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Posts posted by gib65


How does the light from distant stars get to our eyes?
Maybe it's just my misunderstanding, but the odds of seeing a distant star seem astronomically low. Here's my understanding of how it works. Please let me know if I've got anything wrong.
The light emitted from stars are photons. Photons travel through space as waves. These waves are no different than the waves of any other particle described by the wave function of quantum mechanics. That is to say, they describe the locations where the particle is most likely to be if one attempted to measure their location.
By the time a photon from a distant star reaches my eye, the wave spans a vast amount of space. I can see the star from locations on Earth thousands of miles apart. I can even see the star from the Moon. Or from Mars.
But according to quantum mechanics, when the wave function collapses, it collapses to a much more specific location. This is where I might be misunderstanding. When we see something, the light from that thing is stimulating a molecule in either a rod cell or a cone cell in the retina which triggers an electrical signal to be sent from the eye to the brain. Does this count as the wave function of the photon "collapsing"? Is the molecule in the rod/cone "absorbing" the photon?
If this is right, then out of all the places and things that could have collapsed the photon's wave function throughout it's journey from the star, this one molecule in my eye happened to be the one. That seems astronomically improbable. Now, I realize the star is not just emitting one photon. It emits billions or trillions of photons every second (right?). Is this what makes up for the improbable odds? The probability still seems extremely low. The star may emit billions or trillions of photons but it is billions or trillions of miles away, so that's a huge number of things that could interact with the photon and cause it to collapse. Furthermore, it doesn't seem to matter where I stand. If I move an inch to the left, I can still see the star. If I move an inch to the right, I can still see the star. That means there are photons coming from the star for every inch of ground I could be standing on, and for every inch of ground I could be standing on, there are enough photons such that out of all the things that could cause its collapse, one of them is always guaranteed to collapse on this one molecule in my eye (and more likely, there are enough photons to collapse on several such molecules since seeing a star most likely requires several rod/cones in the eye to be stimulated).
Are there really just that many photons being emitted by the stars in the sky? Or am I misunderstanding something in the above?
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I've heard of a goldilocks zone for solar systemsa region around the solar system's sun that's not too close and not too far away from the sun for life to thrivebut is there a similar concept for galaxies? For example, could a solar system capable of sustaining life exist deep within the central bulge of a galaxy? Or would that region be too hot? Similarly, could a solar system exist far outside a galaxy and still be capable of sustaining life? It might be significantly colder in the empty space between galaxies but the solar system's sun could provide all the heat life needed, couldn't it?
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I'm familiar with the prediction that global warming is melting the polar ice caps and glaciers around the world causing the oceans to rise. But wouldn't global warming also cause the oceans to evaporate by a certain degree, thereby off setting the rise in ocean levels? When scientists make predictions about how much ocean levels will rise, do they take into account rates of evaporation?
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Hello everyone,
I have a theory about drug tolerance that I'd like some feedback on (is there support for it? Against it? Can anyone tell me if there's reasons it might to true/false?). It goes a bit deeper than the already widely accepted their of receptor upgrading/downgrading (and note that it's not a competing theory but builds on it). The theory of receptor upgrading/downgrading, as I understand it, is that neurons will shed their receptors (downgrade) if they detect (somehow) that those receptors are overstimulated, and will build more receptors (upgrade) if they detect that those receptors are understimulated. As I understand it, this happens with both drugs and naturally occurring neurotransmitters. If a drug finds its way into the synaptic gap and binds to receptors therein, then after a while those receptors will start downgrading to return the level of activity to normal. If the drug somehow blocks naturally occurring neurotransmitters from stimulating the receptors, then after a while those receptors will start upgrading to return the level of activity to normal. This can happen directly or indirectly. A drug can indirectly increase the amount of stimulation at receptor sites by, for example, increasing the rate at which naturally occurring neurotransmitters are released into the synaptic gap. This is the case with dextroamphetamine. It increasing the amount of stimulation by entering into the synapse and pushing out more dopamine into the synaptic gap than usual, and the dopamine stimulates the receptors directly. Likewise, a drug can indirectly decrease the level of stimulation of receptor sites by, for example, increasing the amount of stimulation at a neuron whose function it is to inhibit the stimulation of the first neuron, thereby causing less naturally occurring neurotransmitters to enter into the synaptic gap of the latter.
