# balloon

### Ask Ethan #14: The Highest Energy Particles in the Universe

"The results of my observation are best explained by the assumption that a radiation of very great penetrating power enters our atmosphere from above." -Victor Hess You might think of the largest and most powerful particle accelerators in the world -- places like SLAC, Fermilab and the Large Hadron Collider -- as the source of the highest energies we'll ever see. But everything we've ever done hear on Earth has absolutely nothing on the natural Universe itself! For this week's Ask Ethan, let's take a look at the simple question of our reader David Hurn, who asks: Ever since I was a young…

### The Physics of a Sad Balloon

My birthday was two months ago, and SteelyKid's was the weekend before last, so we've had balloons running around the house for a good while now. Meaning that when I came into the library yesterday, I saw the sad little image on the right: a half-deflated Mylar balloon floating at about chest height. Now, the first thought of a normal person on seeing this would be "Why didn't we throw this away a while ago?" My thought, since I've been on a bit of an everyday physics kick for a little while now, was "Hey, physics!" "What do you mean?," you ask. "What physics is there in the sad balloon? It…

### How big of a balloon do you need to get to 120,000 feet high?

I am still thinking about the Red Bull Stratos Jump. Sorry, but there is just tons of great physics here. Next question - how big of a balloon would you need to get up to 120,000 feet? I am not going into the buoyancy details of Archimedes Principle - I think that was covered fairly thoroughly with the MythBusters floating lead balloon. However, in short, here is a force diagram for a floating balloon. For a floating balloon, the buoyancy force must equal the weight of the whole thing. It turns out that the buoyant force is equal to the weight of the gas (or fluid) the object displaces…