Is there such thing as an absolute measurement?

  • #1
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To want to know the exact quantity of an object whether it be it's length, width, weight etc... Doesn't an absolute measurement only exist in the math/our human Minds. Then go down to quantum scales and that gets even harder because from what point do we even measure from if there is no exact point (I think). Hopefully this is considered mainstream. Thanks in advance.
 

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  • #2
Astronuc
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Relatively speaking, yes, give or take.
 
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  • #3
Borek
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Does the charge of an ion expressed in units of elementary charge count as absolute?
 
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  • #4
Vanadium 50
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I have six pennies in my hand. Is six absolute?
 
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  • #5
DaveE
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I have six pennies in my hand. Is six absolute?
Yes. But is counting measurement? You only have 3 pairs of pennies.
 
  • #6
256bits
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You have somewhere between 5 and 7 pennies.

When you count to 5 you still have more uncounted but so you up the count to 6..
When you get to 6, you may have some more uncounted, but are unsure.
when you get to 7, there definitely is no penny, so you backtrack by 1 to 6.
Is that the last penny, you are unsure, so you backtrack once more to 5
Now some pennies left over so you count up, to 6
Is that the last penny, not sure, so count up to 7.
And so on....
you are always hovering between 5 and 7, forever, and ever,
 
  • #7
etotheipi
Yes. But is counting measurement? You only have 3 pairs of pennies.

Huh?

You have somewhere between 5 and 7 pennies.

When you count to 5 you still have more uncounted but so you up the count to 6..
When you get to 6, you may have some more uncounted, but are unsure.
when you get to 7, there definitely is no penny, so you backtrack by 1 to 6.
Is that the last penny, you are unsure, so you backtrack once more to 5
Now some pennies left over so you count up, to 6
Is that the last penny, not sure, so count up to 7.
And so on....
you are always hovering between 5 and 7, forever, and ever,

What?
 
  • #8
256bits
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Huh?



What?
Think about it.
When you count you have to look ahead - and count 1 after the amount there actually.
Certainly that comes natural to a person trained in counting.

The backtracking all the way to to 5 does seem kind of iffy, though.
More likely, one is hovering between 6 and 7 , with a mean of 6.5.
 
  • #9
etotheipi
Think about it.
When you count you have to look ahead - and count 1 after the amount there actually.
Certainly that comes natural to a person trained in counting.

The backtracking all the way to to 5 does seem kind of iffy, though.
More likely, one is hovering between 6 and 7 , with a mean of 6.5.

No, that's absurd. The most basic operation is incrementation; you start at zero, with all the pennies on one side of the table, and each time you move one across to the other side of the table you increment the total by one. You can count by scratching a line in the table each time you move a penny, or whatever.

Why the heck would you increment the total a further time, to 7, when you have no pennies left to move across to the other side of the table?
 
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  • #10
256bits
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how did you know there were no more pennies left to move, you checked, which is one more count.

it might be abstract,;
but if you take a ruler marked off in inches, and measure a line length, one will write down the length as being 6 ± 0.5. it's not 5 .5 and its not 6.5, but somewhere in between. A measurement is actually counting.
 
  • #11
DaveE
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You have somewhere between 5 and 7 pennies.

When you count to 5 you still have more uncounted but so you up the count to 6..
When you get to 6, you may have some more uncounted, but are unsure.
when you get to 7, there definitely is no penny, so you backtrack by 1 to 6.
Is that the last penny, you are unsure, so you backtrack once more to 5
Now some pennies left over so you count up, to 6
Is that the last penny, not sure, so count up to 7.
And so on....
you are always hovering between 5 and 7, forever, and ever,
Yup, you've nailed the math of counting. But, perhaps measurement requires counting AND the definition of what you are counting. It's not really that useful if I tell you the weight of a machine I'm shipping is 83. OTOH, you could bet that two of them would be 166, or 2 machines. "2 machines" contains useful information; I'm not sure "166" is that helpful.
 
  • #12
etotheipi
how did you know there were no more pennies left to move, you checked, which is one more count.

No, it's because I looked and observed that there were no more pennies on that side of the table? The counting was implemented operationally by scratching the table each time I moved a penny, so if I only have 6 pennies to move across, I never make a "7th count".

but if you take a ruler marked off in inches, and measure a line length, one will write down the length as being 6 ± 0.5. it's not 5 .5 and its not 6.5, but somewhere in between. A measurement is actually counting.

That's completely different, that's uncertainty! The measured length of the line can be taken to be a random variable, and the value of a measurement is taken from a distribution. Then the measured value must be quoted with some measure of uncertainty, e.g. a standard deviation, which reflects the limitations of the measuring apparatus.

