Okay, let me get this out of the way: white holes are totally science-fiction and cannot and do not exist. So keep that in mind when I say... We might have seen one?
In theory, white holes are black holes that are going backwards. Key words: in theory, because they only exist in hypothetical cases of physics and mathematics. A black hole, as you know, is a giant object that sucks stuff into a single point of infinite density from which there is no escape - we call this a singularity.
But in 2006, we saw an explosion of light out in deep space that we can't explain any other way. And it's even weirder than it sounds.
In reality, a white hole would violate the second law of thermodynamics. This claims that the amount of entropy in the universe can only stay the same or increase; it can never decrease. Entropy is often described as disorder, but it's more like a measure of how many different states that particles in a system can be in at any given moment.
Like, if you have a piano, and you throw it in a woodchipper, you’ve increased the entropy of the piano. Because a pile of chopped-up piano splinters can be in lots and lots of different shapes and styles while still being a pile of splinters.
But these piano splinters can only be arranged in one very specific shape in order to be an actual piano. And you can't load your pile of piano splinters into the woodchipper, and run the thing backwards to get a piano again, right? That would decrease entropy, which is not allowed.
Therefore, black holes are great at increasing entropy! They’re the universe's woodchippers: shredding entire stars into pulp, and leaving only a whiff of radiation. And if white holes existed, they’d have the impossible job of reversing the woodchipper.
So why does anyone think white holes might exist in the first place?
Well, they were first proposed as a kind of mathematical oddity, because of Einstein’s theories of relativity. One of the many endearing quirks of relativity is that it doesn't care whether you play time backward or forward. If time can go in one direction, it should just as easily go in the other.
And if black holes are a thing, then white holes - which are black holes played backward - should also be a thing.
But even though relativity in mathematics claims that time can go in both directions, we all understand that our time in reality is always moving forward. So even if a white hole did somehow occur, it would be incredibly unstable, because the Universe does not like it when you break the laws of physics! A real white hole would probably only last for a few seconds before it collapsed in on itself to become a black hole.
Which brings us back to the explosion we saw in 2006.
Detected by NASA’s Swift satellite on June 14, it was a huge gamma ray burst: the highest-energy type of explosion possible, a million trillion times more energetic than the Sun, and get this - it only lasted 102 seconds.
Scientists believe that gamma ray bursts only last that long during supernovas. But this one, labeled GRB-060614, didn't have a supernova to go with it. As far as we can tell, it was an explosion of white hot light that came from nowhere, and then vanished.
And while white holes remain incredibly, stupendously, ridiculously unlikely... That's pretty much exactly what one would look like.
Some physicists have offered other explanations for what it might’ve been - like a shock wave from neutron star torn apart by a black hole, or maybe two neutron stars colliding (any Muse fans here)?
But events like these only release energy for two seconds at most, never ever as long as a minute and a half.
In the end, all we can gather from this data is that white holes are an impossible possibility. We know from the center of our passionate hearts to the core of our rational minds that there’s no way something can defy fundamental physics and exist. However, the number one rule in science is to question everything: so maybe, just maybe, it’s out there. And until we see another explosion like the one in 2006 that we could hopefully learn more from, we’ll just have to wait and wonder.
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Sources: This story was originally published on SciShow Space. I am republishing a lightly edited version on SkyFeed in light of interest in the subject. Riemers, Ried. "White Holes: An Impossible Possibility." SciShow Space, 6 May 2014. Web video.
Citation: Rovira, Lia N. "White Holes: an Impossible Possibility." SkyFeed, 21 February 2018. Web article.