weber88

The explanation given here is pretty decent:

http://en.wikipedia.org/wiki/Classical_electromagnetism_and_...

The main thing is to consider how charge densities change as we switch reference frames. Because the lengths contract when we switch to a reference frame where things are in motion, we see higher charge densities (same charge per less length).

A simple demonstration: Say we have a charge neutral, current carrying wire. We model it as a bunch of positive charges staying still, and some negative ones moving. The positive and neutral balance, but there is still a current because only the negatives are moving. Now imagine we switch to a different reference frame, one where the negative charges aren't moving, but the positive one's are, we are flying along parallel to the current. Now the positive charges contract relativisticly, so the density of positive charges is now greater than the negatives, and hence the wire appears to be carrying a net charge.

I've come to be suspicious of anything in finance claiming to be "mathematically optimal". You can only optimise according to some simplified model, and simplified models of complex systems have a tendency to unpredictably break down.

Just a question that popped into my head: what would happen if everyone followed a passive strategy, ie, no one was active? Isn't some sort of active strategy required, somewhere, for funds to be directed at all?

Though, I do think on average fund managers probably don't actually make anything like useful predictions. But perhaps we do need someone, somewhere, looking for good investment.

My guess is that there is a role in society for some conservative, value based investing, but at the moment there are more people trying to do this than is useful, and even more people trying to find good investments by worthless strategies (like trying to predict future movements from past movements).

Oddly, I read it as having an orthogonal subject: not having skills, but demonstrating them. The presentation seems to be aimed at the sort of entitled mindset that believes employers will _just_know_ that they deserve 40k fresh out of college. Whether you have skills or not, if all you do is write your bachelors degree and some dot-points on your resume, you're not going to get much credit from employers.

Of course, as your skills go up, the chance that you'll get credit for them increases. Truly world class skills would market themselves. The point, however, is that there _is_ an independence between your skills and employers perception of them. It's not always going to be obvious to an employer that you can provide them with value.

It's not enough to simply have skills. It's necessary to demonstrate them, to get them out there. The techniques the presenter outlines might be familiar to someone who has done some reading on the general subject, but to the sort of entitled mindset that the presentation seems to be directed at, they mightn't be so obvious. Blogging, building a portfolio, networking: basic stuff to some, but not to everyone.