Why the Sky is Blue?

If you’ve got kids, and I do, you can impress their little minds by having savvy answers ready for  the questions they answer while they’re examining their navels.

Why is the sky blue? Why doesn’t the sky just stay black with the sun acting as another point of light? Why do the stars disappear during the day?

Got your long-term memory ready? Here’s the answer. The first thing to understand is that the sun is slightly brighter than the moon and stars. You can verify this by staring at the sun and burning your retinas out in a minute or so. (Staring at the moon is doesn’t do this and is actually romantic.) Also of note is that the atmosphere (nitrogen and oxygen molecules) has an effect on the happy little sun beams passing betwixt them.

There is a physical phenomenon called Rayleigh scattering that causes light to scatter when passing through molecules that have a diameter one-tenth that of the wavelength (color) of the light.

Sunlight is made up of all different colors of light, but because of the physical properties of all those oxygen and nitrogen molecules in the atmosphere, blue wavelengths of light are scattered much more efficiently than the other colors. So while most wavelengths hitting the upper atmosphere just pass through and on into space, blue lights path get changed, resulting in a defuse blue light coming from all directions of the atmosphere.

So when you look at the sky on a clear day, you can see the sun as a bright disk surrounded by blue as the atoms in the atmosphere scatter the blue light waves toward you. Got that?

Of course the sky on Mars is not blue. (See the color pictures from Mars Pathfinder) This is because the atmosphere of Mars is very thin and dusty, and atmospheric light scattering is dominated not by Martian atmosphere (mostly carbon dioxide) but by suspended dust particles. These are larger than the wavelengths of visible light, and they are reddened by iron oxide from the Martian soil. It’s not just Rayleigh scattering, so the spectrum is different.

Now when you kids ask you why the sky is blue, you can dazzle them with the explanation above, or you can say that it’s blue because that’s your favorite color. It works just as well and will probably impress your kids even more.

More on the blue sky and scattering 

Micro-organisims & You

While you might be close to your friends and family, but you have friends who are closer still. 600 different species of bacteria inhabit your mouth every morning. They’re the little guys that make up that tasty film on your teeth. Yum.

And it doesn’t stop there. About 500 species of bacteria, as well as many species of yeast and other organisms, inhabit your human gastrointestinal tract and make up your “gut flora”.

Yep. You’re a veritable Petri dish of little goo-critters. If you’re an ‘average’ human, the bacteria weigh in at about 1kg and the number of individual micro-organisms easily outnumbers the total number of cells in your bug-loving human body. (So far, none of these organisms have been identified as the midicloreans that Yoda uses to channel The Force but perhaps if you don’t brush your teeth you’ll have a nagging desire to build a light saber.)

Luckily for us a large number of these organisms don’t cause disease — instead, they help protect us from disease. The gut flora perform many functions that contribute to the health of the human host; “friendly bacteria” mostly have names beginning with Lactobacillus or Bifidobacteria.

The friendly bacteria aren’t the only type of microorganism present in your gastrointestinal tract however. There are also a number of organisms that don’t provide you with any benefits; these include coliform bacteria, yeasts and bacteroides.

Motion Sickness

Motion Sickness: My idea of the seventh level of hell is being stuck in winter ski-gear, in between two fat guys on a bus, in sunny weather, driving in circles searching for a parking space, backwards.

If you’re not currently puking your guts out and feeling woozy, it’s because your eyes, inner ears, skin, and muscles are sending signals to your brain about your bodies current position in space and tracking the direction of movement of all of your various parts. And all the signals are saying the same thing. That’s good.

If that’s not what’s happening and your ears, eyes and such are sending conflicting information and arguing about what’s going on with your body, that’s bad, and stand back because I don’t want you splashing anything nosesome on my shoes.

Motion sickness is that most noxious of feelings that happens to you when your balancing system gets overwhelmed by contradictory messages sent from the eyes and inner ears. Stuff like sweating, light-headedness, hyperventilation, nausea, vomiting and a remarkable ability to let loose incredible profanity without moving your head. If your eyes are telling you one thing, and the fluid of your inner ears are sloshing around telling you another, your brain seems to make a command decision and put everyone in time out.

For some people, motion sickness can be brought on merely by walking down the aisles in a supermarket or watching telephone poles whipping by a car window. Some people can even get motion sickness sitting in a theater and watching an action-packed film on one of those super-sized movie screens. Lets just hope that they’re not sitting right behind you.

Motion sickness in space is very common. Evidently your brain just won’t believe your ears that gravity’s been suspended for a while, and the Space Shuttle comes equipped with numerous barf ports. This is a good thing since who want’s to see that floating around in zero g.

What can you do to prevent motion sickness?

