Our atmosphere and the rotating Earth

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Discussion Overview

The discussion revolves around the forces that keep the Earth's atmosphere in sync with its rotation, exploring concepts related to motion, gravity, and the behavior of clouds. Participants examine the implications of Newton's laws and the nature of atmospheric movement, questioning how calm days can occur despite the Earth's rapid rotation.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that Earth's gravity and magnetic field play roles in keeping the atmosphere aligned with the rotating Earth.
  • Others argue that no force is necessary for the atmosphere to maintain uniform motion, as it continues moving with the Earth due to inertia.
  • A few participants question how clouds can appear motionless while the Earth spins at high speeds, proposing that clouds are not stationary but rather moving with the atmosphere.
  • There are claims that if the atmosphere were to move independently of the Earth, friction would quickly synchronize its motion with the ground.
  • Some participants express confusion about the apparent lack of delay in atmospheric movement relative to the Earth's rotation, questioning the mechanics behind storm movements.
  • Discussions include references to Newton's First Law and its implications for understanding motion in the atmosphere.
  • Participants highlight the complexity of local wind patterns and their effects on atmospheric behavior, noting that prevailing winds can differ significantly across different regions.
  • There are assertions that the atmosphere has had billions of years to synchronize with the Earth's rotation, suggesting a historical perspective on atmospheric dynamics.
  • Some participants emphasize that the atmosphere is not a separate entity but part of the Earth itself, complicating the understanding of forces at play.

Areas of Agreement / Disagreement

Participants do not reach a consensus, with multiple competing views on the forces affecting atmospheric motion and the nature of cloud movement. The discussion remains unresolved, with ongoing debates about the implications of Newton's laws and the behavior of gases in the atmosphere.

Contextual Notes

Limitations include varying interpretations of Newton's laws, assumptions about atmospheric behavior, and the complexity of local weather systems that may not be fully addressed in the discussion.

  • #31
pkt said:
I estimate the top of the motionless puffy cloud to be four miles above me. For it to be moving in sync with me the top must be moving much faster than I am as we rotate. I moved 700 miles in the last hour and the top of the cloud moved much farther. The top of the cloud moved much farther and faster than the bottom of the cloud. How is this possible? What force acts on the top of the cloud to move it faster than the surface of the Earth as we rotate? Newtons law does not explain this.
If you moved 700 miles in one hour, then for your latitude, in that same hour the top of that cloud four miles above you, in order to stay directly above you, would have had to have moved 701 miles, or 1 mph faster than you. This is not what I would call "much faster".
As to what would cause this to happen, You have to consider the nature of the air around you. It is made up of countless particles which are individually moving at high speeds of ~100's of meters per sec or better than 1000 mph, which are constantly colliding with each other and other objects such as the ground itself. (air pressure is actually the net force of all these air molecules bouncing of surfaces.)

So even if we were to assume that you started with a rotating Earth and an atmosphere that did not rotate with it, collision between the ground and air would transfer ground motion to air molecules striking it. These will, in turn, transfer motion to other air molecules via collision. This process will quickly work its way up through the atmosphere until the the net angular speed of of both the Earth and atmosphere match. This dragging process will be greatly helped by the fact that the Earth is not smooth but is covered with mountain ranges etc.

The reason we get winds at all is due to the uneven heating of the Earth's surface by the Sun. Warm spots create updrafts which draws air in from cooler areas to replace the rising air. For example, bodies of water tend to be cooler that land masses. So generally speaking, you get winds blowing off of oceans heading inland.( Something I'm well familiar with. I live in the Pacific Northwest about 100 miles inland. Many a time, we, on a hot summer day, have taken a trip to the coast, and as the day wore on, and the Sun heated the inland areas more, the wind off the ocean grew more intense as it fed the rising warm air inland.)

Include the fact only half the surface is being lit at anyone time and different latitudes receive the Sun at varying angles, plus the surface irregularities alluded to above, and wind patterns can be quite complex.
 
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  • #32
It is no more surprising that the atmosphere follows the Earth's surface than the air in a closed car (fan off) doesn't blow in your face. In neither case is there any "drag force" to keep the air from going at the same speed as the ground below.
Note that the Bernoulli effect is present because of the Earth's spherical shape. It causes moving air to follow a curved path which it wouldn't if the Earth's surface was cylindrical. Many features of the weather are due to the Bernoulli effect. (Google it to find some interesting things)
 

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