June 5, 2003 SUMMER CYCLES

June 12, 2003 COUNTDOWN

June 19, 2003 STARS OF SUMMER

June 26, 2003 MOON DANCES

July 3, 2003 STELLAR FAMILY

July 17, 2003 THE SPEED OF SUMMER

July 24, 2003 MARS ATTACKS

July 31, 2003 TRANSITIONS

August 9, 2003 HAVE A BALL!

originally released August 9, 2003

HAVE A BALL!

There is a perfection in roundness: a simple efficiency, a brevity of
concept, an elegance of form. The roundness of a sphere evokes
self-sufficiency and potentiality: a water droplet falling freely, a
pea, a womb, an eye, the bowling ball of the Earth rolling through
inky space.

Despite long centuries in the middle ages when religious dogma
dictated otherwise, we have known that we live on a sphere for more
than three thousand years. Sailing ships dropping below the horizon
hull first, changes in the path of stars and sun with latitude, the
obvious roundness of the Earth's shadow on the moon during lunar
eclipses (plus analogy with the clearly round Moon itself): all these
suggest an Earth that is shaped like a ball.

As far as we know, the circumference of the Earth was first estimated
by the Greek librarian/geographer Eratosthenes in about 200 B.C.
Eratosthenes knew that in the town of Syene in Egypt, sunlight at noon
on the solstice would reach the bottom of a well, indicating that the
sun was directly overhead. In his hometown of Alexandria almost
directly north of Syene, vertical poles cast a shadow 7.2 degrees from
vertical on the solstice. With a little trigonometry, he went on to
estimate the circumference of the Earth to within a few percent of
what we know today.

The farther north we travel, the longer are the shadows, the shorter
are the summers, and the higher the Big Dipper appears in the sky.
South of the equator, the sun travels right to left across the
northern sky and the moon looks upside down. Fewer of heavens stars
are visible at extreme latitudes than at the equator, leaving northern
skies sparsely scattered with bears and cold dragons with only
occasional glimpses of the outskirts of the Milky Way while southern
skies are crowded with both galactic center and nearby Magellanic
Cloud galaxies.

Star-watching sessions in New Zealand left me gasping, feeling that I
might somehow fall off the bottom of this precariously round world.
Traveling north from mid-latitude California brings a subtler
impression, but the feeling of crawling away from the sun is
unmistakable during the daytime and the growing dominance of the Big
Dipper is obvious at night.

The round body of the moon becomes fully illuminated on Tuesday,
August 12 at 8:48pm PST. The same night (sadly for the visibility of
the show) is the peak of the Perseid meteor shower. Look 90 degrees
away from Perseus to see the most meteors and find some obstacle to
block the brightness of the moon.

PS Don't forget to look for Mars in the east after sundown\ over the
next few weeks.

Eratsothenes and the circumference of the Earth.
http://www.uu.edu/programs/physics/sciguysjuly2001.htm

Information on the Persied meteor shower.
http://SkyandTelescope.com/observing/objects/meteors/article_937_1.asp

originally released July 31, 2003

originally released July 24, 2003

MARS ATTACKS

Smaller than Earth but clearly once host to liquid water, Mars is a
planet we can wrap our minds around. Standing on that wind-bedeviled
surface, our toes would be a toasty 50 degrees F while our ears would
be frostbitten. Escarpments and hillsides, valleys and mesas provide
a familiar, homey landscape made only slightly alien by greenish
skies. Maybe we are in Earth's Mojave desert, or maybe a high desert
plain in Peru, but no, we are on Mars, millions of miles from home.

Although not visible in the east until midnight, Mars is now rapidly
brightening for its closest approach to the Earth in almost 60,000
years. Usually dim red like the prominent Scorpio star Antares, Mars
is now brighter than Jupiter and still growing.

Watch over the next few weeks. By the end of August, Mars will grow
to 16 times brighter and almost three times wider than its usual self,
providing excellent opportunity to detect ice caps and valleys in
small telescopes. Best yet, Mars will be visible by 9pm local time so
late night light-weights like me have a chance of enjoying the show.

