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What is radiocarbon dating?

At a very steady rate, unstable carbon-14 gradually decays to carbon-12. The ratio of these carbon isotopes reveals the ages of some of Earth’s oldest inhabitants.

Star brightness versus star luminosity

Some extremely large and hot stars blaze away with the luminosity of a million suns! But other stars look bright only because they’re near Earth.

What’s a penumbral eclipse of the moon?

During a penumbral eclipse, observant people in the right spot on Earth will look up and notice a dark shading on the moon’s face. Others look and notice nothing at all.

What’s a Blood Moon?

Nowadays, 4 totally eclipsed moons in a row are called Blood Moons. Why? We don’t know for sure, but the answer may lie in a 2013 book by 2 Christian pastors.

Why no eclipse every full and new moon?

This year, in 2017, there are 12 full moons and 12 new moons, but only four eclipses – two lunar and two solar.

Circumpolar stars never rise or set

From Earth’s North and South Poles, all the stars appear as circumpolar. Meanwhile, at the equator, no star is circumpolar. And what about in between?

How big are the biggest monster stars?

How big can stars get? And how do these monster stars get so big?

What are the seasons like on Uranus?

Uranus lies nearly sideways with respect to the plane of its orbit around the sun. That sideways tilt makes a huge difference between winter-summer on Uranus, and autumn-spring.

Why stars seem brighter this time of year

No matter where you are on Earth on December, January and February evenings, you’re looking toward bright stars in our local spiral arm.

What is a supermoon?

By at least 1 definition, the year 2017 has 4 supermoons. Three are new moons and not visible in our sky. The only full moon supermoon of 2017 will come in December.

January’s birthstone is the garnet

Happy birthday January babies!  Your birthstone is the garnet.

Lucky New Year’s foods

Lucky New Year’s foods in the U.S. South and around the world. Happy 2017!

Why were prehistoric insects so huge?

Before the dinosaurs, giant insects ruled the world more than 300 million years ago.

Watch for earliest sunsets before solstice

Year’s shortest day comes at winter solstice. But, for Northern Hemisphere, earliest sunsets happen around early December. Southern Hemisphere? Your earliest sunrises are around now.

How long to orbit Milky Way’s center?

One journey of our sun and planets around the center of our Milky Way galaxy is sometimes called a cosmic year. That’s approximately 225-250 million Earth-years.

Why a halo around the sun or moon?

A large ring or circle of light around the sun or moon is called a 22-degree halo by scientists.

What is the Brocken Spectre?

The Brocken Spectre is your own shadow, cast on mists below you, when you are mountain climbing. The shadow may appear enormous and has a ring around it.

When can you see Earth’s shadow?

You can see it any clear evening …

Does Mars have a North Star?

Earth’s north star – Polaris – is located nearly directly above Earth’s north pole. There’s a star above Mars’ north pole, too, but it’s very faint.

What causes rainbow colors in clouds?

Iridescent clouds – clouds with rainbow colors – happen when especially tiny water droplets or small ice crystals individually scatter light.