Something for the Weekend

First things first, Earth. NASA has just released the most detailed whole planet pictures to date showing our small, mostly blue, ball in stunning detail. Can you pick out your location?

http://gizmodo.com/5478787/the
-most-accurate-highest-resolut
ion-earth-view-to-date?utm_sou
rce=feedburner&utm_medium=
feed&utm_campaign=Feed:+gi
zmodo/full+(Gizmodo)

(Just click to enlarge)

To go hand in hand with the new pictures is this animation showing plate tectonics and how our planet has evolved over the last 600 million years and our predicted future (this is from the Northern University of Arizona’s Geology dept)

http://www.youtube.com/watch?v
=uGcDed4xVD4

Finally as a follow up to two weeks ago’s focus on STS130 here is a nice photographic record of the mission from the guys themselves.

http://www.sacbee.com/static/w
eblogs/photos/2010/02/space-sh
uttle-endeavours-missi.html

Internet security and Prime numbers

Ever wonder how websites like Amazon.com keep your personal information, like credit card or check numbers, safe from the internet bad guys? Well, here’s the how.

At the Amazon website you enter in your private info, press “send”, and your internet browser quickly encodes your data and sends it off to Amazon. To make sure no one but Amazon can view your info, each code has a lock that can only be opened with the correct key, which Amazon has.

This is where prime numbers come into play. Prime numbers are those divisible only by themselves and 1, like the numbers two, three, five, seven, eleven etc. Of course these are very small prime numbers, but there are infinitely many of them and they can get big; the biggest found so far is thirteen million digits long!

The lock on the code protecting your private info is a very big number which is the unique product of two prime numbers, and the key to this lock are exactly these two primes. As a small example, take the number fifteen.

If this were our “lock” number, then the two primes three and five would be our “key”; since both are prime and three times five is fifteen. Unlike the small example however for a larger “lock” number it is nearly impossible to find the two “key” primes if you don’t already know them.

The best computers in the world might take years to find the “key” primes of a “lock” number only three-hundred digits long. Thankfully websites like Amazon typically use “lock” numbers at least this big, thus making it nearly impossible for a bad guy to sneak a peak at your private info online.

All points north

Antarctica is 98 percent ice and 2 percent barren rock. The average thickness of the ice sheet is 7,200 feet. This amounts to 90 percent of all the ice and 70 percent of all the fresh water in the world. If the ice cap were to melt, the sea level would rise by an average of 230 feet.

The bed of nails and how to do it the scientific way

Quite rightly the prospect of lying down on a bed of sharp pointy metal things isn’t something to be done lightly, because, lets face it, its going to hurt.

Or will it?

The bed of nails trick is, when taken apart by science, not as painful as you might first imagine.

Think of it this way. You can press your fingertip lightly on a nail without it hurting. If you put the other end of the nail on a scale and then press, you can see how many pounds of pressure you can put on one nail without it hurting you. Don’t press too hard!

Suppose the answer is one pound. You can press down on a nail until the scale reads one pound, and beyond that you don’t want to press any harder. Okay, one pound of pressure per nail is safe for you. So, if you weigh 200 pounds, you can lie on a bed with at least 200 nails on it and not be hurt. That’s because each nail is supporting only one pound and your weight is evenly distributed.

And there you go, how to lay on a bed of sharp objects without the need for any guru’s, incantations or other mumbo jumbo.

Lay carefully and evenly though if you don’t want to become a human pin cushion.

A spoonful of honey

It takes twelve bees a lifetime to make one teaspoon of honey.

Meteorological Mythology

Which area of science would you expect to find elves and sprites ?

Answer Meteorology - Sprites are large-scale electrical discharges high above a thunderstorm cloud. Elves, or ‘Emissions of Light and Very low frequency perturbations from Electromagnetic pulse Sources, are a glow caused by colliding electrons.

Recognizing Rhesus

Recent tests have shown that at six months a human baby can tell the difference between two Rhesus monkey faces just as well as two human ones. By twelve months this ability is gone, the baby can recognize the difference between the human ones, but the monkey faces all look the same. This is giving scientists an insight into how our brains are wired at birth with innate abilities, but our brain changes over time using a "use it or loose it" philosophy.

Measuring the Moon

The Moon is 27% the size of the Earth.

Radius of Moon = 1738 km

Radius of Earth = 6378 km

Comtemplating Casimir

Today's Factoid isn't so much a fact as an explanation.

The Casimir effect is a small attractive force that acts between two close parallel unchargedconducting plates. It is due to quantum vacuum fluctuations of the electromagnetic field.

The effect was predicted by the Dutch physicist Hendrick Casimir in 1948. According to the quantum theory, the vacuum contains virtual particles which are in a continuous state of fluctuation. Casimir realised that between two plates, only those virtual photons whose wavelengths fit a whole number of times into the gap should be counted when calculating the vacuum energy. The energy density decreases as the plates are moved closer, which implies that there is a small force drawing them together.

The attractive Casimir force between two plates of area A separated by a distance L can be calculated to be,

π h c

F = ------- A

480 L ⁴

where h is Planck's constant and c is the speed of light.

The tiny force was measured in 1996 by Steven Lamoreaux. His results were in agreement with the theory to within the experimental uncertainty of 5%.

Particles other than the photon also contribute a small effect but only the photon force is measurable. All bosons such as photons produce an attractive Casimir force while fermions make a repulsive contribution. If electromagnetism was supersymmetric there would be fermionic photinos whose contribution would exactly cancel that of the photons and there would be no Casimir effect. The fact that the Casimir effect exists shows that if supersymmetry exists in nature it must be a broken symmetry

According to the theory the total zero point energy in the vacuum is infinite when summed over all the possible photon modes. The Casimir effect comes from a difference of energies in which the infinities cancel. The energy of the vacuum is a puzzle in theories of quantum gravity since it should act gravitationally and produce a large cosmological constant which would cause spacetime to curl up. The solution to the inconsistency is expected to be found in a theory of quantum gravity.

Some examples in practice

Since L is in the denominator, the bigger L gets, the smaller the force will be; and because the force goes as the fourth power of L , the drop-off with increasing distance will be really huge. So let's make L small--say, one micron--together with big one-square-metre plates:

π × 6.6 × 10 ^-34 × 3 × 10 ⁸ × 1

F = ------------------------------ newtons

480 × 10 ^-24

or 1.3 mN. Now, since the weight of 1 kg is about 10 N, then 1.3 mN is the weight of 0.13 grammes. Which is pretty small, but measurable, except that putting two 1 square metre plates a micron apart would be difficult in practice. But using smaller plates leads to smaller forces. For instance plates with area 1 square centimetre placed 1 millimetre apart would feel a force equivalent to the weight of 10 ^-17 grammes, which is vastly smaller!

Missiles in the Marshall's

The largest coral atoll in the world is Kwajalein Atoll in the Marshall Islands. Although like some if its neighbours this atoll hasn't been used for nuclear testing It is used by the US as a missile-testing facility with two airbases currently in operation on the windswept island.

http://virtualglobetrotting.co
m/map/kwajalein-atoll/view/?se
rvice=0