# is there a substance that you CAN'T see through? **URL:** \ **Category:** Factual Questions\ **Created:** [November 17, 2002, 8:57am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149 "2002-11-17T08:57:12Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![seven7r](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@seven7r](https://boards.straightdope.com/u/seven7r)\ **Post date:** [November 17, 2002, 8:57am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/1 "2002-11-17T08:57:12Z")
someone please let me know… ---
**Author:** ![Phlint](https://avatars.discourse-cdn.com/v4/letter/p/c89c15/32.png) [@Phlint](https://boards.straightdope.com/u/Phlint)\ **Post date:** [November 17, 2002, 9:01am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/2 "2002-11-17T09:01:29Z")
Personally, I’ve never been able to see through any of the walls in my house, does that count? ---
**Author:** ![seven7r](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@seven7r](https://boards.straightdope.com/u/seven7r)\ **Post date:** [November 17, 2002, 9:02am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/3 "2002-11-17T09:02:46Z")
lol nah, there are technologies on this earth that permit you seeing through the walls of your house… so nah, it doesn’t count. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [November 17, 2002, 9:28am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/4 "2002-11-17T09:28:20Z")
You have to be more specific. Are you asking for a wall that blocks 100% of all known waves and particles? If you count neutrinos, I don’t think even a neutron star will block an appreciable fraction of that. The event horizon of a black hole is the only thing that blocks 100% of everything. ---
**Author:** ![antechinus](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@antechinus](https://boards.straightdope.com/u/antechinus)\ **Post date:** [November 17, 2002, 10:18am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/5 "2002-11-17T10:18:34Z")
The definition of ‘seeing’ is usually agreed to be observation with your eyes - a result of photons impinging on your retina. I must agree with Phlint, I cannot see through my walls either. ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [November 17, 2002, 3:29pm UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/6 "2002-11-17T15:29:33Z")
I can see through my walls. I have had devices installed called “windows”. ---
**Author:** ![airdisc](https://avatars.discourse-cdn.com/v4/letter/a/e19adc/32.png) [@airdisc](https://boards.straightdope.com/u/airdisc)\ **Post date:** [November 17, 2002, 4:10pm UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/7 "2002-11-17T16:10:37Z")
I could see through my walls after applying a force to them, such as a few sticks of dynamite, though only after the smoke cleared. Personally, I’d rather not see through them, and if I did, I’d simply go outside. ---
**Author:** ![hawthorne](https://avatars.discourse-cdn.com/v4/letter/h/c89c15/32.png) [@hawthorne](https://boards.straightdope.com/u/hawthorne)\ **Post date:** [November 17, 2002, 4:46pm UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/8 "2002-11-17T16:46:16Z")
It’s possible that **seven7r** (welcome to the boards, by the way) was posting this in response to [How come you can see through glass?](http://www.straightdope.com/classics/a1_120.html) which was featured on the front page in the last week or so. > [@](#): > > _Cecil_ > the reason you can see through glass basically is that there is no reason for you not to be able to see through it. For expanded definitions of “see”, try thick lead sheets. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [November 17, 2002, 4:52pm UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/9 "2002-11-17T16:52:50Z")
seven7r Do you have things to hide, and don’t want anyone spying on you or eavesdropping on your conversations, whether they are with other people or computers? Walls, insulation, and noise-generators will go a long way, but check out EMSEC: [http://www.tscm.com/TSCM101tempest.html](http://www.tscm.com/TSCM101tempest.html) ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [November 17, 2002, 8:17pm UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/10 "2002-11-17T20:17:28Z")
Forget walls…I’ve never even been able to see through my eyelids. ---
**Author:** ![Some\_Guy](https://avatars.discourse-cdn.com/v4/letter/s/439d5e/32.png) [@Some\_Guy](https://boards.straightdope.com/u/Some_Guy)\ **Post date:** [November 17, 2002, 8:59pm UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/11 "2002-11-17T20:59:56Z")
I see bright lights through my eyelids all the time. This is especially annoying when it’s a faraway lightning strike and I was dreaming. To answer the OP’s question, I doubt that any material is completely opaque to everything, though some things may well be very close, especially if they are sufficiently thick (and therefore more likely to absorb even high energy particles). Anybody got a planet-sized nucleon mass handy to test this? ---
