Wikipedia:Reference desk/Archives/Science/2019 October 15

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

October 15

Approximately how old is this tree?

The poem The Marshes of Glynn was written under the tree in the second photo in the article - 141 years ago. It is a live oak, which grows slowly. But could this tree have been a significant tree 140+ years ago?

(When I was young, I was told that the original tree died, and that this was a different one. But I don't have any source for that.) Bubba73 ^{You talkin' to me?} 00:31, 15 October 2019 (UTC)

Starke, A. H. (1933). Sidney Lanier: A biographical and critical study. has an earlier photo if that helps, worldcat lists an ebook version [1].—eric 04:26, 15 October 2019 (UTC)

Thanks, it is hard to tell. Here is the 133 photo and this is a recent one. Both seem to have three trunks, but (1) the 1933 pne appears taller, compared to the concrete marker. (2) the concrete marker is farther away and pointing the other direction - the plaque on the marker now faces the tree. Of course, the marker could have been moved. I need to take the 1933 photo to the tree and examine the big branches. Bubba73 ^{You talkin' to me?} 05:39, 15 October 2019 (UTC)

Scratch #1 - a rough measurement of the 1933 photo puts it about 6x the height of the marker; the recent one about 7x. Bubba73 ^{You talkin' to me?} 05:45, 15 October 2019 (UTC)

However, the marker looks like a different one. The plaque on the current marker is old, but the concrete might not be. Bubba73 ^{You talkin' to me?} 05:48, 15 October 2019 (UTC)

I don't think there's any way to get a very accurate answer without obtaining a core sample (or a much older photo). According to our article oaks are very long lived (see also Bowthorpe Oak). But size isn't going to be a very good indicator of age because it's going to be complicated by any number of other factors, such as nutrients, exposure to elements, pests, and so on. Matt Deres (talk) 20:18, 16 October 2019 (UTC)

How to Age a Live Oak Tree (by measuring the circumference).

How to measure a live oak’s girth: "Dr. Stephens estimated that an oak with a girth of 17 feet or more (the Live Oak Society today says 16 ft.) should be at least 100 years of age. But he noted also that many live oaks of much smaller girth can be more than 100 years old as well. The girth can vary significantly depending on whether the tree grows out in the open, far from other trees competing for light and water, or in a natural forest setting where it is more crowded (close-grown). Also, the growth rate and overall health of an oak can vary depending on the quality of the soil in which it grows and its access to a regular water source".

See also Tree girth measurement. Alansplodge (talk) 17:54, 17 October 2019 (UTC)

Famous Trees (1938) Charles Edgar Randall, p. 48 has another photograph. Alansplodge (talk) 18:27, 17 October 2019 (UTC)

Oak trees can be very long lived. The Bowthorpe Oak is thought to be over 1,000 years old. Richerman (talk) 20:29, 17 October 2019 (UTC)

Blood backflow in IV

I came upon a IEEE conference-presentation that sought to design an electronic system to prevent blood backflow in intravenous infusions. I am curious to know of the potentially harmful effects, such a back-flow (restricted to the drip-line or extending to the infusion-bag) might have on a patient, with due references to medical literature. ∯WBG^{style="color:#00F">converse} 04:40, 15 October 2019 (UTC)

So to prevent backflow into the iv line? I guess the first question is why would this need to be prevented? It is not really a big deal... Doc James (talk · contribs · email) 09:25, 15 October 2019 (UTC)

If you put the search term "backflow" into pubmed you get a number of articles that might help. This one caught my eye: Avoiding iatrogenic thrombo-embolism: the "KAPLIT" technique. It says "Also backflow of blood into the IV tubing ... predisposes to clotting of blood in the IV tubing/catheter. Overenthusiastic efforts to push IV fluids without disconnection and flushing of IV line may pose a possible risk of embolizing the clotted blood thrombus into circulation." 70.67.193.176 (talk) 21:02, 17 October 2019 (UTC)

XY chromosome disorders.

So, red-green colorblindness affects only males, 8% of males. That is because the gene for colorblindness sits on the X chromosome, and women are XX. Since men are XY, and Y is a lot shorter than X in humans, allows men to be born colorblind. Is the 8% due to the Y chromosome being about 8% as long as the X? And what are some other examples of disorders besides red-green colorblind? My book only lists 1 other and that is hemophilia. It mentions women can be carriers of hemophilia to pass it down to sons, does that mean women can pass down red-green colorblindness to sons too? Thanks. 67.175.224.138 (talk) 04:51, 15 October 2019 (UTC).

The size of the Y chromosome actually has nothing to do with colorblindness. The reason that red-green colorblindness is more common in men (note, it is not exclusive to men, just very rare in women), is entirely due to the fact that only the X chromosome carries the genes for the red and green color receptors. The 8% rate (which is not for men in general, but for men of northern European descent) is a consequence of the mutations that cause it being found on about 8% of X chromosomes in that group. See X-linked recessive inheritance for more examples of diseases that are inherited in this fashion. And yes, a woman can be a carrier of red-green colorblindness, and pass it onto her sons. Someguy1221 (talk) 08:39, 15 October 2019 (UTC)

Indeed, in very rare cases, women can be red-green colorblind as well, if they received the recessive gene from both parents. A facile calculation of 0.08*0.08 = 0.0064, or about 6 out of every thousand women should be red-green colorblind. The actual quoted statistic in the Wikipedia article Color blindness is 0.5% (5 out of 1000), which is within rounding errors for these calculations. --Jayron32 11:44, 15 October 2019 (UTC)

Correction, those figures are for people of Northern European descent rather than for the world population at large. --Jayron32 12:03, 15 October 2019 (UTC)

Because of X-inactivation, it seems possible for a woman to be colorblind in only one eye. —Tamfang (talk) 19:44, 17 October 2019 (UTC)

Men too can have differing color vision in their eyes. While I am not color-blind, I do have differences in color perception between each of my eyes. Relatively speaking, one of my eyes sees things slightly redder and the other slightly bluer than the other. I have no idea which (if either) is "normal", but as I have had this my whole life, it is my "normal". --Jayron32 16:49, 18 October 2019 (UTC)

You might consider taking the glasses off. Someguy1221 (talk) 17:38, 18 October 2019 (UTC)

Escape at less than escape velocity?

