Final answer:
The beginning of summer in the Northern Hemisphere occurs when this hemisphere is tilted toward the Sun, typically in June, due to the Earth's axis tilt, not its distance from the Sun. The tilt causes more direct sunlight and longer days in the Northern Hemisphere, especially at higher latitudes such as the Tropic of Cancer.
Step-by-step explanation:
When the Earth is in a position where the Northern Hemisphere is tilted toward the Sun, this hemisphere experiences the beginning of summer. In June, due to the tilt of Earth's axis by 23.5°, the Northern Hemisphere leans into the Sun and receives more direct sunlight, leading to higher temperatures and longer days. This phenomenon is due to the tilt of the Earth's axis, not the distance of the Earth from the Sun, as the Earth is actually closest to the Sun in January when the Northern Hemisphere experiences winter.
During this position in Earth's orbit, places like the Tropic of Cancer, at 23° N latitude, will experience the Sun at the zenith at noon on the summer solstice. In contrast, during December, when the Southern Hemisphere leans into the Sun, the Northern Hemisphere experiences winter due to the axial tilt directing the Sun’s rays more directly at the Southern Hemisphere.
Understanding the changing seasons involves recognizing the significance of the Earth’s tilt and its effect on solar illumination across the hemispheres, rather than the proximity of the Earth to the Sun which only changes marginally throughout the orbit.