Until we can travel faster than light, or, we meet our maker, we’ll never know if we are all alone or not.
The fastest plane, SR-71 also known as Blackbird flew at Mach 3+ speed. Mach = speed of sound = 768 miles per hour = 0.213 miles per second. So the maximum speed achieved by a man made object is 0.65 miles per second.
You can see we are a very long way away from speed of light = 186,000 miles per second (compared to 0.65 miles per second by SR-71).