My question is regarding effect of Sun's gravity on earth. I want to know that if Sun's gravity can change Earth's landscape in long duration (i.e. billion of years) or not? Means if earth is dead planet and all other planets are not present in the solar system and Earth is as near as Sun as mercury currently orbiting. And also suppose Earth's surface is not smooth (because of hitting with other small bodies at regular interval) then can Earth's surface can be smooth in long duration by gravity of Sun or not?
if ... all other planets are not present in the solar system and earth is as near as sun as mercury currently orbiting.
If the earth is as close to the sun as Mercury, there would be no liquid water for erosion. Also, the earth would become tidal locked so there would be no tides.
Tidal forces could change the landscape of a planet or moon. The effect could be leveling or mountain building as with volcanoes. In 1979 Voyager 1 revealed plumes and mountain building from volcanic activity. Tidal forces between Jupiter and the moon Io created this internal stress and heat source. If a planet or moon's surface were not level this same activity could smooth things out. Our moon has thousands of craters because there are no tidal forces to generated volcanic or plate activity to smooth them out. On the other hand Earth's craters have long been covered up.