Not so super 'super' moon...
On 19/03/2011 19:45, John Hall wrote:
In ,
David writes:
Now I don't know about anyone else, but the so-called 'super moon' didn't
look any bigger than loads of other moon rises I've witnessed.
The full-moon at moonrise often appears much bigger (and so does the sun at
sunrise).
OK, so it's also supposed to be closer to us in its orbit to boot, but I
reckon that extra closeness is not THAT close that you're going to be able
to visually notice the difference.
Eye-catcing it was... but no more eye-catching than many another moonrise at
full moon.
To me, it did seem noticeably larger and brighter than normal. That was
fifteen minutes ago, when it was already well away from the horizon. Of
course it could have been a psychological effect, since I knew that it
was supposed to be "super".
There are both real and psychological effects.
The moon's orbit is distinctly elliptical, so the moon's distance varies
significantly as it goes round. This can be shown by looking at solar
eclipses, which vary from the moon being large enough to completely
cover the sun for about 7 minutes at any given point, to "annular"
eclipses when even at mid-eclipse a ring of sunlight is left around the
moon's disk. Of course, the moon passes through "perigee" every month,
but it is only really noticeable when it occurs at full moon and our
satellite is displayed in full sunlit glory.
The shape of the moon's orbit also varies slightly due to gravitational
effects from the changing geometry of earth, moon and sun. This has
resulted in the orbit currently becoming slightly more elliptical than
normal, hence the slightly closer approach highlighted for tonight. The
earth's orbit and angle of the rotation axis also change in this way
over long timescales - these variations affect the distribution of solar
heating over the globe and a gentleman called Milankovitch showed how,
together with "feedback" effects, these variations could partly explain
the pattern of ice ages and interglacials.
The very real psychological effect is that the brain uses various cues
to estimate the size of objects very far away. Experiments with pairs
of drawings have shown that the brain can be "fooled" by a surprising
amount - an object seen close to the horizon providing a "scale" for it
seems larger than one high in the sky. And there have been any number
of incidents which demonstrate beyond all reasonable doubt that people
will believe almost any old tosh - and judge what they see and hear on
this basis - if they do not know or cannot understand the truth.
--
- Yokel -
Yokel posts via a spam-trap account which is not read.
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