Meet opal. It’s one of two birthstones for October. The other October birthstone is tourmaline, which exhibits the broadest spectrum of colors of any gemstone and thus is often misidentified as rubies, emeralds and sapphires. Check out the beautiful images of these stones, inside this post. And happy birthday!
No matter where you are on Earth, you have a due east and due west point on your horizon. That point marks the intersection of your horizon with the celestial equator – the imaginary line above the true equator of the Earth. At the equinoxes, the sun appears overhead at noon as seen from Earth’s equator. That’s the definition of an equinox: it’s when the sun crosses the celestial equator, as seen in Earth’s sky. That’s why the sun rises due east and sets due west for all of us on the day of an equinox.
Many planets in our solar system have more than one moon. Mars has two moons, Jupiter has 66, Saturn 62, Uranus 27, Neptune 13. But our planet Earth has just one moon. Doesn’t it? Moons are defined as Earth’s natural satellites. They orbit around the Earth. And, in fact, although Earth sometimes has more than one moon, some objects you might have heard called Earth’s second moon aren’t, really. Let’s talk about some non-moons first.
Happy birthday to all you September babies!
Your birthstone, the sapphire, was said to represent the purity of the soul. During the Middle Ages, it was worn by priests as protection from impure thoughts and temptations of the flesh. The sapphire is a relative of July’s birthstone, the ruby. Like ruby, it is a form of the mineral corundum, a normally drab grey mineral. Red corundum is called the ruby, while all other gem quality forms of corundum are called sapphires.
Light is the fastest-moving stuff in the universe. It travels at an incredible 300,000 kilometers (186,000 miles) per second. That’s very fast. A light-year is the distance light travels in one year. How far is that?
Every year for many years now, scientists and others have kept an eye on the annual Arctic sea ice minimum, which occurs when the floating Arctic ice cap melts to its smallest size of the summer. That minimum usually comes around mid-September, and, although the ice is still melting this year as of this writing (August 23, 2013), it now appears unlikely that 2013 will break a new record for the least ice observed in the Arctic. At the same time, in 2013, Arctic sea ice at minimum continues its downward trend.
If you were mountain climbing, at a time of day when the sun was low and behind you, and if you climbed high enough to look down into a mist from a ridge of peak, you might witness the shadowy figure of the Brocken Spectre. It’s your own shadow that you see, cast on the surface of the mists below, surrounded by a ring of light. The sun must be behind you. You’re seeing your shadow projected forward through the mist.
It’s a question people ask us… Will our home galaxy someday collide with the next-nearest spiral galaxy, in the direction of the constellation Andromeda? And if so, when?
Happy birthday to our August friends!
August has two birthstones, peridot and sardonyx.
Some of the finest peridot stones are called “evening emeralds” because they appear greener under artificial light.
Saronyx is used to carve cameos and intaglios.
Read more about both your birthstones….
This photo of a green flash was taken by EarthSky Facebook friend Mike Quinn on July 29 in the East China Sea. Thank you Mike!
It’s said that once you’ve seen a green flash, you’ll never go wrong in matters of the heart. A green flash happens when the sun is almost entirely below the horizon, with the barest edge of the sun – the upper edge – still visible. For a second or two, that upper rim of the sun will appear green in color. It’s really quite exciting to see, especially if you’ve been looking for one.
Read more, plus see more great pics.