One of the teaching units I enjoyed most in my physics classroom was on wave motions. Almost everything is capable of some sort of waving motion, or oscillation. The motions come in a wide range of frequencies and amplitudes dependent upon the object. Smaller objects tend to have high frequencies and small amplitudes. Large objects tend to have low frequencies and large amplitudes of motion. It is a fascinating field of study.
Some objects respond to an input of energy of some specific frequency and begin oscillating with the same frequency as the source. Their motion can grow in amplitude as the source of energy continues. A simple example is a pendulum with a child on a swing. Pushing the child at the right time inputs energy to drive the amplitude larger. The energy of drawing a violin bow across the strings of a violin sets some of the strings into vibrations that are large and produce sound. This response to the driving action goes by the name of resonance. A previous post of mine on resonance can be found here.
The resonance response can be so strong that large vibrating objects reach amplitudes that can be easily seen or felt. Between July and November 1940, the new suspension bridge across Tacoma Narrows responded to various strength winds by doing some gentle waving motions as motorists crossed it. Some called the bridge Galloping Gertie.
On 7 November 1940, a half mile long section of the suspension bridge was set into a waving motion none had seen before by a steady 42 mph wind from the side. It collapsed and fell into the narrows. The video of that event is a classic one used by physics teachers every year to dramatically demonstrate the effect of resonance.
Every year I showed that video I thought it would be fascinating to actually see the bridge location and the replacement constructed in 1950. I finally got to do that. While vacationing in Tacoma, we were staying only a few miles from the bridge. I had to go see it and walk out on it if possible. We found a small War Memorial park next to a parking lot a short distance from the highway leading to the bridge.
After crossing the highway, we were treated to this view. Today, there are two bridges. The one on the right is the 1950 replacement of the one which fell into the narrows. It carries one-way traffic across to the other side. The left bridge was opened in 2007 and carries one-way traffic the other direction. The walkway was only available on the new bridge.
The total shore-to-shore bridge length is 1 mile (1.6 km). It is 0.5 miles from the near to the far support towers. We walked to the halfway point of the left bridge. At the lowest point on the walk is where the steel suspension cables are attached.
The scale of the bridges is huge. The towers rise nearly 500 feet above the piers. Due to the high speed traffic flow, the noise was quite intense. It would have been good to have ear plugs. There was a lot of road dirt blown into our eyes, too.
We neared the center of the span and saw two workers walking on the cables doing some inspections.
Finally, we reached the middle. This intrepid explorer posed for the shot. I finally had my up close and personal experience with the Tacoma Narrows bridges. It was the final lesson for me about that fascinating physics event. I was happy.
Gertie doesn’t gallop any more. Engineers modified the structure to make it and future bridges safer. I didn’t get to be on the actual replacement bridge either. However, the view was excellent. This is toward the northwest from the center of the span.
Click to embiggen.
How I See It 
To paraphrase Paul Harvey, “…and now the rest of the story.” Thanks for the epilogue.
I had a great time seeing this first hand. I can close the lesson plan book on that one.
Love the name Galloping Gertie; that must have been quite an experience in the past.
Well done, Jim. I enjoyed this vicarious visit and your excellent photos!
For any who want to know more about bridges, I recommend this episode of Stuff You Should Know, one of my favorites. It also mentions the Tacoma failure.
Thank you, Jim. It was hard to appreciate how big those bridges are until we started walking toward the middle. That is a good link. Thanks for it.
Ah, Home Sweet Home….My understanding is that the locals weren’t in any hurry for a replacement bridge, and now there is enough traffic to demand two bridges. Ah, well. Wave action was one of my favorites in physics, too, and I loved the Galloping Gertie story. Thanks for sharing this. Love the picture of you in the middle 🙂 And the wonderful view.
As to violins, resin on the bow helps the bow on the strings resonate. Couldn’t resist.
Right you are about the resin. Do you play?
World War II also slowed the progress toward replacing the bridge. The traffic was heavy at mid-morning when we were out on it.
Thanks for stopping by.
In third grade someone sat us all down and put violas into our hands, hoping to entice us. I wasn’t unwilling, necessarily, but definitely overwhelmed. Visually they are such a treat. Do you play?
Guitar…self-taught, electric, blues.
That is awesome, Jim. Do you play often?
Almost every day for an hour. I turn on some music I like and play along. I can’t read music or play chords. If I get the right key, I’m good to go.
Wow! I wish I could do that.
Reblogged this on Our View From Iowa and commented:
Jim’s great post about our visit to the Tacoma Narrows Bridge.
Reblogged this on Still Skeptical After All These Years and commented:
I wanted to reblog this, a fine travelogue because of the quality pictures!
I had trouble finding the reblog button. Now it is not on the black top bar, but only with the other shares. Moments of frustration ensued…
Me too, Melanie. WordPress can’t stop tweaking! 🙂
There were days in physics class when I had worked hard to get the settings and knobs just right on a demo. Invariably, some kid would stop to look and reach for a knob or touch something important. They learned after a while to not touch things just because you can.
