What are lightyears and why do scientists use them?

Light years are the distance is takes light to travel in a year. Scientist may use light years to measure the distance of how far away a star is, or other celestial objects.

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Most objects in space are so far away, that using a relatively small unit of distance, such as an astronomical unit, is not practical. Instead, astronomers measure distances to objects which are outside our solar system in light-years.

Source: coolcosmos.ipac.caltech.edu/cosmic_classroom/cosmic_reference/distance.html

if you are talking about current time the answer is no

if you are talking about when the colonies were developing the answer is yes

in the 1800s, chinese workers migrated to the united states, first to work in the gold mines, but also to take agricultural jobs, and factory work, especially in the garment industry. chinese immigrants were particularly instrumental in building railroads in the american west, and as chinese laborers grew successful in the united states, a number of them became entrepreneurs in their own right. as the numbers of chinese laborers increased, so did the strength of anti-chinese sentiment among other workers in the american economy. this finally resulted in legislation that aimed to limit future immigration of chinese workers to the united states, and threatened to sour diplomatic relations between the united states and china.