There are a number of options, home remedies, and hope. (There’s always hope.) By far the best option is to have your doctor prescribe a drug like Scopace (Scopolamine) which is an anticholinergic central-nervous system depressant. That’s good since it’s your anticholinergic central nervous system that’s trying to kill you. You want it depressed.

Locusts

Locusts are part of a large group of insects commonly called grasshoppers which have big hind legs for jumping. (Kangaroos also have big hind legs for jumping but are not part of this group.)

Locusts belong to the family called Acrididae but differ from grasshoppers in that they have the ability to change their behaviour and habits. So, while locusts could stop smoking if they want, grasshoppers are paying big tobacco ‘till they go legs up.

A Desert Locust lives a total of about three to five months although this is extremely variable and depends mostly on weather and ecological conditions. Their little life cycle has three stages: egg, hopper and adult. Eggs hatch in about two weeks, hoppers develop in five to six stages over a period of about 30-40 days, and adults usually mature in about two to four months (Sometimes as long as nine months for late bloomers or locusts that are still living with their parents).

Locust swarms can vary from less than one square kilometre to several hundred square kilometres. There can be as many as 80 million locust adults in each square kilometre of swarm which means they can’t remember everyone’s name and are constantly saying ‘excuse me’ as they bump into each other.

One Desert Locust adult can consume roughly its own weight (about two grams) in food per day. You on the other hand take a year to eat your own body weight if you’re average. I take about six months.

Each ton of locusts eats the same amount of food in one day as about 10 elephants or 25 camels or 2,500 people. A large swarm can in a cultivated area can eat enough food to feed 400,000 people for one year. You can see why people complain.

In order to get back at locusts, sometimes people eat them. If you ever find yourself in the middle of a swarm, take advantage.

Here are some recipes to help.

Boiled Locust: remove the wings and hind legs of the locusts, and boil in a little water until soft. Add salt, if desired, and a little fat and fry until brown. Serve with cooked corn.

Roasted Locust: prepare embers and roast the whole locust on the embers. Remove head, wings, and legs. Only the breast part is eaten.

Traveling Locust: If traveling do what the South Sotho people do. The heads and last joint of the hind legs are broken off and the rest laid on the coals to roast. The roasted locusts are ground on a grinding stone to a fine powder. This powder can be kept for long periods of time and is taken along on a journey. Dried legs are especially relished for their pleasant taste.

Cambodian Peanut Stuffed Locust: take several dozen locust adults, preferably females, slit the abdomen lengthwise and stuff a peanut inside. Then lightly grill the locusts in a wok or hot frying pan, adding a little oil and salt to taste. Be careful not to overcook or burn them.

Grilled Locust: prepare the embers or charcoal. Place about one dozen locusts on a skewer, stabbing each through the centre of the abdomen. If you only want to eat the abdomen, then you may want to take off the legs or wings either before or after cooking. Several skewers of locusts may be required for each person. Place the skewers above the hot embers and grill while turning continuously to avoid burning the locusts until they become golden brown.

Why time slows down when approaching the Speed of Light.

Ok, so you’ve heard that nothing can travel faster than the speed of light. (That’s not quite true. The expansion of the universe allows for faster than light travel but that’s another post.) You’re also aware that time slows down the closer you get to the speed of light. You know, the ‘One twin goes off to Alpha Centauri at the speed of light and comes back after 80,000 years but he’s only aged 3 months’ story.

Ever wonder why? Here’s the crib notes.

Everything in the universe always travels exactly at Light Speed. Always.

Time dilation: Special relativity declares a law for all motion: The combined speed of any object’s motion through space and it’s motion though time is always precisely equal to the speed of light.

That’s right, everything. You, me, the computer screen you’re looking at, your grandma’s French toast, Santa Clause… everything.

Everything is traveling through Spacetime: space (the three dimensions we experience and the nine others that m-theory predicts) and time.

Adding the total movement through both space and time always equals light speed. Always. Always. Always.

Space and Time do not exist seperately, the are parts of the same thing, Spacetime.

Since you must travel constantly at exactly the speed of light, when you increase your speed through space, you decrease your speed through time.

Your head (and the rest of you) is traveling through spacetime at the speed of light. But, when you’re at rest (not accelerating) all of your head’s movement is through time, none of it is traveling (accelerating) through space. Every time your head moves (accelerates) through space; in a car, in a plane, in a spaceship… even nodding up and down, some of it’s movement in time is lost since it is now moving through space.

Cool huh.

What about light?

Since light waves use all of their motion to travel through space at Light Speed, they have absolutely no motion through Time. Every photon that has ever been produced exists in an ageless state. (To us, the light seems to move through time but to the photon, time is standing still. This is one of the seemingly odd realizations fo Ensteins Theory of Relativity.) That's why poton's from the early universe don't 'fade out' or do something else. They can't, since for them, time is at a standstill.

The universe ages, light does not.

Reading: The Fabric of the Cosmos: Brian Greene