Science desk
< January 26	<< Dec \| January \| Feb >>	January 28 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

January 27

Maximum number of isomers from asymmetric Diels-Alder?

Assuming that I am reacting an non-cyclic asymmetric dienophile with a non-cyclic asymmetric diene, what is the total theoretical maximum number of different isomers that I can get? My textbook says the answer is 8 because you will get two structural isomers each with 2 chiral centers (2^2), so each structural isomer will yield 4 stereoisomers, for a total of 8 stereoisomers between the two structural isomers.

However, I think the answer is 4 because although each structural isomer has 2 chiral centers, the dienophile could only approach the diene either above or below the plane, so only two possible stereoisomers could exist for each structural isomer. In my opinion, what the book is suggesting is that in order to get 4 stereoisomers per structural isomer, the dienophile would have to attack across (sort of like trans) the plane of the diene. Who is correct? Thanks Acceptable (talk) 01:03, 27 January 2012 (UTC)[reply]

When you say "from above or below", are you considering each face of each (both endo and exo)? DMacks (talk) 01:13, 27 January 2012 (UTC)[reply]

I'm not sure, but are you basically assuming the Diels-Alder#Cis principle? The "theoretical" may not mean products you really see. Wnt (talk) 01:50, 27 January 2012 (UTC)[reply]

The cis principle (or not following it) sounds like the concern about adding trans across the plane of the diene. But the diagram at that link is great...it's got 4 possibilities, and then you could also have another set of four where the two stereocenters in that diagram are inverted. DMacks (talk) 02:19, 27 January 2012 (UTC)[reply]

alien missionary

IF for example, alien from another galaxy came to earth and preach about christianity (of course not the same history as our bible but the same trinity and all of core beliefs in christianity) does that prove christianity? MahAdik _usap 01:58, 27 January 2012 (UTC)[reply]

No. It merely acts as another data point, making the Christianity concept more plausible. In itself it is not a proof. --Tagishsimon (talk) 02:00, 27 January 2012 (UTC)[reply]

It would lead to yet another round of re-interpretations of key Biblical passages, making the whole thing even less credible to me. HiLo48 (talk) 02:03, 27 January 2012 (UTC)[reply]

It wouldn't necessarily even make it more plausible. Presumably said galaxy-traveling aliens are capable of receiving our radio and television transmissions (either past or present). They could be doing it just to mess with us, for unknown alien reasons. One would have a lot of hypotheses to rule out before one assumed that the example given there was proof of the truth of Christianity. The devil's in the details. If we had records that another civilization, totally disconnected, had been doing the same thing for centuries as well — that would be more interesting. There would still be alternative hypotheses to rule out (perhaps the Christ mythos was delivered to us by aliens! or perhaps convergent evolution applies to cultural matters in ways we don't quite understand.) that would not necessarily be any more bizarre (in the sense of Occam's razor) than Christianity being true. --Mr.98 (talk) 02:10, 27 January 2012 (UTC)[reply]

I would say, "the question is ill-posed." "Christianity" is not a fact that can be proven or disproven. It is a complicated set of cultural norms, theological ideas, and social practices, as well as a series of stories and rituals. Within the realm of Christian thought, there are certain tenets - facts - that could be either proven or disproven. For example, it seems plausible that we could collect enough archaeological evidence to prove or disprove whether a person had been crucified. But we could not "prove Christianity." It's not subject to a boolean measure of truth or falseness. Nimur (talk) 02:15, 27 January 2012 (UTC)[reply]

I would just note as well that that the trinity is not actually a core belief in all forms of Christianity. Even Christ's resurrection is not. There is no single Christianity — it rather famously has a very large number of sects, some of whom disagree with each other quite sharply on rather core issues. At best one would be getting an alien espousing the beliefs of one or another sect of Christianity. --Mr.98 (talk) 02:24, 27 January 2012 (UTC)[reply]

