lucaspa

I've always thought the "thing" that layed the first chicken egg was not *quite* a chicken itself, therefore the egg came first. Maybe not always, but before this article came out in May, at least.

This would work if there was a clear demarcation in evolution. But there isn't. What this is saying is that, in a transition of 1,000 generations from the species before chicken to chicken, we can know that at generation 800 it is definitely species chicken.

But you can't do that. The beginning of the sequence and the end of the sequence during speciation are clear. But there is no magic line that you can draw in the middle to say this is the generation that you have the first chicken.

" In an evolutionary continuum, change occurs more or less gradually through time. At the early and late ends of such change, everyone agrees that different names are justified, but when one form slowly transforms into another without break, the point where the change of name is to be applied is a completely arbitrary matter imposed by the namers for their convenience only - it is not something compelled by the data." C. Loring Bruce, "Humans in time and space." In Scientists Confront Creationism, edited by LR Godfrey, 1983, pp. 254-255.

Amazon has this "general physics" bestseller list that has things like Brief History of Time' date=' and Brian Greene Elegant Universe etc. And Kaku books etc.

 

I just checked it out around 6 PM pacific today Wednesday 30 August and

 

SMOLIN WAS NUMBER ONE[/quote']

 

This is good news because ...

I am sad to see that this thread is starting to get a bit silly. A lot of arguing is going on about matters that are not relevent to the earlier theme. For example : some of the comments about fossils are just plain ridiculous. It is widely accepted among professional palaeontologists that the reason for minimal fossils before 600 million years ago is lack of hard body parts. Some of the other arguments on this are based on local examples without wide or general application.

Your argument on the presence of alien artifacts rests on the assumption that the geological record is complete. That simply is not true. We don't have a complete fossil record for every species on the planet. Why? Partly because the geological record is not complete.

I used pre-Cambrian only to show that we have samples from that period from a very limited geographical area. That applies to every time period in earth's history you care to name. The local examples are just that: examples of a general application. If the aliens had a camp at Milwaukee, we would see artifacts there only if the camp was in a very limited time scale -- the Mississippian. All other time periods are not at the surface. This applies to EVERY square foot of the earth.

Again, why no fossils showing an evolutionary history of bats? Because bats don't have an evolutionary history? That would be the conclusion based on your argument: we should have found fossils of bat precursor species. That we have not found those fossils means there were no bat precursor species. See the similarity to your argument: we have not found artifacts or fossils of alien visitors, therefore there were no alien visitors.

If aliens had once occupied Earth, it is possible they 'camped overnight' and left no markers. If so, why not a second race, that colonised? Such an occurrence would have left billions of hard remains that would be likely to form fossils. How many coke bottles alone are thrown away each year? To suggest aliens came here and left no traces is ridiculous.

You are using "occupied" and "colonized", meaning, in your mind, aliens occupying the entire livable surface of the planet. Even today, look at all the areas that have no coke bottles. All of Antartica, for instance. So, come back 3 billion years from now and the only area of the earth's suface to have rocks dating from now is where Antarctica once was. Would we find evidence of our civilization? No.

Also, you have ignored the degradation of coke bottles. It doesn't matter how many are thrown away if they all are ground to dust, does it?

Lucaspa mentions corals and koalas. Both have means of dispersal. Look it up. Admittedly koalas method is slow, and inefficient, and not well adapted to Australia after the impact of humans.

It's also very limited. That's the point. Eukalyptus is the only food for koalas. So koalas can't go where their food source can't. Corals can't go where the water is too deep or cold. So, dispersal does not = everywhere.

Population pressure causing geographic dispersal does NOT operate on large fractions of the species. It works by influencing very small numbers to get the hell out of there. It is always a small number of pioneers, while the vast majority stays home to face the consequences.

Haven't been paying attention to the immigration debate, have you? It's not "small numbers" of illegal immigrants we are looking at. Nor was it "small numbers" of Europeans that came to America in the late 1800s.

Even in Larry Niven's 'motie' books, the only case of a motie emigrating was an individual, while the bulk of moties stayed home and died. This is the way it works in real life.

That's not true. You shouldn't try to fib about the book. There were representatives of each subspecies on the ship -- in frozen sleep. There was only one conscious Motie -- a Mediator.

But the story highlights a problem I've been trying to get you to see: ECONOMICS. It took cooperation of most of the Motie planet to produce the mechanism of that emigration: launching lasers and the ship itself. They did so ONLY because all the Motie Masters hoped to get possession of the launching lasers to use for world conquest. And of the thousands and thousands of Cycles, they were only able to get that cooperation once.

The problem with slower than light colonization is the economics. So, increasing population pressure soaks up resources -- resources you need to build the colonization ship in the first place. And a colonization effort can't involve just 5-10 explorers. You need at least several hundreds to have a viable colony. Look at what happened at Plymouth. If they had not had a reinfusion of new colonists the 3rd year, the colony was doomed. Too few people to maintain it.

For exploration on earth, the economics were in reach. Wooden ships weren't cheap, but they weren't that expensive. Ships used for travel around Europe were adequate -- without modification -- to get across the ocean. That isn't the case with generation ships.

We can't afford to build an interstellar generation ship. We have the basic technology if we used the Orion drive. But no nation can afford it and, quite frankly, the taxpayers wouldn't cough up the money. And we have population pressure, don't we?

Lucaspa says Dyson swarm habitats are not generation ships. Quite the contrary actually. They are IDEAL generation ships. Just a couple of modifications.

LOL! I gave 2 ways that Dyson swarm habitats differ from generation ships and the technical difficulties in making them generation ships. You ignored both and say glibly "just a couple of modifications".

But you ignored my major point (you really shouldn't ignore points in a discussion): Once you have Dyson swarm habitats, you have no MOTIVE to go interstellar! In order to live on the habitats without overloading the biosphere, you have a means of controlling the population. So now you have much more living space than any possible habitable planet within your solar system and no population pressure. You have destroyed the motive you say is necessary for interstellar colonization.

Since all solar systems are going to be basically the same, there is no economic benefit. Remember, Europe explored and colonized the rest of the world because there were resources -- spices, gold, silver, timber, etc. -- that were either unavailable at home or scarce. There was trade between the home countries and the colonies. But there can be no interstellar trade at speeds of 0.2c or less. Too long for the voyage. So no population pressure and no economic motive.

That leaves political/cultural. Some of the initial colonies from Europe were formed for political/cultural reasons. That could still form a motive on Earth for interstellar colonization: some group that feels that its way of life is threatened and wants to go to another planet to preserve it. Raises its own private funds to build a generation ship and leaves.

BUT, if you have a Dyson swarm, that motive too disappears: just have your own Dyson ship or ships.

Lucaspa argues against the 6 billion year time frame. That is not my idea. It came from an item in New Scientist, based on astronomers findings. 10% of our galaxy consists of third generation stars 6 billion years old or more. That is not a matter open to debate. it is a scientifc finding.

Can you remember the article? I've been searching Google for it or references to it and can't find it. Are you sure it didn't say 10% were 6 billion years or younger?

Nor can I find an estimate of Population 1 stars by age. I do find that 20% of stars in the galaxy are Population 1, but not a breakdown by age. The oldest Population I stars seem to be about 10 billion years old, but their metal content is about 20% that of Sol. Stars with metal content = Sol's are less than 6 billion years old. http://www.ifa.hawaii.edu/~barnes/ast626_95/pcmw.html

I was trying to say that, if cost was a limiting factor on numbers of kids, we would expect the very rich to have more kids.

