What if there were no atmosphere

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Discussion Overview

The discussion centers on the hypothetical scenario of Earth existing without an atmosphere and its effects on the day-night cycle, particularly the length of days and nights. Participants explore various factors, including angular momentum, moment of inertia, and atmospheric refraction, while considering both theoretical implications and speculative scenarios.

Discussion Character

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

Main Points Raised

  • Some participants propose that the length of days and nights would remain the same, but there would be no twilight due to the absence of an atmosphere.
  • Others argue that the elimination of atmospheric refraction would result in slightly shorter days, estimating a few less minutes of sunlight at sunrise and sunset.
  • One participant suggests that the Earth's moment of inertia would decrease without an atmosphere, potentially leading to an increase in angular velocity, thus shortening the day-night period.
  • Another participant counters that the Earth's angular momentum would also be less without an atmosphere, implying no change in the day-night cycle.
  • Speculation arises about the process of losing the atmosphere and its implications on Earth's rotation and tidal forces, with some participants questioning the assumptions behind these scenarios.
  • Concerns are raised about the need to clarify whether the discussion is about a "with vs without" or "before vs after" scenario regarding the atmosphere.
  • One participant mentions that if Earth had lost its atmosphere billions of years ago, it might now rotate at a higher speed due to smaller tidal forces.

Areas of Agreement / Disagreement

Participants express differing views on the effects of an atmosphere's absence on the day-night cycle, with no consensus reached on the implications for angular momentum and Earth's rotation. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants highlight the need for clarity regarding the assumptions made about the loss of the atmosphere and its effects on angular momentum and rotation. The discussion includes speculative elements that depend on hypothetical scenarios.

Ezio3.1415
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What would be the effect on day night period if there were no atmosphere? I mean would the days become longer or shorter? Why?PS:Admims,Trust me its not my homework...
 
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The days and nights would be the same length, but there would be no twilight.
 
Depending on how precise you want to be, you'd get a few less minutes of the sun being up due to the elimination of atmospheric refraction. Roughly 1 solar diameter at the horizon equals about 4 extra minutes each at sunrise/sunset if the sun is setting vertically:
http://en.wikipedia.org/wiki/Atmospheric_refraction

[edit: er - I calculated 2 min, but thought I remembered it being 4.]
 
The Earth's moment of inertia would be less,so angular velocity must increase to conserve the angular momentum... So day and night should be shorter...
Actually I asked the question,because many things can happen... I want to know what else are the factors?
 
russ_watters said:
Depending on how precise you want to be, you'd get a few less minutes of the sun being up due to the elimination of atmospheric refraction. Roughly 1 solar diameter at the horizon equals about 4 extra minutes each at sunrise/sunset:
http://en.wikipedia.org/wiki/Atmospheric_refraction
Oh, interesting.
 
Ezio3.1415 said:
The Earth's moment of inertia would be less,so angular velocity must increase to conserve the angular momentum...
No, its angular momentum would also be less, so there would be no change.
 
Ezio3.1415 said:
The Earth's moment of inertia would be less,so angular velocity must increase to conserve the angular momentum...
Conserve from what? We have to make up a story about how it lost its atmosphere or came to exist without one without changing its angular momentum. Now this is just idle speculation and storytelling.
 
russ_waters: yeah that's a big effect... Do u think my logic is logical?
 
now the Earth has to rotate with its atmosphere... So wouldn't the 'w' be a higher value if there's no atmosphere...
 
  • #10
Ezio3.1415 said:
now the Earth has to rotate with its atmosphere... So wouldn't the 'w' be a higher value if there's no atmosphere...
No, why should it. The atmosphere has angular momentum. If it didn't exist then the Earth would have less angular momentum.

Now, if you are not just thinking of a "with vs without" scenario, but are rather thinking of a "before vs after" scenario, then you need to specify the process you are considering for removing the atmosphere.
 
  • #11
If there was no atmosphere the oceans would evaporate. If the Earth had lost it's atmosphere 4 billion years ago, just as Mars did, it would now rotate at a higher speed since the tidal forces would be smaller.
 

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