Recent content by David Lewis

Grammar is social currency. If universities aim to produce productive citizens, grammar may seem secondary to technical skills. But if the goal is to cultivate successful citizens, grammar is essential: it enriches self‑expression and shapes how others perceive intelligence. Grammar snobs run...

I’m working on a sci-fi novel and part of the process is building a consistent story world. While the plot includes magical and fantastical elements, I want the underlying “rules of the world” to be scientifically accurate wherever possible. My goal is to make sure the physics and technical...

"Looks like I'm in the placebo control group."

In the Canary Islands there is not one canary. And in the Virgin Islands, same thing -- not one canary there either.

Is L the rest length of the wagon?

If you have two masses, each moving at 0.9c in opposite direction, the separation speed would be 1.8c. However, your question asked about the speed measured from one of the masses.

I think both clocks will record the same time in all frames. The flash bulb is equidistant between the two clocks, and the clocks are synchronized*, so the reading on both clock faces will show that the light hit them at the same time. * In the train frame

It helps to draw your diagram approximately to scale. Then you can tell if the answer you came up with is in the ballpark (sanity check). If you draw the correct arrangement of the 1.3kg force vector on the ball, the drag vector you are solving for, and the 25-degree angle in the right place...

This one has set up a gift shop at the exit.

OK. You had to be there.

No worries, Russ. This is not the appropriate forum for me to ask questions, solicit input, respond to valid criticism, or learn from mistakes.

Thank you. I have made the corrections.

1. In this system the sun boils Freon in a solar panel. 2. Freon vapor is sent to a turbine or piston motor. 3. Freon discharge from the motor is sent to condenser coils submerged underwater. 4. The cooled, low-pressure Freon is sent back to the solar panel inlet. 5. The Freon-powered motor...

In the Canary Islands, there is not one canary. In the Virgin Islands, same thing. Not one canary there either.

This one has set up a gift shop.