On average Mars swings between (say) San Francisco (73 miles) and San
Jose (30 miles) in distance from the Earth, er, Santa Cruz, but on
this pass, Mars at closest approach passes through Los Gatos (22
miles). If you don't like to drive through Bay area traffic, now
might be a good time to visit the Sharper Image store.

Sure enough, astronomers are taking advantage of this close approach
and an armada of probes are on their way to the red globe. Two Mars
Exploration Rovers from the US recently dubbed Spirit and Opportunity,
a European lander called Beagle 2 (after Charles Darwin's ship) which
will be ejected from an orbiter called Mars Express, and finally
Nozomi, a trouble-plagued Mars orbiter launched by Japan in 1998 will
all converge on the Red Planet in the next few months. These new
vehicles join surviving American orbiters Surveyor and Odyssey which
have been continuously sending back data on the Red Planet since 1997
and 2003 respectively.

Let the glowing eye of Mars in the east suck you into the web of Mars
mystery. Did life ever evolve on that planet? Could microbial forms
still exist there today? Could humans ever set up self-sustaining
colonies there? The power of the human mind is to dream; I dare you!

Guide to observing Mars (also follow included links)
http://SkyandTelescope.com/observing/objects/planets/article_985_1.asp

Information on 2003 Mars missions:
http://www.cnn.com/2003/TECH/space/06/02/mars.race/index.html

originally released July 17, 2003

THE SPEED OF SUMMER

You might think that photons always travel at the speed of light. In
fact light travels at NO FASTER than the speed of light and often
considerably slower. This is not a subtle phenomenon only detectable
in particle accelerators or at vast interstellar distances but is as
common an every day experience as pavement, pools, and eyeglasses.

In a vacuum, the speed of light is 300,000 kilometers or 186,300 miles
per second. This may sound plenty fast, but it still takes eight
minutes for photons from the surface of the Sun to reach the Earth,
hours for light to reach us from the outer planets and years from the
nearest star systems. Galactic distances are even more staggering
taking photons thousands of years to cross galaxies and millions of
years to cross intergalactic spaces. Just as thunder lags behind
lightning more and more with distance from the strike, so too our
understanding of the universe is limited to what was going on `back
then' when the photons we see were emitted. This is why observing the
cosmos is like looking back in time.

But I wanted to talk today about more Earthly phenomena. On a hot
summer day we see heat waves shimmering over hot surfaces and mirages
over pavement. Diving into a pool we may misjudge the lay of that
coin on the bottom because of the refraction of light. All of these
phenomena occur because light travels slower in denser material than
it does in a vacuum. Light is a wave and, like a wave in the ocean,
it relies on the movement of the medium for transmission. In the case
of light, it is the electrons which must move, not entire atoms.

The `optical density' of a material is not identical with its physical
density, but it can be precisely measured. Light travels in air at
0.9997 times its speed in vacuum, but this small deficit is enough to
bend the light so that the sun appears flattened at sunset. Lower
density air near hot pavement causes the light to move faster there
and the cooler (denser) air above it curves the light into an arc so
we see dancing bits of sky down near the surface of the road, et
voila: mirage! Eyeglasses and contacts make use of the refractive
index of various materials using special shapes to bend the light to a
different focus. Light in water travels at three quarters of its
speed in a vacuum, and diamonds are efficient casters of rainbows in
part because their tight molecular bonds slow light down to a mere
75,000 miles per second.

So catch some rays this weekend! It seemed like forever for it to
arrive, but I do assure you, summer will be over before you know it.

Optical density and light speed:
http://www.glenbrook.k12.il.us/gbssci/phys/Class/refrn/u14l1d.html

originally released July 3, 2003

originally published June 26, 2003

MOON DANCES

Jupiter, so few weeks ago high overhead, almost lost among the
glittering stars of spring, now rides alone, low and bright in the
lingering summer twilight sky. At 317 times the mass of Earth,
Jupiter is the most massive planet in our solar system, yet a Jovian
day lasts only ten hours. Hurricane force winds are driven by this
ferocious rotation, drawing Jupiter's clouds out into alternating
bands of light and dark which hide the gaseous depths below.

