An age of space travel where our solar system has been duplicated meaning a second earth exists.
A small group of scientists, engineers and astronauts travel to Earth 2 to observe and research the planet and it’s inhabitants.
They didn’t know what to expect but couldn’t believe what they found. A world completely opposite to there own. A planet made of 70% land and 30% water. The majority of the population is left-handed.
Technology and electricity don’t exist. It’s hard to explain but I will give it a go. Earth and Earth 2 are connected somehow. Earth 2 appears to be a mirror image of Earth. If cracks appear on one side, the other side is affected too.
By arriving on Earth 2, the team face the danger of disturbing the balance and welfare of both planets. To prevent any other disturbances, the team decide to return to Earth.
They were on Earth 2 for about 1 month.

However, one of the female scientists falls in love with a man from Earth 2. Their relationship could greatly alter the balance of both realms. So for the greater good, they have no choice but to part ways. The scientists return home with her companions broken-hearted.
But the time they spent together created a miracle. After returning home, the scientist discovered she was pregnant. She gave birth to a son. His DNA and genetics made the first human capable of travelling between the realms without disturbing the balance of both worlds.

I don’t really know how to explain Earth 2. It comes across as a “reflection” of Earth. I ain’t a scientist or a sci-fi experts.
Just a dreamer.
Basically the majority of the population is left-handed. The sun rises from the west and sets in the east (or north to south). The equator runs through the poles. The magnetic fields are opposite.