That is interesting and pretty much supports the "we don't know a lot" idea. Not something easily studied.

Mostly iron because Iron packs really well under extreme pressure and temperature, which is really what drives the segregation of materials inside a planet. It is a matter of space/volume and not all compounds pack to the same extent so unit volumes vary, and will change even for a given compound as P and T vary. The amassing of iron in cores is just a response to the existence of pressure and temperature change with depth (other elements or compounds are less compatible with high pressure, basically, so they end up closer to surface than things that deal well with high P and T, and iron deals the best of them all, apparently.

On top of that density consideration are the chemical needs of each element. Most elements are not all that stable except when in a compound, but iron actually is fairly stable chemically, as a native element. Plus, there is a lots of iron around, with iron being the most stable element made by stars (heavier elements want to break apart, undergo fission, and lighter ones want to combine and make bigger atoms, undergo fusion).

The physical characteristics of iron at extreme pressure and temperature are not well known because it is really hard to study something several thousands of kilometers below a mass of silicate materials (study in place) and it is difficult to make even in laboratory, and then only in very tiny amounts, with even a problem of time duration coming into play (it won't stay the same if you ease off pressure or temp).

People are working on it. More near the frontier of knowledge than a well-characterized material. Even the nature (PT-conditions) of the transition from face-centered cubic to hexagonal close-packed structure is poorly defined from what I have seen about it.

Including minor nickel to make some sort of alloy, and its effects on behavior, is also still poorly understood.

The physical behavior you call "phase" is that of the group or bulk mass. You have the correct understanding that the individual atom has no definite state of matter, because the state of matter is not a characteristic of the individual. The same atom can be in differ phase or state because it depends on what everything else is doing and how the one atom interacts with its neighbors.

Often, the physical state (whether sold, liquid, gas) concerns compounds rather than single atoms, so not only is the single atom part of a particular compound, it is that that compound which displays a particular state of matter that depends on its conditions and what else is present and interacting with the compound.

Air is fairly diffuse, as in there aren't nearly as many atoms per unit volume as with a liquid, so the atom will stay suspended until it encounters another element or compound with which it can react chemically and has an interaction with that other element/compound of a long enough duration that the interaction can proceed. Smacking into an O2 molecule "might" result in the formation of PbO but not if the collision is too forceful, too weak, or not adequately direct. Eventually, over time, thermodynamics say that the metallic lead in air will undergo an oxidation-reduction reaction and make some sort of base salt such as lead carbonate or lead oxide. However, it does take some time for that to happen on a statistical basis (never goes to total completion, really).

Even then, though, the new compound will tend to stay suspended until it absorbs onto some larger solid or dissolves into some larger liquid mass (like droplets in a cloud). It will then go wherever that larger mass ends up going.

If air is still (no movement at all), there will be a slow downward migration because of density differences, but even the slightest air movement will be enough to keep the atoms or tinier particulates in suspension.

Mostly though, the atom will bounce around in the gas, as part of the gas phase, until it gets lucky and reacts with some other participant in the chaotic dance, making a new molecule.

Even metallic lead has a vapor pressure, the presence of some atoms that will leave the solid and enter the air just by random energy pulses, so the drive to "rain" out of the air just by density isn't all that powerful. That is, in a closed space, if you leave a bar of lead out on a tabletop, some of that lead will escape the solid and enter the air. Not a lot because lead isn't all that volatile, but you cannot prevent all loss at the interface (surface of contact between air and solid).

I don't know what the average residence time (median duration that the atom would exist in suspension before descending to the ground) of a lead atom in air would be. Not likely a value measured in seconds or minutes. Even household dust has mean residence times longer than that, and that stuff is destined to fall fairly rapidly by comparison to a lone atom, if only the air would stay still long enough.

I'm going to take a stab at this. Hope I don't get too complex even though the question is really several questions.

Glacial ice is mostly the result of past snowfall. Ice is what you get when you compact the snow and get rid of all the open space. It is pretty much the same idea as the conversion of mud into rock. The snow undergoes metamorphism in a away, it recrystallizes from pressure (weight) perhaps with some melting, flow of water down into open space, refreezing, as well.

As you know, we live on a seasonal planet. The result is that there is seasonality in precipitation and temperature. These variations cause ice to form distinct layers for each year, very much like how tree rings form and the thickness of the rings reflects what went on with the weather during that year. Some rings (some layers) can be fairly thick, and some are almost non-existent depending on what happened over the course of the year. Dry year, not much snow=thin layer.

Loose snow can be 80-90 percent air, or to put it another way, you get about 10 inches of snow for 1 inch of rain. The conversion is ballpark, not precise. I am sure you have heard something along those lines, and the point being made is that water, liquid water, has a density of about 1 (g per cubic centimeter) but snow has a density of about 0.1. Only 10 percent. When converted to ice, the ice will have a density slightly less than water (why ice floats in water).

