Since 1990, based on the Type Ia Supernova observations, it was established that our universe is dominant with some unknown quantities which generally referred to as Dark Matter and Dark Energy. The term dark has been used to represent the form of quantity which does not interact with light or mainly any known particles. Since, the unknown substance is electromagneticaly neutral, hence the unknown sector has been dubbed as a dark sector. The dark matter is referred to as a form of substance which is essential for structure formation and found to be pressureless. This form of matter can be considered as a gravitating system, which behaves as a dust matter. While the form of dark energy can exhibit a repulsive effect (opposite to the gravitational force), that can generate negative pressure, making universe to grow bigger and bigger with an acceleration. It has been found that the major constituents of our universe is dark energy which is 70%, then dark matter 26% and then rest of the matter from which all the galaxies and visible structures are made of.
UNITS- Q uestion you need ton first understand the meaning of science. Science means MEASUREMENTS. In every field of science we do measurements, science only cares about measuring things. That means the things have to be observable. That’s why in science we don’t take care about FEELINGS. Because we can’t measure feelings. Now as we measure something, we need to represent it in some notation to identify or distinguish between quantities. Because whatever we measure it’s just number, if I say you the speed is 5. What info can you tell about 5, it’s just a number, it nothing tells you about anything related to speed. So you need to specify specific quantities to extract info. Actually speed refers to unit distance travel in unit seconds. So the unit distance can be shown in centimeters, meters, and kilometers. Generally we show distances in meters because it acceptable internationally and it is general notation we use in physics. So the (SI) unit of speed is meters per second. So, yo...
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