No, light is not visible in a vacuum. In order for light to be visible, it needs a medium through which it can propagate and interact with matter. In everyday circumstances, light often travels through air or other transparent materials, allowing us to see it.
However, in a vacuum, which is an environment devoid of any material or particles, there is no medium for light to propagate through. Therefore, light does not become visible to the human eye in a vacuum.
It's worth noting that light can still exist and propagate through a vacuum, but it remains invisible to the naked eye. In fact, the concept of the speed of light in a vacuum, which is approximately 299,792,458 meters per second, is a fundamental constant in physics. The speed of light in a vacuum is the fastest speed at which information or physical influences can travel through space.