text: The tilt of the earth's axis (relative to the plane of its orbit around the sun) causes the seasons. If it were tilted more, the seasonal changes would be more pronounced.\n\nIn our winter (in the northern hemispher), when the northern hemisphere is tilted away from the sun, a smaller fraction of the area north of the equator is illuminated by the sun, our days are shorter, and the sun is lower on the horizon. All of these factors result in receiving less of the sun's heat during the winter. (This is also true during the fall, but the winter is colder because the northern hemisphere has already been cooling off during the fall, so by the time winter starts (around December 21), we really start missing the sun's warmth.)\n\nIf the earth were tilted more than 23.5 degrees, then the sun would light an even smaller percentage of the northern hemisphere in the winter, would appear even lower on the horizon, and the days would be even shorter. So winter would be colder and darker.\n\nBut in our summer (and spring), the opposite would occur. The sun would rise higher in the sky, would be up for more hours each day, and would illuminate a larger percentage of the northern hemisphere. In fact, if the earth's axis were tilted 90 degrees to its orbit, then on the day of the summer solstice, every place in the northern hemisphere would have 24 hours of sunlight, and the sun would be directly over the north pole all day. Think what THAT would do for melting the polar icecap. And of course the same thing would happen in the southern hemisphere 6 months later, while the entire northern hemisphere was in the dark for the entire 24 hours.\n\nBottom line: Greater tilt means greater seasonal changes.