When you drop a tennis ball, it falls to the ground due to what we call gravity. The Earth is very heavy, so it pulls the tennis ball down.If Earth had more material inside, making it even heavier, gravity would pull on the ball more strongly. The pull would also be stronger if we stood on the surface of a shrunken Earth, which remained as heavy as it is. Now, imagine we're deep space explorers in we've found something out in space that is both extremely heavy and very small. It pulls very strongly on anything that comes close to it, so we keep our spacecraft a safe distance away. This mysterious object would pull so powerfully that nothing inside could escape to the outside. A spaceship with the biggest rocket boosters couldn't escape. Even a laser beam, fired straight out at the speed of light, would not make it to the outside. This kind of object is a black hole.What's a white hole?Now imagine we stick around in our spaceship (at a safe distance) and make a movie of this black hole. As we watch it, we'd never see anything escape the black hole. We would instead see the black hole eat anything that came too close. We get lucky: as we watch, the black hole swallows an entire star! Our movie, titled "Black hole eats a star" gets a million views online. But now imagine if we played it in reverse. In the backwards movie, we'd see a very heavy, very small object just sitting there - and then, all of a sudden, spit out an entire star!However, we've never seen a white hole (which is a shame, because they would be really awesome). The reason astronomers think about white holes at all is because of Albert Einstein - a great scientist who is no longer alive, but if you've ever seen him you may remember his crazy hair.
Einstein came up with an excellent idea about gravity, the invisible force that keeps our feet on the ground. His theory describes how black holes work, with their huge gravitational pull.
Einstein's idea also says white holes are possible. So could our universe actually make a white hole? And could a black hole become a white hole? Probably not. Something can be "possible" as an idea, but also extremely unlikely in real life.
White holes are unlikely because they are an "in reverse" kind of thing. Think of breakfast in reverse: your egg unscrambles itself and jumps out of the pan, back into the shell. It's possible, but it would mean time had turned itself around and started running backwards.
As best we can see and measure, time in our universe only flows in one direction: forward. So for now, white holes are just an interesting possibilityIf a variant of interest is then shown to be more infectious, evade protection from vaccination or previous infection, and/or impact the performance of tests or treatments, it is labelled a "variant of concern".
The World Health Organisation (WHO) classified Omicron a variant of concern on November 26 because of its potential to cause higher reinfection rates, increased transmissibility and reduced vaccine protection.
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What is the Omicron lineage?
A lineage, or sub-variant, is a genetically closely related group of virus variants derived from a common ancestor.
The Omicron variant comprises three sub-lineages: B.1.1.529 or BA.1, BA.2 and BA.3.
While the WHO has not given BA.2 a separate classification, the United Kingdom has labelled BA.2 a variant "under investigation". So not yet a variant of interest or concern, based on WHO definitions, but one that is being watched closely.
This is not the first variant to have sub-lineages. Late last year, Delta "plus" or AY.4.2 was reported widely, then Omicron came along.
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