Galileo galilei obtained the first observational evidence suggesting the earth moved about the sun developed a theory of gravity to explain the motions of the planets made detailed measurements of the motions of the planets in the sky showed that the orbits of the planets were ellipses and not circles

the underground railroad (apocope of the metropolitan railroad) is a system of urban trains located within a city and its metropolitan area. it is characterized for being a massive transport of passengers in the big cities, uniting diverse zones and their environs, with high capacity and frequency and in segregated form to other systems of transport. metropolitan railroads are built underground or on the surface, although most systems use mixed models where sections are combined in both modalities.

1 - as a result, the metro tends to reduce car travel for two reasons: first, due to the greater transfer of users from the car and, second, due to the reduction in the acquisition of cars in homes located in sectors near the stations of the metro.

2 -the metro allows to contribute effectively to the achievement of all the objectives of an urban development policy: it improves the efficiency of the city's economy by reducing travel costs and also generates a higher level of activities in the city center, taking advantage of of the agglomeration economies.

3 -it is a clean means of transport, since it uses renewable energy (usually electricity), taking care of the environment and avoiding excessive pollution.

answer: a parliamentary system is a system of democratic governance of a state where the executive derives its democratic legitimacy from its ability to command the confidence of the legislature, typically a parliament, and is also held accountable to that parliament. in a parliamentary system, the head of state is usually a person distinct from the head of government. this is in contrast to a presidential system, where the head of state often is also the head of government and, most importantly, the executive does not derive its democratic legitimacy from the legislature.

countries with parliamentary democracies may be constitutional monarchies, where a monarch is the head of state while the head of government is almost always a member of parliament (such as the united kingdom, denmark, sweden, and japan), or parliamentary republics, where a mostly ceremonial president is the head of state while the head of government is regularly from the legislature (such as ireland, germany, india, and italy). in a few parliamentary republics, such as botswana, south africa, and suriname, among some others, the head of government is also head of state, but is elected by and is answerable to parliament. in bicameral parliaments, the head of government is generally, though not always, a member of the lower house.

parliamentarianism is the dominant form of government in europe, with 32 of its 50 sovereign states being parliamentarian. it is also common in the caribbean, being the form of government of 10 of its 13 island states, and in oceania. elsewhere in the world, parliamentary countries are less common, but they are distributed through all continents, most often in former colonies of the british empire that subscribe to a particular brand of parliamentarianism known as the westminster system.

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