Memories from Fifty Years Ago: Invasion of Czechoslovakia 2.

In my last post, I had managed to get my rather aged Ford Anglia up the side of a bank from a riverbed, the bridge having been taken out. I drove through a belt of trees, and found myself at the back of a Russian military camp. There was nothing for it. Fortunately, I realised that whatever else I did, I must not stop, and I must not look sideways, but equally I must not ignore those on the side of the road. I tried to look as if I were supposed to be there, and drove on at about 20 mph, and tried to give puzzled expressions or a “bored look”. This must have been weird for them. A beat-up right hand drive car coming from the base of their camp carrying a Czech flag, with the road definitely cut behind it. What I was hoping was that the ordinary soldiers there would think it must be something concocted up by authority, and one thing I noticed at this time was that Russian military discipline was good. More on this later.

Anyway, I drove through the camp unhindered, and on towards Praha, but keeping a good look at my rear vision. When nothing seemed to be following I accelerated up to a reasonable cruising speed.

As I entered Praha, great relief: there was a petrol station selling petrol. I joined the queue. It may have been rationed, but the person at the pump saw my flag and enthusiastically filled up my tank. That was a big worry off my shoulders, and I unloaded more crowns there.

As I was to rejoin the highway, I noticed tanks driving up. I darted onto the road, on the basis that I knew what a Division looked like in size, and while I had no idea how much of one was being deployed, why take risks? So there I was, with a T54/55 right behind me. (I could not tell the difference between the two options, which, as an aside, are rather modest, but I knew they were the main battle tanks of the Soviets.) Then, as this odd little convoy entered Praha, people were lined up on both sides of the road. They saw me and cheered, then jeered at the tank. I discovered that a T54/55 loses power on its cruising speed at about 22 mph, but the next gear down roars at about 23 mph. It was one awkward speed zone, so I oscillated in it, keeping a clear look at what the tanks was doing. The T54/55 had a crash box, and the driver’s double clutching technique left a little to be desired, and not helped by the huge difference in engine revolutions for the two gears at the same speed. Accordingly, there were a number of satisfying crunches from the tank’s gearbox, which brought loud cheers. I even had some flowers thrown my way. It was one of the weirder experiences of my life, and I will never have anything like it again.

Eventually I reached somewhere near the centre, and I knew this had to stop, so I turned off to find somewhere to park, have lunch, and another Czech beer. Then I went for a bit of a walk around central Praha, hoping to find information. Two chilling memories of the time. The first was from back in Olomouc. I remember looking down a side street where a wedding must have been going on. The bride came out, looked around, and burst into tears. Back on my walk down a street in Praha, the number of people out walking were few, but when I heard a burst of machine gun firing, everybody dived towards the walls of the buildings, and looked at me as if I were mad for just continuing walking. I could tell the guns and bullets were not in this street, but just in case my cover was going to be the gutter at the edge of the street. Only thing was, I did not want to take such cover until I had to, because diving onto concrete can hurt, and gutters are dirty.

Then, I found what I needed: an information kiosk. I asked for information, and what I found was not exactly what I needed: the borders were all closed. One might reopen tomorrow. So, was there somewhere where I could spend the night? Come back at 5.00. So I could be a tourist for the afternoon. It was not long before I noticed a protest march, so I “joined/followed” it as it went into Wenceslas Square. That was ominous. Across the middle of the square the Russian military had painted a yellow line. Some meters back was a row of Russian soldiers with machine guns. The protest stopped, and it was clear that they could do what they liked their side of the line, but that line was not to be crossed. Gradually the noise became louder and I sensed this was a good time to be somewhere else, preferably with stone/concrete between me and what was going to happen. I got around the corner of a building, and the machine guns opened up. One of the odder moments of my life was ten years ago, when I was washing dishes while listening to the radio, and I recognised this pattern of lmg firing. There had been no announcement as to what it was, but I told Claire it would be about 2.30 pm, August 24, Wenceslas Square. Of course I don’t know whether it was for sure, but I felt confident. The sound was an introduction to a program marking the 40th anniversary, and they never said when and where the recording was made, but it seemed just what I heard that day.

