mistermack

From wikipedia " There is general agreement on the most ancient record, which shows that feliforms and caniforms emerged within the super-family Carnivoramorpha 43 million years before present(YBP).[3] The caniforms included the fox-like genus Leptocyon whose various species existed from 34 million YBP before branching 11.9 million YBP into Vulpes (foxes) and Canini(canines). " https://en.wikipedia.org/wiki/Evolution_of_the_wolf

You may be right about me not looking at intelligence over a long enough timeframe. I'm comparing the wolf or the bison to humans, and the difference is phenomenal. The ancestor of the wolf is thought to be a fox like animal dating back 34 million years, and there's not much obvious sign of an intelligence increase. Humans started a dramatic process of brain-size increase about five million years ago, while our closest cousins like chimps and bonobos underwent no noticeable change. You would have to do your own research to get an idea of the brain size of the ancestors dating from that period. They are all generally described as similar in brains to the modern chimpanzee, and the first human differences were bipedal walking and dental changes, rather than brain expansion. In any case, it's not clearly known which species were direct human ancestors, and which were side branches. Ardipithecus Ramidus is a good candidate for the first ancestor after the split, it's older than the famous "Lucy". https://en.wikipedia.org/wiki/Ardipithecus Brain size is very chimp-like. It's dated at about 4.4 million years.

Yes, that's a fair point. I'm still not convinced though, that constantly increasing intelligence is an inevitable line for evolution to take. It is one successful line though, there's no doubt about that, if you stand back and look at the whole four billion years. I tend to look at our own species of modern humans as a freak of nature though, that might be a one-in-a billion occurrence that is unlikely to be replicated on other planets. Human evolution is my favourite science, and the expansion of the human brain hasn't been explained in any satisfactory way, and is really a complete mystery, with just guesses at possible mechanisms. I used to wonder why other species DIDN'T evolve higher intelligence. From our point of view, you would think that bison could easily defeat wolves, with a bit more intelligence, (and vice versa) but there doesn't seem to be any sign of a trend there. If you go along with that line of thinking, and look at the rest of the animal kingdom without humans, there is really no sign that any species could get anywhere near any form of technology for millions of years at least. All of our ape cousins are roughly no more intelligent than the last common ancestor, seven or eight million years ago. I'm just proposing it as a possibility, that there is a natural intelligence ceiling that might apply in most worlds, and that our own species breaking through it is a weird and freakish event, not likely to be replicated elsewhere.

Hi, Moontanman, I get migraines too, so I know what it's like. Mine are as bad as anyone's I know, including unpleasant vertigo and visual disturbances. So if you ever find a cure, get in touch. I get what you're saying about the number of units being able to expand exponentially. That's what the human population of the Earth has done over the last few hundred years. The problem of the scale of the galaxy isn't really affected by this process though. The FRONT of the expansion, if you picture it as a sphere expanding, can only progress at the speed of an individual ship, and the numbers of ships have no effect at all on the maximum speeds possible for the pioneers. So the expansion from the centre can only progress at the top speed of a single ship. Yes, the VOLUME occupied can accelerate, but the DISTANCE from the origin can only increase at the original steady speed. The only way for that to improve, is new methods for increasing the top speed of the individual ship. Say the Earth is the origin of the process. Using today's rocket technology, Voyager 1 is the fastest probe humans have launched, and it would take about 100,000 years to reach the nearest star. It weighs less than a ton so it's not in the same size and weight league as what you are proposing. The distance from us to the other edge of the galaxy is about 25,000 times the distance to the nearest star. So craft like you propose, travelling at voyager 1 speeds, would finish colonising the most distant part of the galaxy after 25,000 X 100,000 years. Which is 2.5 billion years. If you scaled up the size to mobile environment size, as you propose, you would need unheard of quantities of energy to achieve that sort of speed. How many tons would a self sufficient environment comprise? For each additional ton, you would need the energy of one voyager 1 vessel. And as I said earlier, to be able to slow at a destination, you would need the same energy again. So to sum up, yes, of course the volume colonised could grow faster and faster as you described. But the distance from the centre would not accelerate, it could only move out at the rate of a single ship.

