Wikipedia:Reference desk/Archives/Science/2017 September 30

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September 30

Oxirane excited state

How much higher in energy is the excited state of oxirane, wherein the molecule can be considered an ethylene complex of an oxygen atom, than the ground state? Plasmic Physics (talk) 00:03, 30 September 2017 (UTC)

@Plasmic Physics: I don't really understand the distinction you're making there, but here is the IR spectrum and here is the UV-vis spectrum. 1/ 3800 cm-1 = 2630 nm , so there is quite a gap between this and the 182 nm the UV-vis spectrum given begins at, but if the absorptions in the UV-vis spectrum peaking at 156, 159, 171, 173 are what you want, then you'd think the energy might be around hc/lambda, i.e. (from photon energy) 1.2398 eV um / (.156, .159, .171, .173) um = (7.94, 7.80, 7.25, 7.17) eV. Not at all sure this first-principles approach is correct though. Wnt (talk) 20:19, 30 September 2017 (UTC)

I don't see the reasoning behind your ab initio approach, but I do see an interesting peak in the IR spectrum between 1750 and 1500 cm⁻¹, that would correspond nicely to the double bond in an ethylene ligand. This would seem to suggest that the excited state forms a significant proportion of a sample in thermodynamic equilibrium, which would mean in turn that the energy level is not that much higher than the ground state. The distinction that I'm trying to make is that the excited state involves more pi-bonding character than does the ground state, by either occupying the π-LUMO, or vacating the π^*-HOMO. Plasmic Physics (talk) 22:47, 30 September 2017 (UTC)

@Plasmic Physics: I'm still not really sure what state you're looking for, but my impression is that infrared absorptions are basically vibrations of the bond - though I should admit I don't know what those are in orbital terms. A double bond in that region is absolutely normal for IR spectra. But my impression is that genuinely breaking bonds, or switching from HOMO to LUMO, requires serious visible or UV radiation. See e.g. [1]. I mean, I believe you use UV light to make an otherwise antarafacial sort of Diels-Alder reaction (cycloaddition, really) work by putting one of the aromatic compounds into the excited state. Wnt (talk) 19:32, 1 October 2017 (UTC)

I'm not sure how to describe the state without using the molecular orbital concept. Although, the coordination should look similar to Zeise's salt. Yes, IR-spec asseses bond vibrations, but an individual spectrum makes no distinction between unique species or states of an individual species present. This why a reference spectrum is taken and subtracted from the sample spectrum. I've done plenty of IR spectroscopy, and I can't say that a double bond vibration is normal, if the carrier is aliphatic. This is not really cycloaddition since the molecule doesn't actually break appart to reform, it's just an internal electronic rearrangement, like what happens in the methanium cation. Plasmic Physics (talk) 05:51, 2 October 2017 (UTC)

Hmmm, ethane has a 1.54 angstrom bond length while ethylene oxide is at 1.46. According to Dewar–Chatt–Duncanson model the bond lengths of bound ethylene goes from 1.33 angstrom to 1.34 angstrom in Zeise's salt to 1.43 angstroms in a random ? nickel compound they mention. But I certainly don't understand all considerations, starting with whether the strained bonds of ethylene really curve, and whether that curve makes the bond shorter as the crow flies without actually changing its order. I also don't know if the IR band can be explained simply that the "stiffness" of the three-membered ring, with each member having two bonds close to each other, merely equals that of a double bond. So I don't know if calling ethylene oxide a complex of ethylene is merely a matter of groping the elephant and writing the same interaction different ways. But my expectation would be that if you can make an excited complex that is described by having different bonds between the atoms, that this is a bond-breaking operation at some level and should take UV-vis levels of energy to do. Wnt (talk) 10:14, 2 October 2017 (UTC)

I see, that makes much more sense. Plasmic Physics (talk) 10:35, 2 October 2017 (UTC)

Highest survivable temperature

What is the highest temperature a human has ever survived? 2601:646:8E01:7E0B:D403:68F1:A297:C74A (talk) 01:47, 30 September 2017 (UTC)

[2]. --Jayron32 02:19, 30 September 2017 (UTC)

That's only body temperature, but what about environmental temperature? I'd say that it would be pretty close to the point at which you start to choke from the fluid in your lungs. However, what if you had respiratory gear that controlled the temperature of the air that you inhale? Plasmic Physics (talk) 03:00, 30 September 2017 (UTC)

You'll need to be able to define the Q more precisely to get a precise answer. Some factors:

1) Humidity. The lower the humidity the hotter temps we can survive, due to evaporative cooling from sweat.