But where my theory comes in is to answer the question: how does upgrading/downgrading work? What is the mechanism by which it happens? My theory is this: upgrading is constantly happening all the time. It's a naturally occurring behavior of any neuron. Leave a neuron to its own devices and over time it will produce more and more receptors on its surface until it can't anymore. However, receptors are fragile. Too much stimulation can destroy them. So with enough stimulation, the rate at which receptors are destroyed will balance the rate at which they are produced, thereby keeping the number of receptors in an equilibrium state. Moving above that equilibrium will, therefore, imbalance the rate in the direction of destroying more receptors than are created, thereby resulting in downgrading. Moving below the threshold will imbalance the rate in the direction of allowing more receptors to be created than are destroyed, thereby resulting in upgrading.
That's the theory. Is there anything too this theory? Is there anything in the scientific literature that either supports this or discredits it? Does anyone have any reasons to agree? Reasons to doubt? What are those reasons either way?
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Desensitization refers to neurons getting tired of firing. It happens over the course of minutes. They just need to rest for a few minutes and they are ready to fire again.
Tolerance, on the other hand, is the process by which neurons attempt to adjust to over or understimulation by increasing or decreasing the number of receptors being stimulated. This happens over the course of several days or weeks, and takes about a week to recover from.
Here's a link: https://www.pharmacologyeducation.org/pharmacology/desensitisationandtachyphylaxis
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Can one become tolerant to one's own neurotransmitters? I know this can happen with a drug like dexedrine. Dexedrine increases the supply of dopamine in the synaptic gap, and based on my own experience, one can develop a dopamine tolerance at these sites. But what if you were in an environment in which you were being constantly stimulated by things which resulted in dopamine releases in the brain. For example, what if you were a video game addict. I'm told that the joy of playing video games comes from all the little dopamine releases that the game provides. Would you develop a dopamine tolerance even then?
2 
Thanks for the replies everyone.
So what's involved in creating a vaccine?
Also, CharonY said that the number of deaths would be much higher if we were to "rip the bandage off now". I can see how the death rate would be higher, but why the absolute number of deaths. Is a virus that spreads slowly less deadly than a virus that spreads quickly?
0 
I don't get the strategy the world is using to fight COVID19. I get that social distancing and social isolation are ways to reduce the chances of catching and spreading COVID, but what's the ultimate goal? Are we trying to eradicate the virus? Prolong the eventuality of catching it? Are we waiting for a vaccine? What's the criteria for considering the pandemic over so that we can resume our lives?
I don't understand social isolation in particular. It's almost like we think that by isolating ourselves, we're going to be living as isolated "family units" so to speak, such that the only contact we have is with our immediate family and zero contact with the rest of the world, like this:
But this is an unrealistic picture. No group of people can completely isolate themselves from other groups. We all have social connections with people outside our immediate families/groups that we cannot completely isolate from. For example, I'm divorce with a couple children. I work from home. Not being with my children is out of the question. So one might *think* that my little group consists of me and my kids living in our little apartment all alone until the pandemic lifts. But obviously my ex cannot be away from the children any more than I can. So while I have the kids for one week, she gets the kids for the next week. That connects my small group with her. And of course, she can't isolate from her boyfriend who lives with her. And her boyfriend has family too. He can't isolate from them. And his family has spouses of their own. And their spouses have their own families. And the social ties go on and on like this. The picture ends up looking more like a web than isolated bubbles of nuclear families:
This means there is always going to be a path through which the virus can spread to anyone in society.
So if the goal is to quarantine the virus within only those groups that have it until it runs its course, I think this is a poorly thought through strategy.
Is the goal just to prolong the spread, avoid the inevitable for as long as possible? Wouldn't it be better to rip the bandage off quickly and get it over with?
The only realistic goal I can think of is to slow the spread as much as possible until a vaccine is invented. But how long will that take? I guess this is my question (after the question of: what are we doing?). What does it take to create a vaccine? And how long will that take? Once it's created, do we just go out and get it? How will it be delivered to each individual without risking catching a live version of the virus by virtue of having to be in contact with people? And once a person gets the vaccine, is that it? Is he/she free to go about society and resume their life? Or do they still have to isolate because they could still be a carrier?
I'm just not sure what the goal here is, or how we know when we've achieved it.
1 
So would you say that the sequence (0.9, 0.99, 0.999, ... , 1) is not a sequence since 1 can't be mapped?
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Just now, Strange said:
Surely this is true of any infinite sequence?
Well, the point is, it has a last without a second last.