The link that you gave made very fanciful estimates, seemingly taken out of thin air, that a craft could cross the distance of ten light years in ninety years. That's about a tenth of the speed of light, and yet you are claiming that no individual craft would have to travel fast. It's full of gigantic holes. How could a bulky mobile environment be made to AVERAGE one tenth of the speed of light, including acceleration and deceleration phases? My own estimate, of about 20 million years for that sort of distance, is probably wildly optimistic. Your notion that spreading out, rather than travelling from a to b, is somehow quicker, is simply wrong. The SHORTEST distance from a to b is a straight line. Any other process, like the one you described, is much slower. An ant can travel from one colony to another in minutes. The colony would take months or years to grow the same distance. If you actually look at the distances involved, and do the simplest of maths,. the fermi-paradox is no mystery at all. There are probably thousands of intelligent communities in the Milky Way. They are just too far away to have made contact. There is no physical way to get material to travel fast enough, and no signalling method that can be detectable over such distances.

With the best of modern technology, and a tiny craft, you could do it in a hundred thousand years. But not if you wanted to carry enough energy and material to slow down when you got there. For a craft the size that you are proposing, it would take millions of years to travel five light years, and a vast amount of energy at both ends, to accelerate and slow down. You might try a gravity assist from the Sun, but the mass of the shielding needed would be self defeating. Five light years is approximately the nearest star distance, ( Proxima Centauri, 4.2ly) so you can imagine the time scales needed for what you are actually proposing, spreading across a galaxy that's about a hundred and fifty thousand light years across. A crude figure, probably way too conservative, would be 20,000 alpha centauri in a straight line without stops, taking about 200 billion years. That's not counting the stops at each replication stage.

So how long do you think it would take to move your habitat a distance of five light years?

It does, because size affects the timescale over which things can happen dramatically, especially when you are hoping to cross vast distances at high speed. Size also affects timescales of manufacturing and mining materials etc. I don't get your comment about controlled fusion either. While it might be of use somewhere, it's not much of a requirement in space, anywhere near a star. Energy is not in short supply in space near a star. Fusion would be using a sledgehammer to crack a nut. On the other hand, if you were thinking of using controlled fusion in a space vehicle, I would forget it. The size and weight would have to be gigantic.

Why would you need to colonise the galaxy of about 300 billion stars? Our own star would support billions of artificial environments for the next four or five billion years. Extinction avoided right here.

If somehow, aliens could evolve with a high intelligence and tiny body on the scale of a virus, then it might be a practical proposition. I doubt it though. You have the problem of cosmic rays in empty space. No matter how small and lightweight your aliens, they would need massive shielding on their travels, which would defeat the advantage of a tiny size. Once size increases, then everything gets harder. Your artificial habitat needs huge energy to get where it's going in a reasonable time. And then it needs to develop a full manufacturing capability, in an unknown environment, to be able to reproduce in a practical way. You don't say if you are proposing purely robotic "habitats" or occupied ones. Anyway, who's to say that a rival bunch of aliens don't come across your habitats, and simply adapt them to what they want?

If they simply expanded, it would obviously be incrementally slow, compared to a deliberate voyage. It would be no surprise at all that we have never encountered aliens, if you were waiting for them to arrive due to expansion. In any case, the concept of a need for expansion is not really a logical one. How long would it take, for humanity to exhaust the energy and materials of the solar system? Probably longer than the 4.5 billion years that it has existed. And if we did, we would only need to expand to the next available star. (which does have planets, I believe).

The way I would look at it is that if E=mc2 then m=E/c2 so a massless particle has a mass equivalent, but it's obviously going to be absolutely miniscule. If you are used to visualising a huge amount of energy tied up in a small amount of mass, then this is just the reverse of that.