I hear you.
I had heard about the bridge collapse, but didn’t see this video/film until high school (mid 60’s). It’s just amazing how flexible solid can be. Thanks for the walkalogue. 🙂
I would have done the same as the professor.
Vibration of apparently solid objects is amazing. Another demo I did showed the vibration of a cement block wall in the classroom. A laser was pointed directly at the wall. A small mirror was mounted on the wall to reflect the laser light back into the laser tube. The laser had an audio connector for an amp. A gentle tap with a fingertip would set the wall into a high frequency vibration lasting for 10-15 seconds. You could tell if someone was walking along the hallway on the other side of the wall.
For some reason…probably the idea of recognizing phenomena that are beyond our normal experience of life…this demo reminds me of some of the experimental results in “The Secret Life of Plants”, one of which found plants reacting in horror when Drano killed algae in a nearby sink drain.
Interesting early work by Stevie Wonder.
And on a more pleasing note….
Nice egret on the shoreline.
I first experienced wave motion on a swinging bridge at camp when I still was in grade school. We had a lot of fun with that bridge, and got warned off it a time or two, but I didn’t recognize what was going on with it until I saw the video of Galloping Gertie just a few years ago. It still amazes me.
i love that you went to visit the bridge. One person’s boring day is another’s destination travel!
Some of my earliest memories of the resonance phenomenon were from life on the farm. On some windy days, the stop sign by the road would start oscillating rapidly. Fun to watch. In the winter, ice would sometimes build up on the power lines. There were two, one above the other. Wind from the side would start them waving up and down until they touched. Wow! A blinding blue flash would dim the lights. They would start up again and touch. Eventually, the ice would be melted or knocked off to stop the process.
We have these trees behind the house whose fronds of leaves oscillate in the right breeze. Some wave one way and the next one will wave the other. Fun to watch.
Like the Queen wave.
I found this video which has audio and an explanation of the failure. And it also has the information that the car owner left his dog in the car where it perished…so if there was a professor he did not save the dog. I’ll not say how I feel about the dog owner.
This video also has two other things of interest. What I had remembered from the past was seeing a car disappear and reappear in the undulations. Also, the phrase “benign undulations” is used which seems a little ludicrous. I would think that, even without the twisting motion, over the years those undulations would have proven less than benign.
That was tragic that the dog was not saved. One newspaper account I read reported that the person got to the car and Tubby was threatening to bite him. He felt his life was in such danger that he abandoned his attempt.
Today, we know so much more about the stresses and behaviors on large structures like this one. Safety rules would not let people drive on it like they did then.
Thanks for the video. I hope others watch it, too.
This was such an interesting post, Jim. Thanks for the science and history lesson! 🙂
I am very happy you liked it. It was very meaningful to me because of the days spent teaching about it.
Thank you for your kind comments.
Ah! Now I wonder what the bridge sounded like. When I first moved to the coast and experienced my first earthquake I was shaken awake. I remember hearing a sound like a train approaching and thinking — waitaminute there are no trains on this island!
I watched a movie posted by Steve Gingold in this comment section. There are some sounds during the twisting phase of the bridge. I don’t know if they are actually from the scene. But, they do sound authentic based upon my knowledge about cables under great tension.
Those earthquake sounds would be eerie. Tornado winds can also give sounds like that.
I’m glad that as a physics teacher you finally got to see the site of the infamous bridge. I didn’t realize they’ve now doubled the replacement bridge, no doubt a response to the increasing population in the area.
I once went on a Tacoma odyssey of my own. My Peace Corps friend Tom Neville was born in Tacoma around the same time I was, but while he’d grown up there I had no recollection of the place. When I finally visited him in 1978 we went to Tacoma General Hospital and snuck into the then-closed old maternity ward to see where we’d both come into the world.
I read your description of the TGH visit to Melanie. We both got a chuckle out from it. I’m glad you found your roots. That is the same hospital we visited. Most looked very new.
The EMTs asked a couple of times where we wanted our son taken, which hospital? How would we know?? Son said, “Take me wherever they’re going to fix me.” We finally agreed on TGH because it was nearest. They did fine. 🙂
Then we can say that I had a birth there and he had a rebirth there.
I expect the EMTs deal mostly with families from the area, who might have a reason (doctor, insurance, closeness to home, etc.) for preferring one hospital to another.
I enjoyed the images! Thanks for sharing this fascinating post full of history.
My pleasure. It was a great culminating experience for me.
I thought it was interesting that the Newspapers.com blog posted about the anniversary of the bridge collapse — which happened on November 7th. You’ve included most of the information here, but I still thought you might be interested in seeing the article.
That was interesting. I clicked on the linked dog word near the end. It took me to the words of the person who tried to save it. He said the dog was so frightened it bit his hand when he opened the car door. He gave up to save his own life.
Thanks for the reference.