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The average human being is ‘hotter’ than the sun.

Obviously not. So why the title of this post? It is about the energy density of human beings compared to the Sun. ‘Hotter’ is of course loose terminology, but it makes it easier to appreciate.

As some will not have seen or heard in Prof Cox’s series that he said that the average human being emits 6000 times more energy than the sun per unit of weight. It was a quick statement that many missed. The point is, it was a staggering figure. Sorry I’m not here to spoon feed in which part of the series he said it. What – am I paid to spoon feed everybody? I am not! To spoon feed yourself, if you’re not a lazy cow, head to key facts at Encyclopaedia Britannica and NASA.

Normally people think of the sun as a very hot object and I am not disputing that (just in case). To have a play with the sun (image from NASA), you can grab it with your mouse and rotate etc.


The main point is that I have checked on the energy output of the sun per kg compared to that of the average human being.

Thus the total power output of the sun is  3.9 x 1026 watt. The mass of the sun is approx 1.989 × 1030 kg. Yes – I am aware that the sun is converting 4 million tons of matter into energy every second. But that is insignificant relative to the total mass. Ok – calm down! No need for a panic attack. Reliable calculations show that the sun has enough matter to last a few billion years. Humanity would probably self-destruct long before the Sun has a chance to go out or fry us to death.

The basal power output of the average human being is around 100 watts (+/- 20%), just breathing, sleeping or working on a computer etc. Trained athletes can generate between 400 to 1000 watts for brief periods on bikes, cross trainers etc.


Stupid: Are you a sun expert or an astrophysicist?

CW: No. I know where this is going.

Stupid: Why are you calling people lazy cows? That’s insulting.

CW: I did no such thing. [Clunk! Back in the box]



Human power density (HPD): I will take an average human being to be 70kg. So this makes for a power density of 100/70 = 1.43 W/kg.

Sun power density (SPD): From  the above foundations of evidence SPD is 3.9 x 1026 watt divided by 1.989 × 1030 kg = 1.96 x 10-4 W/kg. For those who would frown and sigh, and go “I’m neither a mathematician or sunologist“, that means the Sun emits 0.000196 watts per kg of its mass.

How many times more energy does the human being emit per kg? That’s HPD/SPD. You can get your calculators out to find the figure is 7293. Yes – so based on the estimates of mass of the sun, its energy output compared to energy output of the average human being – the human being emits 7293 times more energy than the sun per kg.

Another interruption

Stupid: There you are again being arrogant and trying to be a mathematician.

CW: WTF! How did you get out so quickly!?

Stupid: How would I know!

CW: Right – I’m simply doing calculations that anybody can do with a pocket calculator.

Stupid: I don’t have one.

CW: Yes – except you I meant.

Stupid: What’s the point of all this?

CW: I’m just trying to see if I can get close to Prof Cox’s 6000.

Stupid: Well clearly you haven’t. You’re rather dim, that’s why.

CW: I’ve had it with this nonsense of yours. [Zip! Gone]



Jeez – it’s to hard to write a blog these days when I’m being interrupted by this fool with the social media attitudes. Where was I?

Okay – as I was about to say, Prof Cox’s figure of 6000 is a good estimate. Estimates of the mass and energy output of the sun would vary a bit depending on which source of data you take. My 7293 is not bad, because I’ve seen other estimates of 8000.

The main point is that the energy density of the human being exceeds that of the sun several thousand fold.

It’s a conclusion that is very surprising and true.

This does not mean the human being is hotter than the sun.

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