Later in the afternoon, I wandered onto the Charles Bridge to look at the Vltava, and Russian soldiers camping on the riverbank. Interestingly, it appeared that at least some were not issued with socks, and they wrapped their feet in rags before putting on their boots. Anyway, while I was watching this, a Russian officer came up and stood beside me to look down at the river. Apparently, he wanted to talk, which was a problem because the only common language was German and neither of us were proficient. Judging by his epaulette, I guessed Major or Lieutenant Colonel, but I was not familiar with Russian ranks and emblems. Anyway, what I managed to gather was that the Russian soldiers were quite perplexed. They thought they were here at the request of the Czech people, and all they got were protests, insults, and there was no cooperation. I tried to point out they thought this was an occupation, and I added I had seen tanks with Okkupanti and swastikas painted on them. (Yes, spray paint cans were in full use). He agreed, which surprised me. It also turned out that the protests of one town really hurt them because there was no protest. Everybody was subdued and extraordinarily obedient. The town was Lidice. We talked for a while, and I realised that the average Russian officer was not exactly happy about this invasion, but orders were orders. They thought they were going to do good things for the citizens and they did not like what they saw, and the whole situation was bad for both sides. They were not really well supplied, and expected the Czechs would help with food, but all the food got hidden away.

Interestingly, as far as I could tell, the Russians did not pillage. Instead, they tightened their belts, arranged for more supplies, and as far as I could tell, the ordinary soldiers behaved well. The Czech citizens were respected as long as they did not “cross a line”, and while I suspect there would be incidents of soldiers doing what they should not have, by and large that did not happen. Russian military discipline was good.

All of which was all well and good, but I was still there. Time to go back to the information kiosk, and what happened next, I am afraid, is for yet another post, next week.

Meanwhile, you may be interested in

I found this article interesting, but it is not entirely representative. The most obvious difference is the black and white photos give the impression of overall grimness, but actually the weather was absolutely clear, and yes, there were plenty of protests, but they were not that grim looking. All the Czech flags being waved actually gave a colourful impression. The photos give the impression of chaos, destruction and rubbish everywhere, but that was not the case either. What you see there are isolated incidents. There is a photo of a tank burning, but that would be exceptional. There were protests, insulting graffiti on tanks, but by and large all protests were peaceful. There would be mistakes. The photo of a young man shot while trying to put a Czech flag on a Russian tank may well have arisen because there are no obvious places to place such a flag. Had the man tried to open something, the tankers would have to assume something dangerous, such as a Molotov cocktail, could be thrown in, and they would shoot. There would be damaged buildings. You cannot fire all that ordnance and not do damage, but by and large that was atypical, and concentrated around key parts of Praha. It said there were food queues. I had no difficulty buying food. The photos would be real, but exceptional and not really representative of what was happening at large.


Memories from Fifty Years Ago: Invasion of Czechoslovakia 1.

This post is to remind myself that fifty years ago (1968) my little Ford Anglia and I did a road tour behind some of the old Iron Curtain. I was something of an oddity, and I was sometimes referred to as a “stupid Bulgarian” for putting the GB sticker on back to front. The cobbled roads of Poland did not do a lot of favours for the car, since driving towards Krakow on August 22 the clutch mechanism began leaking hydraulic oil, and finding somewhere to get spare oil was a nightmare. Fixing it was impossible; getting the appropriate parts for a very aged British car behind the Iron Curtain was not going to happen. Interestingly, when I stopped at probably the only garage between Gdansk and Krakow, the Poles there refused to speak German. Germans could go to hell! When I managed to get through to them that I was English (OK, I wasn’t, but why a New Zealander was driving a British car would be to much) they suddenly became very helpful. Memories of the Third Reich had not died down.

Back on the road, and before long I overtook what I assume was a motor rifle Division. Trucks carrying soldiers, tanks, artillery, it seemed to take a lot of the afternoon passing it, with me driving on the left hand side of the road, which, of course, felt like usual driving. It seemed a little ominous because I had one more day on my Polish visa, and if you look at a map, options were limited. Interestingly, when I got into my car the following morning in Krakow, the usual black-market currency trader came up to me, and when he found I was going to Czechoslovakia, he immediately offered Czech crown at a huge discount. Even stranger, he would take zloty instead of the usual hard currency. I emptied out my zloty previously bought at a big discount in exchange for some D-mark, and which I could not find anything to spend them on, and got a big fistful of crowns.

