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Posts Tagged ‘Feynman diagram’

Saving the Feynman van

Monday, May 12th, 2014

A version of this article appeared in symmetry on May 8, 2014.

A team of Richard Feynman’s friends and fans banded together to restore the Nobel laureate’s most famous vehicle.

A team of Richard Feynman’s friends and fans banded together to restore the Nobel laureate’s most famous vehicle. Image courtesy of Seamus Blackley

“The game I play is a very interesting one,” says Nobel Laureate Richard Feynman in a low-resolution video posted to YouTube. “It’s imagination in a tight straitjacket.”

Feynman is describing his job as a theoretical physicist: to lay out what humanity knows about how the world works, and to search the spaces in between for what we might have missed.

The video shows more than Feynman’s way with words. It shows his approachability. One of the greatest minds that particle physics has ever known stands barefoot, lecturing in a distinct Queens, New York, accent for an audience lounging casually on the floor at the new-age Esalen Institute in Big Sur, California.

In a way, Feynman remains approachable to this day for all of the snippets of his personality left behind in books, letters and recordings of formal and informal lectures and interviews.

Recently, a more concrete bit of Feynman history came out of retirement: A small team has brought back to life the so-called “Feynman van.”

One camper, special order

In 1975, Feynman and his wife, Gweneth Howarth, bought a Dodge Tradesman Maxivan and had it painted with Feynman diagrams, symbols Feynman had invented to express complicated particle interactions through simple lines and loops.

It might seem arrogant to drive around in a van covered in reminders of one’s own intellectual prowess. But Feynman’s daughter, Michelle, thinks the decorations represented something else: a love of physics.

“My dad was pretty low-key about himself,” she says. “I think decorating the van was more to celebrate the diagrams than to celebrate himself.”

Michelle’s parents put a lot of thought into the design of the vehicle, which they primarily used for camping, Michelle says. It was outfitted with a small hammock for Michelle to use in case the family of four needed to sleep inside during inclement weather.

“I don’t think that they had ever done anything like that with a car purchase before,” Michelle says. “It was always: Go to the dealer and find something—it doesn’t really matter what color it is—and you’ll have it for a million years.”

The Feynman family took the van to Canada, Mexico and dozens of US campsites in between, often traveling with a couple of other families, often leaving the paved road for the unknown.

Michelle began driving the van to school after she turned 16.

“I thought it was kind of embarrassing,” she says. “But at a certain point I kind of got over it. If you want to drive at that age, you’ll drive anything.”

After Michelle’s first couple of years in college, one of her father’s friends, film producer Ralph Leighton—Feynman’s drumming partner in another famous fuzzy YouTube clip—bought the van and put it into storage, where it began to rust and fade.

Saving the Feynman van

When video game designer Seamus Blackley, known as the father of the Xbox, got ahold of the van in 2012, “it was just about too late,” Blackley says.

Blackley has a history with particle physics. He was in his early 20s, working on his PhD thesis at Tufts University and Fermi National Accelerator Laboratory, when he saw his plans for the future disintegrate with the defunding of the planned Superconducting Super Collider.

“I found out on CNN,” he says.

He changed course and wound up taking a job working on some of the first computer games with 3D graphics. He designed the physics of the game environments, “keeping things from going into other things.” He has helped shape the world of video games in a variety of different roles since.

Game design takes the same type of thinking Feynman described in his talk at the Esalen Institute, Blackley says. A designer must creatively solve problems without breaking the rules that keep the environment realistic—“and then you have to have a lot of intuition about how to make it fun.”

In 2005, Blackley moved to Pasadena, California, just miles from where Leighton was keeping Feynman’s van. Oblivious to his proximity to the famous camper, Blackley nonetheless began to make a hobby of restoring classic Italian cars.

It was fellow Pasadena resident Michael Shermer, founder of the Skeptics Society, who told him about the van in 2012. Blackley knew right away that he had to help save it.

“The universe is telling me I’ve gotta do this,” he says.

With the help of Leighton and Shermer, along with a donation from Feynman fan and world-class designer Edward Tufte, Blackley registered the van as a historic vehicle and brought it to his preferred restoration specialists in Los Angeles.

The van’s Feynman diagrams, which were painted poorly in the first place, turned out to be too degraded for restoration. So a pinstriper re-painted them, taking care to replicate the quality of the original work.

“It looks like this crappy job again,” Blackley says with a smile. “You see the brush marks and everything.”

After the restoration, Blackley prepared to ship the van across the country for a Feynman-themed exhibit by Tufte, held at Fermilab.

Keeping the Feynman spirit alive

The test of whether the specialists had stayed true to the original came when Blackley invited Michelle to come see the van before its next big trip. She came with her 11- and 13-year-old children.

