Why does the International Dateline only touch at the north and south poles?
I'm mystified by the question. Every single point on the International Dateline is
a point where it touches the Earth, and there are an infinite number of those.
What else do you want it to touch ?
Since the Earth is roughly spherical (ball-shaped), you can head out either eastward or westward from the International Dateline and wind up anywhere you want to be. If Dubai is your final destination and you are presently anywhere on the International Dateline ... with two exceptions ... then the shortest route to Dubai is westward from your present location. The exceptions are the very end-points of the International Dateline at the north and south poles…
What is the imaginary strip running down the middle of the Atlantic Ocean from the North Pole to South Pole?
It is the meridian 180 degrees from Greenwich in England which is the zero meridian. It is an imaginary line from the North to the South poles through the Pacific. It is used by shipping as the international dateline but because it runs through land masses, each local government decides which side they will be located for time-keeping purposes. The chosen line is then considered the international dateline for social purposes - days, dates, etc.
The Prime Meridian is the line that marks all points at Zero longitude. The International Dateline roughly follows the meridian of 180Â° longitude. Since those two lines mark different longitudes, the only place where they can meet would be a place where all longitudes come together. Fortunately, there are two of those on Earth . . . the north and south poles. They meet at 90Â° north latitude and at 90Â° south latitude.
A hemisphere is a section of the Earth located north/south or between two major lines of latitude or longitude. The Northern Hemisphere is located north of the Equator. The Southern Hemisphere is located south of the Equator. The Western Hemisphere is located west of the Prime Meridian and east of the International Dateline. The Eastern Hemisphere is located east of the Prime Meridian and west of the International Dateline.
"An" international dateline? There's only one international dateline. it is roughly equal to the 180 degree line of longitude, which runs through the Pacific Ocean from the north pole to the south pole passing between Russia and Alaska. If you are going from the east to the west and you cross it at, say 10:00 am on Monday you change the date to Tuesday. if you are going the other way, Monday would become Sunday.
If you're talking about magnets, then yes, north poles attract south poles. Two North poles repel, and two South poles repel. If you're talking about the Earth's north and south poles, those are just locations. They're about as far apart as it's possible to get on Earth, and they have no influence on each other.