Urine is made up of range of organic compounds such as proteins and hormones, inorganic salts and numerous metabolites. These by-products are often rich in nitrogen and need to be removed from the blood stream through urination. The pH level of urine is typically around (pH7) but varies depending on diet, hydration levels and physical fitness. The color of urine is also determined by these factors, with dark-yellow factors, with dark-yellow urine indicating dehydration and greenish urine indicating of excessive asparagus consumption.
There are two main ways of measuring time: dynamic and atomic time. The former relies on the motion of celestial bodies (including the Earth) to keep tract of time, whether it’s the rotation time of a distant spinning star such as a pulsar, the motion of a star across our night sky or the rotation of the Earth. However, a spinning star notwithstanding (which can be hard to observe), these methods are not always entirely accurate.
The old definition of the second was based on the rotation of the Earth. As it takes the Sun one day to rise in the east, set in the west and rise again, a day was almost arbitrary divided into 24 hours, the hour into 60 minutes, the minute into 60 seconds. However, the Earth doesn’t rotate uniformly. In fact, its rotation decreases at a rate of about 30 seconds every 10,000 years due to factors such as tidal friction. Scientists have devised ways to account for the changing speed of the Earth’s rotation, introducing ‘leap seconds’, but for the most accurate time you have to go even smaller.
Atomic time relies on the energy transition within an atom of a certain element, commonly caesium. By defining a second as the number of these transitions, time can be measured with an accuracy of losing a tiny portion of a second in a million years. The definition of a second is now defined as 9,192,631,770 transitions within a caesium atom.