Alpha Centauri is the nearest star system to our sun at 4.3 light-years away. That’s about 25 trillion miles (40 trillion km) away from Earth – nearly 300,000 times the distance from the Earth to the sun. How might we travel to Alpha Centauri, the next-nearest star? And how long would it take to get there? Read about star travel via conventional propulsion, warp drives, and more.
Red rainbows happen when the sun is on the horizon. They’re created in much the same process that causes a sunset or sunrise to look red. Details – and more photos – inside.
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.
April 22, 1970 – Arbor Day – was the first Earth Day. Today, a common practice in celebration of Earth Day is still to plant new trees.
We’ll pass between Mars and the sun just one month from today, on May 22. Watch Mars brighten dramatically between now and then!
A rainbow isn’t a flat two-dimensional image on the dome of sky. It’s light along a three-dimensional cone, with your eyes at the tip.
Glories are common. They’re seen all the time by people traveling in airplanes. You need the sun to be directly behind your head. In front, you need an ordinary cloud. As you look toward the cloud, look for the shadow of the airplane. The plane’s shadow may be surrounded by a multi-colored circle of light. That’s the glory.
That glow over the unlit part of a crescent moon – called earthshine – is light reflected from Earth.
Beautiful photos in this post!
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?
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.