But it is a changing 1.23% on the same plane. Both respective planets have no significant satellites. Venus spins wonky. I’m not saying any of it is related, but it is curious.
Venus is loosely around solar lap 20M, Earth 12M, Mars 6.5M in the last 4.5 billion years. How many 1% differences stack in patterns before there is a problem?
Two more variables that are going to affect the number of encounters are when the "final" orbits of the inner planets were established (the Nice model suggests there was much disruption early on) and that Mars' orbit is very elliptic so it's rarely lining up at its closest approach, which is still pretty far. If anything we'd more likely see some correlation between Earth and Venus if there is any.
Depends how you’re using “why”. In Russian, they actually have two words for why, one of which implies teleology, and one which doesn’t, and merely requests some explanation for a phenomenon. I wish we had that in English.
In this case, it’s such a general question you can’t do much better, but you could, for example, talk about why oxygen-carrying proteins pretty much always incorporate an ion of something, in a merely cause-and-effect way. (And I actually don’t know the answer to that one)
The answer to the question, “How did this evolve?”, is the same as the answer to a non-teleological “why”. People just need to learn to use “how” because “why” is such a loaded word.
When using “how” in this sense and “why” in the non-teleological sense, they have the exact same meaning (at least to my ear), but then the “how” version isn’t ambiguous.
If I say to myself, “How did this evolve?”, the question feels good. It feels clear, and my mind leaps into thinking about the function of the mineral in the body and the chain of evolutionary steps that could have caused it.
If I say to myself “Why did this evolve?”, I just can’t get the teleology sense of the word out of my head. If someone didn’t want a teleological answer, why did they say “why” when “how” is clearly better? So I assume they mean why.
I feel like even if I answered their question, the next one would be, “Yeah, but why?” Making me feel like I wasted my time explaining the “how”.
That’s might be an option too, I guess, but in some situations it’s a different question. If I make a mistake and you ask “how”, you might just get more details. If you ask “why” I might respond with “I was tired”, which doesn’t really imply teleology. As I understand it почему would be more specific to cause rather than just means, but then again my Russian is pretty basic. The word “how” would be как, and it even works as an intensifier the same way.
Animals whose biology that used the metals reproduced more successfully is the explanation. It could longer lives, better reproductive outcomes, or a ton of other reasons but it all comes down to reproduction.
Well, genes, if we want to get really technical. Otherwise you can find counterexamples where genes are detrimental to the organism, but manage to spread anyway do to some quirk.
Generally they don’t impact the reproduction rate enough.
Let’s take reproductive cycles as an example of there being no single benefit or negative. Some species reproduce in mass quantities and that works for them, while others are slower. The fast one having genes that slow reproduction would probably die out because their adaptation of mass reproduction is what keeps them around. A slower reproducing species won’t necessarily benefit from higher rates as they might overpopulate their range. So what looks like a detriment could just be a thing that neither benefits nor is a detriment depending on the complex context of the species and where they live.
And sometimes detriment are offset by other benefits, like sickle cell anemia having some terrible outcomes but it also protects against malaria so in the context of somewhere with a high rate of malaria it is beneficial to survive to a reproductive age, which would explain it sticking around.
Ah, so you haven’t heard about this thing. It’s not really lucky 10,000 territory, but it’s still cool.
There are situations, where in sexually reproducing organisms, an unambiguously bad gene can spread through the population, just by ensuring it’s more likely to appear in the next generation. As long as it’s not so bad it kills the species off, you’re still likely to observe it a lot in a future population. We’ve actually harnessed this idea technologically, with genetically modified mosquitoes that crash their local population by skewing all offspring malewards.
That is one example of ‘not detrimental enough to impact reproduction’ which I meant in the context of a population and not an individual, but I guess that my wording wasn’t clear enough.
Theoretical biologist here. I’m going to push back on that just a bit. I think that you might have mentioned Selfish Gene, too. That was not the best book even at the time of publication (most biologists had a number of problems with it oversimplifying in a way that’s probably similar to what anthropologists think about Guns Germs and Steel). It also has been getting worse the more we learn.
Evolution acts on the phenotype, not the genotype. It affects the gene makeup of the population through differential reproduction rates. “Fitness” can be measured as a value relative to the rest of the population specifically by using the number of offspring. So what I’m saying here is that all factors that affect phenotype, whether genes or other factors, affect evolution.
So, of course genes are important. But you have epigenetic factors, too. link here You also have extensive non-coding regions that regulate transcription. You have rna editing. And so on.
If you’re interested, I would highly recommend a book called How Life Works by Phillip Ball. It was just published in November and is an outstanding summary of how much our understanding of life has evolved (heh) in the last 20 years or so.
