Cmac22

In reply to AlphaZNV: Thanks for your input. However, I do not think that some of what you have said is correct. you can think of the body as a system, with the skin as its external barrier, and the liquid you are swimming in as the external environment. The 'scale' does not effect the dynamics in the way you suggest. The pores do not change because the volume of the external liquid is so much larger. Similarly, volume does not make a difference, per say. What matters is the gradients between the internal system (body) and the external environment, across the skin. Thus it is not volume that matters, but the concentration of solutes in the body and external liquid. Diffusion is governed by the same laws in both cases, save for things like active transport etc. inside the body. But in both cases the 'scale' is at the molecular level, i.e. the movement of water molecules and ions from one area to another. However, some of the things you said about different factors and variables made me think, and here is what I have found. The skin consists of 3 main layers. From internal to external: hypodermis, dermis, epidermis. Blood vessels only extend to the top of the dermis layer. Thus, epidermis cells die as they migrate outwards because they have no access to blood vessels. As they die, the cytoplasm (and this water) is removed from the cells and replaced by the protein keratin. The epidermis functions as a 'waterproofing' layer. The epidermis is typically 25-30 cells thick. the outermost layer(s) is called the stratum corneum, and is largely responsible for protection from the environment. It is an effective barrier against most nano sized particles. These cells are also surrounded by various proteins, which add to their adhesive and barrier functionality. 'Trans-epidermal water loss' or 'insensible water loss' is the term use to describe the loss of water to the environment via evaporation. (obviously evaporation is a little bit different, but I think the same principles still apply). The epidermis functions to minimize water loss with a low permeability. However, organisms have little control over 'trans-epidermal water loss' What I take from these things is this: The skin functions to minimize the rate of diffusion/osmosis across it. It does this by blocking the movement of most nano sized particles, and by doing things such as keratinization. as you move to the outward layers of the epidermis, the cells contain less water. These things function to minimize the movement of water. There is little water to move, there is no blood circulation so there is no 'convection', and keratin help absorb/retain water(i think?). Overall though, this does not really answer my question. It only shows that the movement of water through the skin is very slow, ostensibly. However, water does move through it, and defects in skin can cause dehydration issues etc. So how slow is slow? How long would you have to sit in pure water or some very solute heavy solution for effects to become dangerous, if ever?

I was not certain where to post this, sorry if this is not the correct place. During breakfast the other day my friend randomly asked a question somewhere along the lines of "If you were to bathe in a pool of syrup, would you loose water through your skin?" i.e. through diffusion/osmosis. I found I was not able to come up with a satisfactory answer. Ultimately, I decided no, that there must be some barrier to prevent this, but i was not certain at all about this. My thought was, that if this was true, it would also mean that you would swell with water if you were swimming in a lake, which I feel does not happen, although I am not sure about this either. After recently searching google, I still have no answer. The information I found was vague, ambiguous, and sometimes controdictory. Thus, I have turned to the forum to get a satisfactory answer. Is water free to flow through your skin like this? If you sat in syrup (or salt water with a high enough concentation) for long enough, would you become dehydrated? would you die from it? Thanks!

but if mass and energy are similar, that is mass can be converted to energy, then cant energy be converted into mass? hence gravity?

Hey, these questions probably will seem dumb to you but im kinda learning stuff on my own here so help would be nice. i was just trying to understand the whole E=mc^2 equation. i understand its about the energy in atoms and stuff, but does that mean that energy can have mass? what i was really wondering is does energy cause gravity? can light cause gravity? see, dumb questions heh

Thanks a lot Martin. I understand it much better. i appreciate the time you spent to reply and the clarity of your post!

it seems like you have some interesting ideas there. i didnt understand some of it on the first pass but ill look over it again when i got more time. thanks for the input!

