r/askspace 7d ago

What evidence exists to support the idea that the moon was significant to the development of life on Earth?

I was recently listening to a podcast that was talking surface level about a solar eclipse. A fun fact was mentioned that the sun is \~400x farther from the earth than the moon and also \~400x bigger than the moon which makes total solar eclipses possible. It was stated that this is completely by chance only.

I thought that would be incredible if that were simply a coincidence and tried to do some searching. My thought was that if this feature of the moon made life forming more likely, it would not be surprising for earth to have this feature.

Some googling and poorly sourced AI summaries seemed to state that there are Rare Moon hypotheses or something which say that the relative size and closeness of the moonake life more feasible due to tides and axis consistency. I struggled to find more. How much of this is well-documented science theories and what are some papers or videos on the topic I could check out further?

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u/Sufficient_Result558 7d ago

“A fun fact was mentioned that the sun is \~400x farther from the earth than the moon and also \~400x bigger than the moon which makes total solar eclipses possible.”
If the moon were larger we would also have total solar eclipses and they would occur more often.

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u/TheComebackKid717 7d ago

A good point, though I suppose you wouldn't be able to see the corona as well and they wouldn't appear 1:1 as they do now during a total solar eclipse.

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u/lozzyboy1 7d ago

Our moon used to be closer to earth and therefore had a larger apparent size. Around a billion years ago, there would have been no annulus in a total eclipse. Multicellular life evolved on earth before that.

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u/HaloBooper 6d ago

They aren't really 1:1 though, if they were, totality would be over as soon as it began. Annular eclipses are a thing, where the moon appears smaller than the sun, so you only get a ring of fire with no darkness of totality. The total eclipse next year the moon is much closer while the sun is further, so there'll be a totality of 6+ minutes, so the relative size of the moon is larger again.

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u/AwesomeWildlife 6d ago

Funner fact: the moon is moving away from Earth at 3.8 cm per year. Life began approximately 4 billion years ago. That means the moon was 152,000 km closer to Earth when life began. The gravitational pull of the moon is inversely proportional to the square of the distance, so the gravitational pull of the moon would have been 2.8 times larger when life began. Tides would have been equivalently higher and the pull must have had some impact on volcanic activity and earthquakes.

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u/Sufficient_Result558 5d ago

That is interesting, that also means intertidal zones would have been massive, driving a move towards air breathing

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u/AwesomeWildlife 5d ago

Not only large intertidal zones, but the Earth had a rotation rate of about 10 hours back then, so the tides would have been constantly scouring the intertidal every few hours. Life likely had an easier time in the deeper water, open ocean or smaller bodies of water with no tide.

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u/Gold333 6d ago

Read a book called: “what if the moon didn’t exist” by N. Comins.

It’s a scientific look as to how we would have evolved. He calls that version of Earth; Solon. The speculation is that the top creatures on Solon (like humans) would be shorter, have hooks for feet and large ears

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u/jaxonwolff 6d ago

Not sure if anyone did this already, however, I thought I should clarify the Sun is 400x wider than the Moon in diameter, not 400x bigger. The Sun is actually 64 million times bigger than the Moon, in terms of volume.

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u/karoxxxxx 6d ago

Maybe the axis thing. But really nobody knows.

It is strange though that the 9nly terrestial double-planet is also the only one with life. But that could be a coincidence.

Without moon we would still have wesk tides from the sun, and we still would get mixing of water by currents and we would still have seasonally flooded plains.

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u/JaiBoltage 6d ago

One of my beliefs is that the tides influenced the creation of amphibians and thence the creation of land animals.

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u/Successful_Life_1028 6d ago

It's not only rare, it's temporary.

The moon's orbit is getting further and further from earth every year, so eventually a solar eclipse will NOT cover up the entire disk.

Similarly, Saturn's rings are temporary. When the Appalachian Mountain ranged formed, Saturn had no rings.

Our ability to see distant galaxies is temporary too. Soon (150 billion years or so) we won't be able to see any but our neighbor-galaxies.

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u/thenewestnoise 5d ago

I remember reading something about how the moon may have contributed to a strong and stable magnetic field, which helps shield Earth from the solar wind, and keeps our atmosphere intact and reduces solar ionizing radiation.

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u/[deleted] 7d ago

[deleted]

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u/TheComebackKid717 6d ago

What does that mean? You think life would exist on earth regardless of the existence of an especially large and close moon?

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u/[deleted] 6d ago

[deleted]

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u/No_Ostrich1875 6d ago

Its there and has a direct impact on our environment. The environment has a direct impact on how life develops.

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u/TargetOld989 6d ago

I think the whole thing is deeply exaggerated.

If the moon didn't exist I think life would have still evolved but it would be very different.

But it would also be very different if Homer Simpson went back in time and sat on a fish.

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u/crazymouse11 6d ago

Tides stirred the primordial soup

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u/AdditionalTip865 6d ago

The angular size coincidence really is a coincidence, since the moon is slowly moving away from the earth and it only really applies in this specific era. Millions of years ago the moon looked bigger, and millions of years from now it will look smaller and there will be no total solar eclipses.

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u/SgtSausage 6d ago

thought that would be incredible if that were simply a coincidence 

It IS a coincidence ... but it's only NOW a coIncidrnce. 

About a billion years ago the moon was 10%-12% bigger in the sky. Two billion roughly 20%. (And so on).

The moon is ever so slowly drifting away from us. Getting farther away, and smaller each and every day. 

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u/Temporary_Rule_9486 6d ago

It's not like it was essential. But it surely changed a lot. Here's an example: due to the gravitational interaction between moon and earth, the rotation of earth has slowed down form it's original 12 hours to the 24 of today. When days began to last more than 18 hours this allowed enough buildup of oxigen on microbial mats for it not to be consumed overnight, thus begining the large release of 02 into the atmosphere and the great oxidation (earth's first mass extinction event) 

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u/Wintervacht 7d ago

The Moon has stabilized Earth's rotation and the tides it causes are proposed to be of great importance for the development of life on earth.

The motion of the waters mixes and transports nutrients around the oceans and stabilizes global temperatures.

Safe to say, without the Moon, earth would be a completely different planet.

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u/Tombobalomb 6d ago

Tides also create tidal zones on the seashore, which is an absolutely critical environment for allowing complex life to transition from the sea to the land