So, you lose about 90 percent of the volume even if no melting or sublimation (evaporation but without passing through a liquid state, from solid to vapor directly). Apparently about half that density change from snow to ice happens in the first year. (makes stuff called firn, snow from previous winters that has not converted into solid ice) and the rest happens over several years or more.

That is how we go from snow to glacier. How much snow? Well, that really varies a lot. Some places will only see maybe a meter of snow per year, and other places maybe 10 meters or more, with most places having permanently winter conditions getting something in between.

Lots of places still see some above-freezing or near freezing temperatures so sunlight heats the snow to melting, during part of the year (like say on high mountains) so part of the snowpack gets lost by melting and evaporation/sublimation. So in many regions, the amount of original snowfall that makes it down into ice might only be a small percent of the original, perhaps 10-20 percent. So, if we started with a meter of snow per year, we might only get about 5 cm of ice. Still, even at that slow rate, you could get 5 meters in a century and 500 meters in 10,000 years.

So, how fast does it accumulate? You can get some pretty important changes to ice extent and thickness over the period of a millennium (1,000 years), even when there is not a lot of snowfall, but generally it will be slower even if there is a lot of snow (because of loss through evaporation/sublimation and melt runoff).

Many thousands of years is generally needed to make a good glacier and tens of thousands of years to make an ice sheet (massive glacier). Some ice sheets, like in Greenland, have been drilled and cores removed, going back 100,000 years, and even further back, several hundred thousand years, in the Antarctica ice sheet.

Africa has largely missed on continental glaciation because it is too close to the equator, or too far from the poles. Mountain glaciers and flow onto nearby lowlands is indicated, but no massive ice sheets. Same idea with Australia. South America had a pretty well-glaciated spine almost up to the equator (the Andes mountains are so high that glaciers could be formed even near the equator), but much of the continent did not get glacial cover.

Two reasons why the northern hemisphere got a lot more glacial cover than the southern hemisphere: 1) the Arctic is an ocean so lots of moisture can be transferred to nearby land, and 2) a lot more land in the northern hemisphere is near and in the polar regions than in the southern hemisphere.

The ice sheets in the northern hemisphere mostly never got further south than about 45 degrees N. Most of Australia, Africa, and SOuth America, is further north than 45 degrees south. Basically southern lands a lot further from the south pole than northern lands from the north pole. Apart from Antarctica, of course. Frozen pretty solid down there.

Yeah, well, there is the nub of the argument, and a good part of the reason why most scientists accept that humans are affecting climate but many disagree about the importance of the human role. It is also where a lot of uncertainty appears in predicting into the future.

The problem is that there is no "signature" we can measure directly and say "this 23 % is from humans (pick any number), and the other 77% is what nature does".

What we have are climate models. The climate models are an attempt to imitate the natural system behavior, and seeing how different changes to input conditions cause changes to output. The system is complicated, and so are the models.

There has been a lot of work on trying to figure out how much change has been "forced" by human activities versus how much can be explained by natural changes. They can compare models with, or without, changes to various important parameters over time as an input, and see how the results differ, and then interpret what is really important and what is not so important for what is actually happening. Fairly complicated work in actual practice.

It is from playing around with the various parameters that can affect climate, and finding mismatch between observation and the changes that ought to have happened if nature alone is the cause, that a lot of climate scientists have concluded that CO2 is the main problem.

Are they right? We are finding out. Not sure it is wise to perform this experiment in real time, but we are, even if not purposefully.

rate doesn't affect the fact that accumulation is happening, what matters is that addition exceeds removal over time. How long it would take to make a thick pile, though, that does matter on rate, or more particularly the size of the difference between addition and removal (high addition rates combined with high removal rates would still result in slow accumulation, same as if both were low). The Antarctic has been accumulating ice for maybe as much as 25 million years, or about there, and it probably wasn't such a desert for all that time.

The earth did not go from "Antarctica is a temperate forest and grassland" to "Antarctica is a frozen desert of ice" overnight.

The dating is not used to define the temperature or other chemistry. It is used to put the sample into a time context. Most dating using radioactive decay as a "stopwatch" has a window of time where it works, and only works if the radioactive element and its daughters get captured at the time the mineral, rock, or organic residual got made, and any changes after formation to concentration of those atom types in that sample is only because of decay).

The date we would get from measurement and calculation refers to the date that the measured component got created. Dating the age of a mineral derived from erosion of an igneous rock will yield the age of the igneous rock, not the age of the sediment, so sediments tend to be more difficult to date by radioactive means. Some minerals do form in the sediments at (about) the time of sediment deposition, and dating those minerals, when possible, will give a decent age for the sedimentation. Generally speaking, radioactive dating is used to put date limits on sequences (using some cross-cutting relationships with datable units like dikes or sills; younger than that 5 million year old rock but older than this 3.2 million year old rock). Ash layers from volcano eruptions are actually really good for that, because the ash layer is a distinct layer and a fixed time and covers a very large area, and the age of the ash is the age of the sediment it is in, so it can be a very good marker unit for a lot of different places in the area.

