The trailer-mounted radar is a "phased array" type - it scans the sky with a narrow beam which flicks between thousands of locations each second.

BBC: Fact file: Patriot missile defence

In fact, there has since been a wide-array of other gold-type ETFs that have hit the market, like the iShares Gold Trust (NYSEArca: IAU) and the ETFS Physical Swiss Gold Shares ETF (NYSEArca: SGOL).

FORBES: GLD: King Gold

Mr. Rosenberg also spoke without notes although he presented a dazzling array of charts, graphs, and small-type slides that were rarely on the screen long enough for the audience to decipher.

FORBES: Two Views Of The Future

It is done using a special type of liquid-crystal array developed by a British firm called Light Blue Optics, which is also developing the technology for use in tiny projectors (see article).

ECONOMIST: Monitor