0 
Hello,
I'm in a online debate with someone about some deep mathematical concepts. My opponent was trying to convince me that you can have a sequence of numbers for which there is a first element, a last element, but no second element and no second last element (where the sequence contains more than 2 elements). I thought that was absurd until he gave me an example: all the real numbers between 0 and 1.
It definitely has a first member (0) and it definitely has a last member (1), but after 0 there is no "next" real number. Likewise, there is no real number that comes just before 1. Yet there are obviously real numbers between 0 and 1.
That stumped me until I figured that couldn't possible count as a sequence because sequences must consist of welldefine discrete elements and real numbers aren't welldefined or discrete. I thought that was a terrible way of putting it, so I looked up the definition of sequences online and the key word I found was "enumerable". The members of a sequence must be enumerable. And I don't believe the reals are enumerable.
But then he came up with this other example: take the sum \(\sum_{i=1}^{n}\frac{9}{10^i}\). If you define each member of the sequence as the value of this sum for every value for n > 0 and order them by each incremental value of n, then you will have the sequence (0.9, 0.99, 0.999, ...). And if you allow n = \(\infty\), then we know this sum equals 1. Therefore, 1 is the last value in the sequence. Therefore, the sequence starts with 0.9 and ends with 1. Furthermore, each member is welldefined and discrete. We know each member by the sum \(\sum_{n}{i^1}\frac{9}{10^i}\) and the value of n. Yet, it has no second last member.
Is this a legitimate example of a sequence?
0 
Hello,
I understand that scienceforums.net is not about giving medical advice, but I have some questions about how drug tolerance works and I'm wondering if anyone knows about a good source that will answer my questions.
Here's some example questions:
1) Can I expect that the time it takes to get over tolerance is relatively equal to the time it takes to become tolerant? So let's say it takes 4 days to become tolerant to a drug at a specific dose. Would it then take 4 days to undo the tolerance if I abstain from the drug for those 4 days?
2) Would tolerance buildup occur at the same rate if I consumed a certain dosage of a drug once per day vs. consuming half that dose twice a day. For example, suppose I consistently had 2 cups of coffee every morning, one immediately after the other. Compare that to having 1 cup every morning and another cup in the afternoon. Would I become tolerant to caffeine at the same rate in both cases? Or would it happen quicker in one case or the other?
3) Can I avoid tolerance buildup by taking a drug at a low enough dose each day?
4) Does tolerance buildup begin to occur after just one consumption, or do I have to consume a drug several times in a row before tolerance begins to occur? If so, how many times in a row?
If anyone can answer these questions, great! But if it is inappropriate to answer them hear, I would appreciate being directed to another place where I can get my questions answered. Thank you.
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What about the imaginary number, the square root of 1? < That's said to be imaginary, therefore not one of the reals. Does that make it a hyperreal? Do the hyperreals include imaginary numbers?
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10 hours ago, studiot said:
A cardinal number is a measure of the size of a set that does not take into account the order of its members.
An ordinal number is a measure of the size of a set that does take into account the order of its members.
Here's the youtube video where Michael Stevens talks about cardinals and ordinals:
Note that at 7:55, he explains how only cardinals refer to amounts. Note the statement: "Omega plus one isn't bigger than omega, it just comes after omega."
Another question I have is: infinitesimalsare they divisible?
In other words, is an infinitesimal defined as the "smallest possible number" (in terms of magnitude, not how far below 0 it is)? Or is it more of a set of numbers that are infinitely smaller than any real number?
I would think its a set. Just as for any infinitely large hyperreal number R, you can have R + 1, R + 2, etc., and R  1, R  2, etc., I would think for any infinitely small hyperreal number e, you can have e/2, e/3, etc. or 2e, 3e, etc. That is, e doesn't represent a limit to how small numbers can get, it just represent an infinite amount of division you would have to do on a real number to get to it. That means that no matter how many times you multiply e, you will still only have an infinitely small hyperreal number.
What happens if you multiply the infinitely small hyperreal number e by the infinitely large hyperreal number R? Do you get a real number?
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5 hours ago, uncool said:
Before I answer some of these questions, I'd like to note that it may be easier if you learn how the hyperreals are defined formally. However, the formal definition is somewhat complex and based in advanced set theory (namely ultrafilters and the existence of free ultrafilters on the natural numbers).
Yes, the definitions and explanations on the web are very complex. They just confuse me. I'm a better learner if I just ask someone and they explain it in plane English.
