Orbital structures are becoming increasingly important for worldwide communications and a new generation of technologies. But scientists are warning that the danger of space debris (碎片)is rapidly increasing . Space debris can include pieces of old rockets, non-operational satellites, lost tools and other parts. These pieces of wreckage present a risk to spaceships, satellites and space stations.

In an effort to reduce the amount of debris orbiting the Earth, some experts suggest creating “orbital-use fees.” A group of economists at the University of Colorado at Boulder proposed a yearly fee, or tax, on satellite operators for their use of an orbital path. The group’s study on the subject appeared recently in the publication Proceedings of the National Academy of Sciences.

Matthew Burgess helped write the study. He said in a statement: “Space is a common resource, but companies aren’t accounting for the cost their satellites impose on other operators when they decide whether or not to launch. So we need a policy that lets satellite operators directly factor in the costs their launches impose on other operators.”

Akhil Rao was the lead writer of the study. He said most proposed answers to the problem have been based on using technology to clear away the debris. Some suggestions, for example, call for nets or other devices that capture the space wreckage. But, Burgess said that removing debris only means that operators will launch more satellites. He said an international treaty calling for a yearly fee or tax would push companies to be more mindful about launching more objects into space.

Christopher Newman is a professor of space law at North Umbria University in Britain. He told the Thomson Reuters Foundation that carrying out a space tax could be tricky. Newman noted that such a cost could be seen as a restriction on the free use of space. That freedom is guaranteed in the Outer Space Treaty of 1967. The United Nations document has been signed by more than 100 nations. Newman added that the effort to place a fee on the use of space could easily be slowed by the many details involved.

Rome — Doctors and medical groups around the world last weekend reacted with strong opposition to the news that an Italian specialist is on the brink of cloning the first human baby.

Dr. Severino Antinori, who is the head of a hospital in Rome, has been referred to in an Arab newspaper as claiming that one of his patients is eight weeks pregnant (怀孕) with a cloned baby.

Antinori refused to comment on the reports, but in March 2001 he said he hoped to produce a cloned embryo (卵) for implantation within two years. So far seven different kinds of mammals have already successfully cloned, including sheep, cats and most recently rabbits.

Doctors showed their doubt and were strongly opposed although they admit that human cloning would finally come true unless there was a world wide ban on the practice.

Professor Rudolf Jaenisch of the Whitehead Institute for Biomedical Research at the Massachusetts Institute of Technology: “I find it astonishing that people do this where the result can be foretold that it will not be a normal baby. It is using humans as guinea pigs. It makes people feel sick.”

But Ronald Green, director of the Ethics Institute at Darmouth College in the US, said it is unlikely that an eight-week-old pregnancy would lead to a birth.

So far all cloned animals have suffered from some different serious disorders, many of them dying soon after their births.

Doctors are opposed to human cloning because they are worried about the welfare of the cloned child if there is one.

“There are no benefits of cloned human beings, just harm,” said Dr .Michael Wilks of the UK.