Myth-busting Monday: The Dark Side

Blood moon during lunar eclipse

It’s Myth-Busting Monday again, and this week, we look at a persistent lunar myth, unwittingly perpetuated by one of the biggest bands of the 20th century…

Myth: The moon has a ‘dark side’ which never gets any light from the sun.

Blood moon during lunar eclipse
Image: Pixabay (user: KBOutdoors)

 

Truth: Like the Earth, the Moon is spherical, and is lit by the Sun, which is how we can even see it (moonlight is just sunlight reflecting off the Moon’s surface). The spherical shape means that there is always half of the Moon that is in the light, and half in darkness – just like on Earth. (This is how we get our day and night cycles, and it’s very easy to demonstrate this phenomenon using a lamp and a globe or ball in a darkened room.)

However…like the Earth, the Moon also spins on its axis. This means that all ‘sides’ of the moon (if a roughly spherical object can even have sides) face towards the Sun at some point in its spin, and therefore all areas of the Moon’s surface receive about the same amount of sunlight.

There’s a reasonable explanation for the origin of this myth, though.

The moon is what is known as ‘tidally locked’ with the Earth. The tidal gravitational forces from the Earth have affected the Moon’s rotation, slowing it down so much that it now rotates on its axis in about the same length of time it takes to orbit the Earth. This means that the same side of the moon is always facing toward the Earth, regardless of where it is on its orbit.

(If the Earth and Sun were tidally locked, that would mean that one day would be the same length as one year! You might think the school day seems to last forever now…can you imagine if it actually lasted six months, and was followed by six months of night time?? Let’s be glad that the Earth has managed to continue spinning on its axis thus far.)

So if the same side of the Moon is always facing toward the Earth, that must mean that there’s another side that is always facing away from the Earth, right?

Right! And that’s how this delightful myth was born. Because it had never been seen by Earthlings, the side of the moon facing away from Earth was at some point referred to as the ‘dark side of the moon’, with ‘dark’ in this instance meaning ‘mysterious’ or ‘unknown’. And it was indeed mysterious, up until 1959 when the Soviet spacecraft Luna 3 flew around the unseen side of the Moon and sent back the first pictures.

Unfortunately, ‘the dark side of the Moon’ had entered the general lexicon, and was cemented there in 1973 with the release of the Pink Floyd album of the same name. This led people to conclude (erroneously) that the side of the Moon facing away from the Earth was always in darkness.

And of course, it isn’t! Sometimes, the side facing away is completely lit, and the side facing Earth is completely dark. This is what we know as a ‘new moon’ (when we can’t see the Moon in the sky at all). Conversely, when the side facing us is completely lit, this is a ‘full moon’. If the far side of the Moon was actually in darkness all the time, we would see a full moon every night of the year. (Which would be cool.)

This is a lesson on why it’s always important to use the correct words for things (and possibly also part of the reason that science communication is now its own field of study and expertise). Astronomers prefer the terms ‘near side’ and ‘far side’ of the Moon.

 

For more about the Moon, including some more debunked misconceptions, head to https://moon.nasa.gov/ (link opens in new tab).

To find out more about when the Lunar Eclipse is visible in your area, visit https://www.timeanddate.com/eclipse/lunar/2018-july-27 (link opens in new tab).

Return to Articles homepage

Return to Big Bang Education homepage

 

Sources:

Bad Astronomy – http://www.badastronomy.com/bad/misc/dark_side.html

Lunar 3 Mission – https://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1959-00

Far Side of the Moon (Wikipedia) – https://en.wikipedia.org/wiki/Far_side_of_the_Moon

 

Myth Busting Monday: Goldfish Memory

myth busting Monday - goldfish wearing a mortar board

Happy Myth Busting Monday! Ichthyophiles, it’s your day – today we dispel a tenacious myth about one of your favourite creatures…

Myth: Goldfish have a three-second memory

Truth: Goldfish, and most other fish officially studied, have been shown to have memories extending far past the three-second barrier. Fish intelligence, cognition and sentience has been studied extensively over the years, often using the classical conditioning techniques popularised by the scientist Ivan Pavlov and his many well-trained dogs. In one type of study, fish that were fed at one end of their tank in the morning, and the other end in the evening, started to gather at the correct ends in anticipation of feeding time. This showed that they could make associations between locations, times and rewards.

If you have your own fish, this type of study is very easy to replicate (and please let us know about it if you do!). In fact, in 2008 a 15-year-old student named Rory Stokes decided to debunk the goldfish memory myth for himself. He put a red Lego block into his fish tank each day and sprinkled the food around it. After just three weeks, Rory found that the fish would start to gather around the red Lego block before he had put the food in. He also found that the fish still associated the Lego with being fed even after a week of Lego-free meals.

It’s almost certainly a good thing that fish can remember things for more than three seconds. A memory this short would be of little to no use to a living creature that had to find itself food, avoid predators, and otherwise survive from day to day.

So where did the myth come from? It’s possible that it was invented by purveyors of pet fish, to make everyone feel better about keeping fish in small uninteresting environments. It’s also possible that pet fish’s repetitive behaviours were interpreted as the fish ‘forgetting’ what it had already done, although repetitive behaviour in a captive animal usually indicates that the animal is somehow distressed. So if you do have pet fish, keep their minds active by making sure that their tank is interesting and stimulating – it’s best to consult fish-keeping experts for the best ways to do this!

