Sunday, December 25, 2011

Boy of Age 16 Asks Me about Relativity, etc.
2. Einstein and Black Holes

Albert Einstein during a lecture in Vienna in 1921.
By Ferdinand Schmutzer [Public domain],
via Wikimedia Commons.

A friend of mine on Twitter, Aaron (a pseudonym), is an overseas, 16-year old boy, who seriously admires Albert Einstein and wants to become a physicist. He continually writes me (Ted, also a pseudonym) questions about the theory of relativity and related topics, and I am sending answers. In this series of blog posts, those questions and answers are reproduced with modifications. I am not an expert in the fields of physics related to relativity. So, my answers might contain errors. If you find any error, please do not hesitate to write a comment for the benefit of the boy and me as well as that of other readers.

Aaron: I read in some books that Einstein did not believe in black holes. Then, why did he publish the work of general relativity that predicted black holes?

Ted: When he developed the theory, Albert Einstein did not notice that it would predict the existence of black holes. Only after the publication of the paper on general relativity, other physicists studied solutions of Einstein field equations to find the possible existence of black holes. (For the detailed history of finding black hole solutions, see Ref. 1.)

Einstein's disbelief in the black hole solution is explained in Ref. 2 as follows:
It seems that Einstein always was of the opinion that singularities in classical field theory are intolerable. They are intolerable from the point of view of classical field theory because a singular region represents a breakdown of the postulated laws of nature. I think one can turn this argument around and say that a theory that involves singularities and involves them unavoidably, moreover, carries within itself the seeds of its own destruction.
In other words, Einstein's belief in his own theory combined with his opinion about physical theories in general did not allow the existence of the black hole. However, his theory was cleverer than his opinion and predicted what was confirmed by (indirect) observations. A physical theory or an equation can sometimes be more reliable than the philosophical opinion even of the greatest man.

References
  1. "Section 1. History" in "Black hole", Wikipedia, The Free Encyclopedia (19 December 2011 at 11:28).
  2. Quoted in Philosophical Problems of the Internal and External Worlds: Essays on the Phylosophy of Adolf Gr├╝nbaum edited by John Earman (University of Pittsburgh Press, 1993), as written by Peter Bergmann (1980, 156).

(Originally written on February 21, 2011)

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