2) Wind. Wind can actually make things worse at high temps, as it blows away the air near the body which has been cooled (by the conduction with the body and evaporative cooling) and replaces it with hot air.

3) Time. Obviously high temps are more survivable for short time periods.

4) Body mass. A larger body will take longer to heat up than a small one, due to the square-cube law.

5) Sunlight versus shade. In sunlight, clothing matters a lot, and loose-fitting white clothes may be best.

6) Activity level.

7) Availability of water, especially cool water, to drink. StuRat (talk) 02:58, 30 September 2017 (UTC)

OK, here are more details:

1) Humidity: Low due to extreme air temperature.

2) Wind: Convection only from rising air and combustion products, and from fresh air being sucked in.

3) Time: More than a few seconds is the only limitation (I'd say 1 minute or more).

4) Body mass: How much does a typical firefighter weigh?

5) Sunlight: None, but radiant heat from the fire may be a factor.

6) Activity level: Standing and spraying with a fire extinguisher, moving as needed.

7) Water: Available, but the water may have been heated a great deal by the fire.

8) Miscellaneous: The person is wearing full turnout gear (not a fire proximity suit), but has lost his breathing gear.

2601:646:8E01:7E0B:D403:68F1:A297:C74A (talk) 05:05, 30 September 2017 (UTC)

Guinness Book of World Records (voluntary, briefly): 400°F naked, 500°F heavily clothed. Sagittarian Milky Way (talk) 05:20, 30 September 2017 (UTC)

That low? Don't people sometimes go inside lit brick kilns, coke ovens, locomotive fireboxes, etc. (wearing fire proximity suits, which is not the case in my scenario, that is true) to make repairs without having to wait for the fire to die down? 2601:646:8E01:7E0B:D403:68F1:A297:C74A (talk) 12:38, 30 September 2017 (UTC)

Well I don't know how long that test was exactly. Or if the clothing was even reflective. It may have been broken by now. Also I don't know if firefighters wear thermometers which would be the only way to tell if the air temperature+radiative heat contribution of the fire, walls etc. averaged over their whole body exceeded that. That record might not be in the book anymore because Guinness has sucked for a long time. Many interesting records that rarely change like sweetest chemical or biggest locomotive are replaced by useless things that happened that year like most hours singing Lady Gaga on a roller coaster and biggest underwater rap battle. Sagittarian Milky Way (talk) 15:32, 30 September 2017 (UTC)

Americium oxyrhenide is the sweetest chemical. μηδείς (talk) 23:00, 30 September 2017 (UTC)

In relation to body mass: it's not as simple, because thinner bodies will also tend to more efficiently dissipate heat. If it is still possible of course (if the environment does not transfer more heat to the body than the body can transfer it to the environment including by sweat). Large bodies tend to cope better with cold. Also of interest which was not mentioned would be heat shock. —PaleoNeonate – 06:15, 30 September 2017 (UTC)

For how long can someone stand directly in front of a steel furnace with the hatch open and no protective gear? Plasmic Physics (talk) 08:04, 30 September 2017 (UTC)

In this scenario, the person DOES wear protective gear -- specifically, a firefighter's turnout gear minus the breathing mask (which he lost somehow, maybe by falling through a hole in the floor). 2601:646:8E01:7E0B:D403:68F1:A297:C74A (talk) 12:38, 30 September 2017 (UTC)

I'm thinking you'd have to specify an air pressure - humans can theoretically survive explosive decompression for brief intervals (I'm not sure if the remarkable story of JAT Flight 367 applies, though it certainly might expand my notion of the possible). And temperatures in the thermosphere and outer space can be ... outlandish. I mean, in theory a person in a space activity suit might survive with their skin exposed to temperatures of thousands of degrees for prolonged periods ... I think. Wnt (talk) 20:26, 30 September 2017 (UTC)