**Author:** ![seven7r](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@seven7r](https://boards.straightdope.com/u/seven7r)\ **Post date:** [November 17, 2002, 9:56pm UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/12 "2002-11-17T21:56:30Z")
thanks for the welcome. i knew i had to be more specific, but it was 5am and i was drowsy. i didn’t have the engergy to aborate. :-/ ok, i might as well tell you guys. i’m creating a character that has the configuration of what we perceive is an orb, when in actuality, it is a living thing. it can grow and reproduce itself within itself. what i was wondering was, what kinda material should i make the outer crust of the orb be so no technology on this earth is able to “see” through this material and discover that this orb is actually a living thing. (i know, i know, won’t the orb eventually become a black hole? yea, so are a bunch of other suns on this universe. :-P) so, please help me out guys. thanks in advance. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [November 17, 2002, 10:06pm UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/13 "2002-11-17T22:06:23Z")
Well, the thing is that the more penetrating the radiation that you use, the harder it is to use to detect since the detector has to stop the rays. I have read somewhere that a neutrino has a roughly 50-50 chance of passing through a light year thickness of lead, but for that very reason, it is very hard to detect. So nothing is impervious to all radiation, but lead does a pretty good job. Somehow this reminds me of the time I was in a Japanese restaurant and saw (and ate) some tiny fish that were totally transparent and virtually invisible–except for their eyes. If you think about it, you will see that it is logically impossible for the eyes to be transparent. ---
**Author:** ![Devil\_s\_Advocate](https://avatars.discourse-cdn.com/v4/letter/d/3d9bf3/32.png) [@Devil\_s\_Advocate](https://boards.straightdope.com/u/Devil_s_Advocate)\ **Post date:** [November 18, 2002, 12:05am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/14 "2002-11-18T00:05:19Z")
If the thing is surrounded with lead, I don’t think current human technology would allow us to see what’s going on inside without actually going in there. Or you could just create a ficitonal material, like Niven did in _Ringworld_. It could be impervious to neutrinos, too, if you wanted it to be. But that would be overkill, IMO. ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [November 18, 2002, 1:31am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/15 "2002-11-18T01:31:27Z")
Collasped admantium would serve, as would a thiotimoline crystalline matrix. ---
**Author:** ![antechinus](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@antechinus](https://boards.straightdope.com/u/antechinus)\ **Post date:** [November 18, 2002, 2:29am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/16 "2002-11-18T02:29:32Z")
> [@](#): > > \*Originally posted by DrFidelius \* > \*\*I can see through my walls. I have had devices installed called “windows”. \*\* Yes…very good. It was night when I posted. Anyway, after I installed windows my walls kept falling over.😃 ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [November 18, 2002, 4:33am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/17 "2002-11-18T04:33:02Z")
I think ultrasonic waves can penetrate a lead shield. I don’t know if you can get any spatial information, but I don’t see why not. Anyway, using any known material will just lead to complaints from readers who think they know how to get past it. I think you’ll have to say that with our current technology, we can’t even tell what it is made of. It worked well in **2001**. You don’t have to worry about neutrinos, since we don’t have the technology to use them for imaging. ---
**Author:** ![billy](https://avatars.discourse-cdn.com/v4/letter/b/ecd19e/32.png) [@billy](https://boards.straightdope.com/u/billy)\ **Post date:** [November 18, 2002, 5:57am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/18 "2002-11-18T05:57:29Z")
> [@](#): > > \*Originally posted by seven7r \* > \*\*lol nah, there are technologies on this earth that permit you seeing through the walls of your house… so nah, it doesn’t count. \*\* Cite for this??? I know the military was working on something that you could pass over the surface of a wall and it would indicate when you got to a heat source. Kind of like a large, but still handheld stud finder. I wouldn’t call it seeing though. ---
**Author:** ![ShadowWarrior](https://avatars.discourse-cdn.com/v4/letter/s/7993a0/32.png) [@ShadowWarrior](https://boards.straightdope.com/u/ShadowWarrior)\ **Post date:** [November 18, 2002, 11:39am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/19 "2002-11-18T11:39:14Z")
> [@](#): > > \*Originally posted by seven7r \* > \*\*i’m creating a character that has the configuration of what we perceive is an orb, when in actuality, it is a living thing. it can grow and reproduce itself within itself. what i was wondering was, what kinda material should i make the outer crust of the orb be so no technology on this earth is able to “see” through this material and discover that this orb is actually a living thing. (i know, i know, won’t the orb eventually become a black hole? yea, so are a bunch of other suns on this universe. :-P) so, please help me out guys. thanks in advance. \*\* presumably then this is for some sort of novel/film/rpg or something… anyway, if it’s a sci-fi based story, why not simply create a new material? You can have mine, I call it ShadowWarriorium… ---
**Author:** ![ShadowWarrior](https://avatars.discourse-cdn.com/v4/letter/s/7993a0/32.png) [@ShadowWarrior](https://boards.straightdope.com/u/ShadowWarrior)\ **Post date:** [November 18, 2002, 11:40am UTC](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149/20 "2002-11-18T11:40:15Z")
Oh damn, I missed devil’s advaocate’s post… sorry… that’ll teach me to skim read… [Next page](https://boards.straightdope.com/t/is-there-a-substance-that-you-cant-see-through/137149.md?page=2)