Wednesday, July 29, 2015

What's My UV Exposure?

Here is where the home form goes.

Your home data should appear here, but something has kept the script from updating it.

Your Current Latitude (please use decimal degrees, no minutes or seconds):
North or South:
Choose your nearest Home Elevation:

Please enter your current position data above.

Many places talk about the UV index as a way to indicate your exposure day to day, for example as part of the local weather report; however, it is difficult for most people to use this information effectively. That is why earth42 has developed an exposure calculator here, one that will compare your current location to that of your home, ie, the place you are accustomed to, as well as to a reference location on the Earth's equator at sea-level.
Here are a couple of assumptions:
  1. the earth's atmosphere is our major protection from harmful radiation, and this protection is essentially uniform throughout the planet. I know there are local variations in the temperature, ozone content, etc., but for our purposes we can idealize a bit and use a "rule of thumb", the Standard Atmosphere Model.
  2. The major difference from one place to another in the level of protection comes from its latitude. The farther from the equator, the greater the angle of sunlight, and thus the greater amount of atmosphere it passes through. This is what gives rise to the differences in climate as one travels from equator to pole. Additionally, as the Earth orbits the Sun, its tilted axis of rotation modifies the effective latitude of a given location. This is what gives rise to seasonal changes.
  3. Elevation above sea-level also affects ones exposure. The higher you are in the atmosphere, the less there is of it to protect you. This can undo much of the protection from higher latitudes, and measurements of air density by altitude have been made that we can use here.
 Combining these factors, we can calculate your exposure in a way that will give you a more intuitive sense of what to do about it.

Thursday, May 1, 2014

Is There Any Way to Really Fight Spam?

Hold a Sit-In!

Spam wastes an incredible amount of resources, and nobody likes it, except the spammers themselves. After all, they're making money. The endless cycle of putting up filters and such is the wrong approach; they just keep finding ways of getting past them. After all, you want to get your email, right?

What we need to do is attack the demand for spam. We can hold a "sit-in" at the sponsors' web sites! Just as with a traditional sit-in, we choose a place (ie the spam sponsor's web site), set a time when everybody should go there, and then at the appointed time, we all "go", ie repeatedly request the page.

Just as a million interested citizens inadvertently brought down the U.S. Affordable Care Act web site, we can bring a spammer client web site to a standstill, if enough of us want to, without doing the site itself any damage, nor breaking any law. Each participant in the sit-in is doing just what the spammer client wants us to do: go to the site.
The Sit-In app (currently available only at the SlideME android market) from earth42, facilitates each part of this process.

Sunday, November 25, 2012

What's my golf handicap?

A golf handicap enables you to gauge the quality of your game and compare it to others, regardless of what course you play. As part of the Rules of Golf, the USGA has created an algorithm for calculating your handicap based on your most recent 20 games.

With the Golf Handicap Calculator (currently available only for android devices) from earth42, you can enter rating and slope parameters of golf courses you play, and then enter your score and course for each game. Once you have at least 5 games stored, it will calculate and graph your "differentials", the normalized scores, and your "handicap index"; and once you have a handicap index, the calculator can also predict your score for a stored course, or from a rating and slope that you enter.

NEWSFLASH: I have recently had a very helpful conversation with theoclitus, a user who plays nine-hole golf courses. These courses have nine-hole ratings, and the newest version, 3.0, deals with both nine-hole and eighteen-hole courses - just register the course in your list with its nine-hole rating and slope, and check the box indicating it's a nine-hole course. If you play nine on an eighteen-hole course, and they don't furnish nine-hole ratings and slopes for the front and back, you can just use the course's given rating and slope, but you must double your score when you enter the game in order to get the correct handicap index, or at least as close as you can get. There is now also a preference in Settings to choose whether to display your handicap index as eighteen-hole or nine-hole, and regardless of that, you can select nine-hole or not when predicting your score.