查看“︁粒子视界”︁的源代码

{{NoteTA|G1=物理學}}
'''粒子视界'''（{{lang-en|particle horizon}}）指[[粒子]]发出的光在[[宇宙的年龄|宇宙寿命]]内能行进、被观察者观测到的最远距离。和其他[[视界]]的概念类似，粒子视界范围以内可被人类观测到，其外则不可被观测到<ref name="books.google.com">{{cite book|author=Edward Robert Harrison|title=Cosmology: the science of the universe|url=https://books.google.com/books?id=kNxeHD2cbLYC&pg=PA447|access-date=1 May 2011|year=2000|publisher=[[Cambridge University Press]]|isbn=978-0-521-66148-5|pages=447–|archive-date=2016-08-26|archive-url=https://web.archive.org/web/20160826075123/https://books.google.com/books?id=kNxeHD2cbLYC&pg=PA447}}</ref>，因此当前的粒子视界的大小即是[[可观测宇宙]]的大小。<ref>{{cite book|author1=Andrew R. Liddle|author2=David Hilary Lyth|title=Cosmological inflation and large-scale structure|url=https://books.google.com/books?id=XmWauPZSovMC&pg=PA24|access-date=1 May 2011|date=13 April 2000|publisher=Cambridge University Press|isbn=978-0-521-57598-0|pages=24–|archive-date=2013-12-31|archive-url=https://web.archive.org/web/20131231164745/http://books.google.com/books?id=XmWauPZSovMC&pg=PA24}}</ref>

== 计算 ==

{{Refimprove section|time=2021-05-29T07:12:14+00:00}}

粒子视界的大小不能简单用宇宙的年龄，而是要用被称为'''共形时间'''<ref>{{cite web |title=共形时间 conformal time |url=https://nadc.china-vo.org/astrodict/termdetails?id=21777 |website=国家科技资源共享服务平台 |accessdate=2021-05-29 |archive-date=2021-06-02 |archive-url=https://web.archive.org/web/20210602212420/https://nadc.china-vo.org/astrodict/termdetails?id=21777 }}</ref>（{{lang|en|conformal time}}）乘以[[光速]] <math>c</math> 来计算。其公式为<ref name="Giovannini">{{cite book|author=Massimo Giovannini|title=A primer on the physics of the cosmic microwave background|url=https://archive.org/details/primeronphysicso0000giov|registration=yes|access-date=2011-05-01|year=2008|publisher=[[World Scientific]]|isbn=978-981-279-142-9|pages=[https://archive.org/details/primeronphysicso0000giov/page/70 70]–}}</ref>

:<math>\eta = \int_{0}^{t} \frac{dt'}{a(t')},</math>

其中<math>a(t)</math>为[[弗里德曼-勒梅特-罗伯逊-沃尔克度规]]的[[宇宙標度因子|標度因子]]，<math>t=0</math> 为[[大爆炸]]发生的时间。传统上用下标的“0”表示当前时间，因此目前的共形时间为<math>\eta(t_0) = \eta_0 = 1.48 \times 10^{18}\text{ s}</math>，再乘以光速 <math>c</math> 即可求得当前（即<math>t = t_0</math>时）粒子视界的大小是：
:<math> H_p(t_0) = c\eta_0 = 14.4\text{ Gpc} = 4.69 \times 10^{10} \text{光 年 }</math>

== 参见 ==
* [[宇宙学视界]]

== 参考资料 ==
{{reflist}}

[[Cat:物理宇宙学]]