Alas, it has been a while since I’ve written a new LSNED article. There are only 24 hours in a day, you know!

Twenty-four seems like an arbitrary number to choose for hours in a day. Consider that somebody along the way had to decide how long an hour was, and how many could squeeze into one day. So just where did the number come from?

It appears the Egyptians are the architects of our daily scheduling. In ancient times, their numbering system was based on 12, just as ours is based on 10. It is believed they learned to count using the joints of their fingers (three on each finger) making 12 the natural sized group. Frankly, that’s no more strange than how we now base everything on 10 because we have ten fingers/thumbs.

Any way you count it, the Egyptians loved their twelves, so they opted to decree there were twelve parts to the day, and twelve parts to the night. For a long time, these twelve parts would stretch and grow throughout the year as sunlight varies with the seasons. It was the Greek mathematician, Hipparchus, who first set about trying to standardize the time periods, but this was not widely practiced until the 4th century.

The word hour began as hore or hora, but the H has fallen silent since early Roman times.

If you’re hoping for more LSNED’s, I suggest you poke back into the archives with this article on clocks that let you smell the time. And next time you complain about not having enough hours in the day, at least know you know who to point your triple-jointed finger at. Yes indeed, we all… clock like an Egyptian.

• Source: Curious About Astronomy – Cornell University
• Source: Origin of the word Hour – Online Etymology Dictionary

Fun Fact: If the movie Rocky had been about wheelchair boxing (yes, it does exist!) then, according to the guidelines of the Americans with Disabilities Act, the famous training montage would have climaxed with a dramatic roll up a 672 foot long wheelchair ramp to the Philadelphia Museum of Art.

Okay everybody, get yourself a board. A long board. Great. Now… lean it against something sturdy. Done? Congratulations! You’ve just constructed a “machine”… technically speaking. It’s one of the six Simple Machines that are the basic building blocks of all our tools and devices.

You may call it a ramp, or “a plank leaning on a fence”, but it is in fact an inclined plane in science talk. A plane is a flat surface (not to be confused with a plain… a flat surface covered in grass) and inclined means one end is higher than the other. Sounds simple, but like all the other simple machines, this has given you a mechanical advantage. It has made it easier to do work.

We’re talking about work in the technical/mechanical/physics way. Work is defined as the energy transferred by a force acting over distance. So let’s say there’s a big box on the floor. For you to lift that box a fraction of an inch you would have to apply a certain amount of force. Now, for you to lift that box from the floor to the table, you would have to maintain that same amount of force all the way up. That gives us the formula: Work = Force x Distance.

Now let’s get our scrap of lumber to make an inclined plane. One end is on the floor, the other end rests on the table edge. It’s easier to push the heavy box up the ramp (compared to lifting it straight up) because the inclined plane covers more distance to reach the objective. By virtue of the formula (W = F x d) to do the same amount of work, an increased distance requires less force.

The longer an inclined plane, the less force required to get to the top. That’s why some streets in San Fransisco are so curvy. They cover more distance going up a steep hill, so the car engine doesn’t have to work as hard. However, the same amount of work is done either way. It’s just a choice between light work for a long time, or heavy work for a short time.

For wheelchair access ramps, the guideline is to have a slope of 1:16. (16 inches of ramp for every 1 inch of height) That means a recommended 9 feet of ramp for every average 7-inch step of a stairway. 4 steps, 37 foot ramp. 72 famous Philadelphian steps, 672 foot ramp.

And since I know you’re curious, if the ADA wanted to make Mount Everest more wheelchair friendly, starting at base camp they would need to build a ramp over 55 kilometers in length to reach the summit.

• Source: Inclined Plane on Wikipedia
• Source: ADA Wheelchair Ramp Specs from Mobility Advisor

These days any weather report worth its salt will include the UV index number. I think we all understand the practicality of it. The higher the number, the higher risk of sunburn. But personally, that superficial understanding doesn’t satisfy my curiosity.

I also get to brag a little, as the UV Index in a Canadian invention, circa 1992. Many other countries picked up on the idea. It’s now been taken over and standardized by the World Health Organization.

We’re talking about ultraviolet radiation here, which got a mention last week regarding its spot on the spectrum of electromagnetic waves. There are three types of UV radiation, conveniently called UVA, UVB, and UVC depending on the wavelength. Each one affects us differently.

UVA: These are the longest waves, and thus can more easily pass through stuff. As such, nearly 99% of all UV radiation that gets through the ozone layer is UVA. UVA causes immediate tanning, and long term wrinkling and skin aging.

