![\"\"](\"https:\/\/talesofmanythings.com\/blog\/wp-content\/uploads\/2026\/10\/2026-10-16-1-restaurant-1c.jpg\")
<\/p>\nMy wife and I were sitting in a restaurant when the kid at the next table asked a perfectly reasonable question. \u201cWhy are the oceans salty?\u201d<\/p>\n
It\u2019s a good question. It\u2019s the kind of question that has occupied geologists, oceanographers, chemists and other people who get genuinely excited about rocks and water for considerably longer than anyone has occupied a restaurant booth. To be honest, I wanted to hear the answer, too.<\/p>\n
The child\u2019s father didn\u2019t hesitate. \u201cBecause people have been peeing for ten thousand years and it\u2019s all been running downhill.\u201d<\/p>\n
That\u2019s the answer that makes you squirt whatever you were drinking out of your nose.<\/p>\n
I definitely have questions. Not about the ocean. We have actual scientists for that. I have questions about the man who just delivered that answer with the confidence of someone explaining the quadratic equation to a room full of Nobel laureates.<\/p>\n
Was it a desperate attempt to get his kid to be quiet and focus on his fries? Was it an honest admission of ignorance disguised as a plumbing metaphor? Was he testing a new theory of oceanography and hoping the peer review process would be distracted by the appetizers? Or, and this is the possibility that concerns me most, did he actually believe it?<\/p>\n
Because somewhere between \u201cI don\u2019t know\u201d and \u201cthe Earth is a giant port-a-potty”, we seem to have misplaced our collective appreciation for the difference between an answer and a sentence that happens to contain nouns and verbs.<\/p>\n
Naturally, I had to investigate. For science. And because I couldn\u2019t get out of my head the image of eight billion people standing on the continental divide, peeing downhill.<\/p>\n
<\/p>\n
<\/p>\n
First, Let\u2019s Talk About the Plumbing<\/strong><\/p>\n The basic theory seems straightforward enough.<\/p>\n Humanity urinates. Gravity does its thing. Water flows downhill. Eventually, all the pee arrives in the ocean, where it accumulates until the planet\u2019s largest bodies of water achieve their distinctive salty flavor.<\/p>\n It\u2019s an elegant theory, provided you ignore geology, chemistry, hydrology, the water cycle and the inconvenient fact that the human race has not been around nearly long enough to explain the age of the oceans.<\/p>\n Let\u2019s be generous in our assumptions. Let\u2019s assume our father of the year is correct about the general mechanism and investigate whether the numbers support his hypothesis.<\/p>\n First, we need to know how salty urine actually is.<\/p>\n <\/p>\n The Science of Wee<\/strong><\/p>\n Human urine contains water, dissolved minerals, waste products and various other substances your kidneys have decided your body would prefer not to keep. Its composition varies with diet, hydration, health and a number of other factors, normally ranging from 2 parts per thousand to 9 parts per thousand. For the sake of argument, let\u2019s assign our hypothetical urine a dissolved salt concentration of 5 grams per liter. That\u2019s a deliberately simplified assumption, not a universal measurement of human urine.<\/p>\n Seawater, by comparison, contains roughly 35 grams of dissolved salts per liter. Our hypothetical urine is therefore much less concentrated in dissolved salts than the ocean.<\/p>\n Already, Houston, we have a problem.<\/p>\n If you fill an empty ocean basin with urine, you don\u2019t get an ocean with normal ocean salinity. You get an enormous, faintly yellow, mildly concerning body of liquid with a dissolved salt concentration considerably below that of seawater.<\/p>\n And here\u2019s another hiccup in the theory. You can keep peeing into the ocean until the cows come home. You can invite the cows to participate, too. You can recruit every mammal on the planet and establish a global initiative called Project Golden Shower.<\/p>\n The concentration won\u2019t increase just because you add more liquid of the same concentration. Five grams of salt per liter times a billion liters is a lot of salt, but it\u2019s still five grams per liter. Chemistry is annoyingly indifferent to enthusiasm.