i was watching the TV show the universe, the new episode on gravity. in it they show what would happen if you built a hole through earth and put in a kind of transport car that ran off gravity. i think it was assuming like no air resistance or something but they were saying that it would go all the way through and stop on the other side. but the cool part was this. the time it would take to go straight through the earth to the other side is 42 minutes. but also the time to go from one city, to any other city, even if it is not straight through the earth, is 42 minutes! i dunno the conditions for this... like no air resistance and minimum serface resistance.. probably like mag lev or something. so it would take the same amount of time, 42 minutes, to go from seattle to paris, and to go from seattle to new york. i think thats pretty cool! but when i was watching this i had a question. if you are inside the earth while going straight through the center, say 1/2 way to the center, does the fact that you are inside the mass of the earth change anything? by this i mean... well since your passed a lot of earth there is less below you, so even though gravity is stronger because you are closer to center, would it be stronger if you were the same distance away from an object of the same mass with a density that would put you outside of that object? or is the only thing that is importaint is the center of mass or center of gravity? i hope that makes sence heh.

hehe, did thought exist before man!

thanks for the links inow. but yea i dont think a star could get even close to large enough. also i found that the largest know black hole is actualy around 11 billion solar masses. thats big heh... i suppose depending on the size those theorys seem reasonable. i guess the biggest black holes would be from galaxys that merge into several galaxys probably. and the smaller ones possible from just their own galaxy or one more.

i know im a bit late but perhaps it may have been the gamma ray burst afterglow talked about here http://www.astro.ucla.edu/~wright/cosmolog.htm and in more detail here http://www.nasa.gov/home/hqnews/2008/mar/HQ_08086_Swift_Detects_GRB.html im not sure how long the afterglow would remain visible but i believe they can last for days or longer... who knows eh scratch that, i dont think it would be visible for that long

so i was going over the Lineweaver and Davis' Scientific American article Misconceptions about the big bang and there were a few parts i could use help understanding. specifically having to do with the hubble constant. i dont understand how it changes. the article says: "In particular, the constant is proportional to the rate of increase in the distance between two galaxies, divided by that distance." im confused at what this means. in an example, if something beyond the hubble distance sent light towards earth, the hubble constant changes? and so we eventually can see the light? basically how does the constant expand? also later in the article it says: "If light from galaxies receding faster than light is to reach us, the Hubble distance has to increase, but in an accelerating universe, it stops increasing. Distant events may send out light beams aimed in our direction, but this light is trapped beyond the Hubble distance by the acceleration of the expansion." so...now the hubble distance doesnt increase anymore but it used to? one more question from the article: "This reasoning changes if acceleration is not constant, as some cosmologists have speculated. If the acceleration itself increased, it could eventually grow strong enough to tear apart all structures, leading to a “big rip.” But this rip would occur not because of expansion or acceleration per se but because of an accelerating acceleration." is there any newer info about this. is the acceleration accelerating? i remember watchin a show that talked about the big rip as the end of the universe but i dunno how accurate that is comments are always appreciated

well call him up! lets get it goin again

im not quite sure what you are asking here. first... 1000 mass i suppose we can just make that kilograms... but 10,000 (rotations per minute) could mean anything! it depends on the size of the object and the size of the orbit and so on, or axis if u want to rotate it on an axis. and what do u mean gravitational change!? change relative to what? do u mean to simulate gravity inside a spacecraft by rotating it? i think then u would be talking about centrifugal force, which isnt exactly a gravitational change but i suppose would feel similar in this case. or do u mean the gravitational force of the object itself?

