Some numbers are easy to visualize. If someone tells you they see three ducks on the lake, or that they just bought a dozen eggs, or that it might snow ten centimeters tonight, you probably have a good idea of exactly what that means. You’ve seen eggs and ducks and snow before, and in similar quantities. You can close your eyes and easily imagine what a dozen eggs looks like. We can relate to these quantities because they’re part of our direct experiences.
Other numbers are difficult or impossible to get an intuitive feel for. You’ve never seen 30 trillionths of a picogram before. You’ve never driven two and a half million light years. You’ve never spent $7 trillion. Consequently you probably can’t close your eyes and visualize these in a concrete way like you can with more familiar quantities.
If you had to jog a distance of 350,000,000,000 angstroms, that might feel like a daunting task, especially if you don’t know what an angstrom is. When we encounter a quantity that’s difficult to visualize, our brains do what they often do when facing a difficult task; they substitute an easier task instead. Your brain might just go, “Wow! Look at all those zeroes. Gee, that sounds like a pretty big number.” Of course, if you’re not feeling lazy you could do some easy math and convert that quantity into numbers and units that are easier to relate to, and you might find out it’s really not such a long jog after all.
Quantities can be made to seem particularly big or small by carefully choosing how they are presented. If someone wants to make some statistic seem small they might use an unfamiliar unit that happens to make the number come out small looking, and then hope that most people will be too lazy to convert it into a number that is more meaningful to them. For example, when this organization says things like this:
“Of the fresh water used [to process oil from the Alberta oil sands], less than 1% of the Athabasca River’s flow is extracted.”
clearly they want us to think “Wow! Less than 1%. Gee, that sounds like a pretty small number.” But how much water is that? Isn’t 1% of the flow of a major river still an awful lot of water?
There are plenty of other ways they could have described this quantity. They could have said that the oil sands require around 6000 Litres of water per second. They could have said it consumes the equivalent of about 17 thousand pop cans of water per second, or 4000 bathtubs per minute. They could have said it uses 70% more water than the city of Vancouver does (at 2010 rates).
But instead what they have done is to come up with a number that is difficult to relate to, but produces as small seeming a number as possible. It almost makes you wonder why they didn’t just say “Only 0.00000015% of the planet’s water is used each year to process oil from north Alberta.” (Perhaps they didn’t want us to start thinking about the vast amount of water the oceans contain, regardless of how small a fraction is being used to process this oil.)
What they’re definitely not going to do is make the ubiquitous jumbo jet comparison. Jumbo jets are huge structures, but they’re actually deceptively light for their size, so measuring weight in jumbo jets is what you do when you want to make a quantity seem very heavy. You also use the weight of the lightest version of the jumbo jet, and use its OEW - its weight with no fuel or cargo.
Obviously they’re not going to describe water consumption this way because it doesn’t put the desired spin on the number, but if we’re not lazy we can do some easy math and see what the less flattering way of stating their number is…
…and what they’re saying is that processing oil from Alberta requires a jumbo jet’s weight in water every 26 seconds.