Big Bang Physics

Imdad Mansoor.S wrote: "The Big Bang formed both planets and asteroids. All of the planets are nearly round in shape, but many of the asteroids are not. Why is this?"

Well, planets and asteroids are about as far away from Big Bang Physics as you can get! They presumably formed billions of years after the BB. Your actual question is about formation of the solar system, some 5 billion years ago.

The short (and rough) answer is: all the planets presumably started out as so-called "planetisimals", somewhat like the asteroids today – too small to have large gravity on their own, leaving them odd-shaped. But, combined they had enough gravity to clump together and form fairly rounded planets and moons, due to the larger own gravity. Due to gravitational heating, most planets and moons had liquid mantles, at least for some part of their history. It is thought that the giant planet Jupiter prevented a normal planet to form at the distance of the main asteroid belt and left many planetesimals.

For the long answer, start by reading this internet link:http://stardate.org/resources/ssguide/planet_ form.html

I ever heard someone founded such formulation of number series, showing that the planets of our solar system are right in its place. However, according to his series, there is a 'lost' planet right in the position of asteroid belt. He then proposed that the belt was a planet and somehow broken into pieces that we called it asteroids. Need correction and further suggestion.

It is called the "Titius-Bode law of planetary spacing". You can read my engineering summary in a pdf download from this page: http://www.einsteins-theory-of-relativity-4enginee rs.com/articles.html

My son told me (I was working at the time, so couldn't check his source myself) that a Planet has just been defined as a body orbiting the Sun whose own mass/gravity is sufficient to make its shape approximately spherical. As a result, Ceres the largest Asteroid (or ex-asteroid) has been upgraded to planetary status. This look like begging the question - a planet is round because if it's not round it's not a planet - but also answers it. Gravity will pull a planet into shape but an asteroid's gravity isn't strong enough to do so if it is knocked out of shape by a collision.

Gravity is proportional to diameter cubed, right? All other things being equal? So a planet that's twice as wide as another would have eight times the gravity.