DEVELOPMENT DRAFT     The only stable URL is
Comments encouraged - (Mitchell Charity)
How Big Are Things?
Home     Welcome
small Real

big     solar system between galaxy

Building your own
    HowBig? Cube
    Big letter "a" poster
    Wavelengths poster
    Construction notes
    Print rulers
    Print a 10 cm cube
    graphpaper.pdf  .ps
Ball is 1/2 box
    an Arizona wildfire
    - Cosmic View
Scaling the universe
  to your desktop
A View from the Back
  of the Envelope

Fermi problems
Orders of Magnitude

Development cruft
    (Nov'02 course cruft)



 I suggest new visitors visit Welcome
To make things appear their true size on your screen, you can calibrate! :)

microfloor and micropaper perhaps have the most content.

Thanks for your help - Mitchell

What's new? (Last changed 2003-Nov-26)

A printable HowBigAreThings? Cube!
Assorted additions.
Arizona wildfires.
Big letter "a" poster.
Person height calibration.
Intro text added to home page.
First change in almost a year.

How Big Are Things?

I hope to make it easy for you to know how big things are.
Everything from atoms to galaxies.

The idea is to have rooms with different magnifications.
In one room, you are Godzilla, and people are the size of ants.
In the next room, the world looks like a road map.
And in the room after that, the Earth is a blue-white marble, floating in space.
Just ten rooms get you from your teeny tiny atoms to our really BIG Milky Way galaxy.

The next neat thing is that you already have a feel for how big some things are.
If I ask you, "How big is a can of soda?", you already know!
You are not going to think it is as big as your bathtub... no way.
And you are not going to think a can is as small as your finger.
You've held soda cans, and you know how big they are.
So we are going to do the same thing with buildings.
And with planets. And bacteria. And lots of other stuff. :)
We can even do some of them for real, making models we can really hold.
(Like a little Statue of Liberty. Or a virus that looks like a baseball with spikes).

So, that is what I'd like this site to do for you.
To help you get a feel for the sizes of everything.

Here is the Welcome page.

Thumbnail of micropaper.

Background / Vision

This site was inspired by Cosmic View and Powers of Ten (another, list). They are nifty, but have some limitations. I have found them hard to remember ("Was the Earth 10^6 or 10^7 meters?"). And it is not easy to compare objects spread over multiple pages ("What is the relative size of Moon and Sun?"). And few objects are presented, as the emphasis is on a broad-brush sketch of scale, rather than on the sizes of a rich set of objects. And finally, precision is hard to come by ("The Earth is what times 10^7 meters? Is it a big 10^7 or a small 10^7?"). So "Powers of Ten" is a terrific introduction to scale, but only gets you so far. This site attempts to pick up where "Powers of Ten" leaves off.

"How Big Are Things?" tries to make size something you can remember, use, and optionally calculate with. This site will have succeeded if watching the news, or talking with friends, you can quickly and easily figure out the rough size of anything physical. And hearing a size ("100,000 acres are burning in Arizona"), you have a feel for what it means. Whether this is something this site can really accomplish, is not yet clear. And it will work better for some folks than for others (eg, it works best if one thinks spatially, rather than say symbolically). But it is a start.

The approach taken is to break Powers of Ten into chunks of 3 orders-of-magnitude (each chunk is 1000x bigger/smaller then it's neighbors). Having 10 chunks is more manageable than having 30 pages. Each chunk is treated as 1, 10, 100, thru 1000, whatever-meters. So, for example, there is a 1/10/100/1000 kilo-meter chunk. Then each chunk is made tangible by treating it as a "room". In the "kilometer room", 1/10/100/1000 kilometer objects are 1/10/100/1000 millimeters big. Then, the rooms are filled with objects. For instance, in the "Megameter room", the Earth (13 Megameter big) is a blue marble (13 mm big). Jupiter is a striped softball. And the Sun is a big white person-high ball. This leverages our everyday ability to remember the rough size of things we handle. Then, we can draw/print/craft/gather appropriately sized models of objects. For instance, I have a real Earth-sized marble. And a cup of red blood cell sized M&M candies. We can decorate our real rooms to look like these whatever-meter rooms. And there we can stop. With rooms full of pretty objects. The universe at your finger tips. Everything from atoms to galaxies. No numbers. Perfectly suitable for kindergarten kids.

But we can also take it one step further. Numbers are easy to come by. Easiest are the orders-of-magnitude ("1, 10, 100, and 1000 kilometers are ten to the 3, 4, 5 and 6 meters"). You only need to be able to add and subtract simple numbers. You can even do it on your fingers. And then, if/when you do want greater precision, you can easily get it. On these web pages, you can just count squares on the graph paper background. And you can measure the models with a ruler. And then, later, as you become familiar with the sizes of everyday objects ("About how many millimeters long is your finger?"), you can often do it from memory. For example, the blue Earth marble, is, well, marble-sized. So more than 10 mm but less than 20 mm. So just by remembering that the Earth is a pretty blue marble, I know its diameter to within better than 50%.

So, that is the idea. That anyone can easily get a feel for how big things are. And then, with surprisingly little work, develop a rich and powerful quantitative mastery of size.

A strawman provocative statement might go like this: By early elementary school, people can have encountered everything from atoms to galaxies, view them as real tangible objects, and have a feel for their sizes. Late elementary school students can be doing length, area, volume, and Fermi problems, dealing with any object the physical world has to offer. This combination of familiarity with the physical universe, and adeptness at approximate quantitative reasoning, provide an interesting complementary/alternate approach to science education. There is no excuse for the current state affairs, in which engineering and science graduate students have only the most tenuous grasp of the magnitudes of even the simplest properties they have spent years studying. And finally, a familiarity with the rough sizes of everything physical is a prerequisite of basic literacy. <Flame off>. How's that for an eyebrow raiser. :)

Comments encouraged - Mitchell Charity <>

(c) 2000-2003 Mitchell N Charity. All rights reserved.
Noncommercial use is fine. Otherwise, ask.