What Galileo did was point his telescope at things of interest up in the sky, the Moon, Jupiter, Venus and so on, and demonstrate to anyone with at least one working eye and a modicum of open mindedness, that things in the heavens weren't always quite the same as they were the day before yesterday. And the single most corruptible of those heavenly bodies turns out to be the Sun.
|One of Galileo's sunspot sketches|
I used the same method myself yesterday. I have a small, 3 inch reflector that's very handy for deep sky objects but also works nicely for projecting the late afternoon Sun onto the ceiling of my porch. I did it to show my granddaughter something she won't see too often - a naked eye sunspot. This one is called AR1476 and it is very big indeed, and active and could interfere with communications and electricity grids down here on the good Earth. The NASA image left shows how large, in comparison to the size of the Sun, this sunspot is. It was clearly visible on my porch ceiling and the grandaughter left having seen it going "Sun, mummy, spot."
My limited technology does not extend, sadly for the moment, to solar filters and the like so I was deprived of having an even closer view. As might have been guessed, sunspots have structure so large magnification reveals the spot to be a roiling mass of fingers of superhot gas, trained by the rippling magnetic fields of the Sun's inner structure poking through into the visible sphere. So this photo from David Maidment in Oman (via spaceweather.com) captures even more wonderment and delight than the NASA picture:
If you have a small telescope or a pair of binoculars, take the occasional safe look at the Sun. It is not just a yellow circle up there to warm and tan you. It is a fascinating object in its own right.