How Physicists At Fermilab Build a Bridge | Hacker News Reader

How Physicists At Fermilab Build a Bridge

joedoliner.com

27 pointsjdoliner10 comments

That strikes me as an obvious and not particularly noteworthy solution.

Disclaimer: I have a Physics degree.

Remember these are physicists so this solution only came after they spent hours trying to throw string across (you may neglect air resistance) float string across (you may neglect the mass of the string) and jump across (assume a spherical physicist in a vacuum).

The mathematicians came up with the string solution, but only after a few days of attempting to drop the ball of string from the bottom to the top because they had a different convention about coordinate systems.

I'd have expected the physicists to be first with the string theory. The mathematicians should have spent at least one week discussing knot topologies.

Slight catch. if you suspend a rope pendulum from a horizontal string, if the string flexes at all, it will essentially act like a longer pendulum perpendicular to the string (where the string moves) than it does along the string. The result is that the pendulum's swing has a different period along either axis, and it will trace out a lissajous pattern, not a straight line in its swing. And that sort of wrecks the idea of a focault pendulum.

Oops!

Better make sure your cable is REALLY tight.

If you can stretch a cable across a "chasm" chances are that you can pop an I-beam in there instead. That would solve that problem.

Because I-beams are perfectly rigid and don't flex at all?? I'm guessing "would render that problem so small as to be unnoticeable" but maybe the pendulum is so light that effects are drowned by random noise or don't exist - there must be a potential well to climb out of before lateral forces cause axial flexing so I'm probably wrong.

Another cute thing about Wilson Hall at Fermilab is that the front doors faces precisely due north. Not because they were constructed with painstaking precision but because the physicists have redefined Fermilab's coordinate system such that north is defined as the direction Wilson Hall faces.

If you every have a chance to visit fermilab, I highly recommend it. The 20-story pendulum is only one of many cool science geek things unrelated to the accelerators you can see.

IEEE used to offer special tours. Don't know whether they still do.

And if you do, be sure to visit the museum on the 15th floor of the High-Rise. It has some great information in it.

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