Well, you would know a lot better. And thanks for the reading recommendation.
What are your thoughts on viruses as a form of life? Asking what natural selection is in exact terms is pretty closely related to asking what life is, since life is probably some subset of things that can do natural selection.
Personally, I do think of viruses as a form of life, and although it’s not universally held by any means, I think there’s a growing consensus around the idea.
That’s probably as minimalistic as I would go, though. I mean, you can make a similar argument to some extent about prions, but prions are too close to being “just chemistry” for me.
Viruses on the other hand cooperate and compete in complex ecosystems, which in my opinion magnifies the complexity of a virus as an element of a complex adaptive system. They don’t have a metabolism as such (which is why so many don’t consider them living), but their ability to conduct theft of resources of more complex and obviously living systems makes me push them to group of living things.
One of the nearest things about biology is that there’s always an exception to the rules and examples, and the simplifications we make when teaching bio 101 are really best learned as rules of thumb. Things like what a “gene” really is, the operation of selection, and even what constitutes a “species” can lead to some really interesting discussions.
A few fields are a bit like that. I remember my chemistry teacher in high school saying something similar.
As mostly a math person, it kind of bugs me. There definitely is one set of rules that a field obeys, and while it’s usually necessary to simplify I’d really like to know how not to. Sure, water is mostly incompressible, but it’s not exactly so, and that’s how sound works and can translate to other mediums. And then once you get down to small scales, high energies or low pressures you start seeing the individual water molecules being relevant and doing all kinds of different things. Those factors were always there, even if they weren’t relevant.
Sorry, maybe that’s a bit of a rant, but all that to say I’m sure you can find a consensus on these questions eventually.
Sort of. I work closely with geophysics in the rock mechanics world. I don’t personally know if any machines that create folds at large scale due to the heat and pressure required but rock deformation is a big thing they do. I’ve built a few machines that do this.
Small scale experiments at the temperatures and pressures required are done using diamond anvils at extreme pressure and sometimes with laser heating.
Larger scale is done with giant hydraulic presses called triaxes that use confining pressures up to the Gigapascal level.
Yeah, I never thought we could do it at a super large scale since the forces required are too massive. However, I find it funny that we actually do bend rocks, for whatever reason.
The elephant in the room is why? Based on what you described, it seems like a very specific problem that is expensive to solve and happens to be dynamic enough to merit repeated testing.
I am gonna make a wild guess for fun though…
I am guessing the reason it’s done has something to do with mining and trying to solve material density problems. If I needed to drill through a few layers of rock and I knew the material types, sticking samples of those materials in a press that simulates tectonic activity would give me a good idea what I was dealing with. That data seems like it would be key in setting feeds and speeds for expensive drills…
I am guessing the reason it’s done has something to do with mining and trying to solve material density problems.
This is definitely part of it. Oil companies have labs that run samples all day every day to study the density and porosity of rocks to see how much oil or gas they could hold when they’re trying to find new areas to drill.
Most of what I’m familiar with is research labs at universities where they are studying it to simulate tiny earthquakes. It’s just pure research to learn more about how the earth functions as a system. All rocks are different and all situations are different so the more data you collect the more you can understand exactly what happened during an earthquake and why. Maybe it can lead to better earthquake prediction or it can let us use those earthquakes to know more about the structure of the earth.
It is loosely defined from my perspective, but I am curious about harder rocks, like granite. Your standard everyday rock tends to be much more brittle and may not have a high metal content. (It will likely have iron in one form or another though.)
Most metals and rocks are crystals in their “normal” state, so I see what you are getting at.
Your username is basically the notation for a crystal oscillator, so it’s gotta count. (Damn the rules!) Quartz is a rock that bends for a commercial purpose, so thats a really good answer, actually.
The “cure” for rabies is to treat it with a vaccine prior to symptoms appearing. The rabbies vaccine is 100% effective and you will not become symptomatic if you treat soon after the bite. The Milwaukee protocol has been tried and it’s a last ditch effort for people who didn’t get the vaccine shortly after the bite and are now showing symptoms. They don’t even know if the Milwaukee Protocol is what prevented death or if the people it worked on were somehow resistant to rabies.
Because unless you’re living and working in a high risk environment, there’s no need for a human to go get a rabies vaccine because they can just avoid mammals that are acting strangely. It’s not like it’s airborne, you have to get a penetrating bite from a symptomatic animal to get it, so when that happens you just go to the doctor. You’d still likely get the vaccine even after a bite even if you had been previously vaccinated.
Vets and people who work in animal shelters often get the rabies vaccines beforehand. But even if you have been vaccinated previously, you still have to get it again if you are bitten.
