Home › Science & Space

Science & Space?

The sky, the ocean, the moon, and why any of it happens. 24 questions and counting.

Why is the sky blue?Air molecules scatter short blue wavelengths of sunlight far more than red, so blue light bounces to your eyes from ever…
How far away is the moon?About 238,900 miles on average, far enough to fit every other planet in the solar system in the gap. And it is drifting …
Why is the ocean salty?Rain has spent billions of years dissolving minerals out of rock and rivers have delivered them to the sea, where water …
What causes lightning?Ice particles colliding inside storm clouds separate electric charge until the air itself breaks down and a giant spark …
How old is the Earth, and how do we know?4.54 billion years, give or take about 1 percent, measured by radiometric dating of meteorites and ancient minerals. Mul…
What is a black hole?A black hole is matter crushed so dense that within a boundary called the event horizon, not even light moves fast enoug…
Why do leaves change color in the fall?The yellows and oranges were in the leaf all summer, hidden under green chlorophyll. Shorter days shut down the chloroph…
What actually causes the seasons?Not distance from the sun; Earth is actually closest in January. Seasons come from the planet's 23.5-degree tilt, which …
Why is space black if there are so many stars?Because the universe has a finite age and is expanding. Light from the most distant stars either has not reached us yet …
How do vaccines work?They train your immune system on a harmless preview of a pathogen, so it recognizes the real thing and responds fast. Th…
What is DNA?The molecule that carries the instructions for building and running a living thing, written in a four-letter chemical al…
Does time really move slower in space?Yes, and it is measured, not theoretical. Speed slows time and gravity slows time, so clocks on the space station and on…
How do airplanes actually stay in the air?Wings deflect air downward, and the reaction pushes the plane up. The popular explanation about air traveling faster ove…
How fast is the speed of light, and why does it matter?About 186,282 miles per second, or 299,792,458 meters per second, and it is the universe's speed limit for anything carr…
What is the difference between a virus and bacteria?Bacteria are living single-celled organisms that reproduce on their own; viruses are not alive by most definitions and m…
Why can you see the moon during the day?Because the moon is bright enough to compete with the daytime sky and it is above the horizon during daylight hours for …
What is evolution, in plain terms?Populations change over generations because individuals with traits that help them survive and reproduce leave more offs…
Why does metal feel colder than wood at the same temperature?Because metal conducts heat away from your skin far faster. You are not sensing temperature, you are sensing heat loss, …
How do magnets work?Magnetism comes from the motion and alignment of electrons. In most materials the electron magnetic fields point randoml…
If there are billions of stars, why is the night sky dark?Because the universe has a finite age. Light from the most distant stars has not had time to reach us, and expansion str…
What is absolute zero, and can anything reach it?The temperature at which atomic motion reaches its minimum, minus 459.67 Fahrenheit. Nothing can reach it, because remov…
Why do humans have fingerprints?Not for grip, as long assumed. Testing found ridges may actually reduce friction on smooth surfaces. The better-supporte…
How does sunscreen actually work?Mineral filters like zinc oxide sit on the skin and scatter and absorb UV; chemical filters absorb UV and release it as …
Why does helium make your voice squeaky?It does not raise your pitch. Sound travels almost three times faster in helium, which shifts the resonant frequencies o…