一個(gè)從一艘沉船中挖掘出的史前器物可能是現(xiàn)在世上發(fā)現(xiàn)的最早用于導(dǎo)航的工具。海洋考古學(xué)家說(shuō)這個(gè)物體是一個(gè)星座命盤(pán)，海員在航行中用它測(cè)量太陽(yáng)的高度，以確定所在地方。這個(gè)星座命盤(pán)是在1503年在印度洋暴風(fēng)雪期間沉沒(méi)的一艘葡萄牙船艦中找到的。

The slim bronze disc was discovered during the excavation^{1 of the Esmeralda shipwreck2 a Portuguese3 vessel4 that was exploring the Indian Ocean when it sank in a storm in 1503.}

The object is decorated with a royal coat of arms, but laser scanning also revealed faint etchings around its edges, each separated by five degrees. It confirms that this is an astrolabe - an instrument used by mariners^{5 to measure the height of the sun above the horizon, enabling them to navigate6 the seas.}

only around one hundred of these items have been found, and this one most likely dates to the late fifteenth century, making it the earliest known example by several decades.