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| Solar noon from the downtown library. The length of the short arm of the shadow indicates a solar altitude of 84.9 degrees. Its direction indicates true north. |
Sunday, June 8, 2014
Saturday, May 24, 2014
Fact check: Florida youth suicide rate
I came across an odd side-note in Michael Gannon's Short History of Florida (1992, updated 2003) on pages 147-8 which reads: "Civic and religious spokespersons began talking in earnest about the need to protect, nurture, and guide Florida's young, all the more so when it became known that the state had the nation's highest youth suicide rate."
Gannon provides no reference for this statement, but I happen to know the CDC publishes detailed mortality statistics for every state in the nation all the way back to 1968. Their "Wonder" online database application allows you to break down these data by age group and use them to rank the states. Of course Florida never had the highest rate for youths ages 15-24 (that distinction belongs principally to Alaska) but I assume Gannon meant Florida was highest among the 20 most populous states.
By that measure Florida indeed was #1 in the years 1980 and 81, but those were the only two years I could find that true. Florida ranked #2 in 1969, 75, 84, and 96. It ranked #3 in 1970, 74, and 82. In the 90s we ranked mostly between 5-10th place, and in the 2000s we ranked mostly 10-15th place, as adjusted to the nearest census year.
Florida has an extraordinarily high suicide rate in the 55-and-up age group, however, ranking in the top 3 for every year I checked including 2010, the most recent year for which data were available. With 1,151 suicides we were second only to California in number of deaths, and second only to Arizona (371 deaths) in terms of crude rate per 100,000 in population.
That aside, the point Gannon seemed to be making is that Florida didn't take very good care of its kids in the late 20th century, which can be confirmed through other measures like the Annie E. Casey Foundation's "Kids Count" Data Book, published since 1989, which ranks the states based on a variety of measures of child well-being. Florida spent many years in the bottom 5 of that last list, but has since climbed up to the mid-30s, on a scale from 50 to 1 where 50 is the worst (New Mexico) and 1 is the best (New Hampshire). For the complete 2013 list see page 16 of this PDF file: http://www.aecf.org/~/media/Pubs/Initiatives/KIDS%20COUNT/123/2013KIDSCOUNTDataBook/2013KIDSCOUNTDataBookr.pdf
Monday, April 21, 2014
Friday, April 18, 2014
Wednesday, April 16, 2014
Tampa's Pride
[Commissioner] Victor Crist unsuccessfully sought formal assurances that the vote would not result in Hillsborough County supporting obscene, prurient events not appropriate for families.
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| Gasparilla 1968 Florida Archives |
"The festivals, the activities and things need to have a little different tone to them," said Crist, a Republican. "Parading around in lingerie, pasties, g-strings and outfits that promote your sexual organs is not necessarily an appropriate thing to do in Hillsborough County."
"That's Gasparilla," a member of the audience replied, bringing laughter.
June 5, 2013 Tampa Bay Times
Saturday, April 5, 2014
Solar Mysteries Resolved
If you're reading this please send me a note. I hate lurkers. I really, really hate them. That said, I'm now going to experiment with producing original content:
Mystery #1: The ultraviolet "danger zone"
The ultraviolet "danger times" are often given as "2 hours before and 4 hours after noon." This could lead a reasonable person to presume that UV is somehow less dangerous in the morning than it is in the afternoon. The reality is the recommendation has more to do with politics than it does with science.
Science tells us the danger period is roughly 2 hours before and after solar noon. Solar noon rarely occurs at the same time as noon on a standard clock for several reasons. For one, the time zones have been re-drawn for political reasons so it's possible for you to live in a place that's very far from the longitude nearest to your solar noon time. Second, even after correcting for time zones, solar noon itself varies throughout the year by up to 30 minutes thanks to our elliptical orbit and a few other factors. So to account for this the CDC bumped up the times to 3 hours before and after clock noon as a rule-of-thumb.
The problem most relevant to the morning/afternoon asymmetry, however, is that we observe Daylight Saving Time in the U.S. during most of the year, which puts solar noon off by an additional hour for most people. Instead of expanding the danger times further, the CDC simply shifted them ahead by one hour to match DST. This is probably best because UV tends to get more press coverage in the summer months, and after all it's only a rule-of-thumb. OK, but a rule-of-thumb that can lead reasonable people to form erroneous assumptions about the sun. Furthermore, UV can actually be more dangerous in winter, particularly at high altitudes and in the presence of snow.