5 hours ago, uncool said:Yes. In fact, every real number is also a hyperreal number (if you have an exacting philosophy of math, the statement might be more accurately stated as "Every real number has a hyperreal counterpart", but I'm going to ignore philosophical issues for now). Slightly more formally, we really consider the hyperreals as an extension of the real numbers  the set of hyperreals includes the real numbers, and then some.
Ah, but you're essentially saying the 0 of the hyperreals is just the 0 of the reals, correct?
5 hours ago, uncool said:You can create "hyperhyperreals" through a similar formal process to the way the hyperreals are constructed. However, 2*R isn't special  it is "merely" hyperreal, in the same way that 0 is "merely" real. You can do any formal algebraic operation on the hyperreals that you could do on the reals  add them, subtract them, multiply them, etc. Formally, they are an ordered field just like the real numbers.
But is it correct to think of 2 x R as twice the distance from 0 as R is from 0? If so, and if 2 x R is just another hyperreal number, then is it fair to say that there can be infinite distances between hyperreal numbers (assuming both hyperreal numbers are greater than any real number).
5 hours ago, uncool said:I strongly suspect that you misunderstood something here; the ordinals, cardinals, and hyperreals are all in some way or another generalizations of the idea of infinity. All of them have some idea of "greater than infinity".
...
If I had to give an answer, I'd say that they are like quantities in that they can be added, subtracted, multiplied, divided, etc. However, I'd more say that ordinals, cardinals, and hyperreals are simply attempts to extend different collections of properties of finite things  in the case of ordinals, ordering; in the case of cardinals, counting; in the case of hyperreals, the arithmetic.
Do you mean to say even the cardinals can be extended passed infinity? As in, there are cardinal numbers (representing quantities) greater than infinity?
0 
Hello,
I've been getting into the concept of hyperreal numbers lately, and I've got tons of questions. What I understand about the hyperreals is that they are numbers larger than any real number or smaller than any real number. I'm sure you can imagine how counterintuitive this sounds to someone like me who's new to the concept. It's like talking about numbers greater than infinity. I always thought that was impossible. So it shouldn't be surprising that someone like me would have a ton of questions. I'll start with a couple.
1) Assume that R is a hyperreal number greater than any real number. What does 2 x R equal? It's clear what 2 x n means where n is a real number because there is a 0 value for referencei.e. 2 x n is a number twice the distance from 0 as n is from 0. But do the hyperreals have their own 0 point? How could they if they are greater than any real number (I realize some hyperreals are smaller than any real number, but for this question I'm only focused on the infinitely large hyperreals)? If 2 x R means twice the distance from 0 the real number as R is from 0 the real number, the you get a number another infinite distance awaysort of like a hyperhyperreal number. < Does that make sense? Do the infinitely large hyperreals have their own infinity beyond which are numbers that are hyperreal even to the hyperreals?
2) I remember watching a vsauce episode on youtube where Michael Stevens explained the difference between cardinals and ordinals, which as I understand it is the difference between numbers that represent quantities and numbers that represent orders. He explained that while there is no cardinal number greater than infinity, you could talk about ordinal numbers greater than infinity. He didn't explicitly link ordinals to hyperreals but it seemed like the same idea. He stressed that since ordinals don't stand for quantities, you cannot use ordinals to speak of "how much" something is, but simply whether they come "before" or "after" another number. Is this true of hyperreals as well? If so, this would seem to imply that there is no 0 point on the hyperreal number line as that would mean you could quantify any hyperreal number R (the ones greater than infinity). It's quantity would just be how many whole hyperreal numbers it is away from "hyperzero" (just as we say the number 5 represents the quantity of whole numbers it is away from 0). But if there is no such "hyperzero" number, then there isn't a reference point relative to which we can say "how much" a hyperreal number (greater than infinity) represents (except that it's greater than any real number). We could still quantify the difference between any two (greater than infinity) hyperreal numbers. So we could say R+3 is 3 greater than R, but without knowing how much R really is, we don't really know how much R+3 is either. So I guess the question is: should hyperreal numbers greater than infinity be thought of as ordinals onlythey represent orders of number, not quantitiesor is there a way of talking about their quantities as well?
I'll stop there for now. Thanks for any forthcoming responses.
0 
Why isn't the universe just a big soup of chemicals? Why is it that when we find water, or dirt, or air, we find it with more water, dirt, or air. In other words, why not just a single water molecule by itself? Why do water molecules tend to stick around with other water molecules?
