While search certainly has proven effective for discovering text content, there are significant technical challenges to video search.

搜索引擎对文字内容的搜索当然已经被证明是很高效的，但是对视频搜索来说就还有很大的挑战。

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Some highlight the philosophical challenges of discovering that life exists on Mars or elsewhere in the Universe, or indeed of finding that it does not.

有些人提出发现（火星或宇宙其它地方拥有生命时，或者发现火星没有生命时会遇到的哲学挑战；

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Their work becomes one continuous adventure as long as they manage to keep discovering new challenges in it.

对于这些人，只要能设法经常从中发现新的挑战，那么，工作就可以成为一种连续不断的人生探险。

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The competition kicked off on MTV.com on July 7 with the 20 candidates competing in a series of five Twitter challenges created with ZYNC from American Express that ranged from discovering a local band to interviewing celebrities including Sean Kingston.

ENGADGET: MTV crowns its first Twitter jockey, remains mum on the prospect of actually showing music videos