In the beginning this blog was centered on San Francisco parks and open space issues with special emphasis on natural areas and natural history. Over time it began to range into other areas and topics. As you can see, it is eclectic, as I interlace it with topics of interest to me.

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Monday, February 20, 2012

2012.02.20 special astronomy edition

1.   We celebrate Copernicus on his 539th birthday
2.   Editorial on science budgets
3.   Now showing: the 3 brightest planets, soon to be joined by 4th
4.   The stunning Helix Nebula
5.   Comparative sizes and distances - to stretch your mind

1.  Nicolaus Copernicus, 19 February 1473 - 1543
    Mikolaj (German: Niklas Koppernigk).  Later he Latinized his name

See the revolution of the times

Indicated excerpts below are from Dava Sobel,  A More Perfect Heaven: How Copernicus Revolutionized the Cosmos.

In my later years love of history and philosophy has deepened and intensified.  Reading the life and times of those (primarily Francis Bacon, Copernicus, Kepler, Galileo, and Newton) who developed science  -  the systematic study of the structure and behavior of the physical and natural world through observation and experiment - has occupied so many of my most pleasurable and rewarding hours.  However, I was chary of giving much credit to Copernicus.  After all, I thought, Aristarchus of Samos had determined that the Earth and planets revolved around the Sun in 250 BCE, so why was Copernicus given credit?  The short answer is that Aristarchus never developed his idea into a system that explained how it worked.

In order to understand the achievement of Copernicus you must project your mind back to the world of 500 years ago.  Not easy.  We are so accustomed to graphics portraying the solar system that we can't appreciate what a knotty puzzle he had to solve.  It would have been fairly easy if planets orbited in perfect circles, as everyone knew they did.  Copernicus never did solve that conundrum; he kept the circular orbits but nevertheless resolutely managed to keep the Sun at the center, leaving the orbits for Kepler, whose struggles were promethean.    Even then, one holdout, Mercury--the fly in the ointment--had to wait for the 20th century and Einstein, as even Newton's monumental achievement couldn't account for its peculiar orbit.

 A more substantial answer to why credit belongs to Copernicus is hinted at by Sobel:

.. his father's copper and other common substances could not be considered elements in the modern sense of the periodic table.  Rather, they comprised some combination of the four classic elements:  earth, water, air, and fire.  The heavens, in contrast, consisted entirely of a fifth essence (also called quintessence, hence our word), called ether, which differed from the other four by virtue of being inviolate and everlasting.  Ordinary objects on Earth moved more or less along straight paths, whether seeking their natural places in the world order or being compelled by outside agents.  Heavenly bodies, however, lay cocooned in celestial spheres that spun in eternal perfect circles.  (Emphasis added)

This belief, bought into by Aristotle, that bodies in the celestial realm moved in perfect circles, held back progress for two millennia.  It also caused Galileo to be humiliated by the church.  The great Ptolemy, who dominated astronomical thinking for 1500 years, went through contortions to keep the circles and save the appearances--ie, how the Sun, planets, even stars appeared to move.  No one knew what gravity was or what it did.  Ptolemy devised a convoluted Rube Goldberg system of epicycles and epicycles within epicycles to account for how the heavens actually behaved--sort of.  So planets and Sun often revolved around arbitrary empty points in space.  All this in the name of keeping Earth at the center of the universe, which later the church accepted as doctrine, as it served to keep humans at the center of God's concerns.

So Copernicus as a church Canon (the Timid Canon, in Arthur Koestler's Sleepwalkers), had to steer his way through church politics as well as the larger political landscape.  To be assured, he accumulated vast storehouses of heavenly observations over his lifetime, and he incorporated these in his great book De Revolutionibus Orbium (On the Revolutions of the Heavenly Spheres)--which he would allow no one to see.

Somehow in spite of his efforts, word was seeping out and moving through the underbrush.  A young Lutheran mathematician and associate of Martin Luther, Rheticus, from the university at Wittenberg, showed up on Copernicus' doorstep, a great risk in this Catholic region.  Executions and burnings at the stake were common in this turbulent time for those holding heretical beliefs--and Rheticus not only held that belief but was a Lutheran in Catholic country, for which he could be killed summarily.  (Additionally, he was homosexual, although from what I can discern in Sobel's brief mention that didn't seem to be much of a problem, which, if true, surprises me.) 