Some fossils are actually pretty good for dating, but short time windows tend to rely on microscopic fossils like foramnifera that are a lot of work to find and ID). Carbon dating (which only works on fairly young materials, like 60,000 years old or less, about) isn't actually dating the sediment either, but the age of the piece of wood or plant leaf or whatever is going to be the same (to the precision we can measure) as the sediments it got buried by and within.

Mostly, though, we either use other non-radioactive methods to date the sediment or material. Ice ores are dated sort of the same way as trees using tree rings. The rings (layers) get counted. It isn't always counting right from surface, sometimes the section or the sample is compared to other sequences already counted and matched to a window of time without counting all the way back until today in that one sampling program.

The point here is that dating is not the same analysis as the measurements used to define chemical conditions of atmosphere and oceans. There are lots of ways to measure temperature and chemistry, some of which are very direct (when you can get an actual, real sample of preserved atmosphere in some ice and analyze it) and some are indirect (using stable isotope equilibrium among different species to define the temperature of equilibration (=formation) assume the minerals formed from sea water did so in equilibrium with that sea water and thus with each other). Similar things respecting ocean chemistry is revealed by major and trace element contents of minerals formed from that sea water. So we can get a pretty decent idea, within certain windows or ranges (small error limits), about what ocean chemistry and temperature was at the time of the deposition of sediments in that ocean.

It isn't just one thing and "POOF" the conditions are known for a given time. It is a lot of work involving measurement from a lot of samples from a lot of different places and times, and fitting all the data into how things have changed (or stayed the same) through time.

We keep doing sampling and analysis of different sediments, or ice, or whatever we can get our hands on, from different places and different times, and adding that data to what we already know, and this allows us to know more precisely, better, what actually happened. The more information we have, the more certain we can be in our understanding of things. It takes time and lots of work by lots of different people though.

Acids come in different strengths so the amount of H+ that can be released relative to the total concentration of the acid compound is highly variable. Basically, the idea is that "acid" means that there is a favorable condition for releasing an H+ from the rest of the compound. Water is an acid, even. Its pH is 7. It isn't a very strong acid (hardly lets go of the H+ unless really forced to). Some acids, like HCl, though, have almost no hold on the H+ and will lose it easily, and acidify water a lot.

All by itself, the pH of water will be (about) 7, what we call neutral. Very weak acids tend to be made from strong bases (strong bases GRAB loose H+ if it is around), and strong acids when combined with strong bases, tend to make salts and water (like HCl (strong acid) reacts with NaOH (strong base) to make H2O (water) and NaCl (table salt); a solution with a near neutral pH).

In the bulk mix of compounds that is the natural world, and the human body too, the mixture of strong acids, weak acids, strong bases, and weak bases, and other things with effectively no acid behavior at all, when all the competition is done between the various species for grabbing or releasing an H+, the system tends to end up somewhere around neutral. The system "wants" to go to neutral if it can, basically. Strong bases grab H+ just as much as strong acids release it. The end balance in most systems sees this happen, and near-neutral is the result (just as likely to see a strong base as a strong acid, and the two coming together makes a neutral salt and water).

That is the basic reason that the human body is slightly above neutral in pH. It is mimicking (trying to reproduce) the natural world, the ocean that life came from or developed in, originally, which is slightly basic too.

What is an amino acid? They are basically ammonia (NH3) where the H atoms have been replaced, at least in part, by some other large chemical group, many of which are weak acids. We call such compounds "amines" (hence they make "amino" acids), because the nitrogen is in the reduced state (filled to max with electrons, hasn't met other elements that want its electrons even more than it does itself). When reduced nitrogen does meet a strong electron grabber like oxygen, it makes nitrates (and nitrites, sort of the same thing), but that is a little off where I am going with this explanation.

The amine groups tend to be attached to weakly acidic other compounds, or rather weak acids like HCO3-, so one side of the compound is a weak acid, but the other side, or sometimes inside (if all H+ has been replaced by weak acids), it is a strong base. So, because the primary characteristic is a weak acid, the compounds are "amino acids". However, they are not strong acids at all, they are weak acids and do not lower pH by much. If they had been stronger acids, they would have reacted with ammonia to make NH4+ (would have just told ammonia, here is the H+, take it and leave us alone out here in weak base land away from you).

Amino acids are, in effect, the result of that pH-balancing process that happens in nature. The amine group is, if in its normal state of ammonia (NH3), a very strong base. It wants to make NH4+ by grabbing any H+ it can find. the end result is that it sort of does do that, by grabbing on to other compounds that have a weak grasp on an H+, changing the product into a very weak acid rather than its once powerful base. When together, these combined molecules are pretty "happy" in near-neutral conditions. The strong base (ammonia) was neutralized by reacting with acids (like carbonic acid) and now we have a happy "acid" that is not very acidic in behavior, it is very weak. And there are still some bases out there floating around, not strong enough to grab H+ from the weak amino acids, but plenty strong enough to grab H+ from some stronger acids, if they come along, and in so doing, neutralizing them.