<\/p>\n So, technically, the father wasn\u2019t just wrong about the timescale. His entire mechanism fails the basic arithmetic test.<\/p>\n Let\u2019s not stop there. We still have oceans to fill.<\/p>\n <\/p>\n How Much Pee Would It Take to Make an Ocean?<\/strong><\/p>\n The world\u2019s oceans contain approximately 1.335 billion cubic kilometers of water. That’s 1,335,000,000 cubic kilometers. I wrote the number out because scientific notation can make absurd quantities feel abstract. Adding all those zeros makes them feel absurd in a more personal way.<\/p>\n Let\u2019s imagine emptying the ocean basins and refilling them with our hypothetical urine. To produce the same total mass of dissolved salt found in the oceans, we\u2019d need approximately seven ocean volumes of urine at our assumed concentration of 5 grams per liter.<\/p>\n That\u2019s about 9.35 billion cubic kilometers of urine. Seven oceans\u2019 worth. Humanity has apparently been underperforming.<\/p>\n Of course, we can\u2019t simply pour seven oceans of urine into the existing ocean and expect the salinity to reach 35 parts per thousand. We\u2019d be diluting the very thing we\u2019re trying to concentrate.<\/p>\n We\u2019d have to collect all that urine, extract the dissolved salts and get rid of most of the water. Imagine the industrial infrastructure. The world\u2019s largest desalination plants would look like your neighbor\u2019s kids\u2019 soapbox lemonade stand. We\u2019d need a processing facility so enormous that the phrase \u201cemployee restroom\u201d would take on a whole new meaning.<\/p>\n And then we\u2019d need to evaporate approximately six-sevenths of our collected liquid to leave enough concentrated material to fill the ocean basins at the desired volume and salinity. We have now officially reached the point where a child\u2019s question has become a planetary scale waste management proposal.<\/p>\n Let\u2019s see how long the collection phase would take.<\/p>\n <\/p>\n A Modest Proposal for the Next 2.3 Billion Years<\/strong><\/p>\n Suppose eight billion people each produce approximately 1.4 liters of urine per day. That\u2019s about 11.2 billion liters every day. It\u2019s a staggering amount of pee, by any reasonable standard. Wastewater processing plant managers are cringing at the very thought.<\/p>\n At that rate, collecting the equivalent of seven oceans of urine would take roughly 2.3 billion years. Two. Point. Three. Billion. Years.<\/p>\n That\u2019s long enough for continents to rearrange themselves, mountain ranges to rise and erode and entirely new forms of life to evolve, become dominant, invent plumbing and begin asking why the oceans are salty all over again.<\/p>\n Meanwhile, we\u2019re supposed to believe ten thousand years of human urination did the job? Ten thousand years is barely a rounding error on this particular timeline. It\u2019s the scientific equivalent of arriving at work three seconds early and claiming you built the building before the next person arrives.<\/p>\n Given the father\u2019s hypothetical proposal, we would need an unlimited supply of patience and a very large collection bucket and humanity would need to keep at it for hundreds of thousands of times longer than recorded civilization has existed.<\/p>\n That\u2019s before we get to the part where urine isn\u2019t actually a suitable substitute for the mineral composition of seawater.<\/p>\n At this point, I think we can safely retire the theory, unless the father was referring to an undocumented civilization of immortal giants with kidneys the size of military heavy lift cargo planes, in which case, I\u2019ll ask to see the peer reviewed literature.<\/p>\n <\/p>\n So, Why are the Oceans Salty?<\/strong><\/p>\n Here\u2019s where things get genuinely interesting, for a scientist, anyway.<\/p>\n Oceans didn\u2019t become salty because the planet has been used as a communal urinal. They became salty through a combination of geological processes operating over immense periods of time.<\/p>\n Unlike our proposed alternative, these processes have the advantage of being real.