On August 23, 1968, I crossed the border at Cieszyn into Czechoslovakia, as it was then known. Unbeknown to me, the Russian army had crossed the previous night. Getting across the border was interesting, but my expiring Polish visa meant there was nowhere else to go, and I had a legitimate visa for getting into Czechoslovakia. The border guards gave way to a military officer, and when I said I was trying to get to Vienna, he let me through. I stopped at an open square in Frydek-Mystek and bought myself a beer and some lunch. I was glad to taste Czech beer, which was far better than Polish beer, and looked out to see a tank on the other side of the square, and a number of soldiers. It was a beautiful sunny day, and the soldiers seemed to be dozing, while the people ignored them. Someone wanted to put a Czech flag on the aerial of my car, so I let them. Then it occurred to me that the person who let me through the border probably had a Russian uniform. Oops! The next bit of news was all the borders were closed.

So, where to go? The next step was fairly obvious: Olomouc. From there, roads went to Brno or Praha. Brno is near the border with the route to Vienna, but there were likely to be far more westerners in Praha, which meant that with more options, it was more likely a border would open soon. It was also reasonably obvious that I would have to stay the night somewhere, so that somewhere might as well be Olomouc. When I got there, all was not well because it was late afternoon. I tried the odd hotel, and met someone who would make a cameo appearance in one of my novels: he spoke 13 languages, so he claimed, but none were English, French or German. So, on the road again. I took the road towards Praha (and I cannot recall whether this was a decision or accidental) and nothing much happened except it started to get darker, then it was clearly night. I was going at about 60 mph, and came over a hill when I saw a small fire to the left and something not right. Emergency avoidance! I swerved left and went into a four-wheel drift, sending a shower of stones towards some clearly frightened soldiers (they would see a ton of steel heading their way). Fortunately, my youthful time spent doing drifts on gravel roads came to my assistance as I held the car and carefully made it back onto the road. (Hint – returning to the road is the most dangerous part as it is easy to overcompensate and start rolling.) Going left was pure instinct. Nevertheless, I had avoided colliding with a tank parked in the centre of the road and covered with camouflage netting to hide its shape. All the same, I decided I had better stop driving soon.

I came to a little village where the road turned right, but there was a further road going left and straight ahead. The road signs had been switched, directing traffic to Praha straight ahead. I stopped, and the Czech flag did a good thing – it brought someone who spoke English. He told me the obvious, but I said I really needed somewhere to stop. He took me to a hotel down to the left, and I found it was illegal to be moving. My guide said he would burn down the hotel if the manager didn’t accept me. Would I permit him to register me from the day before? Of course. Everyone was happy. After ensuring my belongings were in the room, I went back to the cross-roads where part of a Division was passing through. There was a Czech out there indicating the false road, where the sign was pointing but the soldiers were not to be fooled. There was a gap in the traffic, and I approached my new friend, and suggested he get the Czech on the road to point the right way: the drivers would not believe a Czech was trying to be helpful. So when the next part of the Division arrived, the Czech was ignored and the trucks started going down the wrong way. This went on for about half an hour, when a driver was almost going down the wrong way but he realised his mistake and hit the brakes. Everybody stopped behind him. He flung his truck into reverse and shot backwards, furious at the agitated crowd. What he forgot was he had a trailer with an artillery piece on the back, the barrel of which smashed the following truck’s window and the driver only just evaded. The crowd roared. Eventually, this was sorted and what was left of the Division went the correct way. I later learned that a Polish Division was split into five parts that night and it took three days or so to get them all back together. My small contribution to military history!

Next morning I was off to Hradec Kralove, where I found a garage. They could not sell petrol, but I did get a litre of hydraulic oil. They refused payment; it was illegal to sell anything under the occupation. My Czech flag was working! I took the road to Praha and all was well on another gorgeous morning. I passed a detour sign, but I knew better. (I had passed lots of them before.) I kept driving and I must have been fairly close to Praha when there was a minor disaster in the making. There was a dry riverbed, but no bridge. On the other side the road went behind a belt of trees. The last detour sign appeared to be true, but I had only two gallons of petrol left and there was no way I could make it around the detour. I took something of a deep breath, put the car in second gear and went down the bank to the streambed and floored the accelerator. I got up to about 45 mph by the other side, sustaining ferocious bouncing, then up the other side. I had just enough momentum to get over the lip and onto the road. Joy! Through the belt of trees and . . . Oops. I was at the back of a Russian military camp. This Czech flag may not be working in my favour now . . .