So, the system is happy and near neutral. It is where things, taken all together, tend to go to be in balance, somewhere near neutral pH. The world likes to get into some sort of middle balance if it can.

You don't know The Clash? Oh my, to be young again and hear London Calling for the first time.

How much time do you have? The only loss of energy (loss of heat) will be by radiation. There is no conduction and of course no convection. Energy emission by radiation will be from black-body radiation (the emission of "light" energy that depends on the temperature of the body itself).

As temps decrease, the energy being emitted decreases, so the temperature of the body would approach but never really reach the limit of 0 contained thermal energy, although after a huge amount of time, it would be close enough that you couldn't measure the difference. The death of the universe condition (everything at absolute zero or, actually, slightly above because absolute zero is not possible for other reasons) is trillions of years in the future according to estimates I have seen (never tried to calculate it myself; not exactly certain how to).

There is a minor problem with your question, because the black body emissions can be absorbed too, so even in the absence of big energy sources like stars, all matter is being bathed in a low amount of energy, which would counter the loss by emissions, through absorption of radiation coming from other objects. Not much energy, certainly, but still energy. Also, there is a lot of energy zooming around which was emitted ages ago and has yet to interact with matter, and all matter will encounter some of that energy and heat up slightly by absorbing it.

The role of collisions and conversion of energy of motion (kinetic energy) to heat (or kinetic energy at the atomic level, which is pretty much what temperature is truly measuring) would lengthen that cooling process as well. Cannot have true absolute zero if things are moving.

Simple answer is that isolated matter in space does not cool to absolute zero (or as close to that state as can be attained by matter). Stuff in space is a bit warmer, a few degrees warmer in the sparser regions of space and considerably warmer if there is a decent source of emitted energy nearby. Still usually extremely cold by our human standards though, just not absolute zero.

throw in some water and make sugars. About the same idea as photosynthesis. Of course, electricity-driven reactions don't tend to be all that controlled and there is a lot of competition by other reactions, so costly and inefficient is probably a good description. It is why we don't already do that.

Just making carbon would be a fool's game, because the carbon would want to react back with any free oxygen as soon as it could. generally as a big fire. Sure, we can deal with elemental carbon in lots of ways (it doesn't generally spontaneously combust) but you would have to do something with all that carbon. And, of course, there is the question of how you make the electricity in the first place, ideally not from burning coal or inefficiencies would mean you release more CO2 than you break apart/recover.

But yeah, at least it is an idea. Thinking and coming up with ideas is usually a good thing. Most ideas turn out to have more problems than they solve, but occasionally a good one comes up, so don't stop, don't get discouraged that your idea isn't practical. Hardly alone with that.

I have always loved this song, from when I fits heard it on my little 8 transistor radio back when it came out. I would not have guessed 66, I would have put it a year later, which might be when I heard it, being from the back country we called the state of Maine and late for everything fashion). got some great lines ("everybody seems to Naaag me", "even my old man looks good", "I'll change that scene some day"). Very mid/late 60s with sitarish sound (almost stolen from a Rolling Stones riff), good changes, nice chorus, upbeat groove despite the negativity of the lyrics. What is to dislike?

It isn't steam, it is condensed water vapor in air (fog or a cloud). The temperature depends on a few things but generally somewhere around 35 degrees C based on info I just looked up. The water being pushed out of the tower is not water from the steam-generation system used to power the electric turbines. That steam is not usually released except in emergency (the steam is recovered as liquid and reheated to make new steam, in a big circle of use).

Instead, what happens is that the used steam from driving a turbine (now only hot water) is pumped to a radiator of sorts (some sort of closed unit that has air pass over it) located at the base of the tower. Air passing over this radiator heats up (takes heat form the hot water in the radiator, cooling that water more). the cool water is sent back to be made back into steam.

To help cool this air taking the heat from the "radiator", a spray of cold water is typically used. This spray is released near the top of the tower and descends down over the upflowing hot air (cold water is used as a counter flow to the rising hot air to help cool it faster). The water is usually taken from a nearby river or other similar water body. it is "fresh" water, different water from the water used by the electricity-generating system.

Because of this water spray, the hot air gets saturated (maximum humidity), and because maximum humidity decreases as temperature of the air drops, the water vapor condenses into droplets, making a fog or a cloud. This is what we see leaving the plant tower. The water in the discharge fog is not radioactive and it is not all that hot.

I think this is a case of "we can't tie those 3 million differences to neanderthals specifically". Maybe they also had them but we don't have enough sampling to know. What we do have is relic neanderthal genes that have mostly spread throughout all the population in the few hundreds of generations since they mixed in.

