When a worm is chopped in two, the missing part often re-grows. Researchers at several biotech companies are challenging the assumption that humans can't perform a similar feat by developing drugs that encourage self-regeneration.

Hydra Biosciences is working a regeneration drug that stimulates heart muscle-cell regrowth, and could lead to better recoveries for heart attack sufferers. The protein-based drug induces mature cells to become a little bit like stem cells.

Hydra hopes its cardiac-muscle drugs will prove to be just the tip of the regenerative medicine iceberg -- the company is already considering investigating ways to re-grow retinas in macular degeneration sufferers and pancreatic cells in diabetics.

Other companies are starting to explore regenerative techniques as well. Genzyme, for instance, has developed a little-known drug called Carticel, which is FDA-approved to regenerate damaged cartilage and has proven useful in treating slow-healing knee injuries. Meanwhile, Epicell, in the United Kingdom, is developing ways to generate sheets of extra skin from the body's own epithelial cells, techniques that are becoming instrumental in many types of reconstructive and plastic surgery.

It seems too good to be true: a new source of near-limitless power that costs virtually nothing, uses tiny amounts of water as its fuel and produces next to no waste. If that does not sound radical enough, how about this: the principle behind the source turns modern physics on its head.

Randell Mills, a Harvard University medic who also studied electrical engineering at Massachusetts Institute of Technology, claims to have built a prototype power source that generates up to 1,000 times more heat than conventional fuel. Independent scientists claim to have verified the experiments and Dr Mills says that his company, Blacklight Power, has tens of millions of dollars in investment lined up to bring the idea to market. And he claims to be just months away from unveiling his creation.

The problem is that according to the rules of quantum mechanics, the physics that governs the behaviour of atoms, the idea is theoretically impossible.

Dr Mills's idea goes against almost a century of thinking. When scientists developed the theory of quantum mechanics they described a world where measuring the exact position or energy of a particle was impossible and where the laws of classical physics had no effect. The theory has been hailed as one of the 20th century's greatest achievements.

More than 470 physicists, including seven Nobel laureates, have signed a petition to oppose a new U.S. Defense Department proposal that allows the United States to use nuclear weapons against non-nuclear states.

"While it has long been a U.S. policy to use nuclear weapons in order to respond to a nuclear attack," said Hirsch, "the new policy allows the U.S. to use nuclear weapons against states that do not have nuclear weapons and for a host of new reasons, including rapid termination of a conflict on U.S. terms or to ensure success of the U.S. forces."

"Humanity has gone more than half a century without using nuclear weapons, in large part because of the success of the Nuclear Non-Proliferation Treaty," said Griest. "The U.S. use of nuclear weapons against non-nuclear states will destroy the Nuclear Non-Proliferation Treaty and give strong incentive for other countries to develop and use nuclear weapons, thus making nuclear war more likely. As physicists we feel we need to bring this to the attention of policy makers and the public, in order to engender discussion, debate, and hopefully repudiation of the new policy."

A synthetic chemical similar to the active ingredient in marijuana makes new cells grow in rat brains. What is more, in rats this cell growth appears to be linked with reducing anxiety and depression. The results suggest that marijuana, or its derivatives, could actually be good for the brain.

In mammals, new nerve cells are constantly being produced in a part of the brain called the hippocampus, which is associated with learning, memory, anxiety and depression. Other recreational drugs, such as alcohol, nicotine and cocaine, have been shown to suppress this new growth. Xia Zhang of the University of Saskatchewan in Saskatoon, Canada, and colleagues decided to see what effects a synthetic cannabinoid called HU210 had on rats' brains.

They found that giving rats high doses of HU210 twice a day for 10 days increased the rate of nerve cell formation, or neurogenesis, in the hippocampus by about 40%.

This was the 15th Ig Nobel Prize ceremony, and it was every bit as riotous as its predecessors. Hundreds of students fired paper airplanes toward the Sanders Theatre stage, where they landed at the feet of the real Nobel Laureates who were there to hand out the goofy awards.

