North Carolina Trip Part I: Ocean Tides

This past week my family and I were vacationing in Emerald Isle, North Carolina.  It was a fantastic vacation and although we didn't specifically set out to find science, it was a vacation full of science.  Science was everywhere!  I would have posted earlier on this, but since I'm not a fan of broadcasting to the world that I'm away from my house and won't be back for days, I decided to wait.  Now that I'm back home I can post about our science experiences.  Given that there were so many, I'll divide them up into several blog posts over the next week or two.  If I combined everything into this post, you'd be reading for the next two hours.

We rented a beach house about 1/2 block from the Atlantic Ocean shore, so we spent at least part of each day on the beach.  One of the first things my daughter noticed was that the beach differed in size throughout the day.  Sometimes when we went to the beach there was a lot of sand, other times, not as much.  I realized this was an excellent opportunity to give her a crash course on lunar tides.  As an astrophysicist I have a clear understanding of how tides work, but living in land locked states my entire life I've never had a chance to directly witness this change.  I was just as amazed as my daughter.

If you're not clear on why we have tides on Earth, let me briefly explain.  Tides are result of gravitational forces between the Earth and the Moon.  Water will "bulge" toward (and away from) the Moon.  Rock also bulges, but not nearly as much.  There's a bit of lag in the bulge, so the height of the tide is not directly toward (or away) from the Moon, but that's a bit beyond the scope of this post.  So if there was no Moon, would we still have tides?  Many people have the misconception that the answer is no, that without the Moon, tides would not exist.  But the truth is that the Sun also plays a role.  The Sun's effect on tides is about 40% that of the Moon. Much less, but still significant.  Thus, even without the Moon, we'd still see ocean tides.

Original: JhbdelTranslation: Gianluigi [CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)]

As the image above shows, tides are stronger when the Earth, Moon, and Sun are aligned and weaker when they are not.  

My daughter is 5, so I simply explained to her that the Moon causes the water to reach higher/lower levels on the beach.  When she's older we'll discuss it further.  Another thing she noticed regarding high/low tide was the placement of sea shells.  She was very excited about searching for shells.  Depending on the tide, the waves dumped shells on different parts of the beach at different times.  

I thought it was very cool that a vacation to the beach naturally introduced my daughter to science.  And she asked questions which is one of the characteristics of a good scientist!

Tune in later for more vacation science.