system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When jump staring a car, why is it important to connect negative to ground, instead of negative to negative directly? Shouldn't that be the same, electrically?
gpt
It is, but when you make the final connection of them all, there is a risk of arcing, which you don't want to happen near a battery that can produce explosive gases. 

That's also why you connect positive first. If you drop the positive onto either car chassis accidentally, there will be a spark if the negative is already connected.