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

[gary350]

TL;DR

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?

 

[phinds]

Your finger is made of atoms and molecules. Can you see your finger? Can you see an atom?

A beach is made up of grains of sand. Can you see a beach?

 

[hmmm27]

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.

 

[Drakkith]

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.

 

[Dale]

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.

 

[tech99]

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.