There's a great scene in the epic The Hunt for Red October when Captain Marko Ramius's rebel Russian nuclear submarine rises to periscope depth to make visual contact with the heroic US submarine, captained by Commander Bart Mancuso. After a brief morse code exchange, Ramius is requested to acknowledge his affirmative response by sending out a sonar ping. The high-pitched pulse rings through the oceans depths. Typically used by submarines to position the opposition, we are also familiar with a ping used to contact websites.
I think there is also another use, but in the realm of personal relationships. We use relational pings when we are not entirely sure where a friend, colleague, acquaintances is in relation to us. You know the situation, there has perhaps been an argument, some kind of water under the bridge, or a suspicion of something. You then send out a ping in the form of a statement designed to elicit a response that would either confirm or refute your suspicion.