No. Because the wealthier you are the more the kids cost! You are thinking of kids as fixed cost per kid. But it turns out that isn't true. Instead, as family income increases, the cost of each kid increases. As I pointed out, poor families put 2 or more kids per bedroom, use hand-me-down clothes, do not send their kids to private schools, don't buy them cars, etc. All this reduces the per child cost of each kid.

BUT, as family income increases, the cost per child increases more than income: 1 child per bedroom, new clothes for each child, private schools cars, etc. All this means that each kid costs more for the rich than for the poor. So the rich can't afford more kids and practice birth control -- even before and in the absence of modern birth control. This seems counter-intuitive to you, but it is well-documented.

So, a technologically advanced species is going to have an economic reason to control population growth. When that happens, there goes your motivation for expansion.

Protiens and other chemical scan influence DNA. They can cause mutations or even cause the DNA to fold/pack differently. These can cause the DNA of the organism to express its self differently. I was not saying that the protiens changed the DNA "letters".

This isn't translation. Translation is converting the "letters" in DNA to amino acids in proteins. You don't go the other way: taking the amino acids in a protein and converting them to the "letters" (of 3 base codons) in DNA.

Again, what you are talking about is expression. Folding/packing is involved with whether the DNA can be transcribed to messenger RNA. If tightly packed, no transcription.

Now, when you speak of "mutation" you are talking a change in the sequence of bases. BUT, this isn't a reflection of the amino acids in the protein. Instead, it is a "random" change unrelated to the function of the gene.

If you switch a light on then off, it does not mean that the light was not on. The fact that the DNA was changed means a mutation took place, but then it wa repaired. Permanant mutations is another thing altogether. I think that here we are arguing over a dictionary definition rahter then the actual meaning in context so I will not persue this any further.

No, we are arguing over the meaning. Mutations are permanent. What you are talking about are errors that occur during the replication of DNA that are then corrected still during the replication process. Or the methylation and de-methylation of DNA.

But, in genetics, the meaning of "mutation" is a permanent change in the DNA. If the light was on and then off, then the light being "on" is a temporary situation, not a permanent one. This happens during gene expression. Often genes are expressed "transiently", that is, turned on and then off. But the sequence of bases in DNA that is a mutation stays that same sequence.

Some protiens can cause a mutated protien to change into the correct one. It can also go the otherway as in a Prion. These protines can be passed on from Mother to child as these protiens may exist in the egg cells.

Please cite the paper that changes a "mutated protein" into the correct one. As I say, I've never seen this.

As I said, "Whenever a cell devides". I did not specifically say germ cells. Mutations can arrise in cells that are not sperm or eggs, not just at conception.

This is where you are confusing cancer with the OP. The OP was clear that an individual was "born with" the mutation. This is mutation in the classic genetic and evolutionary sense. Not changes that occur in some cells in the adult during the transformation of a normal cell to a cancer cell.

Protiens and other chemical scan influence DNA. They can cause mutations or even cause the DNA to fold/pack differently. These can cause the DNA of the organism to express its self differently. I was not saying that the protiens changed the DNA "letters".

But, in order to "correct a mutation" changing the DNA letters is EXACTLY what has to happen. That's what a mutation is: a permanent change of the sequence of bases in DNA.

What you are talking about is expression of the gene. When is it expressed, how many mRNA copies are made, are both copies of the gene turned on, etc? This is no longer correction of mutations, but gene expression.

Apples and oranges.

If we look at the process of evolution' date=' which should apply to all life in our galaxy, a couple of relevent and probable trends appear.

1. Life, universally, should have a tendency to increase its population.

2. Life, universally, should have mechanisms to ensure geographical dispersal.[/quote']

 

"should have" is not a phrase you can use in science. As it happens, observation says that life does have the ability to increase population. However, observation also shows that many species do not have the mechanisms for geographical dispersal. Corals, for instance, are limited to warm and shallow water. Koala bears are limited to areas where there are eukalyptus trees.

 

If, however, large numbers of such aliens exist, it is seriously probable that a number of them are still driven by those evolutionary trends. These species would increase their numbers and would be expansionist. If they survive long term, they must develop a partial control, and only increase their numbers when conditions permit. I see this as a very likely outcome.

 

Let me get back to Edtharan's point: such expansion as you postulate will end up in war. After all, as number increase on the home planet, you postulate expansion to relieve population pressure.

 

Suppose you do ship off enough to temporarily relieve populatoin pressure (a questionable assumption at sublight speeds). The colony world has a growing population. Eventually they need to ship their population off, so they expand to a new world. And, of course, the home planet is continuing to ship excess population to new colonies. So now you have a sphere of colonized planets such that the inner planets CAN'T ship the population out fast enough past the edge of the sphere. Their population builds up until there is a huge war for the remaining resources or everyone starves. In any case, civilization and population collapses. Now you have a mostly empty planet.

 

So, the inner ring of planets need to ship off excess population. Which is going to be easier, a long way out past the outer ring and hope to find a habitable planet, or the much closer journey to the home planet that is now mostly empty? I say the home planet. Or perhaps the political organization is such to send a battlefleet to a newly settled colony of another planet -- you already know it is habitable.

 

Either way, what you now have is constant war between the planets in the sphere. Either fighting over colonizing the collapsed original home planet and first colonies, or fighting over the new colonies. And the whole civilization collapses and the expansion stops right there.

Edtharan.

Much of your reasoning on the population growth question is based on an "All or Nothing" logic. That is' date=' you suggest that EITHER

- The population growth is totally controlled, so that no expansion is needed

OR

- Population growth is uncontrolled and will expand until disastrous collapse.

 

Now, bear in mind that we are talking about intelligent and technologically advanced beings. An intermediate state can be achieved. If the aliens know thay have to control their numbers, but also have the desire to have more than two offspring per two parents, then a compromise condition can be organised. That is, population control is used with reluctance when needed. Population growth is eagerly embraced when possible. Such a state would render your reasoning invalid.[/quote']

 

No, such a state renders YOUR reasoning invalid. In order to have continuous interstellar expansion, numbers must be uncontrolled. If numbers CAN be controlled, then they will be at the point BEFORE the numbers are such that they have to send excess population off on generation ships.

 

Lucaspa said :

 

After all, you need to get the wealth necessary to build a generation ship. Not to mention all the R and D to get to the point where you can build a ship.

 

We have already got past this point in discussion. I was arguing about what is likely to ahppen AFTER the aliens had achieved a Dyson swarm. The habitat now already exists.

 

Dyson swarm habitats are NOT generation ships. They are habitats in stable orbit around their sun. And such a swarm provides a lot more living space than any new planet around another star. So, if a species has a Dyson swarm, it has no motivation to go colonizing other stars.

 

Generation ships pose different problems. Dyson swarm does not need large amounts of reaction mass -- a generation ship does. A Dyson swarm has cleared out inconvenient debris within the solar system such that they don't have to worry about collisions. A generation ship traveling at 0.1c has to worry about collisions. Even a dust particle at that speed would do enormous harm. So either the ship has to be very massively armored (with an increase in reaction mass needed) or have some way of deflecting interstellar pebbles and dust.

 

And don't forget the wealth necessary to support them. As individuals get wealthier, kids cost more. So, the cost of children is such that a couple can only afford two, if they are to raise them in such that they have a chance to do well and reproduce.

