Human immunodeficiency viruses are the one which infects human over time. The virus infects human body cells and progresses towards immune system failure which creates life threat for a patient. The disease is incurable till date but the effects can be slowed down by the medication and treatments. The disease in contagious and spreads by transfer of infected blood.
The half of the Moon that points toward the Sun looks bright because it is lit by sunlight. The Moon appears to change shape because we see different amounts of the lit part as the Moon orbits Earth. ... As it moves around Earth, more and more of the lit side comes into view.