The efficacy of vaccines usually declines over time after administration. The immune system starts to “forget” how to fight a pathogen it doesn’t encounter. It doesn’t completely forget, but it puts the treatment data way back in the archives. So when it encounters the real deal, it can take quite a while to boot up production of antibodies. It also varies by the type of disease.
This is fine for some slow diseases ( which is why sometimes a single vaccination can suffice ), but can be risky if the disease progresses faster than the immune system can ramp up the defenses.
Administering the vaccine as soon as possible after suspected exposure to deadly or highly contagious diseases simply helps the immune system to get the necessary blueprints to get in the fight quicker.
Administering the vaccine before any exposure at regular, long intervals is done to decrease the baseline risk. Sometimes you don’t know you have been infected. Many diseases are not only transmitted by dramatic, obvious vectors. In those cases, it’s definitely better to have some old defense than none at all.
In addition to what Senshi said, if you have recieved the full course of vaccines (4-5 doses spread over a month), any future bites need only 1-3 doses. Also the time within which you have to take the first dose increases from 24 hours to 2-3 days, which can be quite useful to vets in remote places.
We’d see that in the redshift: one direction would be more redshifted than another. Instead, we see all points in space moving away from all other points (except points mutually within gravitationally bound systems), and the rate of expansion between two points (recessional velocity) is directly proportional to the distance between them: the more distance, the faster they expand.
Edit: To answer the question in the title: Strictly, we don’t. We know, as you pointed out, that our measurements don’t agree. We also have good evidence that the rate of expansion was different in the past (much, much faster) in the early universe.
That makes sense, but how would we then be able to distinguish how much of the redshift is due to the metric expansion of space and how much is due to their velocity vector component in that direction?
Inflation is supposed to explain this: It could provide the initial impulse to kickstart the velocities. I think the general idea is that the fact that everything is moving away from each other to begin with is explained by inflation, and the fact that this expansion is accelerating is explained by dark energy. Take all this with a grain of salt, here we approach the limits of my tenuous understanding, but what I do understand is that none of this is experimentally verified: No “inflaton” has been found, or any other mechanism to otherwise explain inflation theory has ever been produced such that we could test it, and no working model of dark energy has ever been produced (to my limited knowledge) that we could test or detect.
Tl;dr: I’m pretty sure it’s untestable anyway, we basically will never know during our lifetime short of some breakthrough in physics.
Right, but the velocity component would still be present in some form due to the gravitational attraction between bodies. I don’t know how significant this would be compared to the redshift value from the initial kick from inflation, or if it is possible to separate the two components somehow.
Gravitational attraction is not a relevant factor on the largest scales where dark energy takes over. To be more precise, it’s possible to measure the effects, and to describe a specific distance limit between two bodies where they can no longer become gravitationally bound and are doomed to eventually expand out of each others’ event horizons. That limit is the precise boundary between gravitational dominance and DE dominance.
To be specific, literally everything outside of the Virgo Supercluster (home to Andromeda and Milky Way among others) is outside of this limit, and will eventually become impossible to detect because the light between us and them isn’t moving as fast as the rate of expansion between us and them. Everything within the supercluster is gravitationally bound, and will eventually (iirc, grain of salt on this one) form a supergalaxy.
The Hubble constant is an interesting one – it isn’t actually a constant, but if you reframe it as a partial differential equation, the law is very predictable. en.wikipedia.org/wiki/Hubble's_law#Time-dependenc… – so in many ways, it’s just a misnamed phenomenon, and shouldn’t be called a constant at all.
Any place in the universe beyond which we’ve directly sent probes – is assumed to be like those parts we already know. Part of the reason we make this assumption is that: main sequence stars appear to behave identically across vast reaches of space and time. Thus we assume that physics hasn’t changed significantly (at least within the period of time where main sequence stars exist). Because if the physics was different, the stars would be different (spectra, lifecycles, etc.).
I’ll present a tickler I learned in cosmology decades ago, for hand-waving.
Run the big bang backwards – imagine all of the matter and energy of the universe collapsing to a single point. Which point is at the centre? They all are. Run time forwards again and all the points expand outwards from each other, but which point was at the centre that you can use to reference the centre of the universe against? They all were. Thus, I am the centre of the universe. And so are you ;)
This made my brain melt until I learned to visualize this using lower dimensional surfaces (like Riemann spheres). Imagine a beach ball being inflated. It is a two dimensional surface. You’re an ant on the beach ball and all the other points are getting further away, but it’s happening in a uniform way. (The Hubble parameter is something like the rate at which air is added to the beach ball.) Now, run this beach ball backwards through time – it shrinks and shrinks until it becomes a single point, where all points overlap – every point is the centre of the beach ball universe. Run this forward in time again and ask: which point on the surface of the beach ball is the centre of this two-dimensional universe? And the answer is “all of them” and the universe should be uniform in its expansion properties.
