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Little Questions Wrap Up

Entry 1449, on 2012-10-15 at 20:23:11 (Rating 2, Science)

It's time to wrap up my discussion of simple questions with deep, complex, and meaningful answers. I will briefly cover the other little questions I listed over a month ago now. So far I have discussed these: Why is the Moon round? Why is the sky blue during the day? Why is the sky dark at night? and What is a star? These revealed some quite insightful facts about the universe we live in so let's get started with the rest.

The first question is "Why is grass green?" The question could extend to other plants as well because most leaves are also green.

Grass is green because grass is full of chlorophyll which is green. Chlorophyll is a chemical which allows the plant to capture light from the Sun and store that as energy. Green things are green because they absorb all the light which isn't green and reflect the green light which we see.

But the Sun generates a lot of energy in the green part of the spectrum so you might think that chlorophyll should be black because it would then absorb all the light that hits it and it would be able to create more energy for the plant. Why isn't it black?

Evolution does not always produce the best possible outcome. It works with what it has and all complex organisms were originally much simpler and almost certainly adapted to quite different conditions. In fact chloroplasts (the little organelles in a plant cell which contain chlorophyll) were originally completely independent bacteria which invaded the plant cell. The same thing happened with mitochondria, the energy production organelles in animals.

So the fact that grass is green tells us a lot about how evolution works. The way that plants and animals produce energy (using what were originally bacteria which they assimilated into their own metabolism) is also strong evidence supporting evolution (as if it really needed any more).

The next question is "What is a dream?" I'll give you my understanding of the current consensus on this. The brain works when the individual is asleep organising memories and performing numerous other tasks. Dreams are subconscious thoughts on issues which have made some impression on the person during the day: things which they might be concerned, happy, or worried about, things they were surprised about, etc.

Dreams are not premonitions of the future (at least they are nothing more than guesses), messages from the dead or living, or anything else ultimately mysterious. Sometimes people think a dream has given them some special insight and maybe it has, but these situations are the result of confirmation bias. People have many dreams and we would expect by chance that one might occasionally provide some unexplained information. People often remember the time when one dream was accurate but forget the 100 times that other dreams were wrong.

Attributing special abilities to dreams is sometimes an example of when the wrong conclusion is reached because of a failure to look at all the evidence - a far too common occurrence, I'm afraid!

Question three is "How deep can you dig a hole?" I'm not sure if I can extract a vast amount of unexpected insight from this but it's still interesting.

The Russians decided to dig the deepest hole they could in the 1970s. That hole reached a depth of 12,262 metres (40,230 ft) in 1989 and that is the deepest hole so far completed.

That's not actually very deep considering that the diameter of the Earth is around 12,800 kilometers. It represents 0.2% of the total depth theoretically possible (reaching the center of the Earth's core) but it is eight times deeper than the deepest natural "hole" - a cave system in France.

So how about this one: "When is the world's birthday?" The Earth took many years to form and there was no clear point where you could say that formation was complete, so this question cannot really be answered. There is a consensus on the age of the Earth though: 4.54 billion years, and this is known to an accuracy of about 1% which is quite an impressive achievement when you think about it.

Perhaps for an object which exists as long as a planet a better question would be when it was born in terms of orbits around its galaxy rather than days. That makes the Earth about 19 orbits old but I'm still not quite sure how I would specify the equivalent of its birthday.

Maybe the conclusion from this is that most humans think on such small time scales that even the questions they have don't always work within the longer timescales of the universe as a whole.

So here's another question: "Why do we have toes?" The idea that only the big toe is necessary for balance and the others are basically irrelevant is quite common but I have never found a definitive source confirming that. This one might get back to evolution again like the chlorophyll question above. Maybe we have toes because our distant ancestors did.

Our ancestors were arboreal and toes were useful for gripping tree branches. We don't use them for that any more but they are still there. That's the way evolution works.

Moving on we have "How much does the sky weigh?" I will assume by "sky" here we mean the atmosphere. It's actually not that difficult to calculate this number from a couple of other quite well known numbers.

If we know the pressure of the atmosphere on a particular area that tells us how much all the air above that area weighs. This number is about 14 pounds per square inch (sorry about the ancient units which are the only ones I can remember!) So for every square inch of Earth there is 14 pounds of air above it.