It is a misleading statistic. The extent of variation in neanderthals is poorly known simply because identification of that type of variation requires thousands upon thousands of samples to be analyzed, and we don't have that. All we have is enough data to say what all neanderthals had in common with each other (what makes them specifically neanderthal). The extent of variation in existing humans is well known because there are millions of analyses. Not really comparing the same details either (comparing apples to oranges, in a way). Major components that are unique to Neanderthals are being compared to major components of existing humans in the one case, and in the other, trace components among humans are being compared to trace components in other humans. They don't differ from other humans in the 10,000 ways (almost?) all humans differ from neanderthals.

Comparing apples and oranges and saying they are different in 10 easy to identify ways ways and then pointing out there are hundreds of varieties of apples, and then pretending that this proves that apples are more varied than oranges.

Our planet saw a serious period of glaciation so many irregular features were revealed only recently. Ice isn't really very fluid so it creates irregularities, water and air are fluid and get rid of irregularities.

It is mostly a matter of time that the coast has been the coast and eroded only by interaction with nearby ocean which is the cause of irregular coastlines. the north was glaciated, and it created a new landscape (troughs, ridges, large sublinear scratch marks, and so one). It isn't just the coastlines that have obviously different features (lakes abound in recently glaciated terrains, for example). Only a few short thousands of years since the ice went away, so the rounding that happens when ocean meets land (eroding promontories like capes and points and filling in indents like coves and bays with sediment), and the work of long-shore drift, haven't had time to do the work well.

Basically, energy minimization is at work and energy is minimized by elimination of points and dents (just like a rock rolling in a stream gets rounded). The land/sea contact zone is always in the process of linearization and smoothing/rounding, equalization of forces of the ocean against the land. The presence of points acts to turn the waves toward the points and concentrate the energy of the ocean on those outstanding features, eroding them faster. The stuff broken off migrates to open spaces and fills them in.

Really, the same sort of process is happening everywhere that erosion by wind and water is occurring, leading to the smoothing of contact zones (elimination of zones of unequal exposure). Juvenile terrains and renewed terrains are marked by numerous irregular features. Those features do disappear with time. Basins fill in and high points wear away.

This becomes more of a rate consideration. To have flow, the space has to be big enough to allow the molecule through essentially unimpeded, AND the open space has to be connected the entire distance. Unconnected pore space is not very useful to flow.

Down at the molecular scale (sub-micron size range, down near the nanometer (1/1000 of a micron, or 10 angstroms), there will be interaction of the liquid's molecules with adjacent neighbors of the container material, and this is a sort of friction (resistance to flow as the adjacent molecules attract or repel each other when close). With large open spaces, the resistance is only an issue at the edge of the open space, so flow is unimpeded toward the middle of a pipe or crack, but does drag along its edges (water moves slower at the borders of the space). Even rivers show the effects of drag at the edges and bottom (flow goes from free flow/max flow speed to no flow over a very short distance between pure liquid and the "wall" of the passageway).

When you get down to the size range of a few molecules thick, this resistance to flow (interaction with the walls) actually matters, can fill the entire tube or fracture, and to overcome it you need to provide a much larger force to impose the flow (increase differential pressure to overcome the resistance of near-molecule interactions).

The material of the "container" matters because each compound will have its own particular electromagnetic zone of influence (charge space). The materials can also affect the nature of the "pipes" (cracks/flow pathways), so clays, which stack like sheets upon each other, can have a lot of open space, more open space than a quartz silt would (as examples) but the narrowness of the interlayer space means all water is interacting with the clay surface, the entire route that it has to flow (and it is a longer route because it is back and forth, a switchback path rather than almost straight through). On top of the simple constriction and path length aspects, clay has a very strong charge distribution so grabs passing water molecules fairly strongly compared to quartz, which lacks that charge disparity in its structure. Clay is thus generally speaking way less "leaky" than a quartz silt of similar porosity and explains why clay is generally favored as natural seals for landfills or whatever storage we do not particularly want to see leaking.

Oh, I also forget to mention that different fluids have different viscosities (natural resistance to flow) so some liquids will not flow without a strong head (pressure differential) even if the space is pretty wide open: the liquid's molecules interact with each other and are a form of self-produced friction.

A crack is only a leaky one if the pressure (force on the liquid inside the container) is high enough to overcome all of the various forms of resistance that the container will present. Typically, there is a minimum gap width that has to exist for the situation before flow can commence freely. Part of this is due to the resistance to flow in small passageways, and part of it is simply a matter of unit volume per time (slow flow through a small hole cannot let much volume through it; just no room for it). The rate can be offset somewhat by pressurization, by pushing on the liquid inside the container, but there are limits.

