We were given a lunar calendar for Christmas this year which is a really cool tool to have! We decided to display it near our tide tables since the moon plays a large role in the tides. I'm not sure about you but I've never known exactly HOW the moon affects the tides so I decided to do some research. As it turns out, NOAA has a great educational kit about tides online - I learned most of the following from their site.
Of course the moon is not the only factor that affects the tides - the sun affects them too - as well as wind and weather. However, since we received a lunar calendar and the moon seems to have the most effect on the tides, I'm only going to tackle the moon for now.
Of course the moon is not the only factor that affects the tides - the sun affects them too - as well as wind and weather. However, since we received a lunar calendar and the moon seems to have the most effect on the tides, I'm only going to tackle the moon for now.
After reading up on the NOAA site, my understanding is that tides are just really big waves that originate in the oceans and travel toward the continents (which affect the tides as well because the land gets in the way). The gravitational pull of the moon is what causes those waves. Whichever side of the earth is facing the moon has a bulge or peak of this huge wave due to the gravitational pull from the moon. Conversely, there is also a bulge on the exact opposite side of the earth at that point because where gravity won out over inertia on the other side, inertia wins out on the side facing away from the moon. Basically, every time our side of the earth faces the moon, it starts a high tidal wave in our area. But how does it work out to twice a day?
Maybe it's just me, but I really only have ever paid attention to the 24 hour solar cycle and haven't mentally retained any other cycle lengths such as the Lunar cycle (amount of time for the moon to revolve around the earth) which is 24 hours and 50 minutes. If you divide that in half (one for facing the moon and one for facing the opposite direction), you get 12 hours and 25 minutes which allows you to have almost two full sets of tides in every day - also known as semidiurnal tides. Theoretically, this would be the same around the earth but since there are large continents that don't allow the water to flow freely, it's not the case. The west coast of the US has a mixture of semidiurnal tides and diurnal tides - only one full set of tide per day. Here in the Chesapeake, we have semidiurnal tides as does the entire east coast.
The supplemental information that came with the lunar calendar only had one piece that pertained to tides - the perigee and apogee. Perigee is the point in the moon's elliptical path around the earth where it is closest to the earth and Apogee is the point where it is furthest from the earth. At these two times in the moon's orbit, high tides can be higher than normal and low tides can be lower than normal. The tides can be also be exaggerated when we have a new and full moon because the moon and earth are lined up with the sun.
After reading and understanding the changes the Lunar cycle has on tides, I’m interested to see what the additional effects the Sun and weather have as well… stay tuned!
The supplemental information that came with the lunar calendar only had one piece that pertained to tides - the perigee and apogee. Perigee is the point in the moon's elliptical path around the earth where it is closest to the earth and Apogee is the point where it is furthest from the earth. At these two times in the moon's orbit, high tides can be higher than normal and low tides can be lower than normal. The tides can be also be exaggerated when we have a new and full moon because the moon and earth are lined up with the sun.
After reading and understanding the changes the Lunar cycle has on tides, I’m interested to see what the additional effects the Sun and weather have as well… stay tuned!
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