Is it possible for an object travelling at less than the escape velocity from the sun to escape the sun's gravity well by slingshot from another mass? This is without any thrust, I know that a slingshot can be used to greatly increase the effect of thrust by applying it near the point closest to the other object. -- ????

Yes. The third stages of the launch vehicles for Pioneer 10, Voyager 1 and Voyager 2 followed similar initial trajectories to their probes, but without thrusters for course correction or boost during gravity assist manoeuvers. All three third stages are now believed to have achieved solar escape velocity after unguided gravity assist fly-bys of Jupiter and Saturn - see List of artificial objects leaving the Solar System. Gandalf61 (talk) 08:26, 15 October 2019 (UTC)

Thanks, it certainly is possible then! -- Q Chris (talk) 11:23, 15 October 2019 (UTC)

Applying thrust at closest approach is to exploit the oberth effect, which is a separate concept from gravitational slingshot. They are often employed simultaneously, however. Someguy1221 (talk) 08:31, 15 October 2019 (UTC)

Interesting, I had not appreciated that they were different effects. -- Q Chris (talk) 11:23, 15 October 2019 (UTC)

well, these are means to acquire escape velocity, not to bypass the requirement, so the answer should be no (unless some "at the time of launching" is implied in the question) Gem fr (talk) 11:25, 15 October 2019 (UTC)

Obtaining carbon-oxygen compounds by burning

In the same way you can avoid getting CO by rising the temperature while burning or re-burning the gases, and obtain CO2 instead, could you tweak the burning further to maybe obtain some other carbon-oxygen compound? Would adding a third element change stuff? Can the by-product of burning, say methane or gasoline, but something else? C est moi anton (talk) 22:40, 15 October 2019 (UTC)

The burning of methane in oxygen results in a very complex equilibrium of mostly methane, oxygen, carbon dioxide, carbon monoxide and water. The precise equilibrium depends on temperature, which is of course highly variable across a typical flame. In principle you can use the data at this source to compute the amount of carbon monoxide vs. carbon dioxide generated under various conditions, but generally, following Le Chatelier's principle, we might predict that injecting extra oxygen into the reaction will reduce the production of carbon monoxide, and favor the production of carbon dioxide. See also Combustion#Incomplete_combustion_of_a_hydrocarbon_in_oxygen. It is possible to convert methane and other hydrocarbons into a variety of different compounds, and you can indeed achieve this by burning in an atmosphere with a reactive molecule other than oxygen, such as a halogen (see Haloalkane). Indeed, just having other compounds or elements present during combustion can result in traces of these alternative products being generated even when oxygen is the primary fuel. For example, setting fire to a complex mixture of compounds, such as compost, will result in a huge menagerie of products being generated. Someguy1221 (talk) 23:43, 15 October 2019 (UTC)

While there are other oxygen-carbon compounds than CO2 (such as the aforementioned CO and the ones noted below), it is important to note that CO2 is the lowest energy state for a carbon-oxygen compound. That is, all other forms of C-O compounds have more chemical potential energy than does CO2. Since burning is an exothermic process (that is, it turns potential energy into kinetic energy), it tends to stop once the potential energy minimum is reached. More exotic C-O compounds, with more oxygens, require an endothermic process (i.e. it requires us to turn kinetic energy to potential), which would require an entirely different mechanism than burning. --Jayron32 12:22, 16 October 2019 (UTC)

You may also be interested in the Oxocarbon page, although most will not be made by burning! I like carbon pentoxide. Graeme Bartlett (talk) 10:58, 16 October 2019 (UTC)

• As explained above, CO2 is the most stable oxygen-carbon compound at room temperature and pressure. In practice CO and CO2 are the only C-O compounds found in significant quantities at the end of combustion processes, and increasing temperature tends to further burn the CO (as long as there is excess oxygen), but it is not true that increasing the reaction temperature will necessarily increase the fraction of the room-temperature-stable compound.

For instance, in internal combustion engines, increasing the combustion temperature can increase the amount of NOx because at the combustion temperatures such compounds get formed and they do not separate into the (more stable) N2/O2 when brought rapidly to low temperatures. Tigraan^{Click here to contact me} 10:12, 17 October 2019 (UTC)

That's a great example of the difference between chemical kinetics and chemical thermodynamics. At high temperatures, the NOx compounds are more stable thermodynamically. At low temperatures, the NO2/O2 mixture is more stable. However, there is a large activation energy "hump" to get over to get from NOx to N2 & O2, and at lower temperatures there isn't enough ambient energy to get over that hump. The NOx products are what we call metastable, but they have a stupidly long half-life, long enough that on human timescales we consider it stable (even though it doesn't technically exist at the lowest energy state for the given temperature). Processes that are thermodynamically stable, but kinetically difficult don't happen on time scales necessary for easy human observation. --Jayron32 11:15, 17 October 2019 (UTC)

For that idea in a more macroscale context, see Pitch drop experiment. DMacks (talk) 04:12, 18 October 2019 (UTC)