2 Measuring vitamin D levels is also expensive, costing between $50 and $220 per test in commercial laboratories for patients without insurance. Another challenge is that the level of 25-hydroxy-vitamin D that should be considered normal is unclear.
The closer a planet is to the sun, the shorter the time to complete one revolution is. Mercury, for example, has an orbital period of 88 days while it takes Jupiter about 11.86 years. The period of the Earth's orbit is usually thought to be 365 days as calendars show. However when averaged it is actually about 365.25 days, which requires an extra day on the calendar every four years (causing a leap year). Contradictions within orbit times are probably caused by the ages of the sources.
The Geological period consists of time periods in the origin and evolution of earth. The earth is about 4.5 billion years old. The time from the origin of the earth to the present is divided into super eons, eons, eras and periods. The Precambrian period is a super eon that is sub-divided into three eons: â¢ the Hadean Eon (4.5 to 3.8 billion years before present), â¢ the Archean Eon (3.8 to 2.5 billion years before present),, and.