Life and our galactic location (Part 2)

The Israeli-American Gerald L. Schroeder, an Orthodox Jew who earned his B.Sc., his M.Sc., and his Ph.D. in nuclear physics and in earth and planetary sciences at the Massachusetts Institute of Technology (MIT), is one of the most interesting contemporary writers on science and religion.  He is a professor at Jerusalem’s College of Jewish Studies.

Here, drawn from his book God According to God: A Scientist Discovers We’ve Been Wrong About God All Along (New York: HarperOne, 2009), is the second part of a passage about our rather special location in a quite congenial galaxy:

Spiral galaxies are fit for life because spiral galaxies provide a range of conditions among which are those optimal for nurturing life.  The spiral structure offers a variety of stellar concentrations throughout, from high densities near the galactic center and within the spiral arms to very much lower densities of stars in the spaces between the arms.  Depending upon how the outer limit of the Milky Way is defined, the diameter of our galaxy is between 80,000 and 100,000 light-years.  Our sun likes between two spiral arms, some 27,000 light-years, or approximately two-thirds of the way, out from the Milky Way’s center.  Relative to the thickness of the Milky Way’s galactic disk, the solar system is just above (or below, depending upon one’s orientation) the center of the 6,000-light-year-thick central plane.

The earth revolves around the sun at approximately 30 kilometers per second.  The sun and the solar system revolve around the center of the Milky Way at some ten times that speed.  All revolutions are in the same direction.  A deep challenge remains to discover why all components of the universe revolve or rotate.  Angular momentum, as the forces of rotation are categorized, is always conserved unless acted upon by an outside force.  What force acted to induce the rotations observed is an unsolved puzzle.  A universe without rotation would mean a universe without planets and without life.  All solids and gases would be gravitationally drawn directly into the parent star rather than revolving around the parent star.  (64-65)

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Big changes seem to be coming for one of our continents:

“Crack in East African Rift Valley Is Evidence of Continent Splitting”

“The Sahara Desert is Expanding: New UMD study finds that the world’s largest desert grew by 10 percent since 1920, due in part to climate change”

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I’ve posted about this subject before:

“Meet TESS, the satellite that will find thousands of planets”

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And this is interesting, too:

“What’s sending mysterious repeating fast radio bursts in space?”