Christianity may not be Boolean, but God is real - unless declared integer. Mitch Ames (talk) 08:49, 27 January 2012 (UTC)[reply]

Just out of curiosity, what factual references is the OP seeking? Because this is, after all, the reference desk. This disclaimer at the top states "The reference desk does not answer requests for opinions or predictions about future events." Please post the question at Wikipedia:Discussion forum which has no need for factual answers or references at all. Shit, why is that still a redlink... --Jayron32 02:30, 27 January 2012 (UTC)[reply]

I don't think it's an "opinion" to discuss the logic of the thing. Nimur at least has provided a reference on falsifiability; I've provided one on convergent evolution. Seems like there are some ways to provide references to this sort of thing. It's ultimately an epistemological question. --Mr.98 (talk) 02:35, 27 January 2012 (UTC)[reply]

Fixed your link Jayron. CambridgeBayWeather (talk) 04:11, 27 January 2012 (UTC)[reply]

Burn! Well played, my friend. Well played indeed. --Jayron32 04:48, 27 January 2012 (UTC)[reply]

The core beliefs of the Abrahamic religions include the tacit assumption that life exists only on earth (and in heaven). That realm is where everything in those religions occurs. There's no provision for Men from Mars, etc. Very unlikely that an alien species would have independently latched on to Christianity or any other earthly religion as such. However, it would be interesting to know what religion(s) they believe in, if any, to see if there's a cultural parallel. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:13, 27 January 2012 (UTC)[reply]

On the other hand, if 10-foot-tall, blue-skinned, sapient humanoids from another planet visit us to tell us to worship a mother goddess called Eywa then it is very likely that James Cameron is a prophet. Until then the sane part of humanity will stick to worshipping the Flying Spaghetti Monster or the invisible pink unicorn because we have proof that they actually exist. Von Restorff (talk) 07:32, 27 January 2012 (UTC)[reply]

What would be really interesting is if those aliens had somehow uncovered evidence to definitively prove (or disprove) the elements of standard religious beliefs, such as gods, an afterlife, and so on. Even forgetting the religion question, there is the question of how humans would react to definitive proof that there is life elsewhere. One of the important lessons of 2001: A Space Odyssey that doesn't get much attention is Heywood Floyd's comments about keeping the proof of extraterrestrials a secret until there can be time for "conditioning". For all the talk of E.T.'s, if they actually showed up it could be a highly traumatic experience for the world's human population. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:43, 27 January 2012 (UTC)[reply]

Oh, I am sure we would respond in a rational and dignified way. Von Restorff (talk) 08:04, 27 January 2012 (UTC)[reply]

"Testing shows the presence, not the absence of Bugs" ;-) [1] AndyTheGrump (talk) 08:55, 27 January 2012 (UTC)[reply]

Bugs, I don't think there's anything in the Bible which explicitly rules out extraterrestrials. It doesn't mention them, but it also doesn't really mention dinosaurs or saber-toothed tigers or North America or a lot of other things that believers have been able to more or less assimilate into that worldview. --Mr.98 (talk) 14:17, 27 January 2012 (UTC)[reply]

An equivalent of this thought experiment was carried out in the Middle Ages. Although they didn't have any concept of extraterrestrials, what they did consider possible were antichthones - people who lived on the far side of the world, separated from the Northern Hemisphere by impassable deserts and wide oceans. If anyone lived there, there were one of two massive spiritual problems - either these people were all damned, since no-one could teach them about God or, even if they were Christians, this would mean Jesus would have also appeared on the other side of the world (and would also fatally damage the Adam and Eve story). Sadly, the record doesn't appear to show the churches's reactions to finding that the New World was inhabited by people with no concept of Christianity. Smurrayinchester 15:50, 27 January 2012 (UTC)[reply]

