Megalodon’s actual size, recalculated
A new study bases its calculations on more than the great white shark.
- Previous estimates of the megalodon's size were based solely on its teeth compared to the star of "Jaws."
- The prehistoric monster is as closely related to other sharks.
- Imagine just a dorsal fin as tall as you are.
For anyone already terrified by ferocious sharks — few of them actually are, of course — the prehistoric megalodon, Otodus megalodon, goes several steps beyond a nightmare. Not much is known about the animal that roamed the seas from 23 million to about three million years ago. The most definitive fossils are triangular teeth that are larger than a human hand, really not much from which to extrapolate a complete picture of the shark. Even so, they suggest a gargantuan predator. Have you seen "The Meg"?
Now a new, open-source study from the University of Bristol and Swansea University published in the journal Scientific Reports purports to have figured the megalodon's true dimensions, and they don't disappoint.
What’s different about this analysis
Previous estimates of the megalodon's size have been based on the great white shark, which can exceed 20 feet in length — that's about half the length of an average school bus. The idea has been, essentially, that since a great white's tooth is about 2 inches long — the biggest one ever found is 2.5 inches — and most megalodon teeth seem to be in the neighborhood of six inches — the largest one found is 7.4 inches — then the megalodon must have been about three times as big as a great white. The suggestion is that if great whites can bite with two tonnes of pressure (4400 pounds), then the megalodon's bite must have been significantly more powerful.
This may not be a completely fair comparison, however, according to one of the study's authors, Catalina Pimiento of Swansea. She tells University of Bristol that "Megalodon is not a direct ancestor of the Great White but is equally related to other macropredatory sharks such as the Makos, Salmon shark and Porbeagle shark, as well as the Great white." To arrive at their measurements the researchers, "pooled detailed measurements of all five to make predictions about Megalodon."
To try and work out the proportions of the prehistoric shark based on this larger group of contemporary sharks, the researchers investigated how their bodies change as they mature. "Before we could do anything," says co-author Mike Benton, "we had to test whether these five modern sharks changed proportions as they grew up. If, for example, they had been like humans, where babies have big heads and short legs, we would have had some difficulties in projecting the adult proportions for such a huge extinct shark."
It turned out, surprisingly, that though these sharks get larger as they grow up, their body proportions don't really change much. "This means we could simply take the growth curves of the five modern forms and project the overall shape as they get larger and larger — right up to a body length of 16 meters," adds lead author Jack Cooper.
Cooper has always been, as he puts it, "mad about sharks." He's worked and dived, in a steel cage, with great whites. He enthuses, "It's that sense of danger, but also that sharks are such beautiful and well-adapted animals that makes them so attractive to study."
The megalodon’s revised measurements
Credit: Reconstruction by Oliver E. Demuth/Scientific Reports
The study proposes the following approximate measurements for a full-grown megalodon:
- Length: about 16 meters (52.5 feet). A full-size school bus is just 45 feet long
- Head size: about 4.65 meters long (15.3 feet)
- Dorsal fin: about 1.62 meters tall (5.3 feet). A person could stand on the back of a megalodon and be about as tall as the fin.
- Tail fin: about 3.85 meters high (12.6 feet)
Let's just hope this sucker is really extinct.
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The idea of 'absolute time' is an illusion. Physics and subjective experience reveal why.
- Since Einstein posited his theory of general relativity, we've understood that gravity has the power to warp space and time.
- This "time dilation" effect occurs even at small levels.
- Outside of physics, we experience distortions in how we perceive time — sometimes to a startling extent.
Physics without time<p>In his book "The Order of Time," Italian theoretical physicist Carlo Rovelli suggests that our perception of time — our sense that time is forever flowing forward — could be a highly subjective projection. After all, when you look at reality on the smallest scale (using equations of quantum gravity, at least), time vanishes.</p><p style="margin-left: 20px;">"If I observe the microscopic state of things," writes Rovelli, "then the difference between past and future vanishes … in the elementary grammar of things, there is no distinction between 'cause' and 'effect.'"</p><p>So, why do we perceive time as flowing <em>forward</em>? Rovelli notes that, although time disappears on extremely small scales, we still obviously perceive events occur sequentially in reality. In other words, we observe entropy: Order changing into disorder; an egg cracking and getting scrambled.</p><p>Rovelli says key aspects of time are described by the second law of thermodynamics, which states that heat always passes from hot to cold. This is a one-way street. For example, an ice cube melts into a hot cup of tea, never the reverse. Rovelli suggests a similar phenomenon might explain why we're only able to perceive the past and not the future.</p><p style="margin-left: 20px;">"Any time the future is definitely distinguishable from the past, there is something like heat involved," Rovelli wrote for the <a href="https://www.ft.com/content/ce6ef7b8-429a-11e8-93cf-67ac3a6482fd" target="_blank"><em>Financial Times</em></a>. "Thermodynamics traces the direction of time to something called the 'low entropy of the past', a still mysterious phenomenon on which discussions rage."</p>
The strange subjectivity of time<p>Time moves differently atop a mountain than it does on a beach. But you don't need to travel any distance at all to experience strange distortions in your perception of time. In moments of life-or-death fear, for example, your brain would release large amounts of adrenaline, which would speed up your internal clock, causing you to perceive the outside world as moving slowly.<br></p><p>Another common distortion occurs when we focus our attention in particular ways.</p><p style="margin-left: 20px;">"If you're thinking about how time is <em>currently</em> passing by, the biggest factor influencing your time perception is attention," Aaron Sackett, associate professor of marketing at the University of St. Thomas, told <em><a href="https://gizmodo.com/why-does-time-slow-down-and-speed-up-1840133782" target="_blank">Gizmodo</a></em>.<em> "</em>The more attention you give to the passage of time, the slower it tends to go. As you become distracted from time's passing—perhaps by something interesting happening nearby, or a good daydreaming session—you're more likely to lose track of time, giving you the feeling that it's slipping by more quickly than before. "Time flies when you're having fun," they say, but really, it's more like "time flies when you're thinking about other things." That's why time will also often fly by when you're definitely <em>not</em> having fun—like when you're having a heated argument or are terrified about an upcoming presentation."</p><p>One of the most mysterious ways people experience time-perception distortions is through psychedelic drugs. In an interview with <a href="https://www.theguardian.com/books/2018/apr/14/carlo-rovelli-exploding-commonsense-notions-order-of-time-interview" target="_blank"><em>The Guardian</em></a>, Rovelli described a time he experimented with LSD.</p><p style="margin-left: 20px;">"It was an extraordinarily strong experience that touched me also intellectually," he said. "Among the strange phenomena was the sense of time stopping. Things were happening in my mind but the clock was not going ahead; the flow of time was not passing any more. It was a total subversion of the structure of reality."<br></p><p>It seems few scientists or philosophers believe time is completely an illusion.</p><p style="margin-left: 20px;">"What we call <em>time</em> is a rich, stratified concept; it has many layers," Rovelli told <em><a href="https://physicstoday.scitation.org/do/10.1063/PT.6.4.20190219a/full/" target="_blank">Physics Today</a>.</em> "Some of time's layers apply only at limited scales within limited domains. This does not make them illusions."</p>What <em>is</em> an illusion is the idea that time flows at an absolute rate. The river of time might be flowing forever forward, but it moves at different speeds, between people, and even within your own mind.
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