百科知识视频之煎蛋小学堂51 我们会随着宇宙的扩张而变大吗？

Physicists tell us that the universe is expanding,but does that mean we expand with it? I mean,if so,wouldn't no one notice because everything would scale up,at the same relative size and it would seem like nothing had changed? Well,the truth is,the universe isn't expanding.

物理学家告诉我们 宇宙在扩张，但这是否意味着我们也在变大呢?我是说 若真如此 不是应该没人注意到 因为所有的东西 都在同比例放大 因而看似一切都没变过吗?真相是 宇宙并不在扩张。

Space is,Of course,everything else in the universe is "in"space,and ignoring the influence of any other forces,when the space between things expands,those things will appear to be carried farther apart.But there are other forces in the universe,and their strengths aren't directly affected when space expands.

而空间在扩张 当然 宇宙中的一切都在空间“之内”，忽略其他力产生的影响，当事物之间的空间扩张时，这些事物看起来像是被拆散到更远处。但是宇宙中还有其他的力，当空间扩张时 它们的强度并不会被直接影响。

For example,gravity and electromagnetism are able to hold atoms and solar systems together,because these forces are too strong for the slow expansion of space to overcome,Think of it like this-if you and your cat are standing on a piece of ground.that starts to stretch horizontally between you,the ground will pull you and your cat away from each other.

比如 重力和电磁力可将原子 太阳系等拉到一起 因为这些力要远大于克服空间缓慢扩张所需的力。这么想想看 如果你和你的猫都站在一块地面上 地面开始在你们之间水平拉伸，并将把你和你的猫拉离对方。

But if the leash is strong enough -in particular if it's stronger than the friction force between your feet and the ground,it'll hold you and your cat together as space expands beneath you.In the real universe,it's the strength of the electromagnetic force that determines the effective sizes of particles,atoms,and molecules,so that even if the space they're in expands,the molecules don't.

但如果皮带够结实 尤其是，如果它强于你的脚和地面间的摩擦力的话，当你脚下的空间扩张时 它能把你和你的猫拉在一起。在真实的宇宙中 是电磁力的大小 决定着微粒 原子和分子的有效直径 因而即便其所处的空间扩张 这些分子不会扩大。

Electromagnetism is basically the leash that holds atoms and molecules together,and gravity is the leash that holds solar systems and galaxies together,Only over super super long distances is gravity's attraction weak enough,and the cumulative expansion of all that space big enough to cause galaxies and galactic clusters to actually grow more distant from one another over time.we know this because the light from distant galaxies gets red-shifted as it's stretched by the expansion of the space it's traveling through.

电磁力基本上就是那将原子和分子拉在一起的皮带 而引力也是将太阳系 星系等凝聚在一起的皮带。只有在特别特别远的距离下 引力影响才会足够小 空间扩张的积累影响才会足够大 并导致 星系和银河星团随着时间过去 相互间距离越来越远 我们知道这个是因为远处星云发出的光出现了红移 光波被所穿过空间的扩张拉长了。

Gravity certainly still pulls distant objects towards each other,but space expands faster,Basically,the cat is off the leash.

当然 引力仍然会将遥远的物体相互拉近，但是空间扩张更快。基本就是说 那只“猫”挣脱了皮带。