Ask MetaFilter questions tagged with measurement

How many grains of sand until we're there...?

TigerMoth — Tue, 15 Dec 2009 12:30:27 -0800

Time&SpaceFilter: GoogleFu failing me here... Trying to RE-find specific time and amount measurement/approximation sites. 1. A site (perhaps found on the Blue, a few years back?) about time where one can enter, say, a birth date/time and determine number of days or hours or minutes or whatever someone's been alive AND the date/time on which the next major milestone (25,000 days, 500,000 hours, or whatever) occurs, other things too...

2. A different site which provides nice visual analogues for amounts. Something like 100 is roughly the number of seats in a section of a baseball stadium (?), that sort of thing.

These were both fairly unadorned sites, and probably not related (though they may have been).

Preparing to go through a wormhole over the holidays, so I was thinkin' these might be useful again... ;)

Highway measuring devices...maybe?

brandman — Fri, 09 Oct 2009 10:20:14 -0800

Question about highway....measuring devices? Not exactly sure. So where I live (US midwest), there are these orange strips that are placed across the highway every so often - usually in three sets, usually in increasingly close proximity to one another (see here for my faithful recreation). I assume these are measuring traffic patterns, possibly including the various speeds and types of vehicles driving on the highway, but I'm not sure. And I've not yet figured out why they would need three sets with varied spacing. Anyway, I can't figure it out via google, so I figured I'd ask you all. Thanks!

Tools That Make Other Tools

toomanyplugs — Wed, 19 Aug 2009 10:27:04 -0800

How did we go from basic rough hand tools to the point of having really precise tools? Specifically, how do you make a better tool from the ones you have on hand? I came across an article on Make: Magazine about casting parts and building your own machine shop that got me thinking about how we as a species have arrived at very precise tools that are capable of creating a perfect sphere. The statement that got me thinking was:

"The order is important, because each tool requires the use of the previous machines in its construction."

How did we progress from only bare hands to these very precise machines? What fundamental laws of the universe can be harnessed to build these tools? I would expect that it required the development of measuring devices that could also become more precise.

Some of the other things that got me thinking:

The "Universal Measure" (as I found out from that scene in Stephenson's Quicksilver with Hooke and the mercury on the table), or the ideas of "straight", "square", geometric construction, linkages, etc.

Are there any good resources that speak about this? How would one go about recreating the level of precision we have now if trapped on a (technologically) desert island?

How is acreage measured on non-flat terrain?

Orinda — Tue, 18 Aug 2009 11:58:04 -0800

Surveying 101: How is acreage measured on hilly ground? Is the acre a measure of the surface area of the ground, or of the area inside an imaginary box that is superimposed over the ground? For example: Say I have a flat piece of ground that measures 4400 yards x 11,000 yards = 48,400,000 square yards = 10,000 acres. That's simple enough. But what if I have a piece of land that measures 4400 yards x 11,000 yards, but there's a mountain sitting in the middle of it? Is it still 10,000 acres, or is it more acreage because the mountain increases the actual surface area of the land within that rectangle?

(Answers to a previous question brought up the curvature of the earth as an issue that complicates rectilinear-grid surveying systems. This question is more about whether the local terrain affects what we call an "acre.")

Information Society

CRM114 — Thu, 21 May 2009 02:39:00 -0800

Is there an equivalent to free web metrics sites like Quantcast and Compete for the UK & Europe? Quantcast and Compete have long been my go-tos for getting ballpark figures for Website traffic, audience demographics etc. I'm in the UK now and I'm finding that Quantcast and Compete's US-based panels are vastly underrating traffic to UK sites.

Are there any similar services that cater to the UK or European markets?

Greenwich, Zulu & UTC: What's the difference?

cwarmy — Wed, 18 Mar 2009 21:08:27 -0800

What is the difference between Greenwich time, Zulu and UTC? Is Zulu and UTC a form of Greenwich time? I can't seem to find a page that states the difference. And do these forms of measurement not recognize daylight savings? Thanks in advance!

What software can make measurements in my pictures?

springload — Sun, 12 Oct 2008 07:28:49 -0800

Is there any good free software for putting a coordinate system on an image and extracting positions of objects? I have a lot of pictures, each of which contains a few crosses and some lines, and I'd like to determine the positions of the lines with respect to the crosses. The magnification and rotation of the images are not known in advance.

