system
Given the following post, respond as if you're commenting on Reddit:
human
Why is so much easier to balance on a moving bike than a stationary one?

I imagine there's some physics involved here...does the momentum somehow make it easier to keep going straight than to fall over?
gpt
While you are moving, you can make corrections in your trajectory (by adjusting your balance or shifting the handlebars) in order to keep your balance.  At slow speed, the correction required becomes larger (since you are moving over a smaller distance), hence why it is easier to balance a bike at speed.  

When you are stationary, you can't make corrections at all, and you have to balance through other means.  Most of these involve turning your front tire to the side and being able to move backwards and forwards (either from being on a hill or riding  a non-freewheel bike).