What Watt is what? An experiment with 27 candles.

27 candles on a coffee table

It’s cold today, and my new house has one of those annoying pay-as-you-go electricity meters with a horribly expensive energy company that I’m pretty much stuck with until I get it all changed to my preferred energy supplier.

It’s all electric heaters here, and loath to guzzle more electricity, I was doing ok in the cold until I realised one of my pet rats had started hibernating. That’s worrying, because rats don’t naturally hibernate. Something had to be done.

Now, I do have enough on the meter to get us through this cold patch, but I also have rather a lot of candles – a whole box full in fact – lying around since the move. And in my realisation that the candles could be placed on the coffee table far closer to my pets’ cage than the electric wall heater, lo and behold, a scientific experiment was born.

It’s a known fact to everyone who has stuck their hands too close to a fire that fires generate heat as well as light. So I wanted to know how much I could heat the room by burning candles. And I want to know the output in terms of Watts, so I can compare it to the power of my electric heater.

To start with, it is helpful to know what a Watt is. It’s a SI unit for power, measured in Joules per second.

Tea lights weight roughly 20 grams and burn for around 5 hours – that’s four grams an hour.
6 inch dinner candles weigh 60 grams and burn for around 6 hours – that’s ten grams an hour.
3 inch high pillar candles weigh roughly 300 grams and burn for around 40 hours – that’s 7.5 grams an hour.

So it seems that the tea lights burns the least grammage per hour and the tapers the most grammage per hour. But how does that convert to heat? Which is better?

I am going to approximate that all my candles are made from paraffin wax. Now, paraffin wax burns at about 43kJ per gram of material, or 43000 J per gram.
For my tealights, at 4 grams an hour, that’s 4 x 4300 = 172,000 J per hour
For my tapers, at 10 grams an hour, that’s 10 x 43000 = 430,000 J per hour
For my pillar candles, at 7.5 grams an hour, that’s 7.5 x 43000 = 322,500 J per hour.

I have 21 tealights, 3 tapers, and 3 pillar candles.
(21 x 172000) + (3 x 430000) + (3 x 322500) = 5 869 500 Joules per hour.

But remember, Watts are Joules per second. So we need to convert this.

There are 3600 seconds in an hour, so we divide our answer by this to get the Joules per second.
5 869 500 / 3600 = 1630.41667
That’s ~ 1630 Watts for my 27 candles.

Now, the average candle emits light at only around 0.05% efficiency. So the most significant part of that wattage output is as heat (infra-red) rather than visible light, and therefore it’s really negligible to try and calculate how much of that total radiative power is emitted under the visible spectrum rather than the infra-red so I’m just going to leave it out.

My electric heater produces 2000W (in other words 2000 Joules per second).
1630W for my 27 candles really isn’t all that bad in comparison. I know that the amount of joules per second will vary as the candles will run out at different times, and I know that this is a very sketchy exercise in a field I’m no expert in, but it’s still a pretty decent amount of energy being emitted.

For now, though, I am going to whack the heater on full blast in addition to burning the candles. And Porkchop, my wee pet that started this entire exercise, is certainly benefiting from this double output of heat.

Fun facts I didn’t know before I started this exercise: The temperature in the centre (blue bit) of a candle can get up to 1000 degrees Celsius! And light is measured in lumens, the SI unit of luminous flux (or the portion of radiative power falling in the spectrum of visible light).

So… this Higgs fella…

I feel like I should be writing something about this Higgs stuff, as it’s pretty big news for scientists everywhere, whether interested in particle physics or not. These kinds of discoveries tend to develop huge implications for very different areas of science.

My challenge, though, is to get through this without mentioning the dreaded G-word. Exotic as it is, and much as I love it in a magical sense, it tends to annoy me in scientific talk for some reason. The goddamn thing.

So what happened at CERN that was so amazing?


Well done, guys.

At a frequency of 126 GeV, with 5 sigma certainty (that means highest certainty) on the 4th of July 2012, the Higgs was discovered. It’s another reason to celebrate the 4th July, eh?

Time to rewrite the books.

Neutrinos are normal after all

So today it emerges that the strange results of the CERN – Gran Sasso neutrino experiment last year – whereby neutrinos appeared to travel faster than the speed of light, something impossible in a relativistic universe – were down to problems with the fibre-optics. It would have been interesting if the results had been true, and the whole thing certainly gave plenty of scientifically-minded people pause for thought, but it says just as much that the results aren’t true, because it is further confirmation of Einstein’s Special Theory of Relativity.

Neutrinos are subatomic particles, which can travel long distances through matter as they are only affected by the weak atomic force and by gravity. The OPERA experiment at CERN attempts to find out more about neutrinos by firing them from a neutrino cannon through the ground to a sister lab in Gran Sasso, Italy.  The aim had been to detect tau neutrinos from muon neutrinos as particles decayed, and nobody had been expecting a faster-than-light speed result. Back in March, they repeated the experiment with the ICARUS detector, which found no such anomaly.

The experiments that go on at CERN have long been a subject of media intrigue, and it’s rare to hear something so highly scientific talked about to such a degree by non-scientific folks. This time round, what with the increasing prevalence of scientists in the media, we had the neutrino experiment even more in the public eye when Prof. Jim Al-Khalili announced he would eat his shorts on live TV if the results turned out to be true. In the end, we won’t be needing to pass him the ketchup, we now have an explanation for the anomaly, and can rest assured that a few more people in the world now know about neutrinos… which is great!