I think the biological analogy to your example would be the case of genes being randomly generated at inception - no heritiability. In this case, if we looked at a population of animals at a certain age, we’d see characteristics that tend to help the animal survive to that age (like being a six in your example.) The reason it is not evolution in the normal sense is that the chatacteristics do not change at all over generations. One million years later, assuming the same environment, you’d get the same percentage of animals who die young. With evolution, of course, the percentage of unfavorable genes would decrease, and relatively more animals would survive, all other things being equal.
As for things we don’t understand yet - two words - dark energy.
This is one of the reasons I love this place. Where else can an interested but uninformed layman chat with someone who knows this stuff? J
I knew that the universe is expanding, but I thought that the expansion was uniform across space, and that the reason more distant objects were moving away more rapidly was because there was more space between us and them, and therefore with the same amount of expansion per unit distance, you would have more space coming into being between us and a more distant object, so we move apart more quickly.
But you’re saying that the expansion is stronger (and therefore faster?) at increasing distances? Or have I misunderstood this completely?
That is one big error. It does make you think there’s something pretty fundamental we’re missing. Any personal guesses?
The galaxies are held together gravitationally by a majority of matter we can’t see.
Perhaps the matter is in the form of neutrinos which may have a very small mass going through to interstellar gas and dust, up to rogue planets, black dwarves, etc.
Evolution is the process of progressive modification across generations. Without heritability in some fashion (whether by genetically-defined characteristics acted on by selective pressure, Lamarckian-type inheritance of acquired characteristics, or some other method by which progeny acquire characteristic qualities) there is no progression, just random drift about the mean. For biological evolution, Darwin’s “descent with modification”, what we now call natural selection, is the prime theory (to a point of virtual certainty) on how evolution works.
Again, yelimS’s example doesn’t represent evolution, even in a conceptual manner. It demonstrated the process of selection by weeding out undesired (non-six) rolls of the dice, but the end result is a convergence to a statistically determinant mean, with individual rolls (or a collection of rolls) falling somewhere in statistical distribution. In evolution, each “roll” of the dice would have some influence on the successive rolls, all the way down the line. In yelimS’s analogy, the rolls are essentially reset every sixth roll, so there is no progression. If you were to plot the results as a function of frequency of individual numbers, you’d see some initial noise, then a tendency toward the statistical mean. The error would be a convergent series. This is not evolution; this is statistical convergence. Different game entirely.
Again, this is an example of selection, but not a good analogue of evolution in general, which requires progressive modification by definition.
Correct. This part works with or without a cosmological constant. The problem is that the Universe seems to be not just expanding, but accelerating, and ordinary attractive gravity can’t account for that all by itself. Even if the density were very much below the critical density, such that the expansion would continue forever, it’d still be slowing down. It’d asymptotically approach a constant expansion rate, so eventually the slowing would become imperceptible, but it certainly wouldn’t speed up. Except it does, which means that ordinary attractive gravity isn’t the whole picture. We need to add the repulsive cosmological constant term.
I think the confusion in yelimS’ case is because the system he describes has many of the same outcomes of natural selection but via a different mechanism. Imagine a jar with different shaped rocks that is being vibrated. Over time, the smaller rocks will migrate towards the bottom so it would be tempting to say that the small rocks are, to some degree, fitter than the larger rocks and “evolve” down to the bottom. Only this explaination would be completely wrong. It’s via a completely seperate process which happens to share many of the same traits.
It may be useful as a pedagogical exercise to help people visualise the concept of natural selection but saying the dice game is an example of natural selection or evolution is in the strictest sense, wrong.
The cosmological constant isn’t used to (directly) account for the rate of expansion, but rather the change in the rate of expansion?
Currently, that rate is increasing, and is doing so by a huge factor, even though our current understanding would posit a much, much lower (and negative) rate of change?
We don’t have a clue why.
I’m amazed everyday by how much I don’t know. Cool stuff, definitely.
We think that gravity is one of the four fundamental forces of the universe. We have theories that say that three of those forces are different manifestations of some more fundamental force (like electricity and magnetism are different manifestations of the same force). To a theoretical physicist, if three of the four fundamental forces are really the same force, the fourth really should be, too. But no one has figured out a theory that makes that work yet.
Electromagnetism has another mystery for physicists. You can have a particle (say, an electron) with just a negative electric charge and no positive electric charge, or vice versa, no problem. But you can’t have a magnetic north pole without a magnetic south pole, or at least no one has ever found a single magnetic pole by itself.
