John Salerno

I think I get it now. The principle is basically an "upper limit" rule for an animal insofar as it actually remains that animal as it grows larger, rather than becoming so altered that it's no longer reasonable to call it a spider, or elephant, or whatever, anymore. And I suppose the main point is that this change can't happen in a small amount of time, hence the original point of saying spiders (as we know them) cannot get much larger than the largest that we've observed?

That makes sense. So maybe a more fundamental question is simply, when does the square cube principle come into play? Is it strictly for artificially enhancing size? Or does it have implications even in the natural course of evolution? To put it as naively as possible (yes, I see how dumb this question is before I even ask it), why can we have elephants as big as they are then? Why is their muscle tissue not so densely packed to accommodate their size that it becomes a problem for them? They obviously grew large from a relatively small size, so during that growing, how did the muscle growth keep up? And why can't the same happen to a mouse?

I think I'm starting to understand it better now. When I was lying in bed last night in the dark I started thinking of it this way: I can't see the color of anything in my room because there is no light present to reflect off the objects. However, if I had my TV on, I would see colors despite the absence of other light, because the TV itself is producing specified colors. So when I see red on TV, it's because the actual color red is being shown in the TV, rather than absorbing outside light (which isn't present anyway) and reflecting red. Does that make sense? This is sort of what led me to even ask the question in the first place, and I still don't quite understand this. If I can't see the yellow shirt in the dark, wouldn't that suggest that it's only subtractive color? Or are you saying that perhaps the shirt was made to reflect red and green, which is still a subtractive process, but then my eye uses the additive color process to combine them to yellow? At the most fundamental level, I suppose I'm sort of asking, how is the shirt made? What goes on in the factory to make it? Is it made with dyes that reflect yellow? Or that reflect red and green? Is it at this point (the making) that determines whether I'm seeing a subtractive or additive color later when I buy the shirt? Or does the type of color I'm seeing (subtractive or additive) change based on the conditions in which I'm viewing the shirt?

But I guess another way of asking my question is, even if we were to artificially scale up the size of a spider, couldn't we just artificially scale up everything else so that it doesn't succumb to the square cube principle? Or is the very nature of the exoskeleton what makes them an exception? What about other animals, like the mouse you mentioned. Couldn't we artificially make it a giant mouse by also increasing its muscles and mass in the proper proportion? Basically, my confusion comes from the statement I quoted originally. That statement seems to assume that even if you artificially increase the size of something, the other aspects of that organism (muscle, mass, etc.) increase in fixed ratios and cannot themselves be artificially altered as well to accommodate for the new size. That doesn't sound right. If we're already playing mad scientist with the size, why not adjust *everything* to the proper ratios so that the organism is viable?

I've been reading these two pages on Wikipedia and my head feels like it's spinning. I understand the whole concept of light being absorbed/reflected to create color (subtractive). And I understand what additive color is, but I don't understand how these two interact, or how to tell which is the one producing any given color you might see. For example, if I have a red shirt, how was it created? Is it absorbing all light except red, thus it looks red to me? Or was it created by *combining* colors to make red? (Although in that case, it would just be the single color red. But say the shirt is yellow. Is it absorbing all light except yellow? Or was the shirt made by combining red and green colors?) The example given for additive color was a computer monitor. There are three pixels close together (RGB) which turn on and off to create colors. But is subtractive color not playing any part in this? Why do those colors even *look* red, green, and blue in the first place if not for absorption/reflection of light? Or is this maybe the crucial difference between the two? Hmm, I just had another thought. Would it be correct to say that additive color requires its own light source to make? Such as the computer monitor, or projectors, or theater lights? So in other words, additive color is not possible except for things that are backlit or light-producing on their own? And that subtractive color requires normal light only (i.e. I wouldn't be able to see the red or yellow shirt without the light on, so it can't be additive color)?

I'm curious about this "square cube law" and how it limits body size. I read this on the Wikipedia page: "If an animal were scaled up by a considerable amount, its muscular strength would be severely reduced since the cross section of its muscles would increase by the square of the scaling factor while their mass would increase by the cube of the scaling factor." I'm not going to pretend that I understand everything that sentence is saying, but let me try first: If an animal increases in size, its mass would increase more than its muscles, so it wouldn't be able to support its new mass? If that's correct, I'm just wondering, couldn't it come about that a species evolves to a larger size over time so that it *could* support itself? Take the spider for example. The above quote seems to prevent the artificial scaling of a spider to a large size, I get that, but does it also mean a spider could *never* get large even through the course of normal evolution?

Thanks for the resources!

Thanks again!

I just want to be clear on something: during a new moon, is it the case that you can't see the moon at night simply because the Earth-facing side is not being illuminated (but the moon is still physically there in front of you), or is it the case (which I think you are saying) that the moon is on the other side of the Earth and is physically absent from the viewable portion of the sky?

It may be a "US problem" but that doesn't diminish the fact that these people have an influence on what US citizens believe, and as far as I'm concerned, that's still important. I'm not going to take the attitude of "Don't worry about some of the dumb people in the US, the rest of the world has it under control."

Yes, people like that are who I had in mind, not just anecdotal accounts from people on the street. And granted, I don't put much trust in anything someone like Glenn Beck says, but the fact is he is one of them promoting the idea that GW may not even be happening at all.

