What are some effects of special relativity in the natural world (i.e. not human technology) that are visible to the unaided eye?

Special relativity is a theory developed by Albert Einstein in 1905 and has since revolutionized modern physics. It states that time, space and mass are all relative to one another, meaning they depend on the observer’s perspective or their state of motion. This means that familiar phenomena such as gravity and motion are affected in ways you might not have thought possible before!

In terms of effects visible to the unaided eye, special relativity can explain why stars appear redder when close to the horizon than when they're directly overhead at night. This occurs because, from our point of view here on Earth, light appears to travel faster when it is travelling closer to the horizon than it does when going straight up into space. So stars towards the horizon appear redder due to this relativistic effect called 'time dilation'.

Special relativity also explains why different astronomical objects can appear brighter (or dimmer) depending how close they are relative to us. For example something like a distant galaxy will seem much brighter if it lies between us and an even more distant object; this is known as 'gravitational lensing' - a powerful phenomenon which takes advantage of special relativity's predictions about warps in spacetime caused by massive bodies like galaxies!

There are many other interesting phenomena which occur partially due to special relativity's principles, but these are just some noteworthy examples visible from our own backyard – proving again that you don't need expensive technology or observatories for understanding some amazing aspects of modern physics!