Think about it. What is the one truly unique spectacle of a total solar
eclipse?
So everything will go dark.
The night flowers will bloom, the
bats will come out and the birds will fly home. We see that happen
every day, or night
rather.
So you'll see lots of people
looking up into the sky through
strange looking glasses. Weird, maybe, but you could also probably
see that at your
local UFO communion group.
The one feature that only
becomes visible during a total solar eclipse is the
outer region of the sun, especially the corona, which can be seen as
a gorgeous,
pearly white halo billowing out from the darkened disk.
This rarefied region of excited
gas floats millions of kilometres above the
sun's surface and is held in place by the sun's powerful magnetic field.
Its
ethereal glow is usually obscured by the brilliance of the sun itself.
This means we don't know
a lot about it. In some ways, we know the inner
workings of the sun better than we know its outer layers.
What baffles astronomers
about the solar ``crown' is that it's hot. Too hot.
Hotter than the surface of the sun itself.
Finding out why could be
quite useful, because it may have something to do with
solar weather patterns. The sun actually has some pretty nasty weather
and, far
away though the Earth may be, we are still caught in its not-so-icy
grip.
Begin at the beginning, deep
inside the core of this momentous ball of gas,
where nuclear reactions are generating temperatures of around 15 million
degrees
and producing power equal to about 80,000,000,000,000,000 of the largest
power
plants made by Earthlings.
These reactions also produce
photons, units of light. Photons travel fast.
There's nothing faster. They only take about eight and a half minutes
to travel
from the sun to the earth.
But it turns out the hardest
part of the journey is simply getting from the
core of the sun to its surface.
It would only take a few
seconds if they travelled in a straight line. But it's
crowded in there, and the photons are always bumping into things, rather
like,
say, driving a car around the Victory Monument during a rush hour traffic
jam.
So instead of seconds, it
takes photons millions of years to get out to the
sun's surface (sound familiar?), a region known as the photosphere.
This is the
area blocked by the moon during an eclipse, and things are much cooler
there:
it's only about 5,000 degrees.
But then something odd happens.
Just above the surface lies the chromosphere _
which can also be seen during a total eclipse as a red glow around
the moon _
and here the temperature starts to rise again.
And by the time they hit
the corona, it's suddenly back up to 1-2 million
degrees. It's kind of like biting into mouthful of phrik kee nuu while
eating a
bland dish of khao pat.
Astronomers speculate this
heat may come at the tail end of shock waves roaring
through the chromosphere, like the crack at the end of a whip. Or it
may be a
result of tangled magnetic fields caused by sunspots erupting into
solar flares.
For the sun's surface turns
out be a regular cauldron of storms and spicules,
flares and flocculi which stream out into space and wreak havoc on
our own climate.
Solar flares have been known
to wreak havoc on radio and telephone communications and power lines. They
are a wonderful excuse when you don't want to
talk to somebody (``What's that, honey? I can't hear you. It must be
the
solar flare activity').
Like much of the sun's weather,
flares are probably related to sunspots _
regions on the surface which appear dark because they are cooler than
the
surrounding area.
Sunspots generally come and
go in 11-year cycles. During an episode of very low
sunspot activity 300 years ago, northern Europe experienced an abnormally
cold
period known as the Little Ice Age.
The level of sunspot activity
is thought to influence the shape of the corona,
which is continually shifting. During a sunspot maximum, long, pale
streamers
can be seen riding off into the blue-black sky. But we are now near
a minimum,
so the corona will probably appear more like a ring, perhaps broken
by
petal-like baubles of mist.
Even if you don't manage
to catch a glimpse of the haloes and flares emanating
from the sun on Tuesday, one day you may still be able to see another
feature of
space weather: the solar wind.
This steady stream of charged
particles flowing out of the sun creates some of
the most beautiful sights in our solar system. It causes comets to
relinquish
their tails. And it buffets the Earth, sparking off the eery curtains
of glowing
gas known as the Northern and Southern Lights.
The solar wind may even be
our ticket out of this place. Space travel en
thusiasts have suggested building giant sailboats to harness the celestial
breeze.
Who knows, some day we may
be able to simply tack our way to the stars.
Wishing for magic from the eclipseb This editorial was quoted verbatim
by UPI!
Ah, how nice it must have been in the good old days.
Back then, there was no need
for international conferences, UN blue berets and
complicated treaties to keep the peace. Instead, there was good old-fashioned
fear of the heavens.
Herodotus, the ancient Greek
historian, recounts how two warring tribes who had
fought for six years suddenly decided to lay down their arms when they
witnessed
``the day turned into night'.
If only the eclipse of 1995,
due next Tuesday, would have such a powerful
effect as it sweeps across the strife-torn lands of Afghanistan, Burma
and Cambodia.
Unfortunately, soldiers bathing
in the moon's shadow are far more likely to
fire off their weapons than lay them down. Cambodian authorities have
reportedly
given strict orders for soldiers not to shoot at the blackened disk,
lest they
scare off the tourists.
Even in the days of yore, eclipses may have helped cause some bloodshed.
Chinese history is a bit
vague on this point, but it seems that the legendary
emperor Yao sent off some emissaries, including a semidivine pair named
Hsi and
Ho, to the four corners of the world to prevent the moon from obstructing
the sun.
Of course, they didn't do
a very good job of it (rumour has it they were too
busy drinking). So around the second millenium BCE, King Chung K'ang
decided to
dispatch some troops to teach them a lesson.
Okay, so maybe the good old days weren't all they were cracked up to be.
The point is, an eclipse
has always managed to stir mankind's imagination. In
our history, literature and our myths, they hold a fabled place.
