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If some kind of insane wizard began a ritual that would turn the inner core of the earth into gold, what would happen?

Over the course of 15 days, the entirety of the core will become gold.

Each individual atom will spontaneously gain the amount of protons, neutrons, and electrons to be a stable isotope of gold. Each atom will be selected at random, and approximately equal periods of time will pass between each selection.

Obviously, this will cause the core of the earth to become more massive, and may have a very large effect on the earth's magnetic field.

Since gold is denser than both iron and nickel, this will make the core more massive.

Given all this, how long will it be before...

  1. It is noticed that something is amiss in the core

  2. The effects have a significant detrimental effect on our lives

  3. Humans start to die

  4. Humans are wiped out

  5. Total annihilation of pretty much all life on earth

Some of those might not actually happen as a result of this. It's not my area of expertise.

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    $\begingroup$ Since gold is denser than both iron and nickel, I presume the core will also expand. I expect the opposite to happen. $\endgroup$ – Renan Feb 7 '18 at 18:07
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    $\begingroup$ You might want to ask a similar question about converting the inner core to gold, but instead of assuming that the inner core becomes more massive, assume that the mass of the inner core remains the same. This would cause the inner core to shrink. $\endgroup$ – Jasper Feb 7 '18 at 18:31
  • $\begingroup$ Are you sure you need hard science on this? $\endgroup$ – Mołot Feb 7 '18 at 18:57
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    $\begingroup$ science-based is for what you just described. Hard science is for situations when you need actual scientific papers on the topic, exact calculations etc. $\endgroup$ – Mołot Feb 7 '18 at 19:00
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    $\begingroup$ I'm pretty sure what will happen is humans will rip the secret of non-conservation of mass out of physics and abuse it for star travel. $\endgroup$ – Joshua Feb 7 '18 at 22:16
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CORRECTION: There won't be quick catastrophe.

If the transmutation effect is limited to the inner core, gravitational and volumetric effects would be relatively modest. While most pictures of Earth's inner structure lead us to believe that inner and outer core are two comparable regions, volume- and mass- wise they are quite different. Inner core constitutes only 1.7% of Earth's mass and about 1% of Earth's volume (compared to outer core's 30.8% mass and 15% volume).

If every atom in the Earth's inner core is replaced with gold, its weight would increase substantially. Standard atomic weight of Gold is 196.966569. Standard atomic weight of atoms in Earth's core is 50.4 (total core, but we assume that core's composition is uniform). We are looking towards an increase by 3.9 times of Earth's inner core mass. The fraction of Earth's core mass (core/total) is about 1.7%, so the total mass of the Earth is set to increase by about 4.9%. This would increase the force of the gravity on Earth's surface by approximately the same amount. Increased gravity alone will cause significant destruction and mass extinction of species, but should not pose significant risk to the entire biosphere, and human civilization should be able to adjust.

Additional potentially destructive factor would be explosive increase of Earth's inner core size. Although I can not provide exact calculations for the density, let's consider that atomic radius of gold is 14% greater than atomic radius of iron. Considering small size of inner core, this should not be enough to rip Earth's crust apart, but may result in a period of increased seismic and volcanic activity.

An increase of Earth's gravity will pull the Moon from its orbit and cause it to shift to an elliptical orbit around Earth. 5% increase in Earth's gravitational pull would not be enough to cause a collision, though.

Contrary to popular beliefs, Earth's magnetic field might not be affected at all be switching to a non-magnetic inner core. According to the Dynamo theory, Earth's magnetic field is explained by the convection in outer core. All that is needed from the inner core is that it should be hot.

And now the timeline:

  1. It is noticed that something is amiss in the core - Almost instantly all high-precision instruments will go awry because of the change of gravity;

  2. The effects have a significant detrimental effect on our lives - In 1week there will be substantial increase in seismic activity. Increased weight will become noticeable to regular people;

  3. Humans start to die - The same first 1 week. After the earthquakes start, they will only get worse.

  4. Humans are wiped out - Probably never, at least never because of this event. Civilization will adjust to the new gravity and live through the volcanic period.

  5. Total annihilation of pretty much all life on earth - Transmutation effect of this scale should not affect life on Earth in general.

