system
Given the following post, respond as if you're commenting on Reddit:
human
[Ant-Man] How the hell do Pim particles work?

They shrink the space between atoms, sure, but do they also alter mass? Is Hank Pim carrying around a full-weight tank in his pocket? How is Scott Lang not weighing down the barrel of the gun he’s running on as though a full-grown man had jumped on the front of a couple pounds of metal and plastic? How does he exert so much force upon hitting the weapon’s wielder? In Civil War, when he grows to Iron Giant size, why does he have so much more impact than a normal-sized man, and why is he slower?
gpt
He has some control over things like the square-cube law. Normally he does reduce his mass, but he can bring it back if he feels the need to punch someone hard enough to knock them out. He can even extend the increased strength from the square-cube law to the skin and jaw of the person he's punching so he doesn't just poke a hole with his needle-sized fist.

The reason stuff seems to happen in slow motion when it's bigger is that gravity doesn't scale. If you drop a one-centimeter marble five meters it will take about one second to hit the ground, but if you drop a four-centimeter ball twenty meters it will take two seconds instead of one second. So it looks like it's happening at half speed. Hank Pym figured out how to make it reduce gravity when shrinking so that he can walk normally, but he was only just beginning to work with growing things and it seems he hadn't figured out how to reverse that and increase gravity.