Science Feature
Stephen Hawking gets a taste of zero gravity

Stephen Hawking experienced a total of four minutes of weightlessness in a plane that dives through the sky to give passengers a taste of zero gravity (Image: Zero Gravity Corp). British physicist Stephen Hawking took a flight on Thursday that gave the renowned scientist, who is confined to a wheelchair, a taste of the weightlessness of space.

Hawking, 65, and an entourage of caretakers and other thrill-seekers, took off from the space shuttle's runway at Kennedy Space Center in a specially modified jet that dives through the sky to give passengers an experience of zero gravity.

They returned to the space center in Florida about two hours later after doing eight dives, giving him four minutes of weightlessness.

"It was amazing," Hawking said afterwards.

"Space here I come," he said, referring to his hope that the experience will prepare him for a real sub-orbital space flight in the future.

Hawking acknowledged before the flight that experiencing weightlessness, even for a few seconds, would be sweet relief from the bondage of a daily life immobilised by a debilitating and irreversible neuromuscular disorder.

Future in space

"I have been wheelchair-bound for almost four decades and the chance to float free in zero g will be wonderful," Hawking told a pre-flight news conference.

The acclaimed cosmologist and best-selling author of A Brief History of Time, who has posited theories to help explain black holes and other celestial phenomena, lost his ability for natural speech after a tracheotomy that followed a bout of pneumonia in 1985. He speaks with the aid of a computer-controlled voice synthesizer.

Hawking said in an interview on Wednesday that he feared that the human race did not have a future if it didn't go into space. "I therefore want to encourage public interest in space. A zero-gravity flight is the first step towards space travel," he said.

Suborbital flight

"Life on Earth is at an ever-increasing risk of being wiped out by a disaster such as global warming, nuclear war, a genetically engineered virus or other dangers," Hawking added at the news conference.

In a reference to his affliction, amyotrophic lateral sclerosis, or Lou Gehrig's disease, Hawking noted that his flight also would serve as a demonstration that "everybody can participate in this type of experience".

During these flights, participants experience at least one free-fall, lasting about 25 seconds, where they float up from the floor. The maneuver is accomplished as the plane flies towards the ground following a steep climb.

The ride, which normally costs $3500, was courtesy of Florida-based Zero Gravity Corp., which operates a commercial zero-gravity service similar to what NASA uses to train astronauts.

Hawking hopes the experience will lead to a suborbital spaceflight aboard a new passenger service being developed by Virgin Atlantic Airway's offshoot, Virgin Galactic. Commercial suborbital spaceflights are expected to begin in 2009.

(New Scientist Space and Reuters)

ET Should Write, Not Call

Robert Roy Britt

A fresh perspective on searching for aliens suggests that ET is more likely to send us something akin to a message in a bottle rather than relying on energy-intensive, inefficient radio messages.

The professional hunt for ET depends largely on huge telescopes that scan for electronic intelligence in the ether, on the assumption that a brainy, technologically advanced civilization might try to reach out to others, or that their communications would leak into space.

However, sending a signal across the cosmos is expensive and inefficient, argues Christopher Rose, a professor of Electrical and Computer Engineering at Rutgers University.

Tortoise and hare

Rose and physicist Gregory Wright initially set out to learn how to send the most information over a wireless channel. They then considered the amount of energy needed to send a signal over greater distances. As logic suggests, more energy is needed to send a message farther, and the signal weakens.

Radio waves, laser beams or X-ray pulses and other electromagnetic signals all travel at the speed of light. But the farther they go, the more they disperse. This makes them harder to detect.

"Think of a flashlight beam," Rose said. "Its intensity decreases as it gets farther from its source."

Seth Shostak knows about this problem. Shostak worked on the SETI Institute's Project Phoenix, a just-finished search for extraterrestrial radio signals (they didn't hear any) that is the most comprehensive so far. Not involved in Rose's research, Shostak wrote recently that sending a barely detectable radio-based signal across 100 light-years and in all directions would require 100 billion watts of power. Translation: You'd have to focus the output of all American power plants to do the job.

Interstellar radio programs face another problem in garnering listeners. Once an electronic signal passes its intended recipient, it is gone for good. If the creatures on a target planet have their electronic ears tuned to some other frequency when a signal arrives, or if they have yet to develop the right listening technology, the effort to make contact is wasted.

A written message in a space capsule, however, could have landed on Earth millennia ago and await discovery. A spacecraft, once up to speed, can cruise for long periods with little additional power input.

Time to spare?

The downside to the message-in-a-bottle approach: Human technology, at least, can't propel a spacecraft to even a significant fraction of light-speed. So getting a note from one star system to the next would take more generations than the average human mind can contemplate.

The most distant probe sent by earthlings is Voyager 1, just crossing the outer boundary of the solar system. After a 27-year journey it is 90 times the distance from Earth to the Sun, or nearly 8.4 billion miles (13.5 billion kilometers). A radio signal can go that far and back in about a day -- more than 26 years quicker!

The next nearest stars, in the Alpha Centuri system, are 4.3 light-years distant. That's more than 3,000 times what Voyager has so far covered. However, so long as time is not of the essence, Rose and Wright figure hard copy would be the preferred method to talk across the stars.

"If haste is unimportant, sending messages inscribed on some material can be strikingly more efficient than communicating by electromagnetic waves," Rose said.

Outbound examples

Further, he points out, long messages are handled more efficiently by inscription.

NASA's two Voyager probes exhibit such an effort. Each carries a 12-inch, gold-plated copper disk with sounds and images that portray terrestrial life and culture. The cost to send the records was practically inconsequential compared to the overall price tag of the mission, whose main purpose was to study the planets.

Radio pulses announcing anything more than "we exist" would consume more energy (which requires money) for every word.

Rose is not against listening. He just thinks looking might prove more fruitful. He also notes that messages might not arrive as language per se. Perhaps organic material embedded in an asteroid, the Moon or a satellite of Jupiter would reveal the presence of life elsewhere. That of course is not a new idea. Other scientists have considered that unintelligent (microbial) life could even travel between planets embedded in a rock kicked up by an asteroid impact. No calling card required.

(Source: Space.com)

Copyright (R) thedailystar.net 2007