This is all off topic, but saying it would disprove Adam and Eve sounds like circular logic, and their unfamiliarity with Christianity would be no different than people in Sweden or Namibia for quite some time. As for alien religious beliefs, well... we're assuming a lot there, such as that our thought and their thought are even potentially mutually comprehensible. There's no real substitute for data. Wnt (talk) 17:04, 27 January 2012 (UTC)[reply]

The arguments were that: a) Adam and Eve would be damaged because for the antipodes to be inhabited, the immediate descendents of Adam and Eve would have needed to cross the "torrid clime", which was believed impossible. Finding people there, they believed, would have meant two gardens of Eden. b) That people in Sweden weren't converted was thought to be our fault for not getting to them faster. Crossing the equator however was thought impossible, so they could never be evangelised, unless a second Jesus had appeared to them. Smurrayinchester 23:14, 27 January 2012 (UTC)[reply]

Well if you believed in one Garden of Eden and a truly impassable "torrid clime", then you'd have to believe the other side was empty, and no one could prove you wrong. It doesn't sound like a great paradox to me. In fact, most scientists would make the same statement any day of the week if you ask them if there are people on Jupiter, Gliese 581d, etc., with very much the same thought process. Wnt (talk) 00:30, 29 January 2012 (UTC)[reply]

The question was if there were other people there. And once it was discovered that they were, the paradox became more than just a thought exercise. — The Hand That Feeds You:^Bite 21:44, 31 January 2012 (UTC)[reply]

"Cat years" versus "Human years"

Is there a rational way to compare the "age" of a 17 year old house cat to a human? Edison (talk) 06:44, 27 January 2012 (UTC)[reply]

Well, it's certainly not a linear relationship. I Googled "cat years human" and got quite a few useful sites. They tend to suggest that a 17 year old cat is equivalent to a human of around 84 years old. HiLo48 (talk) 06:52, 27 January 2012 (UTC)[reply]

The tendency to transform age by some obscure formula doesn't make much sense to me. You may as well ask how to convert the weight of an eight-pound cat into human pounds; or the length of a 30 inch cat to human-inches. The units of time, mass, and length are the same for cat and human. The reasonable ranges that we expect to find if we measure a cat are different than those we expect for a human. On average, a healthy housecat should live for ten to twenty years. Our article, cat, and cat health, cite sources for "12 to 14" years as common life expectancies. Seventeen is old, but far from uncommon. There's no rational justification for saying that seventeen cat-years is any way similar to eighty-four years. They've orbited the sun seventeen times, not eighty-four; and they've been around for the same number of minutes and seconds as a seventeen-year-old human, horse, or block of cheese. You might say, "it's unusual for a cat or block of cheese to last 17 years," but I still don't see why that makes them "84" in "cat years" or "cheese years." Clearly whoever came up with this conventional wisdom for conversion had no concern for precision of timekeeping or proper dimensional analysis, and they had no qualms taking liberty with the definitions of common units of measure. Nimur (talk) 07:27, 27 January 2012 (UTC)[reply]

I was going to point out that 84 is double 42, then thought better of it, but now I think it's important to highlight that significant fact. HiLo48 (talk) 07:44, 27 January 2012 (UTC)[reply]

Hoping Nimur's answer is a least a little tongue in cheek - though this question is on the science desk so fair enough! I always assumed the idea of these 'conversions' is to help people put a pets age into context and help people understand what age their pet is in terms of expected lifespan. Remember that prior to the mass of knowledge that is the internet this information was not so readily available...I.e. in the old days saying '1 year for a dog is equivalent to 7 for a human' provides a handy ratio for people to use. ny156uk (talk) 08:11, 27 January 2012 (UTC)[reply]

If you're going to remember that 1:7 ratio, you might as well remember that a dog's average lifespan is 12 years. Unless you're a 3-year-old who needs to count fingers to remember numbers, I see no reason why 7 would be easier to remember than 12. Furthermore, human life expectancy has increased by more than a factor of two over the past two hundred years (although most of it is due to decreased infant mortality rate). 1/7 of 35 years is very different from 1/7 of 82 years. --140.180.15.97 (talk) 10:34, 27 January 2012 (UTC)[reply]

