Ask Mr Brain...all will be explained

PUBLISHED : Saturday, 31 July, 1999, 12:00am
UPDATED : Saturday, 31 July, 1999, 12:00am

What will happen if a bird's sperm goes into a human egg and develops into an embryo? LESANDA Maryknoll Convent School Scientists would be amazed if such a thing did happen. H G Well's story The Island of Doctor Moreau tells the tale of a demented scientist carrying out horrific experiments to produce human-animal hybrids. However, in reality such hybrids are impossible.

Reproduction is only possible between animals of the same species. In fact the usual definition of 'species' is animals which are able to reproduce together. As has been mentioned a few times in this column, chimpanzees and humans share more than 98 per cent of their genes in common. However it is impossible for even chimps and humans to breed. That one to two per cent difference in genes makes all the difference. Apart from the genetic difference, chimps have 24 pairs of chromosomes whereas humans have only 23. In order to reproduce successfully, male and female chromosomes have to match, which is impossible if the two species do not even have the same number.

A very few species are able to interbreed - female horses and male donkeys can breed to make mules (the other way round it is called a hinny). However, horses and donkeys are even more closely related than humans and chimpanzees are and even so their offspring are sterile.

Why is longitude and time measured from Greenwich in London? Lines of longitude are imaginary north-south lines which divide the earth for the purposes of navigation and for calculating time zones. Since there are 360 degrees of longitude, if you are 15 degrees to the east of a place, you are one hour ahead of it. Similarly, if you are degrees 15 to the west, you are an hour behind. However, since most countries do not follow longitude lines exactly, each decides which time is convenient for it. For example, China covers nearly 60 degrees of longitude, which is equal to four time zones, yet the country operates on one time - Beijing time.

Amazingly, until the late 19th century, almost every town in the world kept its own time. In the United States, when it was midnight in New York, it was 11.47 in Washington DC. However, the growth of in ternational and national communications made it increasingly important to set a single international time standard.

Finally, in 1884 delegates from 25 countries met in Washington DC for the International Meridian Conference. After a vote, Greenwich in London was chosen as zero degrees longitude, the prime meridian from which all others are measured. From then on, time was measured as Greenwich Mean Time, now also known as Universal Time.

According to the Royal Greenwich Observatory, Greenwich was chosen because the US had already chosen to use Greenwich - the home of the Royal Observatory - as the basis for calculating its own time zones.