Does our moon affect Earth's core

[Kurious12]

I read that Mars core cooled a long time ago because the planet was small, and Venus's core cooled because of its slow rotation. Does our moon have any affect at all on the Earth's core? Could the size of our moon play a role in keeping the core hot? 

[TheVat]

Good question.  One way to think about it is to consider the size of the body generating tidal stress on another.  With Jovian moon Io, where gigantic Jupiter is generating the tidal force, the heating effect is pretty dramatic.  But Earth does not cause the moon's core to heat significantly, so it seems pretty likely that the moon, smaller than Earth, would not generate enough tidal stress on Earth to heat its core.  The heat in Earth's molten center is from a different source, which you may have also heard about.

[Genady]

As TheVat says, it is unlikely that the Moon heats the Earth's core. However, it can have other, namely mechanical effects on it. For example, since the core is liquid and inhomogeneous, the Moon might affect movements in it, which in turn might cause changes in the Earth's geomagnetic and gravitational fields.

[Moontanman]

1 hour ago, TheVat said:

Good question.  One way to think about it is to consider the size of the body generating tidal stress on another.  With Jovian moon Io, where gigantic Jupiter is generating the tidal force, the heating effect is pretty dramatic.  But Earth does not cause the moon's core to heat significantly, so it seems pretty likely that the moon, smaller than Earth, would not generate enough tidal stress on Earth to heat its core.  The heat in Earth's molten center is from a different source, which you may have also heard about.

I'm going to have to disagree, the Earth rotating as the Moons tidal effects slow down Earth's rotation has to result in some heat. Not as much as other sources but it has to be a significant source of heat/friction. 

[Genady]

11 minutes ago, Moontanman said:

I'm going to have to disagree, the Earth rotating as the Moons tidal effects slow down Earth's rotation has to result in some heat. Not as much as other sources but it has to be a significant source of heat/friction. 

Wouldn't this heat be generated in the crust rather than in the core? 

[studiot]

It should be possible to make a reasonable estimate of the loss of rotational kinetic energy, which as Moon says, must be degraded to heat.

It has been possible to detect 'earth tides' in the crust, but the deflections are tiny compared to the deflections of the water covering (oceans) and energy depends upon the square of the deflection amplitude.

So deflection of the liquids in the outer core will also be greater than those in the more solid crust and mantle and of course the inner core.

The outer core will generate much friction as it rubs between the undermantle and the inner core.

We now have believable models of the (rate of) heat transfer between the various layer of the Earth that can be applied.

[swansont]

1 hour ago, studiot said:

It has been possible to detect 'earth tides' in the crust, but the deflections are tiny compared to the deflections of the water covering (oceans)

They’re a good fraction of meter

https://en.wikipedia.org/wiki/Earth_tide

[beecee]

4 hours ago, Genady said:

Wouldn't this heat be generated in the crust rather than in the core? 

I go along with that and I believe the tides and tidal interactions support it.(1) The Moon,(and the Sun to a lesser extent) attract the waters closer to it. (2) It then attracts/pulls the Earth towards it, to a lesser degree. (3) And to an even lesser extent, the waters on the opposite side.(4) The movements of the tides, create a friction on the Earth's crust, and the tides being "slightlÿ ahead" of the overhead Moon, pulls the Moon into ever increasing higher orbits at around a couple of cms per year.

Edited May 2, 2022 by beecee

[studiot]

9 hours ago, swansont said:

They’re a good fraction of meter

https://en.wikipedia.org/wiki/Earth_tide

I suppose they both depend where you live.

We have 30 metre sea tides where I live.

[StringJunky]

57 minutes ago, studiot said:

I suppose they both depend where you live.

We have 30 metre sea tides where I live.

Is it down to the degree of incline of the landmass edge that dictates tide height i.e  steeper inclines causes higher tide heights?

[swansont]

1 hour ago, studiot said:

I suppose they both depend where you live.

We have 30 metre sea tides where I live.

Which is atypical and I'm betting that's not out on the ocean. 

[studiot]

3 hours ago, swansont said:

Which is atypical and I'm betting that's not out on the ocean. 

You chose to quote the vertical deflection, yet the horizontal deflection can be from a few to hundreds of kilometres.

People always forget tidal streams.

[swansont]

Just now, studiot said:

You chose to quote the vertical deflection, yet the horizontal deflection can be from a few to hundreds of kilometres.

People always forget tidal streams.

Tidal streams are not out on the ocean, which is what you originally referenced.  

[studiot]

6 minutes ago, swansont said:

Tidal streams are not out on the ocean, which is what you originally referenced.  

Of course they are, that is how the water body moves up and down to support the vertical  movement of the water/air interface.

Of course they are not the only source of water movement.

[Airbrush]

I still don't see how the moon could affect Earth's liquid core significantly.  It could 3 billion years ago, because it was so close to Earth.  The liquid core has been insulated from any moon/Earth-crust friction for a long time now.  Or am I wrong?

