[image: Tiresias.jpg]
*Tiresias: * *How to make a prophet*
When the ill-fated Oedipus Rex summoned the blind prophet Tiresias to ask
him the causes of Thebes' plague, the sightless soothsayer told him in a
roundabout way that the king, himself, was to blame.   It turned out that
Oedipus had, indeed, killed his father and married his mother, as the
Delphic Oracle had prophesied.  As the gods loathed both patricide and
incest -unless they, themselves were the ones committing either act-the
plague would only end after Oedipus was expelled.  Oedipus was sorry he
asked.    Years earlier, Liriope asked Tiresias if her then infant son,
Narcissus -we encountered him last week- would live a long life.   "Yes,"
Tiresias assured her. "But only if he never knows himself."  The irate
Liriope considered this answer so cryptic and unhelpful that she was also
sorry she asked.  Many years later, when Tiresias was dead and residing in
the Asphodel meadows, Odysseus -we saw him last week, too-ventured into the
underworld to consult him on how to survive his now famed Odyssey.
Tiresias offered invaluable advice, including ways to cope with the dreaded
Scylla and Charybdis.  In that instance, Odysseus was quite pleased to hear
what Tiresias had to say.  Those are just three out of many times when
Tiresias' assistance was requested by those seeking sage advice
As Tiresias was arguably the mythological world's most celebrated prophet,
it might come as a surprise to learn that he wasn't born to be one.
Instead, he was made a prophet in a particularly strange way.   One day the
young and sighted Tiresias was wandering around Mount Cyllene when he
happened upon two copulating snakes. Repulsed, Tiresias separated them with
a stick and then tossed them away from each other.   Hera observed this
violent act and angrily transformed Tiresias into a woman. As a female,
Tiresias eventually served as a priestess of Hera and gave birth to Manto,
who matured to become a revered prophetess.   After seven years of living
as a woman, Tiresias once again encountered two copulating snakes   Though
still disgusted, she did not interfere.   Her restraint appeased Hera who
then returned Tiresias to male form.
Many years later, Hera was chastising her husband Zeus for his innumerable
infidelities.  He defended his indiscretions by claiming that physical
intimacy was all to the woman's benefit and for men was, in his words
"mostly just work."  (Fool.)   Appalled by that claim, Hera called forth
Tiresias, who was still serving Hera in a religious capacity.   As he had
lived as both male and female, Tiresias was believed to have been uniquely
qualified to resolve the dispute.    "Who benefits most from the coital
act," Hera asked him.   Tiresias replied,
"If love's pleasures count as ten,
 thrice three go to women, only one to the men."
While Zeus chortled heartily, Hera became incensed and punished Tiresias
with permanent blindness.    Although Zeus could not restore his sight as
that would require negating another Olympian's punishment, he did gift
Tiresias with the power of prophecy: second sight.   Tiresias quickly
cultivated this divine ability and soon became a prophet of note, though
not always a popular one.   One could regard him as the "Gandalf" of the
Cadmus family.  The blinded prophet Tiresias was present through all seven
generations of the Cadmus household.  He was first advisor to Cadmus and
then appeared in many of the tragedies that occurred to his cursed
descendants.  He finally perished after the Cadmus line was ultimately
destroyed in the Seven Against Thebes war in which Oedipus' two sons (and
brothers) killed each other in a battle over the Thebian throne.

THE SOUTHWORTH PLANETARIUM
207-780-4249   www.usm.maine.edu/planet
<http://www.google.com/url?q=http%3A%2F%2Fwww.usm.maine.edu%2Fplanet&sa=D&sntz=1&usg=AFQjCNHulkHuLP13bOG2PkNrPazsGWFs2A>
70 Falmouth Street   Portland, Maine 04103
43.6667° N                   70.2667° W
Altitude:  10 feet below sea level
Founded January 1970
Julian Date: 245953.16
2019-2020:  CXXV

THE DAILY ASTRONOMER
Monday, April 13, 2020
Remote Planetarium 11:   A Tourist's Guide to the Planets

