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Johannes Kepler was born on December 27, 1571, in the Free Imperial City of Weil der Stadt (now part of Germany), and he died on November 15, 1630, in Regensburg. He was an influential astronomer, mathematician, and astrologer of the 17th century, during the scientific revolution.

Kepler was married twice, first to Barbara Müller, and then, after her death, to Susanna Reuttinger. He had a total of 12 children, though not all survived into adulthood. Kepler studied at the University of Tübingen and held a variety of positions including mathematician to the Habsburg court and astronomy teacher in Graz and Linz. He spent the last years of his life in Regensburg, where he died.

Kepler was motivated by a fervent desire to understand the mysteries of the natural world, and he believed that the key to understanding the universe could be found in mathematical and geometric principles. His Lutheran faith also played a significant role in shaping his worldview and scientific pursuits.

Kepler is renowned for his laws of planetary motion, which transformed the understanding of the solar system. His laws laid the foundation for Isaac Newton's theory of universal gravitation and still form a crucial part of astronomy and physics.

Kepler faced numerous challenges in his research, most notably the imperfections of observational instruments of his time, political and religious turmoil, and personal tragedies. However, his meticulous analysis of the astronomical data left by his mentor Tycho Brahe allowed him to make his groundbreaking discoveries.

Kepler's primary achievements lie in his formulation of the three laws of planetary motion, which played a significant role in the scientific revolution and the subsequent development of modern physics and astronomy. Kepler also made significant contributions to optics, including research into the workings of the human eye and the design of improved telescopes.

Kepler's laws of planetary motion are usually stated as follows:

First Law (The Law of Ellipses):

The orbit of every planet is an ellipse with the Sun at one of the two foci.

Second Law (The Law of Equal Areas):

A line joining a planet and the Sun sweeps out equal areas during equal intervals of time.

Third Law (The Law of Harmonies):

The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

This can be expressed mathematically as:

T^{2} ∝ a^{3}

Where:

- T: the orbital period of the planet
- a: the semi-major axis of the planet's orbit

The following tutorials and calculators are influenced by the work the great physicist Johannes Kepler, each calculator contains a tutorial that explains Johannes Kepler in the field

- Physics Gravitation Tutorial 8.2 - Gravitational Potential Energy and Kepler Laws
- Physics Cosmology Tutorial 22.3 - The Moon's Movement, Eclipses and Calendars
- Physics Cosmology Lesson 22.2.5 - Planetary Motion around the Sun
- Physics Cosmology Lesson 22.6.4 - Hierarchic Structures in the Universe
- Cosmic Velocities Calculator
- Gravitational Field Strength Calculator
- Gravitational Force Calculator
- Gravitational Potential Energy Calculator
- Kepler Third Law Calculator
- Orbit Pericenter Distance Calculator
- Orbital Velocity Calculator
- Rotational Velocity of a Star Calculator