More next week for those interested.

Volatiles on Rocky Planets

If we accept the mechanism I posted before is how the rocky planets formed, we still do not have the chemicals for life. So far, all we have is water and rocks with some planets having an iron core. The mechanism means that until the planet gets gravitationally big enough to attract gas it only accretes solids, together with the water that bonded to the silicates. There re two issues: how the carbon and nitrogen arrived, and if these arrived as solids, which is the only available mechanism, what happened next?

In the outer parts of the solar system the carbon occurs as carbon monoxide, methanol, some carbon dioxide, and “carbon”, which essentially many forms but looks like tar, is partially graphite, and there are even mini diamonds. There are also polyaromatic hydrocarbons, and even alkanes, and some other miscellaneous organic chemicals. Nitrogen occurs as nitrogen gas, ammonia, and some cyanide. As this comes closer to the star, and in the region of the carbonaceous chondrites, it starts getting hot enough for some of this to condense and react on the silicates, which is why these have the aminoacids, etc. However, as you get closer to the star, it gets too hot and seemingly the inner asteroids are mainly just silicates. At this point, the carbon is largely converted to carbon monoxide, and the nitrogenous compounds to nitrogen. However, on some metal oxides or metals, carbon forms carbides, nitrogen nitrides, and some other materials, such as cyanamides are also formed. These are solids, and accordingly these too will be accreted with the dust and be incorporated within the planet.

As the interior of the planet gets hotter, the water gets released from the silicates and they lose their amorphous structure and become rocks. The water reacts with these chemicals and to a first approximation initially produces carbon monoxide, methane and ammonia. Carbon monoxide reacts with water on certain metals and silicates to make hydrocarbons, formaldehyde, which in turn condenses to other aldehydes (on the path to making sugars) ammonia (on the path to make aminoacids) and so on. The chemistry is fairly involved, but basically given the initial mix, temperature and pressure, both in ready supply below the Earth’s surface, what we need for life emerges and will make its way to the surface. Assuming this mechanism is correct, then provided everything is present in an adequate mix, then life should evolve. That leaves open the question, how broad is the “right mix” zone?

Before considering that, it is obvious this mechanism relies on the temperature being correct on at least two times during the planetary evolution. Initially it has to get hot enough to make the cements, and the nitrides and carbides. Superficially, that applies to all rocky planets, but maybe not for the nitrides. The problem here is Mars has very little nitrogen, so either it has gone somewhere, or it was never there. If Mars had ammonia, since it dissolves in ice down to minus 80 degrees C, ammonia on Mars would solve the problem of how could water flow there when it is so cold. However, if that is the case, the nitrogen has to be in some solid form buried below the surface. In my opinion, it was carried there as urea dissolved in water, which is why I would love to see some deep digging there.

The second requirement is that later the temperature has to be cool enough that water can set the cements. The problem with Venus is argued that it was hotter and it only just managed to absorb some water, but not enough. One counter to that is that the hydrogen on Venus has an extremely high deuterium content. The usual explanation for this is that if water gets to the top of the atmosphere, it may be hit with UV which may knock off a hydrogen atom, which is lost to space, and solar wind may take the whole molecule, however water with deuterium is less likely to get there because the heavier molecules are enhanced in the lower atmosphere, or the oceans. If this were true, for Venus to have the deuterium levels it must have started with a huge amount of water, and the mechanism above would be wrong. An embarrassing problem is where is the oxygen from that massive amount of water.

However, the proposed mechanism also predicts a very large deuterium enhancement. The carbon and nitrogen in the atmosphere and in living things has to be liberated from rocks by reaction with water, and what happens is as the water transfers hydrogen to either carbon or nitrogen it also leaves a hydroxyl attached to any metal. Two hydroxyls liberate water and leave an oxide. At this point we recall that chemical bond to deuterium is stronger than that to hydrogen, the reason being that although in theory the two are identical from the electromagnetic interactions, quantum mechanics requires there to be a zero point energy, and somewhat oversimplifying, the amount of such energy is inversely proportional to the square root of the mass of the light atom. Since deuterium is twice the mass of hydrogen, the zero point energy is less, and being less, its bond is stronger. That means there is a preference for the hydrogen to be the one that transfers, and the deuterium eventually turns up in the water. This preferential retaining of deuterium is called the chemical isotope effect. The resultant gases, methane and ammonia as examples, break down with UV radiation and make molecular nitrogen and carbon dioxide, with the hydrogen going to space. The net result of this is the rocky planet’s hydrogen gradually becomes richer in deuterium.

