Answer: the four terrestrial planets must once have been hot enough to be molten (like a liquid)
Explanation: Terrestrial planets can be defined as any planet of the solar system or any exoplanet which is "Earth-like" in the sense that it is composed primarily of metals and rock, in contrast to a planet which is a gas giant.
Within the Solar System, the terrestrial planets are the inner planets closest to the Sun, i.e. Mercury, Venus, Earth, and Mars.
Scientist believing that the densest, heaviest materials are at the center and not evenly distributed can be due to the fact that they must once have been hot enough to be molten. In this case, density will take place, making the heavier under and the lighter on top.
Its been a while since I did this topic, but I believe it was mostly because under communism there was little work for intellectuals, so they were often the ones who left the country. This resulted in a 'brain drain', a lack of knowledgable people. I seem to remember reading about the entire maths department of a university just up and leaving at one point. You could also argue that it was damaging for the image of communism if so many people were trying to leave.
To move a flashlight across the paper, you first need a flashlight, a piece of paper, and at least one functioning hand. Then you put the light in your hand and slowly pull your hand in any direction you wish above the sheet of paper.
The origin of Buddhism points to one man, Siddhartha Gautama, the historical Buddha, who was born in Lumbini (in present-day Nepal) during the 5th century BCE.
He saw one of the yellow spotted lizards