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    $\begingroup$ "Weight, weight !", shouts the wizard. "Earth is transmuted by weight, not volume! The mass stays the same! Earth shrinks a little bit, maybe. So everyone is OK?" $\endgroup$ – Willk Feb 7 '18 at 20:32
  • $\begingroup$ I wonder how the very distribution of inner (solid) to outer (liquid) core would change. On the one hand, gold has a lower melting point so that might shrink the core; on the other, the increased gravity would cause more of the outer core to solidify and become inner core. $\endgroup$ – Kevin Feb 7 '18 at 23:19
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    $\begingroup$ Citation needed: 4.9% increase in gravity "will cause significant destruction and mass extinction of species". While it will have some effect, particularly on animals which fly, I find it hard to believe that it would cause "mass extinction of species", or even "significant destruction". As to the "significant destruction", most structures, natural and man-made, should be able to withstand a 5% weight increase. It's likely that there will be some which have problems, but I think you're significantly overstating the case. $\endgroup$ – Makyen Feb 8 '18 at 0:14
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    $\begingroup$ As a quick estimate of the effect of 5% increase in gravity, you can look at the effect of drag through air. The drag force can be rewritten as F=mg(v/V)^2 where V is the terminal velocity. For a human, this is 122mph. A little math will show that ~27mph winds induce the same force as a 5% shift in gravity. I would say that this is significant for flying animals, but land animals probably don't care. $\endgroup$ – aidan.plenert.macdonald Feb 8 '18 at 0:44
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    $\begingroup$ @Alexander The question isn't if it will affect things, but how much. Bugs, birds, yes, I'll agree. I made a simple calculation above. But rocks and mountains?! I'd need to see math. $\endgroup$ – aidan.plenert.macdonald Feb 8 '18 at 0:46
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Volume changes

The changes in the Earth's volume will largely depend on the crystalline or liquid structure of the materials in the core. The density of iron is 7.8 g/cm$^3$, and its atomic mass is 55.8 g/mol. Thus, a mol of iron will occupy 7.1 cm$^3$ at room temperature. Gold on the other hand has a density of 19.3 g/cm$^3$, and its atomic mass is 197.0 g/mol. A mol of gold will occupy 10.2 cm$^3$.

Now density of iron in the Earth's core is much higher, almost twice as high. I was unable to find any estimates for gold's density at conditions remotely close to those at the center of the Earth (~6000 K, ~300 GPa). So we are left with estimates from standard temperature and pressure. So we can tentatively assume that the transformation to gold will cause the Earth's core to expand.

If we assume at 10.2:7.1 volume ratio (ignoring the nickel component, for simplicity), then the inner core will ultimately increase its volume about 44%. Since the Inner core is about 1220 km in radius; we expect the rest of the Earth to expand by about 7 km in radius to accomodate the volume change, or about 0.1 %.

The circumference of the Earth will increase by about 45 kilometers. Given that continents are arranged in plates, I would assume that the most likely place for cracks to appear is at the plate boundaries. For such a massive increase in circumference, the plate boundaries would each be looking at chasms down to the mantle forming, in the order of tens of kilometers wide.

Mass changes

Since we know the differences in atomic mass, and since each individual atom is changing, we can know for certain the difference in mass. The inner core is actually not that massive, about 2 % of the Earth's total. Gold is more massive than iron (ignoring the nickel component, again) by a ratio of 197:56; so the inner core will increase in mass by a factor of 3.5; the increase in the inner core's mass will add 7% to the mass of the Earth.

Surface gravity ($\hat{g}$) is expressed as:

$$\hat{g} = \frac{4}{3}\pi G\rho r.$$

As shown above, mass increases by a factor of 1.070 and radius by 1.024. Volume of the planet will increase by the cube of radius, or 1.075. Since density is mass over volume, the overall change in surface gravity will be

$$\frac{1.070}{1.003}\cdot1.001 = 1.067.$$

So, the increase in surface gravity will not be very significant; given that this happens over 15 days, there will be an increase of 0.00018$g$ per day. Scientific instruments would detect this, but the bearing on our everyday lives will be pretty paltry compared to the km wide, mantle deep chasms opening on the crust.

How soon will changes happen?

