Wikipedia:Reference desk/Archives/Science/2014 November 3

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November 3

Passage of time with altitude

There was a piece on NPR this morning about time and super-accurate clocks. It said that due to relativity, the passage of time for a clock on the floor of your house differs from the passage of time for a clock hanging on the wall by one part per million.

That seems, intuitively, like a really high number to me (one second every 12 days!) - can someone give me a simple equation relating altitude to rate of time passage (compared to sea level, for example). Did I mis-hear "million" for "billion" or something?

SteveBaker (talk) 14:10, 3 November 2014 (UTC)

Physical Review Letters, 1980, Test of Relativistic Gravitation using a Space-Borne MASER, simplifying equation (1) for non-moving objects:

${\frac {\delta f}{f}}={\frac {\delta \phi }{c^{2}}}$

where φ is gravitational potential, and f is clock frequency.

Nimur (talk) 15:04, 3 November 2014 (UTC)

Thanks! That's what I was looking for. SteveBaker (talk) 20:38, 3 November 2014 (UTC)

Perhaps you listened to this NPR piece http://www.npr.org/2014/11/03/361069820/what-time-is-it-it-depends-where-you-are-in-the-universe ? The difference in clock measurements between wall and floor is on the order of one part in 10^16 (not 10^6). --Modocc (talk) 15:36, 3 November 2014 (UTC).

(I corrected an important error in my earlier comment: gravitational potential is not identical to gravitational potential energy). In more verbose notation, the equation expands (for two locations at height h₁, h₂ near Earth's surface where we can assume gravity g is a constant:

${ClockError(ppm)}={\frac {g(h_{2}-h_{1})}{1\times 10^{6}\times c^{2}}}$

...which gives a few parts per 10¹⁶, not a few parts per million - so I think I am in complete agreement with Modocc.

Nimur (talk) 16:08, 3 November 2014 (UTC)

That makes more sense....it didn't seem right that the difference should be so large. Thanks! SteveBaker (talk) 20:38, 3 November 2014 (UTC)

• So what is the difference in time (clock error) out at the edge of the Solar System where Voyager 1 is? — Preceding unsigned comment added by Richard-of-Earth (talk • contribs)

You can plug and chug using the more general form equation I listed first; and use an estimate for solar gravitational potential, $\phi \approxeq -{\frac {GM_{\odot }}{r}}$. Of course, Voyager 1 is non-stationary with respect to Sun or Earth... so you'd really want to use the full-form equation and account for velocity and acceleration, as described in the original paper. The velocity and acceleration of Gravity Probe A was non-negligible, so it stands to reason that the velocity and acceleration of Voyager are also non-negligible, given that an interplanetary, extrasolar-capable exploration spacecraft has a higher kinetic energy at launch than a sub-orbital probe. Nimur (talk) 20:55, 3 November 2014 (UTC)

Also note that it is not error. Both clocks have the same error which is not the same as clock differences in relative (relativistic) frames of reference. High accuracy clocks are needed to measure the difference. Another example is Muon decay half-life as they enter the earths atmosphere at high rates of speed. The half-life increases over the "at rest" particle. That's a real physical manifestation of different clocks (for the particle, the half-life appears as "at rest" in it's own frame but the distance is shorter through Lorentz contraction). --DHeyward (talk) 21:38, 3 November 2014 (UTC)

Fair point; although to belabor the point in my defense, the term "error" is used in a lot of technical contexts to mean "any deviation from a reference value." For example, in feedback control, the "error signal" is what drives the system to its correct value. I agree that both clocks are equally correct. I did not intend to imply that the measurement is erroneous. Nimur (talk) 04:10, 4 November 2014 (UTC)

• Thanks folks, you have convinced me. I shall go out tomorrow and buy a bed mattresses of solid lead (or better still depleted Uranium). Sleeping upon this mass, will I will be able to extend my life by a few picoseconds – err... or a bit less. Giving up wine, women and song might be more efficacious but each to their own peccadilloes --Aspro (talk) 21:58, 3 November 2014 (UTC)

I ought to know this, or look it up for myself, but as long as you're looking at it already... do the effects of time dilation by speed and by gravity match up when something is in an elliptical orbit? For example, do clocks on Earth run at different rates (relative to, say, distant pulsars) when the planet is at its closest and furthest distances from the Sun? Wnt (talk) 05:04, 4 November 2014 (UTC)

