system
Given the following post, respond as if you're commenting on Reddit:
human
Why is it so difficult to find MH370? Don't we have the technology to find a big metallic wreck at the bottom of the ocean?

Given the properties of water vs. metal, do we not have the type of instrumentation to identify a wreck of that type from the surface, even if it is 2 miles down? What makes this difficult?

I would have thought the depth of the ocean would even work to our advantage as a single boat could target an even larger area of ocean bottom from a particular point on the surface.
gpt
1) You're assuming it's a big metallic wreck.  It's likely a lot of little metallic pieces and a lot of composite pieces spread over miles and miles and miles.  Airlines are not battleships.  They're built as light as possible.

2) There is other metal down there.  Maybe it's ore in the earth's crust.  Maybe it's older wrecks.

3) The ocean is BIG and the ocean is DEEP.  Really, really big and deep.  Sunlight does not reach the bottom of the ocean.  Any kind of microwave scanning like RADAR won't have any more luck penetrating the water.  It's not a vacuum.  It absorbs energy.  It has impurities that block light and radio waves.  That's why submarines use SONAR instead.

4) SONAR detects hard things, not metal things.  (gross simplification)  SONAR still runs into the "the ocean is really, really big" problem.  The most powerful SONAR we have can still only scan a very small part of the ocean floor while retaining any useful accuracy.

So our best tech is SONAR.  Only the best SONAR can reach the deep ocean floor.  When it does, we get a map of various elevations and extra-sonar-reflective hard things that may or may not be very small pieces of MH370 or any other debris.

We also have some magnetic disturbance sensors, but there are lot of magnetic disturbances out there.  If the magnetic disturbance is *moving*, it's probably a ship.  If it's stationary, it could be a lot of barely magnetic stuff or a little highly magnetic stuff.  Including iron ore deposits.  Not terribly useful for finding a debris field that is by now quite settled.