P.S. If you’re someone who regularly employs the ‘memory like a goldfish’ simile to describe someone’s (or your own) poor memory, might we suggest switching to ‘memory like a sieve’? Sieves have indeed been scientifically proven to let many things through them.

P.P.S. An ichthyophile is one who loves fish. #todayilearned

Follow us on Instagram to keep up to date with Myth Busting Monday and learn more fun facts each week!

Myth Busting Monday: Breathing Trees

It’s Myth Busting Monday time! This is one that has many variations, all with a seed of truth… 

Myth: Plants breathe CO2 during the day, and oxygen during the night

Truth: OK, so this is almost right. Plants do indeed ‘breathe’ or take up carbon dioxide (CO2) when the sun is shining, because they use it to make sugars in a process called photosynthesis (‘oh, I’ve heard of that!’).

Photosynthesis converts sunlight and CO2 into sugars found in plants, and produces oxygen as a by-product. Photosynthesis is ultimately the oxygen and food source of every living being on the planet…but of course, it can only happen while the sun is shining.

Speaking of every living being on the planet, there’s another process that goes on in all their cells – it’s called cellular respiration, and it converts oxygen and sugars into energy that can be used by their cells. Carbon dioxide is a by-product of this process.

Plants are awesome because they do both these processes. During the day while they’re photosynthesising, they don’t need to take up oxygen from the atmosphere because they’re producing so much of it already. But they do need to take up oxygen at night time to complete the cellular respiration process. Luckily for us, they produce about 10 times the amount of oxygen they use themselves.

So trees are pretty great. This magnificent specimen is a Kauri pine, located outside the Cobb & Co Museum in Toowoomba. It was sadly too large to hug properly, but we gave it a nice bark-rub.

Follow us on Instagram to keep up to date with Myth Busting Monday and learn more fun facts each week!

Myth Busting Monday: Cars and Lightning

It’s Myth Busting Monday again! Let’s zap this one once and for all…

Myth: Your car’s tyres will insulate and protect you in the event of a lightning strike.

Truth: Choosing to stay inside your car during a thunderstorm is usually the safest option – this much is true. But the protection the car offers has little to do with the tyres. In fact, it’s the car’s metal body that protects you!

“Huh? But metal conducts electricity…?”

Yep! The car’s protection comes from the fact that it is a hollow ‘cage’ made from an excellent conductor of electricity. Lightning is basically a stream of charged particles looking for the shortest path between a storm cloud and the ground. If its path happens to go via you, this is bad news. It’s generally not advisable to be outside in a thunderstorm, and especially not near something tall like a tree that is likely to attract the lightning (and send it via you).

But if lightning hits the top of a car, it will continue to travel through the metal body of the car AND the tyres (and safely around you) to the ground. This phenomenon was harnessed by Michael Faraday, who discovered that a continuous shield of conductive material would stop an electromagnetic field (including lightning and radio waves). He developed the Faraday cage in 1836 to protect electronic equipment from damage and interference.

Incredibly, a person inside a Faraday cage can even touch the metal on the inside of the cage while lightning is striking, and remain unharmed (NB. DO NOT TRY THIS PLS). This is demonstrated in one of the best science shows we’ve ever seen, at the Museum of Science in Boston, MA, back in 2012. The presenter stands inside the cage, nonchalantly running their hands around the metal bars, while the world’s largest Van der Graaff generator zaps the top of the cage with approx. 15 gazillion volts. 10/10 would recommend.

For more on this topic, check out Richard Hammond putting this theory to the electrifying test on Top Gear: https://youtu.be/ve6XGKZxYxA

Follow us on Instagram to keep up to date with Myth Busting Monday and learn more fun facts each week!

Myth Busting Monday: Daddy Long Legs

One of our favourite things we get to do as science teachers is debunk scientific misconceptions and myths! So we hereby present to you… Myth Busting Monday! We kick off with an old, old chestnut about our spindly little friend, the Daddy Long Legs spider.

Myth: they’re actually super venomous, but luckily for us, their tiny fangs can’t penetrate our tough skin!

Truth: it’s true that Daddy Long Legs do have venom, and teeny tiny fangs (just 0.25mm). But compared with other spiders, their venom is not very potent at all. Despite this, the DLL does prey on other such famous eight-legged assassins as the Red-back Spider – usually by trapping them with strands of silk, rather than by envenomating them – but this may have caused people to misinterpret the strength of the DLL’s venom, hence the myth.

Also, in 2004 one of the actual TV Myth Busters stuck his hand in a tank of DLLs (shudder…they’re still spiders) and found that their tiny fangs actually could puncture his skin! He reported feeling a tingling sensation which soon wore off (hint: that was the venom). There are also many other anecdotal reports of DLLs biting humans, none of which led to a fatality.

Myth: Busted! 📷: Olaf Leillinger – Pholcus phalangioides (seriously though, how fun are scientific names?)

Follow us on Instagram to keep up to date with Myth Busting Monday and learn more fun facts each week!