There were 10 prizes this year: The Ig Nobel Prize in medicine went to Gregg Miller, inventor of Neuticles, artificial testicle replacements for neutered dogs and other animals, which come in different sizes and levels of firmness.

Another gross-out idea won this year's Ig Nobel Prize in fluid dynamics: Two European researchers calculated the pressure that builds up inside a penguin about to go potty, and reported their findings in a paper entitled "Pressures Produced When Penguins Pooh -- Calculations on Avian Defaecation" (.pdf).

The Ig Nobels, which are organized by the magazine Annals of Improbable Research, recognize the most bizarre and hilarious achievements in science and the arts. Annals editor Marc Abrahams says the Ig Nobels honor research that "first makes people laugh, then makes them think."

Scientists have created eerie zombie dogs, reanimating the canines after several hours of clinical death in attempts to develop suspended animation for humans.

Pittsburgh's Safar Centre for Resuscitation Research has developed a technique in which subject's veins are drained of blood and filled with an ice-cold salt solution.

The animals are considered scientifically dead, as they stop breathing and have no heartbeat or brain activity.

But three hours later, their blood is replaced and the zombie dogs are brought back to life with an electric shock.

Duing the procedure blood is replaced with saline solution at a few degrees above zero. The dogs' body temperature drops to only 7C, compared with the usual 37C, inducing a state of hypothermia before death.

Software scientists at Microsoft Research have teamed up with biomedical researchers in Seattle, Boston and Perth, Australia, to see if computer techniques used to defeat e-mail spam can also be used to help design a vaccine that can defeat AIDS.

"HIV mutates like crazy, but it does show a pattern," said Dr. David Heckerman, a physician and computer scientist at Microsoft Research.

"HIV mutates by making errors in its (genetic) copying," Jojic said. But it can make only so many errors, he said, if it hopes to retain the genetic equivalent of the spammer's intended e-mail.

Deep in the basement of a dusty university library in Edinburgh lies a small black box, roughly the size of two cigarette packets side by side, that churns out random numbers in an endless stream.

The machine apparently sensed the September 11 attacks on the World Trade Centre four hours before they happened - but in the fevered mood of conspiracy theories of the time, the claims were swiftly knocked back by sceptics. But last December, it also appeared to forewarn of the Asian tsunami just before the deep sea earthquake that precipitated the epic tragedy.

Although many would consider the project's aims to be little more than fools' gold, it has still attracted a roster of 75 respected scientists from 41 different nations. Researchers from Princeton - where Einstein spent much of his career - work alongside scientists from universities in Britain, the Netherlands, Switzerland and Germany.

It is possible - in theory - that time may not just move forwards but backwards, too. And if time ebbs and flows like the tides in the sea, it might just be possible to foretell major world events. We would, in effect, be 'remembering' things that had taken place in our future.

Scientists have begun blurring the line between human and animal by producing chimeras—a hybrid creature that's part human, part animal.

Chinese scientists at the Shanghai Second Medical University in 2003 successfully fused human cells with rabbit eggs. The embryos were reportedly the first human-animal chimeras successfully created. They were allowed to develop for several days in a laboratory dish before the scientists destroyed the embryos to harvest their stem cells.

Irv Weissman, director of Stanford University's Institute of Cancer/Stem Cell Biology and Medicine in California, is against a ban in the United States.

"Anybody who puts their own moral guidance in the way of this biomedical science, where they want to impose their will—not just be part of an argument—if that leads to a ban or moratorium. … they are stopping research that would save human lives," he said.

Some cancers are caused by heterocyclic amines, DNA-damaging chemicals found in cooked meat and fish. When Sakae Arimoto-Kobayashi's team at Okayama University in Japan fed these chemicals to mice, the DNA damage to their liver, lungs and kidneys was reduced by up to 85% if the mice drank non-alcoholic beer instead of water.

Heavy alcohol consumption is blamed for around 6% of all cancers in western countries (New Scientist print edition, 18 December 2004), though moderate consumption reduces the risk of heart disease. Since the mice drank non-alcoholic beer, the findings do not show whether moderate consumption of normal beer has any anti-cancer benefits.