In the Movie, Despicable Me 2, Gru shrinks the Moon down the the size of an orange causing surfers waves to suddenly collapse. Let’s comment on the geology of this phenomenon, including considerations of metamorphic reactions with the shrinking Moon, how that might affect the Moon’s mass and density, and how this would affect waves (tides?) on Earth! This is intended as a discussion area for the college course “Earth Science Essentials for the Science Fiction Writer” but, please, others are strongly encouraged to participate!
The gravitational attraction from the moon causes the oceans to bulge out in the direction of the moon. Ocean levels fluctuate daily as the sun, moon and earth interact. Without of of these things would be a lot different, so if one of those things isn’t there then the sun and the earth can’t do what they are supposed to do also. Tides are created because the Earth and the moon are attracted to each other.
Hey Lauren. Do you think the video is accurate? Good post!
I wish this was accurate so we could all go hang out on the moon due to its gravitational pull on our bodies!!
I like your explanation about tides. What do you think about the movie? Could it happen?
Is the moon the only thing that attracts the tides? Do you believe that the tides will disappear entirely?
I wish this was real so we could all hang out on the moon due to that gravitational attraction!
Agreed I think its the absence of moon that will affect the tides. I think if Gru doesn’t steal the moon and let it stay where its supposed to be the tides won’t change due to the shrinkage as the mass of the moon will be the same
Shrinking the moon on this scale (i.e. from it’s actual size to small enough to be held) would produce a number of changes. From what we know about metamorphism, shrinking the moon at this scale could change both the moon’s texture and even change the minerals that make up the moon. For example, when coal is put under pressure (which is probably one of the ways that the moon would have to be shrunk, without magical shrink rays) , the arrangement of atoms has to change to form a diamond, and thus the appearance and properties of the rock changes. The same thing would likely happen to the moon, and when shrunk it could even look very different, just like coal and diamonds!
Assuming that the moon is being shrunk and just becomes a miniature version of itself, this makes it seem like the mass would not change. Therefore, as density = mass/volume, with the mass staying constant and the volume decreasing, this would cause the density of the moon to increase. As judging by the size change, the moon would become VERY dense.
As far as tides go, according to the US National Oceanic and Atmospheric Administration, while the moon plays a big role in the tides on Earth, the sun plays a role as well. The alignment of the sun, moon, and Earth affects tides on Earth, not just the presence of the moon. When the sun, moon and Earth align you get either very low or very high tides. When the sun and moon are at right angles however, the effects of the sun partially cancel out the effects of the moon, causing tides that are not very high or very low (more in the middle). Therefore, while removing the moon would obviously make some big changes, but it likely wouldn’t be instantaneous. Not all waves are caused by tides either, some are caused by wind and weather, which is another reason why they would not immediately stop if the moon was removed.
(Information on tides from: http://oceanservice.noaa.gov/education/kits/tides/tides06_variations.html )
I had not heard before that the sun and moon work in tandem towards the gravitational effect on the tides. It had always been taught to me as a lunar-only phenomenon. Thanks for putting this little detail into your comment.
I actually didn’t know that the sun and moon worked together either until I did some research!
Great informative post!
In order to the moon to shrink, it need pressure from forces bases on high level of temperature if we consider the force applied by the big gun on the moon in the video. In this case, the earth will be affected by lacks of season and the sun will be exposed to the earth which is crucial for it population. Also, it will safe to say that maybe we are not going to see any waves form by ocean. It is important to point out that The other forces acting on the moon come not from its interior, but from Earth. These are tidal forces. When the tidal forces are superimposed on the global contraction, the combined stresses should cause predictable orientations of the fault scarps from region to region. To sum up, i have to say that the video is quite accurate.
You are right that their would still be waves. The sun would still have an effect on the waves with solar tides. Without the moon the waves would be a lot smaller and the ocean in general would be a lot calmer. Good job on your science!
Yup I totally agree the video is pretty accurate. And I like that you point out the forces on earth like the tidal forces. Thanks for explaining that more as well. Great post!
If we really were to shrink the moon, a large number of changes would take place. First, there would be the changes to the moon itself. From what we know about metamorphism, to shrink the moon to the size of an orange would take an enormous amount of pressure and a high temperature. There would likely be a large number of changes to the moon itself. It would become extremely dense, having been compacted down to a mere fraction of its original volume but not losing any of its mass. The moon may also change in appearance, more than just by shrinking. It would not look like just a tiny version of the regular moon. The high pressure needed to shrink it would likely cause changes to the moon’s minerals. Different minerals may be visible or may form out of the elements already in the moon, so the color of the moon may change. Additionally, the pressure would also cause the texture of the moon to become different. There would also be changes that would occur on Earth. The tides would be enormously changed as there would no longer be an object of the right size to cause the gravitational pull influencing the tides. Waves in the oceans would continue to exist (boats, wind, and shifting plates cause waves too), but there would not be as many without a tide.
