I persuade you not to stare the sun directly, it will really do harm to your eyes. The strong rays and ultraviolet will stimulate your retina; they will burn your eyes. The strong rays will damage your eyes, but you will never have something feel discomfortable, that is because there have no sense of pain in the retina. The burning degree will relate to the staring time and level of rays. After the staring at sun, the vision will decrease, even distortion of the image, the most serious one is blind. Some damage would be recovery, and others will be permanent visual injury. Some people get eyes damage when they observe the solar eclipse, that is a strong evidence for the harm of sun rays.