The color of smoke depends on what’s burning, and how it’s being burned. Smoke can be black, white, or grey – and chemicals can even make it colorful. This week’s viewer question comes from Harfiz Abu B. from Ghana.

1816 became known in Europe as the "Year Without a Summer". The year before, Indonesia’s Mount Tambora had erupted in a huge explosion. Ash from the volcano darkened skies around the globe, resulting in failed harvests, famine and epidemics.

When does a volcano explode? And when does it erupt more gently, without an explosion? It's a question volcanologists are seeking to answer. No one can look inside a volcanic vent. But laboratory experiments can show how magma erupts and explodes.

Contrary to what photos taken by Apollo astronauts suggest, stars are indeed visible from the moon. But they appear differently to what they do here on Earth.

Clouds and fog both form when water vapor condenses. So what's the difference between them?

Solar panels convert sunlight into electrical energy, and have turned into a key contributor for making energy supplies more sustainable. But how do they actually work?

Fog coalesces when water vapor condenses. The resulting droplets reflect light and obscure vision. This week's viewer question comes from Dobrila B. from Bosnia and Herzegovina.

Some 7,000 light-years from Earth are gigantic cosmic columns of dust and gas. Because new stars are coalescing there, the formation is known as the Pillars of Creation.

Condensation trails are linear artificial clouds that form from the exhaust of airplanes. Do they have an effect on the climate? This week's viewer question comes from Al Ben M. in Panama.

In adults, blood is formed in short, flat bones like the ribs and sternum. This week's viewer question comes from Monica

Bustos in Colombia.