Monday, December 24, 2018

Problems with Pop Sci from Sky & Telescope

Last year, I bought myself the Page-a-Day Incredible Cosmos desk calendar from Shop at Sky dot com, the retail arm of the leading magazine for amateur and hobby astronomers. Most days offered interesting snips of knowledge to consider and even wonder about. About 40 pages made questionable assertions. A few were laughable, the bad science being a consequence of poor philosophy.

First of all, it is important to note that astronomy is one of the few remaining studies—numismatics being another—where professionals work with and learn from amateurs. All of the world’s institutional observatories combined are not enough to watch and record all of the sky all of the time. Competing research schedules force narrow windows on professional staffs. On the other hand, amateurs can devote all the time they want to their own passions. Amateurs routinely discover comets and asteroids. NASA’s public webpages on meteorites cites the International Meteor Collectors Association. Cornell University’s page on the subject points to the American Meteor Society. Put “discovery by amateur astronomer” in your search engine. Some projects, such as the search for planets orbiting stars outside our solar system (“exo-planets”), involve amateurs being enrolled to access and review thousands of images from space-borne telescopes such as NASA’s Kepler. In most cases, amateurs work entirely on their own. So, we amateurs and hobbyists expect good science from Sky & Telescope. 

August 19: “Cosmic rays aren't rays--most of them are protons shooting through space at a significant fraction of the speed of light.”  So, what is a “ray”? A so-called “gamma ray” or “x-ray” is quantum packet, right? Isn't everything? Alpha rays are helium nuclei. Beta rays are electrons. I had a freshman physics homework problem to calculate the wavelength of a fast ball using Planck's equation. 
 
HyperPhysics from Georgia State University here 
July 3: “The whole universe (including the parts we can't see) might be infinite.”  That begs a lot of questions. If it is infinite, then you could take away the parts we cannot see and it would still be infinite, right? If the “whole universe” is infinite, then is it comprised of a finite number of infinite subsets, or it is comprised of an infinite number of finite subsets? What do they mean by “see”? Does that include what we “see” with radio telescopes? Does this include Dark Matter, which we can calculate but cannot detect, i.e.,“see”? Which meaning of “infinite” applies here? Can the Universe be finite in space but eternal in time? If so, what can “space-time” refer to? Objectivists assert that the Universe does not exist “in” time, but that time exists in the Universe.


July 9: “The temperature of the Sun is almost 10,000°F (5,778 K)—hotter than burning rocket fuel.”  In fact, the temperature of the Sun varies from the core to the corona; and actually the surface (photosphere) is cooler than either of those. 
  • The center of the Sun: about 15 million degrees Kelvin (often stated as “Kelvins”).
  • Radiative Zone: Temperature falls from about 7 million to about 2 million K across this zone.
  • Convection Zone: drops from 2 million K to 5800K in this zone.
  • Photosphere: about 5800K, although sunspots are about 3800K – that’s why they are dark.
  • Chromosphere: 4300 to 8300 K from inside edge to outside edge
  • Corona: about 1 million degrees 
(From the Cornell astronomy department public pages here and see also Scientific American online here .)

August 5: “A third of all planets discovered by the space-based Kepler mission have a super-Earth or mini-Neptune. (Most of these planets are not at all habitable, though.)”  Well, now they are not. Neither were the Arctic and Sahara habitable until someone figured out how. If on principle the Moon is not considered uninhabitable why would Neptune be?

February 7: “When you look up tonight, you see stars because the universe is transparent. Between 380,000 and a few hundred million years after the Big Bang, that wasn’t the case.”
and
August 15: “A fog of neutral hydrogen kept the universe dark in the so-called ‘dark ages’ during its adolescence between 380,000 years and a few hundred million years.”
and
August 16: “The first galaxies began forming a few hundred million years after the Big Bang.”  In the first place, the universe is not transparent. If it were, we could never detect anything, not galaxies, and not our keyboards. It is the problem of Superman’s X-Ray Vision: if he sees through everything, then he sees nothing. A better statement is that interstellar space is mostly not opaque. (See, also, Olber's Paradox.) The cosmology implied by these three claims is that the hydrogen “fog” began to coalesce as (diatomic) hydrogen molecules were attracted to each other. But it is also true that we believe that most of the “stuff” of the universe is as-yet-undetectable “Dark Matter.” So, we may still be in the Dark Ages …

February 4: “When two galaxies merge, the space between the stars is so vast that they almost never collide. Instead, the stars are swept into different orbits around the new galactic center.”  Galactic mergers are complex events. One resource is the GalMer Project of the Paris Observatory (http://galmer.obspm.fr) where you can try your hand at any of the 1000+ simulated interactions between 15 Hubble Types of galaxies. Easiest here is that it seems typical of elliptical galaxies that the stars do not orbit the galactic center, but move along seemingly random paths of Brownian motion on a galactic scale. However, that stage is supposed to be the last in a complicated interaction. While galaxies are merging, whatever were their centers are arbitrarily the new foci, two “centers” that add (by vectors) to a new barycenter. The same phenomenon applies to our own solar system: the planets do not revolve around the center point of the Sun; their orbits are ellipses with the Sun’s (shifting) barycenter as one focus.

February 5: “Intracluster light is the name for the ghostly glow in the space between galaxies, emanating from the lost stars tossed out of their hosts during gravitational interactions.”  Given the complexities (see above), it remains more likely that the stars were pulled out their host galaxies, not tossed out by them. 

Previously on Necessary Facts

Questions about “A Brief History of Time” 

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