Early Big Bang Processes
早期大爆炸过程
From the very beginning the universe had a very precise expansion rate that made possible the formation of galaxies and stars.
The universe is observed to be essentially "flat" in the sense that it is almost at the critical density at which it would expand forever. At that critical expansion rate it could form helium, whereas with a much faster rate only hydrogen would form. That rate also makes galaxies and stars possible, so that the heavier elements we are made from could be "cooked" in the nuclear fusion furnaces at the centers of stars. The universe retains the overall hydrogen-helium abundance from this early process.
宇宙被观测到基本上是“平坦”的，即它几乎处于临界密度，这种密度下宇宙将永远膨胀。在这样的临界膨胀速率下，它可以形成氦，而如果膨胀速率更快，则只能形成氢。这种速率也使得星系和恒星的形成成为可能，因此我们所拥有的较重元素可以在恒星中心的核聚变炉中“炼制”出来。宇宙保留了这一早期过程产生的整体氢-氦丰度。
| Division of energy between photons and massive particles
光子与有质量粒子之间的能量分配 | Expansion time.
膨胀时间。 |
| Particle population table
粒子数量表 | Example of energy and time calculation
能量和时间计算示例 |
从一开始就，宇宙有着非常精确的膨胀速率，这使得星系和恒星的形成成为可能。点击任何部分以获取更多细节。
Big Bang scenario
Reference
Weinberg, First Three Minutes
索引 大爆炸情景 参考 Weinberg，前三分钟
| HyperPhysics***** Astrophysics
HyperPhysics ***** 天体物理学 | R Nave |
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