## The First Three Minutes – interim assignment

For those reading The First Three Minutes with me – there are a number of black-and-white pictures in the book which were originally published in 1977.  While impressive for the time, you now carry better cameras in your pocket than were used by the most advanced researchers then.

A possibly interesting and useful mini-project might be to find and collect higher-resolution images of the pictures in the book.  They might be the same images as the original, or newer.  In particular, color images of the galaxies and various spectra mentioned.

## B/C Creative Writing 1st Draft Date

If you are working on a creative writing piece, I would like to see a rough draft by Tuesday the 20th.  I will give you feedback soon after that.  After you fine tune this writing, please put it on your personal blog.

## Time and Tide wait for no Physics Teacher

The study of Physics is the study of our Universe, and how the things within it interact with one another.  The Universe is a complex place, and therefore its description is likewise complex.  To begin to understand its workings, we often strip a situation down to its simplest state, and add back in complexities as our understanding increases.  Unfortunately, this can be confusing to the student, as it asks them to imagine a situation which they *know* to be untrue (i.e. “what if there were no friction or air resistance”)

http://xkcd.com/669/

In their simplest explanation, high and low ocean tides are caused primarily by the gravitational force the Moon exerts on the Earth, and the fact that the force is a bit less on the side furthest from the Moon (this is also what is being referred to when someone mentions “being ripped apart by tidal forces” either in science fiction or science fact.)

The Sun, of course, also exerts tidal forces on the Earth, though due to the much greater distance between the bodies, the differences in forces are smaller; the tidal effects of the Sun are most noticeable in conjunction or opposition with the effects from the Moon.

 “Together, the gravitational pull of the moon and the sun affect the Earth’s tides on a monthly basis. When the sun, moon, and Earth are in alignment (at the time of the new or full moon), the solar tide has an additive effect on the lunar tide, creating extra-high high tides, and very low, low tides — both commonly called spring tides. One week later, when the sun and moon are at right angles to each other, the solar tide partially cancels out the lunar tide and produces moderate tides known as neap tides. During each lunar month, two sets of spring and two sets of neap tides occur (Sumich, J.L., 1996).”

So, Saturday September 10, at approximately 5 pm: the Sun is setting in the west (as it does), and a half moon is high in the sky, nearly at its zenith. We should be nearly at a high neap tide, with low tide occurring around midnight, and another high tide about 6 in the morning, yes?

Nope.

Spring tides. Low tide at 6:30pm. Only one high and one low tide per day. This is *not* the way the tides are supposed to work, and it’s North America’s fault…though South America certainly isn’t helping any.

The Continents mess things up.  Due to Earth’s rotation, they push the water ahead of them so the tidal bulges precede the moon rather than lag behind.  Coastal irregularities put a local spin on a global phenomenon.  The Bay of Fundy in Nova Scotia has the world’s highest high tides. The Gulf of Mexico experiences only one high and one low tide per day.

“This map shows the geographic distribution of different tidal cycles. Coastal areas experiencing diurnal tides are yellow, areas experiencing semidiurnal tides are red and regions with mixed semidiurnal tides are outlined in blue.”