<\/p>\n Rainwater isn\u2019t chemically pure. As it forms and falls through the atmosphere, it absorbs carbon dioxide, forming a weak acid called carbonic acid. When that rain hits rocks, it gradually reacts with their minerals, breaking them down and releasing dissolved ions.<\/p>\n Some of those ions include sodium and chloride, the familiar components of table salt. Others include calcium, magnesium, potassium and bicarbonate.<\/p>\n Streams and rivers carry these dissolved materials toward the sea. Each river contributes a little. Then another river contributes a little. Then another. Repeat this process for millions and billions of years and the ocean receives a truly impressive mineral delivery service.<\/p>\n It\u2019s not particularly fast. Nobody is going to make a fortune by investing in a company that promises to dissolve the Rocky Mountains by Tuesday.<\/p>\n Given enough time, the process adds up. The Earth is very good at doing small things for an offensively long time.<\/p>\n Here\u2019s the other half of the equation.<\/p>\n Water evaporates from the ocean, rises into the atmosphere, forms clouds and eventually returns to the surface as precipitation. What\u2019s important is that when water evaporates, most of the dissolved salts stay behind. Evaporation doesn\u2019t create salt. It concentrates the dissolved material already in the water.<\/p>\n The ocean is essentially running a natural separation process on a planetary scale. Water goes up. Most dissolved salts don\u2019t. Rain then weathers more rock, rivers carry more dissolved minerals to the sea and the cycle continues.<\/p>\n It\u2019s a little like boiling a pot of salty water until the water disappears and the salt remains, except the pot is the size of the Earth, the heat source is a star and the process has been running for geological ages.<\/p>\n However, the ocean isn\u2019t simply getting saltier forever. There are processes that remove dissolved material, too.<\/p>\n Which brings us to the ocean\u2019s underground plumbing.<\/p>\n Beneath the waves, seawater circulates through cracks in the ocean floor and interacts with hot rock. At hydrothermal vents, heated water dissolves some minerals and triggers chemical reactions that can either add substances to seawater or remove them. Undersea volcanic activity also contributes materials to the marine environment.<\/p>\n The ocean floor is not just the bottom of a giant bathtub. It\u2019s an active chemical interface between the water above and the planet below. Unlike the hypothetical urine theory, this explanation doesn\u2019t require billions of years of humanity holding its collective bladder. It does, however, require a basic understanding of geology.<\/p>\n Apparently, we can\u2019t have everything.<\/p>\n This is the question that makes the whole subject more interesting than it initially sounds.<\/p>\n If rivers continuously carry dissolved material into the sea, why hasn\u2019t the ocean become so salty that it\u2019s automatically brining all the fish in it? The answer is simple. The ocean is part of a dynamic churning system.<\/p>\n Minerals are removed through chemical reactions, interactions with seafloor rocks, incorporation into sediments and biological processes. Some materials become part of shells and skeletons. Others are buried or transformed through geological processes.<\/p>\n The balance varies across different substances and timescales. Ocean salinity has changed throughout Earth\u2019s history and individual regions of the ocean can be considerably saltier or fresher than the global average.<\/p>\n The modern ocean has a broad, relatively stable average salinity because the processes adding dissolved material and the processes removing it operate together. Nature, as it turns out, has been managing the situation for quite a while. No committee meetings. No budget overruns. No press conference announcing the launch of the Global Urine Mitigation Initiative.<\/p>\n Just geology.<\/p>\n <\/p>\n Wait. Why is Pee Salty, Anyway?<\/strong><\/p>\n Before we leave our original theory behind, there\u2019s one more question worth asking. If the oceans aren\u2019t salty because of urine, why does urine contain salt in the first place?