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Hydrostatic weighing, also referred to as underwater weighing, hydrostatic body composition analysis and hydrodensitometry, is a technique for measuring the density of a living person's body. It is a direct application of Archimedes' principle , that an object displaces its own volume of water.
Air displacement plethysmography (ADP, also known as whole-body air displacement plethysmography) is a recognized and scientifically validated densitometric method to measure human body composition. ADP is based on the same principles as the gold standard method of hydrostatic weighing , but through a densitometric technique that uses air ...
A solar equinox is a moment in time when the Sun crosses the Earth's equator, which is to say, appears directly above the equator, rather than north or south of the equator. On the day of the equinox, the Sun appears to rise "due east" and set "due west". This occurs twice each year, around 20 March and 23 September. [a]
An often-cited 1980 orbital model by Imbrie predicted "the long-term cooling trend that began some 6,000 years ago will continue for the next 23,000 years." [ 46 ] Another work [ 47 ] suggests that solar insolation at 65° N will reach a peak of 460 W·m −2 in around 6,500 years, before decreasing back to current levels (450 W·m −2 ) [ 48 ...
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In addition the tilt, or obliquity, of the Earth's axis is not constant but changes in a cycle of its own. During a cycle that averages about 40,000 years, the tilt of the axis varies between 22.1 and 24.5 degrees. [4] The precession of the axis of a spinning body as seen on a small scale in a gyroscope.
The Persian calendar begins each year at the northward equinox, observationally determined at Tehran. [15] The Indian national calendar starts the year on the day next to the vernal equinox on 22 March (21 March in leap years) with a 30-day month (31 days in leap years), then has 5 months of 31 days followed by 6 months of 30 days. [15]
Thus the equinox moved 54° in one direction and then back 54° in the other direction. This cycle took 7200 years to complete at a rate of 54″/year. The equinox coincided with the epoch at the beginning of the Kali Yuga in −3101 and again 3,600 years later in 499. The direction changed from prograde to retrograde midway between these years ...