# Does the orbit of a planet cross the orbit of another?

The size of universe is beyond imagination. It is made up of thousands of galaxies and one of these thousands of galaxies is our own galaxy i.e. Milky Way. Milky Way is made up of billions of stars and one of these billions of stars is our own Sun. Sun has its own solar system in which 9 planets keep on revolving around the sun in a fixed orbit due to the gravitational pull of sun.

Just like Sun every star in Milky Way has its own surrounding system and even the stars present in other galaxies also do have same or even more diversified surrounding system. So there are billions of stars in whole universe and trillions of planets revolving around them in different systems, here we will not take up the astronomical facts about whole universe, so that we can focus only on one of trillions of systems i.e. our own solar system in which our mother planet is revolving.

The Orbits
An orbit can simply be defined as a curved path or movement of an object around some fixed point in the space. Mainly two types of forces are responsible to keep an object revolving around its fixed point in a fixed orbit; these forces are electrostatic force and gravitational force. Electrostatic force makes an electron to revolve around a nucleus in a fixed orbit, similarly gravitational force makes an object i.e. planet, asteroid, satellite etc to revolve around another heavier object i.e. star, planet or a black hole.

Every planet in our solar system has a fixed orbit, in which they revolve around Sun due to their gravitational equation. The size and radius of an orbit depends upon the mass and distance of two objects from one another. Planets, asteroids, comets etc all have different masses and different distances from sun, mo they have different orbital motions around the sun.

Mechanism of orbits
This question may always trouble you that what makes an object like planet to revolve around another object like and that too in such a precise and balanced motion.

Well you can locate answer through simple experimentation. Take a half filled glass of water and revolve it in circular motion at high speed in such a way that at top position glass faces downwards. You will note that water will not fall out of glass. This happen because of orbital motion attained by water, in this case orbital motion work against the gravitational pull of earth but in case of planetary system gravitational pull facilitate the orbital motion.

Exact explanation of orbital motion of planets can be located in Big Bang theory. According to Big Bang theory everything in universe came out of an extremely dense zero point and currently the universe is in expansion phase. During the primitive days of universe, molecular clouds came so close to one another that under high pressure nuclear fusion reaction began that created many stars including Sun. Initially sun was very unstable and many explosions occurred in it, these explosion produced large amount of solar dust which projected out of sun at high speeds, but due to gravitational pull these dust particles failed to escape the gravitational field of sun and they attained a projectile motion around sun, but due to strong gravitational force the solar dust escaped the impact of centrifugal force and they started an endless journey around sun. With the fusion of this solar dust and high energy reactions, planets and their satellites came into origin. These planets started revolving around the sun in their fixed resultant orbits. The shape and radius of these orbits depend upon the size, weight and distance of planets from the Sun, because according to Newton’s law of gravitation the gravitational force between two objects is a direct function of distance between them.

Intersection of orbits
In our solar system no orbits intersect each other excluding the orbits of Pluto and Neptune. Now a very common question may strike your mind that “Can both planets collide with each other?” Well, the truth is that a collision between Neptune and Pluto is impossible to occur for at least next 10 million years and it is very unlikely to occur even after that.

Why they can’t collide?
On a two dimensional plane, we can clearly find the intersection of orbits of Pluto and Neptune. But on a 3 dimensional plane we will not find any intersection, because orbits of Pluto and Neptune pass above or below to one another. So, even when we see both plants colliding with one another on horizontal axis then the actual distance between them is actually more than 2 billion Kilometers on vertical axis. Moreover, with such a large distance between the orbits, it is eventually impossible that both planets will attract one another due to the gravitational force existing between them simply because this distance is very large for such an incidence. So, friends don’t worry these two planets of our solar system will never collide with one another.

Category: Astronomy, Science