Malena,
I found your inclusion of fractionation in your discussion very interesting: “Different minerals may be visible or may form out of the elements already in the moon, so the color of the moon may change.” Since this movie is science fiction, we can’t be certain what the mechanism of shrinkage actually was. But, it had to have involved heat and pressure, and there may have been melting of the rock in the process. This melting could potentially result in fractionation, with certain minerals being concentrated in either the liquid melt or solid crust of the recrystallizing moon.
I like the point you made regarding the look of the moon after. It would certainly not look like a “mini moon”. I thought differently about the tides. I thought if the mass remained the same that maybe the tides would not be affected, but there are so many more factors to consider. Good thing we are talking about a fictional character and not reality.
I like how you highlighted the visible changes. Due to the stress of shrinking, the materials will move and stabilize, which would greatly change the appearance.
I agreed with a lot of your thoughts on what would happen and how much is real. I really liked your thought about the minerals and rocks that are on the moon. I mainly just about what was happening to the moon as a whole. I forgot about the smaller details and what would happen to those items. Great thoughts!
Very interesting information about the changing of the moon itself. Good post!
Temperature and pressure could cause the moon to shrink if they were great enough. This shrinkage could cause mineral composition of the moon to change. It could be possible. However, probably not to the extent that it occurred in Despicable Me.
Shrinking the moon would affect the force and size of tides. If you think of the moon as a magnet, shrinking it would decrease the magnetic force or pull it exerts on the earth. The reason we have tides is because the moon is tidally locked with the earth. When the sun is aligned with the moon and earth, the gravitational pull is stronger. The centrifugal force of the earth also adds to the force of the tides and waves.
If there was no moon, we could possible not have tides or waves. The ocean would be a large body of water that just sits there.
Shrinking the moon so dramatically would require an absolutely immense amount of equal pressure from all sides given any weak spots in the “shrink” field would cause an explosion of matter to escape. The texture and mineral composition would change as well, textures become a good bit smoother as matter is forced to crush down to more and more advanced stages of metamorphism likely to create thin leafy layers if the rock was chipped away once it reached this ultra-dense orange sized object. if it hadn’t already become some sort of huge diamond or a black hole. Also it is likely the miniature moon would be incredibly hot after this change not only from the friction inevitably caused by all that matter crushing inward but by the changes at the atomic level to the minerals that make up the core of the moon.
The part about the tides is debatable, of course waves wouldn’t instantly disappear without the moon but depending on the tide there could be other problems. I believe gravity is a property of mass and changing the size of the mass does not change the amount of “stuff” that is exerting it’s gravity on other celestial bodies so I would guess that this mini-moon would have the same effect on earth as the bigger version did, except now it is not in regular orbit but much closer to earth as it stays in Gru’s pocket. This would make it incredibly difficult for Gru to slow his decent on re-entry and create a fairly apocalyptic scenario to have the entire mass of the moon come crashing down to the earth in which case, I think big waves might be the least of one’s worries.
The shrink ray would have to apply high temperature and high pressure for the moon to shrink. It would cause the moon to become much more dense than its original size. Even though the weight would be the same, the size would effect the tides, like in the movie. The pull from the moon in orbit around earth aides in the high and low tides daily, but with the size of the moon shrinking it would cause the change in the tides to be much less dramatic.
The metamorphic force that is likely to cause the moon to shrink (i.e., increase in density) is pressure. We learned in the lecture video that pressure compresses the rock and causes its density to increase. The other major metamorphic process, heat, causes entropy to change, and the shrinking of the moon would not be a direct cause of changes in entropy. Further, driving water out of the rock – a process we touched on – has the potential to have the same density-increasing impacts as pressure, but its effects are likely less. Increasing a rock’s density will result in property changes. Specifically, it may result in foliation, where the constituent minerals are changed into more stable arrangements (e.g., schistosity). Not only this, but the pressure would also likely cause the cratered landscape on the moon to compress down into a flat landscape. Since we did not see the post-shrinking moon in the moon, it is unclear where these things occurred.
In regards to tides, the shrinking of the moon would likely impact tides. According to NOAA, gravity generates tides. This force is equal to the following equation: Tidal force = massEarth * massmoon *gravitational constant /distance^2. In the scenario in the video clip, it is assumed that no mass was destroyed when the moon shrank. Plus, we know that the Earth’s mass didn’t change either, and the gravitational constant does not change. Thus, in the equation, the numerator remains the same. In the denominator, the distance should not change either, assuming that the distance variable is measured from center of mass of the two affected objects. If this is the case, then the tidal force would remain unchanged. If however, the distance is measured between the outer edges of the two objects, then the tidal force would decrease significantly. This is because the moon’s radius would go down from 1,737.1 km to only about 5 cm, and this value is squared so it would result in a substantial change in tidal force magnitude. I was unable to figure out which method is correct, however, as I found no clear indication in my research. Does anyone have the answer to this?
