user: When was the theory of comparative advantage developed?

assistant: <think>
In an economic model, agents have a comparative advantage over others in producing a particular good if they can produce that good at a lower relative opportunity cost or autarky price, i.e. at a lower relative marginal cost prior to trade. Comparative advantage describes the economic reality of the work gains from trade for individuals, firms, or nations, which arise from differences in their factor endowments or technological progress. (The absolute advantage, comparing output per time (labor efficiency) or per quantity of input material (monetary efficiency), is generally considered more intuitive, but less accurate — as long as the opportunity costs of producing goods across countries vary, productive trade is possible.)

David Ricardo developed the classical theory of comparative advantage in 1817 to explain why countries engage in international trade even when one country's workers are more efficient at producing every single good than workers in other countries. He demonstrated that if two countries capable of producing two commodities engage in the free market (albeit with the assumption that the capital and labour do not move internationally), then each country will increase its overall consumption by exporting the good for which it has a comparative advantage while importing the other good, provided that there exist differences in labor productivity between both countries. Widely regarded as one of the most powerful yet counter-intuitive insights in economics, Ricardo's theory implies that comparative advantage rather than absolute advantage is responsible for much of international trade.</think>
The classical theory of comparative advantage was developed in 1817 by David Ricardo.

user: Please give me a short bulleted list of the principal fields of engineering

assistant: <think>
Main branches of engineering
For a topical guide, see Outline of engineering.

Hoover Dam
Engineering is a broad discipline that is often broken down into several sub-disciplines. Although an engineer will usually be trained in a specific discipline, he or she may become multi-disciplined through experience. Engineering is often characterized as having four main branches: chemical engineering, civil engineering, electrical engineering, and mechanical engineering.

Chemical engineering
Main article: Chemical engineering
Chemical engineering is the application of physics, chemistry, biology, and engineering principles in order to carry out chemical processes on a commercial scale, such as the manufacture of commodity chemicals, specialty chemicals, petroleum refining, microfabrication, fermentation, and biomolecule production.

Civil engineering
Main article: Civil engineering
Civil engineering is the design and construction of public and private works, such as infrastructure (airports, roads, railways, water supply, and treatment etc.), bridges, tunnels, dams, and buildings. Civil engineering is traditionally broken into a number of sub-disciplines, including structural engineering, environmental engineering, and surveying. It is traditionally considered to be separate from military engineering.

Electrical engineering
Main article: Electrical engineering

Electric motor
Electrical engineering is the design, study, and manufacture of various electrical and electronic systems, such as broadcast engineering, electrical circuits, generators, motors, electromagnetic/electromechanical devices, electronic devices, electronic circuits, optical fibers, optoelectronic devices, computer systems, telecommunications, instrumentation, control systems, and electronics.

Mechanical engineering
Main article: Mechanical engineering
Mechanical engineering is the design and manufacture of physical or mechanical systems, such as power and energy systems, aerospace/aircraft products, weapon systems, transportation products, engines, compressors, powertrains, kinematic chains, vacuum technology, vibration isolation equipment, manufacturing, robotics, turbines, audio equipments, and mechatronics.

Bioengineering
Main article: Biological engineering
Bioengineering is the engineering of biological systems for a useful purpose. Examples of bioengineering research include bacteria engineered to produce chemicals, new medical imaging technology, portable and rapid disease diagnostic devices, prosthetics, biopharmaceuticals, and tissue-engineered organs.</think>
chemical engineering, civil engineering, electrical engineering, mechanical engineering and bioengineering

user: What is a stinky slinky?

assistant: A stinky slinky is the nickname for a RV sewer hose. When emptying RV tanks an accordion-style hose is attached to the output port on the RV, with the other end being placed into a hole at a dump station. Levers are then pulled to empty the tanks: blank tank first (toilet contents), then gray tank after to remove any leftovers from when the black tank was emptied. Most people wear gloves when doing a tank dump. Given that the sewer hose is stretchy like a slinky, and removes toilet waste, the nickname “stinky slinky” is common.