Yesterday, the Advanced LIGO laboratories in the US detected gravitational waves from two merging black holes some 1.3 billion light-years away. Why is this big news? Well, such a phenomenon has been theoretical over the past two centuries and no technology was sensitive enough to detect it until now. What are they? Uh, short answer: its like any other wave but one we cannot readily observe because its effects are usually so weak. You may be surprised to know gravity itself is largely theoretical because we have been unable to make any observations of it. No, letting go of an apple and watching it fall is not gravity itself but an effect of it. Arguably, this is the first time gravity has been observed which could have a profound impact on science in the 21st century. Yet one thing is for certain, when you really start trying to put all of it together, the Universe is pretty weird. Take a look at BBC’s explainer for more information.