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Comment by RedNifre | Hacker News Reader

What a perplexing article.

Isn't a pixel clearly specified as a picture element? Isn't the usage as a length unit just as colloquial as "It's five cars long", which is just a simplified way of saying "It is as long as the length of a car times five", where "car" and "length of car" are very clearly completely separate things?

> The other awkward approach is to insist that the pixel is a unit of length

Please don't. If you want a unit of length that works well with pixels, you can use Android's "dp" concept instead, which are "density independent pixels" (kinda a bad name if you think about it) and are indeed a unit of length, namely 1dp = 158.75 micro meter, so that you have 160 dp to the inch. Then you can say "It's 10dp by 5dp, so 50 square dp in area.".

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Yeah, this isn't really that complicated. It's just colloquial usage, not rigorous dimensional analysis. Roughly no one is actually confused by either usage ("1920 by 1080" or "12 megapixels").

It's nearly identical to North American usage of "block" (as in "city block"). Merriam Webster lists these two definitions (among many others):

> 6 a (1): a usually rectangular space (as in a city) enclosed by streets and occupied by or intended for buildings

> 6 a (2): the distance along one of the sides of such a block

Another colloquial saying to back this up is that "Oh, that house is five acres down the road" or, for a non-standard unit, "The store is three blocks away". We often use area measurements for length if it's convenient.

The pixel is a unit of area - we just occasionally use units of area to measure length.

> Another colloquial saying to back this up is that "Oh, that house is five acres down the road" or, for a non-standard unit, "The store is three blocks away". We often use area measurements for length if it's convenient.

I have never heard someone use the first instance, and I wouldn't understand what it meant. I mean, I could buy that it meant that there is a five-acre plot between that house and where we are now, but it wouldn't give me any useful idea of how far the house is other than "not too close." Perhaps you have in mind that, since the "width" of an acre is a furlong, a house 5 acres away is 5 furlongs away?

I think your final sentence would be a more specific/more correct to say "five acres away", but in reality I don't think I've ever heard anyone use a furlong as a serious unit in conversation.

I have heard sentences like "the property line is two acres into the woods" and it was understood that he was using acre like you might use "block" in a city - "the property line is two acre widths into the woods". As you say, that's just a furlong, but I doubt either of us knew that at the time.

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