When Superman uses his heat vision, do people nearby actually see ruby-red laser-like rays shoot out from his eyes? Or are the red lines just there as a convention for the reader (or viewer) to indicate what’s happening?
This burning question (pun!) came up last night when a few of us UK Dopers were enthusiastically supporting the British brewing industry, and we couldn’t arrive at an answer.
Short answer: He shoots rays out of his eyes that people can see.
Medium answer: Well, at least he did that through the bulk of his history. There’ve been periods where there were no red lines at all.
Complete answer (which is probably more than you wanted to know):
Pre-Crisis (IE before they rebooted Superman in 1985-ish and revamped his origins and powers) people saw the red laser-beams coming out of his eyes. There were a number of stories where people commented on the beams. One notable story had him and the Parasite dueling with heat vision and people commenting on it—if they hadn’t been able to see the heat-beams, Jimmy Olsen woulda said something like “Why are they flying around, giving each other squinty stares?”
After 1985, and for a while after that (5-7 years, maybe), Superman’s powers all became psychic and his “heat vision” was actually pyrokinesis and while his eyes glowed when he used his pyrokinesis for reasons never clearly explained there were no rays at all. He’d stare at something, his eyes would glow red and the thing on the other end would melt/burn. This (IMO) was not an effective storytelling technique–or an effetive dramatic technique either.
Sometime in the last ten years or so, the whole “Superman as Uri Geller” thing has been mostly abandoned (except for the occasional lapse) and he’s back to shooting visible laser-beams out of his eyes (with exceptions where he doesn’t).
Does that help? 
Fenris
Oops–one other thing before someone jumps me on it!
Yes, there was one story (by Alan Moore maybe?) where Jimmy (or someone) says “Great Scott! He’s so mad that he’s using his heat vision at so high a level that *I can actually SEE the beams!”
This left olde-tyme fans scratching their heads saying–“Um…but you’ve seen the beams before. You see 'em every time he uses 'em! That’s like saying “My GOD Superman! You have a yellow “S” on your chest!””
I wish I could remember which story that was…
Wow, Fenris, what a super answer. Very helpful and informative.
If I can have some supplementary qs… these also came up in the pub.
Has it been established that Superman has to eat to live? If an enemy could find a way to confine Supes, could Supes be starved to death?
If the answer is that yes, he must eat to live, then can we also safely assume he has to use the bathroom for both normal functions? I think it highly unlikely, but has this issue ever been referred to at all in any canonical literature? (As opposed to people trying to extract some humour from the situation).
Once again assuming that he has to eat… is there anything he can’t eat other than kryptonite (before it was disinvented)? Or is he effectively the same as Matter Eater Lad and can shove anything down? If he can’t eat just anything, this would seem at odds with his well-touted invulnerability.
If he drinks alcohol, does he get drunk like the rest of us?
Pre-Crisis, as long as he’s under a yellow sun, he doesn’t need to eat to live. He also doesn’t need to sleep/rest either, but he DOES need to dream. Post-Crisis, who knows–I suspect he needs to eat/sleep, but I don’t think it’s been addressed.
I’d assume that Post-Crisis he goes to the bathroom–Pre-Crisis, I could make a pretty strong case that IF he eats, he’d have a “super-digestive system” such that there would be no waste.
Also, someone will come along and refer you to the short article “Man of Steel, Woman of Kleenex” by Larry Niven any minute now. BUt it ain’t cannon. 
There’s some substance that even Matter-Eater Lad can’t eat–it showed up in one issue of ADVENTURE COMICS. I’d assume Superman Pre or Post Crisis couldn’t eat it. He also couldn’t eat anything that came from Krypton as it’d be “super” too. In other words, if a table from Krypton miraculously survived the explosion and wasn’t turned into Kryptonite, Superman wouldn’t be able to eat it any more than you could eat an earth-table.
Nope–his system wouldn’t even notice, Pre-Crisis. Post-Crisis…um…maybe, but probably not–if alcohol can affect him then poison can affect him. However, there was a really bad “Drinking and Driving is WRONG!” story Post-Crisis (with all the subtlty of a sledgehammer in the face) and IIRC, Young Clark had started to get his super-powers but was still able to get toasted. (I could be completely wrong–I hated the story and could be misremembering).
There was one post-Crisis issue where he had visible heat vision beams, but it was because Luthor had some invisible robot thingy broadcasting on various frequencies trying to overload various of Superman’s powers.
You are correct about the drinking and driving story.
Ok here’s a question. How does his “X-Ray” vision work? Because an X-Ray works by sending X-Rays through an object and a special film or camera picks up the X-Rays shining through. Is he both the source and receiver of x-rays or is it more like a thermal imaging thing?
Regarding his X-ray vision:
There was a pre-Crisis Superman comic I picked up once where Lex Luthor shot him with some sort of push-Superman-around ball of energy. As Supes was being shoved out into Earth orbit, he discovered that the only way to defeat this energy ball was to shoot it with heat vision out of one eye and X-ray vision out of the other eye.
