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Thus, the Sun occupies 0.00001% (1 part in 10 7) of the volume of a sphere with a radius the size of Earth's orbit, whereas Earth's volume is roughly 1 millionth (10 −6) that of the Sun. Jupiter, the largest planet, is 5.2 AU from the Sun and has a radius of 71,000 km (0.00047 AU; 44,000 mi), whereas the most distant planet, Neptune, is 30 AU ...
The most commonly seen in the scientific literature denotes the time of year as the number of degrees on its orbit from the northward equinox, and increasingly there is use of numbering the Martian years beginning at the equinox that occurred April 11, 1955. [1] [2] Mars has an axial tilt and a rotation period similar to those of Earth.
Mars comes closer to Earth more than any other planet save Venus at its nearest—56 million km is the closest distance between Mars and Earth, whereas the closest Venus comes to Earth is 40 million km. Mars comes closest to Earth every other year, around the time of its opposition, when Earth is sweeping between the Sun and Mars. Extra-close ...
Since this value is close to zero, the center of the orbit is relatively close to the center of the Sun (relative to the size of the orbit). As seen from Earth, the planet's orbital prograde motion makes the Sun appear to move with respect to other stars at a rate of about 1° eastward per solar day (or a Sun or Moon diameter every 12 hours).
Sagan goes on to extend the comparison in terms of surface area, explaining that if the Cosmic Calendar were scaled to the size of a football field, then "all of human history would occupy an area the size of [his] hand". [3] A similar analogy used to visualize the geologic time scale and the history of life on Earth is the Geologic Calendar.
Solar cycles are nearly periodic 11-year changes in the Sun's activity that are based on the number of sunspots present on the Sun's surface. The first solar cycle conventionally is said to have started in 1755. The source data are the revised International Sunspot Numbers (ISN v2.0), as available at SILSO. [1]
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The average duration of the day-night cycle on Mars — i.e., a Martian day — is 24 hours, 39 minutes and 35.244 seconds, [3] equivalent to 1.02749125 Earth days. [4] The sidereal rotational period of Mars—its rotation compared to the fixed stars—is 24 hours, 37 minutes and 22.66 seconds. [4]