 

This is somewhat unrealistic. You only need to look around you. People do not always decide on numbers of kids by careful logical reasoning. The final numbers are likely to be the result of emotions, not logic. Your faulty logic implies that very wealthy people will have more children. In fact, on average, poor people have more children.

 

Now I know you aren't reading the posts correctly. Look again at what I wrote. I said wealthy individuals have fewer children. Wealth itself is a form of birth control. Why? Because wealthy people can only afford a few children -- each child costs more. Instead of 2 or more kids per room, each kid gets his/her own room, own clothes (not hand-me-downs), own car, private schools, etc. That adds a lot to the cost of each child.

 

Studies done in cultures without birth control still shows an inverse relationship between wealth and number of children. Increase wealth, decrease the number of kids. You said as much.

 

So, in our discussion, you posit an alien species technologically advanced enough to build generation ships. Then you also postulate that such a species would have to do interstellar colonization because of population pressure. But those 2 things are contradictory. Technological advancement means increased wealth. Increased wealth means decreased birth rate. Decreased birth rate means no population pressure. And there goes your motive for interstellar travel.

 

Also, remember that, if you have a generation ship traveling at only 0.1c, then inhabitants of the ship MUST have birth control. So that means the species has birth control at home too. As you noted, access to birth control means drastically decreased birth rates. And there goes your motivation for interstellar travel.

 

The only way you can have population pressure is if there is NO WAY to control birth rate. Like the Moties in Mote in God's Eye. But if that situation prevails, then you have a boom and bust cycle where civilization collapses before it is able to accumulate the spare wealth to build a generation ship.

 

 

However, when I talk about 6 to 8 billion year old stars, I am talking only about third generation stellar systems. Roughly 10% of the Milky Way galaxy is third generation stars at least 6 billion years old.

 

Our sun is 3rd generation. It is only 4.7 billion years old. So, any stars older than 6 billion years are second generation stars and are still deficient in heavy elements. I question your assumption of a 2 billion year head start.

 

There could still be a 60 million year head start. After all, if the asteroid had not hit 65 million years ago, it is possible that one of the dino species would have evolved sentience and tool use. But not a 2 billion year head start.

 

There is always some population loss, and this is generally quite large. If a population stays at a relatively stable level, it is due to the unbiquitous tendency for the population to grow. In other words, more than two births per pair of parents, to permit compensation for the high death rate. As soon as a species develops to the point where it reduces its own mortality, this drives population growth, which is thus the 'natural' state.

 

Population growth is NOT the "natural" state. Population stability is the "natural" state, as scarce resources limit the population. Yes, more individuals are born than the environment can support. But the environment always eliminates the surplus such that population stays constant.

 

In order to "reduce its own mortality", resources have to increase faster than population. This can happen as a population moves into a new geographical area. Humans have increased resources by technology -- particularly farming and herding. But even here there is an ultimate limit due to the finite space on a planet.

 

BUT, as we have seen, if a species is intelligent to have that technology, then we have 2 new factors to limit population growth: economics and technology in the form of birth control.

 

In order to have continuous population growth, you have to postulate a species that cannot choose to limit growth -- whose biology is so weird that they absolutely MUST reproduce. This contradicts your postulate at the beginning of this post: "That is, population control is used with reluctance when needed. Population growth is eagerly embraced when possible."

 

It is true that the numbers of fossils reduce dramatically pre-Cambrian (older than 600 million years). But this is not due to the age of the rocks so much as due to the fact that hard structures were uncommon in living things at that early stage.

 

You missed the point. As you noted, we only have limited areas where pre-Cambrian rock is available. You mention the Canada rocks of 3.8 billion years ago. Where else do we have 3.8 billion year old rock at the surface? NOWHERE. Where else do we have 3.5 billion year old rock at the surface? NOWHERE. So this is why you only have evidence from 2 limited locations.

 

So, what if your coke bottle from colonization were in Michigan? Here is a map of the Michigan area: http://www.earthscape.org/t2/scr01/scr01ac.html

Notice how little of the region is pre-Cambrian. If the aliens were at the site of present-day Milwaukee, no pre-Cambrian rock is exposed: the bottle is still buried.

 

What's worse, much of the rock that is exposed is metamorphic or igneous. The processes that formed this rock would destroy any artifacts that might have been present. This is from Alabama: "The few rocks of that age that do exist have been highly altered through metamorphism and contain no recognizable fossils. " http://www.paleoportal.org/time_space/state.php?name=Alabama

 

See what the site says about Mesozoic rocks: "Most Mesozoic rocks in Alabama are deeply buried beneath younger sediments"

 

Of course, creationist sources have often claimed to have technological artifacts dating long before the evolution of humans. They use the artifacts as evidence against evolution. However, you could easily view them are remaining artifacts of alien visitation or colonization. Why don't you?

 

Any alien species living on Earth would have left hard structures. Thus, they would have left traces.

 

Bats have hard structures -- bones. So where are the fossil bats? Or the fossil woodpeckers? Or many other fossils of vertebrates? They didn't leave traces. WHY?

 

It's not a matter of hard parts. You ignored the points and tried to change it. It's a matter of just how little of the geological record is at the surface for us to find. That's the problem. Your premise is flawed. There have been so many species and groups of species on the planet. Most of them have not left traces. And it's not because they weren't here.

1. Is it valid to continue the pseudo meson scale in the same manner as the main sequence? If so' date=' why?[/b']

 

Using mass quantities published by The Particle Data Group, my method to find the scale indicates that this is the case (the same method is used for finding both scales).

I'm sorry, but you didn't address the question. All you said was that you did the sequence. You didn't tell my why it is valid to do so. The results don't justify the method.

2. What "waves found in cosmology"?

 

Distances between bodies of a given system are shown to be fractions in the mathematical order of main sequence fractions indicating that cosmic body systems have the same basic wave structure as particles and atoms. Any difference is shown to be a question of the 'nucleus and shell' arrangement.

The "waves" in particles and atoms are probability waves, not distance waves. They are more like crime "waves" than water waves. What you seem to be trying to say is that the fractions of distances between the planets and the sun are going to be the same as the fractions of distances between the various electron shells and the nucleus. Am I stating your position accurately? If not, then please correct me.

3. Is the "shell" you refer to the electron shell surrounding the nucleus of the atom?

 

All structures have a nucleus and a shell, even the vacuum field of the single single elementary particle can be divided into two (straight line and curve line sections of a graph of a force field). Three particle composites (baryons) are considered to have one nuclear particle and two shell particles. Mesons do not have a nuclear particle hence there are no stable charged mesons.

It seems that you have just defined everything as having nucleus and shell. I would not call the quarks that make up baryons to be a "nucleus" and "shell". The terms "nucleus" means a central locationa and "shell" a toroid or spheroid around that nucleus. Also, a straight line and a curve line is not a "nucleus" and "shell" in the same way you have an electron shell surrounding the nucleus of an atom.

Just defining things the way you like isn't looking for what the universe really is, it's trying to force your ideas on the universe. Not science.

4. Total force to do what? What's the source of this total force?

 

All single particle states have the same Linear force acting on the radius. it is the manner in which I found this figure that lead me to use the term 'Total force'; this has caused some confussion for which I apologise.

 

Some modern astro-physicists already believe the universal structure consists of 'bubbles within bubbles'. I simply show that each bubble has the same internal fractional wave structure.

