Comments on Malament's " 'Time Travel' in the Gödel Universe"
Comments on Malament's " 'Time Travel' in the Gödel Universe"
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马拉门《哥德尔宇宙中的‘时间旅行’》评论
DOI：
10.1086/psaprocbienmeetp.1984.2.192499
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
Lawrence B. Sklar
中科院分区：
文献类型：
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作者：
Lawrence B. Sklar
在那些没有明确的绝对时间，因而也就不可能存在客观的时间流逝的世界中，仅仅是与自然法则的相容性，就能使人们对那些绝对时间可以被定义的世界中的时间的意义有一个清醒的认识。因为，如果有人断言这个绝对时间正在流逝，他就接受了这样一个结果，即客观时间是否存在（即，这个词的普通意义上的时间是否存在）取决于物质及其运动在世界上被安排的特定方式。这不是一个直接的矛盾;然而，导致这种后果的哲学观点很难被认为是令人满意的。（哥德尔，1949，第562页）哥德尔的评论是在试图反驳绝对时间对我们的重新强加的背景下提出的，即使是在相对论的背景下，由Jeans提出，他认为存在一个“宇宙时间”，这在理智的宇宙学中是可用的，并且允许时空在一个时间整体分解为空间，再一次在世界上重新引入了一个优选的时间，而不是任意移动的观察者的坐标或适当的时间。在具有封闭类时线的哥德尔宇宙学中，这样的宇宙时间显然是不可用的。我不认为哥德尔真的需要这样一种宇宙学来”反驳”金斯，因为我认为，概念反思向我们表明，即使这样一种宇宙学时间存在，它也很难恢复”绝对时间”，就像那个概念的前相对论意义一样。但我认为哥德尔的主张是正确的，即某种世界的纯粹物理可能性严重影响我们概念的健全性，即使我们的世界不是那种世界，并且思考封闭的时间型线的可能性如何影响一些熟悉的概念是值得的。
Ihe mere canpatibility with the laws of nature of worlds in which there is no distinguished absolute time, and, therefore, no objective lapse of time can exist, throws sane light on the meaning of time also in those worlds in which an absolute time can be defined. For, if someone asserts that this absolute time is lapsing, he accepts as a consequence that, whether or not an objective time exists (ie whether or not a time in the ordinary sense of the word exists), depends on the particular way in which matter and its motion are arranged in the world. This is not a straightforward contradiction; nevertheless, a philosophical view leading to such consequences can hardly be considered as satisfactory.(Gödel 1949, p. 562.)Gödel's remarks are made in the context of trying to refute the reimposition of an absolute time on us, even in a relativistic context, by Jeans, who argued that the existence of a" cosmological time", which is available in sane cosmologies and which allows for a global decomposition of spacetime into spaces at a time, once again reintrcduced a preferred time into the world over and above the coordinate or proper times of arbitrarily moving observers. In a Godel cosmology with closed timelike lines such a cosmological time is clearly unavailable. I don't think Gödel really needed such a cosmology to" refute" Jeans, since conceptual reflection• shows us, I think, that even if such a cosmological time exists it is hardly a restoration of an" absolute time" in anything like• the pre-relativistic sense of that notion. But I think that Gödel's claim that the mere physical possibility of a world of a certain kind bears heavily on sane of our concepts, even if our world is not of that kind, is true, and that reflection on how the possibility of closed timelike lines bears on some familiar concepts is worthwhile.