Flying over thunderstorms

I find thunderstorms fascinating. They terrify me. But when I think about them – about the physics of the storm itself – they delight me with their beauty.

From my present vantage, about 30,000 feet above the Earth in a Southwest Airlines flight, I have a unique perspective on one big storm between New Mexico and Texas. We’re skirting the storm on its southern side. The scale of the system is deceptive. From where I sit, the lightning flashes inside the clouds, or between the clouds, seem as flickering fluorescent lightbulbs in need of replacement.

Yet, each of those flashes represents the complete breakdown of air between two points in space, the molecules of water, nitrogen and oxygen ripped apart by the electric field filling the space between what will become the origin and destination of the lightning strike. Once pulled apart and stripped of electrons, the air becomes a plasma – a cloud of ions and one of nature’s most perfect conductors. This is the end for air – and a great burst of light erupts in the electric field as photons are sprayed during the ionization process. Photons, those quanta of the electromagnetic field, free stream from the clouds to my eyes, where they seem to be from but a distant and harmless flicker.

Some of the lightning strikes are muted flashes in the clouds, their ferocity cloaked by thick curtains of water vapor. Others are clear and jagged streaks in the sky, a naked wire hanging in space for a tenth of a second and glowing as bright as the sun. I can imagine the great magnetic fields generated by these lines of electric current, the interplay of Maxwell’s Equations written in the sky as moving electric charge generates magnetic fields. Those magnetic fields are touching the skin of our aircraft, inducing eddy currents in the plane’s surface. Current makes magnetic field, and changing magnetic field makes current. Faraday would be pleased.

The electric fields required to rip apart air and water are vast, and the energy released in the breakdown is immense. On the ground, such energy is capable of splitting whole trees in half as they seek the ground, on their way vaporizing liquid water in plants and blowing apart the cells that form the building blocks of the unfortunate tree. I am trying not to think about what such a strike would do to the engines of a jet.

The storm recedes behind us, its passing in relative motion behind us a harbinger of storms to come to West Texas, and perhaps even to Dallas. The fate of this weather system is hard to predict, depending on too many variables. Somehow, the complex interplay of water and ice that gave rise, through friction and the beautifully named “triboelectric effect”, to the show of lightning and thunder seems less difficult to understand than the dynamics and movement of this entire storm system. Either way, I am delighted to have seen it, and delighted that it’s behind us.

Process: going from the lecture room to the web

I thought it might be useful to jot down some notes on my process this semester for going from the lecture room to the web with my course material. Since starting to teach at SMU, I’ve tried each semester to (1) make available lecture media for students and even the general public, with preference to having it available for my students and (2) making that process as simple as possible to minimize my time.

That said, I am quite proficient on multiple software platforms, including Linux, Mac OS, and Windows. That makes some things a lot easier for me. I tend to use Linux and Mac OS, so that’s where my process starts.

I currently record lecture audio using my iPad. I find that the microphone is just great in that for picking up omnidirectional sound. It seems to capture student questions sufficiently well in a room of about 60 students, and it certainly picks up audio from the lecturer or lecturers in the room. I don’t have to lug an external mic around with me any more.

I get the audio into my personal cloud so that I have a backup of it, and can then download it to another machine for editing the audio, adding video, etc. I currently use the ownCloud application to do this. I run a server at home, with about 3TB of storage available through my own private ownCloud server. The iPad application can send files from the iPad to the ownCloud instance, so after lecture I tell the recording application (AudioMemos) to send the .wav file to my ownCloud server. An 1.5 hours of lecture is about 500MB, so this takes some time to upload. During this phase, I get other work done, or get a coffee and a sandwich.

At home, I then download the audio from my ownCloud server. I edit the audio using Audacity, if I only want to make an audio lecture podcast.

If I want to make a video lecture podcast, I use Kdenlive. I pull the audio into the Kdenlive project editor. To place slides in the video stream, I dump my PDF to a bunch of graphics files, e.g.

convert -density 150 lecture.pdf lecture-%03d.png

and then pull the images files into the Kdenlive project and drop them so that they sync up with the audio stream.