You have taken this out of context. Bubble Universe (see Andre Linde) is a hypothesis that states that the universe may consist of many isolated "bubbles". See below. Bubble Universe has has not been tested: we don't know if there are such bubbles. Therefore it is impossible for you to show that "each bubble has the same internal fractional wave structure." You can't show characteristics of an entity that you haven't shown exists. For instance you can't show that the invisible unicorn has wings.

The proposal is that the Standard model should be expanded to include the 'bubble' model.

Considering that you don't seem to have any idea what Bubble Universe says, I really have severe doubts about this.

http://www.astro.lsa.umich.edu/users/hughes/ucourses/120f97/inf.html

"Alan Guth and Andre Linde independently proposed in 1981-2 that the Big Bang begins in a hot dense state, but as it cools through the so- called Grand Unification Theory (GUT) transition energy at 10^15 GeV and 10^-35 seconds, it gets caught in a false vacuum state. This causes the universe to exponentially grow in size in what is called a quasi-de Sitter state. The expansion ceases once the universe enters its true vacuum phase, with a release of energy that appears as a fireball phase of particle and radiation creation by 10^-33 seconds after the Big Bang. The expansion then resumes with the Friedmann expansion phase which it is now continuing to undergo, but at a greatly reduced speed. The transition occurs by the nucleation of true vacuum bubbles within the expanding matrix of the de Sitter false vacuum phase. These bubbles either merge together to form the present day uniformity of the universe (Old Inflation), or remain as separate domains that grow to sizes billions of times larger than our observable universe (New Inflation). The supermassive, scalar Higgs field is identified as the culprit whose phase transition initiates Inflation. "

I think the Dyson Swarm (a better and more accurate term than bubble or sphere) would still suffer from instability as individual statlites effect each other.

There are 2 separate ideas: a Dyson Swarm and a Dyson Sphere or shell. A Dyson Sphere is a hollow sphere at earths orbit, with the inner habitable side facing the sun. You can calculate the amount of living space this provides and it is basically larger than billions of habitable planets.

This is NOT Dyson's original concept. The Dyson Swarm is closer to that.

http://en.wikipedia.org/wiki/Dyson_sphere

Of course with smaller objects it would be easier to addjust their positions. Therefore it would be posible to stabilise the swarm, but at a cost. The fuel to do so must come from somewhere.

 

Without using any physics breaking technology (sci-fi stuff), we know of no way that a swarm could maintain its positions for long periods of time wihtout having to loose mass (ie rocket engines or ion engines) to do so.

Not really. What you get is a series of habitats in rings at slightly different angles to the ecliptic and slightly different distances from the sun. See the article. Thus, you don't have interference from one ring to another, but the total effect is to completely block the light from the sun, as well as have an enormous amount of living space.

Sayonara.

In earlier postings I have suggested two reasons why a species will move away from its sun.

1. The explorer instinct. If it is Earth humans' date=' then we know from observation that this affects a minority of people, but very strongly. There would always be a certain number of people who would fight for the chance to go elsewhere. Some alien species would be similar.[/quote']

 

But you need many more than a small minority. After all, you need to get the wealth necessary to build a generation ship. Not to mention all the R and D to get to the point where you can build a ship. It's a lot of wealth. Humans have a very difficult time getting the wealth together just to get back to the moon.

 

2. Population pressure. If the species involved continues to grow in number (and evolutionary principles suggests that a desire for more than 2 offspring would be a selective advantage), then even a Dyson swarm would eventually be unable to support all of them.

 

Not always. Remember, it is number of surviving offspring. With modern technology, you only need 2 (or 1) to be fairly sure that one grows to adulthood and has kids.

 

And don't forget the wealth necessary to support them. As individuals get wealthier, kids cost more. So, the cost of children is such that a couple can only afford two, if they are to raise them in such that they have a chance to do well and reproduce.

 

And again, I have to say, that if the number of alien species is very large, then at least one will act in just that way.

 

No, that's your assertion. You are saying that, by chance, one will act this way. But we are saying that there are non-chance factors that would squelch the behavior.

 

Edtharan, I think you are right in your suggestion that reaction mass would be needed. Correct me if I am wrong, but I cannot see how a solar sail could be used to move inwards towards the sun, which would, in theory, be needed as often as a move outwards.

 

You use your speed to move toward the sun and use the light from the target sun to brake. You may also be able to tack a solar sail, like you tack a sailboat to move into the wind.

I must be very poor at explaining things' date=' since there seems to be a lot of misunderstanding. Let me try again.

 

First, my whole point is that there cannot be, or have been, more than a few technologically advanced alien species in our galaxy. If the total number is less than (say) 100, over the past 2 billion years, then my logic breaks down. However, if the number is large, then probability requires certain outcomes. For example, some of the species will have expanding populations.[/quote']

 

1. We understand quite well. We are just refuting your logic and conclusions.

 

2. We are arguing that it is not inevitable that any of the species will have expanding populations -- at least expanding so that they do interstellar travel at less than lightspeed.

 

For one thing, in order to do interstellar travel at 0.1c, they must have a means of controlling population growth. Which means no expaning population.

 

Second, the rules of economics say that increasing wealth -- which is produced by a technologically advanced civilization -- results in control of population growth.

 

Conclusion: your assertion and assumption that there must be a species with population growth such that it feels compelled to do interstellar travel is invalid.

 

Second : arguing by analogy with Earth life. These intelligences must be enormously varied. On earth we have apes, cetaceans, parrots and crows, cephalopods, carnivores, and elephants - all with quite substantial levels of intelligence. They vary enormously in body form. It seems logical to assume equal variability in psychology. This variability must apply to alien intelligences also. This means, if there are very large numbers of such species, we cannot argue on the basis of psychology.

 

But we can argue on the basis of economics and physics. Those are the same everywhere.

 

Some of the species must, by probability, have the mental attributes for successful expansion. Some will have the mental attributes leading to explosive population growth. Some will have both.

 

So? They are still up against the same economic and physical constraints and, if they don't change, they will die.

 

For instance, if they can't control their population growth, then they will exhaust the resources of their planet before they can even get into space. That may yet happen to humans. Then they go back to a perpetual state of savagery as they fight for scarce resources. Building a generation ship is a huge investment of resources. It requires a lot of spare wealth.

 

See the book The Mote in God's Eye for the consequences of the inability to control population growth and being limited to lightspeed.

 

Third. Travel through the galaxy. According to my Scientific American article, humans will have the ability to travel between stellar systems within 1000 years, at speeds of up to 0.1 to 0.2 c. Since star systems have existed in the Milky Way for 6 to 8 billion years, and IF large numbers of aliens exist and have existed, then the same probability argument strongly suggests that aliens with exploding populations, with the ability to successfully expand would have spread through the galaxy a long time ago.

 

Actually, stars have existed in the Milky way for 10 billion years. But there is another hidden assumption here: the elements available to planets of first generation stars. Our ability is predicated on heavy metals. First generation stars and star systems are metal poor. So they don't have the basic material necessary to make the equipment necessary.

 

Four. Yes, I believe the logical place for most of this population will be in space cities. However, if the population pressure is high enough, they will also colonise every planet they can find.

 

Well, we are arguing that "if". You haven't addressed those arguments against your "if".

 

Remember that, on Earth, the tendency for every successful species is population growth. Very basic and important principles of biological evolution drive every successful species to gain the ability and tendency to grow its population.

