On this day in 2013, astronaut Luca Parmitano took a space selfie to remember.
When you hop on a swingset, you make yourself swing higher and higher by using your legs—propelling your body either forward or backward depending on the direction you’re swinging. This shift in the position of your legs happens at a specific point as the swing moves (can you think of it?!) in order to help you swing higher—hitting that point in the cycle is what creates resonance. The frequency required to hit that point every time is called the resonant frequency.
This is the same phenomenon that allows you to tap a basketball that is motionless on the ground, and continue to hit it so as to bounce it higher and higher without stopping. Notice how you can’t just randomly hit the ball and expect it to continue to bounce higher. When you dribble a basketball from the ground to your waist you are dribbling the ball at its resonant frequency. And if you were superhuman, you could continue to dribble the ball at its resonant frequency until the ball collapsed from the force.
Which is exactly that happened to the Tacoma Narrows Bridge!
The Tacoma Narrows Bridge collapsed just months after its opening, and sparked greater research in the aerodynamics and resonance of structures such as bridges and buildings that are greatly affected by wind and weather.
This is cool…..