Set lasers to infinity!
QUESTION If a laser is fired vertically upwards, will it eventually disappear as it loses energy? Laser energy is a form of electromagnetic energy and so falls into the same category as radio waves and visible light. In accordance with the first Law of Thermodynamics, energy can neither be created nor destroyed and can only be converted from one form to another.
In the case of lasers, the energy is usually converted from light to heat, which dissipates into whatever medium it passes through.
electromagnetic energy follows an inverse square law. so each time the distance travelled is doubled, the energy content is halved, the other half being converted to another form of energy.
as an example, the output of a 100 kw radio transmitter will be 50 kw at one metre from its source, 25 kw at two metres from its source, 12.5 kw at four metres, 6.25 kw at eight metres etc.
as fans of shortwave radio can tell you, it is possible to send a radio signal around the world with radio transmitters of much lower power output than 100kw.
Using the inverse square law, it is apparent that the laser energy will continue to travel for an infinite distance, but at a certain point its remaining energy will be too small to measure using conventional equipment.
The actual distance at which this happens is determined by the output power of the laser transmitter and the sensitivity of the measuring equipment.
However, if you had equipment sensitive enough, it would still be possible to detect the laser’s light even at the other end of the universe.
Bob Dillon, Edinburgh. QUESTION When was autism identified? Are any well-known historical figures now thought to have suffered from the condition? HIgH- FUncTIonIng autism was officially identified in 1954. Many of the conditions on the autistic spectrum, such as asperger’s syndrome (from which I suffer very mildly), were officially recognised in 1990.
The condition was discovered by austrian doctor Hans asperger, and is more common in males, although more women are now being diagnosed with it.
If you consider that attention Deficit Hyperactivity Disorder (aDHD) and Fragile X syndrome are also on the spectrum, you will see it covers a wide range of conditions, which can be mild or severe depending on the sufferer.
Historical and famous people thought to have had autism in one form or another include albert einstein, Hans christian andersen and the artist Wassily Kandinsky. a more recent example is President Putin, who is believed to have asperger’s syndrome. The national autistic society, among other charities, offers invaluable advice. Mrs Frances-Mary Pratt,
Carterton, Oxon. Andy Warhol’s repeated images of campbell’s soup tins, elvis Presley and Marilyn Monroe are considered to be the artist’s ironic response to consumerism and popular culture, but it has been suggested that many of his artistic and behavioural traits bear marks of autism.
His social ineptitude, care to use the minimum of words in speech, difficulty recognising friends and obsession with the uniformity of consumer goods are each thought to be clues that to some degree he was autistic.
clinical psychologist Dr Judith gould, former director and current lead consultant at the Lorna Wing centre for autism, in Kent, said: ‘From the study I have seen, Warhol almost certainly had asperger’s syndrome.’
Wolfgang amadeus Mozart is thought by some to have been on the autistic spectrum. eyewitness accounts recall his grimaces and outbursts as well as a short attention span akin to ADHD, perhaps responsible for his prolific output.
The brilliant scientist nikola Tesla had an intense sensitivity to light and sound, a range of phobias, a tendency to be reclusive and an obsession with the number three. sadly, this left him at a great disadvantage to his rival Thomas edison who pinched many of his ideas.
sadly, Tesla wasn’t recognised for his genius during his lifetime and died alone, penniless and shunned by the scientific community.
James Gould, Reading, Berks.
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