The effects of the two mechanisms are different. For Venus, the first one requires huge oceans; the second one little more than enough water to liberate the gases. If we look at the rocky planets, Earth should have a modest deuterium enhancement with both mechanisms because we know it has retained a very large amount of water. Mars is more tricky, because it started with less water under the proposed accretion of water mechanism, and it has less gravity and we know that all gases there, including carbon dioxide and nitrogen have enhanced heavier isotopes. That its deuterium is enhanced is simply expected from the other enhancements. Venus has about half as much CO2 again as Earth, and three times the amount of nitrogen, little water, and a very high deuterium enhancement. In my mechanism, Venus never had much water in the first place because it was too hot. Most of what it had was used up forming the atmosphere, and then providing the oxygen for the CO2. There was never much on the surface. To start with Venus was only a bit warmer than Earth, but as the CO2 began to build, whereas on Earth much of this would be dissolved in the ocean, where it would react with calcium silicate and also begin weathering the rocks that were more susceptible to weathering, such as dunite and peridotite. (I have discussed this previously: ), on Venus there were no oceans, and liquid water is needed to form these carbonates.

So, where will life be found? The answer is around any star where rocky planets formed with the two favourable temperature profiles, and ended up in the habitable zone. If more details as found in my ebook “Planetary Formation and Biogenesis” are correct, then this is most likely to occur around a G type star, like our sun, or a heavy K type star. The star also has to be one of the few that ejects it accretion disk remains early. Accordingly life should be fairly well spaced out, which may be why we have yet to run into other life forms.

Ebook discount

Discounted to 99c/99p from August 9 – 16: Jonathon Munros, book 3 of the First Contact trilogy. Jonathon Munro, a truly evil man, was to be removed from society and an android is made to substitute for him. The android has to study what Jonathon did, so he could act like him. When the android learned to self-replicate, what could possibly go right? A story of corruption, revenge, greed for power, and sentient machines in a dystopian future.

Rocky Planet Formation

In the previous posts I have argued that the evidence strongly supports the concept that the sun eliminated its accretion disk within about 1 My after the star formed. During this 1 My, the disk would be very much cooler than while the sun was accreting, and the temperatures were probably not much different from those now at any given distance from the star in the rocky planet zone. Gas was still falling into the star, but at least ten thousand times slower. We also know (see previous posts) that small solid objects such as CAIs and iron bearing meteorites are much older than the planets and asteroids. If the heavier isotope distributions of xenon and krypton are caused by the hydrodynamic loss to space, which is the most obvious reason, then Earth had to have formed before the disk cleanout, which means Earth was more or less formed within about 1 My after the formation of the sun.

The basic problem for forming rocky planets is how does the rocky material stick together? If you are on the beach, you may note that sand does not turn into a solid mass. A further problem is the collisions of large objects involve huge energies. Glancing collisions lead to significant erosion of both objects, and even direct hits lead to local pulverization and intense heat, together with a shock wave going through the bodies. When the shock wave returns, the pulverized material is sent into space. Basically craters are formed, and a crater is a hole. Adding holes does not build up mass. Finally, if the two are large enough and about equal sized, they each tend to shatter as a consequence of the shock waves. This is why I believe the Monarchic growth makes more sense, where what collides with the major body is much smaller. Once the forming object is big enough, it accretes all small objects it collides with, due to gravity, but the problem is, how do small bodies stick together?

The mechanism I developed goes like this. While the star is accreting, we get very high temperatures and anything over 1000 degrees will lead to silicates softening and becoming sticky. This generates pebbles, stones and boulders that get increasingly big as we get closer to the star, because more of the silicates get more like liquids. At 1550 degrees C, iron melts, and the iron liquids coalesce. That is where the iron meteorites come from. By about 1750 – 1800 degrees silicates get quite soft, and it may be that Mercury formed by a whole lot of “liquids” forming a sticky mass. Behind that would be a distribution of ever decreasingly sized silicate masses, with iron cores where temperatures got over 1550. This would be the origin of the cores for Earth, Venus and Mercury. Mars has no significant iron core because the iron there was still in the very small particulate size.

