What would happen if we had no moon?

What would happen if we had no moon?

What would happen if we had no moon?

That was a questioned posed by one of my kids this week. It lead to lots of discussion and interesting debate until finally we were talking about werewolves!


 photo credit: kendoman26 Not Quite There! via photopin (license)

Firstly, lets consider how the Moon got there in the first place.

The Moon is approximately 4.51 billion years, about 60 million years younger than the Solar System. It formed from the debris from created by a massive collision between a large asteroid (about the size of Mars) and the early Earth.

Originally the Moon spun on its own axis much more quickly than it does today, as did the Earth. However, over time the Moon’s spin slowed down. This is because the gravitational pull of the Earth on the Moon distorted its shape, making it bulge in the centre and ultimately (it took an estimated 1,000 years) it slowed it down until the speed at which is spun on its axis matched the rate at which it orbited the Earth. This is why we only see one face of the Moon. If you still find that hard to understand test it out with two balls or check out this great video by Minute Earth.

Almost all moons in our solar system spin on their axis at the same speed as they orbit their planet.

Of course the gravitational forces between the Earth and the Moon are not one sided, the Moon also has a gravitational pull on the Earth and this causes some obvious effects here on Earth, like the tides in our oceans and seas.

Not that we know how it got there, let’s consider what would happen if it suddenly disappeared.

  1. Darker nights

    Although the night sky would still be lit by so many stars in our galaxy we would definitely notice it darker without the Moon. The full Moon on a cloudless night provides enough light for us to navigate by, in fact we can nearly read by its light. On these nights the Moon is about 1500 times brighter than Venus, the next brightest object in our night sky.

  2. Shorter days

    Without the stabilizing effect of the Moon, the Earth would begin to spin more quickly. It is estimated that a day on Earth would eventually only be about eight hours long, meaning there would be about three times more days (1095) in a year. However, this effect would happen very, very slowly. How long?

  3. Less extremes between high and low tides

    The gravitational forces exerted by the Moon causes tides to rise and fall in our seas and ocean, this is called lunar tides. Without the Moon we would see a big drop in the difference between high tide levels and low tide levels. There would still be some tidal difference (as the Sun exerts a gravitational force too – solar tides) but it would be a lot less, maybe as much as 40% less than what we have now.

  4. A more extreme climate

    As mentioned above, the Earth would spin more quickly on its axis without the Moon around to slow it down. The Earth is also tilted slightly on its axis as it spins. At the moment the Earth is at a tilt of 23.5 degrees on its axis. The Earth’s tilt can wobble slightly, but, due to the Moon, it never stays between 22 and 26 degrees. Without the stabilising forces of the Moon the Earth would wobble a lot more as it spins. This would lead to changes in our seasons. Sometimes it would tilt too far, resulting in extremes of temperatures and seasons. Sometimes there would be no tilt at all, meaning no seasons at all. Whatever way it goes, we would certainly find some extremes in our weather conditions if we had no Moon.

  5. No solar eclipse

    A solar eclipse happens when the Moon gets between the Sun and the Earth, casting a shadow over the Earth. There are different types of solar eclipses, but a complete solar eclipse is quite a spectacular show, the entire sun can be blocked briefly by a full moon, causing complete darkness from the correct viewpoint on Earth. Without a Moon, these spectacles (which can occur somewhere on earth every 18 months or so) would cease! Of course  lunar eclipses would no longer exist either; A lunar eclipse occurs when the Sun, Earth and Moon align with the Earth in the middle, casting a complete shadow on the Moon and preventing any of the Sun’s light from reflecting off it .

  6. No Werewolves!

    We are back to the werewolves. My kids put up a good argument that without a moon Were-people could not change into Werewolves, and they therefore wouldn’t exist. I know better than to argue with that one!


If your questions expand beyond the Moon why not check out my Appliance of Science column in today’s Irish Examiner where I answer questions on the Universe and beyond.

To infinity and beyond – a miscellany of space explorations

To infinity and beyond – a miscellany of space explorations

It seems the subject of space travel is everywhere at the moment. Here are just a few topics that have cropped up in my time line in the last few weeks.


Firstly there was the timely and obliging space probe that landed on a comet right in the middle of our national Science Week, but for a while it looked like an inappropriate fashion choice would overshadow the momentous occasion.

Image credit: ESA–C. Carreau/ATG medialab
Image credit: ESA–C. Carreau/ATG medialab


It was always an ambitious project of the European Space Agency (ESA), to get the rosetta spacecraft to rendez vous with Comet 67P/Churyumov-Gerasimenko, but, after ten years in space it arrived at its destination on 4th August 2014. Even more spectacularly, Rosetta sent out her Philae Comet lander which successfully landed on the comet on 12th November. The initial joy turned to fear as the science team involved, watched by the rest of the world, realised that Philea did not stay in the initial landing point but “bounced” along the surface on the comet, coming to rest, finally, in the shadow of a cliff. There was much worry as to whether the probe would receive enough sunlight in that location to power all its scientific equipment expected to perform a series of investigative experiments on the surface of the comet. In the end all fears were allayed and all data was collected and transmitted back to earth. The team were able to heave a collective sigh of relief, marking a new line in the history of space exploration. Hopefully the event will be remembered for its scientific breakthrough rather than the #shirtgate hash tag it spawned.



I really enjoyed a conversation last night with my nine year old and his friend as we discussed what our favourite planets were and could we really live on Mars. When I spotted this video I had to share it with him and it certainly made him giggle.




Speaking of space travel, it would seem that the moon is now back on the map for space exploration, this time spearheaded by the UK and funded by the general public. The very ambitious Lunar Mission One project plans to use crowd funding to finance a trip to the moon. The original mission will be a robotic exploratory project with plans to drill deep into the moon’s surface (possibly as deep as 100 Metres). The lunar rock that will be mined from these depths is expected to be about 4.6 billion years old and it is hoped that it will shed new light on the original formation of the moon and indeed the earth and the entire solar system.

The incentive for potential funders is obviously to be part of such exploration, but, as an added bonus, each person who pledges money will be able to include something into a public archive, a type of time capsule that will be buried on the moon during the mission. This archive will include information on must of our planet’s historical events, as well as DNA from people who have funded the project.



Of course NASA take credit for the original moon landing and a lot more besides, but did you know that a lot of items of everyday use stem from technology originally created for space exploration? This infographic lays it out really well and I was certainly surprised at a lot of the items listed.

Source: GreatBusinessSchools.org



It would seem that space exploration is a hot topic in Hollywood too with the recent release of Interstellar. In the movie the mission is to travel farther than ever before to find a new home for humanity as earth will cease to support life within one generation. To travel these distances the team must use wormholes, a theory that some hope will one day become a reality. The expert advice on this one however is that wormholes, as we know them would never be able to support human travel. They would require more negative energy than space can provide, in order to stay open long enough to allow such travel.