**Author details**

the center of galaxy and make it so that the velocities of hydrogen atoms are almost

*Rotational curve obtained from 21-cm line observations of the Milky Way. Note that the velocity of the studied*

The problem of missing matter discovered by Fritz Zwicky in 1933 appears to be still an open question. The most important premise of existence of the dark matter is the shape of rotational curves of galaxies, introduced as a tool for studying galaxy rotation by Vera Rubin. With our current understanding of the Universe, the dark matter, still a mysterious substance, makes up 86% of all the matter in the Universe. Throughout the years various attempts have been made to explain its nature. Some of the ideas have been proven unlikely (MACHOs). Some of them contradict each other (DAMA/LIBRA, the COSINE-100 collaboration). Yet even simple Milky Way's observations as presented in Section 5 lead to the conclusion that the dark

constant as the distance increases.

*objects appears to be constant over roughly 3 kpc distance.*

matter is present in the halo of our galaxy.

**6. Conclusions**

**216**

**Figure 10.**

*Progress in Relativity*

Aleksander Kaczmarek<sup>1</sup> \* and Andrzej Radosz<sup>2</sup>

1 Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland

2 Department of Quantum Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland

\*Address all correspondence to: a.kaczmarek12@wp.pl

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
