Saturday, November 26, 2016

A Welcome Addition To Basic Astrophysical Literature: "Welcome To The Universe"

Image result for Welcome to the UniverseImage for the news result

As Black Friday dawned yesterday it was almost a certainty that 99 percent of people would be flooding big box stores to snatch up the latest electronic wonders including the new 55"  "Ultra HD" TV sets to make their debuts as Walmart and Best Buy. But a much more sensible option,  as opposed to more electronic titillation,  would have been to invest in Neil De Grasse Tyson's new book, Welcome to the Universe: An Astrophysical Tour.'

The book, a breathtaking overview of astrophysics and especially how we obtain the knowledge we do, is indispensable to getting to know the universe as science knows it   It is distinct from most other basic texts because most of those - as De Grasse Tyson noted on a recent CBS Early Show appearance -  are "a mile wide and an inch deep".  By contrast, this 472 -page book is a "mile wide and a mile deep."  Well, not quite but pretty close and hey, it even includes algebraic equations where necessary - so ignores the old rule that each equation given "decreases sales by one percent" - or some such jabberwocky.

Some of the topics covered include: stellar evolution (the lives and deaths of stars), the search for life in the galaxy, the interstellar medium, the Milky Way, the expansion of the universe, the early universe, quasars and Einstein's special and general theories of relativity. Also: black holes, cosmic strings, inflation and the shape of the universe.

The content actually represents a division of labor between Neil De Grasse Tyson, Michael A. Strauss and J. Richard Gott. For example, the three chapters on special and general relativity were very ably done by Gott.  If you truly wish to get a handle on these abstruse theories there is perhaps no place better then Gott's trio of chapters, so long as you're ok with some intermediate algebra to assist in the task.

Tyson himself is responsible for chapters:  1, 2, 4, 5, 6, 7, 9 and 10. The only one I really had issues with was Chapter 9, 'Why Pluto Is Not A Planet'.   For one thing, Pluto is not specifically an object for astrophysical inquiry but rather planetary astronomy. Hence, the chapter's inclusion can only be attributed to Tyson having already spent a lot of ink on the subject, so why not include it (since it's firmly in his academic 'wheelhouse') in a new book?

But as I noted in previous posts the arguments given don't make any physical sense. For example, Alan Stern, executive director of the Space Science & Engineering Division of the Southwest Research Institute – and Principal Investigator for NASA’s New Horizons mission to Pluto- observed that the new planet definition was “sadly flawed, particularly due to the vagueness of the third condition- clearing the neighborhood around its orbit - which might also disqualify Earth”.

He added: “A lot of people are going to ignore the (new) definition because it doesn’t make sense.” (Source: Eos Transactions of the American Geophysical Union, Vol. 87, 29 August, p. 350). The other aspect is that Pluto’s dethroning was done by a subjective vote at an IAU meeting, not by any objective measures or consistency. The problem is the IAU definition overlooks the neighborhood of the object.  Pluto just happens to be in the Edgeworth –Kuiper belt with thousands of other objects. This is a condition of happenstance, not of actual intrinsic property.

If Earth were to interchange its position with Pluto it would also be in the same belt, and because other substantial objects (e.g. Neptune) crossed its path, it would have to be demoted – by De Grasse Tyson and the IAU's definition. So what to call it, a “demi-Earth”? A jumbo dwarf planet or jumbo shrimp planet? Give me a break!

Tyson is on much firmer ground - as well within the proper astrophysical sphere -  when he explores the lives and deaths of stars, as well as the scale of the cosmos, how stars radiate energy and stellar spectra. The last two are especially important cornerstones of astrophysics, and Tyson does a stand up job. One also hopes that when curious readers finish his chapters they will move on to Lawrence Aller's  (and now also Leo Goldberg's) 'Atoms, Stars and Nebulae' - which remains the standard for elementary astrophysics in terms of deciphering the nature of stars.

But Tyson and company excel in their own approach presenting the (usual) less advanced reader with numerous examples borne out by superb diagrams such as Fig. 2.4 showing Kepler's laws, and Fig. 6.2 showing the energy levels and associated spectral line series for hydrogen. I also liked how Tyson delved into the historical background, e.g. for the Balmer series, discovered in 1885.

The H-R diagram (Fig. 7.1) is also one of the best, most beautiful I've seen in any astrophysics text, with the relative sizes of specific stars - like Betelgeuse and Aldebaran - in color and projected against their evolutionary tracks. It's also interesting just how the famous diagram was composed: "From a catalog of stellar luminosities and temperatures Hertzsprung and Russell started filling in the diagram and discovered stars did not occupy just any place". Well, no, because it plots the stellar spectra (or surface temperature) vs luminosity so because each stars has distinct pairs of these, it will have differing positions on the H-R grid.

One warning here: Tyson uses an unorthodox form for describing nuclear fusion reactions in stars. For example (p. 101):

ppn + ppn  =  ppnn + p + p

As opposed to say,

3 He + 3 He ®  4 He + 1H + 1H  + 12.85 MeV

with the energy given off.    But truth be told, this notation of his would probably only irritate purists or pedants

What really sets the text apart is all the calculations shown, all very basic, such as the total energy a star will generate over its lifetime by multiplying the star's luminosity L by the lifetime. T. In fact, all the math used which leads to so many fascinating insights, is fairly basic. None of it ought to be beyond a person who has taken at least first year algebra though the derivation of  E = m c2       in Appendix I will likely require at least an intermediate algebra background to follow. .

What makes this book so special is that it offers the reader so many more useful insights and "tidbits" - for lack of a better word- than most astrophysics texts would at this level. One learns, for example (p. 51) "Superman can indeed throw an object 5 miles per second . The object will also fall under the influence of gravity but its curved trajectory now matches the curvature of the Earth such that it never hits the surface and ends up in a circular orbit."

De Grasse Tyson's conversational style, which served him so well in his  2014 reprise of 'COSMOS'  e.g.

is apparent throughout his chapters in the current work. For example, on p. 88, we read:

"You can think of the outermost layer of a star as a tree. Do you know what is coming toward the tree (from inside the star)?  Mixed nuts. We have a mixed nut cannon (the interior of the star) firing mixed nuts (photons at different frequencies) into the tree, and in the tree we have squirrels. My squirrels like acorns (the photons) - these are acorn squirrels. They see all these mixed nuts coming through but they are grabbing only the nuts they like, the acorns, on the other side. (outside the star) come mixed nuts minus the acorns (the thermal radiation minus the H-alpha  photons)"

The reader has to understand that this sort of description is uniquely Tyson's, You won't find it in the chapters by Gott or Strauss, though theirs do remain in a colloquial mode.

The takeaway here is that if you enjoyed the COSMOS series you should find a lot  to enhance your reading in this book. There is all one could ask for to gain a foothold in grasping the basic principles of astrophysics - as well as other topics not specifically related to it, such as how the zodiacal constellations came to be (including why astrology is off) and, of course, why Tyson doesn't regard Pluto as a planet.

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