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"To convert the pressure to depth, you need to know the density of the water over the entire water column, as well as the local value of gravity, which varies by about half a percent on the surface of the Earth." says Zumberge. And if you try to be really Precisely, it should be noted that the gravity "varies even from a few hundredths of a percent of the surface of the sea to the bottom of the ocean".
The other way to measure depth is to use sonar, but that comes with its own complications. The idea is to send a sound and temporal query to the bottom of the sea. The time it takes for the signal to get back to your boat. You need to know the temperature along the way to get an accurate reading because the sound travels faster in warmer water. In addition, if the seabed is covered with sediment, as with the Deep Challenger, the ping could break this mud and eventually bounce off the rock.
In either case, a measurement will have a margin of error of at least several meters, or even more. "The problem is counterintuitive for an average person, because we live in a time where now, thanks to GPS, we know in a way where everything is," says Cameron. "We know where we are, we know where our car is, we know where our phone is within a meter. So we are really spoiled.
Cameron and Vescovo both used the pressure to calculate the depth of their dives. But while visiting the same area of the Mariana Trench, they agreed to explore different places. Cameron says that it was a plain, but Vescovo found features with sonar. "We made real-time maps of the Deep Challenger Deep a week before we even dive into it. We mapped the loot with multiple scans, which James Cameron did not do, "says Vescovo. "To say that all the functionality is completely flat like a pool table, I do not think anyone can know for sure. What I do know is that our sonar map shows an area of about half a kilometer on a kilometer where it is clear that there is a small bowl. That's how we called him. indicated."
Both explorers also recognize that the margins of error of their depth measurements really overlap. "On the basis of pure mathematics, could we have dipped to the same depth as James Cameron?" Asks Vescovo. "Within the limits of statistical analysis, it is obvious that there are, but it is not likely. But we cut our hair when we talk about 10 or 15 meters out of nearly 11,000.
However, the media took over the story that Vescovo broke Cameron's record, largely because Vescovo's press release perpetuated the story. But all these discussions on recordings miss the critical context of the complex science of depth determination.
Cameron and Vescovo both insist that the most important point is the underfunding and underestimation of the deepest depths of the ocean. The fact that the Vescovo team managed four dives in the Deep Challenger also demonstrates that a custom built submarine can work reliably in rough conditions about ten kilometers away.
And for Vescovo, reaching the deepest point of all the oceans in the world is an incredible achievement, said Andy Bowen, an engineer at the Woods Hole Oceanographic Institution, who collaborated with Cameron. "That each of these dives reaches the record number, I think is much less important than the idea that humans have now demonstrated their ability to reach any part of the world." Ocean with a submersible that can bring real significant improvements in our understanding of the deep ocean, "he adds.
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