Ideally, I would import a picture, put a cursor on each cross and tell the program that they have coordinates (x1,y1), (x2, y2) and (x3,y3). Then I would place cursors on the endpoints of a line and the program would tell me what coordinates those endpoints have.

Do you know of a free program that does this?

Measure sunlight in yard to determine new garden spot

stbalbach — Sat, 23 Aug 2008 07:12:57 -0800

Is there a way to measure how much sunlight different parts of my yard get over the course of a day? For comparisons sake (not an absolute number) to determine where the best spot for growing vegetables is, which part of the yard gets the most sunlight over the course of a day. There are a lot of trees and so the sun comes and goes often, depending on where in the yard, and time of day as the sun moves.

Keep those pinchers to yourself, mister.

mykescipark — Fri, 11 Jul 2008 16:02:07 -0800

Where in L.A. can I get my body fat measured by water immersion?

How many times do I need to weigh a given object to overcome the scale's inaccuracy?

geoff. — Wed, 18 Jun 2008 13:30:04 -0800

If I have a scale that is accurate to .1 grams and I want it to be accurate to say, .05 grams, how many measurements do I need to take to do this? Can I even do this? The digital readout is up to the hundredths, even though the claimed accuracy is in the tenths. Would such inaccuracy follow a normal distribution? Could I correct this my measuring the object say, 1000 times to get a better estimation? I feel as if there's a way to do this, and that it might have been on a chemistry final at some point in my life.

No time like the present

Blazecock Pileon — Tue, 04 Mar 2008 23:24:33 -0800

I'm interested in aspects of benchmarking with the help of UNIX's time, specifically, what user, system and elapsed times correspond to, within the functional context of the system and the tested application. I have a very rough idea what the results of time point to in terms of CPU contention, with respect to the result of elapsed time, if elapsed is greater than the sum of user and system times.

• What does it mean that user makes non-system calls (what are those calls?)

• Likewise, what does it mean specifically that system makes system calls (what are those calls?)

Would I use user and system mean times to establish how to guide function profiling, within an application?

• What benchmarking results should I use as criteria for comparing one test result with another, all else the same?

For example, let's say I run sed -e 's/+/-/' inputdata on the same system, where different builds of sed have been compiled with different optimization flags and compilers.

• In this case, why would I choose the mean user time over mean system time as the criterium for comparing against like measurements of a "baseline" stock build of sed?

• Likewise, what are the caveats with choosing one measurement class over the other? (What are the downsides of using user time? system time? I suspect the answer to this will depend upon the calls made.)

If you have pointers to literature (other than the thousands of man pages on Google) I'd be appreciative of that advice, as well. Thanks in advance.

Help Figuring Out this Stick Thing

macinchik — Thu, 06 Dec 2007 20:18:37 -0800

I recall something that I believe I heard Carl Sagan say either in an episode of Cosmos or in one of his earlier books, that one could store enough information to hold an entire encyclopedia by putting a notch in a stick, if only one could measure where the notch lies to some absurd astronomically precise figure. Am I imagining this? Could have something to do with Anaximander, a pre-Socratic Greek philosopher.

This one has been bugging me for decades...

A Problem of Scale: Halfway in size between an atom and the universe

0bvious — Sun, 18 Feb 2007 16:10:04 -0800

"A human is halfway in size between an atom and the known universe"... This is a paraphrased quote I have come across several times. I like it. Who said it first? How true is it in the most literal sense? And, finally, what errors arrive in postulating a universe, or an atom, which can be measured AT ALL from our singular, relativistic, perspective? I found this quote from Cosmic Evolution which further complicates the whole relative size issue:

"Roughly halfway in size between an atom and a human, the amoeba has poor awareness and coordination. It generally responds only at the point stimulated, communicating the information sluggishly through the rest of its body. Although amoebas have developed a crude nervous system, living things that aspire to be more agile—and smarter—surely need quicker internal reactions." - link

Kind of sets another stage from which to view this question.

I also found this quote from Holmes Rolston which further complicates things:

"The human world stands about midway between the infinitesimal and the immense. The size of our planet is near the geometric mean of the size of the known universe and the size of the atom. The mass of a human being is the geometric mean of the mass of the earth and the mass of a proton. A person contains about 10²⁸ atoms, more atoms than there are stars in the universe. Such considerations yield perhaps only a relative location. Still, questions of place and proportion arise." - link

Who first made this often used statement? My earlier questions still stand :-)

Thanks...

