Science desk
< February 21	<< Jan \| February \| Mar >>	February 23 >

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.

February 22

Ancient civilization

Suppose that 200 million years ago, another species became just as intelligent as humans are today, and invented exactly the same technology. They had cities, infrastructure, satellites, landers on Mars, etc. Then they went extinct, having lived on Earth exactly as long as humans have. Would we expect to find any record of their existence, or is the fossil record so incomplete that all their accomplishments would squished into an invisible layer of rock? In fact, is there any evidence that something like this didn't happen earlier in Earth's history?? --140.180.254.70 (talk) 03:38, 22 February 2014 (UTC)[reply]

The burden of proof between two competing propositions generally lies with the person who makes the more extraordinary claim. We can safely presume that no such civilization has ever existed because prima facie the claim that one did and left no trace is ridiculous. See evidence of absence for discussion of the lack of a need to prove a negative (as in "You can't prove a negative", the trite statement that it's impossible to prove that something which doesn't exist doesn't exist; the burden lies with the person asserting it's existence to provide said evidence of existence). However, your basic outline of events (with some modifications) has made a LOT of money for popular pseudohistorical bullshit artists like Erich von Däniken (Chariots of the Gods), Graham Hancock (Fingerprints of the Gods), Immanuel Velikovsky, (Worlds in Collision), L. Ron Hubbard (Xenu), and many many more. --Jayron32 03:54, 22 February 2014 (UTC)[reply]

(OP here) You misunderstood my question. I was asking how much of an impact human civilization has on the geological record, not proposing that an ancient civilization existed 200 mya. To rephrase the question, suppose that humans go extinct tomorrow. 200 million years later, another intelligent species arises and develops the same science we have today. Will they have any evidence that we existed, or will they think they were the first intelligent life on the planet? --140.180.254.70 (talk) 04:57, 22 February 2014 (UTC)[reply]

Certainly enough to leave some trace that could be easily spotted and identified. We have clear evidence of bones from 200,000,000 years ago, and human civilization is made of much more resilient material than that. --Jayron32 05:05, 22 February 2014 (UTC)[reply]

(ec)The possibility of a highly advanced civilization leaving no trace of its existence seems doubtful, but it's a bit like backwards time travel: It might be possible, but there's no known evidence, so the best science can do is to hypothesize on what such evidence might look like, and see if anything turns up. The basic premise of the OP's question reminds me of the plot of Forbidden Planet, in which an ancient, extinct race on another planet had developed an underground network of self-maintaining machinery which is still operational 200,000 (though not 200 million) years after its inventors had perished. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:59, 22 February 2014 (UTC)[reply]

Which human artifacts will last 200 million years ?

This seems to be the Q the OP is after. Most human artifacts will be dust by then, but maybe some can survive. How about precious metals, like gold and platinum bars ? Maybe cut diamonds ? Nuclear waste might not decay in that time, but I doubt if it would remain contained. Presumably our geologic layer will have all sorts of radioactivity and strange chemicals left in it. And global warming may leave records behind, as well. StuRat (talk) 06:21, 22 February 2014 (UTC)[reply]

Well, bones don't remain after 200,000,000 but evidence of bones do, fossilized bones are not bones, but rocks which take the shape of bones through various geologic processes. Evidence of human civilization would be blatantly obvious even if the actual objects don't exist anymore, evidence of their existence would be plain and obvious even to untrained professionals. Not like traces of chemicals that experts would test for, but stuff like impressions of artifacts left in mud which hardened into rock. I suspect that even the actual artifacts themselves remained, but even if none did, imagine finding the impression of some random device preserved in sedimentary rock like a TV remote control or some kid's toy truck. Again, it wouldn't take an expert to deduce the existence of our civilization from such evidence. We leave a LOT of detritus around this planet; it's going to be here a LONG time, and evidence of it would be plain and easy to spot under any expected conditions short of the entire planet turning into molten lava and recooling. --Jayron32 06:31, 22 February 2014 (UTC)[reply]

Who's looking? There's a probability that plants and animals will all die off due to a CO₂ deficit that kills plants. I'm betting the artifacts that can be found are spacecraft sent into interstellar space. Moon artifacts may remain. Glaciation cycles might just destroy every piece of construction. There likely won't be life intelligent enough to identify human artifacts in 200-500 million years. The die-off of big-brained human cousins and predecessors says that Darwin is not particular about selection. We may be a one-off curiosity "full of sound and fury; signifying nothing.” --DHeyward (talk) 06:54, 22 February 2014 (UTC)[reply]

Glaciers don't normally cover the tropics, although they apparently did during the Snowball Earth period. StuRat (talk) 07:34, 22 February 2014 (UTC)[reply]

If, as you suggest, humanity gets extinct today - after all, today is a Ragnarok-event, so that would be quite fitting - then the way it got extinct might have an impact on whether we would be detectable in 200 million years. If something covered the world carefully, chances are up. For example, a global mudslide, ashes from a volcano that erupted and covered the world in ashes would help to preserve traces. I would guess that the great wall of china, and other large constructions, if carefully covered, would be possible to find in the future. If the lightning bolts from Mjölnir, the hammer of Thor, smashes up the entire earth, chances are much less. Possibly the remnant of some perfectly cut diamonds might be the easiest to see intelligence in, if found? DanielDemaret (talk) 07:19, 22 February 2014 (UTC)[reply]

The stuff on the moon, where there's not really any weather or geologic activity, should be as-is pretty much 200 million years from now. We've left a few moon mobiles and stuff there. They are human artifacts, just not on earth. 75.75.42.89 (talk) 15:02, 22 February 2014 (UTC)[reply]

That's an interesting thought, but would micrometeorites pulverize any objects into dust by then ? StuRat (talk) 17:04, 22 February 2014 (UTC)[reply]

