If you've ever looked at the solar system, you've probably noticed that the sun, planets, moons, and asteroids lie roughly on the same plane even though the universe around us is three-dimensional.

You may have wondered why.

Here is the answer.

It was a cloud that shrunk

The solar system - before it was formed as we see it today - about 4.5 billion years ago, was just a huge cloud of dust and gas revolving around itself, with a size of 12 thousand "astronomical units" (AU), and the average distance between the Earth and the sun is about 150 million kilometers.

Although this large cloud contained only dust and gaseous particles, it began to collapse and shrink on itself under the influence of its mass, says Nader Hagibor, an astronomer at the University of Hawaii at Manoa, for "Live" website. Science" (Live Science).

As the cloud began to collapse, its rotation speed increased due to the same physical laws that allow a skater to spin faster when their arms and legs are closer to the vertical axis of rotation.

The meninge gradually turned into a flat disk of little thickness for its size.

It's similar to what happens when a pizza maker throws a piece of dough into the air and it expands as it rotates and becomes thinner and flatter little by little.

This is exactly what happened to the solar system very early in its inception, according to the same source.

Meanwhile, within this rotating cloud, gas molecules gradually condense into a spherical shape and exert mutual pressure among themselves, which leads to their heating.

When the ball reaches a mass estimated at about 70 times the mass of Jupiter, the hydrogen and helium atoms merge under the pressure of tremendous heat and pressure, and launch a nuclear reaction that secures the balance of the new star, which is the sun, for billions of years.

Over the next 50 million years, the Sun continued to grow by sucking gas and dust from its surroundings, releasing waves of intense heat and radiation.

The birth of a new star in the center of the disk of gaseous matter (NASA)

The cloud continues to collapse

As the Sun grew, the cloud continued to collapse, forming a flat disk in the center of which the Sun was located, and became wider with time.

With time, it turned into a flat structure called a protoplanetary disk, orbiting the young star and extending its diameter across hundreds of astronomical units around the sun and a tenth of that distance thick.

Over the tens of millions of years after that, the dust particles in the protoplanetary disk were gently swirling around each other, sometimes bumping into each other to form larger and larger objects over time, according to Hagpour.

Eventually, most of the material in the protoplanetary disk stuck together to form massive spheroids.

Some of these objects grew due to gravity, forming the planets, dwarf planets, and moons known today.

Some of the other objects - smaller and more irregular in shape - became asteroids, comets and small moons.

Despite the different sizes of these objects, they remained at the same level that formed in the disk resulting from the primordial gas cloud.

The beginning of the formation of bodies in the solar system in the same plane (NASA)

For this reason, even today, the eight planets in the solar system and the other celestial bodies orbit about the same, except for some relatively small bodies such as the dwarf planet Pluto, which has an orbital inclination of about 17 degrees relative to the plane of the solar system.