Ever put two hamsters in a cage together and then, come next morning, wake up to find only one fat, innocent-looking hamster? This is the same thing. Only the hamsters are galaxies.
No, they're not ... they're not shaped like hamsters. It's an analogy. Jesus.
Hey. HEY. Look back at the stars. Goddammit.
This phenomenon is called galactic cannibalism, and that's one of those rare scientific names that is as plainly accurate as it is bowel-seizingly terrifying. Basically, smaller galaxies succumb to the gravity of a bigger one and are slowly absorbed into it, thus adding to its mass and making it even larger, so it can eat more galaxies. It's a dog-eat-dog universe out there. Hell, even our own Milky Way is known to indulge in this behavior every once in a while.
Our galaxy, plotting douchebaggery.
How It Will Get Us:
It's not a matter of how; it's a matter of when. See, one of the bigger galaxies that's heavily into eating its kin is Andromeda. You know, our closest neighbor Andromeda -- the "way the hell bigger than our galaxy" Andromeda. See that picture up there? It's not just there to fill space. No, that's a computer simulation of what Andromeda is going to do to us someday. We, as a galaxy, are going to be eaten.
Via W Schoening/V Harvey/REU/NOAO/AURA/NSF
This will cause the two galaxies to slowly compress into a single mess of stars within the next 3 billion years or so, throwing us to the very outskirts of the new Galactic Scramble, or maybe even transforming our very own sun into one of those hypervelocity stars.
And somehow, those are the "nicer" options. Otherwise, our whole solar system could just be devoured by exploding galactic gas or crushed by a colliding Andromedan equivalent.
We spend all that money fixing the Hubble telescope and it repays us with promises of doom.
4Vacuum Metastability Event
Quantum physics, the study of "dual particle-like and wave-like behavior and interaction of matter and energy," is science-talk for "a bunch of far-out shit, man." The field has sprouted some of the more mind-blowing theories of life, the universe and everything. One of the more disconcerting ones is the suggestion that we (as in "we, everyone and everything in the universe") may exist in a false vacuum state. A lot of abstract terms such as "bubbles" and "vacuum levels" are involved, but in layman's terms, this means the universe was built from dodgy parts and ended up with an energy level too low for more than temporary sustenance. Therefore, at any given moment, it could call it quits and succumb to the pressure, only to be replaced by higher energy levels.
Via Wiki Commons
The End of All Things, in convenient chart form.
How It Will Get Us:
It's called a vacuum metastability event, which is what happens when the energy levels of our particular universe's vacuum go sour. Should this happen, the ensuing collapse would level Earth with a light-speed blast before any of us even had time to blink. It's probably a good thing that we don't survive long, because after that, things get really bad. All the laws of physics will go psychedelic on your poor, obliterated ass, until they eventually mutate into a completely new, improved set. There will still be a universe, just not the universe. In time, there may even be life -- just not the sort we'd be able to comprehend, even if our brains hadn't been smashed into inverted color parties riding the crest of an infinite mathwave.
It's kind of like surfing, only your entire body is slowly dissolving into ether, and everything tastes mauve.
In other words, quantum physics is basically telling us that Cthulhu and the Great Old Ones could come knocking at any minute now. That's right: Lovecraft was a scientist all along, just coldly documenting the facts as he saw them.
Via Howard Phillips Lovecraft
He's clearly terrified of whatever is immediately behind the photographer.