Thermosphere? Are you kidding? In this case, the air pressure is normal (29-30 inches of mercury) -- I think I kind of implied this by saying that the person doesn't have breathing gear (so if the air was that rarified, he'd die from suffocation before the temperature could do anything!) And BTW, explosive decompression has nothing to do with this -- it does NOT make the air temperature go up, in fact the temperature goes DOWN because of the Joule-Thomson effect. 2601:646:8E01:7E0B:D403:68F1:A297:C74A (talk) 02:18, 1 October 2017 (UTC)

Hmmm, doesn't sound like I'm talking about what you're talking about here. Wnt (talk) 19:36, 1 October 2017 (UTC)

Right, I'm talking about high temperatures at normal atmospheric pressure (as I said, I kind of implied this by saying the person doesn't have breathing gear, and also by saying that things are on fire -- which they wouldn't be in a near-vacuum such as that in the thermosphere!) 2601:646:8E01:7E0B:D403:68F1:A297:C74A (talk) 01:10, 2 October 2017 (UTC)

How would one detect a magnetic monopole at a distance?

This Forbes blog post https://www.forbes.com/sites/startswithabang/2017/09/28/is-the-inflationary-universe-a-scientific-theory-not-anymore/#7f436605b45e talks about detecting magnetic monopoles, presumably at great distances. (It dismisses the notion they even exist.) If they did, how would they be detected? Thanks. μηδείς (talk) 03:31, 30 September 2017 (UTC)

This isn't an area I know much about, but I don't see that it says it's expected we can detect them at great distances. Instead it seems to be saying that under some theories without inflation, there should be a lot of monopoles, enough that we should have observed them by now but inflation provides an explanation for why we haven't. It greatly reduces the expected density such that it's entirely plausible we still haven't found one. The author appears to be suggesting that inflation isn't the only explaination, it's possible the theory they should exist is just wrong. Our articles Inflation (cosmology)#Magnetic-monopole problem and Big Bang#Magnetic monopoles and Magnetic monopole#Grand unified theories seem to say the same thing (including that others have said something similar to the blog author about our theories of them existing just being wrong). BTW the very next section of the last article Magnetic monopole#Searches for magnetic monopoles discusses various ways to look for them and also seems to support the previous points. Nil Einne (talk) 12:57, 30 September 2017 (UTC)

Yes, I did get the point that inflation might have spread them out so much as to be rare, but the original article seems to imply that even if there were only one in the observable universe it would be detectable (without outright saying this, or explaining how). I also read our entire article, including the section "searches for magnetic monopoles" before posting this, but it spoke of inducing currents in wires, not some sort of observable far-off phenomenon like a black whole. That's what I am wondering, would they be detectable somehow on cosmic scales? Or only like particles in a neutrino detector? The Forbes blog implies without actually saying it that they would be detectable even if there were only a very small number of them. μηδείς (talk) 13:30, 30 September 2017 (UTC)

Again, I don't see that the Forbes articles implies that "even if there were only one in the observable universe it would be detectable" or even "they would be detectable even if there were only a very small number of them". Yes there is one brief mention of single monopole in an image caption, but no where does it seem to imply we would have found that single one. It also says We do not, however, see any of them which seems to be simply saying we haven't definitely found any, even though we should have if they were as abundant as some theories predict. (Our articles do suggest the maximum possible density of monopoles based on current research, so I guess it does depend on what you mean by very small number. I'm assuming the Forbes article was written accepting this research although it only really barely touches on it IMO.) Could you explain what parts lead you to believe that it's trying to suggest we would have found them even if there was only a single or or "very small number"?

To me it seems to be saying the same as our articles are saying. 'We aren't seeing any magnetic monopoles. Inflation supporters say this is because under inflation they're so rare this is to be expected. An alternative hypothesis is that our theories on how common they would be without inflation are simply wrong. In fact, perhaps it's completely expected they don't exist even without inflation.'

Actually it seems to me it's specifically implying that we can't detect only one, or probably a few. If it were claiming we could detect only one, then it would be saying or at least implying that 'clearly we are wrong, since we know there isn't even one based on research', But instead it just offers an alternative hypothesis and don't say or imply 'this is definitely correct, since we are are extremely confident there are no monopoles'.

The only thing it really says about monopoles other than we haven't found them and possible reasons why (either because inflation is correct or because our theories on how many monopoles there would be are wrong), is that we haven't found evidence for grand symmetry but the actual search for this was primarily looking for proton decay rather than anything to do with monopoles. Actually if I understand the last sentence to do with monopoles correctly, it's even acknowleding that mostly even supporters of inflation don't consider the monopole problem as compelling evidence for inflation which again seems to be semi supported by our articles.

