During the great blackout of 2003 I spoke with quite a few people in Toronto who were amazed at the number of stars in the sky and did not know what the Milky Way was.
There’s a simple way to calculate this.
Let’s say a star’s average lifespan is 10 billion years (that’s the Sun’s lifespan)
Most of the stars you can see at night are within 1000 light years of Earth.
(We’ll assume for the sake of calculation that they’re all at 1000 light years- that gives us an upper bound on the number of stars that could have gone out since the light left them)
The answer is roughly 1000 divided by 10 billion: 10[sup]3[/sup]/10[sup]10[/sup] = 10[sup]-7[/sup].
Using those assumptions, one in 10 million visible stars would have gone out between the time the light left it.
There are about 2000 stars visible in the night sky in a good site on Earth- more in a really dark site, fewer in a city, and this depends somewhat on your vision and certainly on weather conditions. We’ll assume you can see 1000 stars in the night sky, just to make the math easier (What’s a factor of two among friends? 
)
If you can see 1000 stars, and one star in 10[sup]7[/sup] has gone out and you still see it, the chances are 1 in 10,000 that you’re seeing one star that has gone out since its light left it.
The actual chances of seeing a star that has since gone out is lower, because not all the stars are at 1000 light years, but this gives you a quick and dirty calculation.
The Milky Way, and, also, the Magellanic Clouds (visible from the Southern Hemisphere), does look like a cloud until you realize what you’re looking at.
Almost certainly urban legend. L.A.‘s a huge city, and the recent earthquakes (Sylmar, Whittier, Northridge) haven’t been large enough to knock out power everywhere. There’s also lots of car headlights, which contribute to night pollution. Plus, the wilderness isn’t that far away – it’s only a few hours’ drive to the mountains and/or desert, where the night sky is crystal clear. Most of us manage to make it out there at least once during our lifetime.
Perhaps you were thinking of San Francisco?
Nitpick: 10[sup]97[/sup]is one thousandth of a googol. Not “nearly a googol” by any reasonable definition of “nearly”.
Nit-nit pick 3 orders of magnatude is fairly ‘near’ when talking theoretical astro-physics
If you prefer, it’s 30,000 googol seconds. The point is, this is one of those few instances in physics where a googol is actually attainable.
Not much, but apparently three orders of magnitude isn’t reasonable.
Ironically, I was in Tokyo and missed the blackout. And, when I took a trip to Mount Fuji for the express purpose of seeing stars for a change (on the rare occasion that business takes me elsewhere than Toronto and Tokyo, it’s San Francisco, New York, London, Paris… notice a trend about visibility of stars?), every night was overcast with nary a star in sight.
However: off to Algonquin next week!! 
[/hijack]
Chronos, when you say that “these days” most of the radiation from in-falling matter to a super-massive blackhole is radio waves, do you mean that at some time in the past it would have been visible light? I thought that the process threw off rather energetic X-rays from the get-go. Is that not correct?
I’ve been brought up in the middle of nowhere, and of course visited many places situated long away from urban lights. I’ve never been able to clearly perceive the Milky Way. At most, I thought “Hmm…maybe there’s something there…Must be that”. In any case, nothing close to “proeminent”. Something that I wouldn’t have noticed if I didn’t have known it existed and searched for it.
I just assumed that everybody was seeing the same, that is, almost nothing, and that the Milky Way was known merely because there had been people observing the skies with a lot of attention, who couldn’t miss this detail, despite it being so teneous.
Now, reading that the Milky Way is blatantly obvious to several posters, I’m wondering… how comes I seem unable to see it? Am I the only one being Milky-Way blind?
Does it appear to people as clearly as the first picture displayed on the wikipedia article linked to in this thread 
? I’ve never seen anything even very remotely as obvious as this.
At some time in the past, there would have been significant visible light from at least some black hole systems. We can still see some such objects which are very far away (and also very bright); we call them quasars. The x-ray emission from black hole accretion can be considered significant, but only in the sense that there’s not much else in the sky giving off x-rays to compete with them (by contrast, a lot of things give off visible light). I don’t have any numbers handy, but I’m almost certain that more energy is given off in the radio part of the spectrum than in x-rays.
Looking at the nearby galaxies which have really bright radio emission, in the X-ray, you’re looking at fluxes from the accretion disk in the range of 10[sup]14[/sup]-10[sup]18[/sup] W/Hz/sr. In contrast, the radio luminosity is of the order 10[sup]21[/sup]-10[sup]23[/sup] W/Hz/sr. So, yeah, most of the energy is given out in radio emission.
Except that’s not energy, that’s spectral density. You’d need to integrate that over frequency and solid angle to get a power output. And x-rays have a much wider range, in frequency, than radio waves (over 10[sup]19[/sup] Hz, as compared to less than 10[sup]12[/sup] Hz for radio). So it’s actually possible that the total power is greater in X-rays than in radio, which I find somewhat surprising.
Thank you, Polycarp, for the excellent post in response to the OP. That one saving.
On another board I frequent, a photographer took a time-lapse photo of the house (lit from the inside by a single votive candle) with the milky way behind it in the sky. Another poster essentially said “Huh, looks nice, but fake of course”. Then proceeded to assert:
• You can’t photograph the milky way because we’re inside it. To see it you’d have to get out beyond it and look back;
• [After backing away from that one] Look, here is another photo of the milky way and see, when I superimpose it on Joe Blow’s photo, they line up perfectly, and that proves it’s a fake. Because the stars don’t stand still wth respect to each other and there’s no way he just happened to take this photo at the same exact time as this professional astronomer did.
• Stars’ proper motion is such that they change position relative to each other all the time but after awhile cycle back to where they started from.
Obviously, some of that is a :smack: with regards to this person’s education rather than one with regards to ignorance of the night sky that one can actually view, but there’s plenty of :smack: to go around.
The one thing I don’t get is why planetariums in metropolitan areas don’t bother to show you the actual freaking night sky. Instead they’re showing you stupid movies about how stars are born or what space travel will be like. Damn, I’ve seen science fiction movies and so has everyone else in NYC. Show us what folks in rural Nebraska or the high mountain country of Colorado see on a clear moonless night!
This is very true, but I’m fairly sure that the spectrum of a active galactic nucleus is flat in the radio and follows a powerlaw in the X-ray. So, I think that you could still get more output in the radio than the X-ray.