For many centuries, humans have taken advantage of tools that translate and bring into our perception natural phenomena that we can't perceive with our senses. In some cases, this consists of simply amplifying signals that feed into our normal sensory inputs (e.g., telescopes can bring into clear view that which is too far away for our eyes to perceive on their own). Other instruments turn signals that we cannot perceive into ones that we can observe. Some of these take the form of expanding the reach of our current senses, such as creating visible images based on the ultraviolet spectrum of light or changing sounds that are normally outside the range of what human ears can hear into audible signals. Alternatively, some instruments measure properties for which we have no sensory capacity at all and change them into that which we can observe.