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FAQs

Will the Andromeda galaxy someday collide with our Milky Way?

Image Credit: NASA, ESA et al.

This image represents Earth’s night sky in 3.75 billion years. The Andromeda galaxy (left) will fill our field of view then, astronomers say, as it heads toward a collision with our Milky way galaxy. Image Credit: NASA, ESA et al.

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?

Does Earth have a second moon?

Image of Earth with two moons, generated in Celestia software, by Grebenkov in Wikimedia Commons.

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?

What exactly is twilight?

Photo credit: joiseyshowaa

Photo credit: joiseyshowaa

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.

Does your dog pronk?

Among wild animals, pronking may be a way of avoiding predators. But when you see an animal pronk, you can’t but think it’s leaping for joy. More videos inside.

Scared of thunder and lightning? You have astraphobia

Never let your pets watch scary movies. Never a good idea! Image Credit: John Veldboom via Flickr

Thunder and lightning can be scary to pets, too. Image via John Veldboom via Flickr

Bam! Yikes!

Do you – and your dog – have astraphobia?

Virga is rain that doesn’t reach the ground

Virga over west Texas by Deborah Byrd.

Virga over west Texas by Deborah Byrd.

We’ve all seen virga, but maybe not known what it’s called. Virga is rain that evaporates before it hits the ground. It often appears in streaks or shafts extending from the bottoms of clouds. You often see virga over a desert, where low humidity and high temperatures can cause rain to evaporate shortly after being released by clouds. Or you might see virga at high altitudes; in fact, the precipitation often starts out in the form of ice crystals. Virga is commonly seen in the U.S. West and above the Canadian Prairies, in the Middle East, Australia and North Africa. At some northerly latitudes, too – as in the photos from Sweden on this page – virga sometimes paints the sky above.

This date in science: New record for youngest moon

View larger. | Youngest possible lunar crescent, with the moon's age being exactly zero when this photo was taken — at the precise moment of the new moon - at 07:14 UTC on July 8, 2013.  Image by Thierry Legault.  Visit his website.  Used with permission.

View larger. | Youngest lunar crescent ever photographed, with the moon’s age being exactly zero when this photo was taken — at the precise moment of the new moon – at 07:14 UTC on July 8, 2013. Image by Thierry Legault. Used with permission.

July 8, 2013. On today’s date a year ago, a new record was set for the youngest moon ever photographed. Thierry Legault – shooting from in Elancourt, France (a suburb of Paris) – captured the July 2013 moon at the precise instant it was new, or most nearly between the Earth and sun for that lunar orbit. Legault’s image shows the thinnest of lunar crescents, in full daylight (naturally, since a new moon is always near the sun in the sky), at 0714 UTC on July 8, 2013.

Baltoro Glacier is a river of ice in Pakistan

This isn’t the Arctic. It isn’t Greenland. It’s Pakistan. At 63 kilometers (39 miles) in length, Baltoro Glacier in Pakistan is one of the longest glaciers outside the polar regions.

How do fireworks get their colors?

Photo credit: Jeff Golden

Photo credit: Jeff Golden

Happy Independence Day! If you’re celebrating the 4th of July by attending a fireworks display, maybe you’ll look up and wonder: What creates those red, orange, yellow, green, blue and purple colors exploding in the night sky?

What’s the birthstone for July?

Photo credit:  Shutterstock

Photo credit: Shutterstock

Happy birthday to all you July babies! Your birthstone, the ruby, is among the most highly prized of gemstones. Large rubies are harder to find than large diamonds, emeralds and sapphires. As a result, rubies’ value increases with size more than any other gemstone.