BTW, I just realised the third link above if incorrect, I meant Magnetic monopole#Grand unified theories 2. Also I admit I only really read the beginning and the part to do with monopoles then searched the rest to look for any other mention. So if the article talked about monopoles in other sections without meaning the word, I would have missed that.

Nil Einne (talk) 16:29, 30 September 2017 (UTC)

The article did say that if symmetry breaking were true, there would be one monopole in the observable universe. On what basis is this claim made or to be verified? Should I just give up? Inflation has always seemed like an unfalsifiable premise to me. But I only took up to Physics 202. μηδείς (talk) 19:09, 30 September 2017 (UTC)

You'd detect a magnetic monopole in the same way you'd detect any other monopole! Measure the magnetic field and estimate a best-fit for a spherical harmonic decomposition and look for a non-zero coefficient for the first term... which we never see!

A monopole would satisfy certain mathematical properties. We have fancy equations to express those properties using very few words - for example, non-zero divergence. So, you'd measure the field, and you'd observe its mathematical properties, and you'd look for any deviation from normally-observed properties. So far, this specific type of deviation has never been seen, and there isn't any good reason to expect it. You would literally have better luck looking for electrons that deviate from normal electrons by carrying a positive electrical charge, because there are a few places in the universe where that rarity actually exists.

Nimur (talk) 17:02, 30 September 2017 (UTC)

Nimur! Why are you yelling at me! If I understood this already, I wouldn't have asked! And if I hadn't read up on the subject here, I wouldn't have asked! (An unmarried Pollack!) μηδείς (talk) 19:09, 30 September 2017 (UTC)

I use exclamation points for emphasis, not because I mean to yell at anybody. I apologize.

If I may misquote Herman Kahn, [3], I apologize for my prolific use of typographical emphasis (!!). I do it in spite of many admonitions from friends and colleagues and in full awareness that many people will find it irritating. I feel, however, that some readers will find it helpful. Nimur (talk) 19:37, 30 September 2017 (UTC)

NP! :) μηδείς (talk) 20:46, 30 September 2017 (UTC)

https://arxiv.org/abs/astro-ph/9412053 Count Iblis (talk) 23:20, 30 September 2017 (UTC)

[ec] (Haven't read Iblis' yet) Am I to understand monopoles would be subatomic? Wouldn't the r² law simply make them indetectable unless they were in your lap? μηδείς (talk) 00:37, 1 October 2017 (UTC)

Monopolonia? Jak gdyby byli więcej niż jedną Polskę!

The above translates as "Monopolonia? As if there were more than one Poland!" Blooteuth (talk) 02:29, 1 October 2017 (UTC)

When I worked in the post department of a famous bookshop we had to type the first word of the name of the firm raising the order on the invoice in capitals. On one occasion I also added it as the first word of the address. The order, for a customer in New York, was raised by "Polak's Frutal Works" [4]. One afternoon the manageress told me a customer had come in, asked for who had typed his invoice, and said he had said he had come over from New York to fight with me but I had just gone to lunch. Then I was called to the general manager's office. He asked me "Have you ever come across the word 'Polak'?" I thought for a minute and said "no". He said "It's a derogatory word for a Polish person, like 'Limey' for an Englishman. You wrote it all over a customer's address label. When the postman delivered the book he said 'Look what they call you in London!'" When I saw the label I explained who had raised the order and he said "You did the right thing". 81.147.142.152 (talk) 08:55, 1 October 2017 (UTC)

The changing magnetic field created by a single monopole has the effect of introducing a relatively long-lived electric current in any conducting loop that it passes through. A simple circle of wire is sufficient for this effect. A magnetic dipole passing through the loop does not have the same effect. In order to detect such a current you need a sensitive current detector and ways to eliminate interference, but both technologies are well developed for scientific research. So, basically, you lay out a large loop of wire, hook up some fancy measurement equipment, and wait for a monopole to fly through your loop. Monopole studies often imagine that the monopoles will be coming at high speeds from space. The larger the loop, the smaller the expected current, so there are some trade-offs when deciding the size of your measurement device. However, after observing for a while, the failure to see any monopoles can be interpreted as a limit of the flux of monopoles in the neighborhood of your detector. For a given assumption about the average monopole speed, a flux limit can then be translated into a density limit for our region of space. Without too much effort one might conclude that there are fewer than 100 relativistic monopoles in a volume the size of the Earth. However, for more powerful limits one is likely to turn to other types of studies. Dragons flight (talk) 02:18, 2 October 2017 (UTC)

Question about the SUNRISE and SUNSET on equator of Earth?

