Get all the email conversations(of all the users) for the current time

I know we can get all the email conversation(started within the start and end dates) using aggregate conversation query API.

How can I get all the conversations(would have started anytime and not disconnected\closed) for the current time?

Thank You!

The conversation details query over a period of the past 'x' hours (say from 1 hour ago to current time as the interval) will return historical and in-progress conversations. The presence of a conversationStart field and absence of conversationEnd should indicate the conversation is in progress.