How to detect 'Dark Matter' ?

Hello everyone, this is the 2nd part of dark matter. In the previous video we learned that dark matter is classified in mainly 2 categories - cold and hot. All these categories refer to the velocity of the dark matter rather than their actual temperature. This indicates how far they moved due to random motion in the early universe. Often this distance is called as 'free streaming length'.Free streaming length(FSL) is referred to the length covered by a particle in a medium without scattering. The size of the particle decides the FSL. If the size is small then the FSL will be large and vice versa. There can be a mixture of the above listed categories also.Although the theory of mixed dark matter was rejected after later. The classification according to the FSL includes protogalaxy.
A protogalaxy or a primeaval galaxy is a cloud of gas forming into a galaxy. The rate of forming of stars decides that whether the galaxy will be spiral or elliptical or irregular.

Cold Dark matter:: cold dark matter is believed to have lower FSL than a protogalaxy. This implies the size of cold matter particles will be large and the velocity will be low.The widely-accepted Lambda-CDM model is based in part of the theory that dark matter is "cold".

On the other hand Hot dark matter is thought to have much higher FSL than a protogalaxy , implying it must have small mass and relativistic velocity
There are various methods in which scientists are trying to detect dark matter. These experiments can be divided into two classes: direct detection experiments , indirect detection experiment.
The link for the first video is here::

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[shibeshmridha]

Great presentation indeed; thank you so much.