Copernicus was not happy about this eager mathematician's offer of help and tried very hard to dissuade him and make him go back to Wittenberg, to no avail.  The story of this relationship is complex and very interesting.  Rheticus like a bulldog grabbed hold of the idea of the Sun at the center of the universe and wouldn't let go.  Copernicus was insistent that the book was not ready (he feared mathematicians as well as the church), but after great effort and danger to both of them, Rheticus wore down his reluctance.  At this point Copernicus' health (he was almost 70--very old for the time) was declining and he knew he wouldn't live much longer.  As it happened, the first printed copy of De Revolutionibus Orbium was presented to Copernicus on his deathbed.  He expired--now beyond the church's reach.

One can't help wonder what would have happened if this Rheticus hadn't dropped in out of the sky.  Would On the Revolutions ever have been published?  Would someone else get the credit for putting the Sun at the center of the universe?  Copernicus' finding was the first staggering blow in the dethronement of the human ego, paving the way for Darwin and Freud.  All three were reviled; the latter two continue to be.  The church has not been happy.

On February 23, 1616, a panel of eleven theologians put the Copernican idea to a vote.  They deemed "the quiescence of the Sun in the center of the world" to be "formally heretical" because it contradicted Scripture.  They further found the heliocentric universe philosophically "foolish and absurd."  Although the earth's motion seemed to them an equally ridiculous concept, they declared it merely "erroneous in faith," since it did not explicitly deny the truth of Holy Writ.  These judgments formed the crux of an official edict issued on March 5, denouncing Copernicus's teachings as "false and contrary to Holy Scripture."  On the Revolutions would be named in a decree appended to the Index of Prohibited Books.  But instead of being banned and destroyed--the fate of other forbidden titles--On the Revolutions was to be suspended until corrected.  In the decades since its publication , the book had proved so useful that the church could not justify condemning it outright.  Indeed, the much-desired calendar reform that engaged Copernicus during his lifetime had since been implemented with the help of his text.  On the Revolutions and the Prutenic Tables provided the mean length of the tropical year and synodic month that enabled the Jesuit Father Christoph Clavius of the Roman College to create the so-called Gregorian calendar, which replaced the Julian in 1582, during the pontificate of Gregory XIII.

(Kepler advised readers to "regard the Holy Spirit as a divine messenger, and refrain from wantonly dragging Him into physics class.")

I deem it my duty and task to advocate outwardly also, with all the powers of my intellect, the Copernican theory, which I in my innermost have recognized as true, and whose loveliness fills me with unbelievable rapture when I contemplate it.
    Johannes Kepler, Epitome of Copernican Astronomy, 1617-21

The constitution of the universe, I believe, may be set in first place among all natural things that can be known, for coming before all others in grandeur by reason of its universal content, it must also stand above them all in nobility as their rule and standard.  Therefore if any men might claim extreme distinction in intellect above all mankind, Ptolemy and Copernicus were such men, whose gaze was thus raised on high and who philosophized about the constitution of the world.
    Galileo Galilei, Dialogue Concerning the Two Chief Systems of the World, 1632

Every time the Kepler spacecraft, currently in orbit, detects a new exoplanet around a star beyond the Sun, another ripple of the Copernican Revolution reverberates through space.  But the counter-revolution that sprang up in immediate reaction to Copernicus's ideas also continues to make waves.  State and local governments still claim the right to control what can be taught of scientific theories in classrooms and textbooks.  A so-called museum in the southeastern United States compresses the Earth's geological record from 4.5 billion to a biblical few thousand years, and pretends that dinosaurs coexisted with human beings.

The following are all Greeks, all Before Common Era except for Ptolemy, and all achieved astounding insights into the nature of reality.  What was it about this time, and this ethnic group that could possibly explain these sample achievements--the most brilliant flowering of innovation and creativity in history?

