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 Earth rotates on its axis with a period of 0.9972 days. The Sun rotate â¦ s on its axis with a period of 25.05 days. All periods are reported in Earth days, and are sidereal time, which is the time for rotation relative to the distant stars.he sun and earth are exerting a gravitational pull on each other, but at the same time the angular vel â¦ ocity of the earth stops us falling into the sun. These two opposing forces allow the earth to stay in orbit around the sun. The same mechanism occurs with the moon and earth system, but on a smaller scale.