The standard theory says the cores separated out with heavier liquids sinking, but what most people do not realize is that the core of the Earth does not comprise liquid silicates, at least not the mobile sort. You have no doubt heard that heat rises by convection at hot spots, but it is not a sort of kettle down there. The rate of movement has been estimated at 1 mm per year, which would mean the silicates would rise 1000 km every billion years. We are still well short of one complete turnover. Further an experiment where two different silicates were heated to 2000 degrees C under pressure of 26 Gpa showed that the silicates would only diffuse contents a few meters over the life of the Earth. They may be “liquid” but the perovskite silicates are so viscous nothing moves far in them. So how did the core form so quickly? In my opinion, the reason is the iron has already separated from the silicates, and the collision of a whole lot of small spherical objects do not pack well; there will be channels, and molten iron that already exists in larger masses will flow down them. Less-viscous aluminosilicates will flow up and form the continents.

The next part unfortunately involves some physical chemistry, and there is no way around it. I am going to argue that the silicates that formed the boulders separated into phases. An example is oil and water. Molecules tend to have an energy of association, that is all the water molecules have an energy that tends to hold them all together as a liquid as opposed to a gas, and that tends to keep phases separate because one such energy between like molecules is invariably stronger than the energy between different ones. There is also something called entropy, which favours things being mixed. Now the heat of association of polymers is proportional to the number of mers, while the entropy is (to a first approximation) proportional to the number of molecules. Accordingly, the longer the polymers, the less likely they are to blend, and the more likely to phase separate. That is one of the reasons that recycling plastics is such a problem: you cannot blend them because if the polymers are long, they tend to separate in processing, and your objects have “faults” running through them.

The reason this is important, from my point of view, is that at about 1300 degrees C, calcium silicate tends to phase separate from the rest, and about 1500 degrees C, a number of calcium aluminosilicates start to phase separate. These are good hydraulic cements, and my argument is that after cool down, collisions between boulders makes dust, and the cements are particularly brittle. Then if significant boulders come together gently, e.g. as in the postulated “rubble piles”, the cement dust works it way through them, and water vapour from the disk will set the cement. This works up to about 500 degrees C, but there are catches. Once it gets significantly over 300 degrees C, less water is absorbed, and the harder it is to set it. Calcium silicate only absorbs one molecule of water, but some aluminosilicates can absorb up to twenty molecules per mer. This lets us see why the rocky planets look like they do. Mars is smaller because only the calcium silicate cement can form at that distance, and because iron never melted it does not have an iron core. It has less water because calcium silicate can only set one molecule of water per cement molecule, and it does not have easily separable aluminosilicates so it has very little felsic material. Earth is near the optimum position. It is where the iron core material starts, and because it is further from the sun than the inner planets, there is more iron to sweep up. The separated aluminosilicates rise to the surface and form the felsic continents we walk on, and provided more water when setting the cement. Venus formed where it was a little hot, so it was a slow starter, but once going, it will have had bigger boulders to grow with. It has plenty of iron core, but less felsic material, and it started with less water than Earth. This is conditional on the Earth largely forming before the disk gases were ejected. If we accept that, we have a platform for why Earth has life, but of course that is for later.

From Whence Star-burning Planets?

This series started out with the objective of showing how life could have started, and some may be wondering why I have spent so much time talking about the cold giant planets. The answer is simple. To find the answer to a scientific problem we seldom go directly to it. The reason is that when you go directly to what you are trying to explain you will get an explanation, however for any given observation there will be many possible explanations. The real explanation will also explain every connected phenomenon, whereas the false explanations will only explain some. The ones that are seemingly not directed at the specific question you are trying to answer will nevertheless put constraints on what the eventual answer must include. I am trying to make things easier in the understanding department by considering a number of associated things. So, one more post before getting on to rocky planets.

In the previous two posts, I have outlined how I believe planets form, and why the outer parts of our solar system look like they do. An immediate objection might be, most other systems do not look like ours. Why not? One reason is I have outlined so far how the giants form, but these giants are a considerable distance from the star. We actually have rather little information about planets in other systems at these distances. However, some systems have giants very close to the star, with orbits (years) that take days and we do not. How can that be?

