First, not all dinosaurs were huge. It’s not a trait of dinosaurs in general. Rather, the environmental factors in the past and some factors that are true for reptiles, allowed being huge as an acceptable evolutionary niche, more than today!
Why would some of them grow so big:
In evolution, it’s always a bit of a hen and egg problem. And there is between species competition called “Red Queen Hypothesis”.
So a likely explanation is that, due to high CO2 atmosphere, plants grew larger which lead to having a long neck or being tall being an advantage. And for carnivorous species bigger herbivores meant that being bigger is an advantage. That, again, meant their prey had pressure to grow bigger (and/or faster), and so on and on.
How could some of them grow that much:
Dinosaurs are reptiles, so they were poikilothermic. Since temperatures have been higher and more stable at their time, a bigger body allowed to keep body temperature stable as well. It doesn’t cool off as fast which allowed more activity which allowed eating more which allowed a bigger body.
There was also significantly more oxygen in the atmosphere which is associated with bigger growth in all species since our metabolism depends on it.
This is especially true for Arthropoda btw, some of them were huge in the time of dinosaurs because they breath through their exosceleton. The biggest centipede found (yet) was 2.5 m long! The difference in size between insects in the past and insects today is much bigger than between reptiles today and in the past. All due to bigger plants and more oxygen and the interaction spiral between prey and predator.
At that point in Earth’s history, the atmosphere was a lot more oxygen rich than it is now! This allowed all sorts of creatures to grow to immense sizes, like trees, insects and dinosaurs. Dinos like Brontosaurus probably grew large for the same reasons Giraffes did too. The best greenery is the one no one else can get to!
grew large for the same reasons Giraffes did too. The best greenery is the one no one else can get to!
Recent evidence in the fossil record regarding giraffids suggests their necks did not evolve to be long for feeding purposes, but rather sexual selection / fighting for dominance with their necks and heads.
Not sure you got the oxygen part right. But I can say that since trees and animal breath each others exhaust, they won’t both thrive due to atmospheric oxygen concentration.
They weren’t all big, but anyway, they (probably) evolved like giraffes to reach for food and as protection against physical damage from predators. The climate was also different and they had plenty of food.
Anyway, evolution does not select. It’s not survival of the coolest features… it’s only reproduction of those that manage to reproduce.
I think it would ultimately depend on a use case for that metric, otherwise you're putting the cart before the horse. There are many measurements and calculations you could come up with, but no obvious (to me, anyway) interpretation of "most discontinuous": something is either in one piece or not. If you needed a metric like this for a practical purpose, your specific needs would be a starting point for designing one. If it's more of a shower thought, you sort of have "too much freedom" to be able to define anything that's necessarily meaningful.
Simple examples would be just "number of 'discrete parts'", "minimal area needed to span all territories" and things like that. Maybe you're more interested in "total distance from all satellites to wherever the capital is" or something, in a different context. The point is they'd all tell you radically different things, so it's important to know which one to ask for.
You could argue that something like Hawaii and Alaska's distance from the rest of the US makes the US score highly.
You could argue that any number of island nations score highly because after all, most of e.g. the US is in one part.
You could argue e.g. Norway's territories near both poles make it pretty high-scoring too.
You could argue that for whatever reason, distribution of area and population matter, and so on.
SI is great, but if you reset everything (and lose all tech and most of knowledge), just create a new system. Embrace what makes SI great (easy conversions and a the nature-based properties) and do it over.
For length, use Hydrogen line when you advance your society enough. It’s more universal than using 🌎 as a 📏.
Step 1: Find the area of each chunk. The biggest chunk is your main chunk.
Step 2: Find the distance between the closest edge of main chunk and the center of each other chunk individually.
Step 3: Discontinuity of each chunk is area of chunk * distance from main chunk / total area.
Step 4: Total discontinuity is sum of each chunk’s discontinuity.
