<blockquote>
  <p>Is there any positive N on which it's agreed among astronomers that 10^-N is accepted as 0 (zero)?</p>
</blockquote>

<h2>No, there isn't.</h2>

<p>Astronomy overlaps with cosmology and there can be some pretty big and small numbers.</p>

<p>However most physical parameters also have <em>units</em> and the units chosen affect the numerical values.</p>

<p>A great example is the <a href="https://en.wikipedia.org/wiki/Jansky" rel="nofollow noreferrer">Jansky</a>:</p>

<blockquote>
  <p>The jansky (symbol Jy, plural janskys) is a non-SI unit of spectral flux density, or spectral irradiance, used especially in radio astronomy. It is equivalent to 10^−26 watts per square metre per hertz.</p>
</blockquote>

<p>In some cases one might even imagine going the other way and using L☉/ℓP² myr (solar luminosities per square planck-length per million years) which would require numerical values about 1x10^-110 times smaller.</p>

<p>Instead, astronomers and other scientists usually decide is something is small enough that it doesn't matter <em>within the context of the current discussion</em>. THey use words like <em>negligible</em> and <em>small</em> to indicate they're going to ignore it.</p>

CC BY-SA 4.0
2019-03-07T05:35:14.463Z
thanks for the detailed answer and your correction to my question. I am not a native English speaker. My q is more clear now and tells exactly what I meant. Best regards.
Andre Chenier
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2019-03-07T05:36:39.360Z
@AndreChenier thank you for accepting the answer, it's possible there may be more answers as soon as your question is reopened, so keep an eye on the question for changes. Welcome to Stack Exchange!
uhoh
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2019-03-06T23:04:55.510Z
2019-03-06T23:21:47.150Z
2019-03-06T23:21:47.150Z
uhoh
<p>Is there any positive N on which it's agreed among astronomers that 10^-N is accepted as, or treated as 0 (zero)?</p>

<p>I think one of the sciences that most precision is required is astrophysics.</p>

<p>I'm aware of my hardware capacity to lowest floating number, but that's not what I'm asking about.</p>

CC BY-SA 4.0
2019-03-06T19:55:53.303Z
I'm voting to close this question as off-topic because It's entirely situation-dependent.
Carl Witthoft
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2019-03-06T19:56:55.510Z
Hardware computing capacity has nothing to do with it.  Google "extended precision library" for example.  Are you asking about uncertainty limits?
Carl Witthoft
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2019-03-06T21:48:25.557Z
I don't understand what this is asking.  Of course in some models, certain aspects are considered negligible but that will vary from model to model.  Of course nobody actually thinks that a non-zero value is equal to zero. So "Of course not" seems to be the answer, but I think that is not what the OP is actually asking about. However I don't know what the OP *is* actually asking.
James K
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2019-03-06T21:49:18.097Z
@chappo 1E-N is notation for 1 x 10^(-n)
James K
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2019-03-06T23:23:46.280Z
I'm voting to close this question because I'm going to go ahead and vote to re-open as soon as it's closed. The question is both **on topic** and **clear what it is asking.**
uhoh
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2019-03-06T23:24:04.660Z
@CarlWitthoft The OP didn't ask what the number is, they asked if there is a number.    The answer is **no, because it is situation dependent**, not "I'm voting to close because it is situation dependent".
uhoh
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2019-03-07T03:50:21.860Z
@uhoh your voting strategy doesn't seem to make sense: you close so you can reopen? I agree the question is on-topic, but no parameters were given so it's unclear, which is why it was closed. The "On Hold" message invites the OP to edit it into a **useful** question; the links are worth reading, especially [Good Subjective, Bad Subjective](https://stackoverflow.blog/2010/09/29/good-subjective-bad-subjective/). If you think the question has intrinsic value, you could always have put the effort into editing it instead of answering it...
Chappo Hasn't Forgotten
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2019-03-07T04:42:25.827Z
@Chappo It makes perfect sense and I have seen others do this successfully as well. Four close votes within hours after a question is posted suggests a fifth is imminent. **I did indeed edit the question** to streamline and remove anything I though might be problematic, then issued the fifth close vote (which would have happened within hours anyway) so that I could start the reopen process with the adjusted wording.
uhoh
CC BY-SA 4.0
2019-03-07T04:47:08.133Z
@Chappo the underlying question is fine and doesn't need to be changed. *Is there an X such that...* is simple, clear, and is easily answered with *No, there isn't, because...* It's a perfectly reasonable question as asked.
uhoh
CC BY-SA 4.0
2019-03-07T05:44:43.553Z
Hi everyone. I am actually an old SO user & know the rules. With all my respect, I think this is a simple question with a clear statement. (I questioned the possible existence of parameter N and got a nice answer.) I tried however really could not understand the point of view of 'this is not a proper question' supporters. Lastly, many thanks to @uhoh for editing the q. best regards.
Andre Chenier
CC BY-SA 4.0
2019-03-07T16:02:57.493Z
Well, I could change to "unclear what you're asking."  I still assert it's situation-dependent.  Even astrophysicists will stop at the Planck length for nuclear behaviours, but I have no reason to pick a minimum value for, e.g., "which of these 2 stars is farther from Earth"
Carl Witthoft
<astrophysics><mathematics>
Is there any positive N on which it's agreed among astronomers that 10^-N is accepted as 0 (zero)?
Andre Chenier
# Is there any positive N on which it's agreed among astronomers that 10^-N is accepted as 0 (zero)?

