It’s often really hard to get a meaningful sense what numbers *mean* – especially huge ones.

*What is a terabyte? A billion euro? A megawatt? Or a thousand people, even?*

I recently got our yearly gas bill, and saw that our consumption was about **1600 m3** – roughly the same as last year. We’ve insulated the house, we keep the thermostat set fairly low (19°C), and there is little more we can do – at least in terms of low-hanging fruit. Since the house has an open stairway to the top floors, it’s not easy to keep the heat localised.

*But what does such a gas consumption figure mean?*

For one, those 1600 m3/y are roughly 30,000 m3 in the next twenty years, which comes to about €20,000, assuming Dutch gas prices will stay the same (a big “if”, obviously).

That 30,000 m3 sounds like a huge amount of gas, for just two people to be burning up.

Then again, a volume of **31 x 31 x 31 m** sounds a lot less ridiculous, doesn’t it?

Now let’s tackle it from another angle, using the Wolfram Alpha “computational knowledge engine”, which is a really astonishing free service on the internet, as you’ll see.

How much gas is estimated to be left on this planet? Wolfram Alpha has the answer:

How many people are there in the world?

Ok, let’s assume we give everyone today an equal amount of those gas reserves:

Which means that we will reach our “allowance” (for 2) 30 years from now. Now **that** is a number I can grasp. It does mean that in 30 years or so it’ll all be gone. Totally. Gone.

*I don’t think our children and all future generations will be very pleased with this…*

Oh, and for the geeks in us: note how incredibly easy it is to get at some numerical facts, and how accurately and easily Wolfram Alpha handles all the unit conversions. We now live in a world where the well-off western part of the internet-connected crowd has *instant* and *free* access to all the knowledge we’ve ammassed (Wikipedia + Google + Wolfram Alpha).

Facts are no longer something you have to learn – just pick up your phone / tablet / laptop!

But let’s not stop at this gloomy result. Here’s another, more satisfying, calculation using figures from an interesting UK site, called Electropedia (thanks, Ard!):

[…] the total Sun’s power it intercepted by the Earth is 1.740×10^17 Watts

When accounting for the earth’s rotation, seasonal and climatic effects, this boils down to:

[…] the actual power reaching the ground generally averages less than 200 Watts per square meter

Aha, **that’s** a figure I can relate to again, unlike the “10^17” metric in the total above.

Let’s google for “heat energy radiated by one person”, which leads to this page, and on it:

As I recall, a typical healthy adult human generates in the neighborhood of 90 watts.

Interesting. Now an average adult’s calorie intake of 2400 kcal/day translates to 2.8 kWh. Note how this nicely matches up (at least roughly): 2.8 kWh/day is 116 watt, continuously. So yes, since we humans just *burn* stuff, it’s bound to end up as mostly heat, right?

But there is more to be said about the total solar energy reaching our little blue planet:

Integrating this power over the whole year the total solar energy received by the earth will be: 25,400 TW X 24 X 365 = 222,504,000 TeraWatthours (TWh)

Yuck, those incomprehensible units again. Luckily, Electropedia continues, and says:

[…] the available solar energy is over 10,056 times the world’s consumption. The solar energy must of course be converted into electrical energy, but even with a low conversion efficiency of only 10% the available energy will be 22,250,400 TWh or over a thousand times the consumption.

That sounds promising: we “just” need to harvest it, and end all fossil fuel consumption.

And to finish it off, here’s a simple calculation which also very much surprised me:

- take a world population of 7.13 billion people (2013 figures, but good enough)
- place each person on his/her own square meter
- put everyone together in one spot (tight, but hey, the subway is a
*lot*tighter!) - what you end up, is of course 7.13 billion square meters, i.e. 7,130,000,000 m3
- sounds like a lot? how about an area of 70 by 100 km? (1/6th of the Netherlands)

Then, googling again, I found out that 71% of the surface of our planet is water.

And with a little more help from Wolfram Alpha, I get this result:

That’s 144 x 144 meters per person, for everyone on this planet. Although not every spot is inhabitable, of course. But at least these are figures I can fit into my head and *grasp!*

*Now if only I could understand why we can’t solve this human tragedy. Maths won’t help.*