User talk:Dildarpk

'''About physical sciences The physical sciences investi gate the nature and behavior of matter and energy on a vast range of size and scale. In physics itself, scientists study the relationships between matter, energy, force, and time in an attempt to explain how these factors shape the physical behavior of the universe. Physics can be divided into many branches. Scientists study the motion of objects, a huge branch of physics known as mechanics that involves two overlapping sets of scientific laws. The laws of classical mechanics govern the behavior of objects in the macroscopic world, which includes everything from billiard balls to stars, while the laws of quantum mechanics govern the behavior of the particles that make up individual atoms.

Other branches of physics focus on energy and its large-scale effects. Thermodynamics is the study of heat and the effects of converting heat into other kinds of energy. This branch of physics has a host of highly practical applications because heat is often used to power machines. Physicists also investigate electrical energy and energy that is carried in electromagnetic waves. These include radio waves, light rays, and X rays—forms of energy that are closely related and that all obey the same set of rules (see Electromagnetic Radiation).

Models of the Universe According to the widely accepted theory of the big bang, the universe originated about 14 billion years ago and has been expanding ever since. Astronomers recognize four models of possible futures for the universe. According to the closed model, many billions of years from now expansion will slow, stop, and the universe will contract back in upon itself. In the flat model, the universe will not collapse upon itself, but expansion will slow and the universe will approach a stable size. According to the open model, the universe will continue expanding forever. In the accelerating expansion model, the universe will expand faster and faster until even the particles in normal matter are torn away from each other............'''