To promote his brother's book, John Green started a surprise campaign to promote Hank's novel, including renting several billboards near their hometown of Orlando, sponsoring four FIRST robotics teams and a college rugby club in Montana, and making An Absolutely Remarkable Thing the official training kit sponsor of AFC Wimbledon, among other advertisements. John also joined Hank for six of his book tour stops. At the end of 2018, John Green chose to leave social media for a year, including Twitter, where he had more than 5 million followers. In January 2019, Green wrote an op-ed for The Washington Post on his decision, saying "I had noticed over the past couple of years that my attention had become more fractured. I found it harder to lose myself in a book, for instance, without feeling the urge to check my phone or open my laptop." In December 2022, Green exited the platform in response to the policy changes made after Elon Musk's acquisition of Twitter. In March 2019, Green moderated a discussion with former First Lady Michelle Obama on her memoir Becoming as part of a YouTube-sponsored event titled "BookTube". In April 2019, Green recorded a live version of the podcast Harry Potter and the Sacred Text at the Indianapolis Central Public Library. Green gave a virtual commencement address to all graduates in May 2020 during the beginning months of the COVID-19 pandemic. Green created a TikTok account in 2020, which has over 2 million followers and 48 million views . In September 2021, Green continued his advocacy for refugees, writing an op-ed in The Independent on the need for education for refugee children. In October 2022, Green gave the opening lecture at Harvard University's 2022 William Belden Noble Lecture series, titled "How the World Ends". In January 2023, John and Hank announced that Crash Course would be offering college courses on YouTube, in continued partnership with Arizona State University (ASU) and Google. The course content would be viewable online for free, with the full online course, which would be led by ASU faculty and included direct interaction, available through ASU for . Finally, students would then have the option to spend $400 to receive college credit for the course that would be transferable to any institution that accepts ASU credits. Influence and reception Books Green's books have been translated into 55 languages with more than 50 million copies in print