If the Earth's axis of rotation was inclined at 90 degrees what would happen?

The present tilt of the Earth's axis is approximately 23.5 degrees, which results in five significant latitude circles: the Equator, the Tropics of Cancer and Capricorn, the Arctic and Antarctic Circles.

As a result, there are various zones on Earth.

There are no seasons in the tropics, which are located between the Tropics of Cancer and Capricorn; weather systems do, however, bring with them wet and dry seasons.

There are two distinct seasons in the temperate zones between the Tropics and the Arctic Circle: longer, warmer Summer days and shorter, colder Winter nights.

The Arctic regions are covered in ice caps because the warmer Summers are not long enough to melt the ice that is added to by the colder Winters, resulting in 24 hour Summer days and 24 hour Winter nights.

The tropical and temperate zones would form a narrow band around the equator, the Equator, the Tropics, and the Arctic circles would all be in the same location, and each hemisphere would have 24 hour summer days and 24 hour winter nights if the Earth's axial tilt were 90 degrees.

The Antarctic ice cap would undoubtedly be far larger than it is at the current tilt, and the North pole might melt in the summer. There would almost certainly be ice caps over both poles throughout the year.

In response to the events: a.) There would be no seasons on Earth. This is only feasible if there was a zero degree axial tilt.

b.) A frozen equator all year round This would only be conceivable if the planet was perpetually frozen.

c.) Year-round frozen poles This is the most likely scenario, though summertime melting of the North pole is a possibility.

d.) The seasons would be inverted in both hemispheres. Unless the Earth was turned upside down, akin to Venus, this is not possible.

e.) The law of conservation of angular momentum would be broken, making it impossible for any hemisphere to face the Sun permanently.

An extreme seasonal variation would result from tilting the Earth's rotational axis to a 90-degree angle, which would align the axis with the plane of the planet's orbit around the Sun. This would mean that one hemisphere would experience continuous daylight for half of the year, and the other would experience constant darkness. During this period, the Sun would appear to travel across the entire sky throughout the year in the hemisphere experiencing summer, resulting in extraordinarily long days that end in a day where the Sun doesn't set (at the summer solstice) and conversely, extremely long nights that end in a day where the Sun doesn't rise (at the winter solstice) in the opposite hemisphere. As the Earth moves along its orbit, these conditions would gradually reverse over a six-month period.