Well, like I said, my knowledge in this area isn't very thorough, so perhaps I don't really know the right questions to ask. However, I do know that many people *do* deny the claims you make above, and it's mainly those people I was wondering about. From the content of your post, you are clearly one of the more sophisticated skeptics of AGW, but I suppose I had in mind the people who are denying AGW but can't give such an answer as yours. There are people who even deny the basic claim that the earth is warming (oh look, it was cold today in Boston) and it was these people that had me scratching my head wondering why they continued to deny the evidence.

Ah good, someone to ask directly then. Can you explain the specific reasons you don't accept AGW? What kind of scientific evidence do you reject? What reasons do you have to think it's purely natural? (I'm really asking, so let's try to keep the discussion civil.)

Hmm, some interesting points (and a very sad video to watch!). But I do think swansont has a point about downplaying the harm of GW. Is that really the best approach to take when what we really need to do is make people realize that it is a real and damaging occurrence? No need to use fear as a tool, but certainly we don't want to ignore the real fears that GW may cause.

I'm not really well versed in this topic, but one question that occurred to me is why so many people are opposed to the idea of humans causing or contributing to global warming. The closest scenario I can think of is people who deny evolution, but at least their reason is clear: religion. But what is it about global warming that causes people to deny humans' contribution? I can understand why corporations like oil companies would deny it, and their subsequent supporters in Congress maybe, but why do normal, everyday people deny it? It doesn't seem to present an immediate conflict with some other belief system, as evolution does with religion. Thanks.

Thanks guys. Last night I also thought of maybe a simpler way to ask the question. Since many humans are color-blind in the same way as dogs and other mammals, I wonder what the answer would be if a color-blind person described what he/she saw when looking at an object which appears red to others. This seems like an easier way to get an idea than to ask a dog.

I'm reading a book that discusses how most mammals other than primates are dichromatic, which to some extent I already knew given the common assumption that dogs, for example, are "color blind." I understand that they aren't fully color blind, of course, but that they can see basically from blue to green in the visible spectrum (visible by humans, at least!). But it got me wondering, do we have any idea what a dog (or any other dichromatic animal) sees when presented with an object that is, for example, orange or red? Does it appear black and white to them? If so, what's happening in the eye to cause this appearance? Or does it appear as some other color that they *can* see? Thanks.

Hmm, how do you like that! All this time I just assumed it was a progression from single-celled to multi-celled. Talk about a paradigm shift.

I recently finished reading Richard Dawkins' book "The Ancestor's Tale" and when I reached the end I noticed that the family tree lists (multicellular) plants and fungi as preceding some single-celled organisms such as choanoflagellates and DRIPs. I had always assumed (perhaps naively) that single-celled organisms came first, then multi-celled organisms evolved from them at one point, and that was that. (I understand that single-celled organisms still exist and did not die out when multicellularity appeared on the scene). But unless I'm understanding the book incorrectly, it seems like certain multicellular organisms (e.g. plants and fungi) branched off from unicellular organisms early, and unicellular organisms persisted, and then branched again into other multicellular organisms, such as what eventually became animals. Is that correct?

Fascinating stuff! Thanks! That explains why the moon was nowhere to be seen last night (on a clear night). According to the calendar, it's a new moon right now. I need to head outside in about 30 minutes and go look for it! (It's 11:30am right now.)

Well yeah, but since it is nighttime, I figured they would have some sort of moon. But you're saying when the moon is new, then anyone on the "dark" side of the Earth can't see the moon at all? Ah, that makes sense! So I suppose I misunderstood what those times represented. Thanks!

Well, that's good to hear since that's exactly what I'd expect. As it turns out, I was wrong about one of those sources: one image (the image on the Wikipedia page for lunar phases) shows that the *new* moon is best viewed at noon -- although this still leads me to wonder how people on the other side of the Earth would be able to see a moon then. If the moon is in between the Earth and the sun, does that mean people on the far side of the Earth don't have a moon at all? As for the full moon at noon, I can't find the site I was looking at last night which allowed me to enter my specific time zone (US CST), but this site is basically the same: http://www.lunarrepu...fo/phases.shtml It lists 17:05 on August 24 as the time of the full moon, which for my time zone would be 12:05pm. Does this mean something other than what I think, or does it mean that by the evening of the 24th the moon will already be waning? Thanks. Edit: Actually that link above is the same site as the one I saw last night. This link is the one I used for my time zone: http://www.timeanddate.com/calendar/moonphases.html?year=2010&n=104

First off, hi everyone! This is my first post because I just found these forums (by Googling "science forums" in hopes of finding a good forum to ask science questions!). Anyway, lately I've been really interested in the moon and I've been reading about the lunar phases. (I assume this is the appropriate sub-forum? Or perhaps it should be moved to "Other Sciences"?) My question involves something I've noticed on a couple of different websites that list the optimal time to view particular phases of the moon. In at least two different sources I've seen that the full moon is best viewed around noon local time. But I don't understand how this is possible if, in order for a moon to be full, it must be on the other side of the Earth from the sun, and in order for someone to see the moon in this specific location, they would have to be on the far side of the Earth (i.e. the dark side) as well? So wouldn't it only be visible at night? I've certainly noticed the moon up in the sky during the day, so maybe this is the same type of case. I just didn't understand how it would be possible to see a full moon during the day since it seems like you'd have to be on the side of the Earth not facing the sun. Thanks! John