主题：【记录】关于宇宙的一段对话 -- 出尘

是我跟一位天文学教授的对话。我是“问”，他是“答”。我的水平有限，问题也比较可笑，请大家将就着看。

问: 宇宙的外面是什么？

答: 宇宙的外面可能是别的宇宙，也可能没有外面

问: 那我们的宇宙有边？

答: in the standard model, there is no edge

问: 那“往外膨胀”，那个外是哪里？是什么？

答: just expansion, not expansion outwards. expansion everywhere, in the same way

问: 嗯？难道还向里膨胀？

答: expansion is just the expansion of the basic scales

问: 没有中心点的？

答: distance between any two objects increases. no centre

问: 大爆炸最初发生的地方呢？

答: everywhere

问: 听着不太对头

答: you are right, quite rediculous.but this is the standard model

问: 不是物质极其集中于某地么

答: no, just density everywhere was much higher

问: 然后同时爆炸？不可思议

答: expansion. not explosion. give you one example

问: 有个初始时间的呀

答: when we look at very far distance places, we are look back in time, because of the limited speed of light. but to all directions, the universe appears the same. this tells you the expansion really happened everywhere

问: 哦！

答: of course the other possibility is that we are at exactly the center

问: 不应该

答: but not many astronomers believe this

问: 我也不信，没理由的

问: if we are not at the center, then the universe was infinite and still infinite. the only two possibilities. I actually believe we are at the center. more natural to me. last year I asked one student to study my model, but finally he cound not get any conclusion

问: 可是我总是不相信上帝一扔骰子，就正好是六六六，没那么巧

答: again only two possibilities. one is that there is only one universe, but created by god

问: 不像

答: or there are many universes, ours is just one of many. cannot prove which is right scientifically

问: 嗯。我又听说超光速是可能的

答: of course it is possible

问: 那相对论呢？

答: in the early universe you must have this. do not violate relativity

问: 为什么必须？

答: in early universe expansion is very fast. otherwise it could overcome the extremely strong gravity, because the density was too high

问: 听着不太对

答: give you one example of super-light speed

问: 不是超光速的只能是零质量吗

答: when you blow a bubble, all parts on the bubble will move simultaneously. their relative velocity can easily be super-light

问: 嗯？

答: this is because this is one event. only when two events with causal relationship cannot go super-light. the expansion of the universe is one event, so no problem.

问: 太牵强了，不符合相对论吧

答: no violation at all

问: 可是相对论说的是，任何有质量的物体，不能达到光速

答: who is the observer in the expansion?

问: 光速是不是应该是绝对的？ 我不觉得有相对的

答: of course

问: 那跟观察者没什么关系啊

答: but if you talk about the relative speed of two parts of the universe, the relative speed can be any value

问: 没道理，我不相信现代科学了。 都是自相矛盾的东西

答: no problem for me

问: 听着都是狡辩术

答: in relativity, observers are very important. no observer, no relative speed. so we cannot measure any speed more c

问: 为什么是so？

答: no reason, Einsten assumes this, and it is always confirmed by experiments

问: 是说，不能测量出超光速？

答: of course

问: 但它可能实际存在？是手段问题？

答: what you mean by existence?

问: 噢，不能测量就不存在？

答: there is one very difficult phenomenon in quantum mechanics

问: 什么

答: it seems to violate the C principle. for example if you have one particle to release two particles. because of conservation laws, the properties of two particles must satisfy certain conditions

问: 需要外部能量吧

答: so if two particles fly in opposite directions, before you detect them, you do not know which one has what property

问: 应该都一样似的

答: but once you mease one, you know immediately the properties of the other one

问: 可是测不准怎么说？

答: suppose you can selectively measure certain properties, for example, the spin, then you know the spin of the other one. spin is conserved precisely

问: 嗯

答: so this way you can communicate with the other station with super C. for example when you receive spin UP you dance. when he receives spin DOWN, he also dances. then you can synchronize your actions with super-C

问: 可是我记得，当初说，还是光速

答: this violate the principle that you cannot communicate with super-C

问: 比方两个光速反向离开，它们之间的相对速度还是光速

答: this is true. but with the quantum mechanical things, you may be able to communicate with super C. this phemonenon has been observed and studied for a long time. this is one example of super-C communication. in cosmology, there is also one phenomenon very strange. for example the easten side and western side have the same properties. but they are seperated so far that there is no why for them to communicate so that they can synchronize their properties

问: 谁的东西？

答: from us, of course, wne we observe the universe. we look to the east and west, we see the universe is the same

问: 不会吧？ 星座星云，不是对称的吧？

答: this is the reason some people proposed that in the early phase of the expansion, it was one event. on large scale, very symmetric. in one event, you do not have the super-c restriction. in fact the microwave background is extremely uniform on all directions. this was the first proof of the big bang theory.

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