The moon is waning now, and the evening sky is free of bright moonlight. By this weekend, the only moon you see will be a waning crescent in the hours before dawn. Good weekend to go camping and observe some dark skies! You might wonder … how many stars can you see with the eye alone?
May’s birthstone is the emerald, a type of beryl colored green by chromium. Perfect emeralds are among the rarest of gemstones. Kings and queens wore emeralds in Babylon and Egypt, and Cleopatra owned them as part of her royal fortune. Later, in the Middle Ages, people believed that the emerald held the power to foretell the future. Find out more about emeralds, and the birthstones for all the months of the year.
Happy May Day! May Day is an ancient spring festival in the Northern Hemisphere. It’s an astronomical holiday, one of the year’s four cross-quarter days, or day that falls more or less midway between an equinox and solstice – in this case the March equinox and June solstice. May Day also stems from the Celtic festival of Beltane, which was related to the waxing power of the sun as we move closer to summer. At Beltane, people lit fires through which livestock were driven and around which people danced, moving in the same direction that the sun crosses the sky.
The New York Times reported yesterday (April 29, 2013) that Japan’s Fukushima Daiichi nuclear power plant is currently struggling to contain a flood of highly radioactive wastewater. This is the plant that was damaged two years ago during the March 11, 2011 9.0-magnitude earthquake and subsequent tsunami in Japan. This post explains the kind of radioactivity most commonly associated with nuclear power plants, and its harmful effect on the human body.
You can define twilight simply as the time of day between daylight and darkness, whether that’s after sunset, or before sunrise. Astronomers, surely the experts on nighttime, recognize three kinds of twilight, which are explained in this post.
Sky watchers on occasion report seeing colors in the clouds, and sometimes our friends send photos of these rainbow colors in clouds. You’ll find some examples in this post. These colorful clouds are called iridescent clouds, and the phenomenon is called cloud iridescence or irisation. The term comes from Iris, the Greek personification of the rainbow. Click inside for some amazing photos and info about iridescent clouds.
Have you ever noticed mushrooms growing in a big circle? It’s known as a ‘fairy ring.’
Ok, you probably didn’t see it looking exactly like this. Click in for some photos of the way a fairy ring is more likely to look, plus an explanation of why these mushroom circles happen.
The first Earth Day – April 22, 1970 – marked the beginning of the modern environmental movement. Approximately 20 million Americans, especially on college campuses, participated. Since then, Earth Day is always celebrated on April 22. But why April 22?
Leonardo Pisano Bigollo, aka Leonardo of Pisa or sometimes just Fibonacci, is best known in the modern world for spreading the Hindu–Arabic numeral system in Europe. He also introduced the west to what is now called Fibonacci’s number or sequence, which relates to shapes found in biological systems: spiral galaxies, sunflowers, shells.
What are star trails? They are the continuous paths created by stars, produced during long time exposure photographs, as shown on this page. In other words, the camera doesn’t track along with the stars’ apparent motion as night passes (actually caused by Earth’s spin under the sky). Instead, the camera stays fixed, while, as the hours pass, the stars move. The resulting photos show the nightly movement of stars on the sky’s dome.