Planet earth not only rotates about its axis but also orbits around the sun once every 365.25 days. Ignore the obliquity of the earth's axis which is more related to the seasons. Days and nights on the equator of the earth are nearly the same; 12 hours each say e.g., Seri Lanka.

For simplicity, lets days and nights are 12 hours each on the equator of the earth throughout the year.

Bird’s Eye View Observer of Picture sees

• SUNRISE in the autumn equinox and SUNSET in spring equinox on his RHS

• SUNSET in the autumn equinox and SUNRISE in spring equinox on his LHS

Thus Bird’s eye view shows a difference of 12 hours when SUNRISE in the autumn equinox takes the position of SUNSET in spring equinox on earth - vice versa and the same is applied to summer and winter solstice. Sunrise and sunset take their original positions when the earth completes its orbit around the sun.

This means, each day, sunrise is lagged behind approximately by 1 min and 24 hours in one year (12 hours in six months as explained above)

If the presented model in the Picture is truly accepted worldwide then why don't we notice such effects in our daily life unless I missed something important?2001:56A:7399:1200:8CC4:755D:4DBC:A90A (talk) 04:17, 30 September 2017 (UTC)EEK

I think you are referring to sidereal day vs. solar day. A real day is 23 hours, 56 minutes and 4.something seconds. The reason this is not noticed is because right is winter constellations and left is summer constellations and this is how you'd tell. (technically a sidereal day is not exactly one rotation, a stellar day is but it takes 26,000 years for the two to be off by 1 day). Sagittarian Milky Way (talk) 04:31, 30 September 2017 (UTC)

No, I am not referring to sidereal day vs solar day as days and nights in my questions are still remain the same but lagging behind every moment when the earth changes its position in its orbit around the sun.

Yes, you are referring to sidereal day vs. solar day. The reason we don't notice is that all timekeeping in everyday life is based on the solar day. Sidereal days are only important if you're interested in observing the stars, planets, etc. --69.159.60.147 (talk) 06:10, 30 September 2017 (UTC)

When you say "sunrise is lagged behind approximately by 1 min" I think you mean 1 degree. The sun's position along the ecliptic (orbit) can be expressed in degrees or time measured eastward from the vernal equinox (Right Ascension). This is tabulated in almanacs - you can see the daily change here [5]. 82.14.24.95 (talk) 11:55, 30 September 2017 (UTC)

The question was: "why don't we notice such effects in our daily life...?"

Aren't you paying attention to the sky, the stars, and the planets? If you watch them each day, you will notice that they rise and set at different times because the Earth is moving relative to the sun; some of them wander around in the sky and some even look like they're moving backwards; these are not purely-theoretical ideas and you don't need special technology to notice these occurrences. All you need is a keen attention to detail.

Probably the easiest object to notice, if you live on Earth, is the Sun; and next, the moon; watch how the moon rises at a different time each day. Once you've intuitively developed a sense for its pattern - which will take about a month to see through the cycle - next, start watching for the planet Venus - it appears to move much more slowly, and you'll need nearly one whole Earth year to notice its variations. Finally, after you've developed such patience, you can really begin to notice that the stars rise and set at a different time each evening - but the change is very slow.

Some older astronomy books - the ones that assume all the readers live in Northern Europe - write about "summer" and "winter" constellations. The "winter constellations" are stars that rise just after sunset, but only in the winter time. In summer, those same stars are still in the same general spot - but they're overhead only after sunrise! If you recognize those constellations, you absolutely notice that the Earth moves around the sun.

As of the time I write this, Orion is becoming easier to see - as long as you live like a diurnal mammal on the northern half of planet Earth. The stars themselves have not moved very much - but because the constellation appears high in the sky only a few hours after sunset, now - say tonight at around 8:30 PM - is a good time to spot it. If you watch this group of stars for the next six or twelve months, you'll see that every day, they rise a little bit later... And if you live elsewhere in our universe, you'll see your own set of constellations that are easier to see during certain seasons.