As if Jupiter itself were not enough to contemplate, the mighty gas
giant plays mother hen to scores of satellites or moons. Although
there are now over 60 identified Jovian satellites, four are much
larger than the others, worlds in their own right. Observed as early
as 1610, the movements of these four ``Galilean moons'' provided
evidence that not all celestial objects orbit the Earth. The moons
were soon named by Kepler for three of Jupiter's human lovers: Io,
Europa, and Callisto and the largest for Ganymede, a handsome human
youth carried away by Jupiter for a cup-bearer.

Io is the famous ``pizza-faced'' moon whose surface is alive with
volcanos actively belching plumes of sulfur and trailing silicate
magma. Less than three Jovian diameters from its massive primary, Io
is constantly kneaded by tidal forces and is alternately stretched and
compressed by the pulls of Jupiter and the other three large moons.

Europa has gained notoriety lately because pictures from the on-going
Galileo probe mission (launched in 1989) reveal evidence for a deep
surface ocean. The top of this ocean is frozen to a depth of maybe 10
miles, but the many visible cracks and folds suggest the existence of
some 60 more miles of liquid water below. With liquid water always
comes the possibility of life, and Europa, after Mars, is thought to
be the likeliest site for extra-terrestrial life in our solar system.

Next moon from Jupiter is Ganymede; larger than either Mercury or
Pluto but less massive, Ganymede is the largest satellite in the solar
system. Cooler than the inner two moons because distance diminishes
tidal forces, Ganymede's surface is pocked with impact craters and
resembles our own Moon. And fourth of the Galilean moons is Callisto.
Colder still, its surface is a network of overlapping craters from
four billion years of relentless impacts.

New moon falls this Sunday at 11:49am PDT. A growing crescent will
sweep by Jupiter next week with closest approach on Wednesday, July 2.

If you have a mind to reconstruct Galileo's discovery, you can trace
the dancing of the moons of Jupiter with a simple pair of modern
binoculars. Sketch the order of the moons as you see then from night
to night. You will be amazed at how rapidly they change places.

number of Jupiter's satellites reach 61:
http://www.ifa.hawaii.edu/~sheppard/satellites/jup2003.html

history of the discovery and naming of the Galilean moons:
http://es.rice.edu/ES/humsoc/Galileo/Things/jupiter_satellites.html

images from the Galileo mission:
http://www.jpl.nasa.gov:80/galileo/images/images.html

originally published June 19, 2003

STARS OF SUMMER

Summer Solstice saunters into town Saturday, June 21. The Sun reaches
northernmost latitude at (appropriately enough) just past noon PDT.
This first official day of summer is also the longest day of the year.
Even though the days slowly shorten over the next few months, the
weather (away from the fog-cloaked Santa Cruz coast) will continue to
grow warmer due to the slow thermal conductivity of atmosphere and
continents.

Long twilights and mild weather make summer evenings perfect for
outside socializing. Over the next few weeks the nights will be
moonless and starry. While sipping your cocktail at campsite or
garden party, let your eyes scan the darkening heavens. Who will be
the first to spot a star?

The first point of light visible in the evening sky tonight is
Jupiter. While not exactly a star, finding Jupiter can be all the
more exciting since it is a glimpse into a world all its own: one with
unfathomable gaseous depths, Earth-sized tornados, and an entourage of
interesting moons: four of which can be seen through binos. Jupiter
will be visible high in the west long before the sky is fully dark.

Almost overhead at sundown stands the red giant Arcturus, third
brightest of all the stars in the night-time sky. You can find
Arcturus by following the curve of the handle of the Big Dipper (arc
to Arcturus). Continue the same arc south and you will come to Spica
(speed on to Spica). The blue supergiant Spica (``Spike-ah'') marks
the foot of the lazy Y of Virgo sprawling out to the west (right).

