Eli5: How do we know that the Hollow earth theory is false if we have never been in the center of the planet?
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We have a lot of data from which we can infer that the Earth isn’t hollow. For example, from observing the gravitational interactions between the Earth, the Moon and the Sun we know the mass of the planet. And Earth has a lot of mass which has to be somewhere. Another example: seismic waves from earthquakes go through the entire volume of Earth, and we can record and study those waves and figure out what’s inside it, the same way medics use ultrasound to see inside the human body without cutting it open. If there was a massive cavity inside Earth, you wouldn’t be able to miss it in the seismic record, but it’s just not there. Another example is the observation of temperature – we know how much heat we get from the Sun and how much heat the planet’s surface sheds into space, and there is an imbalance which can only be covered by the heat coming up from inside the planet. And for there to be that much heat the planet has to be not hollow.
All that is just off the top of my head, I’m sure there are more examples. In the end the hollow Earth theory can not explain most of our actual observations about the planet, and is thus not a valid theory.
Same way as you can tell a bell IS hollow, you bang hard on one side and see what happens on the other side. In the case of the earth, many things from nuclear testing, volcanoes and even seismic vibrations are strong enough to hear after they pass through the Earth. You can calculate the average density of the material by seeing how long the vibrations take to cross the distance. Taking different angles and slices to compare let’s you map out the various densities of layers.
The centre of the Earth is molten, we have attempted to drill down deep but the technology will only let us get down a relatively short way and it is extremely expensive to drill down.
Lots of observational evidence:
* We have ground penetrating radar that can show what different parts of the earth interior looks like
* We have a magnetic field, which could only exist if there was a metallic core in the center of the planet
* Subduction and movement of tectonic plates only works if there are thermal convection currents from a molten core and hot mantle
* A hollow earth would lack the mass to have the gravitational field we all live in every day
Compare that to the complete lack of evidence the earth is hollow and it’s a pretty compelling story. It’s a falsehood that “If I can’t see it, I don’t know if exists”
We don’t, we can only make inferences based on evidence, and the amount of supporting evidence needs to be enough that the scientific community as a whole generally accepts the theory. In this case there is a lot of valid, accurate, and reliable data that proves the current theory.
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