 

This is so completely wrong! Successful species are actually in balance with numbers. Population remains constant. It is the competition among the individuals for scarce resources that is the basis for natural selection. Why are there scarce resources? Because more are born than the environment can support. In cases where population is not controlled -- like some deer populations on islands where there are no predators -- then there is a boom and bust cycle. Population rapidly increases until food is exhausted, then 99% of the population starves. And the cycle starts again.

 

Humans are atypical. We have been able, thru technology, to expand resources faster than population. But you notice that this isn't the case everywhere, and lots of people starve today in various parts of the world.

 

So, you are basing your argument on false premises.

 

Five. Leaving remains. Look at what we already have as fossils. Stromatolite fossils (cyanobacteria) from 3.5 billion years ago. Jellyfish leaving impressions in mud from 700 million years ago. Billions of shells, and bones from all ages of life. Almost anything can form a long lived fossil if conditions are right (such as falling in soft mud).

 

Have you read or heard about all the gaps in the fossil record? Yes, we do have fossils from 3.8 billion years ago -- in one small location. Do you think that was the ONLY place life was on earth? But we don't have any fossils from anywhere else, do we?

 

Do we anything like a complete evolutionary sequence from species to species for ALL species on the planet? NO! We have such a sequence for a few of the billions of species on the planet -- more than enough to show evolution happened and to falsify creationism. But not nearly enough to say that the fossil record is anywhere complete.

 

I find it impossible to believe that any alien species could live on Earth and not leave traces. Where is our alien coke bottle?

 

Probably not successfully colonized. After all, if that happened, they'd still be here, wouldn't they? Of course, the colonization could have been unsuccessful. Like so many human colonies down thru the ages. In that case, the coke bottle is buried in sediments under the sea, or under the land, or has degraded. After all, if it fell into a river, grinding against rocks would eventually (in a few thousand years) reduce the bottle to glass dust. And how would we find it?

 

Or even if it was buried, what happens to the bottle when it is compressed as the sediments form sedimentary rock? Fossils are there because they are rock themselves. But a bottle isn't. Does it break? If so, then as the sediments compress, you get that grinding action again.

 

Lots of reasons we haven't found a coke bottle, or anything else, from a visit or failed colony that happened millions of years ago. Many are the same reasons we haven't found fossils of primitive bats.

 

I gave you the reasons before. You ignore them.

 

All you can show is that earth has not been successfully colonized such that the alien species is still here.

 

All this logic falls apart if the number of aliens is small. However, if the number is massive, then at least one species must have come to Earth, colonised, and left traces.

The expression[/i'] of a mutation is a failure of the repair systems. A mutation is not. Cell in your body suffer mutations each time it replicates, but most these mutations are repaired (the ones that don't might cause the cell to die or turn cancerous.)

If they are repaired, they are not "mutations" as we are using the term. "mutation

1. A change in form, quality or some other characteristic.

2. (Science: genetics) A permanent transmissible change in the genetic material, usually in a single gene. Also, an individual exhibiting such a change." http://www.biology-online.org/dictionary/Mutations

See? An error that is repaired is not a "permanent" change, is it? It was temporary before it was repaired.

There are methods that a cell can use to switch off certain sections of DNA. This is why you can have different cells form from the single egg cell. A cell can detect damage like mutation and can use this to either attempt repair, or cause its self to die (so as to stop a cancer forming). If this fails it can lead to cancer.

Apples and oranges. Yes, cells in multicellular organisms do turn off some genes and turn on others so that cells can specialize. Since I work with adult stem cells, I am familiar with that literature. However, we aren't speaking of those mechanisms. We are speaking of turning off a mutated protein. This doesn't happen. If the type I collage gene -- a necessary and specific gene for some tissues such as tendon, ligament, and bone -- is mutated, the body doesn't have the ability to turn it off. The individual has to live with the result.

Or take the hemoglobin gene -- specific for red blood cells. If it is mutated to the sickle cell form, the individual has to live with that result. A recent case in Sweden illustrates that. The individual exhibited the symptoms of sickle cell anemia, but no one considered it because, well, this was Sweden. Nordics didn't carry the sickle cell allele. But this was a brand new mutation and the individual did indeed have sickle cell.

Remember every cell has another copy of that chromosome that it can use as a template to detect some errors and other cells can send protines, rna and other chemicls through to a nearby cell that can also be used in this fassion (just compareing protiens can be enough - eg if two cells have differnet protien expressions that can both die as one of them is in error and there are other cells can replace them).

1. Can you quote me any paper where the cell uses one chromosome to detect errors on the other? I don't know of any. As I say, type II osteogenesis imperfecta is much milder than type I because there is one good copy on one chromosome. If your hypothesis were correct, this type of OI would not exist, because the good copy would be used to correct the bad one.

2. Can you quote a paper where RNA and/or proteins are passed from cell to cell in order to correct defects in DNA?

3. Again, you are talking apples and oranges. Remember, mutations we are talking about are not in cells in the adult, but in the sex cells. That is in either the sperm or the ovum. When they get together, they form the fertilized ovum -- the cell that is going to give rise to ALL the cells in the body. So ALL the cells are going to have the mutation. There is are no "other cells to replace them".

Each cell ingerits not only the DNA from it parents, but als some of the protines and other chemicals too. This means it does have some point of reference as to what protiens and chemicals should be produced. So by this method it can detect mutations in its DNA.

Translation of DNA to protein goes only 1 way. It doesn't go from amino acid sequence in proteins to base sequence in DNA. Again, can you please cite some papers for this? I have never encountered mention of this phenomenon in my 30 years as a biochemist.

But there are so many methods that a cell can use to catch bad mutations and even attempt to repare them that not all bad mutations are expressed. So if all you are going on is expressed mutations, then you are only sampeling a small fraction of the mutations that occure.

As I read this, I think you are confused between what happens with cancer and mutations as they are used in evolution. Yes, mutations can happen in adult cells -- the somatic cells. And yes, in most cases the mutations cause an abnormal cell which either 1) undergoes apoptosis (programmed cell death) or 2) destruction by the immune system. The rare ones that do neither result in cancer.

HOWEVER, we are talking about mutations in the sex cells -- sperm or ovum. These are errors in copying DNA that are not corrected by the intrinsic repair mechanisms. Errors that are corrected are not mutations. Those repair mechanisms are VERY good, but they cannot be perfect. Such perfection would be a violation of the Second Law of Thermodynamics. So, in that case we have a permanent error that is going to be in ALL the cells of the new individual -- because all the cells came from the fertilized ovum. Many of those errors are bad enough that the embryo fails to develop -- that is the cause of most miscarriages. But the rest reside in the individual and make that individual slightly different from all the other individuals in that generation.

For a genome the size of the human genome, there will be about 2 mutations per genome. That is, you have 2 mutations. So do I. So does everyone else on the planet.

lucaspa

 

1. I noticed you made no attempt to answer the questions I posed. Since these refer only to your theory or claims made by you' date=' I figured you could at least explain them. I'm sorry you didn't.[/b']

 

Sorry but I get into serious trouble with the administrators if I quote my own (unpublished) article. However, I have today received confirmation from a journal editor that my article has been out to reviewers; so I will soon know if I have written anything of value. Meanwhile I must be patient.

 

Will try and get the book, thanks for the advice.

 

regards

elas

I didn't ask you to quote anything. Just answer in your own words. The questions were general, not specific. Here they are again.

