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FAQs

Why does the moon seem to follow you?

Full moon photo by EarthSky community member Fernando Alvarenga in San Salvador.

Full moon photo by EarthSky community member Fernando Alvarenga in San Salvador.

You, or your kids, might notice this. When you’re moving in a car, earthly objects get left behind, but the moon seems to follow. Why?

Video: What is a pulsar?

A pulsar is a rapidly spinning neutron star which is the small, incredibly dense remnant of much more massive star. How dense? A teaspoon of matter from a neutron star weighs as much as Mount Everest.

What is a sun pillar, or light pillar?

U.S. West Coast got an amazing sun pillar on the first evening of spring. Thanks, Lyle Evans

The U.S. West Coast got an amazing sun pillar on the first evening of spring. Thanks, Lyle Evans!

EarthSky Facebook friends occasionally post beautiful photos of sun pillars, or light pillars. For example, there was a beautiful one seen from the U.S. West Coast on March 20, 2016 … a beautiful prelude to the first full night of spring. Click inside to learn what makes them, and for more photos.

Why beware the Ides of March?

Image credit: veraukoion

Image credit: veraukoion

If you have heard of the Ides of March, you know you’re supposed to beware them. Why? In ancient Rome, the ides of March were equivalent to our March 15th. You probably know of the Ides of March thanks to William Shakespeare. In his play Julius Caesar, a soothsayer – or fortune teller – says to Caesar: Beware the Ides of March.

Are a star’s brightness and luminosity the same thing?

This Renaissance woodcut is called Empedocles Breaks through the Crystal Spheres.

This Renaissance woodcut is called Empedocles Breaks through the Crystal Spheres.

When we talk about the luminosity of a star, we are referring to the star’s intrinsic brightness. We are not talking about the star’s apparent magnitude – its brightness as it appears from Earth. For instance, most every star that you see with the unaided eye is larger and more luminous than our sun.

Are solar eclipses more common than lunar eclipses?

Image by Joshua Valcarcel via Wikimedia Commons

Image by Joshua Valcarcel via Wikimedia Commons

It’s sometimes said that, on a worldwide scale, solar eclipses outnumber lunar eclipses by about a three to two margin. True?

Why no eclipse every full and new moon?

Photo credit: pizzodisevo

A solar eclipse happens at the new moon – when the moon passes between the sun and Earth. A lunar eclipse happens when the Earth, sun and moon align in space, with Earth in the middle. Why aren’t there eclipses at every full and new moon?

What causes Death Valley’s sailing stones to move?

The video above shows a famous sliding stone of Death Valley’s Racetrack Playa in motion. See it? It’s the big rock in the foreground.

Although their tracks across Racetrack Playa – a dry lake bed in Death Valley – have been observed and studied since the early 1900s, no one had ever seen the stones in motion … until recently. What’s more, the researchers who captured this video say they now know what causes the stones to move.

What is time?

Why the night sky can tell us a fair bit about time. Photo: eArches National Park/Flickr

Why the night sky can tell us a fair bit about time. Photo: eArches National Park/Flickr

… And why does it move forward?

See 5 bright planets at once

Since late January, and through mid-February, 5 bright planets are visible at once in the predawn sky. This image is from February 8, 2016.  It's by Eliot Herman in Tucson, Arizona.  View on Flickr.

Since late January, and through mid-February, 5 bright planets are visible at once in the predawn sky. This image is from February 8, 2016. It’s by Eliot Herman in Tucson, Arizona.

UPDATE February 8, 2016. The new moon comes to pass on February 8, 2016, at which juncture the moon transitions from the morning to evening sky. Many people around the world witnessed the moon sweeping by all five visible (naked-eye) planets from late January until February 7, 2016. But you still can see all these planets together in the morning sky for at least another week. Read more inside…