Equivalent TL

Any sufficiently advanced magic is indistinguishable from technology. - Niven's Law

Equivalent TL is a concept introduced in GURPS Fantasy where magic is so common that it is effectively technology in of itself. As such it is a form of Divergent Technology but may not reflect the "actual" TL if you ignore the magic.

Concept

"Look at a number of commonly used spells, assign them to approximate TL equivalents, and see if these cluster around one or two TLs as usually defined; if so, use a rough equivalent TL in that range. If that doesn’t work, the TL concept may not fit the setting." It is advised that the GM should avoid assuming the setting will simply be 'just like TLx but with wizards'.

GURPS Realm Management shows that "various large-scale magics" can qualify as superscience meaning the above can be reworked into the following:

'Look at a number of commonly used non-superscience devices and equipment and see if these cluster around one or two TLs as usually defined. If possible go with the lowest TL to get the majority of the items and mark anything more then one step above the TL as superscience.' GURPS Adaptations supports this view by suggesting looking at the overall pattern adding superscience (^) to the TL.

Since the scale maxes out at TL12 (being 4 steps above the TL8 of 2007 ie effectively incomprehensible to TL8) and TL11 is just this side of understandable (-15 to anyone with TL8 skills) one should, if it is reasonably possible, avoid giving out TL10+.

Examples of Magic as Technology

Spell/Item	Comparable Device	Equivalent TL
Accuracy	Gunsight	5
Armor	Subdermal armor	10
Continual Light	Electric light	5
Create Air	Oxygen tank	5
Create Fire	Fire siphon	3
Cure Disease	Antibiotics	6
Extinguish Fire	Fire extinguisher	6
Foolishness	Alcohol	1
Ignite Fire	Matches	5
Lend Vitality	Emergency room equipment	6
Purify Water	Water filter	6
Seek Earth	Remote geosensors	7
Sense Foes	Intruder detection systems	7
Test Food	Chemical analysis	6

Divergent TL vs Equivalent TL

Equivalent TL is what the setting appears to be while Divergent TL is what it "actually" is for the purposes of calculating TL penalties with the superscience ("^") mark to help denote this fact.

Reality	Year	Actual TL	Equivalent TL; TL Category
Azoth-1	1632	TL(4+3)^	ETL9; Manned interplanetary spaceflight
Azoth-7	1780	TL(4+2)^	ETL12; Faster "interstellar" space flight
Britannica-5	1868	TL(5+1)^	ETL10; Antimatter bombs
Etheria	1890-1	TL(5+1), (etheric spacecraft, TL5^)	ETL9; Manned interplanetary spaceflight
Futura	Unknown	TL(5+1)^	ETL7: Manned spaceflight
Igor-1	1944	TL(6+1)^	ETL9 with some inventions
Roma Universalis	168 CE	TL3^	ETL9; Manned interplanetary spaceflight

The Nautilus of 20,000 Leagues Under the Sea (advanced submarine) uses cinematic sodium/mercury batteries which it must return to base to recharge. In GURPS Classic advanced submarine was listed TL(5+1) but at least one retcon gave it nuclear power (TL7). Where it actually would sit varies on the GM though the output of 1,870,000,000 kWs (519.44 MWh) is totally cinematic rivaling the output of the most advanced TL7/8 submarines built.

Reasoning

Using the superscience label this way can help prevent the need to send the TL of a setting into the 11-12 range to get everything to "work". It also allows dialing back the TL of a setting to something far less fantastic. So instead of TL11 for Star Trek and Star Wars one can dial them back to a far saner TL(6+3)^ (transtator; TL6^; Medicine; TL7^) and TL(6+3)^-(6+4)^ respectively.

Note on TL(x+y)^

The use of the superscience symbol for divergent technology that requires superscience to function ie TL(x+y)^ was set by Steampunk 2: Steam and Shellfire.

Examples from the Steampunk 2: Steam and Shellfire sample PDF:

• Electrolabe (TL(5+1)^)
• Mesmeric Wand (TL(5+1)^)
• X-Ray Goggles (TL(6+1)^)

Spaceships 7: Divergent and Paranormal Tech uses a TL(x+y^) variant:

• Ether Steamship TL(5+2^)
• Ether Ironclad TL(5+2^)