7 Simple Questions That Scientists Still Can't Answer

7. Is The Universe Very Big Or Very Small?

We can measure a lot of the things in the universe with astonishing precision. The Earth, the Sun, The Milky Way, we've got them nailed. Something else we can pretty accurately measure is the size of the observable universe. This is the portion of the universe that we can see, extending in a sphere around our planet for around 46.5 billion light-years. The thing is that, by definition, we can't observe anything outside of it. There is an impenetrable cosmic horizon that we just can't see past. Often when we talk about the size of the universe, the observable universe is generally assumed to be a tiny part of it. However, there's nothing to say that the universe extends any further than the cosmic horizon at all, this might actually be all there is. Of course, because the observable is centered on the observer, we could always set off from Earth to see what we can see - like sailing towards the horizon. Scientists suspect that the universe is indeed much bigger than it looks, largely because the cosmic microwave background is so uniform, as opposed to tailing off at the "edges". If this is that case then the universe is very big, perhaps infinite, but the observable universe, if that's all there is, is very small. It's quite probable that we'll never find out the answer.