Why are the orbits of the sun's planets arranged in a more or less flat plane?

In space there is a collection of dust that appears as clouds. These are called nebula. This nebula keeps on spinning during course of time and then forms a huge ball along with rise in temperatures. The temperatures rising leads to expansion of contents of nebula which result in explosion along its equator. The remains that scatters on almost one plane like disk over the years after spinning on their own axis become planets. Hence the planet's orbits are co-planar. The same applies to our solar system also. read less

The planets are believed by many authorities to have coalesced from a disk-shaped cloud of gas early in the evolution of our solar system, beginning roughly 5 billion years ago.“We believe that the sun and planets evolved from a huge, swirling cloud of gas and dust that condensed over a time span of hundreds of millions of years”, “This gas cloud was very likely in the shape of a disk, and when the planets came to be within this cloud, they pretty much all formed basically along the same plane.”There is a notable exception the tiny planet Pluto, which has an orbit that is tipped as much as 17 degrees to the plane of the solar system. It has been hypothesized that Pluto might be everything from an escaped moon of Neptune to a special type of minor planet or asteroid. The anomalous orbit of Pluto was one of the reasons for the great debate earlier this year concerning Pluto’s exact status as a member of the solar system. read less