Bluebulb Projects presents:
Enter a measurement to see comparisons

Your numbers are inaccurate, or your conversions aren't right. Why is that?

Most of the measurements on the website are stored and calculated using significant digits. This is a mathematical concept used to convey the precision of a given number. Measurements, both when they're actually measured and when they're recorded, are always imprecise, and the amount of imprecision usually depends on how large they are.

Consider one of the measurements in the database — the weight of an adult Blue Whale's heart. The size used by the website is 600 kilograms and when you enter a measurement, it's compared to that amount. But, it's not likely that a real Blue Whales heart measures exactly 600 kilograms and not one milligram more or less. In situations like this, the concept of significant digits is used to determine how close of a measurement 600 kilograms really is. The rules for significant digits are pretty basic:
1. All non-zero digits, and all zeros between non-zero digits are significant
2. Leading zeros are not significant
3. Trailing zeros may be significant — it's often hard to determine
4. When multiplying or dividing, the result should have as many significant digits as the operand with the smallest number of significant digits.
In our Blue Whale heart example, the measurement we have to work with is 600 kilograms, but a real heart might weigh as little as 550 kilograms or as much as 649 kilograms. By strictly applying the third rule of significant digits, we can assume that we know the correct figure in the hundreds place — the first digit, six — but the real measurement could be off by as much as 50 kilograms in either direction.

On the other hand, the measurement could really be accurate in the tens place as well. This is where the uncertainty of the third rule applies. It's possible that all real Blue Whale hearts would measure between 591 and 609 kilograms and the measurement is only variable by 9 kilograms in either direction.

Since we don't know whether the 600 is accurate to the tens place or maybe even to the ones place, the site assumes the greatest-possible level of inaccuracy and only relies on the six being accurate. That means that if you convert the weight of a Blue Whale heart into another figure, say ounces, the result can't be any more accurate than the original number. There are 35.2739619495804 ounces in every 1 kilogram, so a weight of exactly 600 kilograms would be 21,164.3771697482 ounces. But because there's only one significant digit in the 600 kilogram measurement, we have to apply the fourth rule of significant digits and we can't keep more than one significant figure in the result. In other words, we can only say that the weight of a Blue Whale heart in is about 20,000 ounces.

Sometimes, however, you'll see measurements in the site that are given in very accurate terms, with many digits after the decimal point. Those are usually circumstances where the item isn't a measured amount, but an amount set by a rule or a standard. The area of a basketball court is one such example and the size used by the website is 495.6377184 square meters. This is much more precise than the size of the Blue Whale heart, because the source of that measurement is the National Basketball Association (NBA) rulebook. It specifies the exact length and width (in feet) of a basketball court and all courts should (in theory) measure the exact length, width, and implied area specified by those rules. While most real courts won't be exactly this amount, our best estimate of the size of a "normal" basketball court is the size given in the rulebook.

Does this mean that all (or most of) the information on your website is wrong?

It might be fairer to say that nature isn't as precise as we'd like it to be. It's easy to ask a question like "How much does a Blue Whale's heart weigh?" and expect to get a single figure for an answer, but nature is full of variety. The fact is, some whales have bigger hearts or smaller hearts than others, so there's no one answer to the question. Furthermore, the researchers who actually had to go measure a Blue Whale's heart were probably in for a difficult task themselves. How do you measure a Blue Whale heart? You'd have a hard time moving it to a scale, so the measurement may be an estimate created using other inputs. And even if that wasn't the case, there's no such thing as perfectly accurate scale. Anyway, when the number is printed in an encyclopedia or scientific journal, some of the accuracy may be lost. Researchers and editors report their results according to how much accuracy is needed. There are probably not very many people who need to know the weight of a Blue Whale heart in really precise terms, so for most situations a level of accuracy to the nearest hundred kilograms is just fine. Measuring and recording measurements of real things is a difficult task because real things come in all shapes and sizes. Sometimes the best we can offer is an approximate comparison.

What can I do with this information?

You can do anything you want with the information here (as long as it's legal). But if you're looking for suggestions about what you could do with this information, here are a few:
• Use it in presentations to emphasize the largeness or smallness of a surprising figure
• Use it as a teaching tool for a lesson on the size of physical quantities
• Use it to help yourself understand the size of units you're not familiar with
• Or, just have fun seeing how your height or weight compares to that of other things
What's the difference between height and distance if they use the same units?

It's true that the units allowed for the height and distance categories are the same. It's also true that the items in those categories can be measured using the same units. The reason for the difference is to provide fairer comparisons, particularly for items in the height category.

