Where on earth is Elon Musk?

The most central hero of Twitter Inc. - both in his company's history and in social networks - suddenly disappeared from the public eye.

Elon Musk, CEO of Tesla Inc., who recently surpassed 100 million followers on Twitter and is generally an obsessive talker, hasn't posted for nine days. He just disappeared.

A brief hiatus from Twitter is not a cause for concern under "normal" circumstances. But as we've written in this newsletter, a little bit about Musk's current situation is standard these days. Not only has he been tweeting almost non-stop for months, but he's also in the process of buying a service that suddenly disappeared from him for $44 billion. So it's a strange time to be silent.

The last we heard from Musk was at the Qatar Economic Forum on June 21, where Musk reiterated that there were "unresolved issues" surrounding the Twitter deal, including debt financing plans to fund its acquisition and concerns about the number of service bots. The comments seem harmless -- he's said something similar before -- but also fueled speculation that Musk isn't as eager to buy the company as he was when he bid in mid-April.

Musk's absence from Twitter has not convinced his colleagues of the deal — and it hasn't gone unnoticed by his fans or journalists. One Musk fan tweeted last weekend that he saw the Tesla CEO at the company's Gigafactory in Texas, part of an apparent effort to allay fears that something had happened to Musk. "His focus is on work, but he is safe and sound," he wrote.