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Have you ever pondered a hypothetical scenario? This Curious Kids article delves into an intriguing question sent in by young readers: If every person on Earth simultaneously entered the ocean, what would be the impact on sea levels?
Reader Question: If everyone on Earth sat down in the ocean, how far would the water rise? – Zahkaev and Viktor
Engaging with hypothetical questions, such as the global ocean swim scenario, can be a stimulating exercise. Employing mathematical principles allows us to derive a close approximation to a real-world answer. To begin, let’s examine a simplified version of this query.
Understanding Displacement: The Bathtub Analogy
Consider a bathtub filled to its brim. Upon entering, you’ll observe water spilling over the edge. This phenomenon occurs because your body displaces water, a concept known as displacement. Given the solid confines of a bathtub, the expelled water has nowhere to go but upwards and out.
The amount of space occupied by an object – in this instance, your body – is termed volume. The volume of water that overflows from the tub precisely equals your body’s volume.
Now, picture a bathtub that is only half-filled. As you get in, your body’s volume still pushes the water upward. We can calculate the precise increase in the water level within the tub using straightforward mathematical equations.
Assuming a rectangular bathtub, we can determine the water level increase caused by sitting in it by considering the added volume and the surface area over which this volume is distributed. The rise in water level is equivalent to the added volume divided by the surface area.
For a bathtub measuring 5 feet in length and 2 feet in width, the surface area is 10 square feet.
Let us now estimate your volume. To simplify the calculation, we’ll approximate your shape as a rectangular box, similar to the bathtub. Imagine you are roughly 4 feet tall, 2 feet wide, and 1 foot deep. Your body volume would then be 4 feet x 2 feet x 1 foot, totaling 8 cubic feet.
When you sit, approximately half of your body’s volume is submerged, contributing to the water level rise. Therefore, the water level increase is calculated by dividing half your body volume by the bathtub’s surface area. Using our approximations, this yields a water level rise of 4 cubic feet divided by 10 square feet, resulting in roughly 0.4 feet or about 5 inches. This change would be readily apparent.
Global Scale: Calculating Ocean Rise
Consider the world’s oceans as an immense bathtub. Oceans encompass over 70% of Earth’s surface, providing a vast area of approximately 140 million square miles for this global bathtub. To ascertain the sea level rise from everyone entering the ocean, we need to determine the total human volume and divide it by this oceanic surface area.
The current global population is nearing 8 billion individuals. Human dimensions vary significantly, from infants to adults. Let’s estimate an average human height of 5 feet – slightly taller than a child – with an average volume of 10 cubic feet. Assuming only half of each person’s body would be submerged while sitting, the added volume per person is 5 cubic feet. For 8 billion people, the total added volume to the oceans would be an astonishing 40 billion cubic feet (5 cubic feet/person x 8 billion people).
However, this substantial volume is dispersed across the colossal expanse of the oceans. Applying the bathtub principle, we divide the 40 billion cubic feet of human volume by the 140 million square miles of ocean surface area.
The result reveals that the total sea level rise would be approximately 0.00012 of an inch, or less than one-thousandth of an inch. Even if every person were completely submerged, this figure would merely double to 0.00024 inches – still roughly equivalent to the width of a human hair.
Ultimately, the oceans are of such a magnitude that humanity’s collective volume is comparatively insignificant – akin to a drop in a vast bucket.
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This report is based on scientific analysis from reputable sources.
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