We recently received the following question about the moon:
…would we miss the moon if it did not exist? I’m not asking what crazy improbable situation would be needed to remove the moon, just what the observable differences upon the Earth would be if there was no moon? Obviously there would be tidal differences, but would we have any other major effects I’m not aware of?
Thanks for the question Matt, This was a fun topic to research.
There are more ramifications from a missing moon than you might realize.
Of course you’re correct that there would be tidal differences but the details may surprise you.
Fist of all, the tides wouldn’t disappear. Everyone usually associates the moon with the tides but the sun contributes as well. These sun-only tides would be smaller of course; in fact they’d be about one third as high as they are today. They would also be very simplified as well, consisting of just a high tide and a low tide with no variation. This is because neap tides and spring tides would disappear since there would no longer be any moon to add to or subtract from the sun’s tidal influences.
Since Matt wanted to know the observable differences if the moon disappeared, I am creating an Observable Difference Factor scale from 0 – 10.
10–is easily observable by anyone not in a vegetative state.
1–is noticeable only by very alert scientists.
0–is not noticeable at all even by a post-singularity super-intelligent AI.
I give the tides an Observable Difference Factor of 9.
If you live or work near the coast and have a fully functional parietal lobe you will notice that the tides have changed.
Did you know that a day on earth billions of years ago was only 6 hours long? Talk about days flying by.
Geologists know this by counting the growth rings in 400-million-year-old coral fossils and 3-billion-year-old stromatolites. Our days have been steadily lengthening because of a fascinating phenomenon call tidal breaking. The huge high-tide bulge of water closest to the moon is never right under the moon because the earth’s spin is moving it away. Gravity pulls the moon towards the bulge which speeds the moon up forcing it into a higher orbit. The bulge is also attracted to the moon so it tries to move toward it which is in a direction opposite to earth’s rotation. This increased friction slows the earth down. A more technical way to look at it is conservation of angular momentum. The total angular momentum of the earth/moon system must remain the same. The moon gains angular momentum as it moves away; therefore the earth must lose it to maintain this zero-sum game.
The bottom line then is that if the moon disappeared, the lengthening of our days would greatly slow down. It would still occur though due to tidal breaking caused by the sun.
I give this an Observable Difference Factor of 1.5
Scientists would notice this easily but some regular people would also notice that leap seconds stopped occurring every two years or so.
Picture the two dimensional path the earth takes around the sun. Now picture the axis upon which the earth spins. There is not a 90 degree angle between these lines. If that was the case, the earth would be a seasonless world. It is because the earth is tilted 23 1/2 degrees away from 90 degrees that I have to endure this bitterly cold winter for many months before spring-summer-fall arrives to reset my sanity back to baseline.
We take this angle for granted don’t we? It’s easy to think that this angle is fixed at the birth of the solar system and stays that way. It turns out though that our moon is a great axis of rotation stabilizer. Without it, the earth’s axis could potentially swing from 5 degrees to 40 degrees based on the various gravitational interactions with the other planets. Imagine what this would do to our weather and evolution. For those of you more into short-term thinking, you wouldn’t have to hold on to anything were this to happen. This wobble could take thousands or hundreds of thousands of years to occur.
I give this an Observable Difference Factor of 1
Only scientists (and cloaked alien satellites) would notice this
The only other significant effect I could find has to do with the altitude of the water in our oceans. Apparently, without the moons gravity, the water in our oceans would migrate a certain extent from the equator to the polar regions. It was unclear from my research how dramatic this effect would be.
I give this an Observable Difference Factor of somewhere between 5 and 9
This discussion seems to beg the question of what would the earth be like today if it never formed the moon in the first place after that Mars-sized object slammed into the early earth (imagine seeing that coming?).
I won’t go into detail but I’d like to briefly address the likely result.
An Earth day now would only be 8 hours long due to the isolated effects of sun-earth tidal breaking.
A faster spinning earth would likely have horrific winds. Daily winds could reach 100 mph and hurricane winds would be quite nasty.
Evolution would be greatly impacted but it still would have occurred I believe. Life seems so tenacious and seems to have started as soon as it was possible but humans certainly wouldn’t be here if the moon never was. It seems likely that at the very least evolution would have been delayed or slowed greatly. With no moon there would be no mountainous tides early in earth history to scour the land every few hours and bring back to the primordial soup the critical chemical ingredients of life.
As I sit here contemplating these changes I am also grateful for some moon-based words that I would miss if they disappeared with the moon like lunatic and mooning.