Category Archives: Physics

Theory, Theory, Who's Got the Theory

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Built on Facts: The Theory of Theory

Matt’s commentary on the idea of “just a theory” at the Language of Bad Physics Blog (to which I linked recently) along with a quick example.

I put “theory” in scare quotes not because amateurs can’t make contributions to physics – they can and do – but because there’s a heck of a lot of cranks out there with theories that aren’t actually theories. In physics, if you want to come up with a theory at minimum it has to:

1. Generate numbers.
2. Match those numbers consistently with observation.

If there’s one widespread trait among cranks, crackpots and other related species, it’s not understanding or accepting the concept of falsifiability, and why if one is wrong, one must be verifiably wrong. I suspect that they simply don’t accept the possibility that they could be wrong.

A Peek in the Closet

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Instruments for Natural Philosophy

In February 1975, Deborah Jean Warner, a Curator of Physical Science at the National Museum of American History, called me to ask if Kenyon had any historical physics teaching apparatus. I looked around my office, and reeled off the names of four or five good pieces of apparatus that I was using in my lectures. The next month I was at the Smithsonian, exploring the collection and photographing some of it in black and white and in color. Since then, I have visited and photographed nearly seventy collections of early physics apparatus. This web site displays pictures of about 1850 pieces of apparatus, along with text and references.

Who's Afraid of Ill-Tempered, Mutated Sea Bass

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But where are the sharks?

The Lab Lemming tells us we shouldn’t be afraid of laser isotope separation of Uranium, and then tells us what we should really be scared of.

[T]he critics of this planned laser separation technique don’t even explain how they expect proliferation to happen. It is just a vague sentiment that if this particular nuclear technology works, it will somehow spread to the hands of the bad guys.

You Keep Using That Word

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I Do Not Think “Adiabatic” Means What You Think It Means

The definition of “adiabatic” given above, namely a process that occurs very quickly, is amusing to me because it’s almost exactly the opposite of the definition I usually encounter. In my corner of cold-atom physics and quantum optics, when we talk about something being “adiabatic,” we almost always means that it’s a process that takes place slowly.

You should read the post that induced this, Letting Air Out of Tires, and its followup, Letting Air Out of Tires II (The Wrath of Lance Armstrong)

The Device That Goes 'Ping!'

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Why wood bats ‘crack’ and metal bats ‘ping’ and much more. Physics and Acoustics of Baseball and Softball Bats

There is a tremendous amount of physics and engineering that goes into the design of a baseball or softball bat, especially the new high-tech aluminum and composite bats which are currently dominating the market. There is also an amazing amount of physics involved in the bat-ball collision, and in the performance and behavior of the bat itself. My interest in the physics of baseball bats began in 1998 when I was setting up a laboratory experiment for my students and decided to have them look at the vibrational behavior of a youth baseball bat. Now, several years later, vibrational and acoustic analysis of softball and baseball bats has become my primary area of research. I have been able to correlate the vibrational frequencies of bat barrels to measured performance, and have signicantly contributed to an understanding of the trampoline effect in a hollow bat. In addition, my vibrational analysis of the bending modes of a bat has added to the understanding of perception and feel, including why some bats sting more or less than others.

tip o’ the baseball cap to Skye

Superluminal Man Meets The Microquark Kid

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Faster than light, smaller than an atom

What do you do when you get an unphysical answer on an exam, and is there any way to mitigate this?

Some combination of carrot and stick is the usual way; of course; when I had control over grading policy it was in the navy and we mainly used the big stick: grossly unphysical answers were conceptual errors and it meant a big loss of points on the question — there was no amount of correct information that would let you have a passing score on that particular problem. To drive this home, it was reinforced with feedback from homework and quiz results — I tried to not let an opportunity pass where I could point out how wrong such an answer was and how much it would cost come test-time. But it was also buttressed by having other divisions using similar grading policy, which is a knob not really available (or at least less accessible) in an academic setting.

It's Official: Lasers Are Cool

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The Most Amazing Laser Application of All Time Is…

The people have spoken, and it doesn’t get any more amazing than laser cooling, which is hereby awarded bragging rights over all other fields of laser-related physics.

Those of us who do laser cooling already knew this, but it’s nice that we have this stamp of approval. The post has links to explanations of all 12 of the contestants, done with the usual Uncertain Principles style and quality.