<\/p>\n The answer is that your kidneys are not tiny ocean making machines. They\u2019re sophisticated filtration and regulation systems. Your body needs electrolytes, including sodium, chloride and potassium to regulate fluid balance, transmit nerve signals and make muscles contract. Your kidneys filter blood and then carefully reabsorb the water and substances your body needs. They also regulate how much sodium and other electrolytes leave in urine.<\/p>\n Most of the filtered sodium is reclaimed. The amount that ends up in urine depends on your body\u2019s needs, your diet, hydration and other factors. Eat a lot of sodium and your kidneys may excrete more of it. Become dehydrated and your kidneys conserve water, producing more concentrated urine.<\/p>\n The result is a fluid that contains dissolved salts and plenty of other compounds, including urea. It\u2019s a carefully managed waste product, not a concentrated sample of the Atlantic Ocean.<\/p>\n Your kidneys are maintaining the chemistry of your internal environment. They are not conducting a long term geological experiment with the goal of seasoning the planet.<\/p>\n They have enough to do.<\/p>\n <\/p>\n The Real Question isn\u2019t About Salt<\/strong><\/p>\n Let\u2019s return to the restaurant.<\/p>\n A kid asks a question. A parent supplies an answer. The answer is absurd, but it arrives without hesitation. Maybe it was a joke. Maybe it was an attempt to end the conversation. Maybe the father simply didn\u2019t know and didn\u2019t want to admit it.<\/p>\n Any of those explanations are possible.<\/p>\n To be fair, nobody knows everything. Not even scientists. Especially not scientists, who spend much of their professional lives discovering how much they don\u2019t know. Trust me. I live that life.<\/p>\n There\u2019s nothing wrong with saying, \u201cI don\u2019t know.\u201d There\u2019s nothing wrong with guessing, provided you identify it as a guess. There\u2019s even something valuable about making a ridiculous hypothesis and then testing it. That\u2019s how you get from an interesting question to an interesting answer.\u00a0 Or discover you were wrong.\u00a0 I have a story for this, too.<\/p>\n The problem isn\u2019t ignorance. Ignorance is the starting point of learning. The problem is treating confidence as a substitute for knowledge.<\/p>\n A child who asks why the ocean is salty has given an adult an opportunity. You can encourage curiosity. You can explain what you know. You can look it up together. You can discover that the answer is more complicated and fascinating than either of you expected. Or you can tell the kid that ten thousand years of human urination has turned the planet into a giant saltwater aquarium.<\/p>\n One of those approaches might produce a future geologist. The other might produce a future politician. I\u2019ll leave it to you to decide which is more concerning.<\/p>\n In the meantime, the oceans remain salty, the rivers keep carrying dissolved minerals downhill and the human race continues to produce urine at a truly astonishing rate.<\/p>\n If we ever discover that the father was right, I want credit for asking the obvious follow-up question: How big was the first guy?<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" My wife and I were sitting in a restaurant when the kid at the next table asked a perfectly reasonable question. \u201cWhy are the oceans salty?\u201d It\u2019s a good question. It\u2019s the kind of question that has occupied geologists, oceanographers, … Continue reading ![\"\"](\"https:\/\/talesofmanythings.com\/blog\/wp-content\/uploads\/2026\/10\/2026-10-16-2-pee-2.jpg\")
<\/p>\n![\"\"](\"https:\/\/talesofmanythings.com\/blog\/wp-content\/uploads\/2026\/10\/2026-10-16-3-ocean-1.jpg\")
<\/p>\n![\"\"](\"https:\/\/talesofmanythings.com\/blog\/wp-content\/uploads\/2026\/10\/2026-10-16-4-evolve-4.jpg\")
<\/p>\n\n
\n
\n
\n
![\"\"](\"https:\/\/talesofmanythings.com\/blog\/wp-content\/uploads\/2026\/10\/2026-10-16-5-cycle.jpg\")
<\/p>\n![\"\"](\"https:\/\/talesofmanythings.com\/blog\/wp-content\/uploads\/2026\/10\/2026-10-16-6-kidneys.jpg\")
<\/p>\n![\"\"](\"https:\/\/talesofmanythings.com\/blog\/wp-content\/uploads\/2026\/10\/2026-10-16-7-peer-review-1.jpg\")
<\/p>\n