Thursday, September 30, 2010

Shellpot Creek just starting to fill up from the rain - video

Shellpot Creek is only just getting started today. If Tropical Storm Nicole drops the 2 to 4 inches expected then this creek will rise higher.

The rain will be good to flush out the creek anyway. We just don't need a flood of the backyard like earlier in the summer.

Tuesday, September 28, 2010

US Religious Knowledge Survey and Quiz

The Pew Forum on Religion and Public Life released a new survey of religious knowledge on Tuesday. From the summary:

"Atheists and agnostics, Jews and Mormons are among the highest-scoring groups on a new survey of religious knowledge, outperforming evangelical Protestants, mainline Protestants and Catholics on questions about the core teachings, history and leading figures of major world religions.

On average, Americans correctly answer 16 of the 32 religious knowledge questions on the survey by the Pew Research Center’s Forum on Religion & Public Life. Atheists and agnostics average 20.9 correct answers. Jews and Mormons do about as well, averaging 20.5 and 20.3 correct answers, respectively. Protestants as a whole average 16 correct answers; Catholics as a whole, 14.7. Atheists and agnostics, Jews and Mormons perform better than other groups on the survey even after controlling for differing levels of education."

There is a quiz you can take to test your religious knowledge. I got 15 our of 15 even with the last question being a very difficult one that I didn't quite know the answer to, but I knew the subject matter so I was able to eliminate answers that couldn't have been correct. The average on the quiz is 50%, which I think is abysmal. Results of quizzes for 3412 nationally representative adults are below.

When I reviewed the number correct for different religious affiliations I realized that people were not even getting the 33% correct that would be expected from random guessing. This means people think their incorrect answers are the right answers for the questions. Are they being taught incorrectly? That needs to be fixed. It might be important to know that a country is predominantly Muslim or the religious holidays of a group that has a disproportionate affect on foreign policy.

Why doesn't Pew ever call me? After the poll they should tell the people the correct answers so they learn something.

Sunday, September 12, 2010

Measuring Shellpot Creek Stream Flow with a Leaf

Before today's rain, the Shellpot Creek has been so low due to the lack of rain that it has contracted down to flowing through a few inch wide cleft in the rocks on the stream bed in the middle of the picture below.

Here is the cleft:

The width is about 3.25 inches:

The depth is 2 inches, the ruler I used goes to 16 inches on the right side and 14 inches is just visible below.

I realized that such a controlled situation would allow me to measure the stream flow with a ruler and something like a leaf floating in the water to get the flow velocity of the surface. I used my camera and flip video to capture the measurements and as a timer for the flow. I repositioned the ruler and used an imaginary line drawn from the cleft in the rock to the ruler edge. This distance is 5.25 inches. I then used the flip video snapshot function to find the exact frame the leaf first crosses the imaginary line at the cleft in the rock and the exact frame the leaf just touches the ruler at the other end (leaf and red lines below).

There are 30 frames/second in the video. I got 10 successful measurements from 14 leaf drops, ranging from 23 frames to 40 frames, corresponding to an average of 5.59 inches/second +/s 15% for the velocity of the leaf and thus for the velocity of the top of the water.

I pieced them all together in the following video.

Without doing the extra work that would be required given the fluid mechanics of the situation we are going to assume that the channel is rectangular and that I have measured the maximum velocity of the fluid. That corresponds to the right hand side of the chart below.

If we assume a linear velocity profile the average velocity is 5.59 inches/sec multiplied by a 2 inch depth and a 3.25 in width to get 36.3 cubic inches/sec for the flow. In reality the velocity profile is more parabolic like the right hand side of the diagram above and the average velocity is higher. Also, the channel is not smooth on the sides or the bottom, because of pebbles and stones and even the cross section will not be regular. Close examination of the video of the leaves floating by shows that they often go fast on the right hand side of the flow of the creek and slower on the left hand side, giving another clue that the velocity profile isn't simple.

Thus I feel like I have measured more of a lower bound for the flowrate. What would my readers do differently?

Wednesday, September 08, 2010

Name the ten largest cities in Pennsylvania - quiz

Mental Floss has a quiz to name the ten largest cities in Pennsylvania in 5 minutes. No choices you just have to type them in. I only got 8, though the quiz declares that anything over 6 would be considered a win. The stats when I took it said that of 1542 people took it with an average score of 53%.

As a former Pennsylvanian who is from the Philadelphia area but went to Pittsburgh for college, I should have gotten all ten. I have been to the eastern one of the two I missed. The other was in the west. Good Luck.

Take the quiz here.

How well can you do?

Monday, September 06, 2010

Polar Bear Swimming at the Lincoln Park Zoo in Chicago

We went to the Lincoln Park Zoo in Chicago as part of our vacation in August. This Polar bear was having a cooler time than us swimming in the pool of his enclosure.

Except for the fact that he would have eaten me, I would have jumped in there with him.

Caterpillars eating a sunflower

I am not sure what species these caterpillars are, but they seem to love eating the petals on the lone sunflower out in the front garden.

I think the sunflower is a second or third generation of seeds from flowers from earlier seeds we planted a few years ago. usually the groundhog snips them off before they get to grow.