science of things

 Q:Why is the sky blue?
 A: Light is a type of energy that travels in vibrating waves at a speed of ~ 300,000 km/sec. Transmitted light from the sun is made up of a spectrum of colors (mixture of different colors) that our eyes can see. We can see the different colors of the visible spectrum by splitting the light with a prism. Each color in the visible portion of the spectrum has different wavelengths and energies. Violet/blue colors have the shortest wavelength and highest energy in the mixture. Red, on the other hand, has the longest wavelength and lowest energy. As light from sun moves through the atmosphere, most of the longer wavelengths pass straight through. Little of the red, orange, and yellow lights are affect by the air. But most of the light with shorter wavelengths such as blue and violet is absorbed and scattered all around the sky. So the sky is full of scattered blue and violet light. However, when we look at the sky, we will see blue light only because our eyes are not sensitive to violet light.

Q: What is farting?
A: The FART (Frequency Actuated Rectal Tremor).  Farting also known as flatulence, is the act of passing intestinal gas from the anus. Intestinal gas comes from several sources: air swallow, gas that seeps into our intestines from our blood, gas produced by chemical reactions in our guts, and gas produced by bacteria living in our guts. Why do fart smell? The smell of farts comes from mixture of various gases . This mixture contains sulfur. The more sulfur-rich foods you eat, the more sulfides will be made by the bacteria in your guts, and the more your farts will stink. Notorious or rather famous fart food causes fart: leguminous (beans, lentils, chickpeas…) vegetables, broccoli, cabbage, egg, milk, raisins and raw apples. Foods like cauliflower, eggs and meat are really bad for making stinky farts. Beans make you fart a lot, yet they are not the smelly kind. Why these foods are so farty? Take beans; they contain sugar called cellulose that we cannot digest. When these sugars make it to our intestines, the bacteria start feasting and making a lot of gas. The produced gas is propelled out by intestinal peristalsis movement.  Imagine eating a broccoli and cabbage salad for lunch, and an apple and raisins for recess with a big glass of milk...... you'll make a huge fart bomb!

Q: How do humidity and wind chill make us feel warmer or colder?
A: Our perception of temperature is due to the transfer of heat between our bodies and the environment. It has to do with the body's need to maintain a constant temperature by regulating dissipation of the metabolic heat it generates. Heat and temperature are closely related but distinct concepts. Temperature is a measure of our perception of hotness or coldness. The faster we lose heat to a substance, the colder it feels to us. Heat is energy in the form of molecular motion which moves spontaneously only from high temperature to low temperature. Dissipation of metabolic heat to the air is by convection, conduction, radiation, and latent heat. Of these, only radiation depends entirely on the temperature of the air. The others are affected by moving air and humidity. Because dry air is a poor conductor we exchange only small amounts of heat with it by conduction. Humid air is a slightly better conductor so when it is cold and humid we lose heat more rapidly than we would otherwise and it feels colder than it really is. Moving air feels colder because it removes the heated air from around the skin's surface. The effect of this convective heat loss is measured by the wind chill factor: the temperature at which still, dry air would conduct heat from unclothed skin at the same rate as the wind does at the ambient temperature. A heat transfer problem arises when exertion increases the metabolic rate. To keep its temperature from rising too high the body must exhaust this excess heat. Another problem arises when the air is warmer than the skin. Heat flows only from hot to cold so the body cannot lose heat to the warmer air by conduction, convection or radiation. The solution to both problems is the evaporation of perspiration from the skin which absorbs heat. This latent heat loss is faster in warm air, but slower in humid air.

 Warm, humid air feels warmer than it really is because we are not losing heat to it rapidly enough. Cold, damp air feels colder than it really is because we are losing heat to it too rapidly. Moving air feels cool because it both carries away heat and increases evaporation.

 Q: I Can See My Breath When It's Cold?

A:Water has three phases: liquid, gas, and solid. Water vapor is the gas phase, and ice is the solid phase. What you are seeing when you are breathing are little droplets of water condensing out of a gas that's in your lungs. Our breath contains a lot of vapor because our lungs are quite moist. When we go outside on a cold day, watervapor in our breath lose the energy that keeps them moving. Instead of bouncing around, they crowd up next to each other when loosing energy (the particle theory). And as they slow down, the molecules change from a gas state to denser liquid and solid states. So what we see when breating is the water vapor that lost energy and became visible.