The 9.0 Tohoku earthquake (and the Fukushima tsunami that came with it) involved a fault slip of 20-30 meters at the epicenter. Let us assume that a circumference of the Earth runs through 5 different plate boundaries, so the delta of circumference is divided 5 ways. This means that a ~125 meter increase in the Earth's circumference will cause all 10 of those plate boundaries to undergo some sort of earthquake-like energy release, of about the magnitude of a 9.0 earthquake.

If it takes 15 days for the circumference to increase by 45 km, then 125 meters will take one hour. Catastrophic earthquakes will begin soon after the increase begins.

Mantle pressure changes

In the short term, the expansion of the inner core will be felt through the rest of the planet as pressure waves. While the Earth will want to split its crust apart, trillions of tons of continental rock isn't just as easy to move as all that. Pressure will build up in the liquid mantle. The speed of these waves will vary with varying viscosity and density, but will probably average around 10 km/s in the outer core and mantle. At this rate it will take around 8-10 minutes for the pressure waves to propagate all the way to the crust.

When a pressure wave approaches the crust, the increase in pressure will probably cause anything remotely volcanic to erupt. I can't begin to quantify how quickly this will happen. And I can't begin to quantify the results. Some volcanoes

will be eruptive, and others effusive. Some volcanoes that have a lot of pent up energy may be induced to go off with the force of a Tambora.

The fate of the oceans

Lets say the crust is 35 km thick, on average. Lets also say that every plate boundary opens up to 5 km in width. There are about 260,000 km of plate boundaries. If Each boundary opens up to be 5 km wide and 35 km deep, the volume of these new 'pits' is about 36 million km$^3$. The volume of the oceans is about 1.3 billion km$^3$, so we can see that there will be plenty of oceans left.

There will obviously be a lot of boiling happening, but I'm really straining to work the physics of this situation. I'm not going to post too much, for fear of being wrong, but I believe that there will not be significant steam formation, due to rapid cooling and relatively low conductivity of the aesthenosphere, and high pressure of ocean water. Ultimately, the oceans will heat, but won't boil off. What these oceanic-ly cooled cold spots in the mantle do is probably really important, but I can't begin to estimate. I'm sure it won't be good.

Conclusion - what will happen

The effect of increased mass is negligible compared to the effects of increased volume. The volume will increase at a fast rate. The effects of this change will be broadcast to the surface by pressure waves in about 10 minutes. Within the hour minutes more, I estimate that every plate boundary on the planet will have the potential to release the equivalent energy of a magnitude 9 earthquake with its epicenter at every single point on the plate boundaries.

While the earthquakes begin, most if not all volcanic hot spots on Earth will erupt. Direct fatalities from ash will be few, but the ash deposition in the skies will be at least as bad as nuclear winter, and possibly orders of magnitude worse.

The seismic and volcanic activity will continue for 15 days continuously. The stresses of the expanding mantle on the underside of the plates will probably start tearing them apart too; more earthquakes. No structure or tree will be left standing. I don't know the effect of being vibrated for 15 days straight, but that by itself sounds like enough to extinguish most higher life forms. Ash will block out the sun; it will be one or more orders of magnitude darker for decades.

Bad day at the office.

To answer your questions specifically.

  • It is noticed that something is amiss in the core: The pressure wave from inner core expansion will take about 10 minutes to reach the surface. The gravity changes in these first 10 minutes will be so slight that it is doubtful anyone would notice. Anyone with sensitive gravimetric equipment would not have the first reaction of, "Whoa, maybe the core turned to gold!"

  • The effects have a significant detrimental effect on our lives: Within an hour of noticing the first tremors, people will start feeling catastrophic earthquakes.

  • Humans start to die: The earthquakes and volcanoes will start the process. Few structures would be able to withstand more than an hour of this violent shaking. People in structures will die, by the billions.

  • Humans are wiped out: For however many people survive the first 15 days, the blocked out sun will extinguish whatever plant life remains pretty quickly. We enter your standard post-apocalyptic scenario, with the difference that very few plants will grow and there are no longer any oceans to speak of.

  • Total annihilation of pretty much all life on earth: It is doubtful that this will happen. There are lots of bacteria and they can be pretty hardy.

