Thread by @DanEnRoute

One thing to keep in mind about the search for Titanic submarine is how difficult it is to *see* underwater. In fact it's impossible. Here's how you search instead. 1/ thread

Micro radio waves are used by satellites to make maps of land. The bounce down from space and then bounce back up. But those waves don't work in water. They don't bounce back.

So the only way 2 see underwater is actually to *hear* underwater. Sonar, in other words, that sends sounds down and documents their return. This is extremely time intensive and expensive, which explains why we have maps of Mars but not a full map of ocean floor.

Seafloor mapping is done with sonar rigs that hover a few hundred feet off the ocean floor, which requires towing a rig at consistent altitude for house. This is very difficult for a surface ship. Requires consistent speed and, at deep depths, a VERY long cable.

Seafloor mappers and shipwreck hunters refer to this as "mowing the lawn." Basically running huge transects back and forth for days, sometimes weeks, to get a semi-accurate "picture" of a small area of seafloor.

This is one of the reasons it took so long to find the Titanic (73 years), even though the whole world knew its SOS coordinates. Even searching a small area by sonar is extremely time-intensive and expensive. And that's not accounting for conditions of the sea surface.

It won't surprise you to learn that the north Atlantic is an especially punishing stretch of ocean. Very rocky waves, lots of storms, and of course icebergs that float down from Greenland. I've heard conditions are *decent* at the moment during the search, but still not ideal.

What's more, the texture of the seafloor is very diverse. Just like on land, there are big rocky outcrops, giant canyons, valleys, and stretches of mud. Sonar can't easily distinguish between a submarine-shaped rock and a real submarine.

For this reason in the 70s & 80s several people searching for the Titanic thought they found it but they were just rocks. One of them, Texas oilguy Jack Grimm, actually found a rock the same size and dimensions of the Titanic propellor (what are the odds?).

Of course the backdrop for all of this is pitch black and the most punishing water pressure on earth (6000 pounds per square inch, like balancing a loaded SUV on your pinky finger). Everything is exponentially more difficult 12,500 feet deep.

Someone asked if the North Atlantic is the worst place on earth to shipwreck or get lost in a submarine, and the answer is, it's close, but there's an even worse place...

Point Nemo in the South Pacific, the farthest spot on earth from a major landmass. Add in rough seas, near-polar temperatures, and the fact that Point Nemo is the unofficial dumping ground for satellites falling out of the sky, and getting lost there is almost guaranteed death.

I could go on for days with stories like this. In fact I did last year in my book SINKABLE: Obsession, the Deep Sea, and the Shipwreck of the Titanic. If you get audiobook I'll even read it to you myself. =) /fin