这个年代，旅游的种类很多，有专题的、历奇的、自驾的、舒适享受型的，喜欢自由一点的可自己安排行程，否则可参加旅行团，总之应有尽有，丰俭由人，但最昂贵的旅行，非space travel（太空旅行）莫属。
载人上太空一向都需要国家的财力、人力和物力才做得到，但有些私人企业正筹备私人太空之旅︰
SpaceX CEO Elon Musk aims to send two people into orbit around the moon – the first entirely private passenger flight ever. His original target was 2018, but the development of a new rocket reset the clock. The estimated price for a seat? Anywhere from $70 million to $175 million.
SpaceX就是其中一家搞太空旅游的机构。不只是上太空，而是“orbit around the moon”。 Orbit用作名词解天体等的运行轨道，用作动词则解move in orbit around，环绕轨道运行。 To launch a satellite into orbit around the Earth是把人造卫星发射进入环绕地球的轨道。
Orbit around the moon就是环绕月球。环月之旅每位收费7000万至1亿7500万美元，即五亿四千多万至十三亿六千多万港元。 “One roundtrip ticket to the International Space Station（国际太空站）via the Russian Soyuz rocket costs NASA approximately $80 million.”去近一点，乘俄罗斯的Soyuz火箭往返国际太空站也要每位八千万美元。负担得起这玩意的不是普通富豪，而是超级富豪。
但现在想到太空站有钱也不成，因为最近Soyuz火箭载美俄两名太空人上太空站时出事，太空人紧急“跳船”着陆无碍，但这支向来安稳、大大小小任务曾使用逾千次的火箭，出事原因未明，所以暂时不能再用，而Soyuz是目前唯一可以送人上太空站的火箭。
花这么多钱，太空旅游却不舒适，亦明显不安全。 NASA（National Aeronautics and Space Administration，美国太空总署）亦坦白指出，太空是极其凶险的地方，而最可怕是space radiation（太空辐射）。
The most dangerous aspect of traveling to Mars is space radiation. On the space station, astronauts receive over ten times the radiation than what’s naturally occurring on Earth. Our planet’s magnetic field（磁场）and atmosphere（大气层）protect us from harsh cosmic（宇宙的）radiation, but without that, you are more exposed to the treacherous（险恶的）radiation.
太空无重状态也影响血液循环：
Space travel plays havoc with our blood circulation. Human cardiovascular systems are designed to pump blood steadily around the body against the force of gravity（地心吸力）, which normally pulls blood towards our feet. But in the microgravity of space, blood moves up to the chest and head, giving astronauts puffy faces and raised blood pressure.
Play havoc with解使陷入大混乱，例如︰The typhoon played havoc with our daily life.（台风打乱了我们的日常生活。）既危险成本又高昂，为什么人类仍要不停上太空？
探索未知世界
NASA认为这是其中一个原因：
Humanity’s interest in the heavens has been universal（普遍的）and enduring（持续的）. Humans are driven to explore the unknown, discover new worlds, push the boundaries of our scientific and technical limits, and then push further.
The Orbital Perspective: Lessons in Seeing the Big Picture from a Journey of 71 Million Miles是国际太空站太空人Ron Garan对太空探索的现身说法。
