The speed of light, denoted as "c," is an incredibly fast speed that plays a fundamental role in our understanding of the universe. In a vacuum, light travels at a constant speed of approximately 299,792,458 meters per second (or about 186,282 miles per second).
When comparing the speed of light to the speeds of other objects in space, such as planets and stars, the vast majority of these objects move at significantly lower velocities compared to the speed of light.
Planetary Speeds: Planets in our solar system have varying orbital speeds around the Sun. For instance, Earth orbits the Sun at an average speed of about 30 kilometers per second (18.6 miles per second). While this might seem fast, it is still much slower than the speed of light. Similarly, other planets in the solar system have orbital speeds ranging from about 10 to 35 kilometers per second, depending on their distance from the Sun.
Stellar Speeds: Stars, including our Sun, also exhibit a wide range of velocities. Stars within our Milky Way galaxy typically have velocities in the range of a few tens to hundreds of kilometers per second relative to their galactic neighborhood. However, even the fastest stars known, which are often those ejected from gravitational interactions or supernova explosions, reach speeds of a few hundred kilometers per second at most. These speeds are still negligible compared to the speed of light.
Cosmic Objects and Expansions: On much larger scales, galaxies can have peculiar velocities relative to the cosmic microwave background radiation, which is a remnant of the early universe. These velocities can reach a few hundred to a few thousand kilometers per second. However, in the context of the speed of light, these speeds are still minuscule.
It is important to note that when discussing speeds in the context of special relativity, it becomes necessary to consider objects moving at a significant fraction of the speed of light. At such high speeds, relativistic effects, such as time dilation and length contraction, come into play. However, in everyday astronomical observations and scenarios, the speeds of celestial objects are far below the speed of light, and classical physics is sufficient to describe their motions accurately.