What would happen if everyone on Earth decided to enter the oceans and seas at the same time? To answer this interesting question, it may be enough to use mathematics. However, it is useful to start with a much smaller-scale example of this problem first.
If you completely fill a tub and get into it, the overflowing water from the tub will create a significant wet area around you that you need to clean up. The water will overflow as it is pushed by your body and the bottom and sides of the tub are made of solid parts. The area occupied by an object in space is called the volume. The amount of water overflowing from the tub will also be equal to the volume of your body.
If we look at the situation when the tub is half full, your body volume will again displace the water and cause it to rise as you enter the tub. It is possible to calculate the amount of water rising with a few simple mathematical operations.
First, to simplify this example, let’s assume that the cuvette is a rectangular-bottomed box. It is possible to find the amount that the water will rise by calculating how much volume you add when you sit in the tub and what size area you spread this volume over. The amount of water rise can be calculated by dividing the added volume by the area.
Let’s say the tub is 1.5 meters long and 60 centimeters wide. This area will be 0.9 square meters. To calculate the volume of our body, we can make a similar simplification and think of ourselves as a rectangular-bottomed box. Let’s say we’re 1.5 meters long, 60 centimeters wide (from left to right) and 30 centimeters deep (front to back) once again. In this case, our body volume will be 1.5×0.6×0.3 cubic meters, that is, 0.27 cubic meters.
Considering you add about half of your body’s volume when you sit in the tub, this would mean that the water will rise by half your body’s volume divided by the tub’s area. Using the assumptions above, we can calculate that this is (0.27/2)/0.9 ie 0.15 meters, or 15 centimeters.
If the ocean and seas were a giant bathtub…
We can think of the oceans as a giant bathtub. More than 70% of the Earth’s surface is covered with water, which means that the area of our bathtub is approximately 360 million square kilometers. To calculate how high the water will rise, we need to find the volume of people sitting in the water and divide it by this ocean area.
There are almost 8 billion people in the world right now. Of course, people come in many different sizes and volumes, from babies to adults. However, for ease of calculation, assuming that we are on average 150 centimeters tall, that is, slightly taller than a child, we can say that our average volume is 0.27 cubic meters. Assuming once again that only half of our volume enters the water with submersion and 8 billion people are assumed, it can be said that we will cause a total displacement of 1,080,000,000 cubic meters of water.
But remember that while this number may seem enormous, it must be divided by the area of the ocean. When we divide this volume of 1,080,000,000 cubic meters into 360 million square kilometers (3.6×1014 square meters), as in the bathtub calculation, the number we get is only 0.000003 meters, or 0.0003 centimeters. Even if everyone is completely submerged in the water, this number is only 0.0006 centimeters, that is, about a hair.
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