Mystery #2: The sun overhead
While walking home the other day I was irritated that the sun appeared to be shining on the north sides of buildings as I passed by. It was my understanding that when one lives above the tropic of cancer the sun is never directly overhead. I interpreted this to mean that buildings north of the tropics must always have a shadow on their north face. I happened to know the street I was walking on was built along a TRS line, however, and therefore was very precisely a north-south road. So, what was going on?
It turns out my interpretation is only partially correct. A building north of the tropics will only always have a shadow at solar noon. On the summer solstice in Tampa this shadow can be as small as 5 degrees as measured from the top of the building. As the sun sweeps an arc across the sky on the solstice, its compass position can pass up to 28 degrees north of the east-west line. This occurs from 6:30 AM to 11:00 AM and from 4:00 PM to 8:30 PM on that day, when its azimuth is less than 90 or greater than 270 degrees, and its elevation is less than 60 degrees.
So on summer evenings in Tampa there is likely more shade to be found on the south side of a building than there is on the north side, a handy thing to know for people who fear the sun.
Mystery #3: The analemma
A circle has one center, an ellipse has two. Our orbit around the sun is an ellipse with two centers. The sun occupies one center, and the other is empty space. The gravity of the sun is what's swinging us around the ellipse, however, and so we are moving faster when we're closer to it, and slower when we're closer to empty space.
An analemma is a plot of where the sun appears in the sky at clock noon every day for a year. The distance from the top to the bottom of the chart represents the distance between the tropics of capricorn and cancer. Using the chart we can tell when the apparent motion of the sun in the sky is moving "fast" or "slow" and therefore gives us an earlier or later solar noon reading relative to clock time.
It also happens that the analemma forms a pleasant shape which is suitable for placing on the sides of globes, particularly in the vast boring empty stretches around the Pacific ocean. It also makes for a neat year-long composite camera image for people with patience and good timing.
Mystery #4: UVA is NOT harmless, and it's everywhere
UVC is the nightmare radiation that seeps through the ozone hole. Most people don't get this without cooking themselves nude on a beach at solar noon on the summer solstice. UVB is the more familiar type that causes sunburn when you stay out too long without sunscreen on a sunny day.
UVA, however, is the stuff that goes right through your sunscreen, your clothes, and into the deeper layers of your skin. It goes through clouds, it goes through glass, it goes through just about everything that isn't opaque. Furthermore, because it penetrates the skin it is the radiation that causes the wonderful long-lasting deep glowing tan hawked as "safe" by tanning salons. The problem is because it operates at the structural level of the skin, it tends to cause the sort of loosening and wrinkling damage associated with aged skin. Second, if you're going to get cancer from ultraviolet exposure, then you want to have it on the surface where UVB operates, because those tumors are slow-growing and easily removed. If you get cancer deep in your skin, then it will often grow faster, making it harder to get at and remove before it spreads to other body parts and kills you.
Now for the freaky part. UVA is EVERYWHERE. You cannot escape it. If you can see light, even if it's an artificial light, then you're probably getting a measurable dose of UVA. If there is enough sun outside to necessitate wearing sunglasses, then you're probably getting dosed with UVA and B. If you're watching the sunset you're getting UVA. If you're working under fluorescent lights you're getting UVA. If you're staring at a monitor, then UVA could be getting into your eyes (such screens are normally polarized...I don't know how that affects it) My feeling is the new LED bulbs in the warm range probably emit the least UVA, but I don't know for sure. I'm also unclear on which bits of the spectrum are more likely to be reflected off cement pavement, or that will bounce around the margins of curtains to get inside your home.
Mystery #1: The ultraviolet "danger zone"
The ultraviolet "danger times" are often given as "2 hours before and 4 hours after noon." This could lead a reasonable person to presume that UV is somehow less dangerous in the morning than it is in the afternoon. The reality is the recommendation has more to do with politics than it does with science.
Science tells us the danger period is roughly 2 hours before and after solar noon. Solar noon rarely occurs at the same time as noon on a standard clock for several reasons. For one, the time zones have been re-drawn for political reasons so it's possible for you to live in a place that's very far from the longitude nearest to your solar noon time. Second, even after correcting for time zones, solar noon itself varies throughout the year by up to 30 minutes thanks to our elliptical orbit and a few other factors. So to account for this the CDC bumped up the times to 3 hours before and after clock noon as a rule-of-thumb.