Greetings!
Welcome back.   I know you missed us, but not nearly as much as we missed
you.  Today we're going to embark on something of a field trip.   Granted,
we'll all be far apart from one another as social distancing is the current
custom.  In fact, you'll be at home pretending you're with us.  Our aim is
to introduce you to just a few of the many breathtaking vistas within our
solar system.  Yes, we mean that literally as we'll have no oxygen to enjoy.
First things first, however.
We're standing in an empty parking lot (the only kind that exists
presently) with, of all things, a roll of toilet paper!  Yes, we actually
found one.   We also have a softball. One might wonder why would a solar
system tour begin with such items?  Simple.  Before we explore the planets,
we need to understand their sizes relative to the Sun and to each other.
 You see, we planetarium fools often show off solar system models like this
one:
[image: solar-system-with-sun-and-planets-on-orbit-vector-13205901.jpg]
Bright, cheerful, neatly arranged and, of course, likely stolen.   Thank
you, VectorStock.   Such a model does present the planet in their proper
order:  Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and
Pluto.  The problem is that it isn't to scale, not by a long chalk.*
 Hence, the toilet paper and softball.  It will help us put the solar
system into perspective.
First, put the softball on the ground.   It represents the Sun.  You're
welcome to paint it yellow, provided you know it isn't actually yellow.
(We'll explain why next week when we turn our attention Sun ward.)   Next,
place one end of the toilet paper next to the softball and then roll it
out.       Each sheet represents one million miles. Mercury will be half
the size of a paperclip hole located 36 sheets away.   It will be much
farther away than one would expect.    We should note that in this model
we'll be placing the planets at their average distance.  Recall that
planets travel along elliptical orbits and their distances from the Sun
change continually.
Venus will be 67 sheets away and will be the size of a paperclip hole.
Earth will be 93 sheets away and also the size of a paperclip hole.
Now, stop for a moment and observe.      The Softball-sized Sun is
surrounded by three minuscule holes at vast distances from it.    Earth is
hardly even visible!
We continue:
Mars will be 142 sheets away and will be about 3/4 the size of a paperclip
hole
Jupiter is 484 sheets away and the size of a hole at the center of those
old 33 1/3 records.
Saturn 887 sheets; Uranus 1,784; Neptune 2,794 and finally Pluto 3,675
sheets.
Granted, we're not expecting you to roll out all the toilet paper even if
you could somehow gain possession of so much without legal consequence.
Just know that the Sun represents more than 99% of the solar system.  The
planets and their moons are just little motes trapped inside its immense
gravity well.

*We begin our rapid planet trek, skipping Earth, which is so boring. *


[image: MTEiJvP99DScN3vkAsE9LA-320-80.jpg]
*MERCURY*
Be careful if anybody invites you to spend a day on Mercury.    Days on the
first world last nearly two Earth months!  Although this planet rotates
slowly, as it is the first planet, it revolves rapidly.   With an average
speed exceeding 160,000 miles an hour, Mercury completes an orbit in
approximately 88 days.     Consequently, a Mercurian would see only two
sunrises a year!    Unsurprisingly, Mercury's surface bakes under a Sun
that appears 2.5 times larger than the Sun we see on Earth.    Its daytime
temperature exceeds 700 degrees F, hotter than a pizza oven.   However, as
Mercury lacks an atmosphere apart from whispers of sodium vapor, its night
side is frigid with temperatures around -200 degrees F: a nearly 1000
degrees day-night temperature range.        On the bright side, Mercury
surface gravity is significantly less than Earth.  A 200 lb Earthling would
weigh in at 74 pounds on Mercury.
DOWNSIDES:

   - Absolutely no oxygen to breathe
   - High radiation levels
   - You'd cook in the day time and freeze at night

[image: kaPwBjHiUKax8syodHNPmF-320-80.jpg]
*VENUS*
Let's face it: Venus was a disappointment.  Seen from Earth, the second
world is so beguilingly beautiful we associated it with Venus, the Roman
counterpart to Aphrodite, goddess of love and beauty.   Moreover, many
astronomers assumed its surface would be lush and verdant: a tropical
paradise extending from pole to pole.   They based this hopeful assumption
on Venus' close proximity to the Sun and its pervasive cloud cover.   It
seemed to have the two fundamental ingredients required for any true rain
forest.  Fierce heat and abundant rainwater.   While it possesses the
first, it lacks the second.   Its thick carbon dioxide atmosphere not only
traps heat, but produces clouds that pour forth sulfuric acid rains.   The
temperature exceeds 900 degrees F from pole to pole and the surface
pressure is 90 times greater than Earth's sea level pressure.   The only
known visitors to this world were the Venera spacecraft the Soviet Union
launched in the 1980's.   Though these vessels were metallic and shielded,
they lasted less than half an hour before Venus destroyed them.

DOWNSIDES:

   - What Hell must be like, but without the Black Sabbath music
   - Crushing pressure
   - Furious heat
   - the rain consists of the same acid used in car batteries
   - Oh, and you would NEVER see the Sun!

One "upside":  Venus's gravity is almost as strong as Earth's so you would
be able walk around on Venus just you do here, except, well, you'd be dead
before you could take your first step.

*Interesting note: *Venus's day equals 117 days, more than half the length
of its year. It also rotates backward relative to the other planets.   Of
course, one can't really tell the difference between night and day, anyway,
and since the temperature is constantly high, Venus has no real seasons,
either.

