Without the sun, the Earth would be completely inhospitable. It would be pitch-black and the entire planet would freeze. The sun is absolutely essential for life to exist on this planet, and if the sun suddenly disappeared, life on Earth would cease to exist almost immediately. Not to mention the gravitational effect. The loss of the sun could possibly send the Earth drifting around the galaxy in a straight line where we could run into who knows what (black holes, asteroid belts, and other disastrous areas). If the sun disappeared in an instant, then it would greatly affect the ocean’s tides, possibly resulting in tidal waves and tsunamis.
If the moon disappeared it would not have as much of an adverse effect. The obvious effect would be that it would be very dark at night. The moon also plays a large role in the ocean’s tides, and if the moon disappeared, it would upset the balance. This would not mean much to us, aside from it disrupting aquatic life, which could in turn, affect fish and other sources of food. The moon also helps stabilize the Earth’s orbit. The loss of the moon may not completely mess up the planet’s orbit, but it might have at least slight effect on it, which could result in the changing of the seasons and the length of days. There are also many animals that live off of a lunar cycle. Without the moon, many species might die out.
If somehow sun and Moon disappeared than we should apply theory of relativity to get the subsequent result.
If sun would disappear than earth will follow an infinite tangetial path to the suns orbit in the space and time.
And if Moon gets disapper than there would be change in earths rotation as well as revolution period