The equinox of the coordinate system must be given.
Solar system ephemerides are essential for the navigation of spacecraft and for all kinds of space observations of the planets, their natural satellites, stars, and galaxies.
Scientific ephemerides for sky observers mostly contain the positions of celestial bodies in right ascension and declination, because these coordinates are the most frequently used on star maps and telescopes.
Typically, such ephemerides cover several centuries, past and future; the future ones can be covered because the field of celestial mechanics has developed several accurate theories.
Nevertheless, there are secular phenomena which cannot adequately be considered by ephemerides.
Ephemerides of the planet Saturn also sometimes contain the apparent inclination of its ring.
Celestial navigation serves as a backup to the Global Positioning System.
The unit began with an introductory lesson on radioactive isotopes, followed by two days of hands-on small group activities that developed critical thinking, math and graph making/interpretation skills.
First, students visualized the concepts of radioactive decay and half-life in an activity using M&Ms™ and marshmallows.
These questions, coupled with the complex effects of metamorphism and element mobility, stand in the way of understanding Earth evolution.
The first two authors developed a unit to correct 8th grade students’ misconceptions and to foster interest in radioactive decay and radiometric dating.
Historically, positions were given as printed tables of values, given at regular intervals of date and time.