# Tag Info

29

The clouds can be seen moving but of course it's subtle at first glance. Frame 16: Frame 20:

28

That would have many consequences. For example the Coriolis force would change the sign. Thus wind around pressure systems would switch the direction from north and south hemisphere, but also the Ekman spiral in the ocean would be affected. Surface heating at sloped terrain will different, as the sun would rise in the West. This would change thermal induced ...

27

They are moving, but not fast enough to notice at the distance shown. From the NASA page: These images were taken between 3:50 p.m. and 8:45 p.m. EDT on July 16, showing the moon moving over the Pacific Ocean near North America. The North Pole is in the upper left corner of the image, reflecting the orbital tilt of Earth from the vantage point of the ...

23

The speed of rotation of Earth is controlled by its angular momentum. And the conservation of angular momentum is a very serious law of physics (perhaps even stricter than conservation of mass). So in the same way that for the Earth to lose mass, that mass have to go somewhere. For the Earth to lose angular momentum, it'd have to go somewhere. Earth's ...

22

Depending on the assumptions you make, the Moon would suddenly have a retrograde orbit. If the moon had a retrograde orbit, it would have tremendous consequences. Retrograde orbits tend to become less distant over time, meaning the moon would either be much closer to the Earth with huge tidal effects or come more close in the future. At some point, the Moon ...

19

TL;DR The Earth's rotational angular momentum is indeed being transferred to the Moon's orbit. However, this is a very slow process that is barely noticeable even over the course of hundreds of years. That long-term trend is invisible in the short thirty year span shown in the graph in the question. The variations seen in the plot result from transfer of ...

18

Yes, it's true (in the northern hemisphere). The small eccentricity of the Earth's orbit is not anywhere close to a key driver in the seasons. The key driver of the seasons is the Earth's obliquity. In the northern hemisphere, the axial tilt of Earth's rotation axis has the northern half of the Earth facing a bit toward the Sun in June/July/August and away ...

18

The short answer is "Probably Yes". The longer answer is that it is debatable whether Earth's rotation will become tidally locked to the moon due to tidal drag, at which point it will not be rotating relative to the moon, or whether the sun's exhaustion of hydrogen and the fusion of Helium will result in the sun's expansion vaporizing the earth first. As ...

14

Let's assume that the earth didn't suddenly stop spinning (because intertia and conservation of angular momentum would do all sorts of "interesting" things that are deserving of a What-If answer), and stipulate that the earth slowed down gradually, or possibly that it was never spinning in the first place (although I'm sure this would have all sorts of other ...

12

Yes, it's called polar motion. The rotational pole moves continuously, as you can see from the right-hand side of this figure (below) by the Earth Orientation Centre (EOC) and the International Earth Rotation and Reference Systems Service (IERS). The figure shows about 650 days of time; mjd is modified Julian day and time goes along the locus in the polar ...

10

Your confusion arise from the definition of East and West hemispheres. That's an arbitrary and confusing definition. Because East and West are relative directions. Meaning they depend on the position were they are specified. East and West come from the proto-germanic languages, where East means dawn and West means evening. Therefore, East from any given ...

10

The image is real, and the clouds are moving, they just move slow, as clouds do. The unnatural appearance arise because they are taken by DSCOVR at an extraordinarily large distance, from a place called L1, more than one million kilometers away!!!. The rotation of the Earth in the animation makes it difficult to distinguish the movement of the clouds, but ...

10

The Earth moves faster around the Sun when it is near its perihelion (the closest point of its orbit to the Sun). And it moves slower when it is further away (aphelion), just as Kepler realized quite a while ago when enunciating his Third Law of Planetary Motion. There are many ways to write a formula to calculate Earth's speed around the Sun. But for your ...

9

This is covered in an episode of the National Geographic TV series Aftermath called "When The Earth Stops Spinning". It's also covered by "If the Earth Stood Still: Modeling the absence of centrifugal force" by Witold Fraczek of Ersi, a GIS software company. The Earth is not round, but bulges at the equator. The diameter at the equator is 43km more than ...

9

Earthquakes, specially those at subduction zones, result in redistribution of mass (as one plate slides on top of the other). This change in distribution of mass causes changes in gravitational field that can be measured by satellites such as GRACE. Now angular momentum is conserved. If we know the change in mass then we can calculate the change in moment ...

9

Roughly once per day, but a tiny bit faster. As the website for Columbia University's Lamont-Doherty Earth Observatory says: The inner core rotates in the same direction as the Earth and slightly faster, completing its once-a-day rotation about two-thirds of a second faster than the entire Earth. Over the past 100 years that extra speed has gained the ...

