1924
A new galaxy
American astronomer Edwin Hubble concluded that Andromeda was not a spiral nebula (a large cloud
of dust and gas) in the Milky Way galaxy but an entire,
separate galaxy. Hubble’s discovery came after he measured distances to stars in Andromeda and found them farther away than the diameter of the Milky Way. We now know that Andromeda is around 2.54 million light years away and is 220,000 light years across.
一个新的星系
美国天文学家埃德温·哈勃得出结论，仙女座星云不是银河系中的螺旋星云（一大团尘埃和气体），而是一个完整的， 独立的星系。哈勃的发现是在他测量了仙女座恒星的距离并发现它们比银河系的直径更远之后。我们现在知道仙女座距离我们大约254万光年，直径为22万光年。
Discovery of PTFE
American chemist Roy Plunkett discovered polytetrafluoroethylene (better known as PTFE, or by its brand name Teflon) by accident while developing a new fridge coolant. PTFE is unreactive and offers very low friction, making it great for nonstick cookware,and as a lubricant on machine parts such as gears and bearings.
PTFE的发现
美国化学家 Roy Plunkett在开发新的冰箱冷却剂时意外发现了聚四氟乙烯（通常称为PTFE，或其品牌名称Teflon）。聚四氟乙烯无反应性，提供非常低的摩擦，让它变得很棒对于不粘炊具，并作为润滑剂机器零件，如齿轮和轴承。
