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Everyone's favorite ground squirrel Sandy Cheeks has been karate chopping and barbecuing her way into our hearts since we first got a glimpse of her in the original season of Spongebob. This Texas-loving critter has had some memorable moments and has one of the coolest living arrangements in all of Bikini Bottom, her tree dome. But could a tree dome work in real life?
So when you think about what it takes to support a mammal it comes down to a handful of essential things needed: oxygen, temperature, and of course food and water.
Sandy is shown eating the acorns from the tree as well as other under the sea food, not to mention she could travel in her underwater suit to get food and return. As for water, she most likely has what's called a solar distillery to convert the salt water to fresh water. It’s a simple way to have an endless supply. So let's move on to the temperature
According to the scientific article titled: “Temperatures of Hibernation and Changes in Body Composition of Ground Squirrels over Winter,” (and yes, that is a real scientific journal article) it says ground squirrels can survive in temperatures as low as -18 degrees Celsius or -0.4 degree Fahrenheit.
So with that in mind let's figure out what the temperature would be in Bikini Bottom. It is commonly speculated that Bikini Bottom is based on the real life nuclear test site Bikini Atoll, which has a depth just over 60 meters or near 200 feet. The depth is relatively shallow compared to the deepest parts of the sea. This graph shows that ocean temperatures at that depth are actually high enough to sustain a ground squirrel.
So far so good, right? We’ve got food, water, and a temperature high enough for the tree dome to work. Well let’s keep going and take a look at oxygen levels.
We all know that plants produce oxygen, but how much? Would the one tree and smaller plants in the tree dome be able to provide enough oxygen for a mammal to survive? According to chemistry.about.com the amount of oxygen produced by a single tree depends on the size, health, and type of the tree. As we can see the tree in the dome is a leafy tree. From the acorns we can tell it’s an oak and it is clearly in perfect health.
Back to chemistry.about.com's article that states: “A single mature tree can absorb carbon dioxide at a rate of 48 lbs./year and release enough oxygen back into the atmosphere to support two human beings,” which is more than enough for one ground squirrel, so we are all good on oxygen.
Now according to Sandy, the dome is made out of polyurethane, which has a compressive strength of 20,000psi. Now, how much weight could that support? Let's be generous and assume that the dome is a meter thick. The internal pressure in a thin-walled spherical shell is defined by pr/2t, where p is the pressure, r is the radius of the shell, and t is the thickness. This means that the maximum pressure it can withstand is C*2t/r, where C in this case is 20,000psi, meaning that the dome could withstand up to about 3200psi of pressure before breaking — around 218 atmospheres. Since the ocean pressure increases by about 1 atmosphere of pressure every ten meters it would have to be around 2180 feet deep before it shatters. Being that the Bikini Atoll is only 200-ish feet deep, the dome would not break under the pressure of the sea.
So lets recap: The temperature is high enough, there is ample food, water, and oxygen, and the dome would withstand the ocean's pressure. So it's all good then, right? Not so fast. Even though we’ve established that the single tree could provide the oxygen needed, there’s still one more thing needed: The sunlight needed to keep the tree alive. Some light does make it to that depth, in fact many small life forms use photosynthesis all the way down to 600+ feet. However, it certainly would not be enough light to support the photosynthesis needed to keep a tree of that size alive.
Therefore the idea for a self-sustaining underwater tree dome falls just short of being possible — at least at that depth. So there you guys have it: Sandy wouldn’t be able to live in Bikini Bottom long before her tree died and her oxygen ran out.
Let me know what you guys think about this. Also make sure to check out my Youtube channel from the video for more awesome cartoon videos!