Hassan Sayyaadi - Professor, School of Mechanical Engineering, Sharif University of Technology, Azadi Street, ۱۱۱۵۵-۹۵۶۷, Tehran, Iran
Dorin Javaherneshan - B.Sc. Graduate, Sharif University of Technology, Azadi Street, Tehran, Iran

One of the recent theories in physics and cosmology is the subject of dark energy and the ex-pansion of the universe, which according to the findings of radio telescopes and the Hubble telescope, some evidence has been provided and some believe the universe continues expand-ing. In contrast, hypotheses can be made that the universe behaves oscillating (expansion-contraction). This article assumes that the universe follows the second theory, meaning that there is a contraction that leads to collapse and another big bang (big bounce). Although there is no evidence on whether or not our universe has an oscillation behavior, this paper pre-sumed this theory is correct. The universe has been modeled as a circular plate that vibrates radially. This geometry has been taken since writing equations, and solving them on a 2D ge-ometry is much simpler than a 3D one. Then, by writing Newton’s second law on an element of this round plate and applying boundary conditions that are close to the reality of the uni-verse, an equation is obtained for natural frequency. Eventually, the first period of vibration is derived using the Hubble constant’s last measured value in one of the obtained formulas. A vibratory model is derived here in this article and the results are discussed appropriately

Universe; Expansion; Contraction; Vibratory Model; Natural Frequency