為什麽質量太大的物質,如太陽,會有重力的出現?

In fact, any object that has mass produces an attractive force around it. In classical theory, the mass produces a graviational field, which when acted upon another mass, gives the graviational attractive force.

In General Relativity, the origin of graviational attraction is explained as a result of warpping of space (i.e. making the space curved) by a massive object.

Qunatum mechanics was originally formulated to deal with objects in very small scale, such as nuclear particles. It is not aimed to explain phenomenon in very large scale, such as plantes, stars and galaxies in the universe.

With the development of quantum field theory, elctromagnetic force is formulated in the quantum mechanical way as the exchange of particles called "virtual photons". Togehter with the other two fundamental forces of nature, strong and weak nuclear interactions, the forces of nature, apart grom gravity, can be explained in terms of particle exchange using qunatum mechanical formulation.

Physicists then believe that gravity should also be formulated in such quantum mechanical way. The concept of "graviton" thus arises. It is postulated that grvitational attraction comes from the exchange of the particle "graviton" between two masses. Thus, a more massive object would emit gravitrons far more than a less massive object.

But up to now, experimental confirmation of the existence of graviton still not achieved.

You may be able to get some hints on the quantum theory of gravity in the following web-page:

http://www.physlink.com/education/AskExperts/ae620.cfm

Actually, not only massive object, but every object that have mass would produce gravitational field. According to relativity, the field actually means the deform of space and time around mass and the field is created by any mass. However, there's no theory of quantum mechanics that can successfully explain gravity effect.