Mariana Trench First Measured Using Good Old-Fashioned Rope.

It's a cliche: We know more about the surface of the moon than our planet's ocean floor.

Reason? It is because we can study the surfaces of Moon using light or radio waves. Radars installed on satellites map surfaces to give an accurate image of terrains, even if distant, but if a surface is covered in water, mapping isn't doable as the methods don't work underwater.

But here is an interesting factoid I read the other day - Earth's highest peak, deepest valley, and flattest plains are underwater.

My question was: How did they find out? Who measured it? When?

And again... how?

Mariana Trench is in the Pacific Ocean and it is the deepest part of our oceans. It is 36,201 ft deep - that is almost 7 miles deep. It's hard to imagine such depth, but this comparison may help: If you were to pick up Mount Everest and place it in Mariana Trench (say, upside down) you would still have 7000 feet of water above the peak. That's how deep it is... and its length and width ain't shabby either. The Mariana Trench is 1550 miles long and 45 miles wide. It is in a crescent shape, east of the island of Guam.

And... we knew about Mariana Trench back in 1875.

So, how did scientists measure the depths of Mariana Trench 145 years ago?

I mean, seriously. How?

Sometimes, as the old saying goes, truth is stranger than fiction. Much, much stranger.

Four days before Christmas in 1872, H.M.S Challenger set sail from Portsmouth in England. H.M.S Challenger was originally a warship. It carried 17 guns and had an engine capable of 1200 horsepower. Now it was defunct. The warship had been refurbished to carry out ocean research. The researchers fit a laboratory onboard, which from every account was impressive indeed. The guns were removed and in their place were workrooms and storage space.

See the images of the ship and its laboratory and read about it here.

It was scheduled to go around the globe, a three-year trip, to map depths, geography, and temperatures, and examine the life that may or may not survive under the ocean.

Here is what I just read in the NOAA website -

The 1870s voyage of HMS Challenger lasted 1,000 days and covered more than 68,000 nautical miles. Many consider it to be the first true oceanographic expedition because it yielded a wealth of information about the marine environment. Those aboard identified many organisms then new to science, and they gathered data at 362 oceanographic stations on temperature, currents, water chemistry, and ocean floor deposits. The scientific results of the voyage were published in a 50-volume, 29,500-page report that took 23 years to compile. Specialists in numerous scientific disciplines studied the collections and data, and helped produce the reports. Also, the reports written by members of the Challenger expedition provided rich descriptions of the flora, fauna and cultures of the lands visited. Photography—new at the time—was highlighted as well, along with scientific illustration.

And this - H.M.S Challenger - was the first to measure the depths of Mariana Trench.

How? Well. The ship carried with it 180 miles of Italian hemp rope.

The team (six scientists led by Dr. C. Wyville Thomson, 21 naval officers, and 216 or so crew) would drop the rope every few days to measure the depth of the ocean at that specific point. Imagine the tedium. I could weep. Every few days, if you're the crew, you unroll and let down a length of rope, then you roll it up again. You sample the bottom of the ocean. You bring up a haul of fish and shells and mud and undefined organisms. The scientists measure and draw and illustrate and pickle and preserve... while you go back to spooling and unspooling that rope... over and over and over for 1000+ days... and across the world - literally.

As Kate Golembiewski writes in her amazing and interesting article:

They did this all the way around the world, from England to the North Atlantic and the Caribbean, down to Brazil and east to the southern tip of Africa. They dipped down within sight of Antarctic icebergs and then headed up, hugging Australia’s southeast coast and making their way through Micronesia and Asia, then east across the Pacific, tracing South America and arriving back in England on May 24, 1876, three and a half years after the journey’s start.

No wonder the ship lost a good part of their crew. When they returned, only 144 of the 216 remained. Rest had abandoned ship, fallen ill, quit, or died.

It was one of the most important ocean expeditions in our history and it found depths in our oceans that were previously unimagined - and it measured these depths with a hemp rope.

A giant hat tip to the crew.