The problem most relevant to the morning/afternoon asymmetry, however, is that we observe Daylight Saving Time in the U.S. during most of the year, which puts solar noon off by an additional hour for most people. Instead of expanding the danger times further, the CDC simply shifted them ahead by one hour to match DST. This is probably best because UV tends to get more press coverage in the summer months, and after all it's only a rule-of-thumb. OK, but a rule-of-thumb that can lead reasonable people to form erroneous assumptions about the sun. Furthermore, UV can actually be more dangerous in winter, particularly at high altitudes and in the presence of snow.
Mystery #2: The sun overhead
While walking home the other day I was irritated that the sun appeared to be shining on the north sides of buildings as I passed by. It was my understanding that when one lives above the tropic of cancer the sun is never directly overhead. I interpreted this to mean that buildings north of the tropics must always have a shadow on their north face. I happened to know the street I was walking on was built along a TRS line, however, and therefore was very precisely a north-south road. So, what was going on?
It turns out my interpretation is only partially correct. A building north of the tropics will only always have a shadow at solar noon. On the summer solstice in Tampa this shadow can be as small as 5 degrees as measured from the top of the building. As the sun sweeps an arc across the sky on the solstice, its compass position can pass up to 28 degrees north of the east-west line. This occurs from 6:30 AM to 11:00 AM and from 4:00 PM to 8:30 PM on that day, when its azimuth is less than 90 or greater than 270 degrees, and its elevation is less than 60 degrees.
So on summer evenings in Tampa there is likely more shade to be found on the south side of a building than there is on the north side, a handy thing to know for people who fear the sun.
Mystery #3: The analemma
A circle has one center, an ellipse has two. Our orbit around the sun is an ellipse with two centers. The sun occupies one center, and the other is empty space. The gravity of the sun is what's swinging us around the ellipse, however, and so we are moving faster when we're closer to it, and slower when we're closer to empty space.
An analemma is a plot of where the sun appears in the sky at clock noon every day for a year. The distance from the top to the bottom of the chart represents the distance between the tropics of capricorn and cancer. Using the chart we can tell when the apparent motion of the sun in the sky is moving "fast" or "slow" and therefore gives us an earlier or later solar noon reading relative to clock time.
It also happens that the analemma forms a pleasant shape which is suitable for placing on the sides of globes, particularly in the vast boring empty stretches around the Pacific ocean. It also makes for a neat year-long composite camera image for people with patience and good timing.
Mystery #4: UVA is NOT harmless, and it's everywhere
UVC is the nightmare radiation that seeps through the ozone hole. Most people don't get this without cooking themselves nude on a beach at solar noon on the summer solstice. UVB is the more familiar type that causes sunburn when you stay out too long without sunscreen on a sunny day.
UVA, however, is the stuff that goes right through your sunscreen, your clothes, and into the deeper layers of your skin. It goes through clouds, it goes through glass, it goes through just about everything that isn't opaque. Furthermore, because it penetrates the skin it is the radiation that causes the wonderful long-lasting deep glowing tan hawked as "safe" by tanning salons. The problem is because it operates at the structural level of the skin, it tends to cause the sort of loosening and wrinkling damage associated with aged skin. Second, if you're going to get cancer from ultraviolet exposure, then you want to have it on the surface where UVB operates, because those tumors are slow-growing and easily removed. If you get cancer deep in your skin, then it will often grow faster, making it harder to get at and remove before it spreads to other body parts and kills you.
Now for the freaky part. UVA is EVERYWHERE. You cannot escape it. If you can see light, even if it's an artificial light, then you're probably getting a measurable dose of UVA. If there is enough sun outside to necessitate wearing sunglasses, then you're probably getting dosed with UVA and B. If you're watching the sunset you're getting UVA. If you're working under fluorescent lights you're getting UVA. If you're staring at a monitor, then UVA could be getting into your eyes (such screens are normally polarized...I don't know how that affects it) My feeling is the new LED bulbs in the warm range probably emit the least UVA, but I don't know for sure. I'm also unclear on which bits of the spectrum are more likely to be reflected off cement pavement, or that will bounce around the margins of curtains to get inside your home.
Thursday, February 13, 2014
Workforce
Waldon's semi truck and a BMW sedan were traveling south on I-75 approaching the Alafia River bridge around 2:30 a.m. Wednesday when the truck hit the back of the [BMW] sedan. The BMW traveled off the inside shoulder of the bridge and into the Alafia River. James Dylan Proctor, 42, of Parrish, died at the scene. The semi overturned, spilling a large portion of the 30,000 gallons of alcoholic beverages it was carrying onto the highway. [...] Florida law does not prevent a person's driving history from allowing them to get a commercial license. So far, no charges have been filed. (baynews9)
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