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11 things you may not know about solar eclipses

A total eclipse of the sun is one of nature’s most stunning phenomena. This strange spectacle happens when the moon passes precisely in front of the sun, blocking its light. The Dark Side of the Sun has been exploring the mythology and psychology behind this odd astronomical event.

1. The US eclipse on 21 August looks set to be the most-watched solar event in human history

The first total solar eclipse to be seen in the States for 99 years, it will be viewable across a swathe of the country 70 kilometres wide. Stretching across 14 states, from Oregon in the northwest to South Carolina in the east, the rare event will attract eclipse enthusiasts from all over the world.

The moon is both 400 times smaller in diameter than the sun, and 400 times closer to the Earth, so precisely the right size to block out the sun.

2. Solar eclipses happen because of a unique cosmic coincidence

In an odd twist of celestial fluke, the moon is both 400 times smaller in diameter than the sun, and 400 times closer to the Earth. This means that from our vantage point it’s precisely the right size to block out the sun. But this won’t be the case forever: the moon is very slowly moving away from the Earth, so at some point in the far future it will appear too small to completely cover the sun.

3. The time during which the sun is completely covered by the moon is known as ‘totality’

During these few minutes, the whole sky darkens to a deep blue or purple colour so that brighter stars can be seen, and an orange glow appears around the horizon. Although the sun is completely blocked out, its atmosphere is illuminated, creating a glowing ‘corona’ around the edges of the darkened moon. The sun’s light is so bright that, even during totality, it should be viewed through special protective glasses to avoid eye damage.

4. In the corona, you can see shapes that aren’t usually visible in the gases surrounding the sun

Stunning phenomena such as polar rays, helmet streamers and coronal mass ejections can be seen within the sun’s atmosphere. The gases that form these shapes are burning at over one million degrees Celsius. Their movements follow an 11-year cycle and are shaped by magnetic fields and solar winds.

5. People often experience total solar eclipses as profound, life-changing events

Dr Kate Russo, a psychologist studying what happens to people watching an eclipse, describes a kind of euphoria caused by the release of dopamine in the brain. Witnesses can also experience an impending sense of doom and fear that triggers a primal fight or flight response. Afterwards, they may struggle to describe what they have experienced, in a way that’s strangely similar to people who have been through trauma.

6. ‘Umbraphiles’ travel thousands of miles to witness eclipses

Eclipse-chasers or ‘umbraphiles’ are so devoted to the phenomenon that they travel the world to see as many as possible. David Makepeace, also known as 'eclipse guy', has witnessed 20 solar eclipses in 13 countries across 7 continents. The name ‘umbraphile’ comes from the Latin word for shadow, referring to the darkness cast on the Earth during an eclipse.

What happens during a solar eclipse?

Physicist Dr Frank Close explains how the movement of astronomical bodies makes them occur.

7. Animals often appear confused, or behave oddly during eclipses

People have reported seeing cows lying down or returning to their barn, dogs barking, crickets chirping, giraffes running around, spiders dismantling their webs and even whales rising to the surface of the sea.

During an eclipse people have reported seeing cows lying down, giraffes running around and spiders dismantling their webs.

8. Birds behave as if night is falling before an eclipse, and as if they’re greeting a new day afterwards

Eclipse chaser Dave Balch describes how during the 1991 solar eclipse in Hawaii, nearby birds became increasingly noisy as the eclipse approached, fell totally silent while it was happening, and then grew loud again as the sun re-emerged. Somewhat more dramatically, astronomer Christoph Clavious claimed that during the 1560 eclipse in Portugal, “the birds fell down from the sky to the ground in terror of such horrid darkness”.

9. The Vikings thought an eclipse was a pair of wolves chasing the sun

Other ancient cultures believed it was the sun or moon being consumed by a creature: Vietnamese people traditionally thought this was a frog or a toad, while early Chinese mythology held that it was a dragon. In fact, the earliest term for eclipse in Chinese – ‘shih’ – meant ‘to eat’.

10. Eclipses have inspired terror and violence, as well as reflection and reconciliation

For many ancient civilizations solar eclipses were a portent of doom, so people would try to chase them away by brandishing weapons and banging drums. The Aztecs are even reported to have carried out human sacrifices. By contrast, for some cultures in Asia, a solar eclipse historically represented a time for calm and reflection. In ancient Africa, the Batammaliba people believed it meant the gods were fighting, and therefore communities should come together and resolve old feuds to encourage peace.

11. Christopher Columbus used a lunar eclipse to save his crew from hunger

In 1504, Christopher Columbus and his crew were stranded on the coast of Jamaica. But their poor behaviour angered local people so much that they had stopped supplying the crew with food. Aware a lunar eclipse was imminent, Columbus threatened to turn the moon blood red if the locals didn’t resupply his ships. When the eclipse occurred as predicted, the frightened community quickly agreed to his request.

Satellite photo of a total solar eclipse in the Sahara desert