Faster speed and greater gravitational potential both act to create more slowing, so the closest approach in an elliptical orbit (pericenter) will have more time dilation than the furthest distance (apocenter). Dragons flight (talk) 10:22, 4 November 2014 (UTC)

You're right! I knew these things individually, but somehow managed to flip their signs relative one another in my head. Wnt (talk) 12:22, 4 November 2014 (UTC)

Come to think of it, I suppose this suggests a better version of the twin paradox. I've seen it argued that the difference between the twins is that one accelerates. However, if two twins pass by one another in two identical space stations orbiting a supermassive black hole, one of which is in a circular orbit and one in an elliptical orbit that goes close to the horizon, then even though the stations each remain "at rest" (though not in an "inertial reference frame" because of the presence of tidal forces) the full time, when they next pass close by one another - I think even if they have the same speed relative to the black hole or the same combined kinetic and potential energy at the point of close approach to one another - they will still have different readings on their clocks. Wnt (talk) 14:29, 4 November 2014 (UTC)

You want to obtain the answer you should generally calculate the path $s=\int ds$ in Schwarzschild metric. Ruslik_Zero 19:40, 4 November 2014 (UTC)

Lysozymes (Lysosomal enzymes) and Veganism

Before I start I want to say that I don't mean to start any ideological discussion here - I aspire to read mostly "Technical" comments dealing only with the subject:

Dr Jockers claims www.naturalnews.com/046844_lysozymes_anti-microbials_enzymes.html in this article] that some animal foods (i.e Dairy milk or uncooked eggs) can contribute Lysozymes to our Mucous membranes (I guess it's mainly the Oral and Nasal ones).

A possible notion from this article is that there are no comfortable non-animal sources for these enzymes. What do you guys think? thanks Ben-Natan (talk) 22:14, 3 November 2014 (UTC)

When you eat e.g. fat or protein, that material is not directly incorporated into the body. It is digested, then you make your own fats, proteins, etc. from the smaller pieces. From your article "[Lysozomes are] enzymes that are naturally produced by the body's secretory cells within the mucosal membranes of the body." - emphasis mine. I'm not an expert on this, but my understanding is that the human body can synthesize these enzymes without ever ingesting said enzyme. While it is true that ingesting the enzyme would ensure that the body has all the right ingredients to synthesize it, those smaller individual ingredients are most likely available in plant sources. SemanticMantis (talk) 22:29, 3 November 2014 (UTC)

The above is correct. Ingested proteins will be broken down in the digestive system and will certainly not make it through intact. But even without all of that, first thing you need to do is look at the source of the statement. It's obviously a crackpot website. That should tell you enough about the validity of the statements made on it. Fgf10 (talk) 22:31, 3 November 2014 (UTC)

Indeed, but what about the claim that the Enzymes joins similar enzymes already on the surrounding oral and nasal Mucous membrane? You think it contains no truth? Thx Ben-Natan (talk)

Not at all. As noted by both people above, enzymes you eat do not enter your blood stream as whole enzymes. Anyone who makes any claim that they do can be automatically dismissed as not knowing their ass from their elbow, and every word that leaves their mouth from that moment forward can be safely ignored. An enzyme is a protein, which is a type of polypeptide. When you digest proteins (that is, when you eat them and then they go through your digestive tract) the protein itself is denatured, that is it is broken down into smaller pieces. The process of protein digestion basically turns the protein into the individual amino acids that make it up. Proteins are VERY sensitive things; if you make only a few minor changes to the way they are put together, they stop doing their job. So eating any protein that does anything inside your body will not give you more of that protein inside your body. Your body treats all ingested proteins as indiscriminate sources of amino acids. Any proteins made by your body (including enzymes), must be built from first principles by stacking together individual amino acids, and then folding it all up into the correct shape. This is why diabetics have to inject insulin. Insulin, a hormone made of several different proteins, cannot enter the blood stream by eating it. You need to inject it directly so it isn't digested by your stomach. If you ate insulin, you'd just get it broken down into the individual amino acids, and then your body would still have to make it. Which, in diabetics, they can't do... So, the moral of the story is you cannot increase the amount of any enzyme in your body by eating it. At all. Ever. Anyone who makes such a claim doesn't know what they are talking about. --Jayron32 01:11, 4 November 2014 (UTC)

