Glowing ball UFO at Stonehenge, computer artwork. Glowing ball UFO reports are common. While such a report may not be satisfactorily explained, there are several possible explanations. Seeing a known object under strange conditions may lead the observer's imagination to mislead them, or this could be a known atmospheric phenomenon such as ball lightning. Circles of standing stones, like Stonehenge in Wiltshire, England, were probably used to make astronomical calendar observations. Stonehenge's construction dates from about 5000 years ago. The largest stones are over 7 metres high and weigh 40 tonnes.