Saturn is up, too... right now in California, we can watch Saturn all day long (except we have to work around that pesky blue sky problem). Saturn sets just after sundown, so if you wanted to watch it for long, you'd have to put another observer in Australia, on the other side of the Pacific (where the sun and Saturn go, right after they set in California).

Of course, the sun hasn't gone anywhere - we say that the sun has set, but in reality, it's the Earth that has spun! If anything, it is me and you and the entire Pacific Ocean - we're the ones who have rolled away from the stars and planets that used to be over our head, and no power in the universe can stop us!

So, why doesn't our OP notice the effects they describe? Effects of living on a round planet that moves in space, surrounded by other round planets that also move in space? Evidently, the OPs aren't looking hard enough... the effects are everywhere!

Nimur (talk) 16:05, 30 September 2017 (UTC)

The most obvious example of this is the planet Venus. It's many a time been mistaken for a flying saucer or an aircraft. You see it in the evening as the "evening star" and then it disappears and comes back as the "morning star". Eventually the ancients worked out that both apparitions are of the same object. 82.14.24.95 (talk) 18:51, 30 September 2017 (UTC)

This took longer for Mercury I think. Evening or morning Mercury was called Hermes in Greek and the other one was called another god. Sagittarian Milky Way (talk) 19:47, 30 September 2017 (UTC)

• Day is longer than night everywhere because the sky is bigger than the ground to an observer. This is due to the curvature of the Earth. If you were standing on a tiny planet the size of a basketball, you would have nearly all day and hardly any night. Abductive (reasoning) 20:18, 30 September 2017 (UTC)

This is called horizon dip. Actually for many people the sum of these factors makes more difference: atmospheric refraction: adds about 4 minutes, Sun is 31.5 to 32.5 minutes wide: adds about 2 minutes, Sun usually doesn't drop straight down: exaggerates the above factors. At middle latitudes these sum to over a tenth of an hour. (half at sunrise and half at sunset) Sagittarian Milky Way (talk) 21:41, 30 September 2017 (UTC)

First of all thank all for your interest and replies. I thought my question was easy to understand for illuminate but let's try this way.

AE = Autumn equinox

WS = Winter solstice

SE = Spring equinox

SS = Summer solstice

Take a point “A” on the equator of earth at sunrise at AE. Now follow this point “A” during the rotation of the earth about its own axis while orbiting the sun. Let's assume first earth is stationary and rotating about its axis only not revolving around the sun. To the Bird's eyes view observer point, “A” always takes its position again when an earth completes its rotation about its axis. Now

There are two different types of the motion of earth according to the accepted model.

1- Rotation of the earth about its own axis

2- Revolving of the earth around sun in its orbit

Both “1” and “2” are independent of each other. Try with an educational globe. Thus the image of the earth is the same in all AE, WS, SE and SS position. So point “A” can be seen in

AE @ Sunrise

WS @ Midnight

SE @ Sunset

SS @ Noon

Example: If sun rises at “A” at 0600 on Sep 01 in AE position then on the equator

Sun rises at 05:59 on Sep 02

Sun rises at 05:58 on Sep 03

Sun rises at 05:57 on Sep 04

Sun rises at 05:56 on Sep 05

Sun rises at 05:55 on Sep 06

Sun rises at 12:00 in its WS position

Sun rises at 18:00 @ in its SE position

Sun rises at 24:00 @ in its SS position

Sun rises again at 06:00 @ AE (When the earth completes its orbit around the sun)

Thus days and nights in my questions still remain the same but lagging behind every moment when the earth changes its position in its orbit around the sun. I hope I have explained things clearly enough to understand. Please correct me if I am wrong.2001:56A:7399:1200:ED04:E934:3CEF:873A (talk) 02:13, 2 October 2017 (UTC)

There's not enough room for something to change 1 minute per day and add up to 24 hours in 1 year. There are 1,440 minutes in a day, it'd take about 4 minutes per day. Also your explanation is going in opposite directions. Time is determined by the Sun. The left and right don't matter for time (except sidereal time which determines what constellations are up). The longitude of the Equator that's at sunrise on the fall equinox will not be at sunrise on the next fall equinox. It'll be about noon because the year is a whole number of days plus 5 hours 48 minutes and 46 seconds long (give or take a few minutes because 12 lunar months is only 354 days, the planets jiggle the Earth-Moon system's orbit around the Sun a little and so on) Sagittarian Milky Way (talk) 02:45, 2 October 2017 (UTC)

