"Eating: radiation advantage?
 

I rolled up an autotrophic alien that "consumes" radiation.

What I want to know is how many rads per day would be required to equate to a normal diet in energy assuming strange biologicals that can harness most of it.

Ballpark figure only.

Re: "Eating: radiation advantage?
 

Wiki says a rad "the dose causing 0.01 joule of energy to be absorbed per kilogram of matter". Lets say your alien weights 70kg. That's .7 J per rad. A human needs about 8.3 MJ per day to stay healthy. So 11 million rads per day, assuming that my reading of Wikipedia is correct and the GURPS concept of a rad is anything like the real one.

Re: "Eating: radiation advantage?
 

Looks pretty reasonable, if 'radiation' means 'penetrating ionizing radiation'.

Re: "Eating: radiation advantage?
 

Yeah, if it doesn't then it could mean a lot of things. We have autotrophs that "eat" radiation on Earth too, we call them plants. :)

Re: "Eating: radiation advantage?
 

I must say that an alien generation system that produces autotrophs that have brains, or that move faster than inches per day, has some plausibility problems anyway, unless you choose to call something that walks around eating radioactive materials (which it stores internally for power generation) an autotroph.

Re: "Eating: radiation advantage?
 

Mobility could develop to solve a different problem than needing to seek food, conceivably.

Or the autotroph's energy source might not be as easy to passively harvest as sunlight. Though that seems harder to justify.

Re: "Eating: radiation advantage?
 

I can think of one alien species that functions off of absorbed energy and has mobility. Kryptonians.

Re: "Eating: radiation advantage?
 

Avoiding being food, possibly, but mobility is rather expensive; the energy available to an autotroph is generally inadequate to do much movement.

Re: "Eating: radiation advantage?
 

I had to go all the way back to Grimoire from 3e to get the best list of sources of radiation and it came up with 16.5 rads per minute for a gram of ingested radium.

So about 465 grams of radium would do if this beastie ate them. The good news is that this is a durable food source. Half-life of about 1600 years apparently.

So over 1600 years 230-something grams has decayed and needs to be replaced. Call it maybe 400 micrograms per day and this starts to look reasonable.

The problem is that the numbers for raw uranium ore or something like that won't be nearly so favorable.

Re: "Eating: radiation advantage?
 

It doesn't have to eat radioactive minerals, just be exposed to ionizing radiation. Such a creature might live in the orbit of a gas giant for example.