No, It Won’t Explode And Kill Us: Five Myths About The Sun, Debunked

Our friends at Queensland Health want to make sure you’re always sun safe, so we put on our skepticism sunnies and looked directly into it to bust some of the biggest myths about the giant ball of fire.

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The sun is the source of tremendous amounts of heat and light generated by nuclear fusion. It is also the reason life on earth is at all possible. It’s pretty great. It’s no wonder, then, that it has played a key role in a number of myths throughout human history – from the ancient Egyptian sun-god Ra, to melting the wings off Icarus, to the Indigenous Australian sun-goddess Wuriunpranilli.

Unfortunately, the sun has attracted its fair share of the other kind of myth: misconceptions, urban legends, and damaging falsehoods. Some of these are pretty innocuous, but others can cause real damage. So to celebrate sunny days in the spirit of healthy scepticism, we’ve taken the liberty of debunking them for you.

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Myth #1: Summer Occurs When The Earth Is Closer To The Sun

The earth orbits the sun in a near-perfect – but not quite perfect – circle. The earth’s orbit is technically elliptical, which means that at times it’s closer to the sun than at other times. At aphelion (the closest), the earth is around 147,000,000 kilometres from the sun, and at perihelion (the furthest), that distance swells out around five million kilometres to land at approximately 152,000,000 kilometres.

Five million kilometres is a long distance, to be fair, and people assume that this yearly variation in distance causes the changing seasons. But: as anyone who has sweltered through a hot Australian Christmas should know, whenever it’s winter in the northern hemisphere, it’s summer in the southern, and vice versa. If the distance theory of the seasons were correct, it would be summer everywhere at the same time.

The reason we have seasons has nothing to do with the distance of the earth from the sun and everything to do with the world’s axial tilt of 23.5 degrees. As the earth orbits the sun, this axial tilt slowly moves the earth so that first one hemisphere and then the other receives more sunlight, which in turn generates the four seasons.

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Myth #2: Australia Has A Huge Vitamin D Deficiency Problem

You might have heard this one from a well-meaning friend or relative. The argument goes something like this: Australians are now so aware from years of slip-slop-slap and skin cancer public awareness campaigns that we’re now risking vitamin D deficiency. Vitamin D is one of the vitamins that humans need to live, and although it can be found in some foods (including salmon, orange juice, and milk), it is mainly synthesised in our own bodies by the action of sunlight on skin. And since vitamin D deficiencies have been linked with some pretty nasty diseases — including bowel and breast cancers and osteoporosis — it’s tempting to think that you should forgo sun safety every now and then in order to boost your vitamin D levels.

Australians are clearly worried about vitamin D deficiency – blood tests for vitamin D levels are the fastest-growing Medicare item in the country, costing taxpayers over $140 million in 2012 compared with a measly $1.02 million in 2000. The problem is that, as a meta-analysis published in Australian Family Physician demonstrates, there’s very little consensus about how little vitamin D you actually need to have to be truly deficient — and some evidence to suggest that having too much vitamin D could also be harmful.

What we know with much more certainty is that skin cancer is a killer – around 2000 Australians die from it every year.

Unless you are one of the few Australians with truly low levels of vitamin D, you should be getting enough from your diet and your everyday exposure to sun. (If you are worried about your vitamin D levels, see your GP – they’ll be able to determine whether you need testing or vitamin D supplementation.) The Cancer Council also have this handy map that shows you how much sun exposure you need each day depending on where in Australia you live.

There’s also evidence to suggest that sunscreen won’t block vitamin D synthesis — so you don’t need to stray from recommended sun safety precaution: wearing a hat and SPF 30+,  covering up, and limiting your exposure, particularly during peak UV periods.

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Myth 3: Auroras Are The Solar Wind Crashing Into The Earth’s Atmosphere

This one is vaguely true – but, like the myths above, the devil is in the details.

Auroras are the famous ‘northern lights’ that most of us are familiar with from desktop backgrounds and nature photography websites rather than firsthand experience. They’re caused by the ‘solar wind’ – a stream of energised plasma that the sun constantly ejects in all directions as a byproduct of all of that nuclear fusion it does. Because the sun itself is not a perfect system, the amount of solar wind it generates varies, which in turn creates ‘space weather’. During periods of heightened space weather activity, auroras appear.

Is this the solar wind hitting earth? Sort of, but not quite. What happens instead is that electrons from the solar wind are sucked in to the atmosphere by earth’s magnetic field, then hit atoms in the earth’s atmosphere, which energises them – and the energy is released as light. What we see is matter from earth being excited by forces from the sun that have been pulled in by the earth.