Consider a few of the tallest items the website had when this FAQ was written:
• Olympus Mons, the solar system's tallest mountain, located on Mars, with a height of 27 kilometers
• The Challenger Deep trench, the depth of the deepest point on Earth, reaching 10.902 kilometers below sea level.
• The Burj Dubai, an office building in the Dubai, United Arab Emirates, and the tallest manmade structure in existence, reaching just 0.828 kilometers (828 meters)
Compare those with a few of the longest items here:
• The total length of The Great Wall of China, with a distance of 8,851 kilometers
• The Amazon River, with a distance of 6,437 kilometers
• The drive from Los Angeles, California to New York City, with a distance of 4,488 kilometers
As you can see, even the tallest things that have been discovered can't compare to just a sampling of the longest things available on the website. So if you're trying to compare the height of a building in your town to other things, it might not be fair to use the length of The Great Wall of China as a basis for measurement.

Everything on the site with a length measurement is placed into one of two categories — distance and height — based on whether they are, in their natural state, longer than they are tall or taller than they are long, respectively. If you don't care about the distinction when searching for results, feel free to use either one. There's also a link provided at the bottom of the height and distance results pages if you'd like to see the other set of results within the other category.

Why are some items in the volume category listed twice? What does "packed" mean?

Take a look at the picture of gumballs to the left. You'll notice that the gumballs have a lot of open space between them — the dark or shadowy spots in the picture. When you put a quantity of solid items, like gumballs, together in a container, you always have some empty space leftover where you don't have enough room to fit additional items.

Mathematicians who study examples this phenomenon call it the "packing problem." These mathematicians have developed several models to represent the way in which the objects are packed into the container — basically to represent situations that differ based on how carefully the items were packed. One of these models is called the "random close pack" model, which describes the method of packing a container by adding spherical items, shaking the container, and then adding more spherical items. In a random close pack situation, the model predicts that about 64% of the total volume of the container will be occupied by items and the rest of the space will be empty. This figure is referred to as "packing density."

If, on the other hand, you took all the gumballs, and melted them into gumball soup, you would fill 100% (or very nearly 100%) of the available space. These are the two results given for volume comparisons — one represents the total result if you were packing with 100% efficiency and the other represents what would likely happen in the real world — the total number of items you could fit in a container with some empty space left over.

Because the site's primary purpose is to provide comparative measurements, most of the research effort is spent on finding the measurement of each item. The source links are to the web page that documents the measurement of an item — our way of letting you know that these measurements aren't just made up. But the rest of the description is more like a "fun fact," which may contain information from another web page, or even combined information from multiple web pages. Hopefully these tidbits are interesting to read, and every attempt is made to make sure that the information is accurate, but listing the underlying research for these descriptions would make the site harder to use and to maintain.

What's the difference between tons, tonnes, long tons, short tons, and metric tons?

Measurements have been around for a long time and have been used by different groups of people to mean different things, in different places, and during different eras. The ton is a good example of this.

The ton, as it is now commonly used, is the same as a short ton (more on the term in a moment) and is a unit most commonly used in the United States and Canada. One (short) ton measures 907.18474 kilograms or 2,000 (avoirdupois) pounds.

The long ton (sometimes called the weight ton or imperial ton) is a unit that has mostly fallen out of use, but which was once popular in the United Kingdom. British law defined the long ton as 2,240 (avoirdupois) pounds, which equals 1,016.0469088 kilograms. The terms long ton and short ton were created to distinguish between these first two kinds of tons. You may still hear the word ton, but what that means will depend on what part of the world you're in.

The metric ton is the same as a tonne and is a unit used in the metric system. It measures 1,000 kilograms or 2,204.62262184878 (avoirdupois) pounds. (It's defined in SI as the mass of one cubic meter of water at 4°C) In the United Kingdom and most other countries which use the International System of Units (SI), this is the most commonly-used kind of ton. The spelling is from the French word for ton, as the French were the first to use the unit.

What is a _________ unit? I've never heard of it before.

Ever since human beings have been trading with each other, there's been a need for them to agree have a way of communicating with each other about physical amounts of things. Many different societies solved this problem in many different ways and the result is a legacy of different units in different language with different meanings. For information about a specific unit or for more information about units of measurement in general, see the following Wikipedia article: http://en.wikipedia.org/wiki/Unit_of_measurement

I'd like to provide a link to your website or write an article about it. Is that ok?

Of course! Feel free to contact me using the link below if you have specific questions and I'll do my best to respond. Otherwise, if you want to provide a link or a write-up but you don't need my input, just let me know using the contact link.

I'm writing a paper. How do I cite your website as a resource?

Each of the items on our website includes a source where the measurement was found. If you want to cite any of the comparisons in a paper, your best option is to visit those websites and cite them directly.

If you want to cite The Measure of Things directly, you can use the following formats:

• MLA Style:
• "[Your measurement]". The Measure of Things. Bluebulb Projects' The Measure of Things. Web. [The date you visited the site].
• APA Style