LAST EDITED ON 03-04-14 AT 01:10 PM (EST)Congratulations! You've just destroyed the giant space station! You know -- the one the size of a small moon? The one with the weapon meant to obliterate planets? That thing which was rapidly approaching your world with intent to erase it? Well, you just took it out when it was still a few thousand miles away. You blew that thing up real good.
So congratulations -- on destroying your world.
Let's talk about the power source at the station's core. Think about all the energy it took to run the thing. Now consider that none of it is currently residing in a container and energy can't be destroyed, only converted or dissipated. How much of that shockwave is going to thin out before it hits the atmosphere? Probably not enough to prevent boiling off most of it. What kind of radiation do those who survive that stage get to deal with? What kind would you like?
Now, let's look at the debris. You did not convert every piece of matter back to its component quarks. No, you blew it up. Which means there are some chunks flying outward in an expanding sphere of high-velocity scattershot shotgun spray. Chunks that came off something which started as the size of a small moon. How big are some of those chunks? Big enough to survive falling through what little is left of the atmosphere. Guess how much damage they'll do when they hit. Picture what too many will do to the tectonic plates. Consider dinosaurs.
Nice work, hero. Really.
Except that -- somehow, none of the above happens. You blow up the giant space station -- and life below goes on as before. There are no extra fatalities. Apocalypse You just doesn't manifest. In the end, there is
http://tvtropes.org/pmwiki/pmwiki.php/Main/NoEndorHolocaust
and why should you care if it doesn't make any sense, as long as everyone important lived?
This trope comes into play when any event which should by all logic and reason cause a huge number of fatalities does not. Every building the villains bring down is empty. The bad guy in his rampage can hit hard enough to break steel, but any person punched just takes a nap. Every bullet fired from that machine gun into the crowd missed. And all the explosion-driven effective mass of a small moon plus the energies contained within? Never heard from again.
It's one of those tropes which, if you're lucky enough to be on the receiving end of it, you don't want to think about too long. The universe might retroactively catch on.