Using Intensity to Measure A Character’s Strength

What is intensity?

Intensity is a measure of power over an area. It’s most often used for things like measuring the amount of power from sunlight in a given area, but we’ll be adapting it to measure the strength of a character’s feats. This will largely be replacing the more typical energy level measurements that you see in regards to feats, such as energy being compared to a yield of TNT.

Why use intensity?

Using pure energy values to compare feats leads to some weird results when comparing drastically different types of damage. For instance, an average human falling 4 feet would have kinetic energy from that fall equal to 840.35 joules. A .35 caliber handgun, on the other hand, is only going to be delivering about 330 joules of kinetic energy. But no one in their right mind would say that falling four feet hurts 2.5 times as much as being shot by a handgun. If we were only using the energy values, someone who did this to a bullet would be hurt by a short fall.

The reason for this discrepancy is because an energy value on its own doesn’t account for how concentrated an attack is. Intensity will account for this, giving us a way to more accurately compare attacks with widely different areas of effect.

Pressure might be a more “natural” fit (that being a measure of force over an area), but it’s based in units of force like Newtons, which are generally harder to understand and harder to convert to and from energy. Intensity is a measure of power, which means it uses watts. This is both easier to visualize (because there are tons of comparisons for power available) and is extremely easy to convert to and from energy.

How to calculate intensity from an energy value?

Say you already have an existing calculation for a feat that gives you the energy value of the attack. Let’s work through how to convert that to a measure of intensity.

To start with, make sure you have the energy value in joules. If you have a number in TNT equivalents, use something like this site to convert that to joules. I’ll be using the energy values I gave earlier for the bullet and the fall as an example, so that’s 330 joules and 840.35 joules respectively.

Next we need to find the timeframe that the energy transfer happened in. One second is a good default if you can’t find an exact time frame, so I’ll use that for the fall energy. For the bullet energy, I’ll just calculate the amount of time needed for the bullet to travel its own length. I’ll spare the calcs here, but that comes out to .000085 seconds.

Now we use that timeframe to convert energy to power. To do that, we just divide joules by the time frame. So the fall has a power of 840.35 watts and the bullet has a power of 3,890,198.7 watts. This is already starting to show why the bullet is far more damaging than a fall, but we’ve still got to compare the areas.

For the fall, we’ll assume that the person fell face down, so we’ll use half the surface area of an average person, which is .95 m². For the bullet, we’ll treat it as a circle with the diameter of the bullet, which would have an area of 255.03 mm². To make comparisons in the future easier, I’ll convert both to cm². That means the fall had an area of 9500 cm² and the bullet had an area of 2.6 cm².

Now we just need to divide the power by the area in order to get our final intensity in watts per cm². 840.35 watts / 9500 cm² means the fall has an intensity of 0.088 watts / cm². 3,890,198.7 watts / 2.6 cm² means that the bullet has an intensity of 1,496,230.27 watts / cm².

Now that we have intensity values, it’s super easy to see the comparative danger imposed by the fall and the bullet. We can also use Wolfram Alpha to easily get comparisons for the power that make intuitive sense (we can do this with energy as well, but power is generally easier to comprehend). We can also now know exactly how being bulletproof compares to being punched through a wall, set on fire, or anything else that we’re curious about.