# Is big bang light still travelling? **URL:** \ **Category:** Factual Questions\ **Created:** [February 15, 2013, 2:54am UTC](https://boards.straightdope.com/t/is-big-bang-light-still-travelling/650359 "2013-02-15T02:54:25Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![virtually\_yours](https://avatars.discourse-cdn.com/v4/letter/v/a587f6/32.png) [@virtually\_yours](https://boards.straightdope.com/u/virtually_yours)\ **Post date:** [February 15, 2013, 2:54am UTC](https://boards.straightdope.com/t/is-big-bang-light-still-travelling/650359/1 "2013-02-15T02:54:25Z")
Hi, is the _big bang_ light still traveling? If one could get to the outskirts and look back would they see the big bang? vy VY ---
**Author:** ![Bob\_X](https://avatars.discourse-cdn.com/v4/letter/b/4491bb/32.png) [@Bob\_X](https://boards.straightdope.com/u/Bob_X)\ **Post date:** [February 15, 2013, 3:03am UTC](https://boards.straightdope.com/t/is-big-bang-light-still-travelling/650359/2 "2013-02-15T03:03:03Z")
There aren’t any “outskirts”: every part of the universe is just as much in the “center” from its perspective and “way out on the outskirts” from somebody else’s. Yes, the photons from the Big Bang are still bouncing around, red-shifted by now down to the “microwave background” radiation, see [here](http://blogs.redding.com/dcraig/archives/2012/02/the-mind-of-god-1.html) for a nice discussion with some false-color pictures of the somewhat variable intensity from different directions (why it is not uniform in all directions is a major controversy). ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [February 15, 2013, 3:11am UTC](https://boards.straightdope.com/t/is-big-bang-light-still-travelling/650359/3 "2013-02-15T03:11:59Z")
> [@Bob\_X](#): > > There aren’t any “outskirts”: every part of the universe is just as much in the “center” from its perspective and “way out on the outskirts” from somebody else’s. Yes, the photons from the Big Bang are still bouncing around, red-shifted by now down to the “microwave background” radiation, see [here](http://blogs.redding.com/dcraig/archives/2012/02/the-mind-of-god-1.html) for a nice discussion with some false-color pictures of the somewhat variable intensity from different directions (why it is not uniform in all directions is a major controversy). Though just to add the CMB (cosmic microwave background) is actually from the “surface of last scattering”, when the Universe’s density dropped to a point where it ceased to be opaque to radiation circa 380,000 yrs after the big bang. ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [February 15, 2013, 3:29am UTC](https://boards.straightdope.com/t/is-big-bang-light-still-travelling/650359/4 "2013-02-15T03:29:56Z")
So to answer the OP: the early Universe was too dense for their to be any light orginating near (that is near in time) the big bang around these days. Light emitted in the first 380,000 years of the Universe’s history would almost instantly be re-absorbed. An interesting fact is that in big bang cosmology whether the whole Universe is casually connected, that is whether in theory light originating at one point in space at any earlier time could’ve traveled to any other point in space by the present time, depends heavily on the expansion of the Universe. I find this interesting as this is despite the fact that all distances go to zero as cosmological time goes to zero (i.e. the big bang). ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [February 15, 2013, 11:32am UTC](https://boards.straightdope.com/t/is-big-bang-light-still-travelling/650359/5 "2013-02-15T11:32:18Z")
> [@Asympotically\_fat](#): > > So to answer the OP: the early Universe was too dense for their to be any light orginating near (that is near in time) the big bang around these days. Light emitted in the first 380,000 years of the Universe’s history would almost instantly be re-absorbed. > > An interesting fact is that in big bang cosmology whether the whole Universe is casually connected, that is whether in theory light originating at one point in space at any earlier time could’ve traveled to any other point in space by the present time, depends heavily on the expansion of the Universe. I find this interesting as this is despite the fact that all distances go to zero as cosmological time goes to zero (i.e. the big bang). This. By the way, can I guess that you typed “universe is causally connected” and a spell checker tried to improve it for you? ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [February 15, 2013, 1:08pm UTC](https://boards.straightdope.com/t/is-big-bang-light-still-travelling/650359/6 "2013-02-15T13:08:13Z")
> [@Napier](#): > > This. > > By the way, can I guess that you typed “universe is causally connected” and a spell checker tried to improve it for you? What’s funny is that my eyes saw “casually”, but I took a second look and the post-processing in my brain turned it automatically into “causally”. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 15, 2013, 2:42pm UTC](https://boards.straightdope.com/t/is-big-bang-light-still-travelling/650359/7 "2013-02-15T14:42:02Z")
It didn’t even take a second look for me; I just saw “causally”. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [February 15, 2013, 3:27pm UTC](https://boards.straightdope.com/t/is-big-bang-light-still-travelling/650359/8 "2013-02-15T15:27:53Z")
Me too. Fascinating issue for interface design. ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [February 15, 2013, 5:19pm UTC](https://boards.straightdope.com/t/is-big-bang-light-still-travelling/650359/9 "2013-02-15T17:19:39Z")
> [@Napier](#): > > This. > > By the way, can I guess that you typed “universe is causally connected” and a spell checker tried to improve it for you? Good catch. It may’ve been spellchecker, though equally it may’ve been a straightforward typo as I would not have spotted it anyway. ---
**Author:** ![Washoe](https://avatars.discourse-cdn.com/v4/letter/w/ecae2f/32.png) [@Washoe](https://boards.straightdope.com/u/Washoe)\ **Post date:** [February 15, 2013, 5:36pm UTC](https://boards.straightdope.com/t/is-big-bang-light-still-travelling/650359/10 "2013-02-15T17:36:45Z")
It’s been my experience that when uneducated/unintelligent adults are reading aloud they invariably stop at the word ‘causal,’ puzzle over it for a split second, and then say ‘casual,’ even if the transposition makes the sentence nonsensical. What’s interesting is that the exact opposite occurred here. Because the sentence structure only permitted the word ‘causal,’ that’s what we saw.