Tides

From: "Matthew Ota"
Subject: Article on Tides
Date: Tuesday, June 20, 2006 9:25 PM

I have been given a unique opportunity to write a newspaper article
on tides for a local beach newspaper, with a circuation of 70,000. Here
is the body of the text of the article (graphic diagram not included).
It took three revisions to do it as it evolved from an
astronomer-centric article to a layperson/beachgoer-centric article.
When I think of tides I visualize the earth, moon and sun as a whole.
When beachgoers think of tides they visualize water levels and changes
in the surf.

Note that in the first paragraph I was allowed to take a personal
stab at discrediting astrology...which is important to me. Also ,
despite my modesty they insisted on a short bigraphical paragraph. The
article is written for non-astronomers.

The body of the article follows:

What heavenly phenomenon exerts a force that is readily detectable
by people on the Earth? It is the tides. The tides are a manifestation
of gravitational forces generated by the Sun and the Moon. Unlike
astrology, it is the only true tangible non-electromagnetic force that
affects life on Earth (the stars and planets are too far away to
influence tides, or personal fortunes for that matter).

The Moon's gravitational pull causes the oceans to rise on opposite
sides of the Earth.
The ocean area closest to the moon is pulled toward the moon, and the
ocean area opposite appears to rise as it is left behind. The earth's
landmass itself is pulled toward the moon but only by a few
centimeters.

There is also a lag of the rise and fall in tides known as tidal
displacement. The Earth's 24-hour rotation causes the lag, as there is
a slight delay as the water adjusts to the Moon's tidal force.

The Sun also contributes to tidal forces, but only about half as
much as it is much farther away than the Moon. The Moon averages
250,000 miles in distance while the sun is 93,000,000 miles away.
However, despite this large distance, the Sun's tremendous
gravitational pull combines with the Moon's gravitational pull at new
moon and at full moon, when the Moon and the Sun line up. These tides
are called "spring tides", from the German language springen, to
spring up. These type of tides cause the highest water levels at the
beach.

When the Sun and the Moon are at an angle as seen from the Earth,
the gravitational forces are set at an angle so the tides are less
pronounced. These are called neap tides.

The portion of the Earth at a right angle to the gravitational pull
is where the water level is lowest, called the ebb tide. The water
recedes from the beach and is at its lowest level.

You can readily see the effects of tides at the Hermosa Beach pier
by looking at the pilings and noting the different levels of water
marks. When the tide is at ebb, you can see barnacles on the pier's
pilings and the high water marks on the rocks. You can also see a lot
of seaweed on the beach, as the ocean recedes to its farthest point.

At high tide, the water level is high, and the water comes closest to
the beachfront. Unknowing people who set up their beach towels and
chairs close the ocean at low tide may get a surprise later in the day
as the tide rises and the surf comes up over them.


Matthew Ota is an amateur astronomer that resides in Gardena,
California.

He currently is a 16 inch telescope operator at the Mount Wilson
Observatory. He also serves as a representative of the Jet Propulsion
Laboratory with the Saturn Observation Campaign, a Cassini/Huygens
outreach program. In addition, he is a long time member of the Orange
County Astronomers, serving as a trustee from 2005 through 2006. He is
known for his extensive and prolific astronomy public outreach
activities in Southern California, and is the newest member of the
South Bay Astronomical Society. He can be reached at ....
(email address here)

The South Bay Astronomical Society is the South Bay's
best-established astronomy club, based at El Camino College. The web
address is www.geocities.com/sbas_elcamino/


Compensation for this wrting effort....nada...ziltch, zero dollars. In
astronomy, there can be fame but no fortune.


--
The Lone Sidewalk Astronomer of Rosamond

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