数学英语 39 What Do Prefixes Mean in Math? - Part 2

by Jason Marshall

A few weeks ago, we began talking about the meaning of prefixes² in math. In particular, we talked about the prefixes used in the metric system to represent lengths smaller than one meter. Today, we’re going to continue this topic by talking about the metric prefixes used to describe lengths much longer than one meter. And, since we’re chatting about big numbers, we’ll also talk a bit about the future of a recently proposed prefix¹ for describing really big numbers.
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Review of Metric Prefixes
In the first part of this series, we introduced some of the logic³ behind the metric system of units—that is, the system of units established in 1795 and now used by the majority of the world to measure lengths in meters, centimeters, millimeters, and a bunch of other units based upon the meter. We also talked about the fact that this whole system of units has been extended by using a set of internationally agreed upon prefixes. In particular, we talked about the various prefixes used to break the meter up into smaller pieces. For example, a centimeter is one-hundredth of a meter, a millimeter is one-thousandth of a meter, the micrometer and nanometer are one-millionth and one-billionth of a meter, and there are more almost unfathomably tiny lengths continuing on from there.
But why do we need these other units? Why aren’t all lengths just measured in meters? Well, it’s simply because they make it a lot easier to write and talk about really small lengths. For example, it’s a lot easier to say that a typical human hair is between 20 and 80 micrometers long, rather than to say that it’s between 0.00002 and 0.00008 meters long—wouldn’t you agree?
The Original Six Metric Prefixes
We’ve also talked about the fact that the original six prefixes defined for use in 1795 were:
“milli,”
“centi,”
“deci,”
“deca,”
“hecto,” and
“kilo.”
We’re familiar with three of these (“milli,” “centi,” and “kilo”), but I bet most of you have never even heard of “deci,” “deca,” and “hecto”—until recently, I hadn’t either! And that’s simply because they’ve long fallen out of favor. But what were they originally intended for? Well, the decimeter represents a length of one-tenth of a meter (that is, 10 centimeters), the decameter represents a length of 10 meters, and the hectometer represents a length of 100 meters. My guess is that people found it plenty convenient to say that something is 30 centimeters, and didn’t really need the option of calling it 3 decimeters too.
Prefixes for Numbers Larger Than One
But the one thing we haven’t talked about yet are the prefixes used to describe numbers larger than one. Actually, you’re probably very familiar with the first one of these, “kilo,” which is derived⁴ from the Greek word “chilioi” meaning “thousand.” Given this, it should come as no surprise that one kilometer is 1000 meters, a kilogram is 1000 grams, and so on. So, what’s next? Well, “mega” comes from the Greek word meaning “great” and is used to represent numbers that are yet another 1000 times larger. In other words, a megameter is 1000 kilometers, or one million meters! So, how big is that? Well, it’s pretty big—the average distance from the Earth to the Moon is about 385 megameters.
In truth, we don’t often use “mega” to talk about distances, but it is used a lot in the computer world. Back in the day, the hard drive on my first computer was a “whopping” 850 megabytes. I really thought that was awesome⁵ at the time, but it’s almost laughable now. But what exactly does it mean? It means that my hard drive was able to store 850 million bytes worth of information. It sounds like a lot, but these days hard drive sizes are measured in gigabytes or even terabytes. What’s that? Well, “giga” comes form the Greek word meaning “giant” and “tera” comes from the Greek word meaning “monster”—so they must represent some really big numbers! And they do: “giga” means 1 billion, and “tera” represents one trillion! So a one terabyte hard drive can store one trillion bytes of information. Just to give a bit more perspective on how big these numbers are, the 93-million mile distance from the Earth to the Sun is equivalent to about 150 gigameters or 0.15 terameters!
Prefixes for Incredibly Large Numbers
So what’s even bigger? Well, next comes the prefix “peta” meaning one quadrillion (which is a thousand trillion), then “exa” meaning one quintillion (which is a thousand quadrillion), and finally “zetta” and “yotta”—which are each successively one thousand times bigger! For comparison, the distance to the next big galaxy⁶, Andromeda, is about 2.5 million light-years (meaning it’d take light 2.5 million years to travel there)—which is equivalent to about 24 zettameters. And the entire observable universe is on the order of a few hundred yottameters across.
Will More Metric Prefixes Be Added?
Interestingly, the “zetta” and “yotta” prefixes were only added to the metric mix in 1991, so development is still happening. In fact, there’s been an Internet-driven campaign to get the prefix “hella” officially recognized as meaning a number that’s 1000 times bigger than the prefix “yotta.” If that ever happens, the size of the observable universe would be a bit less than one hellameter. The “hella” movement began in Northern California where the word has long been used in phrases like: “That’s hella cool.” And lately, the movement has picked up some steam by getting a fair bit of national press coverage⁷. The fine folks at Google have even incorporated the prefix “hella” into their online calculator! (Just go to Google and type in “1 hellameter in meters”.) So, will “hella” stick? I don’t know, but I for one hope that it does.
Wrap Up
Alright, that’s all the math we have time for today. Please email your math questions and comments to..................You can get updates about the Math Dude podcast, the “Video Extra!” episodes on YouTube, and all my other musings about math, science, and life in general by following me on Twitter. And don’t forget to join our great community of social networking math fans by becoming a fan of the Math Dude on Facebook.
Until next time, this is Jason Marshall with The Math Dude’s Quick and Dirty Tips to Make Math Easier. Thanks for reading, math fans!
 

1 prefix   

n.前缀；vt.加…作为前缀；置于前面

参考例句：

• We prefix "Mr."to a man's name.我们在男士的姓名前加“先生”。
• In the word "unimportant ","un-" is a prefix.在单词“unimportant”中“un”是前缀。

2 prefixes   

n.前缀( prefix的名词复数 )；人名前的称谓；前置代号（置于前面的单词或字母、数字）

参考例句：

• The prefixes cis and trans are frequently applied to disubstituted cycloalkanes. 词头顺和反常用于双取代的环烷烃。 来自辞典例句
• Why do you use so many prefixes while talking? 你说起话来，怎么这么多中缀？ 来自互联网

3 logic   

n.逻辑(学)；逻辑性

参考例句：

• What sort of logic is that?这是什么逻辑？
• I don't follow the logic of your argument.我不明白你的论点逻辑性何在。

4 derived   

vi.起源；由来；衍生；导出v.得到( derive的过去式和过去分词 )；（从…中）得到获得；源于；（从…中）提取

参考例句：

• Many English words are derived from Latin and Greek. 英语很多词源出于拉丁文和希腊文。 来自《简明英汉词典》
• He derived his enthusiasm for literature from his father. 他对文学的爱好是受他父亲的影响。 来自《简明英汉词典》

5 awesome   

adj.令人惊叹的，难得吓人的，很好的

参考例句：

• The church in Ireland has always exercised an awesome power.爱尔兰的教堂一直掌握着令人敬畏的权力。
• That new white convertible is totally awesome.那辆新的白色折篷汽车简直棒极了.

6 galaxy   

n.星系；银河系；一群(杰出或著名的人物)

参考例句：

• The earth is one of the planets in the Galaxy.地球是银河系中的星球之一。
• The company has a galaxy of talent.该公司拥有一批优秀的人才。

7 coverage   

n.报导，保险范围，保险额，范围，覆盖

参考例句：

• There's little coverage of foreign news in the newspaper.报纸上几乎没有国外新闻报道。
• This is an insurance policy with extensive coverage.这是一项承保范围广泛的保险。