A very rare occurrence is happening Aug 21, 2017. The solar eclipse. There are areas that will have totality and others that will have a small crescent. This is such a phenomenal occurrence that it may only happen once in a lifetime. However, we have to know what we are doing in order to appreciate it safely.
The damage done from looking at the sun is because the sun’s rays are focused onto the retina. This is so much energy that it causes swelling and damage to the delicate cells of the retina that may be permanent and irreversible. It may not be immediate but will show up in the hours following. It’s like a burn.
First as the sun starts to go behind the moon the it creates a small crescent of “Pearls” that then decrease into a diamond shape just immediately before totality. This is still dangerous until it is in total eclipse. One should not directly view the eclipse except for the brief minute that it will be in totality. The best way to know it would be safe is to check the meteorological times for totality if you are even in a zone where that will happen.
Sunglasses are not enough protection. Even with the darkest lenses in them. they simply can not protect the eye enough from the intense light from the sun. It’s not actually brighter than normal but because the moon blocks much of it it is more comfortable to look at the bright sun without squinting or blocking part of the sun. This is a false safety. It is not safe. Solar glasses block 100,000 times more than sunglasses making them your safe way to view. Eclipse glasses allow just 0.0001 percent of the light that falls on them through.
Otherwise, safety first. If you wish to view it directly there are only a couple of safe ways to do this. Order right now a set of solar eclipse glasses.They should be marked with ISO 12312-2015. You can order these from the American Astronomical Society, Amazon, Walmart and some libraries are selling them. If they show any sign of holes or damage do not use them. Also a welders goggles rated 14 or higher would be considered safe.
Indirect ways to view include the old pinhole camera trick. Take two pieces of cardboard or cardstock. Put a pinhole in the front one so that you can create an image onto the second one. Do this with your back to the sun. If you wish to increase the size of the image don’t make the hole larger, just slide the second piece of cardstock further away from the first piece. You can also use a spaghetti colander or slotted spoon to make an image on the sidewalk.