It didn’t look brand new, Michelle says, but it was as if it had been rewound 30 years, back to the days when her father was still in the driver’s seat. She told Blackley and her kids about the times her father slept on the floor below her hammock.

“As a father now, you appreciate what that means,” says Blackley, who has an 11-year-old son.

A camping van incongruously covered in physics notations seems to be a fitting symbol for a man who couldn’t seem to help thinking about particle physics, Michelle says.

“I think it was impossible for him to turn it off,” she says. “I remember in the car there was a Kleenex box, and the back of it had been used for equations. Every little piece of paper and every waking moment was fair game.”

Richard Feynman died of cancer in 1988 at the age of 69. But projects like the van restoration keep his memory alive, Michelle says.

“He would’ve been an amazing grandfather, and he never had the opportunity,” she says. “So I’m thrilled that there are so many people around who want to share his spirit and his life so my kids can get a sense of who he is.”

Kathryn Jepsen

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Let’s draw Feynman diagrams!

Sunday, February 14th, 2010

Greetings! This post turned into a multi-part ongoing series about the Feynman rules for the Standard Model and a few of its extensions. I’ll use this first post as an index for all of the parts of the series.

  1. Let’s draw Feynman diagrams! (this post)
  2. More Feynman diagrams.
  3. Introducing the muon.
  4. The Z boson and resonances.
  5. Neutrinos.
  6. The W boson, mixing things up.
  7. Meet the quarks.
  8. World of glue.
  9. QCD and confinement.
  10. Known knowns of the Standard Model. (summary)
  11. When Feynman Diagrams Fail.
  12. An idiosyncratic introduction to the Higgs.
  13. A diagrammatic hint of masses from the Higgs
  14. Higgs and the vacuum: Viva la “vev”
  15. Helicity, Chirality, Mass, and the Higgs
  16. The Birds and the Bs
  17. The spin of gauge bosons
  18. Who ate the Higgs?
  19. Unitarization of vector boson scattering
  20. Private lives of Standard Model particles (summary)

There are few things more iconic of particle physics than Feynman diagrams. These little figures of squiggly show up prominently on particle physicists’ chalkboards alongside scribbled equations. Here’s a ‘typical’ example from a previous post.

The simplicity of these diagrams has a certain aesthetic appeal, though as one might imagine there are many layers of meaning behind them. The good news is that’s it’s really easy to understand the first few layers and today you will learn how to draw your own Feynman diagrams and interpret their physical meaning.

You do not need to know any fancy-schmancy math or physics to do this!

That’s right. I know a lot of people are intimidated by physics: don’t be! Today there will be no equations, just non-threatening squiggly lines. Even school children can learn how to draw Feynman diagrams (and, I hope, some cool science). Particle physics: fun for the whole family. 🙂

For now, think of this as a game. You’ll need a piece of paper and a pen/pencil. The rules are as follows (read these carefully):

  1. You can draw two kinds of lines, a straight line with an arrow or a wiggly line:propagator2types
    You can draw these pointing in any direction.
  2. You may only connect these lines if you have two lines with arrows meeting a single wiggly line.
    QEDvertex
    Note that the orientation of the arrows is important! You must have exactly one arrow going into the vertex and exactly one arrow coming out.
  3. Your diagram should only contain connected pieces. That is every line must connect to at least one vertex. There shouldn’t be any disconnected part of the diagram.
    connected
    In the image above the diagram on the left is allowed while the one on the right is not since the top and bottom parts don’t connect.
  4. What’s really important are the endpoints of each line, so we can get rid of excess curves. You should treat each line as a shoelace and pull each line taut to make them nice and neat. They should be as straight as possible. (But the wiggly line stays wiggly!)
    wibblywobbly

That’s it! Those are the rules of the game. Any diagram you can draw that passes these rules is a valid Feynman diagram. We will call this game QED. Take some time now to draw a few diagrams. Beware of a few common pitfalls of diagrams that do not work (can you see why?):

notallowed

After a while, you might notice a few patterns emerging. For example, you could count the number of external lines (one free end) versus the number of internal lines (both ends attached to a vertex).

  • How are the number of external lines related to the number of internal lines and vertices?
  • If I tell you the number of external lines with arrows point inward, can you tell me the number of external lines with arrows pointing outward? Does a similar relation hole for the number of external wiggly lines?
  • If you keep following the arrowed lines, is it possible to end on some internal vertex?
  • Did you consider diagrams that contain closed loops? If not, do your answers to the above two questions change?

I won’t answer these questions for you, at least not in this post. Take some time to really play with these diagrams. There’s a lot of intuition you can develop with this “QED” game. After a while, you’ll have a pleasantly silly-looking piece of paper and you’ll be ready to move on to the next discussion:

What does it all mean?

(more…)

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