Question

What happens if the earth axis become vertical

Answer 1

If the earth weren't tilted, it would rotate like that as it revolved around the sun, and we wouldn't have seasons—only areas that were colder (near the poles) and warmer (near the Equator). But the earth is tilted, and that's why the seasons happen.

Answer 2

Answer:

If the rotational axis of the earth were become vertical to the plane of the ecliptic (the plane that passes through the earth's orbit), several dramatic differences would appear. First would be that the length of day and night would be exactly equal, over the whole planet. There would be no seasons, just one average of the current four. Weather patterns would be very different; much more uniform.