The much-beloved cartoon
character Tintin once used an eclipse to wow the
locals who had him tied to a stake, while in real life the much-beloved
King
Rama IV used an eclipse to impress the foreigners who had designs on
Siam's bounty.
We don't know if King Mongkut's
astronomical prowess really helped prevent the
colonization of Siam. But it sure is nice to think so.
Certainly, there is no doubt
that the real story of his death _ he caught
malaria during the eclipse expedition to Prachuab Khiri Khan _ is far
more
romantic than the silly heartsick demise of Yul Brynner in that play
we won't
bother to name.
Times have changed. Now,
with the help of modern science and technology,
virtually everyone knows just when and where the moon will block out
the sun,
and can safely observe the event themselves (don't forget that special
pair of
shades).
Does an eclipse still have
meaning? Is it to become nothing more than a banal
tourist attraction? Has progress once again robbed us of all supernatural
thrill?
Not necessarily. The message
is different now. A total eclipse of the sun is
now a spectacle of Nature, still awesome if well understood. The hair
will still
rise on our necks as the day turns to our night, and touches off our
primordial
fear of darkness.
An eclipse is perhaps a sign
that we should not take anything for granted, not
even something as basic as the sun shining down from the heavens. An
omen
signifying that some things remain well beyond our control.
We don't have to look all
the way into space to be humbled. No one will be more
keen to appease the gods of good weather than the hordes rushing to
seek totality.
How ironic if, despite all
our knowledge and anticipation, Nature had the last
laugh and it turns cloudy on Tuesday.
We've all heard of a rain dance. Does anybody know a prayer for clear skies?
From Thailand to ancient Greece, few astronomical events have managed
to thrill mankind quite like a total eclipse of the sun.
Throughout history, the eery
experience of watching the day suddenly turn to
night has helped to end wars, change the course of nations, and prove
mind-blowing scientific theories.
But it won't always be this way, astronomers warn.
Slowly but surely, the moon
is moving away from the Earth. One day, total solar
eclipses will be a thing of the past.
That will be a pity, because
as it stands the Earth-Moon system is unique in
the solar system, and thus _ for all we know _ the universe (astronomers
have
only just announced finding evidence of a new planet in a nearby solar
system,
see page ).
Ours is the only planet with
a satellite whose angular size _ as seen from the
surface _ exactly matches the angular size of the sun. Put another
way, the moon
is both 400 times smaller than the sun and 400 times closer to the
Earth.
So perhaps it is appropriate
that such a unique spectacle should
have had such a big impact on human affairs.
The first definite human
record of a solar eclipse comes from Chinese oracle
bones which documented the moon blocking the sun in the year 1217 BCE.
But the most famous ancient
eclipse occurred in Greece in the year 585 BCE,
when a lunar transit of the sun brought an end to a bitter and long-fought
war
between the Lydians and the Medes.
``They were still warring
with equal success, when it happened,
at an encounter which occurred in the sixth year, that during the battle
the day was
suddenly turned to night,' wrote the historian Herodotus.
``So when the Lydians and
Medes saw the day turned to night,
they stopped fighting, and both were the more eager to make peace.'
The eclipse was actually
foretold by a certain Thales of Miletus, an astronomer
and philosopher who was considered ``wise but not prudent'. Plato recounted
a
story whereby Thales actually fell into a well because he was so busy
examining
the stars above.
More recently, of course,
His Majesty King Rama IV of Siam predicted an eclipse
would occur in the province of Prachuab Khiri Khan in the year 1868,
and invited
the English and French ambassadors to come witness it with him.
The envoys were duly impressed,
although whether _ as legend has it _ the
episode actually helped stave off colonization is a matter of historical
debate.
HM King Rama IV died a few
months later from an illness caught while observing
the celestial phenomenon.
In this century, the contributions made by eclipses have been largely scientific. In particular, they were pivotal in proving one of the most important scientific theories of all time: Einstein's Theory of General Relativity.
One of the key features of
general relativity is that anything that has energy
also has mass (e=mc¢). Einstein therefore predicted that light
could actually be
bent by gravity.
It takes a lot of gravity, however, to bend light even a little bit, so scientists turned to the heavens for proof.
In 1919, just four years
after Einstein had published his theory, astronomer
Sir Arthur Eddington of the Royal Greenwich Observatory led a momentous
expedition to the island of Principe off the coast of West Africa in
order to
observe an eclipse.
While the sun was obscured,
he and his colleagues were able to record the
position of stars which at the time could be seen near the sun.
Six months later, when the
Earth had moved to the other side of the sun, the
same stars were visible at night, well away from the sun.
Their positions were again
checked, and found to be slightly different,
indicating that as the light from the stars had travelled past the
sun to the earth, it had been slightly bent by the sun's vast gravitational
pull.
So Einstein was right. For
the first time, his theory of general relativity was
confirmed.
Total solar eclipses won't be with us forever, however.
The moon is believed to have
originally been an interplanetary interloper which
was captured by the Earth. This violent capture may even have created
the tilt
in the Earth's axis, thus making the seasons as we know them.
We do know for sure that
as the moon pushes and pulls the Earth's tides, energy
is lost in the form of friction and the moon's orbit gradually grows
larger.
This means the size of the
moon as seen from the Earth is gradually growing
smaller. When it grows so small as to only block out 98 per cent of
the sun's
disk during totality, the day will no longer turn to night.
How long have we got? Well,
according to astronomer Dr Sten Odenwald, if the
sun's diameter is 1.45 million kms, and the moon's diameter is 3,476
kms, and
the moon is receding from the Earth at a rate of about 2 cms per year...
Better hurry up. You only
have another billion years or so to see a total
eclipse of the sun.