The planets surrounding the Earth differ significantly from each other in size and shape. The diameter of some planets of the solar system is quite small and in some cases does not exceed the diameter of the satellites of other planets. And it's very interesting! For example, the smallest diameter planet is Mercury, smaller than Jupiter's moon Ganymede, and Saturn's moon Titan. In addition, some planets are wider at the equator compared to their poles, which is a consequence of differences in the composition of the substances that make up these planets, and differences in the angular velocities of their rotation around their own axis. As a result, some planets are almost perfect spheres, and some are ellipsoids. Accordingly, the diameter of the latter is a non-constant value.
Location
In the solar system, the planets in order from the Sun go in a certain sequence. Let's consider it. Actually, the Sun, closest to it is Mercury, behind it is Venus, then our Earth, and after it Mars. Mars is followed by two giant planets -Jupiter and Saturn, and Uranus and Neptune close this row. The last planet, Pluto, has recently lost its honorary status of a planet after heated astronomical discussions. Until now, it remains unchanged. The diameter of the planets in the solar system varies widely.
Relatively small solids
With a diameter of only 4879 km, the first planet Mercury is not much larger than our Moon, whose diameter is 3474 km. At the same time, due to the very long period of revolution around its axis (58, 646 days), Mercury is an almost perfect ball. The next planet is Venus, which is often called the sister of the Earth, since their diameter is almost the same and is 12104 km for Venus and 12756 km for the Earth. Venus has a regular spherical shape, due to the low speed of rotation: one revolution in 243.05 days, that is, a Venusian day is equal to 8 months of Earth time. The difference between the planet Earth and the planet Venus lies in the elliptical shape of the Earth, resulting from a relatively high rate of rotation. This makes the Earth related to Mars, the days on which are almost equal to each other. By the way, the difference in the diameters of these planets of the solar system, measured along the equator and along the meridian, is the same value - 40 km, although Mars is almost half the size of the Earth, its diameter along the equator is only 6792.4 km.
Gas giant planets
Let's continue our study. The diameter of the planets of the solar system Jupiter and Saturn is able to amaze the imagination. Because both bodiesjust huge! Jupiter has a diameter of 142,984 km and, having a period of revolution around its axis of only 9 hours 55 minutes, in combination with a predominantly gaseous composition, it is a classic ellipsoid in shape, with a difference in distances measured along the equator and from pole to pole in 9726 km. The second planet Saturn is also predominantly gas and also has a high angular velocity, resulting in a difference in distance measured along the equator and meridian of almost 12,000 km. The diameter of this planet is 108728 km. The asteroid belt forms around Saturn its famous rings, which art workers are so fond of depicting. The next planet, Uranus, is no longer so large, its diameter is 50,724 km. The period of rotation around the almost earth's axis is 17 hours, but the composition is also gaseous, so the difference in the equatorial and meridional diameters is a decent value of 1172 km. The last, that is, the most distant planet from the Sun, is Neptune. With a diameter of 49244 km, it is almost equal to Uranus, it also has an ellipsoid shape with a distance difference of 846 km and a rotation speed almost identical to Uranus.
Results
For the convenience of practical use, the diameter of the planets of the solar system in kilometers is given in the following table. Consider the features:
| Planet | Diameter in kilometers | Diameter in relation to Earth |
| Mercury | 4879 | 0, 38 |
| Venus | 12104 | 0, 95 |
| Earth | 12756 | 1 |
| Mars | 67920 | 0, 53 |
| Jupiter | 142984 | 11, 21 |
| Saturn | 108728 | 8, 52 |
| Uranus | 50724 | 3, 98 |
| Neptune | 49244 | 3, 86 |
The arrangement of bodies in the above table corresponds to the order from the Sun. Quite conditionally, if we take only the diameter of the planets of the solar system, they can be divided into four groups. The first group - relatively small bodies: Mars and Mercury, the second group - conditional "sisters": Venus and Earth, another group - gas giants: Jupiter and Saturn. The last group is the planets, also consisting mainly of gaseous compounds, but not as large as the giants already mentioned. These are Uranus and Neptune. Of course, the characteristics of the planets are not limited only by their size. Mankind has long been able to determine their masses, accelerations of free fall on their surfaces and much more.