It becomes immediately obvious that planets cannot accrete from solids colliding that close to the star because the accretion disk get to over 10,000 degrees C that close, and there are no solids at those temperatures. The possibilities are that either there is some mechanism that so far has not been considered, which raises the question, why did it not operate here, or that the giants started somewhere else and moved there. Neither are very attractive, but the fact these star-burning giants only occur near a few stars suggests that there is no special mechanism. Physical laws are supposedly general, and it is hard to see why these rare exceptions occur. Further, we can see how they might move.

There is one immediate observation that suggests our solar system is expected to be different from many others and that is, if we look again at LkCa 15b, that planet is three times further from the star than Jupiter is from our star, which means the gas and dust there would have more than three times less concentrated, and collisions between dust over nine times rarer, yet it is five times bigger. That star is only 2 – 3 My old, and is about the same size as our star. So the question is, why did Jupiter stop growing so much earlier when it is in a more favourable spot through having denser gas? The obvious answer is Jupiter ran out of gas to accrete much sooner, and it would do that through the loss of the accretion disk. Stars blow away their accretion disks some time between 1 and 30 My after the star essentially finishes accreting. The inevitable conclusion is that our star blew out its disk of gases in the earliest part of the range, hence all the planets in our system will be, on average, somewhat smaller than their counterparts around most other stars of comparable size. Planets around small stars may also be small simply because the system ran out of material.

Given that giants keep growing as long as gas keeps being supplied, we might expect many bigger planets throughout the Universe. There is one system, around the star HR 8799 which has four giants arrayed in a similar pattern to ours, albeit the distances are proportionately scaled up and the four planets are between five and nine times bigger than Jupiter. The main reason we know about them is because they are further from the star and so much larger, hence we an see them. It is also because we do not observe then from reflected light. They are very young planets, and are yellow-white hot from gravitational accretion energy. Thus we can see how planets can get very big: they just have to keep growing, and there are planets that are up to 18 times bigger than Jupiter. If they were bigger, we would probably call them brown dwarfs, i.e. failed stars.

There are some planets that have highly elliptical orbits, so how did that situation arise? As planets grow, they get gravitationally stronger, and if they keep growing, eventually they start tugging on other planets. If they can keep this up, the orbits get more and more elliptical until eventually they start orbiting very close to each other. They do not need to collide, but if they are big enough and come close enough they exchange energy, in which case one gets thrown outwards, possibly completely out of its solar system, and one gets thrown inwards, usually with a highly elliptical orbit. There are a number of systems where planets have elliptical orbits, and it may be that most do, and if they do, they will exchange energy gravitationally with anything else they come close to. This may lead to a sort of gravitational billiards, where the system gets progressively smaller, and of course rocky planets, being smaller are more likely to get thrown out of the system, or to the outer regions, or into the star.

Planets being thrown into the star may seem excessive, nevertheless in the last week it was announced that a relatively new star, RW Aur A, over the preceding year had a 30 fold increase in the amount of iron in its spectrum. The spectrum of a star comes from whatever is on its surface, so the assumption is that something containing a lot of iron, which would be something the size of a reasonably sized asteroid at least, fell into the star. That means something else knocked it out of its orbit, and usually that means the something else was big.

If the orbit is sufficiently elliptical to bring it very close to the star one of two things happen. The first is it has its orbit circularized close to the star by tidal interactions, and you get one of the so-called star-burners, where they can orbit their star in days, and their temperatures are hideously hot. Since their orbit is prograde, they continue to orbit, and now tidal interactions with the star will actually slowly push the planet further from the star, in the same way our moon is getting further from us. The alternative is that the orbit can flip, and become retrograde. The same thing happens as with the prograde planets, except that now tidal interactions lead to the planet slowly falling into the star.

The relevance of all this is to the question, how common is life in the Universe? If we want a rocky planet in a circular orbit in the habitable zone, then we can eliminate all systems with giants on highly elliptical orbits, or in systems with star burners. However, there is a further possibility that is not advantageous to life. Suppose there are rocky planets formed but the star has yet to elimiinate its accretion disk. The rocky planet will also keep growing and in principle could also become a giant. This could be the reason why some systems have Neptune-sized planets or “superEarths” in the habitable zone. They probably do not have life, so now we have to limit the number of possible star systems to those that eliminate their accretion disk very early. That probably elimimates about 90% of them. Life on a planet like ours might be rarer than some like to think.