is summer longer in n. hemisphere or s. hemisphere? and why?

Answer 1

The length of summer (as measured from the point the sun is at it zenith at the Tropic of Cancer or Capricorn to the point it is at its zenith at the Equator) should be the same, unless we have a lopsided Earth.

Answer 2

Technically it would be slightly longer in the northern hemisphere. We are at aphelion in the middle of summer in the northern hemisphere. That means we are furthest from the sun. This also means Earth's orbital motion is slowest. So, the summer in the northern hemisphere would be longer by maybe a day or two. It's really a technicality and doesn't make much difference one way or the other.

Think of it this way. The vernal equinox this year was on March 21st. The Autumnal equinox we just had was on Sept 23. There are 186 days between those two dates, leaving only 179 days left for a year. The period between the beginning of northern spring and the end of northern summer is longer than the period between the beginning of southern spring and the end of southern summer.

Answer 3

Neither.
The axial tilt of the Earth is what gives us our seasons.
When Earth orbits the Sun, it only goes to follow that the northern hemisphere will have a greater exposure to the Sun 50% of the time, and the southern hemisphere will receive the other 50%.
OK?

Answer 4

Difficult to know what you mean. Summer is an arbitrary (I've been using that word a lot) division of the 12 months of the year, which are themselves a random division of the year. If you're going on the calendar definition of the seasons, they're the same length.

If you mean the times of warmth and cold, well then, it depends on where you are, and what your definitions are of Summer and Winter weather.