Photo: Rhett Allain

With the introduction of the electric field in introductory physics courses, the first thing is a calculation of the electric field due to a point charge. But who has actually seen a point charge? I mean, sure — an electron would be a point charge, but you can’t really see it.

Most textbooks go on to introduce macroscopic objects like a solid metal (conducting) sphere with excess electric charges. With a conducting sphere, the following should be true:


Photo: Rhett Allain. Experimental setup to measure Avogadro’s number. This picture doesn’t really have anything to do with this post.

We have a problem with science education, and it seems like it’s getting worse every year.

In pretty much every university for every undergraduate degree program, students have to take a science course. I think even three science courses is very common. But why? Why does a student majoring in history, or economics, or even business? The answer is that a college degree isn’t about job training, it’s about human growth. Students take classes (and have other experiences) that help them become more complete humans. So, part of this means that students need to understand the nature of science. …


Screen Capture: Keynote Equation Editor

It’s just part of writing in science and maths — you are going to have to include some equations at some point. Of course, there are many options:

Yes, LaTeX is about more than just writing equations, but if you just know the equation code you can make some nice looking equations fairly quickly. Some…


Photo: Rhett Allain. The backyard after the storm.

Just for my own historical archive, I’m going to share some of the details and pictures from both before and after hurricane Ida. We live in Hammond, Louisiana — which saw some significant damage during this storm. OK, let’s get started. I will post a picture and then give some type of narrative each photo.


Photo: Rhett Allain. Dog on a Stand-up Paddleboard

I saw this great video on reddit. It shows an incident with a dog on a stand-up paddle board. I’m going to go over all the cool physics things that you can see here. Let’s get to it.

The first step is to get some data. I’m going to load this video into my favorite video analysis program — Tracker Video Analysis (it’s free). The basic idea is to mark the location of objects in each frame of the video. This will give position and time data. The time values come from the video frame rate, however the position…


Photo:Rhett Allain. Two bouncing balls and one dog.

Take a ball and drop it on the ground. Yes, it will bounce back up. However, it doesn’t return quite to its starting height — it never does. Even a “super bounce” ball doesn’t return to its starting height. Why? Well, one way to think of this is that the ball starts with some gravitational potential energy that is converted to kinetic energy as it falls. When it collides with the ground, some energy is then transferred into thermal energy in the ball and ground. This means it has less total energy to get up to the starting height.

You…


Photo: Rhett Allain. The family dog in infrared.

It wasn’t that long ago that it would be completely unrealistic for normal humans to own an infrared camera. I think it was around 2010 that I ordered an IR camera for work — it had a price of around $3000. That’s pretty pricey.

But now, there are a bunch of low price cameras. Most of them connect to your phone and cost under $200 (I’m a big fan of the FLIR One, but Seek Thermal is also nice).

OK, I want to get to the pictures (and videos) but I think we need just a very brief introduction to…


Image: Rhett Allain. Object at L2 near a binary star system (created with Glowscript/Vpython)

I didn’t plan on writing this. My goal was to make a series of videos exploring all the cool aspects of Lagrange points (video playlist here). However, stuff gets complicated and I made some mistakes. So, here I am — trying to fix those mistakes. Oh, one more thing. My goal wasn’t to find the locations of Lagrange points, it was to build my own model (mostly from scratch) to calculate these things.

Introduction to Lagrange Points

Wait. What the heck is a Lagrange point? In short, there are 5 locations (labeled L1 — L5) near the orbit of two…


Image: NASA. Illustration of the Mars Helicopter.

It’s the end of the introductory physics course. That means that the students have seen some of the very fundamental ideas in physics such as:

Really, that’s all you need to explore some really cool physics. In this case, it’s time to use these ideas to build a model of helicopter thrust and power. With that, we can look at some awesome helicopter examples. Let’s get started.

Hovering Helicopters

Suppose you have a helicopter hovering such that it has a zero acceleration. …


So, it appears that the athletes in the Tokyo Olympic Village have cardboard beds. The rumor was that these were “anti-sex” beds that would collapse with more than one human (thus to prevent sex stuff). However, this might not actually be true.

But still, as athletes will do — they want to see how much these cardboard things can withstand. In the video above, you can see 9 dudes jumping on the bed before it gives in. Of course, it’s physics — so let’s get to it.

Standing on a Bed

The first way to “break” a bed is…

Rhett Allain

Physics faculty, science blogger of all things geek. Technical Consultant for CBS MacGyver and MythBusters. Former WIRED blogger.

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