IF SPACE IS NOTHING, HOW DO WE KNOW IT'S EXPANDING?
No one knows exactly how big the whole Universe is.
We can’t see it all from here on Earth, even with the best telescopes, but we can estimate the size of the observable Universe, a good (albeit mind-blowing) start.
‘The latest observations indicate that the Universe is at least 91 billion light-years or 8.6 million billion billion kilometres across,’ Dr Sarah Bosman, a postdoctoral research assistant at UCL, tells Metro.co.uk.
Even at this vast and bewildering size, the whole Universe is likely to be much, much bigger (more on that later).
What’s more, evidence suggests it’s expanding.
But will it keep getting bigger forever? What does ‘bigger’ mean for a thing that might already be infinite?