Spring Tides

In a discussion of tides recently it was asserted that the spring tides
occurring at the full moon always had a bigger range than those at the new
moon. I don't know the answer, but I expect some guru on URS
will............. I await!

"Duncan Heenan" wrote in message
...
| In a discussion of tides recently it was asserted that the spring tides
| occurring at the full moon always had a bigger range than those at the new
| moon. I don't know the answer, but I expect some guru on URS
| will............. I await!
|

In general, the tides at new and full moon are not equal, but sometimes it
is range at new moon which is larger, sometimes that at full.

I cannot remember seeing a full explanation, but the main cause is most
likely to be the eccentricity of the moon's orbit. The moon's distance from
us varies significantly through the month and this would result in a
variation of the gravitational force which produces the tides.
--
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"Yokel" now posts via a spam-trap account.
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Yokel wrote:
"Duncan Heenan" wrote in message
...
| In a discussion of tides recently it was asserted that the spring tides
| occurring at the full moon always had a bigger range than those at the new
| moon. I don't know the answer, but I expect some guru on URS
| will............. I await!
|

In general, the tides at new and full moon are not equal, but sometimes it
is range at new moon which is larger, sometimes that at full.

I cannot remember seeing a full explanation, but the main cause is most
likely to be the eccentricity of the moon's orbit. The moon's distance from
us varies significantly through the month and this would result in a
variation of the gravitational force which produces the tides.

There also is a suntide , and you have to add both,
that gives you all sorts of levels, because they are
not in sync(sun 1 day, moon 1/28th different).
Suntide is moontide, so the summ is mainly locked
to the moon.
I do not think that the shape of the moon orbit
has much influence.

Yokel wrote:
I cannot remember seeing a full explanation,

http://astunit.com/tutorials/tides.htm

Best,
Stephen

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Sjouke Burry wrote:

Yokel wrote:
I cannot remember seeing a full explanation, but the main cause is most
likely to be the eccentricity of the moon's orbit. The moon's distance
from us varies significantly through the month and this would result in a
variation of the gravitational force which produces the tides.

There also is a suntide , and you have to add both,
that gives you all sorts of levels, because they are
not in sync(sun 1 day, moon 1/28th different).
Suntide is moontide, so the summ is mainly locked
to the moon.
I do not think that the shape of the moon orbit
has much influence.

The shape of the moon's orbit has an enormous influence because
it means there is a significant variation in the Earth/Moon
distance. The tidal force in inversely proportional to the
cube of the distance, and the contribution due to eccentricity
is nearly half as strong as the contribution from the sun.

Wasn't it Ronald Raygun who wrote:
Sjouke Burry wrote:

Yokel wrote:
I cannot remember seeing a full explanation, but the main cause is most
likely to be the eccentricity of the moon's orbit. The moon's distance
from us varies significantly through the month and this would result in a
variation of the gravitational force which produces the tides.

There also is a suntide , and you have to add both,
that gives you all sorts of levels, because they are
not in sync(sun 1 day, moon 1/28th different).
Suntide is moontide, so the summ is mainly locked
to the moon.
I do not think that the shape of the moon orbit
has much influence.

The shape of the moon's orbit has an enormous influence because
it means there is a significant variation in the Earth/Moon
distance. The tidal force in inversely proportional to the
cube of the distance, and the contribution due to eccentricity
is nearly half as strong as the contribution from the sun.

So I'd therefore expect the strength of the spring tide force to be
seasonal. The strongest force occurring at spring tides which occur near
lunar perigee. That would be at new moon in February and full moon in
August. At February new moon, the Earth is closer to perihelion, so the
solar tide would be slightly enhanced, making that the biggest tidal
force of the year.

--
Mike Williams
Gentleman of Leisure

Mike Williams wrote:

Wasn't it Ronald Raygun who wrote:

The shape of the moon's orbit has an enormous influence because
it means there is a significant variation in the Earth/Moon
distance. The tidal force in inversely proportional to the
cube of the distance, and the contribution due to eccentricity
is nearly half as strong as the contribution from the sun.

So I'd therefore expect the strength of the spring tide force to be
seasonal. The strongest force occurring at spring tides which occur near
lunar perigee. That would be at new moon in February and full moon in
August.

Indeed (actually January and July are closer than February and August,
according to http://www.fourmilab.ch/earthview/pacalc.html).

At February new moon, the Earth is closer to perihelion, so the
solar tide would be slightly enhanced, making that the biggest tidal
force of the year.

Indeed, with the emphasis on "slightly": The eccentricity of Earth's
orbit is much less than that of the Moon's (about a quarter), and so
the perihelion's effect is much less noticeable than that of perigee
(about a sixtieth).

Also, the biggest tidal forces don't directly translate to the
biggest tidal ranges, because ranges are influenced by other
factors too, notably the fact that just because the lunar and
solar forces are in phase at the exact moments of new and full
moon, they may no longer be in phase by the time the oscillations
they fuel have propagated to any particular site of observation,
since they travel at different speeds due to their different
frequencies. There are other harmonics, and their phases, to
consider too.