The movie may be off-base in its depiction of the disappearing waves in this scenario. According to NOAA, waves are formed by wind and earthquakes, in addition to gravitational tidal pull. The size of the moon doesn’t affect waves formed by winds. Winds are caused by uneven heating of the Earth by the sun. Further, waves that are formed by earthquakes (e.g., tsunamis) would not be affected either, because tectonic activity in the Earth is not impacted by the moon. However, as I conjectured above, it is quite possible that tidal waves would be less powerful or less frequent because of a diminished tidal force. So, waves will still be present in our lakes and oceans, but we may not have the same number, type, and size as before. The movie’s depiction of the wave disappearing from under the surfer is inaccurate, though. Even after the force giving the wave its initial energy was diminished, the wave would retain its initial energy until it crashed into shore or some other object. There is no entity in the universe that would remove its energy mid-break without contacting it.
Sources: http://oceanservice.noaa.gov/education/kits/tides/tides02_cause.html, http://www.teachastronomy.com/astropedia/article/Calculating-Tidal-Forces,
http://www.universetoday.com/19732/radius-of-the-moon/, http://oceanservice.noaa.gov/facts/wavesinocean.html
The shrink ray would need a few different properties. One would be high heat capability and stabilization, as well as the ability to apply a mass amount of pressure. Another property, is that the ray would have time disruption properties. The ray could cause an intense amount of pressure surrounding the moon and stabilized pressure, making it shrink. The time disruption feature would allow the very slow process to work like time travel. Otherwise, it just wouldn’t work! From our metamorphic rock lecture, we learn that in turn the moon would have a higher density. If the moon shrunk due to all the differential stress, it would contain the same material but would look differently. The materials inside the moon would “rotate or dissolve” in order to stabilize.
If the moon changes size, but the mass is the same, the gravitational pull would remain the same. That is assuming the moon continues with the same rotation and the same distance. The distance is not exact in its orbit, but if held constant, maybe the tides wouldn’t change at all. No matter the change in the moon’s orbit or velocity, there would be significant changes of the ocean’s tides and waves.
If the there was no moon the ocean tides would be calmer- the waves would not disappear like they did in the movie but they would be calmer. This would have a dire effect on planet Earth. We would still have waves from the sun (solar waves).
The metamorphic changes would be different if the moon was shrunk like it was in the movie. It would take a lot of pressure and temperature to change the moon- the moon’s texture would be very different. It would be very dense and have low entropy. It would change the texture as well as its crystal structure also.
The rising and falling of the sea levels are because of the gravitational attraction with the sun and the moon. when the moon tries to pull on the water the earth is trying to hold on to it but its hard for the earth to hold on since the water is always moving. Making it easier for the moon to consistently pull at the water. Without the moon pulling on the water I we wouldn’t have the tides we do because we need that gravitational pull. So it may be an exaggeration in the movie but it does have the right idea that the tides are coming from the moon pulling on the moving water and the earth not being able to hold onto it.
In the movie Despicable me Gru uses the shrinkray to shrink the moon. To shrink the moon one would need a high amount of pressure and high temperature to have this happen. Also like we learned about metaphoric rocks the density will also increase. Now about the waves in the movie the waves wouldn’t just disappear like they do in the movie the water isn’t disappearing and where just a smaller force. A smaller moon would cause smaller tides though because there would be less of a gravitational force. Large tidal waves also appear the biggest on the opposite side of the moon so I don’t think that it would be a bright sun with the huge wave that disappears. It was a really interesting thought to look at a movie like this and look for real and unreal parts.
As far as the moons effect on the tides, there would still be tides. The moon isn’t the only thing that affects the tides. Wind, sun, temperature and weather are all factors. There just wouldn’t be as many and they wouldn’t be able to get to the massive swells that we have today. So no, Despicable Me was not accurate.
For the moon to shrink to the size of an orange and thus keep the same mass there would have to be an immense amount of high pressure and temperature according to what we’ve learned in the metaphoric rocks unit.. To the extent it happens in Dispicable me is improbable and most likely impossible but its an interesting thought to think about as the moon would thus have so much attraction causing changes in waves, tides and everything. Although those things are also affected by many other things as well. Along with this the moon would also be much denser, changing mineral composition and crystallizing different.. So many things would happen but they never will because nobody is going to shrink our moon to the size of an orange!
The moon isn’t the only thing that causes tides in the ocean, we have to consider wind, weather, plate movement, and temperature. The absense of the moon wouldn’t stop all activity in the ocean. Also, to have something the size of the moon shrink down that small, the density would be incredible. The general makeup of the moon would change as well, as rocks change under pressure.
The shrink rays are creating pressure on the moon causing for it to shrink. Due to the shrinking, the moon will become higher density. While the change in the size of the moon is evident in the movie clip there is no way to figure out if the mass of the moon changed as well.
when guru steals the moon the tides will be affected by it. while I don’t think they will dissapper instantly but there will be smaller and less intense.