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33 votes

In the northern hemisphere summer, why are places in the north cooler than those in the south?

The image below (apparently from "physicalgeography.net" is somewhat instructive: Notice that even in the middle of summer, India (at about 30 °N) still gets slightly more sun than the ...
James K's user avatar
  • 797
29 votes

Why clouds are not moving in NASA's video of the Moon passing in front of the Earth?

The clouds can be seen moving but of course it's subtle at first glance. Frame 16: Frame 20:
Adam Caviness's user avatar
26 votes
Accepted

Why clouds are not moving in NASA's video of the Moon passing in front of the Earth?

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 ...
gerrit's user avatar
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26 votes
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Does Earth's core actually turn "backwards" at times?

The mantle rotates about 131850 degrees per year. The actual assertion is that the inner core cycles between rotating about 131851 degrees per year versus 131849 degrees per year over the course of 70 ...
David Hammen's user avatar
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24 votes
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What is the fastest the Earth has ever spun?

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 ...
Camilo Rada's user avatar
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12 votes
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Does the geographic North Pole move?

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 ...
Matt Hall's user avatar
  • 11k
12 votes

In the northern hemisphere summer, why are places in the north cooler than those in the south?

Hours of sunlight are not the only factor that determines insolation (solar energy at the surface). Thought experiment: spread a bed sheet on the floor, switch the lights off, and shine a flashlight ...
GB supports the mod strike's user avatar
11 votes

Why clouds are not moving in NASA's video of the Moon passing in front of the Earth?

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 ...
Camilo Rada's user avatar
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11 votes
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How fast does the Earth's inner-core spin?

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 ...
Spencer's user avatar
  • 3,558
10 votes

Why do we say Earth rotates from west to east?

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 ...
Camilo Rada's user avatar
  • 17.7k
10 votes
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Changes in Earth's orbital and rotation speeds

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 ...
Camilo Rada's user avatar
  • 17.7k
10 votes

Does Earth's core actually turn "backwards" at times?

David Hammen's excellent answer covers the key pieces, but the original question also has this part: The literal claim (as it appears in headlines) seems to make no sense given a basic understanding ...
Wolfgang Bangerth's user avatar
9 votes
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why we don't have solar eclipse every month?

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 ...
jeffronicus's user avatar
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8 votes
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Which are the equations needed to calculate how much moving Earth's water with dams would change Earth's rotation speed?

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, ...
Keith McClary's user avatar
6 votes
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Was the filling of the Three Gorges Dam's impact on the Earth's rotation rate detectable?

One needs to calculate the change in the moment of inertia of the Earth and use conservation of angular momentum (the rotation period is proportional to the moment of inertia). Most of the water will ...
Keith McClary's user avatar
6 votes

Was the filling of the Three Gorges Dam's impact on the Earth's rotation rate detectable?

The .06 microseconds figure doesn't sound accurate The moment of inertia for a solid sphere is $$I = \frac{2mr^2}{5},$$ where $m$ is the mass of the sphere and $r$ is its radius. Applied to the Earth,...
kingledion's user avatar
  • 3,376
6 votes

Why does Meteorology rely on a spherical model of the earth, rather than a flat earth, to function?

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 ...
BarocliniCplusplus's user avatar
5 votes
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How much of one day can be considered nighttime, on average?

To further clarify, assume we are on the equator, I want to know how long a time, as a percentage, you could consider to be nighttime on Earth, with the points in time separating night and day being ...
David Hammen's user avatar
  • 23.6k
5 votes

What would be the impact on tides if the earth had no tilt?

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 ...
arkaia's user avatar
  • 15.4k
5 votes

Will the Earth ever stop rotating?

Strictly speaking, the Earth will never cease to rotate in the technical sense... not while Earth is intact at least. No matter what the Earth might eventually become tidally locked with, whether the ...
seanion's user avatar
  • 51
5 votes
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Are the length of seasons the same globally?

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 ...
Semidiurnal Simon's user avatar
5 votes

Do Earth's layers move at different speeds?

The inner core rotates slightly faster than the rest of the planet. This passage from National Geographic explains: The liquid outer core separates the inner core from the rest of the Earth, and ...
BillDOe's user avatar
  • 2,187
5 votes

Are there any types of winds or waves that are produced just by Earth's rotation?

Yes. Such a thing is called an inertial oscillation. Kelvin waves are not examples of inertial oscillations. Kelvin waves balance the earth's rotation against the normal force of a topographic ...
BarocliniCplusplus's user avatar
4 votes
Accepted

Is it coincidence that Antarctica is centered on the south pole?

It's an interesting thought. Antarctica is not so balanced as it might appear on the maps. East Antarctica is old, consisting probably of cratons and Proterozoic orogenic domains whiles West ...
user2821's user avatar
  • 5,946
4 votes

Does the geographic North Pole move?

@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 ...
Wolfgang Bangerth's user avatar
4 votes

Flight time differences between flying east and flying west

The Jet Stream is the cause for slower flight times to the West. It flows from West to East at high altitudes and therefore helps planes flying East but causes extra resistance for planes flying West.
Julian Cohen's user avatar
4 votes
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Why is it still day in Mumbai at 6:47 PM?

This image from https://www.timeanddate.com/sun/india/mumbai shows that daylight ended at 6:44, so 6:47 was three minutes into civil twilight and pretty much close to daylight. Notice the orange ...
Gimelist's user avatar
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4 votes
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Do Earth's layers move at different speeds?

Im am currently doing my masters in geophysics (last semester) and before that I did a bachelor in geoscience. I assume by layers you mean the crust, the mantle and the core. These all have ...
user00007's user avatar
3 votes

What (if anything) can be learned from accurately recording tilt motion during seismic events?

The intent with this (very, very cool) device seems to simply be to improve hazard assessment and mitigation by providing higher resolution motion data. It reminds me of tiltmeters used on volcanoes. ...
user7939's user avatar
3 votes
Accepted

Time standard for IERS Bulletin A

Short answer: UT1 Long answer: The Julian Day (JD) is just a consistent day count since the beginning of the Julian period, that is January 12th 4713 BC. As the numbers tend to be large (today is ...
Camilo Rada's user avatar
  • 17.7k

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