Ultimately, all scientific studies works by expanding human sensory limitations.

Both vision and hearing perceives next to nothing of the energies that the universe is made of.

Below you can see what the electromagnetic spectrum consists of.

The units in the top bar ("nm") is the unit "nanometer" and means "billionth a meter."

0.01 nm - 1 nm Gamma radiation Radiations, made by nuclear decay.
1 nm - 100 nm Roentgen radiation Also called X-rays. Used to make X-ray pictures.
100 nm - 400 nm Ultra Violet light These rays are in the sunlight, and tans our skin.  
400 nm - 700 nm         Visual area Visible light, perceived without any aid.
700 nm - 1mm Near infrared Light between heat-radiation and red light.
1mm - 1 cm Infrared Heat radiation
1 cm - Micro and radiowaves    Radio transmissions

 Our equipment is able to register almost anything in the spectrum.