Mediaspace scheduled maintenance: Aug 25, 2026 07:00 - 12:00 AM. During this time, videos will be temporarily unavailable. Check status updates.

Lecture

Solar Astronomy: Equinoxes and Solstices

In course

PHYS-118: Building physics

Ce cours traite des principaux phénomènes physiques observables dans le bâtiment et doit permettre à l'étudiant d'acquérir des connaissances de base dans le domaine de la physique du bâtiment. ...

Description

This lecture covers solar astronomy concepts related to equinoxes and solstices, explaining the Earth-Sun axis, declination, and geocentric coordinates. It also discusses the equal times and areas phenomenon, as well as the solar race and stereographic projection.

This video is available exclusively on Mediaspace for a restricted audience. Please log in to MediaSpace to access it if you have the necessary permissions.

Watch on Mediaspace

Instructors (2)

Jean-Louis Scartezzini

Director of EPFL Solar Energy and Building Physics Laboratory (1994-present); Founder & Director of ENAC Institute of Infrastructures, Resources and Environment (2002-2009); Founder & Director of EPFL Doctoral Program in Environment (2002-2009); Co-Director of EPFL Institute of Building Technology (1994-1997); Associate Professor of Building Physics at EPFL (1994-1997); Associate Professor of Building Physics at University of Geneva (1990-1997); Group Leader & Research Fellow at the EPFL Solar Energy Research Group (1981-1989); Research Fellow at the Applied Geophysics Institute of University of Lausanne (1980-1981).

Andreas Schueler

Studies of Physics at the University of Freiburg, Germany
Master of Science (Physics) from the University of Michigan, Ann Arbor, USA
PhD degree from the University of Basel, Switzerland

Official source

Related concepts (32)

Equinox

A solar equinox is a moment in time when the Sun crosses the Earth's equator, which is to say, appears directly above the equator, rather than north or south of the equator. On the day of the equinox, the Sun appears to rise "due east" and set "due west". This occurs twice each year, around 20 March and 23 September. More precisely, an equinox is traditionally defined as the time when the plane of Earth's equator passes through the geometric center of the Sun's disk.

March equinox

The March equinox or northward equinox is the equinox on the Earth when the subsolar point appears to leave the Southern Hemisphere and cross the celestial equator, heading northward as seen from Earth. The March equinox is known as the vernal equinox (spring equinox) in the Northern Hemisphere and as the autumnal equinox in the Southern Hemisphere. On the Gregorian calendar, the northward equinox can occur as early as 19 March or as late as 21 March at 0° longitude.

September equinox

The September equinox (or southward equinox) is the moment when the Sun appears to cross the celestial equator, heading southward. Because of differences between the calendar year and the tropical year, the September equinox may occur anytime from September 21 to 24. At the equinox, the Sun as viewed from the equator rises due east and sets due west. Before the Southward equinox, the Sun rises and sets more northerly, and afterwards, it rises and sets more southerly.

Equatorial coordinate system

The equatorial coordinate system is a celestial coordinate system widely used to specify the positions of celestial objects. It may be implemented in spherical or rectangular coordinates, both defined by an origin at the centre of Earth, a fundamental plane consisting of the projection of Earth's equator onto the celestial sphere (forming the celestial equator), a primary direction towards the vernal equinox, and a right-handed convention.

Solstice

A solstice is an event that occurs when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 21 and December 21. In many countries, the seasons of the year are determined by the solstices and the equinoxes. The term solstice can also be used in a broader sense, as the day when this occurs. The day of a solstice in either hemisphere has either the most sunlight of the year (summer solstice) or the least sunlight of the year (winter solstice) for any place other than the Equator.

Related lectures (34)

Radio Universe: Sky Surveys MOOC: The Radio Sky I: Science and Observations

Explores sky surveys in the radio universe, covering observations, coordinate systems, all-sky surveys, and mapping galaxies.

Coordinate Systems: Frames of Reference MOOC: Space Mission Design and Operations

Explains various coordinate systems used in space missions and the precession of equinoxes.

Untitled

The Sun: Fusion Reactor MOOC: Plasma Physics: Applications

Delves into the Sun as a fusion reactor, discussing properties, fusion process, and photon diffusion.

Motion of the Sun in the Milky Way MOOC: Introduction to Astrophysics