Explaining the Lack of a Visible Edge in Shadows of Clouds over the Sea

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In summary: The sun's light wouldn't be able to get through to the surface of the cloud, blocking the view. A totally transparent cloud? The sun's light would be able to get through to the surface of the cloud, but the cloud would still cast a shadow. There needs to be a middle ground, where some of the sun's light is able to get through but not all of it.An area that is partially cloudy and partially clear? Maybe the cloud is low enough that you are able to see the underside, but high enough that the tops of the clouds block the view. In summary, you saw a shadow that didn't have an easily visible edge, and this could be explained by the radius of the sun, the distance to the sun
  • #1
goran d
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I have seen shadows of clouds over the sea. What could be the explanation? Let me explain why there needs to be an explanation:
Radius of sun: ~600000km
Distance to sun: ~150000000km
(assumed) distance to cloud: 2km
This means that there should be a 16 metre edge around the shadow where the shadow goes smoothly from dark to light. But there wasn't such an edge, at least not an easily visible one.
 
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  • #2
Keep in mind that the sun is a sphere, so you are getting almost no light from the left edge of it or the right. You can probably halve your estimate to 8m because of that.
 
  • #3
What will be the brightness in the penumbra with respect to the umbra and the bright area outside the penumbra?
 
  • #4
goran d said:
...at least not an easily visible one.
So what did you see? A sharp shadow boundary edge like from a building? How far away was the shadow, and at what angle where you looking at it? Where the clouds really 2km above, or maybe just 500m?
 
  • #5
rumborak said:
Keep in mind that the sun is a sphere, so you are getting almost no light from the left edge of it or the right. You can probably halve your estimate to 8m because of that.
This isn't how it works. Every point on the surface emits light in all directions, so the brightness is pretty uniform to the edges. You can see this in eclipse photos.
 
  • #6
russ_watters said:
This isn't how it works. Every point on the surface emits light in all directions, so the brightness is pretty uniform to the edges. You can see this in eclipse photos.

I think you misunderstood my point. I wasn't saying that the emitted light has some kind of directionality to it (I agree with you, it doesn't), but instead that if you section the "sun disk" into vertical slices, the slices towards the edge of the sun are shorter and thus contribute less to the overall shadow effect. Because of that, the penumbra will *look* thinner.
 
  • #7
goran d said:
I have seen shadows of clouds over the sea. What could be the explanation? Let me explain why there needs to be an explanation:
Radius of sun: ~600000km
Distance to sun: ~150000000km
(assumed) distance to cloud: 2km
This means that there should be a 16 metre edge around the shadow where the shadow goes smoothly from dark to light. But there wasn't such an edge, at least not an easily visible one.
Are you sure you don't see a transition zone? From what distance are you viewing the shadow?
 
  • #8
goran d said:
why there needs to be an explanation:
A totally opaque cloud?
 

1. What causes the formation of shadows over the sea?

The formation of shadows over the sea is caused by a combination of factors, including the position of the sun in the sky, the angle of the sea surface, and the presence of clouds in the atmosphere. When the sun is low on the horizon, shadows are longer and more pronounced. The angle of the sea surface also plays a role, as waves and ripples on the surface can create variations in light and shadow. Finally, the presence of clouds can further enhance the formation of shadows by blocking sunlight and creating areas of contrast.

2. How do shadows over the sea affect marine life?

The effects of shadows over the sea on marine life can vary depending on the species and their habitats. Some marine animals, such as fish and turtles, use shadows as a form of camouflage to hide from predators. Other animals, such as dolphins, may use shadows to their advantage when hunting for prey. However, shadows can also create areas of lower light and cooler temperatures, which can impact the growth and survival of certain marine plants and animals.

3. Are shadows over the sea a common phenomenon?

Yes, shadows over the sea are a common occurrence and can be observed in various locations around the world. They are particularly noticeable in areas with clear water and calm seas, where the effects of light and shadow are more pronounced. However, the specific formation and appearance of shadows over the sea can vary depending on the unique environmental conditions of each location.

4. Can shadows over the sea be predicted?

While the general occurrence of shadows over the sea can be predicted based on the position of the sun and the presence of clouds, the specific formation and appearance of shadows cannot be predicted with certainty. This is due to the constantly changing environmental conditions, such as wind and ocean currents, which can affect the behavior of light and shadow over the sea.

5. How do shadows over the sea contribute to scientific research?

Shadows over the sea can provide valuable information for scientific research, particularly in the fields of marine biology and oceanography. By studying the formation and movement of shadows over the sea, scientists can gain insights into the behavior of light and how it affects marine life and ecosystems. This information can also be used to better understand and predict weather patterns and climate change, as shadows can be indicators of atmospheric conditions.

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