It seems unlikely that the human:dog years ratio would be based on a detailed knowledge of mortality rates; it is more likely to derive from a perception of what counts as old age or a good lifespan. In humans you can get this knowledge either from observation or from traditional sources such as the Biblical "three score years and ten"; in dogs, people who own animals can typically differentiate premature death from old age. These figures have not changed greatly through history. --Colapeninsula (talk) 10:52, 27 January 2012 (UTC)[reply]

From a scientific point of view, it may make no sense (unless trying to compare stages of life and trends in ageing between the two... not that I'm sure that that would be feasible); however from a pet-owner point of view, it makes quite a bit of sense. I think some people would feel much better thinking that their cat lived 12 years, which is like 84, a decent life, rather than thinking "poor cat, it only had twelve years". Falconus^{p t c} 12:00, 27 January 2012 (UTC)[reply]

The biggest problem is that, as HiLo mentions, it's not linear (ie. there isn't a constant number you can just multiply by). 7 humans years=1 cat year works reasonable well for total lifespan, but if you work in terms of sexual maturity, say, you get a completely different answer (cats reach sexual maturity at about 6 months, humans at about 15 years, which suggests the factor to multiply by is 30, rather than 7 - a very big difference). That means the idea of converting human years to cat years is never going to work. --Tango (talk) 12:38, 27 January 2012 (UTC)[reply]

Well, physically, humans reach sexual maturity faster than that, so the difference is not quite so much. And with human-grade health care they might live longer on average. Meanwhile, a cat's heart beats at only twice the human rate, a little less, 110-140, so they get fewer heartbeats. I once was compiling a table of lifespans, heartbeat rates, and calls for many species (mostly I was impressed by a chimney swift's impossibly rapid and expressive communications, which to me suggested a genuinely faster "subjective time"), and it seemed like there was a fairly general scaling law, but lost it all to a disk crash before I could get to the bottom of it. Certainly any result has to be an approximation of the zeroeth order. Wnt (talk) 17:19, 27 January 2012 (UTC)[reply]

I meant physical maturity - other measures of maturity (emotional, economic, social, educational, etc.) tend to take a lot longer. Even physical maturity can take longer than that, particularly for boys. --Tango (talk) 19:13, 28 January 2012 (UTC)[reply]

Count telomere size and the associated hayflick limit ..? Electron9 (talk) 12:48, 27 January 2012 (UTC)[reply]

Dr. vs. Ph.D.

From a legal point of view, if a person receives the grade "Dr." in a European county (e.g., in Germany), can this person then state in English publications (e.g., in his CV) that he has received a "Ph.D." or does he need to use the German title ("He received his Dr. degree at the University of ...")? In other words, is "Ph.D." the English translation of "Dr." or would "Ph.D." misleadingly signal that he has received a degree in a country where "Ph.D." is the typical name for that type of degree, i.e., not in Germany? 130.149.229.180 (talk) 14:41, 27 January 2012 (UTC)[reply]

Sorry, but we can't answer that 'from a legal point of view'.

The reference desk will not answer (and will usually remove) questions that require medical diagnosis or request medical opinions, or seek guidance on legal matters. Such questions should be directed to an appropriate professional, or brought to an internet site dedicated to medical or legal questions.

- Cucumber Mike (talk) 15:36, 27 January 2012 (UTC)[reply]

The Wikipedia reference desk is unable to offer legal advice; in any event, the question of 'legality' is going to depend on the jurisdiction (rules will almost certainly vary from country to country) and the purpose for which the title is used. Legal questions aside, if you're applying for a job (particularly for an academic job) it's definitely not a good idea to appear to claim a degree which you don't hold (even if the degree is functionally a close equivalent).

