“Properties of Expanding Universes”, which Hawking wrote when he was a 24-year-old graduate student in 1965, long before he became one of the world’s most famous scientists, is now available to all, with its faded typewriter-keystrokes and scrawled handwriting.
We have had a huge response to Professor Hawking’s decision to make his PhD thesis publicly available to download, with almost 60,000 downloads in less than 24 hours, said Stuart Roberts, a spokesman for the University of Cambridge.
As a result, visitors to our open access site may find that it is performing slower than usual and may at times be temporarily unavailable.
I love how proper the University’s response was to their system crashing. Carry on.
We skewered some baseballs and Wiffle balls and used a wind tunnel to measure the forces “lift, drag, and side or lateral forces” as functions of things like the airspeed and spin rate. For the Wiffle ball, we also varied the orientation of the ball with respect to the airflow, making our own version of the manufacturer’s pitching instructions.
With perforations on either side of the ball, we found that the Wiffle balls experienced a lateral force that generally acted to push the ball toward the position of the holes. Things got more complicated when the perforations were on the upstream portion of the ball. As shown in the first image below, fog traces the airflow over a ball with the holes facing the flow, with a symmetric wake pattern suggesting that if we untethered the ball it would fly straight. The second image shows the flow over a ball with its holes facing up, and a wake that is deflected upward, meaning that the ball is experiencing a downward force.
I would be equally interested in learning the dynamics of how the hollow, thin Wiffle Bat impacts distance of hitting a Wiffle Ball when compared to a bat that was different in structure.