Earth at Perihelion 2025 is on Saturday, January 4, 2025: What changes do we see on Earth between perihelion and aphelion?

Saturday, January 4, 2025 is Earth at Perihelion 2025. January Earth Perihelion Earth Perihelion

During the present time, not any measurable difference. During perihelion the Earth currently receives only 6% more solar radiation from the Sun.

Perihelion currently occurs around January.

One can research Milankovitch cycles to determine that when the orbit of Earth becomes more elliptical, effects can be drastic. In an eccentric orbital path, when the North Pole of Earth points away from the Sun during aphelion, ice ages can be triggered.

The effects are caused because most of the land mass on planet Earth lies in the Northern Hemisphere.

During which months does Earth's perihelion occur? When does Earth's aphelion occur?

Earth reaches perihelion in early January each year, and passes through its aphelion point near the start of July.

aphelion is when the earth is farthest

perihelion is closest

(this event does not effect the seasons)

What causes the earth to rotate?

earth's rotation is the rotation of the solid Earth around its own axis. The Earth rotates towards the east. As viewed from the North Star Polaris, the Earth turns counter-clockwise.Earth's rotation period relative to the Sun (true noon to true noon) is its true solar day or apparent solar day. It is the derivative of the equation of time and thus depends on the eccentricity of Earth's orbit and the tilt (obliquity) of Earth's axis. Both vary over thousands of years[1] so the annual variation of the true solar day also varies. Generally, it is longer than the mean solar day twice a year and shorter twice a year.[n 1] The true solar day tends to be longer near perihelion when the Sun apparently moves along the ecliptic through a greater angle than usual, taking about 10 seconds longer to do so. Conversely, it is about 10 seconds shorter near aphelion. It is about 20 seconds longer near a solstice when the projection of the Sun's apparent movement along the ecliptic onto the celestial equator causes the Sun to move through a greater angle than usual. Conversely, near an equinox the projection onto the equator is shorter by about 20 seconds. Currently, the perihelion and solstice effects combine to lengthen the true solar day near December 22 by 30 mean solar seconds, but the solstice effect is partially cancelled by the aphelion effect near June 19 when it is only 13 seconds longer. The effects of the equinoxes shorten it near March 26 and September 16 by 18 seconds and 21 seconds, respectively.[2][3][4]

The average of the true solar day over an entire year is the mean solar day, which contains 86,400 mean solar seconds. Currently, each of these seconds is slightly longer than an SI second because Earth's mean solar day is now slightly longer than it was during the 19th century due to tidal acceleration. The mean solar second between 1750 and 1892 was chosen in 1895 by Simon Newcomb as the independent unit of time in his Tables of the Sun. These tables were used to calculate the world's ephemerides between 1900 and 1983, so this second became known as the ephemeris second. The SI second was made equal to the ephemeris second in 1967.[5]

Earth's rotation period relative to the fixed stars, called its stellar day by the International Earth Rotation and Reference Systems Service (IERS), is 86,164.098 903 691 seconds of mean solar time (UT1) (23h 56m 4.098 903 691s, 0.997 269 663 237 16 SI days).[6][n 2] Earth's rotation period relative to the precessing or moving mean vernal equinox, misnamed its sidereal day,[n 3] is 86,164.090 530 832 88 seconds of mean solar time (UT1) (23h 56m 4.090 530 832 88s, 0.997 269 566 329 08 SI days).[6] Thus the sidereal day is shorter than the stellar day by about 8.4 ms.[8]

Both the stellar day and the sidereal day are shorter than the mean solar day by about 3 minutes 56 seconds. The mean solar day in SI seconds is available from the IERS for the periods 1623–2005[9] and 1962–2005.[10]

Deviation of day length from SI based day, 1962–2009

Recently (1999–2009) the average annual length of the mean solar day in excess of 86,400 SI seconds has varied between 0.3 ms and 1 ms, which must be added to both the stellar and sidereal days given in mean solar time above to obtain their lengths in SI seconds.

The angular speed of Earth's rotation in inertial space is 7.2921159 × 10−5 radians per SI second (mean solar second).[6] Multiplying by (180°/π radians)×(86,400 seconds/mean solar day) yields 360.9856°/mean solar day, indicating that Earth rotates more than 360° relative to the fixed stars in one solar day. Earth's movement along its nearly circular orbit while it is rotating once around its axis requires that Earth rotate slightly more than once relative to the fixed stars before the mean Sun can pass overhead again, even though it rotates only once (360°) relative to the mean Sun.[n 4] Multiplying the value in rad/s by Earth's equatorial radius of 6,378,137 m (WGS84 ellipsoid) (factors of 2π radians needed by both cancel) yields an equatorial speed of 465.1 m/s, 1,674.4 km/h or 1,040.4 mi/h.[11] Some sources state that Earth's equatorial speed is slightly less, or 1,669.8 km/h.[12] This is obtained by dividing Earth's equatorial circumference by 24 hours. However, the use of only one circumference unwittingly implies only one rotation in inertial space, so the corresponding time unit must be a sidereal hour. This is confirmed by multiplying by the number of sidereal days in one mean solar day, 1.002 737 909 350 795, which yields the equatorial speed in mean solar hours given above of 1,674.4 km/h.

The permanent monitoring of the Earth's rotation requires the use of Very Long Baseline Interferometry coordinated with the Global Positioning System, Satellite laser ranging, and other satellite techniques. This provides the absolute reference for the determination of universal time, precession, and nutation.

Over millions of years, the rotation is significantly slowed by gravity