In March 2015, the American space program sent astronaut Scott Kelly to live on a space station for a whole year, where he will not feel gravity as the space station orbits Earth. Scott Kelly’s twin brother, Mark, stayed at home. Scientists then plan to study the twins’ body chemistry, genetics, sight, and other data. This way, scientists can find out how living with and without gravity affects two identical people. What will most likely be a limitation for other scientists trying to recreate this study? There are ethical controversies over testing human subjects. There are probably very few astronauts with twin siblings. There are too many complexities involved in studying body chemistry, genetics, and sight. There is probably not enough technology to keep someone in space for an entire year.

because the vietnam war was fought in an especially brutal and untraditional way

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.