9

The moon's orbit is at a slight angle from the plane of earth's orbit around the sun, so it doesn't always hit the right spot, as described on NASA's Total Solar Eclipse 2017 site: Eclipses only occur if the Moon is located within 0.5 degrees of the plane of the ecliptic, on a line that passes through the center of the Sun and the Earth. The Moon ...

8

There is no evidence that Earth had a much greater axial tilt so long ago. To my knowledge, the evidence for changes in the axial tilt of the Earth is based on ocean sediment cores (see http://en.wikipedia.org/wiki/James_Hays ) and ice cores ( see http://en.wikipedia.org/wiki/Milankovitch_cycles#Axial_tilt_.28obliquity.29 ). However, these only go back ...

8

The biggest flaw I see in a cursory look at this work is failure to compensate for atmospheric refraction. Density varies in the atmosphere enough that the refractive index varies. At low angles above the horizon the temperature structure of the atmosphere becomes very important in determining optical refraction and at low angles very close to the ground ...

8

In theory, if the Earth was a solid object, the Chandler wobble would be easy to understand. It's simply a result of the polhode rolling without slipping on the herpolhode lying in the invariable plane. In other words, $\mathrm I \dot \omega + \omega \times (\mathrm I \omega) = 0$, where $\mathrm I$ is the Earth's inertia tensor and $\omega$ is the Earth's ...

7

Imagine you can fly ignoring wind, gravitation and other forces. You are exactly on the rotation axis looking down the Earth on its North side. You'll see the Earth turning counter-clockwise. But If you look at the same but in South Hemisphere, the Earth is turning clockwise. This is just a convention and it depends on your point of view. Nevertheless, If ...

6

David's answer is correct, but I wanted to elaborate a bit further. The Earth's axis is tilted about $23.5^\circ$ from being perpendicular to the plane of its orbit (as David mentioned, 'obliquity' or 'axial tilt' is the name for this.) As a result of this tilt, at the solstices (the first day of winter or summer,) the sun is directly facing latitudes of ...

6

Changes in the Earth's rate of rotation is measured by the International Earth Rotation and Reference Systems Service (IERS) using observational techniques. They publish daily the rate and orientation of the Earth's rotation, and publish near-term forecasts (of great practical use if you are launching satellites into orbit.) Mass movements in the atmosphere ...

6

The Earth rotates from west to east or counter-clockwise. You can do simple experiment. put your face towards the polar star and stretch your hands. Your head shows North (towards polar star) and your left hand points towards west, your right hand points towards east and your back head points towards South. The sun rises in the East - from the direction of ...

6

You need to calculate the change in the moment of inertia of the Earth and use conservation of angular momentum. In the case of eg. a large dam, (most of) the water will ultimately come from the sea, effectively removing a thin layer of water. The contribution of the removed water to the moment of inertia depends on the distance from the rotation axis and ...

5

A simple way to estimate the implications is to simplify the problem. If the orbits of Earth, Sun and Moon were circular and in the same plane, and the Earth had no tilt, the only remaining tidal constituents would be $M_2$ and $S_2$ (also the overtides and combination tides: $M_4$, $MS_4$...). The rest of the tidal constituents can be expressed as linear ...

5

As has been noted in a comment, it depends on how you define seasons (see https://earthscience.stackexchange.com/a/2603/111). If seasons are defined in astronomical terms, then they have the same length everywhere on the planet. This is simply down to geometry. However, the effects of astronomical seasons vary geographically in a number of ways. The ...

5

Meteorology relies heavily on a spherical model of the earth. If you consider one of the major "forces," the Coriolis force, it is derivable only from a spherical earth. Now, there are planar representations, where the earth's curvature has a negligible effect, such as mesoscale meteorology or micrometeorology. A sphere also has modeling advantages ...

4

@kwinkunks already gave a good answer on the short time scale. On long time scales, mantle convection and plate tectonics redistributes large amounts of mass, and the conservation of angular momentum requires that the direction and speed or rotation of the Earth changes accordingly. (This is independent of the fact that the orientation of Earth's axis may ...

4

Two very different processes! First, if the Earth suddenly stopped rotating then the angular momentum would result in everyone and everything on the Earth's surface being flung sideways at a rate proportional to the distance from the Earth's spin axis. That is, no change at the poles, to 1670 km/hour at the equator. There would also be oceanic tsunami's ...

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