It's a common misconception that the universe is expanding at the speed of light. In reality, the expansion of the universe is a bit more complex.
According to the prevailing cosmological model called the Big Bang theory, the universe began from an extremely hot and dense state and has been expanding ever since. However, the rate of expansion is not directly tied to the speed of light. The expansion is described by a parameter called the Hubble constant, denoted as Hâ‚€. Currently, the most accepted value for the Hubble constant is about 70 kilometers per second per megaparsec (km/s/Mpc). This means that for every megaparsec of distance between two galaxies, the expansion causes them to move away from each other by about 70 kilometers per second.
The expansion of the universe primarily affects the large-scale structure of space, such as the distances between galaxies and galaxy clusters. On smaller scales, within our own Milky Way galaxy and its immediate neighborhood, the force of gravity is dominant. Gravity is much stronger than the expansion of the universe over these small scales. Therefore, gravity holds galaxies, star systems, and planets together and prevents them from being carried away by the expanding universe.
To put it simply, the expansion of the universe does not affect local gravitational systems like our solar system. The planets in our solar system stay in their orbits because they are bound to the Sun by gravitational forces. These gravitational forces are much stronger than the effects of the universe's expansion at these relatively small scales.
It's important to note that the expansion of the universe becomes more significant on larger scales, where the overall structure and distribution of galaxies are affected. On such scales, the expansion becomes apparent through the observed redshift of distant galaxies and the increasing distances between them.