Now that the search is on for the missing plane in order to retrieve the black box and find out what happened, the focus has shifted to the difficulty of finding it in the vast expanse of the Indian Ocean.
Erik van Sebille writes that it is going to be difficult. For one thing, the signal given out by the box stops after about a month so you have to resort to other methods of detection. The ocean becomes impenetrably dark as you go down to such depths. So how does one overcome these problems?
He says that you have to resort to using sonar signals because sound travels very well in water. But there are challenges. If the source of the signal is too high, you can cover a wide area but the resolution may be too poor to pick out the plane. If it is too low, it can take a long time to cover the search area.
The sonar method and submarines were what was used to recover the Air France black box from the 2009 crash in the Atlantic, but that search took two years. If I recall correctly, people had a much better idea of where that plane went down so this search may take longer unless they find a lot of plane debris soon before it drifts too far away from the crash site.