From the D&D rulebook, we all know that a fireball has a 20' radius. The spell description also goes on to state:

"It can melt metals with a low melting point, such as lead, gold, copper, silver, or bronze."

So, let's assume a wizard of any level tosses a fireball at a 20' radius hemisphere of gold and targets the center of the flat side. By the rules, the entire mass of gold is in the area of effect for the fireball and presumably gets melted.

Gold is very dense and heavy, even more so than lead. At room (or dungeon) temperature, a 20' radius gold hemisphere has a volume of over 474 million cc's and a mass of approximately 9.16 billion grams. Gold is also a highly reflective material to many wavelengths of light, but we'll ignore that and assume that all of the energy of the fireball gets transferred into the gold.

The melting point of gold is 1044.18 degrees Celcius. The amount of energy required to raise a gram of gold by 1 degree is called the specific heat of gold and equals 0.0301 thermodynamic calories. To melt all our gold into an uncommonly large glob would therefore take a minimum of:

(1044.18 - 20.0) °C * (9,160,000,000) g * 0.0301 cal/g*°C
= 2.82 x 10¹¹ calories of heat.

The yield of a nuclear weapon is typically measured either in kilotons or megatons. These units refer to an early attempt to equate the explosive power of these devices to tons of TNT. However, since neither TNT nor a "ton" measure is truly standardized, a kiloton has been redefined as exactly 10¹² calories. In the last 50 years, the United States has at one time or another deployed nuclear weapons ranging in size from 10 tons to 25 megatons.

Under this scale, therefore, a fireball has a yield of at least 0.235 kilotons. This is slightly more powerful than any "man-portable" nuclear device believed to have been deployed. It's also the equivalent of the maximum possible energy release of 3.5 grams of deuterium, the best energy source by weight currently exploitable by humans.

Turning back to the description of a fireball, we find that the spell manifests itself as a "glowing, pea-sized bead." If we assume the bead is made of lithium deuteride, the most concentrated form of deuterium at normal pressures, this is consistent with these findings.

Conclusions:

1. When a fifth-level wizard claims he's "da' bomb," he may not be speaking figuratively.
2. Who says physics takes all the fun out of fantasy?

--
Michael Benveniste -- mhb@webwhat.com
I know, "get a half-life!"