10 More Quickfire Science Questions

Hello and welcome to a new instalment of quickfire science questions you may have asked yourself, each answered in 150 words or fewer. Many of them seem to be food-based this time around so I guess I’m finding food particularly interesting at the moment. So interesting in fact that I find myself eating it every day! Click any images to be taken to the original source.

The first 10 questions can be found right here and include: Why do men have nipples? What colour is a mirror? Why do spiders’ legs curl up when they die? And many more. 


1) Why does orange juice taste horrendous after brushing teeth?

Ben Jerry toothpaste OJ icecream
source: duckduckgrayduck.com

It’s probably nothing do with the minty flavour. Like many cleaning products, toothpaste contains a detergent called SLS or sodium lauryl sulphate. This helps spread the toothpaste around your mouth and creates a frothy foam which people generally associate with cleanliness – same with shampoo and washing up liquid.

SLS happens to bind to the parts of your tongue which detect sugars, making you temporarily unable to taste sweetness. Orange juice is packed full of sugar (as much per glass as Coca Cola) which masks the taste of various other substances that you wouldn’t normally perceive. Take the sweetness away and all the sour and bitter flavours you weren’t expecting reveal themselves. 


2) Why does insulin need to be injected if the contraceptive pill can be taken orally?

These treatments both involve hormones – substances which relay messages around the body. Type I diabetics use insulin to help maintain normal blood sugar levels as they cannot produce it for themselves. The contraceptive pill contains variants of oestrogen and progesterone which essentially trick the body into thinking it’s already pregnant and therefore not receptive to further attempts at making it pregnant again!

The difference is this: insulin is a protein hormone and will get broken up by protein-digesting enzymes as soon as it reaches the stomach. Injection directly into the bloodstream simply bypasses the gut. The hormones in the contraceptive pill are steroid-based and aren’t destroyed by digestive enzymes, so they pass safely through the wall of the small intestine to be delivered to the relevant organs.


3) Is there a reason for runts?

The runt on the left died days after this was taken. Source: montana osprey cams
The runt on the left died days after this was taken. Source: montana osprey cams

Siblings can be pretty horrible to one another, but some animals have it far worse than arguments and practical jokes. Many bird species lay one more egg per clutch than they can normally raise. This “bonus” child usually hatches later and is therefore smaller than its siblings. During years of bumper food, there’s plenty to go round for the runt. If it survives to adulthood and reproduces for itself, the runt’s parents will have done better genetically than those who did not lay an extra egg.

In years where food is scarcer, it’s better to have fewer healthy offspring than more sickly hungry ones. Here, the runt serves as a kind of genetic sacrifice or deliberate weak link. It is fed less often by its parents and harassed by its siblings so harshly that it eventually gives up the struggle and dies. Seems cruel, but it makes evolutionary sense.


4) I went for a long run today but my legs only started aching today. Why?

You’re experiencing a classic case of DOMS, short for Delayed Onset Muscle Soreness. This dull ache shouldn’t actually be painful, and it’s a sign of a good workout on muscles which haven’t been properly used for a while. When you exercise hard, extensive and repeated stretching creates “microtraumas” in the muscle fibres. Sounds nasty, but this process is vital to becoming stronger. Your body takes these tiny tears as a signal to put grow the muscles back stronger so you can perform better in case you decide to try the same activity again.

There’s no proven effective treatment for DOMS, but the ache will fade in a couple of days unless you’ve done something nasty to yourself. The next time you go for a run (assuming you don’t wait months!) you should experience far less DOMS as your new-and-improved muscles are ready to take on the challenge again.


5) What are freckles?

frecklesThe brown colour of skin in freckles, moles, tan and naturally dark skin is all caused by the same pigment molecule – melanin. Melanin protects us from the UV light from the sun and is produced by specialised skin cells called melanocytes. People prone to freckling (such as myself) have a naturally uneven distribution of melanin across the face and body.

