# How many years to be considered as history?

User Amit Tyagi raised a good question in https://hsm.stackexchange.com/questions/504/why-was-pluto-demoted-from-the-list-of-planets#comment940_504

Coming to History, please explain what do we call as Historic on this site.....5, 10, 15.....how many years ?

User lwhhow in Yahoo! Answers defined history as 10 years back. User Ooker defines yesterday is history.

• Note that SpaceExploration Isn't fond of events that are ongoing and liable to change. Anything that's within a certain recent timescale (i.e. that could undergo a sudden status change) might not be great for HSM.
– HDE 226868 Mod
Nov 24 '14 at 19:31
• The Pluto question is a let me google that for you example. It is, in the weakest academic circles common knowledge, and it was only demoted about 8 years ago. I think it's a bad example of a borderline time question, and it does not even remotely resemble even a weakly challenging question of history. Nov 25 '14 at 2:45
• @J.W.Perry still, we should define what is considerd to be in history Nov 25 '14 at 4:12
• @Ooker Agreed. A legitimate question. It was lightly discussed before in the definition phase, but it has yet to be formally discussed here, and so it is good that you bring it up again for our meta. Nov 25 '14 at 4:36
• Just for a point of reference, from the definition phase: How recent can "History" be? There is no reason not to hash this out further for the record once here in our meta, as we are still in the beta phase. Nov 25 '14 at 5:13
• The definition may depend on the individual. For example, I consider as "history" everything which happened before 1960 (approximately when I started to read), but other participants may have a different opinion, of course:-) Nov 25 '14 at 15:25
• @J.W.Perry I think let me google that for you is a very casual statement on this platform. I believe 90% of the questions are answered from google. And i think people focused too much on my 1st question, out of the 2 questions. Is this widely accepted and there is/was no controversy over this ? needed a bit of research. There are many questions which were answered just after few minutes they were asked. Dec 1 '14 at 20:11

To give some basis for a debate, this is mostly a copy of my answer to the corresponding question on Area 51. As I yet failed to follow this site as much as I planned to do, this may not be up to date with some aspects already established on this Meta.

TL;DR: Do not define history by age, but by what it is about.

First of all, while I mainly write about science here, this is to keep the text readable. Very similar (and at times stronger) arguments apply to math.

Science idealistically always aspires to be up to date and thus it does not need to care about its history. Or with other words: Science cares about how our current view of the world is and how it is backed up¹, but not about how it came to be. Relatedly, the other scientific Stack Exchanges mainly have questions about our current state of knowledge, current definitions and notations or, in the case of Academia, about the current state of the scientific community.

In contrast to knowledge, society – the main subject of regular history – cares a lot about its own past. Hence it makes some sense that recentness is not the same to this site than to regular history or even to define history by something other than age.

Thus I would define history for our purposes as everything that is not about the current state of knowledge, notations, definitions, the scientific community, etc., but about how it evolved or how it was. As another criterion, the best answer should only be able to change due to new insights on past events and should not even be conceivable to change due to new insights on how reality works (i.e., scientific progress) or new notations and definitions coming into use.

To give an additional criterion for questions like (heavily exaggerating)

How did the theory of X change during the last week?

one could require that there should be some reason to assume a relevant change of the state of knowledge in the respective time frame. However, I do not expect such questions to pose a big problem and I think that they wouldn’t be asked like this in the first place, if there were no such reason.

Some examples:

• Why do we assume X?

is off-topic;

When and why was X first assumed?

is on-topic. However, for the latter, X should not be such an entirely brand new concept that there is no doubt that the answers to both questions are the same. In a rapidly evolving field, a few years might suffice for this, though.

• What is the prevalent theory for X?

is off-topic;

What was the prevalent theory for X, Y years ago?

is on-topic. Again, there should be a reason to assume that there was a significant change in the last Y years.

• Making graphene was as easy as removing layers with scotch tape and it's structure was postulated for years, why was it so difficult to discover?

is clearly on-topic by the above definition as it is about the past state of knowledge.

• Why was Pluto demoted from the list of planets?

is on-topic, though arguably not such an interesting question (but that’s for votes to decide and not a reason for closure).

¹ and of course how it can be improved