In addition to looking for evidence of time travelers online, the researchers also reached out to any potential time travelers directly by writing a post on an online message board asking people from the future to tweet using one of two pre-specified hashtags before a certain date that had already occurred. The hashtags (#ICanChangeThePast2 and #ICannotChangeThePast2) were aimed at letting time travelers tell the researchers about the nature of time travel and whether actions taken while traveling in the past can change events in the future. Famed physicist Stephen Hawking attempted something similar in 2012 by throwing a party for time travelers but only sending out invitations after the fact. ‟I sat there a long time,” Hawking told an interviewer, ‟but no one came."