Mead-making and measuring alcohol content

Blazecock Pileon — Wed, 10 Jan 2007 06:20:04 -0800

Measuring alcohol content without a hydrometer? So I am making a couple batches of mead. Unfortunately, this is the first time I've done this, and I forgot to measure the specific gravity before charging with the yeast starter.

Bubbling is slowing down, and I'm a few days away from transferring to the secondary vessel. I'm curious what the rough alcohol content will be in the final product.

Without having a starting specific gravity, I don't think I can use a hydrometer to make the relative calculation needed for an accurate measurement. I'm assuming I can't use 1.0 as the initial specific gravity because of the (alcohol-like) sugars and other compounds in the starting broth.

Is there a way, without employing the services of the local organic chem lab, to easily measure alcohol content of a generic substance?

My yard is not an option.

carsonb — Mon, 20 Nov 2006 20:53:46 -0800

What are some common household objects that can be used as standard measures? I forgot the size of a television I own, and it's been bugging me. And now that I think about it, there's about a zillion things I'd like to measure around my house. But I don't have a tape measure, and I can't be counted on to get one any time soon. So if I go to my pantry/closet/cupboard/bookcase/and on, what stuff inside is exactly 1 foot long? 6 inches? 1 decimeter? 1cm? etc?

Household instruments good for measurements other than length welcome as well.

Is there a way to determine the THC content of my "Green Dragon" mixture?

Tbola — Fri, 20 Oct 2006 21:06:22 -0800

I'm not a smoker, so I consume most of my THC by steeping 1/4 oz of weed in 26 oz of 151-proof rum. (After a week or so, I strain the rum and consume it about a tablespoon at a time. It suits my needs quite well.) I remember from my days of making homemade wine that there was a fairly easy way to estimate the alcohol content of wine by measuring the specific gravity before and after fermentation. Is there any similar method to get a ballpark idea of how much THC is in my rum?

Which light best portrays an accurate depiction of the whiteness of your teeth?

SeizeTheDay — Thu, 20 Jul 2006 10:13:31 -0800

What kind of light do you use to accurately measure how white your teeth are? There are at least three different kinds of light that I've seen my teeth in, all portraying the whiteness of my teeth at varying shades. Sunlight is the worst. My teeth (IMO) look terrible when viewed in sunlight. Contrast that with my incandescent bathroom light, where I think they shimmer. The third perspective is fluorescent, which is in the middle.

Which light portrays the most accurate depiction of the whiteness of my teeth? Which would you rely upon when making a judgment regarding a need to whiten (or at least get a professional cleaning)? Why? I'm all for a scientific explanation of light and teeth, BTW, though anecdotal evidence is appreciated as well. Thanks.

Are American cookbooks stupid?

betterton — Wed, 03 May 2006 18:01:42 -0800

Why do American cookbooks give ingredient measurements by volume and number instead of weight? Measuring ingredients by weight seems better because (1) it should give better results for things like flour, for which the volume depends on the history ("contents may settle during shipping") but the weight doesn't and (2) it avoids subjectivity (e.g., what constitutes a "medium tomato"?).

When I lived in France I noticed that cookbooks there give ingredient measurements based on weight.

So what's up with American cookbooks? I'm interested in any historical reasons for this, as well as explanations for why I'm wrong and volume/number measurements are better than weight.

measuring really long distances

rdr — Fri, 17 Feb 2006 23:10:23 -0800

Do we have any measurements that confirm redshift for distant objects? Reading this thread tickled a question that's been bothering me since high school. We have methods of measuring distances to nearby objects such as parallax measurements and measuring the brightness of cepheid variable stars. From that we get the redshift distance correlation. The part that has always bothered me is that as far as I know we extrapolate that correlation and use it as the only method of measuring the distance to remote objects. Do we have other methods for measuring distance to far away stuff? Is there enough evidence for the big bang that if we drop the observations based on redshift distance measurement that we can say that we live in an expanding universe and therefore the redshift distance correlation must be true?

How do I read the dipstick on my home heating oil tank?

ValveAnnex — Mon, 13 Dec 2004 23:00:07 -0800

How much oil is left in my 300 gallon underground home heating oil tank? I stuck the measuring stick in, and it came up wet from 15" on down. Assuming a standard, what is the general rule(r) of thumb?

Weather Stats

none — Sat, 11 Sep 2004 10:05:37 -0800

How is quantitative data for humidity, temperature etc translated into a qualitative descriptions of weather conditions? Eg. how do you get from the data on this page to the description?

This may well be a stupid question, so any pointers on understanding the weather would help too.