geeber - Slashdot User

Comment: Re:Standard Missing Option Gripe (Score 1) 708

by geeber on Wednesday November 11, 2009 @01:46PM (#30062642) Attached to: Sci-Fi Shows and Movies Should Stop...

""I Am Legend" was the only Will Smith movie I've seen where he isn't just reprising his Will Smith character."

Yeah, but Charlton Heston got it right the first time around in The Omega Man...no need for a remake on this one.

:)

Vincent Price got it right the first time around in the Last Man on Earth...no need for a remake on this one

Comment: Re:Time compression? (Score 3, Informative) 183

by geeber on Monday September 28, 2009 @06:11PM (#29573051) Attached to: "Time Telescope" Could Boost Fibre-Optic Communications

"Please describe how 'time-compressing' a waveform is different than frequency-shifting it"

If I frequency shift a waveform by a factor of 2, then the time compression is also a factor of 2. The article doesn't really mention it, but the frequency shifts in this experiment are much less than a factor of 2, but the time compression is from 2.5 ns to 95 ps, a factor of 27 compression.

This is a real time lens. A spatial lens works by imparting a quadratic spatial phase to light. Diffraction then causes the beam to focus due to the quadratic spatial phase.

A time lens works in analogy to a spatial lens by imparting a quadratic temporal phase to a light pulse. Propagation in a dispersive media then leads to the time compression.

The difficulty is it is very hard to impart a quadratic phase to short light pulses. The only real way to do it is nonlinear optics, which is where the (small) frequency shifts mentioned in the article come from.

Challenges Ahead In Final Hubble Servicing Mission 130

Posted by CmdrTaco on Monday May 11, 2009 @08:49AM
from the good-luck-up-there-guys dept.

Hugh Pickens writes "Space shuttle Atlantis is slated to lift off Monday on the fifth and final servicing mission to Hubble with four mission specialists alternating in two-astronaut teams will attempt a total of five spacewalks from Atlantis to replace broken components, add new science instruments, and swap out the telescope's six 125-pound (57-kilogram) batteries, original parts that have powered Hubble's night-side operations for nearly two decades. 'This is our final opportunity to service and upgrade Hubble,' says David Leckrone, senior project scientist for the Hubble Space Telescope. 'So we're replacing some items that are getting long in the tooth to give Hubble longevity, and then we'll try to take advantage of that five- to 10-year extra lifetime with the most powerful instrumental tools we've ever had on board.' Some of the upgrades are relatively straightforward and modular: yank out old part, put in new. But they're big parts: The 'fine guidance sensors' sound delicate but weigh as much as a grand piano back on Earth. But what's different this time is that the astronauts will also open up some instruments and root around inside, doing Geek Squad-like repairs while wearing bulky spacesuits and traveling around the planet at 17,000 mph. 'We have this choreographed almost down to the minute of what we want the crew to do. It's this really fine ballet,' said Keith Walyus, the servicing mission operations manager at Goddard. 'We've been training for this for seven years. We can't wait for this to happen.'"