21 November 2009 | NewScientist | 23

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IMAGINE a time machine that could show you the web of yesteryear. That’s the promise of Memento, a system demonstrated at the Library of Congress in Washington DC on Monday.

Memento eliminates the hassle of navigating deep archives of old web pages. It uses a modified browser and server to let users easily retrieve pages that were online on a certain date.

The system exploits the internet’s ability to get different content from the same URL – such as English or French-language pages – depending on the user’s computer settings. Memento users enter a date in the browser’s “time travel” menu, says developer Herbert Van de Sompel of the Los Alamos National Laboratory in New Mexico, and the server delivers pages that were online at that time.

Victorian videoconferencingWHAT began as an optical illusion

to thrill Victorians could one day be at

the forefront of videoconferencing.

London-based firm Musion says its

life-size “holograms” could bring

together people on opposite sides of

the world in a way that no competing

technology can.

In the 19th century, Henry Dircks

and John Pepper developed a ghostly

illusion. A viewer peers into a room;

a near-identical version of this main

room lies outside their line of sight

and a large sheet of glass is secretly

angled between the two. When light

falls on characters in the hidden room,

they are reflected onto the glass and

appear to the viewer as ghostly

spectres in the main room.

Musion has replaced the

unwieldy sheets of glass with a

100-micrometre-thick transparent

polyester foil, and switched

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Time travelhits the web

the live actors for a digital

light-processing (PLD) projector.

The action is filmed at a remote

location and transmitted using the

internet to a videoconferencing

suite. The projector and foil are

then used to project the life-sized

image into the room.

“It isn’t a hologram, it’s a virtual

image,” says Ian O’Connell, director

of Musion. “But it looks like people’s

expectations of a hologram.”

Unfortunately, the cost of the

equipment required to produce

the effect will probably keep the

technology from the consumer

market for several years.

PIEZOELECTRIC materials generate an electric field when deformed, and vice versa, and are found in everything from cigarette lighters to nanoscale motors. But the best-performing piezo material, lead zirconium titanate (PZT), falls foul of a European Union ban on lead in electronics.

Now an alternative has been found that works just as well and has a smaller environmental impact. It comes from Ramamoorthy Ramesh and colleagues at the University of California, Berkeley, who have developed a way to reproduce this

Piezo devices go lead-free

behaviour using non-toxic bismuth ferrite ( Science, DOI: 10.1126/science.1177046 ).

They start with a heated grid of square templates slightly smaller than the crystals bismuth ferrite normally forms. Bismuth ferrite is then deposited onto the squares with a laser. Some pieces of the deposited material match the shape of their template, but others skew into diamonds as they try to form the larger crystals natural to them. The resulting material deforms just like PZT when subjected to an electric field.

The team says applications could include ultra-dense data storage, where bits are stored in the shape of a particular region of the crystal.

–Pepper’s ghost lives on–

The number of times President Barack Obama has himself used Twitter – though he has more than 2.7 million followers

0

Lawyer Alexander Stopp wants English-language entries detailing his clients’ conviction for

murdering an actor in 1990 to be removed from Wikipedia, in accordance with German privacy

laws. The German version has already been taken down (The New York Times, 12 November)

“A criminal has a right to privacy, too”

“It isn’t a hologram – it’s a virtual image – but it looks like people’s expectations of a hologram”