i think it could be tilt
The telescope.
The development of the telescope in the 17th century allowed astronomers to observe planets beyond those visible to the naked eye. This led to the discovery of Uranus in 1781, Neptune in 1846, and Pluto in 1930, expanding the known planets beyond the original five visible to ancient civilizations.
Kepler showed that the orbits of the planets are elliptical, with the Sun at one of the focal points. This discovery led to his laws of planetary motion, which describe how planets move in their orbits.
he wondered if there was a reason that the planets closest to the sun move faster than the planets farther away.
Neptune was discovered when astronomers noticed that the orbit of Uranus was being perturbed by gravitational forces from an unknown distant planet. This led to the search for and eventual discovery of Neptune in 1846.
The telescope.
The telescope and its various improvements
The development of the telescope in the 17th century allowed astronomers to observe planets beyond those visible to the naked eye. This led to the discovery of Uranus in 1781, Neptune in 1846, and Pluto in 1930, expanding the known planets beyond the original five visible to ancient civilizations.
Kepler showed that the orbits of the planets are elliptical, with the Sun at one of the focal points. This discovery led to his laws of planetary motion, which describe how planets move in their orbits.
The wording of this question needs to be improved to understand what you mean.
He said that sun was the center of the universe and that the earth and all the other planets orbit around it.
he wondered if there was a reason that the planets closest to the sun move faster than the planets farther away.
discovery of the atom's structure
The UV rays were entering the surface of earth. This led to discovery of ozone hole.
The discovery of radioactivity
Watson and crick and the discovery of the double helix
There are eight planets in the solar system. For a brief period, the newly-discovered object, Eris was considered for planetary status, but the discovery led to a debate that ended with Pluto losing its status as a planet.