We have received this question enough that it is time for a blog post about it. Here goes:
Here is the straight scoop on what the glasses actually do. You cannot look directly at the Sun, because even if it is covered up 99%, you will blind yourself due to the harmful UV rays it puts out. This is true whether or not an eclipse is happening.
Normally, we don’t look at the Sun, because there’s no reason to, and because we’re conditioned not to – it’s too bright! But during an eclipse, we know that there is “something interesting” taking place up there, and so we want to look at it. That’s where the eclipse glasses come in. You will NOT use them as regular eyewear. You will NOT wear them and walk around – you’ll trip over things because they’re so dark you won’t be able to see anything!
You will CERTAINLY AND ABSOLUTELY NOT drive with them on!!
You are not using them to guard against any special “eclipse rays” – which in actuality do not exist!
What you WILL do is, from time to time, decide that hey – you want to look at the partial phases of the eclipse as the Moon moves more and more over the Sun. You want to watch the progress of the eclipse. So, you put them on – or just hold them up to your eyes – and holding them in place (so they don’t blow away) you tilt your head back and look up at the Sun through them. You’ll see the Sun as an orange ball, because the glasses are blocking out all the harmful rays. You’ll see the “bite” that the Moon is taking out of the Sun. And then you’ll look away from the Sun and remove them from your eyes, and go on with your daily life or your eclipse preparations or whatever.
At some point maybe five minutes later, you’ll want to look again up at the Sun – so you’ll do the same thing: hold the glasses over your eyes and lean back and look at the Sun through them. You’ll see a BIGGER bite, because the Moon has moved that much more in its orbit around the Earth, and is now covering more and more of the Sun.
If you’re not in the path of totality, you can do this over and over. You’ll see the Moon take a bigger and bigger bite, until finally it has covered all it’s going to cover. Then, you’ll be able to watch (always through the glasses) as the Moon slowly moves off, and the bite gets smaller. Then, the Moon will move completely off, and the eclipse will be over. You watched the progress, and you always did it with the eclipse glasses on.
If you’re in the path of totality, the same sequence of events happens, and you’ll do exactly the same things with the glasses to watch the partial phases. Except that because you’re in the path, there comes a point when the Moon covers up ALL of the Sun. This is the moment we’ve been waiting for – totality!!! While you need to use the eclipse glasses for the partial phases, you DO NOT use them during totality! You can’t – you won’t see anything! You watch totality with your naked eyes in complete safety. Why? Because the Moon is completely covering the Sun and there are no harmful rays getting to your eyes!
But once totality is over, and the bright Sun again shows the diamond ring as the Moon moves off, then you need to use the glasses again.
The “eclipse glasses” are really only for the partial phases – NOT for totality! They are a filter device, designed to look THROUGH, AT the Sun, ANY time that it is not being TOTALLY eclipsed.