This means that all of the stars in the universe must be moving away from Earth. If all of the stars are moving away, the Universe itself must be expanding. It was this discovery of the Doppler Effect in star light that led to the Big Bang Theory. (Science Clarified) The Tacoma Narrows Bridge collapsed on November 7, 1940. Incredibly, the whole collapse was caught on tape. Watching the tape, it is clear that the bridge collapsed from instability caused by enormous waves moving with periodic motion through the structure of the bridge. It is not clear, however, what caused this wave motion in the first place, or what caused it to get progressively worse until it destroyed the bridge. The cause of the collapse of the bridge continues to be a subject of debate among engineers.

The Tacoma Narrows Bridge was one of the earliest and longest suspension bridges. It was built to withstand winds of up to 120 miles per hour. The builders, however, did not take into account that wind has frequency, and that if that frequency were to match the natural frequency of the bridge, together they would create resonance, causing vibrations to occur much more strongly than they otherwise would. This is what may have happened in November of 1940. From the day the bridge was built, even a moderate amount of wind would cause it not only to sway from side to side but also to take on transverse undulations up and down the length of the bridge. These transverse waves are the ones that can be seen in the video. The bridge begins to vibrate torsionally with the wind, but then the wind and the bridge...

Finally, despite the structural strength of the bridge, the compounded force of the frequency of the wind and the frequency of the bridge's own movement increases the amplitude of the waves and tears the bridge apart.
Structural engineers and aerodynamicists have argued recently that in order for resonance to have had that strong of an effect, the wind would have had to maintain a precise frequency for a good length of time. It is highly unlike that would have happened naturally. Instead, they argue that the bridge entered a state of "fluttering" or "self-excitation" caused by aerodynamic instability. (Vibration Data Page) Regardless of the true cause behind the collapse, a more thorough understanding of wave mechanics by the bridge's designers could only have made a more stable bridge, and might have prevented its destruction.

Works Cited

"Atom Model History." Center for Teaching and Learning in the West. Colorado State University. Web. 15 May 2010.

"Doppler Effect." Science Clarified. Web. 15 May 2010.

"Ernest Rutherford." SLAC National Accelerator Laboratory Virtual Visitor's Center. Stanford University. Web. 15 May 2010.

Irvine, Tom. The Tacoma Narrows Bridge Failure. Vibrationdata. Web. 15 May 2010.

Jones, Richard K. The Well-Tempered Timpani. Wesleyan University Department of Music. Web. 15 May 2010.

Nelson, Sheila M. The Violin and Viola: History, Structure, Techniques. New York: Courier Dover, 2003. Print.