UVB: While making up only 2% of ultraviolet radiation reaching earth, this is the bad guy. The cause of skin cancer! Last year I wrote about how a sunburn modifies your genes!

UVC: Our ozone layer pretty much completely blocks UVC radiation from reaching us. Let’s hear it for the ozone, ladies and gentlemen!

Now, the UV index is a rating of how much UV radiation is hitting the earth on a given day.It’s calculated based on a number of factors specific to your area.

1. Sun height – Midday in mid-summer would have the sun looking straight down on you, meaning the least amount of atmosphere between you.
2. Latitude - Your position on the globe affects the angle of the sun.
3. Cloud cover – Well that seems obvious!
4. Altitude – The higher you are, the less atmosphere to protect you. Being 1000 meters above sea level equals a UV increase of about 10%.
5. Ozone – The ozone fluctuates, so it can be absorbing more or less UV on any given day.
6. Ground reflection – Depending on the colour and surface, you could be getting UV bounce-back. Snow will reflect 80% of UV waves.

At night, in the dark, the UV index would be zero. While there’s no upper limit to the scale, 10 would be “extreme”… blue sky, mid summer, sun directly overhead.

I’ll wrap up with a note about sunscreen. Specifically that big SPF number on the bottle. You may know it means Sun Protection Factor. That number is determined with a simple lab test.

They round up some pasty looking people and test how long it takes for their bare skin to burn under a controlled dose of UV light. Then they apply the sunscreen to another patch of skin, and measure the time to burn again. If the original burn happened in 3 minutes, and the sunscreened burn took an hour, that means the natural skin protection increased by a factor of 20. (3 minutes x 20 = 60 minutes) Thus, it gets labeled as Sun Protection Factor 20.

• Source: Ultraviolet Radiation – World Health Organization
• Source: Ultraviolet Index – Wikipedia

P.S. The illustration above was inspired by the random words found in robot-proof captcha security things. (where they ask you to decipher a blurry word… in my case “climate iseight”) Captcha Art is kind of an in thing to do these days. The drawing then reminded me I’ve been wanting to do a story on the UV index for a while.

As I was driving down a remote highway this afternoon I saw a curiosity-inspiring sign. “Speed Limit Enforced By Aircraft”. It immediately induced several silly scenarios to play out in my head. I suppose if you got it up to 260 km/h (160 miles per hour) you could potentially be chased by a Cessna aircraft… but if you then slowed down again you would be resisting arrest?

The fact of the matter, which happens to be what I do best, is that planes are used on long open stretches of highway to observe and report “aggresive drivers”. Where you see these signs, you’ll also notice large white marks along the side of the road. It’s a similar feeling as an ant walking along a yardstick. These marks are used for aerial measurement.

The pilot can watch how fast you go between these white marks to figure out your speed visually. Then they call it in to see if a regular patrol car wants to pick up the chase the old fashioned way and track you down. In the case of commercial vehicles that can be recognized from the air, you could potentially get a speeding ticket in the mail directly from the pilot.

Should you ever find yourself with an aerial-observed infraction (and assuming you had slowed down before the patrol car found you) rumour has it that you’d do well to challenge it in court. Both the patroller and the pilot must be present to testify, or else it is dropped.

• Source: A user discssion forum, though totally unofficial, it was the most thorough source I could find on the topic

Please put your desk chairs in the full upright and locked position. We’re not expecting any turbulence, but as we sit we are moving at an astronomical speed… literally. You and I are little blobs of stuff (and no, I’m not calling you fat) stuck like bubble gum to the side of earth. It feels like we’re sitting still, but that is so ridiculously far from the truth.

1 600 km/h – Once per day our planet completes a full rotation, creating the illusion of the sun setting and rising. If you were standing still at the equator, you would actually be moving at 1600 kilometers per hour! We don’t feel this movement because it’s so smooth and consistent.

107 000 km/h – Every year the earth completes a full trip in orbit around the sun. In order to stay on schedule it requires a speed of 107 thousand kilometers per hour. This also means you’re personally moving faster at night, when you are on the outside of the orbit and the earth rotation is in (more or less) the same direction as the solar orbit. Conversely, you’d be going a bit slower during the day… like running towards the back of a moving train.

70 000 km/h – This gets a bit mind-boggling now, but our sun is not sitting still either. The numbers get harder to calculate because there is no sign-post to measure our speed against. Relative to other stars in the “neighbourhood” of the milky way galaxy, our sun and solar system is slowly milling about at 70 thousand clicks.

