"The Science Show" is a weekly program and podcast from
Radio Australia narrated by Robbin Williams, no connection to
the American actor of the same name.
On occasion, it is as dull as paint drying but other
times, it is utterly fascinating. This week is one of those
times.
There is a segment on the huge dinosaurs of Western
Australia, a working demonstration model of Alan Turing's
computational machine based on a theoretical paper he wrote in
1936, and the transit of Venus which is the main topic.
Here is the link to this podcast.
http://mpegmedia.abc.net.au/rn/podcast/2012/06/ssw_20120602.mp3
Those of you who call Australia home probably owe your
place of residence and language indirectly to the transit of
Venus.
When the Moon crosses the Sun or the Earth comes between
the Sun and the Moon, we call this an eclipse.
When a planet momentarily blocks the light from a star,
astronomers call this a "transit."
On either the evening of 5 June 2012 in the Western part
of North America or morning of 6 June in Australia, one
will be able to see Venus pass between
the Earth and the Sun.
This is not a spectacular eclipse-type event in which it
is black night in the middle of the day but rather a tiny black
dot which slowly moves across the disk of the Sun since Venus is
millions of miles or 1.6 times that in kilometers away from
Earth.
Those who can see the Venusian eclipse or transit need
to do so with extreme caution just as one would when viewing a
Solar eclipse. This means to project the image of the Sun on to
a white screen of some kind like a piece of paper or cardboard
and look at that rather than cooking your retina trying to look
directly at the Sun, even with Sunglasses.
Why should anybody care about the transit of Venus? If
you are asking that, it is a good question and here is why. The
sky at night doesn't change much from one moment to the next for
the average person looking up. Those tiny points of light which
are the stars and planets do move in relation to us, but they
move so slowly that it is like watching the hour hand on a
clock. The only time one can really get a good idea of what is
going on is when something like a planet momentarily blocks all
or part of the light from a star and casts a shadow.
We can then see how long it took for the light to return
and even tell if the planet that was blocking the light has an
atmosphere.
While Venus and Mercury have been transiting the Sun
since the dawn of time, we humans have only been aware that it
happens for around 400 years since Gala Leo developed
mathematics that allow us to predict where heavenly bodies will
be in relation to us indefinitely in to the future.
The Sun, Venus and Earth form a straight line on a
schedule that is like a very slow musical beat. Transits come in
pairs which are 8 years apart but there isn't another transit
until either 115 or 121 years have passed at which time, there
is another 8-year pair of transits.
This week's transit is the final one of a pair that
started in 2004 and there won't be another until 2117.
Now for why this matters to Australia. James Cook sailed
to Tahiti in 1769 to watch the predicted Venusian transit. He
saw it, wrote down a small description of what he saw and then
headed back to England and accidentally stumbled across
Australia.
Of course, Cook didn't sail all that way to see a little
black dot slide across the Sun, but was looking for something
much more important but the journey to Tahiti probably wouldn't
have happened had he not been advised about the transit.
Listen to the podcast and enjoy. I get it automatically
each week just to catch the really good shows when they come
along.
Martin
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