1. Is it valid to continue the pseudo meson scale in the same manner as the main sequence? If so, why?

2. What "waves found in cosmology"?

3. Is the "shell" you refer to the electron shell surrounding the nucleus of the atom?

4. Total force to do what? What's the source of this total force?

Population growth of even one species would be enough to drive them to colonise every system thay can.

Why do you postulate the absolute of population growth?

Several studies of humans have shown that, in the absence of modern birth control, birth rate decreases as wealth increases. There are sound economic reasons for this: each child demands more resources as wealth goes up. Therefore a family can support fewer children in the style to which they have become accustomed. So they have fewer kids, even if this means abstinence.

If they were here 1 to 2 billion years before human evolution, there would be no logical reason to bother.

If you are going to go back 1 to 2 billion years, then you must address the arguments I have put forward for why there are no traces. Starting with what is going to be left after a billion years, and will it even be on the surface. Now, if they actually colonize the planet like you said, then where are they? They'd still be here as the dominant species, wouldn't they?

You might want to read the Drako's Tavern series of stories by Larry Niven. In it there used to be a technological civilization on earth 2 billion years ago -- by indigenous anaerobic organisms. The rise of green plants killed the civilization (and species) by oxygen poisoning. What would be left?

My view is simple. Bearing in mind that aliens have had 2 billion years to colonise/explore Earth before humans evolved, and there is no trace of such activity, then it is likely that the total number of such technologically advanced species is very small. Not necessarily zero. Just a small number.

But our contention is that your view has flawed assumptions. If your assumptions are flawed, then so is "your view", which is the conclusion from the assumptions.

Again, "there is no trace of such activity" only counts as evidence if we can really find the traces. There are lots of reasons besides the non-visitation that can account for not having found traces. Your "view" needs to consider them.

Whew!

After all those postings' date=' where do I begin?

Perhaps just a comment or two.

 

First, I was probably wrong at one point in talking of spaceships. It is likely that expansion will be via what we are now calling space cities. Generations in transit matter little for such a structure and such a society.[/quote']

 

"City" implies an open space. This isn't going to be true for interstellar travel. You MUST have an enclosed space. Expansion to the "suburbs" is impossible. So is building taller buildings. There is finite space and resources. So yes, generations in transit time matter a great deal! How do you manufacture spares? Remember, no industrial base because there is no room or place to mine new minerals. No shipping of food in from the countryside to THIS city. You grow everything onboard. Also, what do you use for reaction mass? Do you carry it all? Do you use Bussard ramjets? But those only work at near lightspeed; I'm not sure they work at 0.1c. So, do you use the Orion drive? Lightsail? If the latter, trip time is MUCH longer because acceleration is much lower.

 

Second, it does not matter too much for space cities, when arriving at another stellar system, whether there are suitable planets or not. They will be able to mine space detritis. There is an enormous amount in our own solar system left over from planet formation, and that is probably true for most stellar systems. ... It appears beyond belief to me that, if they were here, some time in the past 2 billion years, that they left no traces. Look at the enormous quantity of junk humans have produced.

 

Did you notice that your first point contradicts your second? You say that the spacefaring species living in generation ships has no need to visit habitable planets! So why would there be artifacts on earth if we were visited by a species living in generation ships? They mined the asteroid belt, took some gases from the outer planets, and left. Maybe they stopped off for a little hunting on earth -- hunting T. rex and sauropods would have been exciting, but why try to grow food when your hydoponics gardens are sufficient?

 

As to aliens doing the same and getting to Earth. I have to keep harping back on the enormous numbers involved. With two billion years to do it, and (according to Sagan and Drake) a million species involved, how is it possible that not one alien species ever got here? Even the tiniest fraction of that as alien junk would have marked their presense indelibly.

 

You keep ignoring the points I brought up concerning why such "junk" would not have been found. You need to address those points in a speculative discussion instead of ignoring them. If they just made a stopover, we postulate one or more temporary camps. How large an area does that cover? A square mile per camp? Kinda large, but let's go with that. And they do a 100 camps in different parts of the world -- they are exploring. That's a total of 100 square miles. How many total square miles on the earth? 196,940,400 square miles. So, we are talking a maximum of 1/1,969,404 or about 1 in 2 million. Bad odds for finding the camps. True, land surface is only 30%, but you have to remember that what was land in the past might be sea now. So we can't rule out what is presently sea. For instance, the Black Sea was flooded only about 12,000 years ago. If one of the camps was in the middle of what is today the Black Sea, we wouldn't see it, would we?

 

Now, if the visits were tens of millions of years ago, the camps are buried by sediment or they are eroded. You keep saying that junk would persist. Would it? How long does plastic last? It's pretty nondegradable, but even it has its limits. http://www.azom.com/details.asp?ArticleID=1655#_Plastics,_Not_as

 

Absence of evidence as evidence of absence works only when you can search all the places where evidence might be found. We aren't even close to that in this case.

 

However, I would like to see you address Sayonara's and my economic and birth rate arguments against interstellar exploration in the absence of an FTL drive. You ignore them but never say why they aren't valid.

There is no such thing as negative evolution. We are always evolving toward some set of selection criteria, never away.

Good point. You are addressing the judgement call of the OP. The poster has the idea that some traits are absolutely "good" -- such as 20/20 eyesight -- and some traits are absolutely "bad" -- such as nearsightedness. Since we compensate for nearsightedness with glasses, the OP feels that this "bad" trait is accumulating in the population.

Since the physcial "fitness" of a human is no longer critical to its survival, this is not being selected-for anymore (or much, at least).

 

What we are doing is moving from physical evolution to social evolution. It is social traits that now determine who breeds and who does not.

A couple of years ago there was a study showing that the increase in height in humans was due to sexual selection: people pick tall mates.

In isolated populations such as the Andean and Himalayan highlanders, there is still selection for physical characteristics. Several studies have shown that each population is evolving (different) adaptations to living at high altitudes.

Can you quote any studies about social traits and mating or is this your gut feeling?

Even if more mutations were detrimental than beificial, this doe not mean that they will lower the fitness of an organism. In sexual selection each organism gets 2 coppies of their genome, each from a different parent. Any bad mutations on one can be canceled out by the other. Also DNA has many repair mechanisms that can detect and either repair the mutation, or switch it off so it doesn't cause a problem.

Let me take these in reverse order:

1. Mutations are a mistake in copying DNA. To have a mutation means that the repair mechanisms have failed. Nor does DNA have the ability to switch off a mutation -- the transcription factors can't tell that a particular gene has been mutated. The organism has to live with the results.

2. It is true that, in some cases, only one copy of a gene is expressed. But again, as far as I know, DNA doesn't have the ability to tell which is which. In the cases where the effect of a detrimental mutation is reduced, it is because both copies of the gene are expressed, and the number of "good" proteins helps mitigate the effects of the proteins produced by the detrimental mutation. Osteogenesis imperfecta is one example of this. Get 2 bad copies and the genetic disease is very bad. Get one bad copy and the severity is much, much less.

3. Detrimental mutations do lower the fitness of an individual. This does not mean an effect on the population, because the individuals unlucky enough to get the detrimental mutation are weeded from the population and the frequency (number of individuals with that mutation) drops. Eventually, the frequency will go to 0. That's the selection part of natural selection. On the other side, a beneficial mutation will eventually reach a frequency of 1 -- every individual will have it. This is what biologists mean when they say a trait is "fixed".

