matter that emits no light at any wavelength is called dark matter.
a force is a push or a pull that acts upon an object as a results of its interaction with another object. these two forces are called action and reaction forces and are the subject of newton's third law of motion. formally stated, newton's third law is: for every action, there is an equal and opposite reaction.
thinking not sure but gammer rays are high energy and may cause damage to healthy cells