The implication, clearly (if you’ll pardon the pun), was that Superman’s X-ray vision does indeed involve X-rays shooting out of his eyes.
Regarding whether or not Superman has to eat:
Let us not forget the following immortal words from the 1978 Superman movie:
LOIS: “Do you … eat?”
SUPERMAN: “Uh, yes, yes I do. When I’m hungry.”
It seems to me there’s two questions here: Can he eat a thing, and can he derive nourishment from it? Remember, there are an awful lot of things humans can eat, too: Remember the episode of MAS*H where Klinger ate a Jeep (very slowly, a piece at a time)? No reason to suppose Supes couldn’t do that, too. But I don’t think it would provide him any greater benefit than it did for Klinger. By contrast, Matter-Eater Lad can, as I understand it, not only eat anything, but derive nourishment from it as well.
Also according to the movie, the eye beams are not only visible, but emit a high-pitched humming sound. I’d be interested to hear an explanation for THAT!
My impression was that the heat was generated pyrokinetically at/in his eyes aimed in the direction his pupils were pointing. So there were still rays, just not in the visible spectrum. It’s been years so I may just be remembering my rationalization.
I think the issue now is left up to individual artists.
It’s definitely like a laser, but like a real laser it’s not visible midstream, only the effect on the target and a glow at the source. But, sometimes they draw them anyway, depending in what’s more dramatic at the time.
I’ve heard both ways on whether or not X-ray vision actually involves projecting X-Rays. Originally, Heat Vision was just X-Ray vision turned up high enough to roast things (they were eventually separated). However, in Kingdom Come, Green Arrow complained that “he probably made me sterile”, and Blue Beetle tried to explain that he didn’t project X-Rays.
I think authors are now uncomfortable that Superman routinely bathes everything in damaging radiation, including friends and loved ones. 
My theory, he projects something, but it isn’t X-Rays, per se.
That’s now how I recall the scene. BB was trying to explain that the levels were not high enough to cause damage, not that they were not X-rays.
I want to disagree about the past (pre-Crisis, I’m talking the Real Superman, the one from the 50s). I don’t think the heat vision was visible, it was just a convention. Perhaps, in the exceptional case, when it was very intense, it was visible.
My counter-example: when Lois tries to trick Clark by cutting off a lock of his hair, he bounces his heat vision off a mirror to snip the hair just as Lois is cutting it. That has to mean that the heat vision wasn’t visible – otherwise, that wouldn’t have been a very effective way of covering!
X-ray vision, too, many artists showed little dotted lines… clearly not visible to the humans around him, just artistic convention.
Not only can superman get drunk, legend has it he’s a real jerk when he’s drunk.
ah… actually, real lasers ARE visible mid-beam, but only if there’s enough crap in the air to reflect the beam. So I concur with your statement, mostly…
To clarify: the beam isn’t visible, unless there’s something to reflect it. However, you’ll find that in the modern context there is usually enough particulate floating in the air that the beams are visible, even if only slightly.
Obviously the more power in the beam, the more visible it will be, conversely, the lower the level of atmospheric particulate, the dimmer the beam, regardless of power output. This is one reason most commercial laser shows rely so heavily on fog machines or mist production gear and whatnot.
I’ve worked with 20Watt Argon lasers that were visible in the shade on a bright, crisp winter’s day with low-levels of particulate (bear in mind you’d need a VERY powerful beam to be visible in bright sunlight) and I’ve worked with beams that were VERY close to invisible. One good example of the visible beam is the output from the two 100Watt Yag lasers in the eyes of the Merlion(!) on Sentosa Island, here in Singapore. The beams are visible for their entire length (at night) such is the density of the atmospheric soup here (the columnation in a Yag laser isn’t very good, so the beams are not so powerful at 100W as you might expect).
So, Superman’s eye beams might not be visible during the day, but given the level of pollution that almost certainly hangs over Metropolis on any given day, and given that Supes can melt dense, tempered steel in mere moments (ref to the comics and the recent Warner Bros cartoons) he has to be pumping out a LOT of power in those beams, so it’s likely they would be visible. I’m guessing, on average he’s churning out something in the order of hundreds, if not thousands of Watts at any given time (this very rough guesstimation is based on observed experience , having seen a 20Watt Argon laser take about two minutes to burn through 2mm aluminium). However, this assumption only works if heat vision is similar to a helium-neon laser (red beams) which are visible at lower temperatures. Higher power lasers tend to be Green-blue(Argon), or invisible (Carbon dioxide), which adds more credo to your assertion that the beams should not be visible.
And yes, the more powerful the beam (on a visible laser), the hotter it gets and the more it moves into the visible spectrum (exhibit A: my right hand which got burneded many times while adjusting mirrors youch!).
Just to add a bit of semblance to this, light from the sun isn’t visible mid-beam either, only at the source and when it strikes something…
Somebody with more recent laser experience will be able to clarify some of this methinks, it’s been a while since I worked in the field.
I really ought to be working y’know…