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Welcome to our Physics lesson on Dark Matter, this is the seventh lesson of our suite of physics lessons covering the topic of Galaxies and Hierarchic Structures in the Universe, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
Scientists believe that a large deal of matter in the universe is invisible and undetectable through actual devices (that is, devices within our current technological knowledge). This "dark matter" is supposed to exist inside the galaxies, predominantly in halos but also in the space between galaxies, as a component of groups of galaxies. The only indicator of dark matters' existence is the difference resulting in the total gravitational force existing in the universe and the theoretical gravitational force if the existence of this dark matter is not considered.
It is probable that the amount of dark matter in the universe is 10-100 times greater than that of the actually detectable matter. If the existence of dark matter is confirmed, this will be a huge achievement in science, as it will allow scientists to understand the future of Universe.
What is the characteristic wavelength of dark matter (if identified and everything discovered about it is in accordance with the actual theory)?
Using Wien's Law equation
where b = 2.898 × 10-3 m · K is the Wien's constant and λm is the characteristic wavelength of radiation. Since the temperature of the universe is T = 2.73 K, we have for the characteristic wavelength of dark matter:
This is a kind of microwave (the range of wavelengths for microwaves is 10-5 m to 10-1 m).
You have reached the end of Physics lesson 22.6.7 Dark Matter. There are 7 lessons in this physics tutorial covering Galaxies and Hierarchic Structures in the Universe, you can access all the lessons from this tutorial below.
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