Anything with mass can’t travel at the speed of light, but a massless particle, such as a photon, completes its trip instantly from its perspective. A photon is created, departs, and arrives at its destination simultaneously.
It’s also worth noting that it also experiences zero distance. If you’re willing to tie your brain in knots, a photon doesn’t exist. Instead, space-time flexes so that 1 point touches another, momentarily. Energy is transferred, and space-time recoils back. That flex would be mathematically identical to a photon traversing the intervening space-time.
There’s a reason we use photons however. Such twisted space is effectively impossible for our brains to usefully comprehend.
I don’t know if that analogy works, because from the perspective of an observer, a photon doesn’t travel instantaneously. It travels at the speed of light.
That’s why I said space-time, not just space. Generally worked with in the form of [X,Y,Z,iT] to make them all behave space like. Basically 2 4D positions become the same position. The fact that the 2 positions are displaced in time is almost incidental. The rules for the transformation however still have to collapse down to the same underlying measurements, so it’s a lot more complex than 2 arbitrarily points.
It also illustrates a funny bit of the logic of multicellular non-clonal creatures: the germ line is the species. The other 99.9…% of you is just a fancy delivery mechanism, so it makes sense to add something seemingly super impractical to the anatomy if it slightly helps the sex cells.
What I remember from watching discovery years ago is simply that “time” will slow down so that it takes longer and longer for that object to reach the speed of light. This is the only kind of " time travel" that is theoretically possible.
Not really.
Take for example a star 1 light year from sun. If we start this theoretical machine, it WILL take 1 year for that machine to reach there. Same for 100 light years distance. That’s the amount of time it takes for light to travel that distance.
My main question, and the one that I initially came here to ask, is: if their ship continues applying the force that, under classical mechanics, was enough to accelerate them at 9.81 ms^-2^, would the people inside still experience Earth-like artificial gravity, even though their velocity as measured by an observer is now increasing at less than that rate?
Relativity says yes. There’s no absolute speed, only relative speed; within the local reference frame of the ship, everything will continue to work normally, including the force experienced due to acceleration.
My understanding is that a trip taken at the speed of light would actually feel instantaneous to the traveller, while taking distance/speed of light to a stationary observer.
The ship is not actually going to reach the speed of light (as seen by an outside observer) though. The faster the ship goes, the more its (observed) mass increases, and the 9.8m/s² acceleration will have less and less of an effect. But to the people inside the ship, it appears as though they can accelerate indefinitely, going faster and faster at their steady rate of acceleration. Due to relativistic effects, it’ll never look like they are passing any objects outside the ship at more than the speed of light; instead it will appear as though the distance they have to travel is compressed, so they don’t have to travel as far.
You’re not allowed to have any way to determine an absolute speed. If your perceived acceleration were to vary (for a constant thrust) depending on your speed, that would give you a mechanism to determine absolute speed, but absolute speed doesn’t exist in relativity.
Rather than “nothing can go faster than the speed of light,” given that we’ve just determined that absolute speed doesn’t exist, the next rule is instead: you are not allowed to observe anything travelling faster than the speed of light relative to you, and relativistic effects will ensure that this is so.
A minor nit pick. It’s worth noting that increasing mass is an inaccurate view. It works in the simple examples, but can cause confusion down the line.
Instead, an additional term is introduced. This term, while it could be combined with the mass, is actually a vector, not a scalar. It has both value and direction, not just value. This turns your relativistic mass into a vector. Your mass changes, depending on the direction of the force acting on it! Keeping it as a separate vector can improve both calculations and comprehension, since comparable terms appear elsewhere (namely with time dilation and length contraction).
Touching on the second question, since the ship would never actually reach the speed of light, the trip would not seem instantaneous to the people on board. However, the trip would seem much shorter to the people on board than it would to external observers. The people on board the ship would experience length contraction in the direction of travel making their destination closer to themselves, while external observers would notice the people onboard the ship moving slowly, ie, experiencing time at a reduced rate. Either way, the effect is that the people on board perceive the trip to be much shorter (in terms of both distance and time) than an external observer watching their ship. In principle you can get the perceived length of the trip (both distance and time) to approach but not equal zero, though in practice this would involve killing everyone on board and destroying the ship (and maybe even the galaxy).
I agree with the other commenters that the people on board will experience a consistent acceleration of 9.81 m/s² in your described scenario. It might help, conceptually, to imagine an external observer watching someone on the ship jumping up and down at this near-light speed, taking into account the severe time dilation they’d be experiencing: The difference in perception comes because, from the external observer’s point of view, the person on the ship is moving in extreme slow motion.
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