Toscoremore

Why is the sky blue?

The light coming from the sun is made of many colors; light travels as a wave, and each color has a unique wavelength. Violet and blue light has shorter wavelengths, while red light has a longer wavelength, and the other colors have wavelengths in between.

When the different colors of light pass through the atmosphere, they run into molecules, water droplets and bits of dust. Because all these particles are closer in size to shorter wavelengths of light, they tend to scatter violet and blue light much more than red, and so they send rays of violet and blue ricocheting toward the ground — and your eyes. More violet light actually gets scattered by atmospheric particles than blue light, but your eyes are more sensitive to blue, so the sky appears blue.

Sunsets are orange-red because in the evening, with the sun low on the horizon, sunlight must pass through more atmosphere to get to your eyes, and only the red light can make it all the way through. The shorter wavelengths have all been scattered toward the ground in the part of Earth where it is still daytime.

Some migratory birds travel as much as 15000 km to escape the extreme climatic conditions at home. Generally they fly high where the wind flow is helpful and the cold conditions allow them to disperse the heat generated by their flight muscles. But how these birds travel to the same place year after year is still a mystery. It seems that these birds have a built–in sense of direction and know in which direction to travel. Some birds probably use landmarks to guide them. Many birds may be guided by the sun during the day and stars at night. There is some evidence that birds may use the magnetic field of the earth to find direction. And it is not only birds that migrate; mammals, many types of fish and insects are also known to migrate seasonally in search of more hospitable climates.

How long does oil take to form?

Under ideal conditions small amounts of oil have been known to form in less than ten thousand years. Typical oil deposits, however, likely required hundreds of thousands to a few million years to form.

Many of the coal and oil deposits in the Eastern United States formed during the Carboniferous period around 350 million years ago. Most of the oil in the middle east formed around 145 million years ago, between the end of the Jurassic and beginning of the Cretaceous.
Most of the oil and gas that formed since the Permian probably leaked out of overlaying permeable rock during intervening ages and was subsequently destroyed. We are fortunate large reserves remained trapped here and there where we could exploit them. Though we still have sufficient coal reserves to last us another few centuries, the age of oil is drawing to a close. We'll be able to continue extracting shale oil and other oil reserves for some decades yet to come, but it is unlikely we will be able to significantly ramp up production even if we wanted.