I Can We See the Moon From 238,900 Miles Away?

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The discussion centers on the visibility of the Moon from 238,900 miles away compared to individual grains of sand. It is established that a single grain of sand cannot be seen at that distance due to its small angular diameter, while the Moon's larger angular diameter allows it to be visible. The conversation also touches on the visibility of germs, emphasizing that while individual germs are not visible, a larger quantity can be seen. The key point is that the human eye's ability to detect objects depends on the amount of light they reflect, which increases with the number of grains. Ultimately, the Moon's visibility is a result of its size and the light it reflects, surpassing the detection threshold of human vision.
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Optic vision question?
You can not see 1 grain of sand from 238,900. miles away with the naked eye so why can we see the moon it is billions of grains of sand?

We can not see 1 germ with the naked eye, can we see 1 teaspoon of pure 100% germs?
 
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gary350 said:
Summary:: Optic vision question?

You can not see 1 grain of sand from 238,900. miles away with the naked eye
You could see the results of a grain of sand hitting the moon at near ##c##. Or a speck of antimatter doing same at any velocity.
so why can we see the moon it is billions of grains of sand?
"billions" ? You mean like a couple of cubic feet of sand ?

I can barely see the keyboard in front of me and need a magnifying glass to read pretty much anything, so count me out of the "we" that can spot a small boulder from a quarter-billion miles away.
We can not see 1 germ with the naked eye, can we see 1 teaspoon of pure 100% germs?
Depends : are they magic, invisible germs ?

Zeno's Paradoxes weren't even paradoxes two and a half millenia ago, but mathematicians hadn't gotten around to formalizing their proofs for things that are mostly common sense, anyways.

The one you seem to be looking for is along the lines of "If we can't hear a single grain of barley dropping to the floor, then why can we hear a bushel of grain hitting the ground"... or something like that.
 
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gary350 said:
You can not see 1 grain of sand from 238,900. miles away with the naked eye so why can we see the moon it is billions of grains of sand?

We can not see 1 germ with the naked eye, can we see 1 teaspoon of pure 100% germs?
Yes, you could see 1 teaspoon of 100% pure germs. I'm not sure you'd like the look of it though.

As for the Moon, a grain of sand at that distance has far too small of an angular diameter to see. But the Moon's angular diameter falls well within the range of human visibility.
 
gary350 said:
Summary:: Optic vision question?

You can not see 1 grain of sand from 238,900. miles away with the naked eye so why can we see the moon it is billions of grains of sand?

We can not see 1 germ with the naked eye, can we see 1 teaspoon of pure 100% germs?
Grains of sand and germs interact with light, so they can be seen with some sort of optical sensor. The fact that the human eye cannot see a grain of sand at the distance of the moon but can see the moon is simply because it is a highly non-linear sensor.
 
Each grain does reflect light but the amount is below the detection threshold of the eye. As the number of grains increases, the amount of light increases and eventually reaches the detection threshold. In many cases like this, it is the noise present at the detector which creates a detection threshold.
 
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