Because without inheritance it fails to share the very basic tenet of evolution. At the end of process you have exactly the same dice you had when you started, and that isn’t evolution in any reasonable definition of the term.
Ok, I’ve re-read what you wrote, and I think I’ve got this wrong.
Try this instead:
The cosmological constant doesn’t describe a change in the rate, it’s that the rate is changing in a way not accounted for just by the attractive force of gravity. In fact the rate of change is going the other way (expansion is speeding up) than would be the case if gravity was the only controlling factor.
So we put this fudge factor into our calculations, the cosmological constant, so the total of the gravitational attraction and our fudge factor give a value consistent with the observations. Currently, that means that the fudge factor is massively negative (repulsive instead of attractive).
Plus, symmetry makes it a lot easier to remember the formulae, which I secretly suspect is the real reason physicists are so insistent about it. (Chemists, however, care naught for consistency and would be perfectly happy to ignore the whole business of fundamental forces in favor of counting all the “made up” intermolecular forces. )
Not exactly. Basic, vanilla general relativity would predict a negative rate of change, but doesn’t say how big it would be (that would depend on details of the Universe like what the density of matter happens to be). However, there’s a very simple and straightforward modification to general relativity, the cosmological constant, which does account for a positive rate of change. Particle physics theories seem to provide a mechanism for the cosmological constant phenomenon to occur, but the prediction made by them is far, far too large.
Correct.
Anne, unification of gravity is actually a slightly different problem than quantum gravity. Unification of gravity with the other three forces would require quantization of gravity, but quantization of gravity would not necessarily require unification. The string model proposes to do both, but loop quantum gravity, a competing model, looks nearly as promising for quantization of gravity, but doesn’t include any natural way to unify it with the others. And there’s no real reason, aside from aesthetics, to expect that all four forces should be unified, anyway: As it is, electroweak unification is well-established, but models unifying the strong force with the electroweak still have some pretty big gaps in them (though these gaps aren’t nearly as far out of reach as are the gaps in quantum gravity; in the next few years accelerators should be good enough to start testing some of the predictions).
As I said, in yelimS’ example, its not the individual dice that are evolving, or even the dice as a group, but rather, the statistical distribution that can be read off of them which is evolving. You do not have exactly the same distribution before and after the experiment, and indeed, the distribution afterwards is radically different tha the distribution before. Yet this outcome is brough about by acting on individual dice in particular situations, rather than intentionally acting on a distribution as a whole. Similarly, in the case of evolution by natural selection, speciation is brought about by action (though of course not “intentional action”) on individual organisms and genes in particular situations, rather than by some kind of action on the species as a whole.
Frylock, get over it. This has got to be one of the most pointless arguments I’ve seen on here and is just an inconsiderate threadjacking. Why don’t you start a Great Debate about how choosing rolled dice that come up sixes are an excellent example of evolution?
You don’t need a program to figure out the dice example.
1s can only come from dice rolled in the last minute that came up 1.
2s can only come from dice rolled in the last 2 minutes that came up 2.
3s can only come from dice rolled in the last 3 minutes that came up 3.
4s can only come from dice rolled in the last 4 minutes that came up 4.
5s can only come from dice rolled in the last 5 minutes that came up 5.
6s can only come from dice rolled in the last 6 minutes that came up 6.
1+2+3+4+5+6=21.
100/21 = 4.761%.
P(1) = 14.761%
P(2) = 24.761%
P(3) = 3*4.761%
etc.
I’m not sure, but I would think it would close in on these numbers after a very small number of rolls (21? 7?), you shouldn’t need 10 million iterations. It’s not approaching a limit, it’s just statistically varying around the statistical ideal.
— from PC Apeman
1: 4.7613%
2: 9.5266%
3: 14.2940%
4: 19.0557%
5: 23.7952%
6: 28.5672%
My apologies? I think? Except I haven’t yet figured out why the comment “get over it” would correctly apply to me?
Well…
I do not agree that the conversation is pointless.
But my apologies for not realizing this is a hijack. (I was just answering emails. I was not even aware of the title of the thread. In general, robust conversations within threads are about the topic of the thread, so I do not have a general habit of “double checking” thread appropriateness when I concieve of myself as participating in a robust conversation within a thread.)
I don’t agree with your implicit judgment that I am some how the one keeping the conversation in question going.
I will not be starting a GD thread. This issue is not something I am concerned about in that way. If the conversation were to end here and now I would not care much. If the conversation continued in this thread, I would participate. If someone else started a GD thread I might or might not participate. The issue’s not really on my radar to the extent you seem to think it is.
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