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    $\begingroup$ 13% difference in volume is not 13% difference in radius. $\endgroup$ – Alexander Feb 7 '18 at 21:35
  • $\begingroup$ Ok then, "(and the rest of the Earth) to expand by about 155 km in radius" - increase at the core would not translate linearly to the surface. Core volume may increase by 44%, but total Earth volume would increase by less than 1% $\endgroup$ – Alexander Feb 7 '18 at 21:42
  • $\begingroup$ @kingledion Why does the radius increase? Gold is denser than iron or nickel. $\endgroup$ – Piomicron Feb 7 '18 at 21:49
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    $\begingroup$ @kingledion - I have to stress that 155 km radius increase at the core would not give 155 km increase at the surface. If you drop 2 cm apricot kernel to 1 liter jar of water, do you expect water level to rise by 2 cm? $\endgroup$ – Alexander Feb 7 '18 at 21:54
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    $\begingroup$ It's good that this answer at least addresses volume effects, which the other answers woefully ignore. There is a second volume effect, though, that might mitigate some of the expansion problems: Stronger gravity at the core's surface area will lead to more pressure in the core and the surrounding material, thus compressing the whole thing more, leading to stronger gravity, and thus even more compression. Thus, you won't see the full added core volume as added volume to the entire earth. $\endgroup$ – cmaster Feb 7 '18 at 22:17
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The reason that the earth has a thick atmosphere, while Mars has a very thin atmosphere, is that the earth has a strong magnetic core that deflects solar wind, while Mars doesn't have a magnetic core. Mars has sufficient mass to attract an atmosphere capable of supporting human life, but the solar wind, unimpeded by a magnetic core, blows most of it away.

Converting the earth's iron core to a non ferrous metal like gold would result in the loss of the magnetic core and subsequently, the loss of most of its atmosphere. Most life on earth would die, certainly all of the more advanced life.

How long would that take? You'd need an extensive background in physics to answer that. Still, the most serious ramification of losing the earth's magnetic core would be the loss of most of its atmosphere.

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  • $\begingroup$ It should be noted though that the atmosphere loss because of that reason is purely speculative at this point. If the op chooses to go with it (and replace more iron/nickel, see top answer, to have it matter), it might be proven wrong in the future. $\endgroup$ – Raditz_35 Feb 8 '18 at 8:25
  • $\begingroup$ According to Alexander, the magnetic core thing wouldn't actually happen, as it's only the inner core. $\endgroup$ – Piomicron Feb 8 '18 at 8:30
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1. It is noticed that something is amiss - in a day or two.
Gold atom is almost 4 times heavier than an iron atom, replacing iron with gold will result in substantial increase in gravity. People will notice different weight when they stand on the scales, elevators and airplanes will not be able to carry as much weight as before, some flimsy structures will begin collapsing.

Once it is established that same thing is happening all over the earth, people will figure it out that it's the core.

2. The effects have a significant detrimental effect on our lives - first few days transmutation. Even if core is half the mass of the planet, quadrupling its mass will double the gravity. Walking will be hard since you effectively carry a second person on your shoulders.

I would also expect all sorts of landslides, dams bursting, rivers flowing faster and eroding the shores.

Loss of magnetic field will render most electronics and radio useless. It will also increase radiation, but in the short term it will mostly lead to sunburns. You can look at the movie Core (2003) for Hollywood take on loss of EM field and shield.

3. Humans start to die - by end of transmutation The biggest effect will be massive earthquakes and volcano eruptions. Liquid gold will have different volume than liquid iron. If my amateurish computations are correct, gold will have more volume (it also makes sense given a larger atom), so Earth will inflate from inside, its crust would crack, and the tectonic plates will float in ocean of magma. Oceans will likely flow over the edge and boil off, there would be huge emissions of unfriendly gasses into atmosphere.

All life near the edges of the tectonic plates will be lost very soon. Life in the middle might last a few days more.

I hope your wizard can open a portal to a new dimension, or a magical bubble on another planet.

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  • $\begingroup$ Your estimate of the size of the core is wrong. The inner core is only 1.7% so your second point is based on an incorrect assumption. $\endgroup$ – Anketam Feb 8 '18 at 18:10

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