Grey dot or circle inside "smoke ring" cloudI work out of my home. Earlier today, I decided to take advantage of sunny conditions to go work outside, so I took my notebook computer out to the back patio and set it up. Although the day had started clear, thunderclouds started building up before noon. Much of the sky to the north was cloudy, but the sky to the south was clear. The stormclouds were well defined. There wasn't much overcast or haze, just stormcloud or clear blue sky. I need to take frequent breaks when working on the computer outside, because of glare on the display. So, at one point, I leaned back and looked straight up into the sky. I noticed that there was a very well defined thundercloud to the north, scattered cloud overhead and blue sky west and east. Directly overhead, there was what looked like a smoke ring, about the size of my thumbnail held at arm's length. It was perfectly circular and appeared to be swirling inward on itslelf. In the centre of the smoke ring was a grey dot or small circle. At first, the dot was almost as large as the area inside the smoke ring, about the size of a fingernail at arm's length. Over the next several seconds, the grey dot appeared to get smaller, then disappeared. The smoke ring remained, but gradually (over about a minute or so) dissipated.