I know I’m missing something basic here but please have pity. I’m told that the same volume of cream weighs more than the same volume of milk. OK, so cream is denser (makes sense intuitively). Why then does cream rise to the top? (I searched the archives for related stuff but couldn’t make the leap to understanding this.) Since cream is more oily than milk, is it analogous to oil and water/vinegar? How does that one work?
D’oh… maybe the person who told you that is wrong ??? … maybe cream is less dense than milk, just like oil is less dense than water? … d’oh … maybe you should ask that person where (s)he got that information ???
I’m happy to accept any corrections and enlightment in the spirit of education. Thanks for putting it so politely.
Maybe you were thinking about “heavy” cream? 
Or “light” milk? 
Sorry for my sarcasm before, gigi. What I was trying to say was that you yourself saw logical holes in the claim that cream is denser. You yourself saw that the cream rises and appears to be less dense. Therefore, my suggestion was for you to go back to the source of that claim, and challenge it there.
Before posting, I did try to find something on the 'net that would show the specific gravities of each, but I could not find much. I did find one site which seemed to say that cream weighs about 500 grams per liter. Water is 1000 grams per liter, so 500 grams sounded way too light, so I may have read that chart wrong. Next time I go to the supermarket, I plan to pick up a carton of each (cream and milk) and see if the difference is noticable.
Thanks for responding again–I was a little sensitive about it as I was feeling a little dumb about the question. I got the info from a friend who worked at a dairy farm; I will have to evaluate his assumptions more rigorously in the future.
One possible source of the confusion is the fact that cream is more viscous than milk. Viscous substances seem like they ought to be denser, but espescially with oily liquids, this need not be the case.
Not to mention that a lot of what you get in ice cream is a mixture of nitrogen and oxigen that is inserted during the manufacturing process to enhance the product. This will affect/effect/impact the results of the experiment. I say, eat it before it mealts and stop playing with your food.
I think that’s exactly right–intuitively it feels like oil or cream “should be” denser.
: wanders off to find some Ben &Jerry’s…
Perfect link, JonF. And so we conclude that light cream is heavy, and heavy cream is light!
Man! There’s a webpage for everything!
Cream is more dense than milk. Calorically dense, that is. I suspect the original source of the rumor was saying something about how heavy cream floats, and may have used the word density or ‘rich’ without explaining (or perhaps even understanding) what he was talking about.