792 000 km/h – Like the earth going around the sun every year, the sun has a “galactic year” that is 225 million earth-years long. We are located near the outside edge of the milky way galaxy that spins like a pinwheel. Every 225 million years our little patch of space makes one trip around. The speed of that trip clocks at 792 thousand km/h.

If all those motions were ever to line up and be working in the same direction we’d be trucking along at near 1 million km/h when sitting still! But hold on to your hats, folks… there’s one more thing to consider…

2 100 000 km/h – Our pretty little galaxy is moving too. Perhaps you’ve heard that the universe is expanding, well, apparently we’re caught up in a current moving at over 2 million km/h. This is calculated by comparing our movement to the “cosmic background radiation”, which is the most steady, constant thing found in the universe.

This, I believe, is the number one reason not to run at a swimming pool because really it’s not adding much to your speed in the big picture.

• Source: http://www.astrosociety.org/education/publications/tnl/71/howfast.html

In popular internet culture, declaring a “FAIL” is the best thing since bacon. But today we’re looking at the almost-fail. In North American schools you’re most often given a letter grade: A, B, C, D, or F. But hey now… what happened to E?

Some grading systems do include an E grade, like the European Credit Transfer and Accumulation System, or ECTS. (that’s right, they may have an E in their grades, but they’re missing an A in their name) They use the E grade to mean “sufficient”, or meeting the minimum requirement. Australian schools give an E for “unsatisfactory” scores in the 40 to 60 percent range. It seems that wherever it’s used a grade E is given to mean “very close to failing” or sometimes “you are failing now, but you can make up for it”.

So the question is, why has the E vanished from schools in most of the US, Canada and many other parts of the world? I’ve found no hard facts, but a few theories…

In the early years of school you are often graded by what the teacher thinks of your performance. In that case E for “excellent” was the top mark, followed by G for “good”, S for “satisfactory”, and the dreaded N for “needs improvement”. So perhaps E has fallen out of favour to avoid confusion.

And you certainly can’t trust those wily kids nowadays. If a paper had an F grade written on it, it would be quite simple to upgrade to an E with a stroke of the red pen. Mind you… I don’t think “almost failing” is really impressive enough to warrant the effort.

My gut tells me that 6 grade levels was too many for practical use. A, B, C, D and “Not Good Enough” is all that was needed, so one letter had to go. I’ve found evidence of some US high schools grading from A-E, but it has proven more popular to use F rather than E simply because of the convenient fact: F stands for FAIL!

• Source: Grading systems from around the world – http://en.wikipedia.org/wiki/Grade_(education)
• This article inspired by a question emailed to me from Nicholas at Louisiana State University… you can email me questions too, ya know.

The time is 250 BC, about 1500 years before what we call “modern science” took it’s first baby steps. The Egyptian city of Alexandria, on the northern coast of Egypt, was home to the greatest library that ever existed, filled with the wisest people of the day, and the birthplace of many fundamentals of mathematics, geometry, and other sciences.

The head librarian was Eratosthenes who was a talented generalist of knowledge, dabbling in many fields. Colleagues joked he was “the second best in the world at everything”, but in today’s story he got the jump on everyone. As he was reading one of the hundreds of thousands of books (scrolls) in his library collection, he found a rather mundane observation from the city of Syene, further south in Egypt.

It was reported on the longest day of the year (summer solstice, June 21), as it came to midday columns in Syene would cast no shadow. The sun was so directly overhead that the light would shine straight down to the bottom of a well. Eratosthenes did his own experiments in Alexandria and found that on the same day, at the same time, there were shadows. The sun shone straight down on Syene, but Alexandria was at an angle. Curious!

Time to apply those math and geometry skills that were floating around the library. By measuring the shadow cast from his sticks, and determining the distance from Syene to Alexandria (he hired somebody to pace out, on foot, the 5000 stadia, or 800 kilometers!) he had the numbers required for his calculation.

His shadow suggested that Alexandria was “tilted” a little over 7 degrees from Syene. Knowing there are 360 degrees in a circle, that meant the distance between the cities was about 1/50th of the total. Multiply the walking distance (800 km) by 50 and you end up with 40,000 kilometers around the whole earth.

Eratosthenes was using rough measurements, and even rounding his numbers for easier calculation. However the idea was solid, and his estimate revealed great accuracy when the true circumference of the earth was measured to be 40,075 kilometers around. Not bad for some sticks and piece of paper.

Sadly the great library of Alexandria was destroyed, along with most of the knowledge housed within. For over 1500 years after Eratosthenes the earth was still generally believed to be flat until the great ships actually set out to make the impossible voyage.

• Source: Carl Sagan’s awesome “Cosmos” documentary. (DVD at Amazon.com)