Did the Big Bang mark the beginning of time? Not if we live in a bubble multiverse!

The year 2009 was International Year of Astronomy, and to celebrate, we asked you what you'd most like to know about your Universe in a series of online polls. You came up with seven questions, which we put to world-leading astronomers and cosmologists. Find their answers in seven articles, as well as some podcasts.

We're all on a journey into the future, but can we travel into the past? Find out with Kip Thorne

The obvious answer is 24 hours, but, as Nicholas Mee discovers, that would be far too simple. In fact, the length of a day varies throughout the year. If you plot the position of the Sun in the sky at the same time every day, you get a strange figure of eight which has provided one artist with a source for inspiration.

And what are gravitational waves?

What's the mysterious stuff that makes up 70% of our Universe?

Find out with Martin Rees

Are the unchanging features of the Universe really unchanging?

These are busy times for Plus. Apart from celebrating our 50th issue by putting together a bumper collection of in-depth articles, news and reviews, we're also working on various special projects, some of which have already gone live, and some of which will reach you over the next few weeks and months. Here's a sneak preview of what's in store for 2009...

The world celebrates a great anniversary and Plus joins the party