Bolded parts are important. If you use the center of the main chunk, larger main chunk radii make other chunks seem more discontinuous than they should be. If you use the closest edge of other chunk’s, you don’t account for the entire area of the other chunk.
This will give you a number that is bigger when there are more and/or bigger pieces that are further away, and smaller when the opposite is true, normalized for the total area of the country so bigger countries aren’t penalized just because they’re bigger.
Maybe we look at the ratio of country perimeter to area? Counting the number of exclaves could also be a factor. And maybe a ratio of the distance to cover all the exclaves divided by their area?
So if a country were a perfect circle it’s perimeter to area ratio would be 2/r, it has zero exclaves and then it’s width would be the diameter.
If a country were two perfect circles of the same diameter, separated by a distance of the same diameter, it’s area ratio would be 2/r, exclaves would be one, and it’s width would be three times it’s diameter.
So now you can imagine a country like Chile, modeled as a really skinny rectangle, has a pretty large perimeter to area ratio, no exclaves, and a width roughly the length of the rectangle.
I guess you’d have to decide if archipelago nations are measured as the geometry of the sea they own, or as discrete islands.
Thanks for the proposal. That gets us somewhere already, although only for non-landlocked countries. Using the perimeter also opens us up to the coastline paradox.
I guess you’d have to decide if archipelago nations are measured as the geometry of the sea they own, or as discrete islands.
I think that it might serve us better to consider them as distinct islands, to keep the measures comparable with landlocked countries.
You didn’t really mention how this is all being tabulated. Just in theory? Do you have access to data sets or are you making them? The coastline paradox only really exists for smaller and smaller measuring devices. If for example your method is using satellite images of a given resolution, or another consistent measuring tool, the measurements should be comparable between country borders and therefore the error or the paradox should come out in the wash.
I would imagine using some sort of shapefile that I can run calculations in a scripted manner. So, in that case it will depend on the resolution of the shapefile.
I would do perimeter^2/area, to avoid biasing toward small countries. Divide one circular country into two circles with the same total area and p^2/A goes from 4 pi to 8 pi. Divide a square country in two and p^2/A goes from 4 to 6.
I did this all in my head. I think you are right. Point being, small simple algebraic expressions stacked as a a polynomial can be used to create relative scores for this type of analysis.
If the sphere of destruction is propagating at the speed of light, then any observable effect reaches you at the same time as the sphere itself. Either you don’t observe it because you’re far enough away to be safe, or you don’t observe it because you’re dead the instant it becomes observable.
Incidentally, you might be interested in looking up the idea of false vacuum decay - although if you tend to get anxious about end-of-the-world hypotheticals you might prefer to give it a miss.
Observation cannot travel faster than the speed of light. No matter what it is you’re using to observe: Photons (light and radiation), measuring gravity, heat, anything. No matter if the phenomenon’s expansion were traveling at the speed of light, the changes to the universe being made as well as our ability to observe them are also traveling at the speed of light.
If the phenomenon were very far away, we would not be able to observe anything it was causing until its leading edge caught up to us. Then we would be destroyed at exactly the same time. This is because in your example it is expanding at exactly the same rate as the universal speed-of-light constraint allows us to receive any indication of its presence. Any evidence of, e.g. a far away star being destroyed would take X amount of time to reach us by its light no longer arriving. However, in that time the edge of the space-destroying phenomenon will also hit us, because it will also take exactly X amount of time to reach us, at the speed of light, from the point where the star was when it was destroyed. The distance is the same, the speed is the same. We would continue to receive light from that star in the meantime, as we already do. (The light from the stars you see in the sky now is already tens/hundreds/thousands/millions/etc. years old depending on the distance to the star in question.)
If the phenomenon were so far away that it is outside of our observable field of the universe, it will never reach us and we will never have any indication of its presence. That’s what “observable universe” means. Anything can happen anywhere outside of the observable universe and it is objectively meaningless to us, because we will never ever be able to reach it, record it, have it influence us in any way. This is, however, predicated on the theory of the perpetually expanding universe being true (which it probably is).
