meteorology is that the motion of air is rather complex and the condition of air can be very sensitive as well as unstable. The meaning of unstable condition can be illustrated by two water molecules that are initially beside each other and how they may be widely separated after flowing for some time. In other words, two initial similar conditions may result in two significantly different final conditions even in a smooth flow of water. Furthermore, physicists are unable to predict the size of the lumps of water and exactly how they will continue to flow. Similarly, a smooth flow of air molecules going over a mountain may result in a turbulent flow, complex whirlpools, and eddies.

Some meteorologists might argue that Feynman was pessimistic because he only discusses the “chaos in order” and omits the “order in chaos.” Currently, they agree that a climatic system is deterministic and predictable in principle, but it is unpredictable in practice. That is, meteorologists have a better understanding of chaos theory and are able to develop better weather-prediction models with the help of powerful computers and satellite images. Interestingly, Albert Hibbs, under the supervision of Feynman, completed a Ph.D. thesis titled “The growth of water waves due to the action of the wind” in 1955. Perhaps Feynman would have a different opinion of “butterfly effect”: a tornado could be related to the butterfly diagram of the sun (that is farther away) instead of a butterfly in Brazil (that is nearer)?

Note: Ilya Prigogine is a Belgian scientist that opines that chaos can give rise to order. In his Nobel lecture, Prigogine (1977) explains that “in a town, in a living system, we have a quite different type of functional order. To obtain a thermodynamic theory for this type of structure we have to show that that non-equilibrium may be a source of order. Irreversible processes may lead to a new type of dynamic states of matter which I have called ‘dissipative structures’ (p. 263).” He received a Nobel Prize in Chemistry in 1977 for his research in non-equilibrium thermodynamics, particularly the theory of dissipative structures.

2. Mountain-forming processes:

“…You will find, if you study geology, that there are mountain-forming processes and volcanism, which nobody understands but which is half of geology (Feynman et al., 1963, section 3.5 Geology).”

Feynman suggests that most geological processes are in front of our eyes, for example, the erosion processes of the rivers, directions of winds, and mountain-forming processes. However, he believes that nobody understands mountain-forming processes and volcanism, which is half of geology. In addition, the cause of an earthquake is not well understood. Simply phrased, geologists understand that something is pushing something else, it snaps and will slide, but it is unclear what pushes, and why? Feynman explains circulating currents inside the earth, due to the temperature difference inside and outside, push the surface of the earth slightly. If there are two opposite circulations next to each other, some matter will be collected in the region where they meet and cause belts of mountains which are in stressed conditions, and it may further result in volcanoes and earthquakes.

Geologists may criticize this section of his lecture because Feynman did not specify the theory of continental drift and explain how earthquakes could be caused by movements of plate tectonics. (If you listen to the audio CD of this lecture, Feynman mentions “tectonics” and says that nobody understands tectonics.) Plate tectonics is the unifying theory of geology which provides explanations of geographical phenomena such as earthquakes and volcanoes. This ground-breaking theory (pun unintended) describes how the lithosphere of the Earth is broken into various plates. Roughly speaking, the plates are of the order of 100 kilometers thick and are constantly moving towards, away from, or past each other.”

3. Earth’s interior:

“… What about the inside of the earth? A great deal is known about the speed of earthquake waves through the earth and the density of distribution of the earth (Feynman et al., 1963, section 3.5 Geology).”

Feynman elaborates that geologists have some knowledge of earthquake waves through the earth, but physicists do not have a good theory of density of a substance with respect to the pressures at the center of the earth. Essentially, the mathematics involved is difficult, but someone may realize this is an important problem and it could be solved soon. Another problem is that even if we know the density of the substance in the earth’s interior, it is difficult to figure out the circulating currents (or circulating electric current within the iron core). Geologists generally agree that circulating currents in Earth’s iron core generate changing magnetic fields.

Geophysicists are studying anomalies in the gravitational field which are due to distributions of masses or minerals within the earth. In general, geodynamical processes such as mountain forming and convective motions in the earth have changed the mass distribution within the earth that result in changing gravitational attraction. Current understanding in geophysics is accelerated by inventions of sensitive gravity meters that can measure tiny changes in the earth’s gravitational field. Furthermore, sensitive magnetometers can measure tiny changes in the earth’s magnetic field that may be caused by flowing oil. Thus, it has important implications for oil industries and future economy.

Note: In his Nobel Lecture, Willard Frank Libby (1960) says that “[r]adiocarbon dating had its origin in a study of the possible effects that cosmic rays might have on the earth and in the earth’s atmosphere (p. 593).” Libby was awarded Nobel prize in Chemistry in 1960 for the development of radiocarbon dating method in using carbon-14 for age determination in archaeology, geology, geophysics, and other branches of science. For example, archaeologists can measure the amount of carbon-14 compared to the stable isotope carbon-12 and determine the age of an item. Nevertheless, Feynman could have discussed whether atoms in the earth’s atmosphere are exactly of the same kind as atoms at the center of the earth.

Questions for discussion:

1. Can meteorologists determine the exact conditions of air today such that they can predict the future conditions of air?

2. Do you agree with the theory in which there are currents inside the earth—circulating currents, due to the difference in temperature inside and outside—which, moving towards, away from, or past each other?

3. Do we know much less about earth’s interior than the conditions of matter in the stars?

The moral of the lesson: we cannot predict the future conditions (temperature, pressure, and velocity) of air because of the limitations of meteorological instruments as well as our limited knowledge of current conditions of air.

References:

1. Feynman, R. P., Leighton, R. B., & Sands, M. (1963). The Feynman Lectures on Physics, Vol I: Mainly mechanics, radiation, and heat. Reading, MA: Addison-Wesley.

2. Libby, W. F. (1960). Radiocarbon dating. In Nobel Lectures in Chemistry 1942 – 1962. Singapore: World Scientific.

3. Prigogine, I. (1977). Time, structure, and fluctuations. In Nobel Lectures in Chemistry 1971 – 1980. Singapore: World Scientific.