The German Dr. degree often has requirements similar to those required to attain a Ph.D. in English-speaking countries, but it doesn't mean that you can make the substitution willy-nilly. (Consider—two universities might offer similar programs in mathematics; one school offers a B.Math. degree, while the other calls it a B.Sc.. Even though the course of study is equivalent, the graduate with a B.Sc. would be torn to shreds if he claimed to have a B.Math., or vice versa.)

In situations where a translation is likely to be helpful, some guidelines might be:

Include the original degree name, so there's no ambiguity about what was awarded;
Translate terms to preserve their sense and literal meaning as much as possible—for example, a Dr. sc. nat. should be translated as Doctor of natural sciences and not as Ph.D. in natural sciences; and
If possible, use the same terminology the university uses in its own English-language documents, press releases, promotional materials, or websites, or find widely-accepted translations for the degree name (Wikipedia can be helpful).

Hope that helps. TenOfAllTrades(talk) 16:08, 27 January 2012 (UTC)[reply]

And how do people in the US refer to PhDs: as Dr. so-and-so or Mr. so-and-so? — Preceding unsigned comment added by 88.26.74.157 (talk) 15:41, 28 January 2012 (UTC)[reply]

Dr. so-and-so, at least professionally. See Doctor (title)#United States. --Tango (talk) 17:47, 28 January 2012 (UTC)[reply]

By the way, in the U.S. at least, don't double-up and refer to yourself as "Dr. Jack Harkness, Ph.D." unless you want to look like a quackpot. SamuelRiv (talk)

What health hazard does sand or glass particle which are used in sand blasting causes?

In sand blasting machine sand particls or glass particls are used which is normally inheled by the surrounding peoples. Which kind of dieses or health hazard does it cause? — Preceding unsigned comment added by 220.225.96.217 (talk) 16:29, 27 January 2012 (UTC)[reply]

See silicosis. Wnt (talk) 17:06, 27 January 2012 (UTC)[reply]

Also, sand-blasting is incredibly loud, so hearing damage is likely, if proper protection is not used. StuRat (talk) 18:28, 27 January 2012 (UTC)[reply]

permanent cure of stye.

We delete these questions for a good reason. Please start a discussion at WT:RD seeking to change the rule rather that trying to circumvent them every time

The following discussion has been closed. Please do not modify it.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the talk page discussion (if a link has been provided). --Jayron32 18:01, 27 January 2012 (UTC)[reply]

As I said - recognizing that we can neither diagnose nor treat the condition - I think it does no harm to point the OP to our article on styes, nor to point out that old or contaminated cosmetics can carry the bacteria. That is neither diagnosis nor treatment, which the OP's doctor already did three times, but just common sense. The Refdesk prohibition has been explained as a matter of "ethics", and what sort of ethics could require us not to repeat such a basic and widely publicized piece of advice? Wnt (talk) 20:23, 27 January 2012 (UTC)[reply]

The guy's doctor can't fix it and he's coming to us for advice? That's funny. Sort of. There's nothing we can do for him except tell him to find another doctor. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:40, 27 January 2012 (UTC)[reply]

Doctors are always in a rush, and don't take the time to give you instructions you should have read on the Internet. Or to follow instructions they should have read on the Internet. Not two months ago I had a doctor trying her level best to intimidate me into taking ciprofloxacin, threatening to "discharge" me as a patient otherwise, for a simple ingrown toenail, telling me that podiatrists have limited knowledge, when I'd just had an unbearably sore Achilles tendon from gout five days before, and two other risk factors for getting sudden tendon snaps from that crazy substance. Even when I pointed out the problem she made out as if that crippling side effect was nothing to worry about. Well, to the podiatrist it was a run-of-the-mill case, and the X-ray showed none of the bone infection she claimed I "probably" had despite my strong impression otherwise. I say, if your ethics allow you, you can try trusting a bookie or a drug dealer and you might get away with it, but never trust a doctor. Wnt (talk) 00:21, 28 January 2012 (UTC)[reply]

