That We Know Of

Recently a colleague of mine and I have been talking about using the phrase "that we know of" in science education. I found myself using it in a rather extreme case. A student of mine commented (and I don't remember what lead into this) that there "are no animals on the moon." I retorted: "that we know of." I was half joking but I stand by the point I was making. Researchers are discovering things all the time and just because we assume there are no animals on the moon doesn't make it true. Just two days ago I read this article: http://www.cell.com/current-biology/fulltext/S0960-9822(08)00805-1 . It's about tardigrades (also known as water bears) being able to survive the vacuum and radiation of space. They're not on the moon but it's not really all that far off.

Field biologists have also recently discovered a new, very large species of crayfish in Tennessee. You can read about them here and here. So if you had said last month "There are no undiscovered species of giant crayfish in the rivers of Tennessee" you would have been dead wrong. If you had been a good science educator and said "There are no undiscovered species of giant crayfish in the rivers of Tennessee that we know of" you would have been exactly right.

It's just amazingly cool that researchers can still find relatively large animals that are basically in our backyards (well, not my backyard but probably someone's). And that is the essential spirit of the phrase "that we know of." Science is not a project of finding out what does not exist. We can never be certain about that. Ever. What we can be certain of are the things that do exist. So the next time you catch yourself making an exclusionary claim about the natural world, do your audience a favor (especially those of you who do work with young scientists) and add those four words.