The speed of light in a vacuum is approximately 299,792,458 meters per second (about 186,282 miles per second). This is the maximum speed at which light can travel. As of our current understanding of physics, light travels at this speed in a vacuum and is generally considered to be the fastest speed possible in the universe.
When it comes to human vision, the speed of light itself is not a limiting factor for our ability to see it. In fact, we perceive light when it interacts with our eyes and stimulates the light-sensitive cells called photoreceptors in the retina. Our visual system is adapted to detect and process light within a specific range of wavelengths, which we perceive as the visible spectrum.
The visible spectrum ranges from approximately 400 to 700 nanometers in wavelength, corresponding to violet, blue, green, yellow, orange, and red light. If light were to travel at a significantly different speed, such as slower or faster than it does in reality, it would not affect our ability to see it within this visible range. We would still perceive light as long as it fell within the visible spectrum.
Therefore, regardless of the speed at which light travels, as long as it falls within the visible spectrum and interacts with our eyes, we would still be able to see it.