# Energy in a human question

1. Jul 24, 2008

### Mudo

This was accidentally posted in the general forum so I moved it over to a more appropriate section of the forum...

Hey guys:
Just needed to know if this logic/math is accurate. I haven't taken a science class since my undergrad days and it was ages ago so I am not too confident with all the concepts here. Just let me know if there is anything glaringly wrong about either the science or the math behind this:

The average human male is about 80 kg and the average human female is about 60 kg. So let us say that the average human is about 70 kg (since they are somewhat close to 50/50 of the population at large). The speed of light is given in meters per second and light travels approximately 300,000,000 meters per second. So to convert the human to energy (in joules) it would be=

E= 70 X 300,000,000 X 300,000,000 or 70 X 90,000,000,000,000,000 (90 quadrillion) or 6,300,000,000,000,000,000 (6.3 quintillion). So if the average person contains 6.3 quintillion joules of energy and joules is a measure of energy released per second (1000 watts would release 1000 joules per second for instance) we can surmise that the energy from one human being would be equivalent to the amount of energy released in one second from a 6,300,000,000,000,000,000 watt generator.
Currently the entire planet’s energy usage amounts to about 15 trillion watts (15 trillion joules per second). The energy of one person (if it burst out in just one second) is more than enough to power the entire planet for more than one-hundred hours ([6,300,000/15] / 3600 seconds in one hour). That means the energy released in one-second (if you converting a human entirely to energy) would be the equivalent of power that you could use to power the entire planet for nearly an entire work week. If you were to harness the energy of a person as you would in a lightbulb, that person could act as a 6.3 quintillion watt lightbulb and could power everything on Earth about half a million (420,000) times over (6.3 quintillion / 15 trillion).

2. Jul 24, 2008

### paw

At a quick glance your calculations look correct. Even the units of energy look right (kg*m^2/s^2). Keep in mind though, that would require the complete convertion of matter to energy, something that would only happen in a matter/anti-matter reaction. You'd need half a person made of matter and half a person made of anti-matter. Even then it's unlikely you'd get complete conversion since most of the mass would be blown away during the initial stages of the reaction. But yes, in theory a person contains enough mass to power our entire civilisation for a time.

3. Jul 25, 2008

### raptor5618

In the book I am reading it said something like if you converted all the energy in a single raisin it would be enough to power NY city for a week. I am not about to attempt doing the math but it is quite striking how much energy is contained in such a small object.

4. Jul 25, 2008

### thomasxc

its a very cool concept.

5. Jul 25, 2008

### paw

I agree it's quite striking the first time you encounter the idea. Keep in mind though, there's no easy way to use that energy. You would need to react the mass with an equal amount of anti-matter to obtain all the energy. We can make anti-matter but only in extremely small quantities and only by using more energy than we'd get back from the matter/anti-matter reaction. So until such time as we find a way to make and store large quantities of anti-matter cheaply this source of energy is denied us.

6. Jul 25, 2008

### Mudo

Thanks to everyone for the feedback on this one. I've got one more question... I have read that there is anywhere between 10-100 trillion cells in the human body. Would I be right in assuming that each cell in your body has more energy than what is released by the largest nuclear bomb?

Of course I know it is faulty logic to think "atomic bomb" = "the energy of one atom" and jumping from that to thinking "cell" > "atom" in mass, but I was wondering that nonetheless since I have heard that each cell has roughly 150 billion atoms (though it varies quite a bit depending on the cell of course).

7. Jul 26, 2008

### thomasxc

this is one of the reasons why i find physics to be so cool.

8. Jul 26, 2008

### HallsofIvy

Staff Emeritus
Are you going to volunteer to power the world for the next one-hundred hours?:tongue2:

9. Jul 29, 2008

### Mudo

Hehe, maybe.

So can anyone help me out on answering the question about the energy of a cell > the largest nuclear bomb or not? My lack of understanding as to what actually happens inside the atom bomb makes it to where I don't have a clear idea on where to start to answer this.

10. Jul 29, 2008

### paw

Sure, I'll give it a shot.

There are two basic types of nuclear bomb. The first is a fission device colloquially called an 'atom' bomb. It involves splitting (fissioning) massive, unstable, atoms into less massive, more stable, atoms. The second is a fusion device often called a 'hydrogen' bomb. It involves joining (fusing) light atoms into heavier atoms.

In both cases the mass of the atoms created is less than the mass of the atoms destroyed. The 'missing' mass is converted to energy via the relationship E=mc^2. The process is very fast so the energy is released explosively.

Again, in both cases, the mass converted to energy is very small for the individual atoms that react but there are LOTS of atoms that are undergo the reaction. That's why there is so much total energy.

A typical bomb might contain a few tens of kilos of 'fuel' of which maybe a few grams of mass is actually converted to energy. So....

If you were to convert ALL the mass of a few grams of cells to energy it would be comparable to a typical nuclear bomb. One cell is clearly not enough. Something like the size of your thumb might do it IF it could all be converted to energy. As I said in posts above though, this could only be done if it could be annihilated with an equal amount of anti-matter. And since we can't make large quantities of anti-matter this is impractical.

11. Jul 30, 2008

### thomasxc

why cant we make larger quantities of antimatter?

12. Jul 30, 2008

### paw

Two main reasons. It requires far too much energy (read 'costs far too much'). It takes more energy to make anti-matter than the energy you'd get back out by using it. Second, it's very difficuly to store anti-matter since it wants to react with matter. It has to be stored in a magnetic 'bottle' and I don't think there's a completely stable magnetic 'bottle'.

13. Jul 30, 2008

### Razzor7

Not even close. You need a few grams to equal the destructive force of a good sized nuke. You need more than half a gram to rival the bomb dropped on Hiroshima, and our nukes have improved considerably since then.

14. Dec 27, 2009

### rkyeun

The reason our process of creating antimatter is so woefully inefficient is because we do it by destroying normal matter (ultimately by solar power which gives us our mundane forms of energy) and then using that energy to MAKE antimatter. That's terribly inefficient. Especially since matter and antimatter are already positive masses, we shouldn't need to use this process at ALL. We should be able to find a way to directly convert an amount of matter into antimatter without fusion or fission. Matter and antimatter are after all mirror-images. We just need a four-dimensional rotation to pick up matter, flip it around, and put it back. If that's even possible.

15. Dec 27, 2009

### qraal

Baryon and Lepton number conservation prevent matter being changed into antimatter in our low energy world. At higher energies number violation becomes possible - the recently proposed electroweak stars are one possible example - but the output is typically as neutrinos. In theory matter can be converted into energy, but it's really, really HARD. Else it would happen spontaneously all over the place (inside white dwarfs and neutron stars, for example) and that just isn't observed.

16. Jun 15, 2011

### GrayBush

So specifically would anybody be able to answer the question: "How much energy would be released if one human cell was was completely converted to energy?"

17. Jun 15, 2011

### PhilDSP

There's a related observation from the Feynman lectures. He calculated, at least twice to make sure the figures were correct, that if all of the electrons in your body jumped suddenly a meter away from you they would be able to transport not the Empire State Building, not Mt. Everest, but the entire planet that distance.

18. Jun 15, 2011

### qraal

Name an estimate for cell mass then multiply by c-squared. Easy.

19. Jun 16, 2011

### Ahsankmc

Wow!
If this happens, the world will change all together.

20. Jun 16, 2011

### MartinJH

Yes and I'm quite enjoying life right now so if anyone plans on doing it please do it else where than earth. I thank you ;).