[image: ewcvC8bNBec6oMG9zufgVg.jpg]

*MARS*Mars was something of a disappointment as well, we must admit.
Whereas Venus was supposed to have been like Tahiti on a global scale, Mars
was supposed to have been a Tolkienesque world replete with imposing
castles, elegant princesses and a vast community of monstrous creatures and
even the occasional sorcerer.     Well, blah!  As far as we can tell, Mars
is devoid of life, though it might have harbored microbial life in the
distant past when the planet's surface was much wetter.    Mars is a cold,
barren desert world that also lacks the oxygen we need to life.   However,
it does possess water ice at its pole that would prove useful to us if we
could hold our breath long enough to reach it.
Unlike the first two planets, Mars does have natural satellites.  Two of
them: Phobos and Deimos, two captured asteroids whose names mean "Panic"
and "Fear."   Those are appropriate nicknames as Mars was named for the
Roman god of War.     As Mars is coated in iron oxide (rust), it appears
reddish in our sky.   Our conflict-weary ancestors likely associated that
color with blood, hence the name.
UPSIDES

   - Mars contains the solar system's largest mountain.* Olympus Mons*.  It
   towers 72,000 feet above the Martian surface and its base is as large as
   the state of Missouri
   - Mars is also scarred by the solar system's grandest canyon, the *Valles
   Marineris.*  Extending more than 2500 miles across the Martian surface,
   this immense canyon can reach of depth of about four miles.   Earth's
   celebrated Grand Canyon could fit neatly inside one of its offshoots chasms.
   - Its surface gravity equals that of Mercury so you'd weigh less on the
   fourth world.


DOWNSIDES

   - Yet, again, no air for us to breathe
   - Cold! Cold! Cold!   The highest temperature possible temperature is
   around 50 degrees. It is only that warm around the equator in summer


[image: Jupiter-980x607.jpg]
*JUPITER*
Now we're moving into new territory, into the realm of the gas giants.   We
can divide the planets into two categories.  The "terrestrial" planets:
Mercury, Venus, Earth and Mars and the "gas giant" planets:  Jupiter,
Saturn, Uranus and Neptune.    Pluto doesn't fit neatly into either
category.
The gas giants rapidly rotate, contain thick atmospheres that are utterly
unlike those enshrouding our planet, and all of them are surrounded by an
absurd number of moons.

Jupiter get high marks for aesthetic beauty owing to its kaleidoscopically
colorful cloud forms.  We are most intrigued by its "Great Red Spot," a
storm larger than Earth which has been raging for centuries.    It is
possible that Giovanni Cassini observed it in the 17th century.  We do know
that the Great Red Spot has been tearing through the Jovian atmosphere
since at least 1830, making it the most durable known storm in the solar
system.   (Even the most persistent hurricane on Earth lasts for only about
a month.)

One minor  problem:   Jupiter offers no surface on which to walk.   If we
tried to "stand" on Jupiter, we'd be consumed by its turbulent clouds and
would perish in an instant.   We could try to wander about any of its 79
known moons.   Yes, 79!   Jupiter boasts more attendant moons than any
other planet.   It is sensible that the fifth planet would be so well
endowed as it is the solar system's most massive planet.  In fact, it is
more massive than all the other planets put together.

DOWNSIDES

   - Even if we could stand on Jupiter, its gravity field is immensely
   strong. A 200 pound person would weigh 508 pounds on Jupiter
   - Again, the lack of oxygen thing.
   - True, Jupiter has plenty of moons, but only a few would be visible
   from Jupiter's cloud tops
   - COLD! COLD! COLD!  About -235 degrees F along the top of Jupiter.
    However, because of the enormous pressures, Jupiter's core is hotter than
   the Sun's surface, more correctly known as its "photosphere."

UPSIDES

   - It is Earth's protector.  As Jupiter is so massive, it has often
   diverted many incoming comets away from the inner solar system.   We have
   likely sustained fewer impacts due to Jupiter's presence.
   - Has a ring, though it is exceedingly difficult to observe.

[image: saturn-lead-image.jpg]
*SATURN*
The one we've been waiting for.     *  A+ *in the looks category.   Saturn
is the the famous ringed world that is almost one billion  miles from the
Sun.    Like the other gas giants, Saturn lacks a solid surface so bang
goes our hope to stroll under its majestic rings.  Although those rings
look solid when seen from a distance, they actually consist of billions of
small particles ranging in size from dust grains to railroad box cars.
 It is also surrounded by more than 60 moons, one of which, Titan- harbors
an atmosphere that might well be similar to that of the early Earth.
Saturn's average temperature is about -288 degrees F, which we would expect
being so far from the moon.       It is also torn by fierce winds owing in
part to its rapid rotation.  Saturn spins on its axis once every 10.5 hours
(slightly slower than Jupiter).   For this reason, Saturn is the solar
system's most oblate planet:  thicker around its equator than at its
poles.
DOWNSIDES

   - Ok, you know about the lack of oxygen issue. We'll stop mentioning it.
   - COLD!   COLD CO...  Sure, we'll stop talking about that, too
   - No surface on which to wa.....ok, and that


UPSIDES

   - Stand on a nearby moon and those rings will dazzle you into a stupor
   - It year lasts almost 30 Earth years so you'll have plenty of times to
   admire any given constellation before the Sun obscures it.


