Uranium
In nature, uranium is found as uranium-238 (99.2739–99.2752%), uranium-235 (0.7198–0.7202%), and a very small amount of uranium-234 (0.0050–0.0059%). Uranium decays slowly by emitting an alpha particle. The half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years, making them useful in dating the age of the Earth.
Astrological transit
Uranus takes about 84 years to complete a full return. However, one of its most important influences is felt when it reaches the halfway stage in its journey, at around age 42. The Uranus half-return is the origin of what for many people is the 'mid-life crisis'. Women, especially those with children growing up and leaving home, may feel that life has passed them by. A lot of women also begin the pre-menopause stage at this time, and many men experience the 'male menopause'. Permanent and successful long-term relationships may be unsettled or disrupted by casual flirtations and affairs. The Uranus half-return can be stressful and tense, but also energising. It is the ideal time for people to break out of routine lifestyles that they have been stuck in for years, and develop new interests.