As a general idea (and it varies depending on materials), the zone of flow resistance is a few molecules thick from wall into fluid. nanometer-sized passages tend to be pretty resistant to leakage. And even if there is leakage, the volumes of lost material will be extremely tiny. Free flow is not going to happen and what does manage to pass will be doing it very slowly. Faster than by diffusion (migration of molecules, one at a time, through random movement) but not fast in the way we look at things.

Strictly speaking, diffusion occurs in pretty well anything. Diffusion is the (extremely slow) movement of molecules from regions of high concentration to regions of low concentration. The occasional molecule changes place, or wheedles its way in somehow, into the walls of the container. Eventually, some luck molecule makes it the entire way across the barrier. But it is really slow.

Point is, nothing is truly impermeable. Time frames matter (keeps the liquid inside long enough for our needs, is the basic idea we look for). Many ceramics (like for coffee cups) have a lot of open space inside, but the spaces do not connect well at all, so the cup is impermeable. Some clay-based containers are leakier than others, and you might see some sweating if they are imperfectly sealed, but even then, the amount of liquid being lost is tiny so the user doesn't much care, usually.

which makes it so you have to go back to the very first life form (if there was such a thing), if you take it to the logical conclusion. There are some things that all life shares. We are not so much interested in that stuff, because it does not tell us anything we don't already know (that all life appears to have come from a common origin). We are interested in when the things that make us different came into existence, when we "separated" from the other life that is not like us.

Yes, even on earth, there is a depth below surface where temperature is the average annual temperature of the above-earth (water, actually, in most of the earth so not much variation). On land, this mean annual temperature is found at a few to several meters below ground surface: the ground between surface and that constant temperature will vary over the seasons (whips back and forth between summer high and winter low, attenuating (going to zero change) with depth. How deep the whipsaw variations extend depends on the intensity of the change at surface.

Caves and even relatively shallow storage buildings dug into the ground rely on this stability of temperature at depth, so the air in such places tends to be pretty much the same temperature all year round, and until you go very deep like with some mines (where heat from below is enough to raise temperatures; we are deep enough to be well below that depth of mean average temperature so heat from below is on its way to the surface), that temperature is the mean annual temperature of the location.

The idea is that earth surface is at the temperature where solar heating is balanced by black body radiation. Clearly, when the earth was very hot in its youth, black body radiation (emission of "light" energy based on temperature) was much higher than solar heating, so the surface of the earth rapidly cooled due to excess loss of heat to space (much more heat lost to space than gained from space), but the heat loss from the very hot early earth was rapid and the (almost) steady-state balance that now exists came to dominate billions of years ago. Not quite steady state, because the heat flux from below is not zero, so there is always slightly more heat being lost to space beyond the amount that is received from space, but the difference is very small now. Loss of internal heat is very slow. It is a factor, but a tiny one.

Now, what we see is the rate of heat migration from inside to surface has "mean surface temperature" as the lower limit for the geothermal gradient. Locally, like when there are massive magma intrusions to shallow depth, there can be a temporary disruption of the balance and heat loss in that region can be measurably higher than average annual solar heating, but it lasts briefly only, like a million years time frame (time frame depends a lot on how active hydrothermal fluid convection is, because convection is way faster than conduction).

When the interior of a planet falls to the mean average surface temperature, there is no more migration of heat from the interior. The entire planet would be kept at that mean surface temperature. Planets are so large, and heat flow by conduction through rock is so slow (absent convection by circulating or migrating fluids and the occasional rising blob of magma) that no planetary bodies that we know about are that cold, yet.

Small bodies like asteroids out in space have very cold internal temperatures but are not at the temperature of deep space because they do get warmed slightly by the sun. On earth, where seasons happen, the summer is a period where heat received by the sun is more than is lost to space, but heat during winter is less than is lost to space. The mean annual temperature is the temperature where those shorter-term losses and gains get balanced to no change.

I suppose even asteroids and comets have "seasonal" variations, even if the seasons are many years long. Clearly, a comet near the sun that is degassing is in what can only be seen as a form of "summer", even if the seasons are imposed from orbital variations rather than tilted axis of rotation. Earth does also have some orbit-dependent heating change, but the orbit is almost circular so not a huge different. It does matter though (see Milankovitch cycles).

Also, the presence of hydrosphere and atmosphere are important in determining what that "mean annual surface temperature" will be. Greenhouse effects, of a sort. This is why Venus is way hotter at the surface than it ought to be based on simple solar flux considerations. So much of its radiant heat loss to space gets trapped by the atmosphere that an important portion migrates back to surface if the surface cools down, so the stable or steady state temperature at surface is higher than it would be in absence of atmosphere. It cannot radiate heat to space at the rate that its surface temperature would have it. This is also true on earth but to a much smaller extent.

The basic problem is that heat cannot leave where it is now unless there is somewhere cooler for it to move into. So, inside the earth (or any planet, really) the internal heat is simply unable to leave except very slowly.

