Light takes almost 8 minutes to reach Earth from Sun. So, now give it a second thought. What will happen if the Sun vanishes suddenly? I meant just think about the situation where the Sun vanishes. Well many scientists have already written and proved so much about it nowdays but few decades ago scientists were not pretty much sure about the outcome of such a thing. Newton, the father of gravity, proposed that as the gravity is the fastest thing in this universe so light will travel along gravity i.e. it will take 8 minutes for us to realize that our Sun has gone missing. He was half right then.
Few decades after Newton gave the above theory another brilliant scientist ever to live in this world Sir Einstein gave His famous theory. He demonstrated that the speed of the light is the maximum possible speed which any body can attain in this universe. So this means either the Newton was wrong in saying that gravity is the maximum limiting speed in this universe or it may happen that gravity and light are the same thing having different names. First option was the right option. Einstein proposed a model of space and time. Our universe is covered with a fabric of space and time in multi dimension layer. Everybody according to its size and weight exerts a pressure on this fabric. Our Sun does the same and so celestial bodies revolve around it. Our Earth too does the same so Moon revolves around it. So coming back to our discussion that what will happen to Earth if the Sun will vanish suddenly. So as soon as the Sun will disappear the pressure exerted by it on the fabric will ceazes to exists. This will cause ripples of space and time flowing in every direction from the middle point. Ripples speed will be equal to the speed of light and after 8 minute our Earth will leave its path on which it revolves around the Sun in an trajectory way. So till 8 minutes we will never be able to know that does our Sun has disappear or not. We will only feel the darkness after 8 minutes. This also open discussion on the relativity concept. Nothing is constant in this world.