OK, after seeing a couple of fireworks ads the other day, several of us got talking about what you could do to put on a really big fireworks display. Things got pretty silly pretty quickly, but the question that came up was, when the Andromeda galaxy celebrates its independence day in the year 201,776, what might they use? Or, to turn it into a General Question, “What is the biggest explosion someone could reasonably expect to see?”
Here’s a list I came up with. (Bear in mind that I only had enough physics to get through Engineering back in my college days and am at best an armchair astronomer, so I’m probably wrong somewhere on this list.)
Conventional Explosives - Just standard fireworks scaled up a few orders of magnitude. I know the military has some really big bombs but I’m not quite sure how far they go. I suspect there is a practical upper limit on how big a conventional explosive can be because (I suspect) past a certain point the part of the explosive that has already gone off blows the rest of it apart before it can react.
Nuclear Explosives - Most people’s idea of a really big explosion. (The conversation that inspired this post got stared when someone wondered if you could produce a country-wide “fireworks display” by setting off nuclear devices in orbit). I suspect the upper limit here would be that, past a certain point, only so much of the fissionable/fusionable material could react before the force of the explosion blew it apart. (And, yes, I know that a star can be thought of as a fusion reaction that keeps exploding, but it doesn’t exactly match most people’s idea of an “explosion”.)
Supernova - Now these are big. I assume that the bigger the star, the bigger the resulting supernova. But, past a certain mass you don’t have a star anymore; you have a neutron star/black hole. So that marks the upper limit there.
Collapsing Black Holes (?) - Here is where we are getting beyond my knowledge level. If I remember correctly, Black Holes can somehow slowly lose mass. When its mass drops below a certain level, it ceases to be a Black Hole and suddenly all the matter and energy within it are released at once. I would guess this is bigger than a Supernova but I don’t know if this is even a valid theory anymore.
The Big Bang - Well, there was only one of these and I doubt anyone was around to see it, so it doesn’t count.
And, some things I didn’t know where to put them.
A) Matter/Antimatter Collison - I know this releases a lot of energy, but I don’t know how big it could get. If, for example, a matter planet and an antimatter planet were to collide, they would start reacting when they first touched. At some point, the energy release would push them apart again. (Or, for that matter, gravity may tear them apart before they hit, which gives us a bunch of small explosions instead of one big one.) I would guess this would fall somewhere between 2 and 3 above.
B) Neutron Stars - Do these do anything? I know there is an energy release as matter falls into them but beyond that I really don’t know. (That’s what a Pulsar is, isn’t it? Not sure if that would count for our explosion definition or not.)
So, anyone have any ideas or input? I’ve only got a few days until the 4th, so I need to start working on my plans…