Although you will have to wait until 10pm for it, full dark reveals
the Summer Triangle, gigantic in the northeastern sky. Bright blue
Vega is easiest to spot on the leading edge of the Triangle; it trails
a small parallelogram of stars which make up Lyra, the Harp. Deneb,
head of Cygnus (the Northern Cross), is north of and lower than Vega.
Follow the the length of the cross south (parallel to the horizon) to
trace the center of the rising summer Milky Way. Below the cross, at
the very eastern edge of the Milky Way is the last to rise member of
the Summer Triangle, Altair, bright eye of Aquila, the Eagle.

After weeks of expectation, summer is finally here! So what are you
waiting for? Get out there and do it!

free interactive sky chart:
http://SkyandTelescope.com/observing/skychart/

originally published June 12, 2003

COUNTDOWN

The days stretch ever more slowly, creaking as they near the limit of
their resilience: a minute here, thirty seconds there. Day by day we
creep closer to the summit of the hill so that I can ... almost
... peer ... over it... into the blazing heat of summer. But not
quite yet. Despite the warm weather and the thick and drippy coastal
fog, summer is not yet - not quite yet - officially here.

Saturday morning's full moon (4:16am PDT) lends a brilliance to the
night hours that solstice will be hard pressed to match. From hour to
hour the light floods down from a beacon slowly traversing the
southern treetops. Constellations will be lost in the glow of the
moon tonight, and the sky will be blue-green with scattered light.

Now is the time to dance and play in the orchard all night, to run in
and out of the deep black moonshadows under the newly set fruit. Come
with me also, you new June brides, and revel in your gladness! Run
laughing down the beach with your partner, and splash shrieking
through the evening's chill surf. Rejoice, you new mothers, gazing in
rapt stillness at the moonwashed cradle with its ensconced miracle.

Don't you feel lost in the wonder of life's bounty? Drink in your
love until it catches in your throat and tumbles down your face in
tears. Why wait until tomorrow when the moon will have faded? Why
wait until tomorrow when we may no longer be together? Come dance
with me now, fond friends; pound your feet on the hardwood floors and
throw your arms wildly into the air. I offer now my happiness to the
universe; what finer gift can I make to God but that?

The ticking of the clock at noon counts down the summer midnight boom.

originally published June 5, 2003:

SUMMER CYCLES

The constellations make their yearly rounds of the heavens with due
precision, but there is a subtle evolution even in things celestial.
Over the years, stars shift on their swirling dance through the
galaxy. Stars also slowly brighten and fade with their own internal
processes. Over the course of millenia, the constellations morph and
skew. So too interrelationships and internal processes dictate our
personal evolution which can at times seem glacial, but is indubitably
continuous.

The longest day of 2003 is approaching, bringing alternating waves of
dry heat and foggy, drippy cold to the Santa Cruz mountains. The
longer twilights feel more leisurely, and dinner sometimes waits until
9:30, but the price is paid in ever-earlier dawns. Add to that this
week's brightening crescent moon, and sweet and sleepy will be the
order of the day: fine for precious days off and for morning snuggles,
not so good for commuting or for long afternoon meetings.

The usual westward creep of the constellations is enhanced by
lengthening twilights at this time of year, and I was surprised to
notice that Saturn has almost disappeared into the west. It lurks
down near the feet of Gemini now where it is washed pale by the
lingering sunset glow. Saturn sets completely by 9:30. Still high in
the southwest at sundown, brilliant Jupiter is two-stepping its way
into the western twilight sky leading Leo by a whisker.

The advance of the constellations is also bringing Scorpio and
Sagittarius rapidly into view. These quintessential summer star
patterns mark the center of the Milky Way. Rising at 10pm this week,
by the end of the month Sagittarius will be rising at 8pm and high in
the south by full dark. The bulk of the Milky Way sags eastward from
Sagittarius; look for it rising parallel to the eastern horizon by
midnight.

The persistent turn of Earth about Sun is bringing summer's familiar
constellations and weather patterns into view. Am I the same person
that saw these things last year? Yes and no. Each summer is unique.
Give me grace to live each day for its own merits.