[image: NVAnBwuGufg8cf2RXkZigd-320-80.jpg]
*URANUS*
The planet every Middle School teacher hates.  Uranus was named for Uranus,
the Roman god of the sky.  It was the first planet to have been
"discovered," as all the closer planets have been known and observed since
antiquity.     Astronomer William Herschel discovered it on March 13,
1781.    He was astonished to realize that he had found the solar system's
seventh planet!
Uranus is "tipped over" on its side so that its axis almost spins along the
orbital plane as opposed to being perpendicular to it.    It has 27
attendant moons, far less than Jupiter and Saturn have, but still much more
than the terrestrials planets lay claim to.    Like the other gas giants
planets, Uranus contains ample quantities of hydrogen and helium, but also
harbors great stores of ammonia ice.
DOWNSIDES

   - Yes, we know!
   - Yes, we know!
   - Yes, we know!


UPSIDES

   - Miranda, one of its moon, has the distinction of having the highest
   cliff in the solar system:  Verona Rupes.   As it is nearly 20 miles high
   and is located on a moon with very weak surface gravity, a person who
   jumped off its summit would fall for more than twelve minutes!  (And, alas,
   still die after impact.)   Yes, not much of an upside.

[image: eNTJrysq4A6DqXncBtsRrB-1200-80.jpg]
*NEPTUNE*
Two astronomers,  Englishman John Couch Adams and  Frenchman Urbain
Leverrier independently discovered Neptune in 1846 by studying the observed
perturbations in Uranus's orbit.  They used Newton's gravitational laws to
mathematically determine its approximate location.  Leverrier persuaded
Johann Galle to search for the then-unknown world through his telescope,
which Leverrier did not possess.  Galle located the planet after only a
single hour search.   He found it about one degree from the position that
Leverrier had pinpointed.

With an average distance of 2.8 billion miles, Neptune is the most distant
of the gas giant worlds.  It requires about 165 Earth years to complete an
orbit.  In fact, it hasn't even completed two orbits since its discovery.
     It is also the smallest gas giant and has fewer known moons (14) than
any of the other Jovians.

Neptune was named for the Roman god of the sea, the counterpart to the
Greek Poseidon.  They named the seventh planet Uranus because he sired the
Titans, including Saturn.  Saturn sired the gods, including Jupiter, who
sired Mars.  The planets were arranged in order of lineage.  The problem
was that Uranus was born out of "Chaos," which meant nothing.  So, instead
of calling the eighth world nothing,  it was given the name "Neptune,"
because of its distinctive bluish coloring.  Methane, not water, produces
that blue tint, however.
UPSIDE

   - The surface of Neptune's largest moon, Triton spouts geysers that
   propel methane crystals miles high.   A sight that must be indescribable.

[image: jGqBq44gCE3CogJTXAnwjT-320-80.jpg]
*PLUTO*
Hey, none of that "it's not really a planet" talk!   At some point we'll
address Pluto's undeserved demotion.   Now, we just want to end with Pluto,
the solar system's ninth world. Discovered in 1930 by American astronomer
Clyde Tombaugh, Pluto's average distance equals 3.7 billion miles.  At that
distance, it requires 248 years to complete one revolution around the Sun.
 It hasn't even finished half an orbit since its discovery.

Pluto is the smallest world and the least massive one as astronomers were
able to determine after the United States Naval Observatory's James Christy
discovered its largest moon Charon in 1978.     Pluto is now known to have
five moons and might well have others that we cannot see from our vantage
point.   NASA's New Horizons probe flew by Pluto in 2015 and discovered
many features not visible from even the Hubble Space Telescope.  Its icy
surface is far more complex than once believed.

UPSIDE

   - Pluto and its largest moon, Charon, have established a mutual
   synchronous rotation.  Charon's revolutionary period equals its rotation
   period and that of Pluto.  If one were to watch Pluto in Charon's sky, it
   would not appear to move at all and vice versa.




*Looking for a diversion during your isolation?    Try "By the Sword
Divided," a wonderful and grossly underrated BBC dramatic series produced
in the 1980s and set during and then after the three 17th century English
civil wars.  https://www.youtube.com/watch?v=bQRVH08xZcI    It is highly
addictive and will make you want to use strange phrases like "not in a
long chalk."



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