Rhett Allain is an Associate Professor of Physics at Southeastern Louisiana University. He enjoys teaching and talking about physics. Sometimes he takes things apart and can’t put them back together.

11 thoughts on “About

  1. Hello Dr Allain

    I just read your Wired article on the effect of planting trees on CO2 etc. You didn’t mention what happens to the carbon sequestered by each tree when the tree dies. Does it just disappear?

    1. The tree could decay and then go back to CO2 or it could get buried in the ground and eventual turn into fossil fuels so that when aliens take over the planet in a billion years, they too can ruin the atmosphere with their giant SUVs

      1. So unless the stock of trees continues to grow the effect on CO2 is zero, not even the small amount you mentioned. It might be a good plan to submit a Corrigendum to the Wired article.

  2. I also enjoyed your Fermi calculation of the carbon that would be removed from the atmosphere if everyone planted a tree. You might also note that the root mass of a tree is roughly equal to its above ground mass. That’s only a factor of two, but I was surprised to learn this some years back. People have only recently started systematically measuring root systems.

  3. Dear Dr Allain,
    I enjoyed your article in PhysicsWorld about “The Fictional Science of Science Fiction”. There is a minor point I wanted to make regarding 2001 A Space Odyssey (one of my all time favorite movies) getting airlocks right. Although its treatment of gravity and inertia in the airlock scene is spot on, there is in fact an error in human physiology, namely that David Bowman is shown holding his breath in the scene. Actually this is not the right course of action as the pressure differential would rupture his lungs. The thing to do in such instances (I know, we’ve all been there…) is to exhale continuously as much as possible. Arthur Clarke was an experienced scuba diver and knew this well, but unfortunately was absent from the set on the day the scene was shot (see him discuss that in an interview: https://youtu.be/F7HGwVqI_FM at 29:05 ). There is a really good explanation of the physiology in this report on the submarine escape technique taught at the Royal Navy sub school: https://youtu.be/H7IcI4ecVwk starting at 1:20.
    I know this is only peripheral to the point you were making in the article but thought I would mention it.
    Best wishes,

  4. Hello Dr. Allain. I Read your equations for drones thrust and force and was trying to apply it to more equation in need to get a very important project rolling. I too have been flying whatever I could get my hands on since I was a child, including building myself a pair of wings and jumping of my 30ft high roof. Lucky enough I had enough noodles to at lease drag out my mattress to Cushing a crash if the wings didn’t work. And of course they didn’t. But now the neighborhood had a super fun activity to keep us occupied for a day or too. I eventually became an air traffic controller and inspector. Anyhow. I just need an answer to the question- “how much power in whatever expression you would like to call it, would I need to “LIFT* a total of 700lbs to 250FT”, altimeter 2992, humidity 50 no wind at all and no airfoil. A quatracopter, so air resistance would be involved, but minimally. Basically LAB CONTROLLED EVIROMENT.” Nothing fancy, just the basics. If someone was selling me a battery, I would know by the power output he gave me whether his battery would do what I need it to do. And that is to “LIFT* and fly forward at 75mph minimum for 100miles, and have at least 1 hour minimum of flight time.” Is that an easy one for you? And can you just send me the power, or kwh needed Please please? I’m not a scientist or mathematician. I just have a project I’m working on. And I’m finding it really difficult to get a straight answer from anyone. Thanks, Roger McCoy

  5. Good question for today, “Do my actions, help those around me, become better, than they ever thought possible?” Professor Allain, I think you model this, in your quest for learning, and the way you present things. Keep it up.

  6. Hello Dr. Allain,

    My name is Georgi Petkov. Just wondered if you are aware that there is another ‘Physics explained’ YouTube channel, which I have been following since 2018. Only mentioning – no association with that channel, other than being a subscriber.

    Best wishes

  7. I read your “What Happens If a Space Elevator Breaks” and found your analysis was incorrect, as was Apple’s Foundation TV show. As the ‘ribbon’ is moving at the same rate the planet’s surface below is, it doesn’t “wrap” around the planet, it drop’s straight down, very quickly and if it doesn’t burn up on the way down, it would pile up in the same place.

  8. I recently read your article on wired (https://www.wired.com/story/the-physics-of-the-n95-face-mask) about how N95 masks work, but I would like to point out that you have missed the equally important factor of Brownian diffusion and it’s role in filtering, as this is also a major part of mask effectiveness and comes into the layering of the mask and the duration of time particles spend in the ejective filtering region (and hopefully stay there ). I would politely request that your wired article be updated as this filtering process is made more effective with better Brownian diffusion (as described by the Darcy flow equations or good ol bitbanging Navier Stokes), but your article seems to indicate that it’s primarily electrodynamics at play when this is only partly true. Triboelectric materials are unarguably important, but please read this literature (https://doi.org/10.1063/5.0015044) and update your article accordingly.
    With all respect,

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.