Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: Sam Brown on 25/10/2018 14:13:35
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Carole has asked:
"I recently heard that the Earth's core is believed to be made up of plasma. Is this correct and how do we know this?"
What do you think?
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Carole has asked:
"I recently heard that the Earth's core is believed to be made up of plasma. Is this correct and how do we know this?"
What do you think?
The earths core has long been known to be a solid LMGTFY https://en.wikipedia.org/wiki/Inner_core
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The center of the Earth is extremely hot - roughly the same temperature as the visible surface of the Sun.
It is made of dense elements, including iron and nickel. It is expected to be very similar in composition to iron meteorites.
The Earth's core is under immense pressure from the rocks above it, which turns it into a solid. We can tell this from the behavior of different types of earthquake waves. Some types of earthquake waves will travel through a solid which won't propagate through a liquid, a gas or a plasma.
See: https://en.wikipedia.org/wiki/Inner_core
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the Earth's core is believed to be made up of plasma
The Sun is made up of Hydrogen and Helium (plus trace amounts of other elements).
- At around 5,500C, the temperature of the Sun's visible surface is hot enough to rip apart hydrogen molecules, and rip off all the electrons from about 3% of the Hydrogen and Helium atoms, forming a boiling broth of:
- positive protons, alpha particles and He+ ions
- mixed with negative electrons and H- ions
- Amongst a majority of neutral H and He atoms
- 3% ionisation is enough to form a plasma
- This plasma is extremely conductive, quite unlike Hydrogen and Helium at room temperature.
- Neutral H/He atoms and H- ions are short-lived, since electrons continually jump around during collisions at these temperatures.
See: https://en.wikipedia.org/wiki/Sun#Photosphere
The Earth's core is made up of Iron and Nickel and other heavy elements.
- At around 5,500C, at the temperature of the Earth's core, the outer electrons of Iron and Nickel forming a mobile sea of electrons which can float freely between atoms: a metal
- However, this temperature is not hot enough to dislodge the inner electrons of Iron and Nickel, so the atom is still recognizable as a unit, and takes up far more volume than just an Iron or Nickel nucleus.
- Under the immense pressure of the inner core, these atoms are forced together into fixed positions of a crystal: a solid metal.
- This solid, conductive metal is not greatly different from Iron and Nickel at room temperature - just a lot hotter and denser.
- Under the slightly lower pressures of the outer core, the atoms of Iron and Nickel are not jammed so closely together, and they are able to move around past each other: a liquid metal.
See: https://en.wikipedia.org/wiki/Inner_core#Temperature_and_pressure
So although the Earth's inner core is at similar temperature to the surface of the Sun, the Sun is a plasma, and the Earth's inner core is a solid metal. This is mainly due to the different chemical composition.