Sometimes, I shoot video in class. If there is a demonstration, it’s nice to have video of it. I’ve found the easiest thing to do, if you have a Mac, is to just use QuickTime to record a movie and then upload the movie to ownCloud via a web browser. If using Linux, the program Cheese works just find for capturing video.

Syncing the video with the audio is the hardest part. I usually zoom way in on the video and audio streams in Kdenlive and drag the video until the sound tracks from the podcast and the video line up (I can hear the same words spoken at the same time in the two audio tracks, with less than a 1/10th of a second delay). Then I delete the video’s audio track and lock the video and audio together so that they can be edited as a single entity. This can be the most time consuming, but I usually find it never takes more than 1 hour to edit a lecture (audio, video, slides) into a ready-to-export video project.

I then render a single video file from Kdenlive. I like to export in Ogg Video format (OGV). I can then upload this to YouTube or another service and share the link with students.

Here are my resources for the above workflow. Your mileage may vary.

  • AudioMemos: an iPad app for recording audio. Simple. Lets you pause the recording and resume later, as needed.
  • Audacity: an open-source audio editor for all platforms.
  • ownCloud: run your own secure cloud
  • Kdenlive: a KDE-based video editor. Linux and FreeBSD (Mac OS) only.
  • Recording video in lecture: QuickTime Player on Mac OS, or Cheese on Linux.

James and the Little Neutral One – Going Up Alleys, Episode 7

Professor James Loach (Shanghai Jiao Tong University) talks to SMU undergrad Nicole Hartman and me about the elusive neutrino.
Professor James Loach (Shanghai Jiao Tong University) talks to SMU undergrad Nicole Hartman and me about the elusive neutrino.

On this episode of “Going Up Alleys,” we hear from Professor James Loach (Shanghai Jiao Tong University) about the elusive subatomic particle known as the “neutrino,” Italian for “little neutral one.” I am joined this time by SMU undergraduate Nicole Hartman, a 2012 SMU President’s Scholar and my co-interviewer for this podcast.

This episode is centered on some audio I once recorded for the “Mustang Physics Podcast,” but which never saw the light of day in that podcast.



Going Up Alleys – Episode 7 – James and the Little Neutral One

James Loach is Professor of Physics at the Shanghai Jiao Tong University in China. His doctoral and post-doctoral work have focused on the properties of the neutrino. He was part of the team at the Sudbury Neutrino Observatory (SNO) in Canada that resolved the “solar neutrino problem” – the observation that too few electron-type neutrinos come from the sun – by definitively concluding that neutrinos can change form (e.g. electron neutrinos can morph into muon neutrinos, a physical process called “oscillation”). This observation is part of the modern basis of all future neutrino studies, including the ongoing quest to measure the tiny, tiny mass of the neutrino.

SMU undergraduate Nicole Hartman
SMU undergraduate Nicole Hartman

Nicole Hartman is an SMU President’s Scholar hailing from Lewisville, TX. She joined us as an undergraduate at SMU in 2012 and among her many other academic and non-academic activities has been active in leadership in the SMU Society of Physics Students (SPS). Nicole and I had the pleasure of interviewing James when he came to SMU in the fall of 2012 to work with our dark matter colleagues and give a seminar on his neutrino work. Please enjoy!



Show Notes

  • 0:00: Opening Theme and Title
  • 0:51: Introduction – the story of the neutrino
  • 7:19: Interview with James Loach
  • 22:26: Closing Remarks – the future of the neutrino and the value of basic science
  • 24:58: Closing Theme and Credits
  • Music for the podcast is licensed under Creative Commons and is by the artist, Nicoco. The song used in the podcast is “Occipital,” from the album “Classicoco,” and is available from Jamendo.
  • This podcast was produced at Hampton House. Linux and Ubuntu were used in the making of this podcast, as was a Macbook, a set of BLUE Microphones, Audacity, and an reasonably insignificantly small amount of “too much free time.”