The Earth's diameter is 12,756 kilometers (through the equator, and 12,713 through the poles - more numbers I just remembered) so let's say 12,730 as an average. The formula for the total area is 4 times pi times the radius squared. Pi is 3.14159265358979323 (yes, another number I remember) and the radius of the Earth (in inches) is about 250 million. So the total area in square inches is 800 000 000 000 000 000 square inches.

Each square inch has 14 pounds of sky above it so the atmosphere weighs 10 000 000 000 000 000 000 (10 million trillion) pounds. And yes, I did use a calculator and checked my answer with some web sites. It seems to agree so we're either all right or all wrong!

Notice that I didn't need to know how deep the atmosphere is, or what it is made of, or how it changes density as its thickness increases to get this answer. However those who have been paying attention will realise this number is too high because it assumes the pressure is the same everywhere. The Earth isn't flat and mountain's heights are significant compared with the thickness of the atmosphere. However I will leave a better estimate for another day... maybe.

Let's get into something a bit more obscure: "What is time?" Well I know but I can't really tell you! It's one of the dimensions of space-time. It's something which prevents everything from happening at the same time (are both of those a bit circular?) Maybe it's something we perceive which doesn't really exist. Does the past exist? Why can we only move forward in time? How is time different from other dimensions like length or width? Why are there 3 space dimensions but only one time?

I know time has something to do with entropy too. That might explain why it only goes one way. But really, as you can probably tell, I can't describe time in any meaningful way and I'm fairly sure no one else can either without using a mathematical definition instead.

So how about something simpler: "Why is water wet?" Is it because it's a liquid? I don't think so because some liquids aren't wet. Dip your finger into some mercury and it doesn't get wet. It does depend a bit on what you mean by "wet", of course. I think wetness involves the liquid clinging to the thing which is wet - that's why I said mercury isn't wet - it just falls off.

So maybe water (and many other things) are wet because they are liquids which cling to things, sometimes because of the polarity of their molecules but not always. But the problem here is more defining the word (wet) rather than coming up with a good answer, and that is often the case.

And now the final question: "Why did God let my kitten die?" I interpret this as being a specific example of the old problem of evil, a classic and long-lasting puzzle in the philosophy of religion. Most religions claim their god is powerful and perceptive, or even omnipotent and omniscient. They also tend to claim he is good. If he is all three of these things why do bad things (like the death of kittens) happen?

If God knows the kitten will die (he's omniscient) and can do something about it (he's omnipotent) then surely he can't be good if he allows it to happen, can he?

There are a number of possible answers here. The first is that God doesn't exist. Clearly that is the explanation I would prefer because there is no evidence a god does exist and what is the point in presenting questions regarding his presumed attributes? It's crazy. It's like asking: what species is the Loch Ness monster, or which planet do UFOs come from, or what is the name of the fairy at the bottom of my garden.

There are other possibilities though. Maybe god isn't exactly like he's presented. Maybe there are things he doesn't know about, or things he can't help with, or maybe he just doesn't care. Maybe he isn't omnipotent, omniscient and good at all.

Needless to say, neither of those explanations are popular with religious people. They tend to offer this one instead: god is all three of those things but his actions (or lack of actions) work towards a greater purpose which we can't understand. It may not seem that what he does or doesn't do is good but that's just because we have insufficient understanding to see the big picture.

Naturally this sounds like a major cop-out. But if you think about it we would be naive to think we could understand the actions of an entity which created and controls the whole universe. The problem that arises from this idea is that it then becomes pointless to try to understand God in any way. We can't make up stories about him (like in the Bible) or worship him, or ask him for help, or pretend we know anything about him at all. He is beyond our understanding.

Again, I don't think this is really the answer believers have in mind, but it is the natural consequence of their initial contention about understanding. It's just too convenient to say we understand God when it suits us but can't when the real world doesn't fit into our preconceptions.

So yeah, that is a big question. For the average child it's probably easier just to make up some empty platitude like "god has taken your kitten to heaven with him". But if you have a particularly gifted child by all means use the question as a starting point to enter into a extensive philosophical dissertation. That's much more fun!

Comment 1 (3353) by Doug Mackie on 2012-10-19 at 21:26:00:

Having a good value for how much the sky weighs is important in terms of international measures to address climate change. The concentration of CO2 is easy to measure as is the atmospheric pressure. From these two you can quickly calculate the mass of carbon to bring about a given change in concentration.

Comment 2 (3354) by OJB on 2012-10-21 at 13:34:38:

Of course, often the most apparently useless and esoteric thing can have real use in science. That's why no one would reject any research for not being practical.

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