Repost: From MIT OpenCourseWare: Walter Lewin’s Lecture On Lightning

March 27, 2009 / chr1 / Leave a comment

My brief summary:

So at room temperature, the electrical breakdown of dry air at 1 meter of distance is 3 million volts (at which point you have discharge sparks, visible light and heat, and moving air).

Go and shuffle your feet on the carpet and touch the doorknob and if you see a spark of 3 mm it’s around 10,000 volts on average according to this calculation (a little prickle on the fingertip, maybe through your hand).

In the very large electrical field generated during a thunderstorm (400,000 storms every day on earth) you can get up to 300 million volts and more, blinding light and up to 50,000 degree F superheated air rushing outward in waves, or thunder. The current should it ground itself through your body, can clearly kill you:

(Language)

Through induction the stepped leader has made contact with the earth, and the return strokes travelling back up to the cloud are visible and audible.

**Of course, if you go and look at the nearest light bulb, the current passing through the resistive filament also produces light and some heat.

That’s my oversimplification. Listen to the lecture, it’s worth it. A whole semester’s worth of his lectures are available for free at that link.

From NOAA: Tornado Safety Guide

March 15, 2009 / chr1 / Leave a comment

Full post here.

We’ll be hearing about tornadoes in the news in the next month or so, so I thought I’d post a link to a safety preparedness page (if you live in a tornado prone area).

Here’s a video from Tornado videos of a huge wedge tornado in Manitoba:

Notice how at 1:30 or so the pressure is so low around vehicle (getting sucked into the vortex) that the gentleman riding shotgun can’t open the door against it. That’s pretty close.

From Strange Maps: It’s All Greek To Me

March 2, 2009March 2, 2009 / chr1 / Leave a comment

Full post here.

The map itself isn’t so impressive, but it’s an interesting thought. Someone made a cartogram of many different languages’ point of reference to other languages as ones that seem unintelligible.

“Mutual incomprehension results from the right mixture of inter-lingual proximity and unintelligibility. In the Middle Ages, for example, when the monks’ knowledge of Greek was waning, they would write in the margin of texts they could not translate, in Latin: “Graecum est, non legitur” (”This is Greek to me, I can’t read it”).”

From Scientific American: Was Einstein Wrong?

March 1, 2009March 3, 2009 / chr1 / Leave a comment

Full article here.

Can philosophy/metaphysics effectively help to deepen physics…or will it always be a way of attaching particulary deep thought (if done well) to even deeper thought?

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The authors, philosopher trained in physics David Albert and writer Rivka Galchen point out a problem they think ought to be focused on:

“-In the universe as we experience it, we can directly affect only objects we can touch; thus, the world seems local.

-Quantum mechanics, however, embraces action at a distance with a property called entanglement, in which two particles behave synchronously with no intermediary; it is nonlocal.

-This nonlocal effect is not merely counterintuitive: it presents a serious problem to Einstein’s special theory of relativity, thus shaking the foundations of physics.”

I’m pretty sure I’m not qualified to answer…

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See Also: David Albert’s turn on bloggingheads with Sean Carroll.

Also, maybe it’s a trend (writers moving directly to science)? Writer Louisa Gilder has a book out called “The Age Of Entanglement” on much the same subject, which she discusses here too on bloggingheads.

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Further: The enlightenment happened, so if you’re going to make a successful metaphysical theory, it’s good to try and understand the mathematical sciences of the day and go from there (Newtonian mechanics for Kant), like Kant did:

Michael Friedman’s Kant And The Exact Sciences tackles the subject ( I know him not and of course this too is more metaphysics and certainly not the mathematics of today…but if you’re going to be carrying Kant around …it’s good too understand how deep he went, what he seemed to understand and what he may have not understood at all about the Enlightenment explosion around him).