So the fact that there are many more bad mutations, than good mutations does not mean that the organism's gene pool will nessisarily become corrupted.

But the data is not that there are more bad mutations than good. Rather, that there are vastly more neutral or beneficial mutations than outright bad ones. However the point is good: selection works to eliminate bad mutations and preserves good ones.

The point of the OP, however, was that humans were not subject to selection anymore. Thus, "detrimental" mutations were not being eliminated by selection.

lucaspa

 

Then submit your paper to Journal of Theoretical Physics.

 

But I feel your point is the right one' date=' and I will come back when I have something to say,

regards to all

elas[/quote']

 

OK. Two things in case you check in:

 

1. I noticed you made no attempt to answer the questions I posed. Since these refer only to your theory or claims made by you, I figured you could at least explain them. I'm sorry you didn't.

 

2. Did you read the book Severian suggested to me? Peskin & Schroder

I don't see you quoting it. Maybe it would answer some of your questions about explanations within QFT.

Incidentally, another reason I think intelligent life is very rare is because it's rare here on Earth. There are several species on the verge[/i'] of complex communication and technology, but there is really only one, out of all the life on Earth, that is actually capable of them. Us. There's also no evidence that there was ever one before us. Although that doesn't prove anything, it should be noted that WE will certainly leave lots of traces for a LONG time. For one thing, all the oil is gone....

See that you are equating technology with intelligence? Not the same thing. A species can be very intelligent (perhaps as whales are) but lack the necessary traits to make technology. In this case, whales lack hands and living in water handicaps them in building technology. Difficult to refine metals underwater.

Also, 30,000 years ago there were three (at least) species of Homo on the planet: H. neandertal, H. erectus, and H. sapiens. There may have been more but not have the skeletal features necessary to distinguish them from H. sapiens. For instance, Mungo man in Australia is skeletally modern, but has DNA as different from us as neandertals.

So, having only one species of Homo on the planet is unusual and recent (in evolutionary terms). It may be that one technological species will always supplant all the others. But then again ...

Oh well I read somewhere that more are detrimental then beneficial.

And where was that? Creationist literature often makes this claim, but the citations are studies done in the 1930s. This was done with massive amounts of x-rays on flies -- causing multiple mutations in the same individual. Also, only naked eye visible "mutations" were looked at. If you are going to massively change the developmental program of an animal, then you are most likely going to change it for the worse. But those studies were designed ONLY to show what was under genetic control, NOT to study the effect of mutations that occur in nature.

Wait a tick. How was that determined (from a paper, possibly?)? And more importantly, how many of these were neutral and how many beneficial? I would assume that the vast majority should be neutral and only a fraction beneficial.

PD Keightley and A Caballero, Genomic mutation rates for lifetime reproductive output and lifespan in Caenorhabditis elegans. Proc. Natl. Acad. Sci. USA 94: 3823-3827, 1997

This study documents the rate of deleterious mutations in the worm C. elegans. Because they are hermaphroditic, the authors were able to separate the worms and run parallel populations descended from a single individual. By maintaining independent sublines, the effect of selection could be minimized, and thus the deleterious mutations could be kept in the population. Lethal mutations are still lethal, but the experimental design allows accumulation of deleterious mutations (as well as neutral mutations) and then the effect on lifespan and production of viable offspring, both of which are measurements of fitness. The estimated deleterious mutation rate per haploid genome (the whole organism) was 0.0026, or 2.6 per thousand.

"Deleterious" refers to mutations that directly shorten lifespan or decrease the viability or number of offspring. "Beneficial" and "neutral" apply only to particular environments. There is no such thing as a universally beneficial trait. Every trait comes with costs as well as benefits. Change the environment and what was once beneficial is now detrimental.

Other population studies indicate that the vast majority of mutations are neutral in any particular environment.

Lucaspa said :

 

The distance between stars using lightspeed is such that birth control MUST be practiced most of the time. Such ships are going to be generational: several generations living and dying on the ship. So' date=' in order to undertake such a journey in the first place, they must have a brake on reproduction. Otherwise they couldn't maintain a stable population on the ship.[/i']

 

Sorry. This is faulty logic. The distance from here to Alpha Centauri is 4.3 light years. At 0.1 c, that journey would take 43 years.

IF Alpha Centauri has habitable planets. We don't know that. If you begin to extend the distance beyond Alpha Centauri (and particularly intergalactic), then you have many more than 2 generations. If population increases only 10% per generation, then you quickly run into troubles.

Either way, we cannot assume that our alien species will not grow dramatically in numbers after arriving at their destination. In fact, assuming numerous species competing, the species that increases fastest has a substantial competitive advantage.

Your assumptions are:

1. The species would want to colonize. Maybe not.

2. That population would increase dramatically. I doubt that. In a technological civilization, everyone wants the wealthy lifestyle associated with technology. That can't be maintained until the technological base is constructed. How long does it take to grow the food to feed the new numbers, mine the metals, refine them, manufacture the tools to make the tool to make the tools to make the factories to produce the technology?

3. That the death rate will be minimal. Look at the history of colonization of N. America by Europeans. Roanoake colony failed and the colonists died. Plymouth suffered 60% deaths the first winter. Both Plymouth and Jamestown survived only because there were additional colonists arriving from Europe. And that was on the same planet on which humans evolved! Imagine the potential problems for colonists evolved on a different planet, cut off from reinforcements, and facing all the hazards of a new environment.

The average distance between stars within our galaxy is, in fact, less than 4.3 light years.

That's misleading. Average includes the stars in the core -- and organic life can't live there because of the radiation. Out in the toroid where habitable planets exist, the average distance is more like 10 light years.

In fact, such a species is the one most likely to be involved in rapid expansion. Population pressure will pressure the explorer types to get out there.[/quote

 

Bad assumption. We have population pressure on earth and we are expansionist. Look at the exploration and colonization conducted by Europeans. Yet where is the construction of generation ships? We have the technology.

 

Instead, the economic and political cost is too high. Instead of spending resources to build such ships, we use the resources to feed the people on the planet and to increase wealth. Also, as wealth increases, birth rate drops. Any species as technologically advanced as you propose is going to have a means of birth control. After all, it must be used on generation ships. I don't see why an alien species would be exempt from economic principles.

 

Even IF there is colonization, how long before the colonists have populated the new world and are able to build their own generation ships to continue the process?

 

Humans are likely, in the next 50 years, to develop a 'space elevator' which can get us into space cheaply and in large numbers. Assuming our alien species has this technology, they will have no major brakes upon their ability to get into space cities, and from there to expand in all directions.

 

Even if we get into "space cities", (and I disagree with your "likely") what is the incentive to leave the solar system? If we can build habitats in space, then we can build them all over the solar system. Think of the massive amount of resources still within the solar system! Your population pressure disappears and we have no incentive to build generation ships.

 

And maybe that is the answer to "Where are they?" Once the level of technology is such that the species can build habitats on the other real estate within their solar system, there is no economic or population pressure to go to the stars if we are restricted to generation ships. Only if there is an FTL drive would colonization become attractive.

Isnt that egotistical

 

It may be possible that we are the most advanced civilization in our galaxy (or at least' date=' any other civilzations are a million or less years ahead).

 

How about inter-galactic travel?

statistically, there HAS to be intelligent life in the universe. If not in our galaxy, then perhaps in another. If they had a 1 billion yr head start then I'm sure they could make it intergalactically[/quote']

 

1. Instead of "intelligent", you need to say "technological" species. Chimps (and perhaps whales) are intelligent, but they are not technological.