If you want to actually see the stars in your sky winking out over the millennia, I suggest building your universal destruction bomb such that its shockwave travels at, say, half the speed of light or some other suitable fraction.
Thanks, I was having trouble intuitively on that tipping point of expansion moving objects faster than the speed of light and how that is observed without more than lunch napkin level thought. Makes sense. We would never know about or see “the bubble” if it stopped short due to expansion.
The best we can achieve in this thought experiment is to see through a telescope some faraway alien set up a bomb with a countdown timer that will surely blow up at a specific time in the future and destroy the universe, but which we’ll never see count down to zero or explode. If we saw it reach zero it would of course kill us in the same instant as we see it, because by the rules of the thought experiment the explosion travels at the speed of light. But if the alien is far away and the countdown is long enough, the accelerating expansion of the universe due to dark energy will carry it outside of our cosmic event horizon before it explodes.
Using the cosmic comoving distance definition and the cosmology calculator, the last scattering surface of the Cosmic Microwave Background for example is 45.5 GLy away. Its light was emitted 13.7 GY ago (400kY after the Big Bang) at redshift 1100z. I was told that due to accelerating expansion, we will never see galaxies further than 63 GLy away (we don’t see them yet, the matter that we’ll see form them is beyond the CMB sphere for us at present), and if we hopped onto a lightspeed spaceship right now, we can never reach galaxies beyond 17 GLy comoving distance.
So for example if we looked at a galaxy at redshift 3z which is 21 GLy away, and whose light took 11.5 GY to reach us, and saw the alien set up the bomb timer to 11.49 GY, we know that the bomb must have surely exploded by now, but also know that we are safe because it’s far enough away and we’ll never see it explode, even in the infinite future.
Similarly, we can relish the tiny shred of joy in the knowledge that if we did fuck up something really major, like creating a false vacuum bubble in the LHC or whatever, we can never destroy more of the universe than the 17 GLy bubble around us.
An explosion wouldn’t change the gravity situation though. Gravitational waves are not relevant here. The danger of an explosion would be the physical matter stripping the atmosphere, and radiation. I think it would take quite a bit longer before Earths gravity is affected significantly based on the drag from traveling through the debris. A gravity well is about the total mass in the center. So wouldn’t a significant amount of material need to make it past the orbit of earth before the orbit is directly altered? The expansion would impact the rotation of matter from the stellar body, but that is not coupled to an orbiting body in a vacuum.
You are right! People often say “what if the sun blew up” in the context of gravity speed vs. light speed thought experiments, but what they really mean is shorthand for what if the entire sun was somehow deleted in a single instant with no trace. But in reality, “blowing up” the sun is much different than “deleting” it and leaves its entire mass behind, just spread around more.
There is even a theorem in general relativity that proves that massenergy cannot be deleted, invalidating a whole swath of such thought experiments. Forgot what it’s called though.
Fun idea. You mean like the expansion of the universe is going 0.5 light speed at the edge of the void, so the spreading void is basically pulled back right? And then any photons that reached us from just before this void are traveling a tiny bit faster I guess? Being just outside the void?
I’d start with making a surface plate using Whitworth’s 3 plate method.
Next, make a perfectly square block, pick two opposing faces of that block, that’s your unit of length. Use your surface plate to make more and measure things against it.
If you’re really smart you would have made that block out of some sort of homogeneous material like steel and made it a perfect cube, not just perfectly square. That’s going to be your prototype weight.
Temperature is the easy one, make a thermometer. Mark where the liquid is at based on two different repeatability phenomenons. Subdivide as desired. Someone will come up with a “better” way later.
Time is another easy one, just build a pendulum and start counting.
That sould get you through most of the neo-industrial revolution.
The rest of the base units will come later for now focus on building a lathe.
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