(Asked by: username_0 on 2019-03-06)

Is there any positive N on which it's agreed among astronomers that 10^-N is accepted as, or treated as 0 (zero)?

I think one of the sciences that most precision is required is astrophysics.

I'm aware of my hardware capacity to lowest floating number, but that's not what I'm asking about.

**Tags:** astrophysics, mathematics
> **Comments:**
> **username_1**: I'm voting to close this question as off-topic because It's entirely situation-dependent.  
> **username_1**: Hardware computing capacity has nothing to do with it.  Google "extended precision library" for example.  Are you asking about uncertainty limits?  
> **username_2**: I don't understand what this is asking.  Of course in some models, certain aspects are considered negligible but that will vary from model to model.  Of course nobody actually thinks that a non-zero value is equal to zero. So "Of course not" seems to be the answer, but I think that is not what the OP is actually asking about. However I don't know what the OP *is* actually asking.  
> **username_2**: @chappo 1E-N is notation for 1 x 10^(-n)  
> **username_3**: I'm voting to close this question because I'm going to go ahead and vote to re-open as soon as it's closed. The question is both **on topic** and **clear what it is asking.**  
> **username_3**: @CarlWitthoft The OP didn't ask what the number is, they asked if there is a number.    The answer is **no, because it is situation dependent**, not "I'm voting to close because it is situation dependent".  
> **username_4**: @uhoh your voting strategy doesn't seem to make sense: you close so you can reopen? I agree the question is on-topic, but no parameters were given so it's unclear, which is why it was closed. The "On Hold" message invites the OP to edit it into a **useful** question; the links are worth reading, especially [Good Subjective, Bad Subjective](https://stackoverflow.blog/2010/09/29/good-subjective-bad-subjective/). If you think the question has intrinsic value, you could always have put the effort into editing it instead of answering it...  
> **username_3**: @Chappo It makes perfect sense and I have seen others do this successfully as well. Four close votes within hours after a question is posted suggests a fifth is imminent. **I did indeed edit the question** to streamline and remove anything I though might be problematic, then issued the fifth close vote (which would have happened within hours anyway) so that I could start the reopen process with the adjusted wording.  
> **username_3**: @Chappo the underlying question is fine and doesn't need to be changed. *Is there an X such that...* is simple, clear, and is easily answered with *No, there isn't, because...* It's a perfectly reasonable question as asked.  
> **username_0**: Hi everyone. I am actually an old SO user & know the rules. With all my respect, I think this is a simple question with a clear statement. (I questioned the possible existence of parameter N and got a nice answer.) I tried however really could not understand the point of view of 'this is not a proper question' supporters. Lastly, many thanks to @uhoh for editing the q. best regards.  
> **username_1**: Well, I could change to "unclear what you're asking."  I still assert it's situation-dependent.  Even astrophysicists will stop at the Planck length for nuclear behaviours, but I have no reason to pick a minimum value for, e.g., "which of these 2 stars is farther from Earth"  

---

## 1 answers

### Answer by username_3 on 2019-03-06. Score: 2 | Accepted answer

> Is there any positive N on which it's agreed among astronomers that 10^-N is accepted as 0 (zero)?

## No, there isn't.

Astronomy overlaps with cosmology and there can be some pretty big and small numbers.

However most physical parameters also have *units* and the units chosen affect the numerical values.

A great example is the [Jansky](https://en.wikipedia.org/wiki/Jansky):

> The jansky (symbol Jy, plural janskys) is a non-SI unit of spectral flux density, or spectral irradiance, used especially in radio astronomy. It is equivalent to 10^−26 watts per square metre per hertz.

In some cases one might even imagine going the other way and using L☉/ℓP² myr (solar luminosities per square planck-length per million years) which would require numerical values about 1x10^-110 times smaller.

Instead, astronomers and other scientists usually decide is something is small enough that it doesn't matter *within the context of the current discussion*. THey use words like *negligible* and *small* to indicate they're going to ignore it.

> **Comments:**
> **username_0**: thanks for the detailed answer and your correction to my question. I am not a native English speaker. My q is more clear now and tells exactly what I meant. Best regards.  
> **username_3**: @AndreChenier thank you for accepting the answer, it's possible there may be more answers as soon as your question is reopened, so keep an eye on the question for changes. Welcome to Stack Exchange!  

---

