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FAQs

Why do fireflies light up?

By in Earth | Jun 14, 2013

You can see what looks like trails made by fireflies, via long-exposure photography from EarthSky Facebook friend Jack Fusco Photography. There's also a single meteor in the upper left of this photo. See it? It's straighter than the firefly trails.

Click here to expand image above

Some experts think the firefly’s flashy style may warn predators of the insect’s bitter taste. On the other hand, some frogs don’t seem to mind. They eat so many fireflies that they themselves begin to glow. Male fireflies also light up to signal their desire for mates – and willing females attract the males with flashes of their own. But not all the flashing of fireflies is motivated by romance. While each firefly species has its own pattern of flashing, some females imitate the patterns of other species. Males land next to them – only to be eaten alive.

The secrets of night shining clouds

By in Earth | Jun 10, 2013

Night shining clouds, South Pole via NASA/HU/VT/CU LASP

What are noctiilucent clouds? Glowing silver-blue clouds that sometimes light up summer night skies in polar regions, after sunset and before sunrise, are called noctilucent or night shining clouds. Scientists studying these clouds have found that year-to-year changes in them are closely linked to weather and climate across the globe.

How much do oceans add to world’s oxygen?

By in Earth | Jun 08, 2013
Phytoplankton - the foundation of the oceanic food chain. image via NOAA

Phytoplankton – the foundation of the oceanic food chain. Scientists estimate that phytoplankton contribute between 50 to 85 percent of the oxygen in Earth’s atmosphere. Image via NOAA

Scientists agree that there’s oxygen from ocean plants in every breath we take. Most of this oxygen comes from tiny ocean plants – called phytoplankton – that live near the water’s surface and drift with the currents. Like all plants, they photosynthesize – that is, they use sunlight and carbon dioxide to make food. A byproduct of photosynthesis is oxygen. Scientists estimate that phytoplankton contribute between 50 to 85 percent of the oxygen in Earth’s atmosphere.

When did the turtle get its shell?

By in Earth | Jun 05, 2013
Photo credit: Laszlo Iyles

Photo credit: Laszlo Iyles

The evolutionary origin of a turtle’s hard protective shell has long puzzled scientists. New fossil evidence published in the journal Current Biology on May 30, 2013 suggests that turtle shells may have started to evolve in reptiles 260 million years ago, which is 40 million years earlier than previously thought.

Is it true that Jupiter protects Earth?

By in Space | Jun 04, 2013
Brown spots mark the places where fragments of Comet Shoemaker-Levy 9 tore through Jupiter's atmosphere in July 1994. Image and caption via Wikimedia Commons.

Brown spots mark the places where fragments of Comet Shoemaker-Levy 9 tore through Jupiter’s atmosphere in July 1994.

Here’s a question we get regularly:

Is it true that Jupiter could be considered our friendliest planet because – without Jupiter – comets would be more likely to hit us?

The answer is yes … and no. Some astronomers believe that one reason Earth is habitable is that the gravity of Jupiter does help protect us from some comets. Long-period comets, in particular, enter the solar system from its outer reaches. Jupiter’s gravity is thought to sling most of these fast-moving ice balls out of the solar system before they can get close to Earth.

What’s the difference between comets and asteroids?

By and in Space | Jun 04, 2013
Comet Lovejoy reflected in the water of Mandurah Esturary near Perth, on December 21, 2011. Image Credit: Colin Legg.

Comet Lovejoy reflected in the water of Mandurah Esturary near Perth, Australia on December 21, 2011. When comets come near the sun, they often sprout glorious tails. Image via Colin Legg.

Astronomers announcement yesterday (June 3, 2013) that the peculiar asteroid P/2010 A2 has a tail much longer than previously supposed once again blurs the line between asteroids and comets. What’s the difference between comets and asteroids?

If you made a sphere of all Earth’s water, how big would it be?

By in Earth | Jun 03, 2013

All the water on Earth would fit into a sphere 860 miles (1,385 km) wide. Image via Jack Cook/WHOI/USGS

We think of Earth as the water planet. But what if you could take all of the water on Earth and form it into a sphere, or bubble? How big would the bubble be?

What’s the birthstone for June?

By in Earth | Jun 03, 2013
Photo credit: Valentyn Volkov/Shutterstock

Photo credit: Valentyn Volkov/Shutterstock

Happy birthday to all our June friends! Your month has three traditional birthstones – pearl, moonstone, and alexandrite. Pearls, according to South Asian mythology, were dewdrops from heaven that fell into the sea. They were caught by shellfish under the first rays of the rising sun, during a period of full moon. In India, warriors encrusted their swords with pearls to symbolize the tears and sorrow that a sword brings. More ….

What is a Dyson sphere?

By in Space | Jun 02, 2013
View larger. | Here is a completely fantastic artist's concept of a Dyson sphere. I like it. Notice the little moon on the left side, being ravaged for raw materials. Via FantasyWallpapers.com

View larger. | A fantastic artist’s concept of a Dyson sphere. The image is called Shield World Construction, and it’s by Adam Burn.

Proponents of solar power know that only a tiny fraction of the sun’s total energy strikes the Earth. What if we, as a civilization, could collect all of the sun’s energy? If so, we would use some form of Dyson sphere, sometimes referred to as a Dyson shell or megastructure.

What causes rainbow colors in clouds?

By in Earth | May 28, 2013
Iridescent clouds seen by EarthSky Facebook friend Mike O'Neal in Oklahoma on May 27, 2013. Thank you, Mike.

Iridescent clouds seen by EarthSky Facebook friend Mike O’Neal in Oklahoma on May 27, 2013. Thank you, Mike.

Sky watchers on occasion report seeing colors in the clouds, and sometimes our friends send photos of these rainbow colors in clouds. You’ll find some examples in this post. These colorful clouds are called iridescent clouds, and the phenomenon is called cloud iridescence or irisation. The term comes from Iris, the Greek personification of the rainbow. Click inside for some amazing photos and info about iridescent clouds.