I feel bad nitpicking such an excellent and correct explanation, but I feel I must point out that denaturing is not the protein breaking down into smaller pieces. It's the loss of secondary/tertiary structure and resulting loss of function. Which is of course one of the first things that would happen to most proteins when hitting the stomach (excluding things like pepsin). Fgf10 (talk) 07:52, 4 November 2014 (UTC)

To nitpick the nitpick, protein denaturation can break proteins down into separate pieces. A protein, in large part for historical reasons, is defined more or less as a tight lump of something mostly peptide in nature with a function, but can consist of multiple protein subunits or polypeptides. Also a single proprotein may be cleaved into multiple chains after it is made and folded. It is (or at least was) quite common for SDS-PAGE to split a biochemically defined "protein" isolated in terms of its activity into several individual bands on the gel. (Nowadays reverse genetics has decreased the prominence of that approach quite substantially) Wnt (talk) 14:40, 4 November 2014 (UTC)

Conceivably, one minded to be charitable could try to argue that lysozymes might contain a perfect combination of whichever essential amino acids are needed to make lysozyme, or that the text indirectly refers to some antibacterial effect of the enzymes acting on bacteria in the food itself, but... no. These would be really strained attempts. The author simply doesn't seem to understand the biology. Even when proteins contain special amino acids (i.e. hydroxyproline in collagen) the proteins still have to be produced with plain vanilla amino acids and altered after the fact. (Except selenocysteine, which is very special; but I don't think there is any in lysozyme, though I didn't check) Wnt (talk) 04:28, 4 November 2014 (UTC)

• I don't know the answer to the OP's question, but I think I have to point out that none of the replies above actually address it. The claim, as I understand it, is that lysozymes from dairy products that you eat or drink can migrate directly from the mouth to the mucous membranes without ever going through the digestive system. It seems doubtful to me that such a process could have any functional importance, but I don't actually know. Looie496 (talk) 14:20, 4 November 2014 (UTC)

I just read the article a second time, and I don't think the linked article explicitly claims what you say it does. Anyway I think the OP basically has the answer: there may not be non-animal sources of this specific enzyme, but that has little to do with production of the enzyme in the human body. SemanticMantis (talk) 15:33, 4 November 2014 (UTC)

(EC) It's worth noting that the despite the questionable nature of the original source, it did link to the supposed sources. These seem to be only used by the early claims, but perhaps it's just internal citation. Anyway while one of these is questionable, the rest seem RS.

The first one appears to be [1] (someone screwed up the link). It's discussing modifying a (I think hen egg white) lyzosyme and testing the effect on gram negative bacteria. They do mention the possibility of using the modified enzyme in formulated food (as well as in a drug delivery system), but I'm not sure the purpose is primarily to have an in vivo effect or more to help protect the food. Either way a fairly odd choice for "natural food" promoting website, particularly once which is telling you stuff should never come from "commercialized farms" etc.

The second source is [2]. The next source [3] which mentions lysozyme is somewhat resistant to proteolytic action including from trypsin, but not from pepsin. Anyway by catalysing the lyzosomes first with pepsin, then with trypsin, they were able to find some components demonstrating non catalytic/enzymatic antimicrobial activity. Although they used hen egg lyzosyme (and were sponsored by the Ontario Egg Producers), I'm not sure they're suggesting this necessarily means there's any significance of consuming the hen egg lyzosyme (although they do mention how hen egg lysozymes are extensively use for preservation and related purposes). They mention "native lysozyme a few times, I think this means naturally occuring undigested lysozyme in somewhere.

The third one is [4]. They are looking at the possible effects in the human mouth. Although they do make a brief mention of hen egg lysozymes (and one of the other things they were looking at being in mouth washes), it's not clear that they think dietary contributions is much of a factor compared to the lysozymes naturally occuring in the saliva (although they don't seem to discuss origins much).

The next source is [5], it's not particularly relevant however it does mention:

Lysozyme is found in virtually all human body fluids (e.g. saliva, respiratory secretions and liquor*). Expression of lysozyme in the skin has been located in the cytoplasm of epidermal cells and throughout the pilosebaceous apparatus

(*)Possibly they mean Cerebrospinal fluid

Next source is [6]. Again they're looking at salivary lysozymes. They mention

Lysozyme present in the oral cavity is derived from the major and minor salivary glands, the gingival tissue and gingival crevicular fluid

and although they actually used hen egg lysozymes for their experiments, this and other stuff they mention make it clear these are just for convience and they're thinking of naturally occuring lysozymes in the saliva, not some sort of dietary constribution.