Im not sure but i believe gravitational waves have to do with acceleration specifically. if an object is changing speeds or direction, hence exceleration, it will give off gravitational waves...for the most part. this is just from my reading from wiki so i could deffinatly be wrong but i suppose it is worth a look... it seemed to be reasonable http://en.wikipedia.org/wiki/Gravitational_wave But back to the original...or general theme i suppose... so...dark matter doesnt iteract at all with regular matter besides gravitationaly? i mean its hard to say because its unknown what dark matter is i guess. i think that dark matter would fall into black holes more often then it does stars, if its even possible. but for a black hole, or supermasive, that is growing in size, wouldnt it expand to consume the dark matter, rather than the dark matter falling into it? . then again i dont know much about dark matter... but i feel that there is probably a connection between dark matter and black holes.

so i was looking online for info into this question and there wasnt really a whole lot. most of the stuff i found was a bit old and more of speculation. i suppose its mostly speculation anyways but i was curious if there was any newer info about them. how would something millions and sometimes a billion times the mass of the sun come into being? My obviouse guess would be that the occasional planet or star would get to close and get pulled in, along with all the gas around and such. but how often is this? i suppose over millions or billions of years it happens. But the biggest black hole im aware of is about 4 billion times the mass of the sun. that means that in a universe 14 billion years old, if it did form then, it would need to grow by one billion solar masses every 3.5 billion years. that means one new solar mass pulled in every 3.5 years on average. does that seem unlikely or is that possible... i guess it must be but... where does all that mass come from!? i was just reading an article about the milkyways supermassive black hole from 2003 "Only hints of spin have been noted from supermassive black holes, each of which is thought to form and evolve hand-in-hand with the development of the galaxy in which it sits." "depends on the curvature of space around the black hole, which also depends on how fast the black hole is spinning. A spinning black hole drags space around with it and allows atoms to orbit nearer to the black hole than is possible for a non-spinning black hole" http://www.space.com/scienceastronomy/mystery_monday_031124.html this is another one from 2005 talking about its size http://www.space.com/scienceastronomy/051102_black_hole.html one question i have from reading these is does spin effect its gravitational pull. in the second quote there it talks about. how does the spin effect its pull? and what causes this spin? is it the fact that an entire galaxy is spining around it or something else? alot of stuff in there your time and comments are greatly appreciated!

yea i get that. but then again, supermassive black holes tend to be larger, some as large as millions or billions of solar masses.... so i would say that is quite different then stars gravity. and yes i understand that it has a smallar radius and is more dense. but when objects come too close to black holes, and then get pulled in passed the event horizen, the objects mass is added to the black hole entirely...i think? i mean if not even light can escape then i wouldnt think any matter could. im not really sure where i am going with all of this, i was just interested in the formation of supermassive black holes. i looked on the internet but there wasnt really that much i could find. as far as i know, there supermassive black holes are not fully understood, if even half understood. one thing i was thinking of was that, if anywhere, the most likely (however unlikely it is) for planets and stars and such to collide or come in close contact would be at the center of the galaxy. with many objects being close together and moving at high speeds, collisions or distortion of stars by gravity would keep feeding the black holes to get larger and larger. but that still doesnt really answer my question of why there are super massive black holes at the center of galaxys in the first place. it certainly cant be called coincidence. and it must have something to do with the galaxy itself or its formation i feel.... i dunno

hmm, i guess that makes some sence. but then again, if theres a supermassive black hole in the center, the gravity wouldnt be zero would it? so what kind of a difference would it make between the two? the galaxy would be denser or somethin? i dunno

Thanks for the replys, they helped some. but i still am confused. the reason i am so curious is because i was just thinking about supermassive black holes in the center of galaxies in specific. im sure i have a lot of misconceptions here so i wanted some clearing up. i was thinking of gravity as a straigt line force kinda, which is probably wrong in the first place. but i was thinking that at the center of a galaxy all the gravity would be pulling strongest from that point, with all the gravity overlapping at that point and what not. but if you think of it as all the gravity pushing in the other direction then that means you have all the gravity of the galaxy pushing onto one point. so all this gravity would create so much...?pressure? ,or gravitational force, that it would cause a black hole to form at that point. perhaps out of a star that might have been pulled there or something but maybe a black hole made of energy or light or something else?... i dunno. does this make any sence? i mean, if Black holes are at the centers of all galaxies, i would think that black holes are a result of the galaxy being there, and not the other way around. or rather that as a result of a galaxy forming, a black hole was formed i dunno if any of that made much sence. but heres another question. does a galaxy need a central black hole to orbit around, or spin around. can galaxies just spin around a central point with nothing in the center? how would this work?