It depends on which density you want: bulk density or density of the solid fraction only, and of course how precisely you want to determine the value.

With solids or liquids, density is easy to determine, all you need to do is establish the mass (weight), which you use with a scale, and volume, which you can typically get by adding the material to a known volume of liquid in a measuring device like a graduated cylinder, and measure the volume change after addition. You could actually do this at the same time, by having the volumetric container on a scale when you add the liquid or solid. Get both volume and weight change in one move.

This will work with a sponge too, to get the density of the sponge material (assuming that you have total permeability, no blocked void spaces when immersed in liquid).

If you want a bulk density of something porous like a sponge, the best method is to measure mass (weight) dry and wet (saturated). The volume of the open space is defined by the mass of water contained within that open space (the change in mass from dry to wet is due to contained water only, and we have established water density to more precision than you will likely need for your purposes-you probably won't need to correct for temperature).

I don't do gas measurements, which generally has a pressure dependence and you would need to do a pressure-mass curve using a fixed volume container (a glass bulb of known volume, seems a good way to go). Empty the glass bulb of all air, measure its weight, then inject it with the target gas, and measure its weight. The change will be due solely to the added gas mass. Do that at a few different pressures to establish the pressure-density curve.

You could, conceivably, crush the porous solid to eliminate pore space and then get the powder mass and volume the same as with any solid. From that, you could establish the pore volume in the original sample (measure volume of the uncrushed sample and its weight and go from there with some simple math).

If you want to determine surface area of a porous solid, well, then you would need to go into more complicated or higher tech methods.

I think one of the biggest misconceptions that the average person has about chemical compounds is to think of them as unchanging. The reality is a lot more complicated. Exchange of like atoms (oxygen for oxygen, or hydrogen for hydrogen say) is always going on. We know this from stable isotope studies and even from radioactive tracer work, among many other reasons and evidence.

Systems are not static at the atomic level, at the molecular level. More like a giant square dance, where the overall form is constant but individual partners move around, trade places. The rate of trading (and how far a trade partner can migrate away) varies considerably depending on the physical state of the compound, whether solid, liquid, or gas. Solids are slowest and gases are fastest, as a general idea.

People talk about things like a water molecule, as if it is something that has existed since it first formed, maybe billions of years ago, but that is not exactly true. In bulk, sure, that mass of 10^23 (1 followed by 23 zeroes, perhaps a cup worth of water) has been water that long, perhaps, but each molecule is constantly smacking other ones and in the process, switching atoms (changing partners). Some of those changes involve other compounds too (the O in CO2 can end up as the O in H2O (water), and the reverse, with time).

It is certainly true that the rate of exchange is highly variable, and depends on the system and things like temperature (amount of energy shared around the system). It is also true that the distance over which such exchange occurs can be very tiny from our point of view. A hydrogen atom moving down a chain of carbon atoms in a solid over time is only moving on the order of nanometers (billionth of a meter), but it is moving. Which particular one is moving, or how many are moving at the same time, or what all is happening in detail is very hard to see or measure, but we can prove that it must have happened, and theory says it should anyway (the world at atom level is really busy).

This is pretty much the idea behind chemical equilibrium, that the compound is stable and persists even if the individual atoms move around. It is a dynamic process, but it is a steady state (what goes one way is offset by things going the other way, and not at all a case of once made, never changes, although some conditions can be, effectively, one-directional, going from all this to only that, when one form is way more stable than the original form). Basically, reactions will proceed primarily in one direction until the rate of reaction coming back gets to be about equal (that is what equilibrium means). Then things just dance together, switching partners (individual atoms or perhaps ion groups, particularly the anion complexes, which tend to migrate as a unit) but not switching the bigger forms that we call compounds.

As to the primary question, the persistence of an organic (or any) chemical compound through time depends on its chemical stability, which depends a lot on its circumstances (what else is nearby and competing for energy and electrons, and how easily can atoms change places, and whether the existing arrangement is more stable than alternatives using the very same atoms).

Some compounds are very easily broken and converted into something else. These compounds are the first to disappear. They also tend to be the simplest compounds (with organic molecules, the short chains will break down fairly easily, but they do get somewhat replaced by the breakdown of bigger chains into shorter chains).

When bacteria or bugs or whatever find these compounds in the environment, they tend to eat them all right up, really fast. These compounds will also break up just from non-biological reasons fairly quickly.

Other different bacteria ("bugs") come along later and try to eat the residues. Some compounds do not yield enough energy to make it worthwhile for bacteria or whatever to even attack them and break them up. Costs more to do that than they get out of it. Those molecules just sit there for eons. No energy benefit for breaking them up even if they might not be the most stable form for what they are made from. The energy wall they need to cross to get to the more stable forms is simply too high for it to happen except rarely.

Other compounds are so stable, or so difficult to split apart, that the still exist after millions of years, changing only slightly between burial and our return to surface in crude oil.