The difference with pennies is that the measured value is taken from the integers, whilst for lengths it's from the rationals (which are themselves dense in the reals). To both quantities you might assign an uncertainty, although probably not for the pennies if you're only dealing with small numbers.

Yup, you've nailed the math of counting. But, perhaps measurement requires counting AND the definition of what you are counting. It's not really that useful if I tell you the weight of a machine I'm shipping is 83. OTOH, you could bet that two of them would be 166, or 2 machines. "2 machines" contains useful information; I'm not sure "166" is that helpful.

Well, obviously! That was sort of my point. You can look at it in two ways:

- either, you're measuring two different quantities: ##n_1 = ## the number of pennies, and ##n_2 = ## the number of pairs of pennies.
- or you're measuring the same quantity, the "amount" of pennies, but expressing the measured value in terms of two different sets of units. In this case the measured value in a certain unit scales inversely to the size of the unit.

In other words, what @Vanadium 50 said was completely precise, because he was measuring the number of pennies, and not the number of pairs of pennies, which is a different quantity.
 
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  • #13
DaveE
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In other words, what @Vanadium 50 said was completely precise, because he was measuring the number of pennies, and not the number of pairs of pennies.
Yes exactly. Precisely 6 pennies. Precisely 3 pairs. But not 6, and not 3.
 
  • #14
DaveE
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It's a bit hilarious, if you think about it. A forum where a bunch of STEM types, mostly with college degrees, are discussing the kindergarten exercise of how many apples are in the fruit bowl. We all know everything about this question. We are all correct.

I'm not a huge philosophy fan, but It seems pointless even in that realm.
 
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  • #15
DaveC426913
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how did you know there were no more pennies left to move, you checked, which is one more count.
No. Checking is not part of the counting.

Code:
while (uncounted_pennies > 0 {
    movePenny();
}

movePenny(){
    uncounted_pennies = uncounted_pennies - 1;
    counted_pennies = counted_pennies + 1;
}

The check (the "while") is not where the counting occurs.
The counting occurs when you actually move a penny.

(While this is written out as pseudocode, it's just as valid logic in wetware as it is in hardware.)
 
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  • #16
etotheipi
It's a bit hilarious, if you think about it. A forum where a bunch of STEM types, mostly with college degrees, are discussing the kindergarten exercise of how many apples are in the fruit bowl. We all know everything about this question. We are all correct.

Well, Terence Tao - one of the greatest living mathematicians - spent the first 15 or so pages of "Analysis I" explaining how to count.
 
  • #17
phinds
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Third grade math problem:
Q: Bob had 25 candy bars and ate 20 of them. What does Bob have now?
A: Third grade answer: Diabetes. Bob has diabetes now.
 
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  • #18
phinds
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you are always hovering between 5 and 7, forever, and ever,
Ridiculous. @Vanadium 50 does not hover. He has 6 pennies and he don't need no damn hovering !
 
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  • #19
DaveC426913
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A foot long ruler is exactly 12 inches long.

Technically, that's a definition, but it's just as easily a measurement.

Try measuring a foot long ruler in inches. Keep going to more accuracy* until/unless you start to see a discrepancy.

*or is it precision? I can never remember which is which...
 
  • #20
DrGreg
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Third grade math problem:
Q: Bob had 25 candy bars and ate 20 of them. What does Bob have now?
A: Third grade answer: Diabetes. Bob has diabetes now.
Blackadder:
I have two beans, then I add two more beans. What does that make?

Baldrick:
A very small casserole.

From Blackadder II by Richard Curtis and Ben Elton
 
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  • #21
256bits
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A foot long ruler is exactly 12 inches long.

Technically, that's a definition, but it's just as easily a measurement.

Try measuring a foot long ruler in inches. Keep going to more accuracy* until/unless you start to see a discrepancy.

*or is it precision? I can never remember which is which...
Didn't the foot long ruler length change depending upon who was king?
 
  • #22
DaveE
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Well, Terence Tao - one of the greatest living mathematicians - spent the first 15 or so pages of "Analysis I" explaining how to count.
Exactly why I switched to engineering after my first Algebra class.
 
  • #23
DaveC426913
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Didn't the foot long ruler length change depending upon who was king?
Perhaps the inch changed along with it...
 
  • #24
Astronuc
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I have six pennies in my hand. Is six absolute?
Exactly, my dear Watson. :oldbiggrin: Cheerio. Pip pip.
 
  • #25
Dale
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Temporarily closed for review, but don’t hold your breath.
 
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