"Trust but verify." Did you take your problem to a bookie or a drug dealer? No, you took it to another doctor. QED. :) ←Baseball Bugs ^{What's up, Doc?} carrots→ —Preceding undated comment added 00:27, 28 January 2012 (UTC).[reply]

Energy density of algae produced biodiesel and biogasoline

Is the energy density of the aforementioned fuels the same as their petroleum counterparts? ScienceApe (talk) 20:12, 27 January 2012 (UTC)[reply]

I do not have sources but I guess the answer is no, because that would be highly unlikely. It is hard to find two different materials with the exact same energy density. Von Restorff (talk) 01:39, 28 January 2012 (UTC)[reply]

Are they different? Petroleum is just biomass (mostly algae) that has been subject to intense heat and pressure over a long time. ScienceApe (talk) 01:59, 28 January 2012 (UTC)[reply]

Common biofuels are often a little lower in energy density than the conventional fuels they are intended to replace (e.g. 5-10% lower), but it can vary based on the feedstocks and processes used. I don't have any specific details for algae-based fuels, but as a first guess it wouldn't be surprising if they are a little lower on average. Of course petroleum also varies considerably in energy density, but we defined standards for fuels and require refiners to adjust the final product to match. I would assume that before biofuel really takes off there would be similar standards adopted for its expected energy content. Dragons flight (talk) 06:17, 28 January 2012 (UTC)[reply]

Farsi Island

Is there any source mentioning the area of Farsi Island? Or maybe a naval map with large scale? Thanks --тнояsтеn ⇔ 22:28, 27 January 2012 (UTC)[reply]

It's pretty small. My CM93 charts represent is as a 9-vertex polygon about 0.46 nm long (WNW to ESE) and 0.22 nm at its widest (SSW to NNW), with an average width of about 0.15 nm, suggesting an area of about 0.237 km ². It also shows a smaller island 85 m off the south coast of main island (in an area of coral) which is represented as a 5-vertex polygon, roughly a 123 m x 103 m rectangle with its NW corner lopped off, yielding an area of about 0.011 km². The combined land area is about one quarter of a square kilometer. My chart doesn't actually call them as "Farsi Island", instead labeling them as "Al Farisiyah" and reports a radar transponder beacon, tower, and light (28.0 m, flashing twice every 15 seconds, visible for 16 nm) at 027.9925N 050.1729E. On this chart, the coordinates given in the article (27.98N 50.18E) are of a point 0.85 nm SSE of the light in open water about 40 m deep. I don't know the original source of the data here, and can't give you an RS. Sorry. -- ToE 22:36, 28 January 2012 (UTC)[reply]

Spanish Wikipedia mentiones a much larger dimension of the island (es:Isla Farsi) and so do other Wikipedias. Aerial images show a quite small island, that is why I asked. So your numbers make much more sense. Thank you! --тнояsтеn ⇔ 22:51, 28 January 2012 (UTC)[reply]

What aerial imagery have you seen? With Google Maps satellite view, I can't make out any land either there or at the spot 12.5 nm south where the Saudi island Al Arabiyah is supposed to be. The nearest land I can make out is Jazirat Karan 25 nm to the SW. -- ToE 02:51, 29 January 2012 (UTC)[reply]

Bing Maps ([2]). --тнояsтеn ⇔ 13:21, 29 January 2012 (UTC)[reply]

Size of the Universe at the Big Bang.