Some compounds persist for so long that we use them as markers, as indicators of which plant (or animal) types are the probably source.

What is the lifespan of an organic molecule? It depends very much where that molecule ends up going and how unstable that molecule would become for new conditions. If you do not change conditions, the stuff will not change very fast if at all. Might still change atoms with near neighbors every so often, but the compound WILL persist.

If you take something like butane (a fairly simple organic molecule), it will last as long as you keep it in a container, but as soon as you flick your bic and press the lever to let gas out, POOF, it is destroyed in flame. Some compounds like PCBs and dioxins are so complex, and so noxious to life, that they persist almost forever, as far as we can tell. That is actually what some compounds we make are called, "forever chemicals", because nothing around our near-earth situation will break them up. We can only break them up at extremely high temperatures in the presence of oxygen or some similar electron-grabber, or in some other fairly difficult way.

How long does an organic compound last? from seconds to billions of years, and pretty well any time in between, depending on what you do to them.

Depends a bit on what you mean by that word "radiation". Radiation from radioactive elements is mostly electromagnetic (EM) energy ("light" even if it might be outside visible range) so redshift or blueshift will happen (doppler effect as it applies to light/EM radiation, which moves as a waveform of fixed frequency).

If it is a particle emission (alpha or beta decay, say), then there is no waveform involved so there will be no change in perceived wavelength at impact with the particle (no wave at all). The impact will be less (or more if a head-on collision) forceful, is all.

There is always also some EM emission whether or not there is particle emission, and the EM emission will do the wavelength shift if the receiver is moving fast enough to cover a significant proportion of a wavelength during the time interval of the individual wave. If the receiver moves a third of a wavelength distance in the time it takes for a second wave to arrive, then the perceived wavelength will be reduced or increased by as much as 1/3 (maximum change if wave and receiver are moving in the same or opposite direction but less if the two are moving obliquely).

Redshift with light from stars and galaxies is how we know that the universe is expanding; the further away the source, the more it redshifts, and further away means more time since the light began the trip. How we know how far away the source is, well, that is a different problem.

yes, you understand correctly. Proximity to water bodies, dryness of the air (cloud cover or lack of it) and other issues definitely matter.

A major factor, however, is the fact that daytime heating is a lot less intense when the sun is a lot lower to the horizon, so the heating is less than it would be if the sun were higher (it isn't only that there is less time of sun exposure, but also that the sun is not even close to as high in the sky).

The local temperature "wants" to be at the median temperature for the location (where it would stay if input and output was the same across the entire 24 hour period). In winter, the amount of heating is a lot less (much less sunlight per unit area), so the increase ABOVE median is smaller, and thus the cooling is equally less severe to get back to median, and the magnitude of variation is smaller.

One cannot ignore the role of atmospheric moisture though. This is a major factor in why cloudless winter nights tend to be so dang cold but cloudy weather isn't generally cold. The clouds and the greenhouse effect of water limit the amount of heat which can make it out into space, so the lower atmosphere stays warmer (loses a lot less heat to space). The flip side, of course, is that cloudiness also reduces the amount of sunlight making it down to the ground and heating things up in daytime. It is definitely a complicated process, many factors matter.

Glass (non-crystalline solid=NCS) can be reflective but it is again a matter of wavelength and gap size. Does the object act like a solid zone of contact to the waves?

The general idea of wave behavior is that waves reflect when obstructions are repeated and have a gap range smaller than the wavelength (so the wave "sees" the series of objects as if they are a solid wall). When wavelengths get down into the range of the gap size, diffraction occurs. When gap sizes are way bigger than wavelength, nothing really happens to the waves. it is as though no such objects were even present.

So, for your question, you have to consider what the wavelength of the energy is, and for gamma rays it is on the order of picometers (the range is actually several orders of magnitude, but for discussion, 10^11 m is the big end and picometers is 10^-12 m).

The spacing between atoms in a typical crystal structure is longer than about 100 picometers, so gamma rays, except perhaps the very long end of the range, basically do not see crystalline solids as "solid" structures (the gaps are big enough that the waves pass through mostly unaffected, as if nothing were there at all). So, there are no crystalline solids which can reflect gamma rays. You would have to get into subatomic matter and such materials do not cluster in large enough masses to create an important obstruction.

Sort of like an island a few km offshore from land. The small waves do "see" the island and get blocked and reflected by it, but the overall pattern of waves is unaffected (only a small proportion of the waves are obstructed by the lone object and the rest move on unchanged). There are no substances we possess or can create which can produce the regular obstructions at the necessary tiny gap size needed to force gamma rays to reflect instead of basically ignore them.

There are things that can be done using energy fields though, but I don't know much about that at all. Not basic knowledge for a geologist (basic optics is, because of optical mineralogy and coloration of minerals-we geologists are jacks of all trades in science terms - we know something about a bit of everything).