When we go out in the sun, our melanocytes kick into action and produce more melanin, especially in areas like the nose, cheeks and arms. Hence more freckles. Some freckles fade with time (you could almost use my face as a calendar with the regularity mine fade after summer) but others stay for life.  While people of any ethnicity can have freckles, visible or not, there is a genetic component and twins often have startlingly similar freckle levels.


6) What are (skin) moles?

Melanocyte cells are also the “culprit” behind these brown dots, but for different reasons. Most moles develop after birth but within the first 20-30 years of life. These moles are actually a sort of failed cancer – the excessive spread of the melanocytes mentioned above. The body has mechanisms in place to stop the growing cells getting out of control, but it can’t get rid of the cells and pigment completely so the brown colour remains.

Most people have around 10-40 moles and these are almost always completely benign. Occasionally they can turn rather nasty and revert back into a growth state. This is how skin cancer (melanoma) can occur. So always watch out for changes in appearance and feel of your moles, and go to a doctor if you’re unsure. 


7) What makes games like Candy Crush and World of Warcraft so addictive?

Source: Samson Yee/Quora
Source: Samson Yee/Quora

These games may look nothing alike, but they work on your brain in much the same way. Both of these games promote addictive behaviour by employing a range of psychological tricks that keep players thinking “just one more”.  

One such strategy is frequently bestowing small rewards with random elements to them. The rewards trigger a surge of dopamine in the brain, a pleasurable but unsatisfying feeling that makes you want another. The random element is particularly important – we are more likely to get hooked on an activity if the prizes come at unpredictable times than if we know exactly when the reward is incoming. Illogical but true, as casinos well know.  

Add in social elements, attractive graphics, genre preferences, escapism, skill (in some cases) and the joy of seeing numbers accumulate feelings of earning rewards and the dopamine surges just keep on coming.    


8) What causes the grey-green coating around some hard boiled egg yolks?

When whole eggs are cooked at high temperatures for extended periods of time, the sulphur in the white reacts with the iron in the yolk. The result is a ferrous sulphide halo around the yolk. This ring is completely harmless but it is a sign that the chef over-did them and may accompany a rubbery white and a pale pithy yolk. The eggs with these coatings are also usually the smelliest, thanks to the treatment of the sulphur.

For not-so-stinky eggs with a bright, creamier yolk:  Put eggs in cold water, turn the heat up high, bring to a rolling boil (harsh bubbling) and time for one minute. Take off the heat and leave in the water until it cools. Enjoy, and you’re welcome.


9) Does celery burn more calories than it contains?

source: wikimedia commons
source: wikimedia commons

Nope, there’s no such thing as a zero-Calorie food. All foods take energy to digest and metabolise but the body is so efficient that the overall caloric value remains positive. In the case of celery, only 0.5 of the 6 Calories in a stick are used for digestion. Proteins are more costly, requiring 20-30% of Calories for digestion.

A sneaky exception is ice-water. Water contains no calories but the body spends a little energy to raise it to body temperature. One glass of ice water technically contains -17.5 Calories.

In the USA, companies can advertise foods as “zero calories” even when they aren’t, so long as they contain fewer than 5 calories per specified serving. The sweetener Splenda (3.4 Calories per packet), and I Can’t Believe It’s Not Butter’s spray (9000 calories per bottle) use this to their advantage, so watch out.


10) Why shouldn’t you put tin foil in the microwave?

Microwaves are actually remarkably simple devices. They emit light radiation at very specific wavelengths which we cannot see but are absorbed by water, fats and sugars. This gives them excess energy which converted to physical vibration – also known as getting hot.

Metals and many other substances don’t absorb the microwaves in quite the same way. However microwave radiation can cause currents to flow through certain pieces of thin metal such as tin foil. When the foil contains sharp edges and corners (which is almost always), the electricity can jump off as sparks as it ionises the air around it.

So far so dangerous, but if there happens to be some sort of paper or oil in the microwave as well, the sparks can ignite the readily flammable material. So unless uncontrolled sparks and flames are your thing, don’t try this at home. Watch these guys try instead!


Any suggestions / clarification / corrections? Let me know in the comments or email  eccoyte@gmail.com, I’d love to hear from you.


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