What's your idea of a good time? What about dancing in a rainy field with one hundred and fifty thousand other people while a famous rock band plays on a stage so far away that the performers look like ants? It may sound strange but that is what many hundreds of thousands of young people in the UK do every summer. Why? Because summer is the time for outdoor music festivals. Held on a farm, the Glastonbury Festival is the most well-known and popular in the UK. It began in 1970 and was attended by one thousand five hundred people each paying an admission price of ￡1—the ticket included free milk from the farm. Since then the Glastonbury Festival has gone from strength to strength--in 2004 one hundred and fifty thousand fans attended, paying ￡112 for tickets to the three-day event. Tickets for the event sold out within three hours. Acts included veteran (老的、著名的) superstars, such as Paul McCartney and James Brown, as well as new talents, like Franz Ferdinand and Joss Stone. Although many summer festivals are run on a profit-making basis, Glastonbury is a charity event, donating millions of pounds to local and international charities(慈善事业). Glastonbury is not unique in using live music to raise money for global poverty. In July of this year, the Live 8 concerts were held simultaneously (同时) in London, Pads, Rome and Bedim Superstars, such as Madonna, Sir Elton John and Stevie Wonder performed in order to highlight international poverty and debt. What does the author mean by 'the Glastonbury Festival has gone from strength to strength'?