What would happen if the earth's axial tilt was zero?
Both North and South Poles would forever be exposed to Sun. Sans an extremely small polar caps, there would be constancy of (12+ h) daytime and (12- h) nighttime.
The Sunlit hemisphere of Earth is always a little more in surface area than that for the hidden side. So, for zero tilt, the poles would be just within Sunlit hemisphere. Of course, Sun could bee seen from poles at the horizon only, throughout the whole year. The question is seemingly simple. Yet, my answer is not so.