Next we have [7], this is looking at lysozyme (and lactoferrin) deficiency in babies is associated with bronchopulmonary dysplasia. They mention early on

Lysozyme is another antimicrobial protein found in nasal secretions and in many other external secretions. Lysozyme is the major protein in upper respiratory tract secretions, often representing 15% to 35% of total protein. Lysozyme is secreted along with lactoferrin by the serous cell.

they also say

The source of lactoferrin and lysozyme in tracheal aspirates of newborn infants is not known for certain.

They then go on to discuss some possibilities, including lactoferrin (but not lysozyme) from milk. I'mn not sure why they didn't consider lysozyme, but I'm pretty sure a similar conclusion still bears out namely that as some of the babies with high levels of lyzosomes were not fed and many others weren't fed much, it can't have come from there (but I even for those fed a bit of breast milk, I don't think they noticed any correlation). Finally they say:

We believe that the most likely source of lactoferrin and lysozyme is airway submucous glands. Lactoferrin and lysozyme are secreted by serous cells of the submucous glands of the adult human bronchus and nasal mucosa. Glands of the lower respiratory tract of newborn infants are also the source of lactoferrin and lysozyme.

This is quite an old article so the info may be seriously out of date, but on the whole, it doesn't sound like even in this more extreme case the dietary lysozymes had much effect. Perhaps the sample size and feeding level was too small, but the author of the naturalnews doesn't seem to have provided anything useful to suggest it does. The final source is [8]. They do suggest it's possible in infants lysozymes and other antimicrobial proteins in breast milk may reduce infections and also encourage a healthy gut microflora, and also as

Recent studies show that the addition of recombinant human lysozyme to chicken feed would serve as a natural antibiotic, possibly suggesting that it could replace currently used antibiotic drugs.

However I suspect this is mostly thinking of the proteins acting at the digestive system level and not anywhere else. It looks like our article has a bit more on this and one of the earlier sources also mentioned that breast milk lysozyme (similar to human egg but it wasn't that source) lysozyme has anti-microbial peptide sequences after digestion.

My conclusion would be that it's possible that dietary lysozyme may have a minor beneficial effect in the adult dietary system (including perhaps the mouth), but even if this is the case, it likely doesn't last very long. And there's no evidence dietary lysozymes generally end up anywhere else (and although I agree with Looie496, we probably can't rule it out, I don't think it's particularly likely unless you're regularly snorting your food or something). This probably explains why the naturalnews article didn't actually provide any direct citations for the later claims, I suspect newer sources will help with some stuff, but probably not support their theory. (Actually this all reminds me of Mānuka honey.)

Nil Einne (talk) 16:43, 4 November 2014 (UTC)

Hmmmm, it turns out that human antibodies actually are not absorbed to the blood from the neonatal intestine, unlike many other animals. [9][10] I found a cute site that suggests lysozyme works the same way as the milk antibodies, in the gut rather than by being absorbed, which lists a few refs. [11] Unlike antibodies which are essentially a learned response, there's no theoretical reason why babies can't make lysozyme that is fully effective in whatever amount that is needed, yet that site suggests that something in breast milk helps to optimize their production level. Wnt (talk) 13:59, 5 November 2014 (UTC)

If proteins were always broken down in the digestion process, why is mad cow disease spread by ingesting proteins from affecting cattle ? StuRat (talk) 12:33, 5 November 2014 (UTC)

We could say that about many viruses... clearly digestion and barrier function isn't 100%. Prions are known for being particularly resistant to just about anything you try to do to them. Apparently they have caused lymphoreticular infection in about 1/2000 Britons, being detectable in appendix that is removed for other reasons, with the level of progression to clinical vCJD still being a matter of interest. [12] Wnt (talk) 14:13, 5 November 2014 (UTC)

(edit conflict) The answer is we're not sure. See Transmissible_spongiform_encephalopathy#Competing_hypotheses which notes several competing hypotheses for how prions could be transmitted and still survive the gut; several hypotheses rely on as-yet-undiscovered agents, such as viruses or other small nucleic-acid-based agents which survive ingestion, and then produce the prions in situ. The other possibility is that the prions have some mechanism to protect themselves from the digestive process. We know that prion diseases can be acquired by eating tainted brain tissue, because it happens, but we don't as yet have a good mechanism for explaining why or how it happens. Your very question is flummoxing scientists as we speak. --Jayron32 14:20, 5 November 2014 (UTC)