And what is inside the gas discharge tube is gas at low pressure.

气体放电管里,有处于低压下的气体。

麻省理工公开课 - 固态化学导论课程节选

Let's say we start from some V1 and p1 here, so high pressure, small volume and we end up with a high volume low pressure, under constant temperature condition.

例如我们要从压强比较高，体积比较小V1，p1出发,到达低压强，大体积的末态，过程中温度不变。

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And so the photons hitting the wall actually put pressure on the wall, but the pressure is so low.

所以光子碰撞墙面,事实上在对墙加压，但只是压力很小。

麻省理工公开课 - 固态化学导论课程节选