Saturday, September 04, 2010

Choice magazine to consumers: don’t eat white dwarfs

There is a Choice Magazine report advocating for stoplight rating of foods, to help consumers eat more healthily. Their rating system uses units of 100g/mL (see figure 1, below). That is tenths of a kilogram per milliliter. I don’t know what they are eating, but the densest known substance at the surface of the Earth is osmium metal, with a density of about 22 g/mL, or 0.22 100g/mL.

Their “green light” value for sodium is 0.3 100g/mL, which is about 50% denser than anything on Earth. For comparison, a pure halite crystal 1 centimeter on a side (salt conveniently grows in cubes) will contain 2.16 g/cc x 0.39 g(Na)/g(total) = 0.85 g sodium. In units of 100g/ml, pure salt thus has a value of 0.0085 100g/mL.

Never-the-less, they rate almost every cereal as having an orange or red light rating.

There can be only one explanation. While osmium may be the densest material at surface pressures, at higher pressures many things can be more dense. As an example, consider a white dwarf star. A white dwarf is the burned out core of a star which has run out of hydrogen fuel and collapsed into a super dense state. Although calculating a diameter (and thus density) is not easy, they are generally thought to be about a million g/cc, or a ton/cc. On the Choice Magazine scale, that would weigh in at ten thousand 100g/cc.

Of course, white dwarfs are mostly carbon and oxygen, not sodium. But lets assume that they have a solar O/Na ratio. Using the Asplund et al. (2006) values, the solar O/Na ratio is about 300. But since white dwarves have carbon, silicon, etc. in them as well, we should really look at the ratio of everything except H and He to sodium. This is about 600 (in other words, carbon plus nitrogen plus all the heavier metals are about as abundant as oxygen).

So a white dwarf sodium content, using choice magazine units, is about 16.7 100g/mL.

Figure 1. The traffic light rating table from the choice magazine report.

That is more than ten times the 1.5 100g/mL “red light” value they suggest.

So eating degenerate matter from the cores of burned out stars is not recommended by Choice. It contains too much sodium, and might give you high blood pressure.

M. Asplund , N. Grevesse, A. J. Sauval; The solar chemical composition; Nuclear Physics A 777 1–4 (2006)


andy said...

Thanks for posting this. While the health hazards of consuming neutron stars and black holes are well known to the general public, far too many people these days are unaware of the similar hazards posed by white dwarfs. Only the other day I came across a website promoting ingestion of white dwarf material as a cure for hair loss. This kind of activity is dangerous and should be condemned as a scam preying on vulnerable people.

Nick Barnes said...

You are being unfair. They say "Grams per 100g/mL" (an even more bizarre unit, suggesting some sort of linear mass response to density).

The intention is obviously "grams per 100g" for solids (that is, percent) and "grams per 100mL" for liquids (that is, not percent). They should just stick with percent, which consumers are more likely to understand anyway.

Kitchen Benchtops said...

The white dwarf tears itself apart, and you get one of the biggest and most violent explosions in the Universe: a supernova.