Moontanman, just because a planet evolves a civilisation, that doesn't mean that they would ever have the ability to make contact across tens or hundreds of thousands of light years distance. If there ARE billions of planets in the Milky Way, then where do you choose to direct your message to? And why would you do that anyway? You might be inviting trouble. I certainly wouldn't recommend that we should do it. So why should they do it? We might have a distorted idea of the likelihood of a technological civilisation arising, because we are living in one. Ours might be a one in a billion freak chance, or it might not. We have no way of knowing. Then there's the problem of crossing vast expanses of space. The speculation about finding ways of defeating the laws of physics is probably way off the mark. It's hardly worth even considering. The amount of energy needed to accelerate something with mass to a significant fraction of the speed of light is gigantic. And there is another inherent problem. If you expend that huge quantity of energy to accelerate, you need to carry the same amount of energy with you, in some way, so that you can decelerate at the other end of your trip. And that requirement puts up the mass of the ship, which puts up the required energy, which puts up the mass. So it's likely to be an exponential increase in the requirements, the faster you plan to travel. If you want to travel a distance of ten thousand light years, and you are limited to 1% of the speed of light ( a huge number) then the trip will take a million years. I can't see us bothering with that kind of enterprise, so the same would probably go for aliens.

My own feeling about the fermi paradox is that we humans really are freaks, and that intelligence will generally reach a plateau and progress no further. Evolution works, we know that. But it rarely goes further than the minimum needed for survival. If you look at Chimps, or Bonobos, or Dolphins, or Orangutans, they seem to have hit a brick wall in the intelligence stakes. While humans evolved this huge brain, Chimps are much the same as our last common ancestor. Take out humans, and look at what's left, and most people would agree that intelligence levels off, once it reaches chimp or dolphin level. We don't know why we are so different, but it could be a one in a trillion occurrence. And don't forget that we very nearly went extinct ourselves, according to the dna evidence of a population bottleneck. Every other strain of humans is now extinct. A big brain is no guarantee of persistence of a species.

Is the curvature of spacetime directly related to the strength of the gravitational field at a point? I was viewing the one as a way of modelling the other for mathematical purposes.

So what does curvature actually mean in words? How does it relate to the free fall of an object?

Am I right in saying that curvature is four dimensional curvature, a combination of speed and mass and distance? For instance, if your speed relative to the Sun is zero, then your free fall is a straight line towards the centre of the sun. The faster you move tangentially, the greater your deflection from that line in free fall. And the speed of light gives the greatest deflection. So it's wrong to picture a fixed curvature of space ?

You might like to read a bit about the river model. My thread in speculations had some interesting relevant thoughts and links on that subject. I'm not pushing "my own hypothesis", it's just easier to link it than bulk post a load of stuff from it: https://www.scienceforums.net/topic/110805-gravity-please-knock-this-down/

This stuff is hardly news. Even the popes had white slaves. I remember being taught as a child that one of the popes was so impressed by the good looks of a new batch of British slaves, that he asked where they were from. When told that they were Angles, he remarked, "more like angels". I was taught that in a Catholic school lesson. ( so it might be rubbish )

I think it's mainly a form of social display by the various parties. The main enjoyment people get out of eating a ridiculously expensive meal it in telling people about it later. They will bore you stiff with the most pointless details of what elaborate effort went into the food that they put in their stomachs. It's very like going on a cruise. The main joy is in going on and on and on about it afterwards. People think it gives them status. Maybe it does in some circles. It makes people feel important, and of course, being waited on is all part of the massaging of the self-image.

Nicely put.

Thanks, I get that. I've got a mental picture of a magnet being like a short pipe in a fluid, with liquid circulating in at one end and out at the other, and the field being like the motion in the fluid around it. And gravity being like a pipe sucking fluid in, but with nothing coming out. The fluid motion around the first pipe will drop off quicker than the second.

Fossils in the wrong place? This has happened. I've seen them, in the Natural History Museum. But there is usually a story about how they got there. The same applies to any other apparent misplacement. As someone else said, in view of the billions of fossils that are in the RIGHT place, you have to assume that if you find one in the wrong place, it's probably been moved as the default position and look for evidence of that. If all of the evidence suggests that it HASN'T been moved, then what you have is a mystery. Not a refutation of evolution. It would take millions of them to begin to do that. You also have to be cautious of very clever fakers. It's been done with oil paintings and antiquities "worth" millions. So experts can be fooled.

Why does magnetic attraction reduce so quickly over distance, compared to gravity? ( I don't know the answer ).

If the bar rests on the shoulders, none of it's weight is transferred through the arm joint. You could theoretically take your hands off the bar. If you hold the bar off your shoulders, all of the weight is routed through the muscles and joint of the arms. In both cases, the same identical weight is routed down through the spinal column to the legs and feet. It's just routed differently at shoulder level.