I love sci fi movies. When done right, they make you think about the world around you and open your mind to a new and exciting future. When done wrong, you still get some pretty cool special effects. The problem with science fiction movies is the "science" part. You see, the whole point of science fiction is to take the technology that we have, right now, and extrapolate it. Thus, the technology in science fiction movies doesn't exist by virtue of the genre. It usually proves as just a fun thought experiment for scientists and inventors alike. Personally, I'm fine with a science fiction movie showing some ridiculously cool piece of technology and not explaining how it works. Often times, movie writers are not scientists and by leaving a void, fans who are scientists can chime in with their own hypotheses which are, more often than not, really interesting. And I think that speculation in the fan community really adds to the experience of the sci fi piece. However, when the writers try to shoehorn in some scientific explanation to make it more "realistic" it can have catastrophic effects... if they do it wrong. Which they did in Ant Man.
Caution: there are spoilers ahead. If you haven't seen Marvel's Ant Man, go watch it. If not for the way it warps your perception with stunning visual effects, then for the way Michael Pena tells stories. Moving on...
Ant Man's (Hank Pym, and then Scott Lang) suit allows him to shrink down to the size of ant, obviously. I didn't have a lot of hope for the idea, especially as a superhero, but they pulled it off and it was awesome. It was awesome until they decided to explain what the suit does to get down that small... twice. In case you missed it, the suit is just a protective coating for the Pym Particle (the red liquid, synthesized into the yellow liquid) which penetrates the subject (Pym, Lang, or lamb) on a sub-atomic level. The particle, according to Pym, reduces the space between the atoms. It sounds like a fairly straight forward explanation, actually: there is a lot of space between atoms, space that is mostly empty. And scientists, notably at the University of Colorado in Boulder, have already been squeezing atoms together. You see, in solid objects, the atoms are bonded together, but not tightly. There's a lot of wiggle room between the atoms. So, what happens when you squeeze those atoms together. Yes, they take up less space, but moreso than that, they get cold. Like really cold. The wiggling between atoms is essentially what heat is. More heat = more wiggling. When you heat stuff up, it wiggles so much that the bonds break and it either evaporates or explodes (depending on what it is). So, when you take away all the wiggle room for an atom, you're going to get something very very cold. When things get so close together that there is no more wiggling, that's what scientists call Absolute Zero. We're nto entirely sure what happens at Absolute Zero, because we haven't actually achieved it. The University of Colorado has gotten within two degrees (last time I checked) but the hypothesis is that everything just sorta stops there. Presumably, if the atoms of Scott, Hank, or discount Lex Luther got close enough together, they would freeze to death well before hitting Absolute Zero.
Later on in the movie, we learn about Wasp and how she had to go "sub-atomic" in order to turn of a nuclear warhead. But, Hank said that you should never go sub-atomic (which obviously means they're gonna do that later) because you just keep shrinking and shrinking and shrinking forever and can't grow back. As any physicist would know, as things get smaller and smaller, the laws that guide them get crazier and crazier. For the sake of the movie, let's assume that the Pym Particle can actualy reduce a mass to the size of a single atom and even smaller. The affects of that increase of density are a lot crazier than that iTunes Visalizer Scott fell through in the movie. About a hundred years ago, this dude named Karl Schwartzchild was doing some calculations with his buddy Einstein. One of the things he wanted to figure out was how black holes work. Black holes, usually collapsed stars, are incredibly dense, basically they are a lot of stuff taking up very little space, which makes their gravity go absolutely bonkers. Schwartzchild figured out that anything can become a black hole, you just need to make it small enough. He even figured out the relatively simple calculation to figure that out: radius = two times the gravitational constant times the mass of the object, divided by the speed of light squared. Or: r=2GM/c^2. The radius in that equation is for the even horizon of the black hole, the point at which nothing can escape the great suckitude. Seeing as Hayley Lovitt played Wasp in the movie, we can calculate using her weight (125 lbs) to see just how small she has to be to collapse into herself and create a black hole. and she only has to be 8.45x10^-26 meters. That's small enough that the metric system doesn't even have a prefix for it (the closest we can get is .00845 yoctometers) but it isn't that small at all, compared to where Pym's science can go. Just for reference, the tiniest thing we know currently is about 1.6x10^-35, so this is still well within the realm of reality (except for that first part). To fit into the casing of the nuclear bomb that they were trying to take care of, she only needed to shrink down to about 100-200 picometers (200x10^-12) depending on what it's made of (I don't want that on my google history). And it only took a matter of seconds to get to that size. If she keeps shrinking at the same rate, then in about twice that amount of time she would be a black hole. And that's still only a matter of seconds. Before Hank can even let go of the warhead, his wife is already sucking matter in left and right. And granted, she's a really tiny black hole, the more she sucks in, the more she'll grow. I'm no astrophysicist, but I'm guessing she'll be able to suck up the whole planet in a matter of minutes. That's right, according to the MCU, Wasp is responsible for the destruction of the planet, not the rest of the Avengers, and certainly not Thanos (obviously because he's taking too long).
Also, I get that they were tying it in to Civil War (and they had a nice Spidey reference in there), but did they really have to bring Bucky back? What's he there for?