Thales of Miletus in 585 BCE predicted a total solar eclipse

Aristotle demonstrated that the earth is spherical

Heraclides of Pontus proposed that the earth rotates on its axis once a day

Aristarchus of Samos proposed that the Sun is at the center of the universe

Eratosthenes of Cyrene worked out the earth's circumference with a high degree of accuracy

Hipparchus of Nicaea discovered the precession of the equinoxes

Sosigenes of Alexandria worked out that a solar year is 365.25 days in length (46 BCE) and thus established the so-called Julian calendar, which is named after Julius Caesar, who employed his services

The greatest astronomical work of antiquity was Ptolemy's Almagest (2nd century CE), even though it was based on a geocentric conception of the universe

"The closer you get to real matter, rock air fire and wood, boy, the more spiritual the world is."
    Jack Kerouac, The Dharma Bums


2.  Editorial - Astronomy March 2012 (excerpts)

...Science has faced a tough future for some time in this country.  Most Americans live in a 2-D world, focused on the activities of their daily lives and utterly oblivious to the cosmos around them or what it means.  The search for the ordinary in our day-to-day existence is what dominates most people's thinking.  Too often, people forget that the drive to know, to understand, to comprehend the reality of the universe around us is what separates Homo sapiens from lower orders of primates.

Even if they admit the value of understanding how the universe works, many people devalue such knowledge during hard economic times, when more-mundae situations rise up to dominate thinking.  When times are hard, it doesn't matter to many that NASA's budget is less than 1% of the federal budget.  To some, it seems superfluous, even though the moment after they complain about useless spending on science, they pull out their cellphones--a technological byproduct of the space program--and commence a meaningful conversation about which brand of diced chicken to buy.  Oh well.

...NASA's science programs will receive $5.1 billion next year, including $530 million for the James Webb Space Telescope.  For those who don't remember, the long-planned scope is a successor to Hubble in that it is a huge observatory outside Earth's atmosphere, but it is different in that it's optimized for infrared observations and will focus on questions of cosmic origins--sorting out how the first stars and galaxies formed in the early universe.  This is one of the major open questions in cosmology.


3.  Three naked eye planets are currently in our night sky, and we have had several clear nights to enjoy them.  The bright Jupiter is outshone by the even brighter Venus in the western sky, Mars in the east.  A fourth naked-eye planet, Saturn, will come into view in late March.  The 5th naked-eye, fleet-footed Mercury, is always elusive and you're lucky if you see it once in ten years.  Conditions have to be just right.


4.  The following is devoted to the Helix Nebula.  The choice is arbitrary, as there are bazillions of wonderful sights to choose from.  Beauty is one thing, process another:  The Nebula illustrates evolution in action.  You see a star in a particular stage in its life--and death; the star is in its death throes, although it will continue to shine for billions of years.  (I don't understand how it can continue to shine after it has ceased nuclear fusion, but the big boys and girls tell me that it does.)
Dust and the Helix Nebula
NASA, JPL-Caltech, Kate Su (Steward Obs., U. Arizona), et al.
Explanation: Dust makes this cosmic eye look red. The eerie Spitzer Space Telescope image shows infrared radiation from the well-studied Helix Nebula (NGC 7293) a mere 700 light-years away in the constellation Aquarius. The two light-year diameter shroud of dust and gas around a central white dwarf has long been considered an excellent example of a planetary nebula, representing the final stages in the evolution of a sun-like star. But the Spitzer data show the nebula's central star itself is immersed in a surprisingly bright infrared glow. Models suggest the glow is produced by a dust debris disk. Even though the nebular material was ejected from the star many thousands of years ago, the close-in dust could be generated by collisions in a reservoir of objects analogous to our own solar system's Kuiper Belt or cometary Oort cloud. Formed in the distant planetary system, the comet-like bodies would have otherwise survived even the dramatic late stages of the star's evolution.


Google the Helix Nebula and you'll find more information and beauty than you can handle.  The Nebula has been photographed through many filters and wavelengths, each of which reveals another aspect of the reality of this stunningly beautiful dying star.  The Sun will die similarly in a few billion years.  Will we be this beautiful?  You'll have wait.

When the Sun swells up and becomes a Red Giant it will encompass the orbits of Mercury, Venus, Earth, and possibly Mars.  Long before this all life would have been destroyed on Earth and Mars (if it existed there).  One wonders how creationists can ignore the fact that everything has a life span; it is born, evolves, and dies.  It becomes something else, perhaps never imagined.  It's an awe-inspiring process.  Who would want to deny it?

This is a tiny sample of stuff that's out there that is outside our experience, but which we can experience through the internet.  We are denied dark skies by our unthinking and wasteful lifestyle, but you can still enrich your life and wonder about it all through pictures and writings.

If the Sun were a half-meter ball:

Earth is 5 millimeters - 55 meters away

Jupiter is 50 millimeters - 284 meters away

The nearest star, Alpha Centauri, is at Perth, Australia

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