So all you are asking is "What is the sidereal time at sunrise?" Noon sidereal time is when the vernal equinox is on the meridian. Be clear in your mind as to the difference between the vernal equinox as a direction in space and as a date on the calendar. The "right ascension" (of the sun) mentioned above is the sidereal time at midnight solar time. Now, on the equator on 23 September (the autumnal equinox) the sun will rise at 06:00 by both sidereal and solar time because the vernal equinox culminates at midnight (it being halfway round the orbit from the autumnal equinox). Every day the stars rise about four minutes earlier by solar time (which means the sun rises about four minutes later by sidereal time). Consequently, by the winter solstice the sidereal time of sunrise has advanced to noon, by the vernal equinox to 6 P.M., and by the summer solstice to midnight. We don't notice all this because our clocks are set to solar time, however astronomers do notice it because the sidereal time tells them where to point their telescopes, and it's also an ingredient in the formula by which they derive Greenwich Mean Time from celestial observations. 81.147.142.152 (talk) 09:35, 2 October 2017 (UTC)

Something has gone awry here. If a body has right ascension X, the sidereal time when it is on the meridian is X. So at the vernal equinox, (when the sun has right ascension of 0h), the sidereal time at solar noon is 0h. Or to put it another way, the sidereal day begins when the vernal equinox ("place") (which we can call the "first point of Aries" to avoid confusion) is on the meridian. The sun's right ascension increases by about four minutes per day. So the relationship is:

                                                      Sun's Right  Sidereal Time   Sidereal Time                
                                                      Ascension    at Solar Noon   at Sunrise 
Vernal Equinox (21 March)                                 0 h           0 h            18 h
Summer Solstice (21 June)       sun has moved 90° E       6 h           6 h             0 h  
Autumnal Equinox (23 September) sun has moved 180° E     12 h          12 h             6 h
Winter Solstice (21 December)   sun has moved 270° E     18 h          18 h            12 h

Right answer, wrong reason. 92.8.220.234 (talk) 19:29, 2 October 2017 (UTC)

Here is confusion why one can’t notice aforementioned lagging on our mechanical clocks in the representation of Sidereal time Vs Solar time

Sidereal time reckoned from the motion of the earth relative to the distant stars – so its still relative to earth. The position of the sidereal time keeping observer (on earth) also change when earth changes its position in its orbit around the sun

The position of observer "O" in Bird’s eye view of the modeled diagram is fixed in space and therefore the interpretation of "O" is more accurate than observing star moment up in the sky from earth.2001:56A:7399:1200:2016:33DE:67DE:8B48 (talk) 22:27, 2 October 2017 (UTC)Eclectic Eccentric Kamikaze

someone already asked this question. I just found the link2001:56A:7399:1200:90A9:3AE0:8E63:A453 (talk) 03:45, 6 October 2017 (UTC)eek

Why is the sea level of the Pacific ocean different than the sea level of the Atlantic ocean where the panama canal is?

But the same where Cape horn is? ScienceApe (talk) 20:53, 30 September 2017 (UTC)

Because the prevailing winds, and hence current, can blow around Cape Horn but not over the Isthmus of Panama? We learned this back in 10th grade History when it was discussed why President Grant wisely chose in a moment of sobriety not to use H-Bombs to simply blow a lock-less waterway through the territory. μηδείς (talk) 21:12, 30 September 2017 (UTC)

Your ignorance is showing. President Grant, h-bombs, it is to laugh. Abductive (reasoning) 21:13, 30 September 2017 (UTC)

Yes it's laughable. Ulysses S. Grant b. 1822, POTUS 1869 - 1877, d. 1885. An H-bomb was not available until after completion of the Manhattan Project 1942 - 1946. Blooteuth (talk) 02:23, 1 October 2017 (UTC)

Ignorance? At least ScienceApe is trying, rather than drinking whiskey. That counts for something in my book. μηδείς (talk) 22:50, 30 September 2017 (UTC)

If you read our Panama Canal article it says that the difference in levels is due to "differences in ocean conditions such as water densities and weather" which is cited to [6]. Richerman (talk) 23:41, 30 September 2017 (UTC)

Yes, winds and currents being other terms for "differences in ocean conditions such as water densities and weather". I appreciate the confirmation.