there is a lot about black holes that i dont understand but heres a few questions i was just thinking about: Are there back holes that arnt in the center of galaxies? i understand that black holes form from collapsed stars (i think). but is this proven? has someone seen a star collapse into a black hole? and if a star did do this wouldnt its gravitation eventualy create a galaxy around it? another similar question: are there galaxies without black holes at their centers? i dunno if there is a difference between supermassive black holes and just normal ones besides i suppose that one is "supermassive". are supermassive black holes formed differently? it just seems to me that if black holes are the center of all galaxies then are the galaxies themselves producing the black holes somehow? are the black holes a product of galaxies? or are galaxies a product of black holes? or is it neither? any comments/ideas would be great!

Im having trouble understanding your question but ill take a stab at it. I think this is what your asking but i could be completely wrong: out at night you see the moon setting. then the next day you see the moon again. how is this possible? Well, (if this is your question) then i think this is the answer though i might be wrong again haha. say your out at night and you see the moon setting at 9 PM. you go to bed and wake up the next day. you look outside around 10am or so and you see the moon rising. basicly the moon will be in the sky a bit less than 12 hours a day. so if it sets at night, it will be rising again and in the sky 12 hours or so later! i hope this answers your question! but again its rising setting times change constantly because it is also orbiting the earth like others said. the moons a tricky little guy

i c thanks a lot!

yes, thank you, that answers my question about how mass effects inertia and gravity. but it still doesnt answer (or maybe it does and i just havnt connected it yet) whether the two apples would pull together or not, as well as related questions

no that is not what i was saying. i was saying that we cannot communicate with someone, hence cannot learn from someone, if we dont yet know of their existance

Not really sure if this is the right place for this question but im sure you guys can answer it. For the question im going to use a hypothetical situation: say you have two small objects, like two apples, out it the middle of space very close to each other, and very far from any other object. because the closest objects are so far from these two apples, there would not be much other force (like gravity) effecting these two apples (right?). So my first question is would the gravitational pull from these two apples pull the apples together, or perhaps cause them to start orbiting or something? Or would Inertia prevent these two apples from pulling together? i Asked someone this and they said that the inertia would prevent the objects from pulling eachother together. That brought me to my second question: The way i understand it, both Inertia and Gravity are affected by mass. the bigger the mass the bigger the pull of gravity and the more inertia it has. So, if you were to expand the two apples to the size of say planets, then (i think?) the two apples would pull eachother together. But how is that possible if all we are chaning is the scale? because while the pull of gravity is bigger with the planet sized object, so is the inertia. is the answer that as mass increases, gravity increases more than inertia? if so what would determin the point at wich gravity overcomes inertia? Sorry if this is all completely wrong haha another possible answer to my own question might depend on the space between the two objects? i mean, if your scaling up the size of the objects than you also have to scale up the distance between them. so even with this distance scaling, what would happen?

im not fully sure what the initial question it. i suppose that, at this point, Humans are merely interested in whether there is other life out there, and advanced life at that. the value of communication would simply knowing of their existance. as far as interstellar war, it seems very unlikely. if there are other advanced life forms that are near enough to visit our solar system, then there must be many sutable planets around. in that case why bother destroying other life when you can simply move in to a vacant planet. as other said, if we found out of other life and began communicating, we probably would not simply send one lined messages but rather would continuosly stream data. and they would probably do the same back. if they were less advanced then humans then i would think we would attempt to help them advance their civilization. However there is the huge problem of language and technological barriers. perhaps there is data being streamed by the earth as we speak, but we dont yet have the technology to be aware of it and to access it.