ABOUT SCIENCE - SOME QUESTIONS AND ANSWERS

1. Why is air invisible?

Air is made up mostly of nitrogen and oxygen molecules that are spread too thinly to affect light noticeably by, say, altering its colour or intensity. Even so, air’s presence is revealed in hot weather through the shimmering effect called ‘heat haze’. This is the result of the heat causing fluctuations in the density of the air, which in turn affects its optical properties.

2. Why do oysters make pearls?

It’s an immune response designed to protect the oyster from a parasite or an injury (not just a grain of sand as is commonly believed). Cells from the mantle of the oyster form a pearl sac around the irritation. The pearl sac then secretes calcium carbonate and conchiolin protein that builds up in layers to form an impermeable barrier.

3. Can you melt wood?

No. Wood is mostly cellulose, lignin and water. If you heat wood, the water boils away first and then the lignin and cellulose (both long-chain organic molecules) will react with oxygen and burn. Even in a vacuum, these molecular chains are too long and tangled to wiggle free into the liquid phase before they reach temperatures high enough to break their bonds. Instead they break down into smaller substances, like methane and organic compounds containing carbon and hydrogen.

4. Do heat patches really help with muscle pain?

Although heat should not be used for a fresh injury, it can certainly be beneficial for longterm conditions. Heat patches dilate blood vessels, promoting blood flow and helping to relax painful muscles. Tissue injury activates nerve endings in the skin called nociceptors, which transmit signals to the brain to inform it of pain. At the same time, neurotransmitters initiate a reflex that causes muscles to contract at the injury site, often to the point of spasm.

Fortunately, heat can activate temperature-sensitive thermoreceptors, which initiate nerve signals to block those from nociceptors. Applying pressure also helps, by triggering nerve endings called proprioceptors. Activating the sets of receptors helps painful muscles to relax.

5. Is it possible to sleep with your eyes open?

Not normally, but there is a condition called nocturnal lagophthalmos where a sufferer is unable to shut their eyelids when asleep. According to one review, this occurs in up to 5 per cent of adults. This can be due to a variety of factors, including protruding eyes or abnormalities of the eyelids.

There are also cases in which the cause has not been established. Noctural lagophthalmos can lead to certain difficulties, from sore eyes to more severe problems such as the development of ulcers on the cornea. Do talk to your doctor if you are waking up with red or sore eyes or have been told by someone that you sleep with your eyes open.

6. Where does the nitrogen in the air come from?

Nitrogen makes up 78 per cent of the air we breathe, and it’s thought that most of it was initially trapped in the chunks of primordial rubble that formed the Earth. When they smashed together, they coalesced and their nitrogen content has been seeping out along the molten cracks in the planet’s crust ever since. Nitrogen can only be used by living organisms after it has been ‘fixed’ into more reactive compounds such as ammonia or oxides of nitrogen. Nitrogen fixation is carried out by bacteria, algae and human activity, and once organisms have benefited from it, some of the nitrogen compounds break down and go back into the atmosphere as nitrogen gas. Along with top-ups from volcanic eruptions, the ‘nitrogen cycle’ has kept the level pretty constant for at least 100 million years.

7. How large a telescope was needed to image an exoplanet?

The first-ever image of a planet beyond the Solar System was taken in 2005 by astronomers using the European Southern Observatory’s Very Large Telescope (VLT) in Chile. Known as 2M1207b, the planet is about 1.5 times bigger than Jupiter and around 170 light-years away. It was detected using one of the VLT’s four gigantic telescopes, whose light-gathering mirrors are an impressive 8.2 metres across.

8. Why do we get dizzy when we spin?

When you move your head, the acceleration is detected by hairs lining the acceleration is detect by hairs lining the side of fluid-filled tubes in your inner ear. If you spin for long enough, the brain gets desensitised to the constant turn signals from your ear, and adjusts to zero them out. When you stop, the ears correctly report zero turning, but your brain is still actively cancelling this out and so it thinks you are now spinning in the opposite direction.

9. Is it possible for chickens to lay eggs in space?

Only one bird has ever actually laid an egg in space. A quail aboard the Russian Soyuz TM-10 spacecraft laid an egg while travelling to the Mir space station in 1990. It seems likely that other birds would be able to physically lay eggs in zero-g, but successfully incubating those eggs is much harder. Experiments with both quail and chicken eggs in space show much higher rates of birth defects in the bird embryos.

10. Are there any studies on the best over-the-counter painkillers?

Experience of pain is highly subjective so it is difficult to say which are the best painkillers. Studies tend to focus on particular aches and pains. For example, an analysis by 'The Lancet' of thousands of trials suggested that paracetamol doesn’t touch pain from osteoarthritis but a max dose of a non-steroidal anti-inflammatory (NSAID) called diclofenac does the job. NSAIDs such as ibuprofen reduce inflammation and are best suited to muscular pain relief. The drugs block enzymes that produce hormone-like chemicals called prostaglandins, which promote inflammation, pain and fever. Meanwhile, paracetamol is most suited to headaches and reducing a high temperature.

11. How does trophy hunting affect wild animal populations?

Since the days of the Roman Empire, wild animals have been slaughtered to prove power and wealth. Bigger is better when it comes to this ‘sport’, which means that dominant, mature male rhinos, elephants, lions, leopards and other animals are the prime targets of hunters. The artificially premature loss of strong, healthy individuals takes vital genes out of the breeding pool which, over time, can result in an overall decline in body size and, where applicable, also horn or tusk size. Removing these frontline animals also undermines social cohesion and can leave members of prides and herds vulnerable to attack by other members of their own species. Although some argue that money from trophy hunting can help with conservation, there is not enough evidence to convince us that it can.

12. How thick is the thickest fog?

By definition, fog has a visibility of less than 1km, but it can get much thicker than that. The Met Office visibility scale runs down to a Category X fog, where visibility is less than 20m. If fog gets mixed with industrial pollution, it becomes smog and can be thicker still. During the Great Smog of 1952, drivers couldn’t see their own headlights!

13. By weight, which animal has the largest baby relative to body size?

Despite a kiwi being about the size of a chicken, the female lays an egg that is about half her weight! It’s so big because it has an enormous yolk, which sustains the chick for the first week of its life. Here you can see some other animals that have enormous babies, as well as those that have teeny tiny offspring (with humans thrown in for good measure)

Kiwi (egg)(1/2), Giraffe (1/10), Beluga whale (1/17), Human (1/22), Giant clam (1/500,000,000), Ocean sunfish (1/1,500,000), Red kangaroo (1/100,000), Honey possum (1/2,400). 

In "BBC Focus" UK, issue 318, February, 2018,excerpts pp. 81-86. Digitized, compiled, adapted and illustrated to be posted by Leopoldo Costa.