Now, about why Grant didn't decide to use H-bombs...or did he? μηδείς (talk) 00:30, 1 October 2017 (UTC)

"Was it 'over' when the Germans bombed Pearl Harbor?" ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:11, 1 October 2017 (UTC)

It was'nt the Germans but their allies, the Japanese who did the Attack on Pearl Harbor. --Kharon (talk) 15:46, 2 October 2017 (UTC)

I'll stand by Bluto Blutarsky's world view.[7] ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:05, 2 October 2017 (UTC)

Some readers here may not understand that this stupid subthread is alluding to a real proposal of the 1960s. See Operation Plowshare#Proposals. --69.159.60.147 (talk) 18:22, 1 October 2017 (UTC)

Who you calling stupid? Jesus,, the Grant/H-Bomb BS was a joke, but I do assume people who've gotten an educationn to age 16 would know t'were a friggin joke. μηδείς (talk) 14:56, 2 October 2017 (UTC)

U.S. Grant was a rough-hewn character. Sometimes he would get angry and holler "Hell!" Otherwise known as dropping an H-bomb. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:05, 2 October 2017 (UTC)

Can I just have a straight answer instead of troll answers? ScienceApe (talk) 03:54, 1 October 2017 (UTC)

I googled "pacific ocean higher than atlantic at panama canal" and there are many results. This one, from The Straight Dope, may be interesting.[8] If not, do that google yourself and see which answers you like. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:02, 1 October 2017 (UTC)

Short answer, the Earth isn't flat and oceans don't behave like a puddle on the sidewalk. Ocean currents, winds, etc. cause the local height of the ocean's surface to vary. For instance, it's higher at the Equator because it bulges out due to Earth's rotation. The land at the Equator does this too. --47.138.161.183 (talk) 07:22, 1 October 2017 (UTC)

The Earth bulges out thing is already taken into account with mean sea level. That's why the equatorial Andes aren't the highest point in the world. Sagittarian Milky Way (talk) 07:49, 1 October 2017 (UTC)

As to the difference in water density mentioned above, see Why is the Atlantic So Salty from Columbia University. Alansplodge (talk) 11:59, 1 October 2017 (UTC)

The most important factor for most parts of the ocean is the long-term average wind flow, which also affects surface currents. Water flows downhill, to good approximation, but if winds consistently blow water towards the land then on average the water piles up a little higher at that coast. Conversely, if winds consistently blow away from the coast, then they carry a little bit of the water away from the coast and sea level there is, on average, slightly lower than one would expect. The deviations often amount to less than a foot across basins that can span hundreds or thousands of miles. Dragons flight (talk) 07:08, 2 October 2017 (UTC)

"Wind flow" is repeated in answers here, but not ocean current. The ocean current is west-to-east on both sides of the canal. You can easily do a mini-experiment in a pool or tub. Put your hand in the water to create a strip of land separating two bodies of water. Since it is hard to make the water flow, move your hand instead. If you move it right to left, you will see water on the left side rise and water on the right side fall. That is exactly what is seen on the two sides of the canal. 209.149.113.5 (talk) 14:24, 2 October 2017 (UTC)

According to this, sea level is about 20 cm higher on the Pacific side of Panama than the Atlantic; if there were a canal without locks, there would be a steady flow from the Pacific to the Atlantic, augmented by tidal currents because the tides have opposite phase on the two sides of Panama. The two oceans can keep water flowing indefinitely in a giant Siphon connecting tube; could this be the basis of future free hydroelectric energy for Middle America? Blooteuth (talk) 21:48, 2 October 2017 (UTC)

My understanding was the Suez Canal is in a similar situation, though its flow varies in direction by season. But these canals... well, they're like really flat rivers. I mean, the first power plant was at Niagara Falls, involving a large amount of water falling a very long distance (around the falls indirectly, that is; they never quite nerved themselves up to literally eradicate them for a power generator, just turned them down a lot). So it is really scraping the bottom of the barrel to get to this; it's way worse than damming the mighty lower Mississippi in oxbow country. On the other hand, if you could make a canal a mile wide and a mile deep maybe you'd have something, since the volume could be huge. Wnt (talk) 22:21, 2 October 2017 (UTC)