Tech rivals Elon Musk and Mark Zuckerberg often outdo each other in business. They want to have the most money or attract the most followers. Their rivalry intensified this week. The two multi-billionaires agreed to fight in a "cage match". The reported punch-up between the richest and tenth richest men in the world is because Zuckerberg wants to create a site to rival Twitter. The fight could take place in a mixed martial arts cage.

The Ultimate Fighting Championship could arrange the fight. It said the event could be the most profitable and "the biggest fight in history" and that it would "break all pay-per-view records". People might have to pay $100 to watch it. It is unclear who is favourite. Zuckerberg recently won gold in a martial arts tournament. Musk has a secret weapon that he calls 'the Walrus'. He sits on top of his opponent and does nothing.