Everyone has been taught to never look directly at the Sun since they were very little, but whenever there’s some astronomical event concerning our lovely star, some people throw caution to the wind. With the Mercury transit next Monday, astronomer and TV presenter Mark Thompson decided to show the extreme consequences of looking at the Sun with no filter.
He used a dead pig’s eye and put it in front of the eyepiece of his backyard telescope with a 50x magnification. Within 20 seconds, the light of the Sun burned the cornea and the retina. The demonstration shows how a telescope can act like a magnifying glass on a sunny day. Of course, you shouldn't look at the Sun directly without a telescope, either.
While the pig eye resembles the human eye enough to make this a fair simulation, the rest is obviously an exaggerated scenario. Hopefully, nobody would be foolish enough to look at the Sun through a telescope with no appropriate solar filter to reduce its light, and most definitely not for 20 seconds.
Although in the video the light burns through the cornea and retina, looking at the Sun with your naked eye won't cause the same level of damage. But it will cause chemical changes in your eye known as photochemical damage. The damage is not permanent, but it could take up to over a year for your vision to go back to normal. So, don't do it.
The Royal Astronomical Society’s Mercury Transit website has some information on how to safely observe the event on Monday.