Which falls faster, a hammer or a feather?

Does as heavy object fall faster than a lighter one? What about a much lighter one? Check out this video clip where astronauts on the moon find out!

Apollo 15 Astronaut David Scott performing a science demonstration on the moon in 1971!

During the Apollo 15 mission on the moon, Commander David Scott performed a science demonstration for all the world to see! He dropped a geologic hammer and a falcon feather and dropped them at the same time. Which do you think hit the ground first?

Scott was testing a famous theory by Galileo Galilei, who said two objects dropped from the same height would would fall at the same rate, regardless of their mass. Legend has it that he tested his theory by dropping different sized balls off the Leaning Tower of Pisa, but this is now thought to be untrue.

In his 1634 book Two New Sciences, Galileo wrote that if it was possible to create a vacuum, any two falling objects would travel the same distance in the same time. He meant that if you could take away other factors, gravity would increase the speed of the two objects at the same rate, even if they were different sizes. That is, they would have the same rate of acceleration. We didn’t have a way to create a vacuum back in 1634 to test his theory, but it turned out that he was correct!

His theory was already proven by 1971 when the Apollo 15 astronauts were on the moon. The experiment had been already been done in vacuum chambers here on earth. But the moon was a perfect place to demonstrate this science principle since its surface is essentially vacuum!

The moon has very little air in its atmosphere, so there was no air resistance and the feather fell at the same rate as the hammer, just as Galileo had concluded hundreds of years before! In a vacuum, all objects fall at the same rate regardless of mass. Way to go, Galileo!

On Earth, where our atmosphere is filled with ntirogen and oxygen and other gases, the hammer would hit the ground first—not because it’s heavier, but because the feather encounters air resistance on the way down. Have you seen a feather fall before? They are light enough, they could even be carried upwards by a gust of wind. That is why it is significant to study gravity in a vacuum. We are able to remove the variables of other forces that might affect what we observe.

Galileo Galilei

Is There Sound in Space?

Is it possible to hear sounds in space? The short answer is no . . . mostly! 😀

In almost every science fiction movies or TV show, you hear spaceships speeding through space or shooting laser beams. That is entertaining, but sound doesn’t work this way in real life. Sound doesn’t travel in a vacuum, and much of space is a vacuum, so that should be an easy answer.

But . . . to be completely correct, not all of space is a vacuum. It’s full of clouds of gas and dust that are the remains of old stars or the beginnings of new ones. And sometimes that gas is dense enough to carry sound waves, just not sound perceptible to humans.

In 2003, NASA’s Chandra x-ray telescope detected ripples in the gas cloud in the Perseus Cluster and determined that they were sound waves from a nearby black hole. It made one droning note, deeper than we could ever hear. The note is a B-flat, 57 octaves below middle C, which is roughly a million billion times lower than the lowest frequency of sound we can hear.

So while you absolutely can’t hear sound in the vacuum of space, there may be a whole symphony of sounds in distant gas clouds that perhaps only alien ears could ever hear. Those sound waves won’t ever travel to us, though, because sound still can’t travel in a vacuum!

A scene from 2001: A Space Odyssey, one the few science fiction movies to depict total silence in its scenes in space, and also one of Mr. Yuck’s favorite movies!

Is the Sun Yellow?

We all reach for the yellow crayon when it’s time to draw the sun, right? And we know the sun is yellow because Superman gets his superpowers from a “yellow star.”

But light is a tricky thing! In space, the sun would appear white. By the time we see light from the sun, it has traveled 92,955,807 miles through space and through our atmosphere, which bends and filters light.

Colors like blue, green and violet scatter more easily than yellow, orange and red. This gives the sun a yellowish color throughout the day and an orange/reddish tint when it is near the horizon, even though it would be white if viewed from space. Sorry, Superman!

By the way, don’t look straight at the sun during the day to check! That might hurt your eyes!

Typical representation of our yellow sun!