We know that our earth's core is made up of iron-nickel alloy, and it is spinning to create magnetic flux all around our planet to create our life-saving Magnetosphere. And this also influences our 9.8 m/s gravitational force, I think. So what if Earth's core (both inner-solid and outer-liquid) was made up of copper or any other metals? How would the magnetosphere and gravitational force differ from ours?

  • $\begingroup$ This question might be better suited to either SE World Building or SE Physics $\endgroup$
    – Fred
    Oct 24, 2019 at 11:27
  • $\begingroup$ I don't see the point of fanciful 'what if?' questions about imaginary worlds. I think questions should be about the real world we find ourselves in, not about some other world which we would prefer, or imagine in our dreams. $\endgroup$ Oct 24, 2019 at 12:38
  • 1
    $\begingroup$ What if the Earth's rotation speeded up one hundred-fold, how would that affect our daily lives? $\endgroup$ Oct 24, 2019 at 13:23
  • $\begingroup$ I'm imagining uranium. $\endgroup$
    – Spencer
    Oct 23 at 0:23

3 Answers 3


On a quick approach:

  • Magnetism. The copper itself have a weak magnetism, so a copper core will not create a magnetosphere. Chek here or here.
  • Gravity. The Iron density is 7.874 g/cm³ and the nickel density is 8.908 g/cm³. Copper density is 8.96 g/cm³. So with those density data, the core will be heavier. (The actual core is supposed to have a 9.9-12 g/cm³ density) It is supposed that this additional mass will increase the gravity. What it is not well determine is the % of iron and nickel at the core, so, we can talk on probably a raising on between 5-15% the actual gravity force.

Regarding some other metals, it will depends on magnetism and density.

Hope it helps!

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    $\begingroup$ That's not quite correct. It's not the iron's magnetism that creates the earth magnetic field, but rather the electric currents that are flowing in the liquid iron. These would also be flowing in liquid copper. $\endgroup$ Oct 24, 2019 at 20:27
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    $\begingroup$ Iron's Curie temperature, at which it loses its ferromagnetic properties, is 1043 K. Earth's core temperature is around 6000 K. So unless the Curie temperature increases considerably with pressure, the core magnetism is not due to iron's ferromagnetism. $\endgroup$
    – jamesqf
    Oct 25, 2019 at 4:56
  • $\begingroup$ It is not the iron's magnetism, for sure, is the motion generated by the core flows. Copper can not create it. Un the Curie temperature is related with the pressure $\endgroup$ Oct 25, 2019 at 5:15
  • $\begingroup$ @Fred: But that's at around room temperature, and in solid materials. Liquids at high temperatures might well behave differently. $\endgroup$
    – jamesqf
    Oct 25, 2019 at 17:27

As explained in some comments, it is the dynamo effect from the flow of liquid metal that creates the magnetic field, not the magnetic properties the solid metal might reveal under surface conditions. In fact, the liquid does not even need to be a metal; it can be any electrical conductor such as water containing dissolved salts. On smaller objects that cannot support a metallic core, a (weak) magnetic field could be generated by a subterranean water-based solution, as on Jupiter's moon Ganymede:

Computer models show Ganymede might have ice and oceans stacked up in several layers like a club sandwich. Scientists first suspected Ganymede had an underground ocean in the 1970s. The Galileo spacecraft discovered Ganymede's magnetic field in 1996, providing evidence to support the theory.

NASA’s Hubble Space Telescope has found more evidence for an underground saltwater ocean, and evidence of a thin oxygen atmosphere on Ganymede.

Where we have a liquid metal core, one metal is more or less as electrically conductive and as fluid as another, so any molten metal would be capable of generating the necessary dynamo effect.

However, there is one subtlety. Under ambient pressure copper melts several hundred degrees Celsius lower than iron or nickel, or any of their alloys (alloying does not markedly depress the melting point with iron and nickel). If such a difference were to persist to Earth-core pressures, a copper-based core might solidify more extensively and leave less fluid for dynamo generation.

In the end, however, it is iron and nickel that are the most common metals likely to get into the core, in terms of both element generation and chemistry (copper is usually considered chalcophile, tending to form sulfides in the crust/mantle), so the mostly fluid iron-nickel core with a strong dynamo effect is what we have.


So, you are asking what our Magnetosphere would be like if the Earth's core was composed of something different than our current composition, and if it was copper, what effects would that have on it and the gravitational forces as well. To answer there are 3 things that are most likely the most prevalent qualities of the Magnetosphere and core of Earth.

  1. Consider that our current composition of inner and outer core is what allows our magnetosphere to be the most powerful electromagnetic field of any rocky celestial body in the known universe.
  2. the magnetosphere acts as a shield, protecting our planet from harmful solar radiation and charged particles
  3. it is generated by the movement of molten iron in the Earth's outer core, which creates a dynamo effect that generates the magnetic field.

-To logic out the most possible answer based on these considerations:

  1. If the Earth's core was composed of a different material, such as copper, it is likely that the magnetic field would be weaker or non-existent.

  2. Copper is not a magnetic material, so it cannot generate a magnetic field. Therefore, if our core was made of copper, it is likely that our planet would not have a magnetosphere at all, or it would be much weaker than it currently is.

-About Gravity-

The gravitational forces on Earth would also be affected by a change in core composition because the strength of gravity is determined by the mass of an object, so if the Earth's core was made of a lighter or heavier material than iron, it would affect the planet's overall mass and therefore its gravitational force. However, it is difficult to predict exactly how this would affect the planet's gravity without more specific information about the new core composition.

In summary, the current composition of Earth's core is crucial for generating our magnetosphere and protecting life on our planet. If the core was composed of a different material, such as copper, it is likely that our magnetosphere would be weaker or non-existent, and this would have significant implications for life on Earth. Since the planets of our solar system formed around the same time, and considering the current condition of Mars and Mercury, one can assume atmospheric death by this point in our timeline. We literally have the perfect conditions for life to exist and life only exists due to the ELectromagnetic Fields of this planet. It is akin to God in all honesty, for without them, life would have to develop its own or be wiped off the face of earth.

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    $\begingroup$ In the generally accepted model iron doesn't create the Earth's magnetic field because it is intrinsiclly magnetic but because of, as you say, a dynamo effect. As all this requires is a conductive fluid I don't think it follows that a copper core couldn't support an equivalent magnetic field. $\endgroup$ Oct 14 at 11:12

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