A total solar eclipse is due to darken skies over the United States on August 21, and people all across America will be lining up to see it.
But while it’s set to be a fantastic spectacle, don’t be tempted to look directly at the sun, because doing so could actually cause your eyes to poison themselves.
When too much UV light hits your eye, it can have lots of harmful effects, such as heat damage, cancerous mutations and cataracts.
But a less well-known effect is the release of chemicals called inside the retina at the back of your eye. These free radicals act like a poison, preventing the cells from metabolising and causing long-term damage to the retina.
Free radicals can attack and destroy the membranes inside the cell, impairing its functions and, “in extreme cases lead to cell death”, B. Ralph Chou, a professor of optometry at the University of Waterloo in Ontario, told the Daily Mirror.
The amount of damage from sunlight (known as solar retinopathy) depends on lots of factors, such as the type of light that enters your eye, the amount of time you spend looking at it, and the intensity.
Scientists are not clear on how big a problem this is but there are hundreds of reported cases of eye damage caused by eclipses.
Legend has it that when astronomer Galileo Galilee made his own telescope, he looked directly at the sun and blinded himself. Although this is actually an urban myth, other notable scientists, including Isaac Newton also reported eye damage from direct sunlight.
While looking at the eclipse is very unlikely to cause total blindness, it can certainly cause permanent vision problems.
How to watch the solar eclipse safely
If you’re planning to watch the solar eclipse, make sure you take one of these safety precautions:
- Eclipse glasses
Good solar eclipse glasses filter out all of the harmful light. Lots of companies sell solar eclipse glasses, but you need to make sure they are CE-approved, meaning they conform with European health, safety, and environmental protection standards.
If you can’t afford CE-approved glasses, don’t rely on regular sunglasses – they won’t protect you. Instead it’s worth looking at other techniques…
2. A pinhole projector
Use a pin to create a small hole in the centre of a piece of card. With your back to the eclipse, hold the card up so it gets the full force of the eclipse.
Take a SECOND PIECE of card and hold it in front of you like a screen. The eclipse itself will be projected through the pinhole and onto the screen. The image will be inverted, but it will also be safe to look at.
3. A handheld mirror
Cover a small mirror with a piece of paper or card with a hole in it (smaller than 5mm). Angle the mirror to catch the sun, it will project a pinhole image of the eclipse onto the far wall.
4. Use a colander
Empty the pasta out first. This works in exactly the same way as the first sheet of card in the example above. The holes in the colander will project several images of the eclipse onto a piece of white card or paper held in front of you.
Make sure to stand with your back to the sun and hold the colander above your shoulder or next to your head.
5. A bucket of water
If you’re really low-tech, simply fill a bucket with water and look at the reflection.