Science: Technoquest

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Q How big is our galaxy?

Our galaxy is about 50 kilo parsecs. A parsec is 3.26 light-years and a light-year is the distance light travels in one year. So that makes the galaxy about 1,500 million billion kilometres across.

Q What is a blue moon, and how often does it occur?

There are two definitions of a blue moon. The first is a phen-omenon caused by particulate matter (ash and dust) that is ejected by volcanic eruptions into the upper atmosphere. When light that is reflected from the Moon passes through the atmosphere, it interacts with the volcanic materials, resulting in a blue casting as seen from the ground.

A second definition of a blue moon is when two full moons occur in the same month. The last blue moons were on 2 and 31 January. So it is not as uncommon as people think - the phrase "Once in a blue moon" is misleading. In fact, a blue moon happens about once every 2.72 years.

Q What is the source and nature of the radiation from mobile telephones, and is it present in landline and cordless phones?

Mobile telephones produce electromagnetic radiation in the radio region. These radio waves are produced during a phone call, whenever text messages are sent and received, and also when the phone is moved from one area of the country to another. In fact, whenever the phone receives information or transmits it to a nearby "base station".

Digital phones radiate a series of pulses, whereas analogue phones produce a continuous signal. Modern mobile phones are usually digital. Cordless phones radiate, but they are only sending information for shorter distances. Landline phones could also radiate, but this would only be through the wires that connect them. In fact, every electronic item has the potential to emit this type of radiation.

Q How high does does a grasshopper jump?

The largest known grasshopper in the world is an unidentified species from the border of Malaysia and Thailand, measuring 25.4cm in length. It is capable of leaping 4.6m. To jump as high as possible, the grasshopper makes its body streamlined. The wings remain closed, and the legs straighten and tuck under the body. Although small, the grasshopper's leg muscles are hundreds of times more powerful than an equal weight of human muscle.

Q Oriental babies supposedly have blue/ black marks on the base of the spine when they are born. Is this true? If so, why is it there?

These are called Mongolian spots and occur on many dark- skinned babies. They are nothing more than dense collections of melanocytes, the skin cells that contain melanin, the normal pigment of the skin. When the melanocytes are close to the surface, they look deep brown. The deeper they are in the skin, the more bluish they look. Either way, they are not related to bruises or any other medical condition. They do not predispose to skin cancer or any other problem.

Many Mongolian spots have faded (at least somewhat) by the age of two, and most have completely disappeared by the age of five. If the spots remain at puberty, they are likely to be permanent. Fewer than 5 per cent of children with Mongolian spots still have any by adulthood. Those who do tend to be the ones with multiple, widespread spots, or with spots in unusual locations.

Further information: http://www.sciencenet.org.uk. Or ask your own questions on Science Line, Freephone: 0808 800 4000, or via e-mail to sci.net@campus.bt.com

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