 

2. Intergalactic travel below lightspeed is going to be technically and, more importantly, economically VERY, VERY, difficult. You need a ship that would last for a billion years, be generational, and can carry enough consumables for an intergalactic trip. No recycling is 100% efficient and material between galaxies is very sparse. And, even if you are using Bussard ramjets as propulsion, is there enough hydrogen for fuel? If we are restricted to lightspeed, then intergalactic travel is damn near impossible.

 

 

Sayonara said :

 

It is foolish and arrogant to take the absence of recognisable evidence for alien visits to Earth in the distant past as evidence against intelligent life elsewhere in the galaxy.

 

And there is no getting around that.

 

This is an assertion' date=' not an argument. Present your logic or your evidence, or else it is just a statement to be taken on faith. [/quote']

 

As stated, it is a sound scientific principle: absence of evidence is not evidence of absence.

 

There are many, many hypotheses to explain the lack of evidence today of visits in the past. Especially the geological past. Many of these are the same hypotheses that explain the absence of transitional series of fossils between most taxa: only a small area in a limited time was visited, that geological strata is either not exposed on the surface or has already eroded away, there are a limited number of paleontologists and they simply haven't found the site yet, the visitors did not leave any evidence that would have survived to today.

 

Any successful expansionist species moving through the galaxy would be expected to live primarily in space habitats for the reasons given. However, they would also move onto planets. My logic assumes some population pressure. Unless they had a brake on reproduction, sooner or later, they would be looking for each last bit of habitable acreage.

 

Bad assumption. Remember birth control? The distance between stars using lightspeed is such that birth control MUST be practiced most of the time. Such ships are going to be generational: several generations living and dying on the ship. So, in order to undertake such a journey in the first place, they must have a brake on reproduction. Otherwise they couldn't maintain a stable population on the ship.

 

Such a society might not want to live on a planet. Blish's city ships and Poul Anderson's "Kith" and spacefarers in Spaceship are just 3 examples where it can be imagined that humans establish a nomadic culture living only on spaceships and not on planets. One thing much bigger than the galaxy is the ability of living things to grow in numbers. And, if there were many intelligent species, the ones with brakes on reproduction would be overwhelmed by the ones that did not.

 

All my 'logic' may be just so much hot air, and is very likely to be. However, I enjoy speculating, and that is the justification.

 

I'm glad you enjoy the speculation and I hope you enjoy my testing of those speculations.

 

 

Occam's razor in its original form states simply that entities should not be multiplied unnecessarily. In other words, make as few assumptions as possible, and discard those aspects of an explanation which are not necessary to it. He also said that, given two explanations with equal predictive power, one should favor the simpler one. So how was bascule's usage incorrect?

 

Because that isn't Ockham's Razor. The Razor has nothing to do with assumptions. What Ockham said was "Refrain from adding unnecessary entities to describe the phenomenon." His example was the statement:

 

“A body moves because of an acquired impetus” vs “a body moves”. In Ockham's day a force called an "impetus" was supposed to make things move. But movement is a succession of points in space over time. So, the statement "a body moves" is all you need to describe the phenomenon.

 

Ockham argued against favoring the simpler explanation. That's because others of his time were arguing that the simplest explanation HAD to be the correct one. Ockham realized that this was not true (Ockham hated the idea because it limited God's power).

 

So, we can have the statements:

1. Planets move in elliptical orbits.

2. Planets move in elliptical orbits because of gravity.

3. Planets move in elliptical orbits because alien spacehips push them.

 

Both #2 and #3 should not be used. In each case, anything beyond "orbits" is unnecessary to describe the motion of planets. In both cases, those are theories about WHY the planets move as they do, but have nothing to do with describing their motion.

 

 

Where did the H and He come from originally?

 

Insane has part of it, altho what he said is not what I have read. Remember E= mc^2. Matter and energy are two forms of the same thing. The early universe was much too hot for matter it exist, there was only energy. As the universe cooled there was a phase transition and the energy converted to matter. It did so in both matter/antimatter. Those tended to annhilate each other and form the gamma ray photons, BUT, there was a slight excess of matter. That became the hydrogen and helium.

 

The gamma ray photons became the cosmic microwave background radiation. With the expansion of the universe the wavelength was strected from the very short wavelength of gamma rays to the much longer wavelength of microwaves.

Since 10% of the stars in the Milky Way are about 2 billion years older than our one' date=' then (based on the assumption that lots of intelligences evolve) it is reasonable to deduce that at least one intelligence colonised the galaxy 1 to 2 billion years ago. Thus, the signs I am talking about would be right here on Earth. Hell, humankind produce enough durable garbage. An alien species would be seriously likely to do the same. The result would be a plethora of fossils.

 

Since there are no such signs, it is reasonable to assume that alien intelligences are rare.[/quote']

 

You have to leave out all the stars except those in a toroid at some distance from the center. That's in a new Scientific American article earlier this year. So I'm not sure your calculations of probability are correct.

 

Now, "durable garbage" is different from fossils. Durable garbage would be things like titanium turbine blades for jet aircraft, or plastics. However, I'm not sure if even this would last after a million years. Of course, gold rings or other jewelry should last.

 

You mean "reasonable to conclude", not "assume". However, that conclusion is no more reasonable than the opposite conclusion supplemented by different hypotheses: such as technological civilizations destroy themselves before they can make the massive financial investment in an interstellar ship (moving at 0.1c).

I ask this with the evolution of the universe in mind. The universe was born 14 billion years ago' date=' the earth 4.5 billion years ago, and life on earth...I don't know 1.5-2 billion years ago? How much earlier than 4.5 billion years ago could a planet like earth of been created. How about intelligent life. Could people smarter than us of lived 2 billion years ago, which means life on their planet probably started 2-3 billion years before that (if their evolution is anything like ours) or was the universe just not fit to do such a thing yet?

 

About stars also. Stars have been observed "burning out" right? Our star's lifespan will be longer than 14 billion years....right? Why did those stars burn out so fast?[/quote']

 

From my reading, there is the problem of heavy elements and planets. At the Big Bang there was only hydrogen, helium, and some lithium. Other elements up to iron are formed by fusion in stars. Some stars then explode in novae or supernovae (depending on their size) and scatter these elements into interstellar dust and gas. Then new solar systems form from the dust and gas. When the first generation of stars formed, there was no carbon to be the basis of life. Even second generation stars apparently are unlikely to have had enough heavy elements in the dust and gas of their solar systems to get rocky planets like earth. Our sun is a 3rd generation star.

 

Now, life formed at least 3.8 billion years ago and probably earlier. It appears that life appeared as soon as the earth was not molten from the impacts of rocks whose impact formed the earth in the first place.

 

Once you have the intelligence and language ability to build a technological civilization, there really isn't a lot of selection pressure to be more intelligent than that. Of course, if any species had a several million year head start on us, their technology would be impressive, even tho their basic intelligence is probably not above ours.

 

The larger a star, the more gravitational pressure compresses the material of the star. This means that more nuclear fusion happens in the core and the star is hotter. That's why you get stars that a blue or blue-white. Our star is a medium sized star. Since "more nuclear fusion" means more fusion reactions per second, it also means that larger stars exhaust their nuclear fuel faster. So they "burn out" faster. The really big stars collapse under their own gravity, causing fusion of heavier elements than hydrogen and resulting in novae and supernovae.