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Can There Be Such a Thing as a Hollow Planet?

Planets come in a wide variety of sizes and types. From ones made up of gas or frozen balls, to our own world brimming with life. It feels like the options are endless. For example, can there be such a thing as a hollow planet? 

There cannot be such a thing as a hollow planet. There are two reasons for this: the Shell Theorem by Sir Issac Newton and the theory surrounding planets’ magnetic fields. In short, physics and mathematics have shown that a hollow planet is impossible. 

Scientists have not seen the core of planets. At least, nobody has drilled that deep, not even on Earth. Yet, scientists are confident a hollow planet is impossible, starting with how planets are made. Many try to refute this by bringing up Dyson Spheres. But the mathematics, as we will see later in this article, doesn’t pan out…

The Belief in Hollow Planets

It isn’t strange to wonder about hollow planets. This belief has existed almost as long as humans. Most ancient religions featured a hollow world: the Neanderthals, ancient Egypt, the ancient Greeks and Romans, and even Dante’s Divine Comedy features a hell set inside Earth. 

Edmond Halley’s Hollow Earth Theory

Science was not immune to the idea of a hollow Earth, either. Edmond Halley, he of Halley’s Comet, proposed a Hollow Earth theory. Halley came up with this theory while investigating the difference between “True North” and “Magnetic North.”

Halley was frustrated by how True North, the geographical North Pole, was not the same as Magnetic North, where the arrow of a compass points. Halley was especially baffled by how Magnetic North moved, which could have devastating consequences for ships at sea.

Halley came up with his theory after investigating Magnetic North from various places around the world. He suggested that under the Earth’s crust were three spheres, each 500 miles thick. He proposed that these shells “were clean, habitable, well-lit places.”

Why Skepticism Remains

There remain skeptics about what exists under the Earth’s crusts. Humans, after all, have not drilled very far into Earth. The Kola Superdeep Borehole is the furthest we’ve gone, and it only reached 40,230ft-deep (12.2km). Scientists believe you would have to drill 3958.756 miles (6,371 km) to reach the Earth’s core. Thus, we haven’t drilled even 1% down into our planet.

Yet, the majority of scientists maintain a hollow planet is impossible. This begins with what makes a planet.

Planets and Sir Isaac Newton.

The International Astronomical Union has defined planets as:

  1. The celestial object must orbit a star. 
  2. The celestial object must have enough gravity to press it into a spherical form.
  3. The celestial object must have enough of a gravitational force that it doesn’t share its orbit around the star with another. 

The crucial point into why we can’t have a hollow planet is found in the gravitational force required for a planet to be a planet.

This begins when a planet is young and nothing more than a swirling disk of dust and gas in space. As the disk swirls, it gathers mass, which gives it gravity. 

Lava planet formation

The forming planet keeps swirling, and the gravity produces a magnetic field, protecting the planet and preventing the atmosphere from drifting into the universe. The basis of this belief is found in Newton’s theory.

For more detail on how planets are formed, check out my article here.

A planet needs gravity to form its spherical shape. It also requires a gravitational force to keep its orbit clear. Without these properties, a planet isn’t a planet.

To have enough gravitational force, a planet needs enough mass. The shell of a planet cannot have enough mass to produce the necessary gravitational force. This leads to Newton’s Shell Theorem…

Newton’s Shell Theorem

Using a lot of calculus, Newton proved that any object in the center of a hollow shell (like a hollow planet) would be weightless. This is because the force acting on the object doesn’t come from what is above it but the force acting below it. This means the outer shell won’t have enough gravitational force to produce a magnetic field. 

How the Dyson Sphere Proves Hollow Planets Don’t Exist

Dyson Spheres are a popular concept in science fiction, but they began with Freeman J. Dyson, a physicist and astronomer. In 1960 Dyson explored the idea that advanced civilizations in our galaxies (aliens) might have the technology to create a mega-structure.

These artificial shells would, like planets, orbit a star and would also harness solar power. This theory has led to astronomers searching for Dyson Spheres. They’ve yet to find one, but the search continues… 

Nor does it appear that humans will try to build one any time soon as an answer to our energy problems. It is estimated if we, say, dismantled Mercury and replaced it with a Dyson Sphere; we’d need about 120 trillion years to complete the project!

So how does this apply to hollow planets? 

How the Dyson Sphere Theory Applies to Hollow Planets

When Dyson was working through his thought experiment, he came up with a formula that would determine the amount of force required for a planet to be able to overcome the gravitational forces that solidify planets. In short, what would it take for a forming planet to not require a core and thus be hollow?

The formula is:

(GM/2r)p= F/A=S

G = Newton’s gravitational constant

M= Mass of a star’s interior
r = the shell’s radius

p = shell’s density (rho)

Using this, Medium and others in the scientific community took the number 57 peda Pascal’s. This number is considered a conservative estimate for what force would be needed on every square meter of the hollow planet’s shell.

If you plug 57 peda Pascal’s into the formula, the result is a number that goes beyond the maximum strength of matter. There isn’t matter in existence that can withstand the forces required for a planet to be hollow.

Conclusion

Throughout humanity, the idea of a hollow Earth has been popular. This has led many to wonder if a hollow planet is possible. But from scientific evidence, this appears to be impossible.

The way planets are made requires an incredible amount of gravitational force. Without the gravitational force, a planet wouldn’t be a planet. Yet, the gravitational force a hollow planet’s shell would be required to withstand exceeds the capabilities of matter. 

More About Planets…

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