Astrobiology and the Relation of Fundamental Physics to Life

Abstract

How come that human beings are here on Earth today? How did the laws of physics made it possible that intelligent life evolved? Are we unique, or are we just one of many intelligent species populating the Universe? It is likely that in the vastness of the Universe we humans do not stand alone; in the near future we might be within reach of other civilizations, and we must understand how to identify them, and how to communicate with them. At the basis of all this is understanding what is life, and how it emerged on Earth and maybe elsewhere. The answer to these questions is written in the language of physics.

How come that human beings are here on Earth today? How did the laws of physics made it possible that intelligent life evolved? Are we unique, or are we just one of many intelligent species populating the Universe? It is likely that in the vastness of the Universe we humans do not stand alone; in the near future we might be within reach of other civilizations, and we must understand how to identify them, and how to communicate with them. At the basis of all this is understanding what is life, and how it emerged on Earth and maybe elsewhere. The answer to these questions is written in the language of physics.

Appendices

Further Reading

 

• [F11.1] L. Dartnell, “Life in the Universe”, Oneworld 2007.

• [F11.2] J. Chela-Flores, “The science of astrobiology”, Springer 2011.

• [F11.3] W.T. Sullivan and J.A. Baross (eds.), “Planets and Life: The Emerging Science of Astrobiology”, Cambridge University Press 2007.

 

Exercises

 

• 1. The mass of the Moon is about 1/81 of the Earth’s mass, and the mass of the Sun is 333,000 times the Earth’s mass. The average Sun-Earth distance is 150 $\times 10^6$ km, while the average Moon–Earth distance is 0.38 $\times 10^6$ km (computed from center to center).

  • (a) What is the ratio between the gravitational forces by the Moon and by the Sun?

  • (b) What is the ratio between the tidal forces (i.e., between the differences of the forces at two opposite sides of the Earth along the line joining the two bodies)?

• 2. What is the maximum temperature for which the Earth could trap an atmosphere containing molecular oxygen O$_2$?

• 3. Assuming that the Sun is a blackbody emitting at a temperature of 6000 K (approximately the temperature of the photosphere), what is the temperature of Earth at equilibrium due to the radiation exchange with the Sun? Assume the Sun’s radius to be 7000 km, i.e., 110 times the Earth’s radius.