Edited May 3, 2022 by Airbrush

[Kurious12]

Lots of good answers here, I've learned something from all of them. One of the reasons I was curious about this is because of what was found when we got a close up look at Pluto, it was thought to be a very cold and dead planet because of its distance from the sun, but that turned out to be very wrong. Something is pumping a bit of heat into the planet, and I would bet it has something to do with its relationship with its oversized moon.

[studiot]

A good place to start looking for information is this book   -  700 + pages of wisdom.
Chapter 2 is dedicated to your tidal question.

 

[beecee]

How's this for tidal effects....

https://en.wikipedia.org/wiki/Horizontal_Falls

The Horizontal Falls, or Horizontal Waterfalls, nicknamed the "Horries" and known as Garaanngaddim to the local Indigenous people, are an unusual natural phenomenon on the coast of the Kimberley region in Western Australia, where tidal flows cause waterfalls on the ebb and flow of each tide. The Lalang-garram / Horizontal Falls Marine Park is a protected area covering the falls and wider area.

[studiot]

6 hours ago, beecee said:

The Horizontal Falls, or Horizontal Waterfalls, nicknamed the "Horries" and known as Garaanngaddim to the local Indigenous people, are an unusual natural phenomenon on the coast of the Kimberley region in Western Australia, where tidal flows cause waterfalls on the ebb and flow of each tide. The Lalang-garram / Horizontal Falls Marine Park is a protected area covering the falls and wider area.

Thanks beecee, nice one.  +1

Do you know if the 'waterfall' is the result of a step in the bed or is just in the water, looks like a bit like hydraulic jump to me.

In fact it seems to be more like the effect you get pouring a bucket of water into a bath of water.

https://parks.dpaw.wa.gov.au/park/lalang-garram-horizontal-falls

Edited May 4, 2022 by studiot

[beecee]

11 hours ago, studiot said:

Thanks beecee, nice one.  +1

Do you know if the 'waterfall' is the result of a step in the bed or is just in the water, looks like a bit like hydraulic jump to me.

I am pretty sure that it is simply an effect caused by the narrow gorge opening.

https://kimberley-australia.com/kimberley-attractions/horizontal-falls/

Although they are called waterfalls, this natural phenomenon actually consists of intense tidal currents hurtling through two narrow coastal gorges. Massive tidal movements create a waterfall effect as water banks up against one side of the narrow cliff passage, to be repeated again on the turning tide.

The twin gaps are part of the McLarty Ranges, which have two ridges running parallel approximately 300 metres apart. The first and most seaward gap is about 20 metres wide and the second, most spectacular, gap is about 10 metres wide.

It is possible to drive boats through the two gaps to the bay behind. The tides in this area have a 10 metre variation which occurs over six and a half hours from low tide to high tide and vice versa. The effect of the waterfalls is created by the tide building up in front of the gaps faster than it can flow through them and there can be a four metre high waterfall between the bays.

[Airbrush]

When the moon first formed it was much closer to Earth.  It had HUGE tidal force on Earth's core.  Could the moon have cranked the Earth's liquid core, like kick starting a motorcycle?  Maybe because of the moon our liquid core was pushed and pulled by the moon over millions of years, before moving so far away as to not have much affect.  Earth's liquid core was supercharged at the start, and that is why we are still protected by a strong-enough magnetic field?

Edited May 6, 2022 by Airbrush

[Kurious12]

On 5/6/2022 at 2:28 PM, Airbrush said:

When the moon first formed it was much closer to Earth.  It had HUGE tidal force on Earth's core.  Could the moon have cranked the Earth's liquid core, like kick starting a motorcycle?  Maybe because of the moon our liquid core was pushed and pulled by the moon over millions of years, before moving so far away as to not have much affect.  Earth's liquid core was supercharged at the start, and that is why we are still protected by a strong-enough magnetic field?

For what it's worth, I do believe that this could be right. You know, I never really gave much thought about when the moon was a lot closer to Earth but I think you're on to something here. 

[Schlagzilla31]

On 5/1/2022 at 4:06 PM, TheVat said:

Good question.  One way to think about it is to consider the size of the body generating tidal stress on another.  With Jovian moon Io, where gigantic Jupiter is generating the tidal force, the heating effect is pretty dramatic.  But Earth does not cause the moon's core to heat significantly, so it seems pretty likely that the moon, smaller than Earth, would not generate enough tidal stress on Earth to heat its core.  The heat in Earth's molten center is from a different source, which you may have also heard about.

The thing that you're not considering... that NO-ONE'S considering is that the Moon is tidally locked. Since the same side of the Moon always faces the Earth, we'd never see tidal friction caused by a "rotating" body.

 

I've only ever heard one scientist talk about it in a way that made sense. He stated that if Mars had a moon that was at least 10% of it's diameter, Mars would still support life.

[Phi for All]

40 minutes ago, Schlagzilla31 said:

The thing that you're not considering... that NO-ONE'S considering is that the Moon is tidally locked. Since the same side of the Moon always faces the Earth, we'd never see tidal friction caused by a "rotating" body.

I think it was assumed in all the mentions of tidal interactions.

[Moontanman]

Doesn't there need to be a third body involved for tidal heating to work? Io is hot due to the effects of the other galilean moons and Jupiter not because Io is orbiting Jupiter or do I have this completely wrong?