Hello friends and fellow Physics enthusiasts At the beginning let me confess that I am more of a sleeping member though I do follow this forum quite closely. Today, I am posting to seek some help from fellow Physics educators. I hope this is the right section of the forum to post, if not, I would like to request the moderator to be kind enough to move it to an appropriate section. A few days back, I had an argument with a person on a social media platform regarding the effect of the absence of diurnal motion (rotation of Earth on its own axis). According to him, there would be a change in "Day-Night" even if only the Earth's revolution around the Sun is present. In support, he also showed a diagram which I am enclosing with this post. I disagreed, arguing that it is not possible that a point on the periphery of Earth will change its position relative to the Sun if there is no rotation of Earth. He then argued that if any other external star system/star is taken as a reference frame then it is possible. I would like to request you all to help me out in the following two points: 1. Is he right? Am I making any mistake in understanding? Is the diagram attached right or wrong? 2. I am unable to formulate a pointed and logical reply in an organized manner to counter his argument. Provided he is wrong, I would like to request you to help me on this. Under the influence of a central force and in absence of any torque, how can the position of a point on the periphery of the object change with respect to the central point or any other reference frame? I hope I have clarified my dilemma and question clearly to the members. If you require any other input, please feel free to ask. I am unable to post the conversation, as it was in my mother tongue "Bengali" and I am sure most of the members here would have no use for that. Thank you all, waiting eagerly for your reply.