People often assume that auroras can best be seen at the poles and should be seen in winter, but this isn’t quite true either. Auroras appear in what scientists call the ‘auroral zone’ – a region of sky around 2500km around each of the earth’s geomagnetic (rather than geographic) poles. The northern auroral zone includes large swathes of Canada, Alaska, and the northernmost parts of Russia, Finland, Norway and Iceland. The southern auroral zone is tricker to get to – most of it lies above the ocean surrounding Antarctica. Within that space is an ever-changing ‘auroral oval’, which is where auroras are most likely to appear; you can find a daily map of it on Spaceweather.com.

Don’t assume that winter is the best time to see auroras, though: the nights might be long and dark, but winter also means a high probability of cloud cover to ruin the view. If you really want to see auroras, the best spot is looking down from aboard the International Space Station – and if you’ve flunked out of astronaut school, you can always watch video footage captured by the ISS crew instead.

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Myth #4: You’re Safer From The Sun On Overcast Days 

This one makes intuitive sense. Getting too much sun causes skin damage, which in turn generates a risk of developing skin cancers. But if the sky is overcast and you can barely see the sun, there should be nothing to worry about, right?

Nope.

It’s not actually sunlight that causes sunburn and skin damage – it’s ultraviolet or UV radiation, which is invisible to the naked eye. The sun emits huge amounts of UV radiation as it goes about its business of nuclear fusion, some of which hits earth’s atmosphere. UV radiation comes in three flavours, each more damaging to human skin than the last: UVA, UVB, and UVC. All UVC and most UVB that reaches earth is absorbed by the ozone layer, but it’s the UVB that remains that directly causes skin cancers.

Here’s where it gets a bit tricky: thick clouds can absorb much of the UV radiation that comes down to earth, but thin clouds simply let it pass through. And cloud cover can actually concentrate UV on the earth’s surface by reflecting and focusing it towards one spot, like a mirror.

There’s an easy solution to the problem, though. The Australian Radiation Protection and Nuclear Safety Agency – ARPANSA – keeps a network of UV detectors in cities around Australia and can tell you in real time what the current UV level is in your region. You can also download several apps for your smartphone that can give you realtime information about the UV level in your area, such as the free Sunsmart app. If the UV index is three or higher (or you can’t find the information for your area), you need to look after yourself — no matter what the weather looks like outside.

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Myth #5: The Sun Will Explode And Kill Us All

Humans in general are terrified of what lies out there in space, just waiting to pounce on our fragile planet and wipe out human civilisation. It could be alien life forms that want to incubate their offspring in us or strip-mine our planet for resources, leaving it a lifeless and barren husk. Or maybe the earth will be hit by a passing asteroid, or smash into a giant wandering planet? These are all scenarios familiar from movies, but conspiracy theorists – particularly those who were sure that the apocalypse would arrive in 2012 – have latched onto the idea that the sun itself will be the author of our end by sending out a huge coronal mass ejection (CME) in earth’s direction.

Let’s go back to the ‘space weather’ analogy. If we understand that solar wind fluctuates in strength depending on the activity of the sun, CMEs are the space weather versions of a hurricane or superstorm: a huge blast of supercharged energy that races off from the sun and traverses the distance to earth in about one day. And the sun is pretty good at sending these things out in all directions: at its most active, it can send out up to five CMEs per day, while at its least active it still averages one per day. When those CMEs hit earth, a huge amount of energy is sucked into the earth’s atmosphere by the earth’s magnetic field – which protects the earth from the force of the solar wind. But things like GPS systems and electricity transformers can be damaged by all that extra energy — in Malmö, Sweden, in 2003, when a small solar storm triggered blackouts.

Conspiracy theorists love to point to the ‘Carrington Event’ of 1859 as an example of the havoc that a CME could inflict on the world in future. The Carrington Event was the most powerful CME yet witnessed, and it played havoc with compasses, and the telegraph system of the time. Beautiful auroras could be seen well beyond the aurora zone. What would happen if a Carrington Event–scale CME hit earth now?

Well, we’d know about it in advance, for starters: the sun is being constantly monitored by a fleet of satellites in orbit around earth, and they can detect space weather events in advance. We already take precautions during periods of heightened space weather: for example, planes must be re-routed away from the polar regions during these events as they can interfere with radio communication. In the case of extreme space weather, there would undoubtedly be some severe impacts on electronic systems in some parts of the earth, but the overall likelihood of this kind of event wiping out civilisation is very low. So we’ll be fine.

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Chad Parkhill is a Melbourne-based writer and editor.