Would every latitude on earth have the chance of seeing the sun directly over head is the Earth was tilted on it's axis by 90 degrees?

Answer 1

Only the latitudes at 0 and 180 degrees and those at 90 degrees would

have the chance of seeing the sun directly over it's head if the earth was

tilted on it's axis by 90 degrees.

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Answer #2:

Thgere is no such latitude as "180 degrees".

If the Earth's axis were in the ecliptic plane and the Earth rotated "on its side",

then each pole would point directly at the sun at one moment each year.

In order to follow through the annual saga, let's say that the north pole pointed

directly at the sun on January 1, just for an example. Then . . .

-- On January 1, the sun would be directly overhead at the north Pole. All

northern latitudes, from the equator to the north pole, would have 24 hours of

daylight. All southern latitudes, from the equator to the south pole, would have

24 hours of dark.

-- From January 1 to the end of March, the sun would move slowly, from

overhead at the north pole, to overhead at the equator. The length of daylight

everywhere in the northern latitudes, between the equator and the north pole,

would gradually decrease, from 24 hours to 12 hours. The length of daylight

everywhere in the southern latitudes, between the equator and the south pole,

would gradually increase, from zero to 12 hours. Every northern latitude woud

have the sun directly overhead once during these 3 months. By April 1, every

place on Earth would have 12 hours of daylight and 12 hours of dark.

-- From April 1 to the end of June, the sun would move slowly, from overhead at

the equator, to overhead at the south pole. The length of daylight everywhere in

the northern latitudes, between the equator and the north pole, would gradually

decrease, from 12 hours to zero. The length of daylight everywhere in the

southern latitudes, between the equator and the south pole, would gradually

increase, from 12 hours to 24 hours. Every southern latitude woud have the sun

directly overhead once during these 3 months. By July 1, the northern latitudes

would have zero daylight, and the southern latitudes would have 24 hours of it.

-- From July 1 to the end of September, the sun would move slowly, from

overhead at the south pole, to overhead at the equator. The length of daylight

everywhere in the southern latitudes, between the equator and the south pole,

would gradually decrease, from 24 hours to 12 hours. The length of daylight

everywhere in the northern latitudes, between the equator and the north pole,

would gradually increase, from zero to 12 hours. Every southern latitude woud

have the sun directly overhead once during these 3 months. By October 1, every

place on Earth would have 12 hours of daylight and 12 hours of dark.

-- From October 1 to the end of December, the sun would move slowly, from

overhead at the equator, to overhead at the north pole. The length of daylight

everywhere in the southern latitudes, between the equator and the north pole,

would gradually decrease, from 12 hours to zero. The length of daylight

everywhere in the northern latitudes, between the equator and the north pole,

would gradually increase, from 12 hours to 24 hours. Every northern latitude

woud have the sun directly overhead once during these 3 months. By January 1,

the southern latitudes would have zero daylight, and the northern latitudes

would have 24 hours of it.

Then the whole thing would repeat during the next year.

Every latitude on Earth would have the sun directly overhead twice a year, except

the poles, where it would be only once a year.

Human life on Earth, of course, would not be possible.