Can anyone tell me what the size, that is volume, of the universe was at the moment of the Big Bang, or at least as close to it as we can get. When I say universe, I mean the entire universe, not only the parts we can see. I've been getting contradictory answers to this question, (either it was a point or already infinite), and I look to you for some clarification. 23:42, 27 January 2012 (UTC) — Preceding unsigned comment added by 68.6.88.47 (talk)

I suppose it depends on how you define the universe. If all the matter is in one geometric point, and then you have infinite space around it, does that make the universe the point or infinite ? Note that there could also be other big bangs, in which case some coin the term "multiverse" to encompass all of them, and perhaps the vast empty spaces between them, too. StuRat (talk) 23:50, 27 January 2012 (UTC)[reply]

A single point of matter within an infinite space is an incorrect picture of the Big Bang. Near the Big Bang, the whole universe was in a hot, dense state. There was no space around it. Spacetime itself rapidly expanded from the singularity.

It isn't known for sure whether the universe was nearly a single point or infinite near the Big Bang, because it isn't known for sure whether the universe is finite or infinite, although according to Shape of the universe#Open or closed, the universe is considered to be without boundaries in the standard FLRW model of cosmology. Red Act (talk) 00:33, 28 January 2012 (UTC)[reply]

If the ruler with which one measures the universe is within the universe, I'm guessing the size would be infinite. As for being outside and measuring it.... (my mind is threatening to explode) HiLo48 (talk) 00:34, 28 January 2012 (UTC)[reply]

Why would you say that? A flatlander living on an S² manifold (say, the surface of a sphere) could do experiments to measure the size of its universe, even though its ruler is contained within its universe. -- ToE 18:53, 28 January 2012 (UTC)[reply]

Lets assume the matter was in a gravitational singularity before the Big Bang, and there was no space around it. Von Restorff (talk) 00:38, 28 January 2012 (UTC)[reply]

We're assuming Big Bang cosmology, which doesn't say that matter was a gravitational singularity before the Big Bang. I don't think that really makes sense. -- BenRG (talk) 05:49, 28 January 2012 (UTC)[reply]

Traditional big bang cosmology predicts a gravitational singularity before this time, but this theory is based on general relativity and is expected to break down due to quantum effects. Von Restorff (talk) 11:35, 28 January 2012 (UTC)[reply]

That's correct; what it says is that traditional big bang cosmology, which suggests there is a gravitational singularity, is expected to break down (i.e. to be wrong) in the era where it predicts the singularity. That's as contrasted with modern-day big bang cosmology, which doesn't have the singularity. -- BenRG (talk) 02:00, 29 January 2012 (UTC)[reply]

There wasn't actually a "moment of the Big Bang". All we know is that the universe has been expanding and cooling from a very hot, dense, and amazingly homogeneous state for about 13-14 billion years. We don't know how large the homogeneous region was or where it came from. If you believe inflationary cosmology then it was very large, much larger than the part we can see now, but beyond that it's hard to say anything. -- BenRG (talk) 05:49, 28 January 2012 (UTC)[reply]

It is not known if something existed before the singularity that appeared at the moment of the Big Bang, nor if time is linear, since the expansion estimated by Hubble's law assumed a linear expansion, and later work indicates there may have been variations. Von Restorff (talk) 14:18, 28 January 2012 (UTC)[reply]

That's gibberish added by a well-meaning layperson almost a year ago. I'll delete it. -- BenRG (talk) 02:00, 29 January 2012 (UTC)[reply]

I think that the meaning of a measure of time defined in terms of oscillations of a cesium atom, at a time when a cesium atom was larger than the universe, is rather mysterious. A tremendous amount of stuff happened in those first few "instants" of the universe, which had impact on future eras. To imply that that was all "nearly instantaneous" rather abuses the concept. Really the Big Bang reflects the inability of our standard of time, the laws of physics of our conventional forms of room temperature matter, to be relevant to higher energy regimes. I get the impression that, in the same way, when protons and electrons decay, when the universe is a vast cold dark wasteland perhaps populated by "neutrino nuggets" (see Wikipedia:Reference_desk/Archives/Science/2011_September_15#Neutrino_chemistry), a vastly longer scale of time and space might make its doings again seem exciting to its residents. Wnt (talk) 16:19, 29 January 2012 (UTC)[reply]