When we look around the world, we don't see one uniform substance making up everythingwe see rocks, trees, sky, clouds, rivers, animals, and so on. In other words, different substances clumping together and staying separate from other substances. Take the sky for example. It is not only composed of oxygen, nitrogen, and carbon dioxide, but water molecules. Water molecules tend to clump together as clouds, separating itself from the rest. Of course, the rest of the moleculesthe oxygen, nitrogen, and carbon dioxideseem to stay evenly mixed (I think), but in general, there seems to be this tendency of molecules and atoms of one kind to stick together with other molecules and atoms of the same kind. The consequence is that, at the macroscopic level, we see objects made of specific substances separately from other objects made of different substances rather than a uniform soup of chemicals permeating everything.
Why do molecules and atoms do this?
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Thanks very much Nevim, those are good links
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Hello,
I remember reading an article a long time ago about the tendency of people to disagree with depressed people. So if a person suffers from depression, people are more likely to disagree with that person's statements and opinions. It doesn't seem to matter what those statements or opinions are (positive or negative, offensive or flattering), and it doesn't seem to matter whether the depressed person makes their depression evident or acts as if they are happy.
I can't find that article. I can't seem to find any research on any studies that would support the above. No doubt, my google search skills aren't as refined as they could be.
I'm wondering if anyone can corroborate with the above or link me to some research that supports the above (or perhaps disproves it).
Thanks.
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Thanks everyone for your responses.
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They say that to get over a fear, one has to expose themselves to that fear over and over until the fear goes away (assuming of course they experience no adverse effects). For example, I have a fear of public speaking. I'm trying to get over it by going to public speaking sessions. For example, toastmasters. I've been going for the past several months and I'm not experiencing the effects I was expecting. I still get very nervous speaking in front of crowds and it shows.
What I'm wondering is, is there any research to show that to get over a fear of public speaking (or any phobia), one has to expose themselves to that fear at a sufficient frequency? I mean, to take a ridiculously extreme example, I don't think one would ever get over a fear by exposing one's self to it once a year. But do it once a day, then maybe.
I go to Toastmasters once a week and I'm wondering if that's not frequent enough. I'm wondering if it should be more like twice or three times a week.
Has there been any research to show that the frequency with which one is exposed to a certain fear makes a difference? In particular, is there a frequency below which it has no effect whatsoever?
0 
Thank you Strange,
What is the earliest that scientists can "see" the state of the early universe? I mean, I know scientists can look at the early universe by observing the CMBR in deep space, but this happened much after the first picosecond. Can they actually "look" that far back, to the first picosecond, or is it all based on mathematical models at that point?
0 
I am told that scientists don’t know what happened within the first picosecond of the universe.
If this is true, I have a question:
How do they know it was a picosecond? I guess the assumption is that if you extrapolate the current expansion of the universe back to its origin, you don’t have to assume anything unusual in the first picosecond. But what if scientists could somehow see into the first picosecond? Is it possible that what they find is that it was way longer than a picosecond? In other words, the universe originally started expanding very slowly, and for the longest time didn’t grow much bigger than its original size, and then for some reason went through the explosive expansion scientists are familiar with?
0 
Hello,
I'm wondering if there are any books out there on the subject of finding substitutes to drugs. Specifically, I'm looking for substitutes to caffeine. It doesn't have to be other substances either like yerba mate or probiotics, but lifestyle changes or changes in perspective as well.
I figure that finding substitutes to drugs is such a common approach to overcoming substance abuse that there must be tons of research on it. < That's what I'm looking for.
Can anyone help me out? Thank you so much.PS  I realize this is not the place to ask for medical advice (or any kind of advice) so please take this as a request for information resource (books, articles, studies, etc.). Thank you.
0
How does the light from distant stars get to our eyes?
in Astronomy and Cosmology
Posted · Edited by gib65
Not along my direct line of sight to the star, but remember that I'm thinking of the photon as a wave, which means it propagates out in all directions, like an ever growing sphere. In that sense, literally everything is in its way. If any one particle in the path of the sphere capable of absorbing photons happens to absorb it, then the ones in my eye won't. My eyes are competing with an unimaginable number of things. Even an object behind the star (opposite of me) could potentially absorb the photon, meaning, in a manner of speaking, that even objects behind the star can "blocked" my view of it. Of course, if something gets that photon before my eye does, there are an unimaginable number of photons left for my eye to get. The main question of this thread is: are those (unimaginable) numbers comparable such that one shouldn't be surprised that one can still see the distant stars.
"Probably also yes."
I wholeheartedly agree. 😁