The Earth rotates on its axis and orbits the Sun to complete one revolution, equivalent to one year of axial rotations. The Sun also travels through the Milky Way in motion relative to other galaxies in the universe.
Scientists have been trying to describe how Earth moves by correctly measuring the objects around and the light leftover from the Big Bang. However, there remains a lot of uncertainty that scientists may never be able to discover.
A man looks at a projected image of the Earth in the universe at the Carl-Zeiss Planetarium in Stuttgart, southern Germany, on April 14, 2016. The planetarium will reopen for the public on April 23, 2016, after a complete refurbishment.
Determining Earth's Motion in Space
Earth's motion through space is not just defined by the planet's rotation on its axis and its motion around the Sun. According to Big Think, it also involves the motion of the Solar System through the galaxy, the galaxy's motion through the Local Group, and its movement through intergalactic space.
Only through a combination of these measurements and the leftover glow from the Big Bang can scientists be able to arrive at a meaningful answer as to Earth's motion in space.
Scientists said that Earth moves around the Sun on its axis and makes it appear to make a closed, unchanging, and optical orbit. But looking closely at it, the planet is moving away from the Sun by around 1.5 cm per year. Observations reveal that Earth precesses on its orbit around the Sun on timescales of about tens of thousands of years.
Furthermore, the Earth revolves around the Sun at speeds ranging from 29.29 km/s to 30.29 km/s. The perihelion during early January causes the fastest motions of Earth, while the aphelion in July causes the slowest motion. On top of that, the Solar System travels in the Milky Way at speeds of 200 to 220 km/s and is inclined approximately 60° to the plane of the planets.
But the motion is not vortical but is the sum of all the velocities. That means the Milky Way and Andromeda galaxies travel toward each other at 100km/s. Meanwhile, clumps and repulsive underdense regions in intergalactic space tug on the Local Group, which moves at combined speeds of 627 ± 22 km/s relative to the cosmic average.
On the other hand, Big Bang's leftover light or photons gives a cosmically unique rest frame that suggests the Sun moves at approximately 368 km/s relative to the Cosmic Microwave (CMB) background. But being in the Milky Way galaxy, humans can only make such measurements.
Earth Moves Faster Than Previously Thought
Humans on Earth can't feel that the planet is moving through space. But evidence suggests that it is indeed moving at a retrograde motion, which happens when Earth catches up with another planet in its orbit, Space.com reported.
It takes 365 days to complete one revolution around the Sun, and Earth's position could tell the season. For instance, it causes the summer season when it is closest to the Sun, and it also causes winter when at its farthest location. But people on Earth see the Sun from different vantage points, which can be calculated using the apparent change of position of the star in respect to other stars, which is called a parallax.
The planet's speed can also depend on its latitude, wherein NASA estimated that it could be 1,670 km/h given that the Earth's circumference is roughly 40,070 kilometers. It takes 24 hours to complete one rotation or one day.
More so, scientists explain that there is no chance that objects on Earth will fling off to space because gravity is so strong compared to the centripetal acceleration, which counteracts the gravity by 0.3%. That means objects weigh slightly less at the equator than at the poles.
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