Consider that rock formations such as the Burgess Shale preserve fossils of soft-bodied animals from more than 500 million years ago. If they can survive, many many types of human artifacts can survive well enough to be recognizable, in sufficiently stable rock formations. Looie496 (talk) 17:18, 22 February 2014 (UTC)[reply]

There are several very long lasting legacies of the anthropocene which should be evident in the lithospheric record:

One of the chief activities of the industrial world has been to mine metals from deep in the earth, transport them across the surface, refine them, and then dump the goods made from them (sometimes via the hydrosphere or atmosphere, or sometimes directly back into the top layer of the ground). So a vertical core taken in the future should show a profound anthropogenic metal layer, which contains all kinds of metals at a significantly higher rate than the human-free layers above and below it. Moreover, the distribution of metals within that layer is quite unlike the natural distribution of metals in the Earth's crust. If, for example, one plotted the concentration of iron in this AML, one would see peaks for cities and higher still for industrial zones and scrapyards within them.
The Holocene extinction should be evident when comparing the fossils from before and after the anthropocene stratum. The co-incidence of the AML and the Holocene extinction will look rather like the KT Boundary.
Weisman's The World Without Us speculates that very large mining operations like the Ekati Diamond Mine or Mountaintop removal mining impose such a disruption to the strata about them that evidence of them will last for a very long time. When the next ice age backfills Ekati, the random moraine left in it will be entirely unlike the rocks in the various strata which will be horizontally adjacent to it. Unlike the extinction and the metal layer, these artefacts will be vertically significant (not just a thin stratum) but they'll be evident only in a very few specific locations. Perhaps in 200 million years Ekati will be like a miniature Chicxulub crater, evident in deep and detailed geological scans.

Some of the scientists arguing for the classification of the anthropocene (e.g.) argue that other human activities (like deforestation and climate change) will produce evidence too - but the Earth's climate changes a lot in geological time, as does the oceans' chemistry and the pattern of vegetation, so it'd surely be difficult to distinguish the civilisation-induced one from all the many and disparate natural ones. -- Finlay McWalterჷTalk 00:06, 23 February 2014 (UTC)[reply]

Certain kinds of concentrated radiation might qualify. Shadowjams (talk) 01:44, 23 February 2014 (UTC)[reply]

200 million years from now they may be decoding CDs containing the entire Wikipedia that were burried in stable rock formations in Australia. They may well be trying to decode this very discussion from 200 million years ago. Count Iblis (talk) 17:46, 23 February 2014 (UTC) [reply]

LOL, CD's are one of the most unstable ways to store data, and are lucky to last 10 years. We might as well store the data as Buddhist sand paintings. StuRat (talk) 19:35, 23 February 2014 (UTC) [reply]

It's possible even to recover preserved pigment (melanin) in fossils 200m years old. [1] Now melanin is a remarkable polymer, and surely many of our modern plastics and inks will not hold up so well, but I would expect no small fraction of our garbage dumps to remain visible to future paleontologists, who may marvel at the readability of our candy wrappers. Wnt (talk) 13:33, 24 February 2014 (UTC)[reply]

We know what would likely last, and what the objects are, but a successor species might not. There is so much plastic around, that any remains may well be interpreted as the results of a natural process! --Auric talk 13:56, 24 February 2014 (UTC)[reply]

Visual impairment

I have in the last few months been diagnosed with degenerative neuropathy. I have been given a report on my vision as follows

Correction with lenses at best level found Right 6\19. (~5.25 \ ~0.75 x 165 )

Left 6\19. (~5 \~0.5 x10)

Near N4. Unaided

What does this mean in plain terms other than "you are almost blind" which is about all anyone is telling me.

I am not requesting some legally binding diagnosis, I am just trying to understand what is happening while I try to adapt to some very large changes.

Please let me know whether you can help, I tried to look at some entries but could not reconcile the content to the information I have. Shaddarra (talk) 05:37, 22 February 2014 (UTC)[reply]

It looks like an eyeglass prescription to me. 6/19 is a metric measurement of visual acuity, there's a chart in that article that explains what the measurement means. The 5.25, 0.75, 165 look like the three numbers usually assigned to an eyeglass prescription, which are (in order) 1) straight vision correction (spherical lensing) 2) astigmatism correction (cylindrical lensing) and 3) the axis (the degrees off the vertical meridian that the astigmatism correction is "turned". The article on eyeglass prescription explains these measurements in more detail. --Jayron32 06:06, 22 February 2014 (UTC)[reply]

You best bet is to visit an ophthalmologist (not optometrist) for prognosis. The numbers are prescriptions for what they van correct but your real question is about what they can't correct and what the prognosis is. Only your ophthalmologist can answer that question. I would consult an ophthalmologist ASAP to get an opinion on your particular condition and prognosis (optometrists are not medical doctors so while they may recognize disease and prescribe lenses to compensate, you may want an overall opinion on your medical condition). --DHeyward (talk) 07:09, 22 February 2014 (UTC)[reply]

Saw an ophthalmologist, said come back in six months to see how much more of the optic nerve has died. No suggestions as to prevention of further loss and a suggestion I consult a neurologist, I am waiting for an appointment — Preceding unsigned comment added by Shaddarra (talk • contribs) 10:55, 22 February 2014 (UTC)[reply]

Searching for "degenerative neuropathy + vision" tends to throw up entries for Optic neuropathy - you may have better results searching for that. Richerman (talk) 11:14, 22 February 2014 (UTC)[reply]

Obviously you deserve much better medical help than this, someone who can explain exactly what is going on. You should find out more about what the specific condition you have is, the underlying cause of that condition and how to fight it ASAP. I don't know how long they have you waiting for an appointment, but most of the damage for one type can be within two months^[2] (though in other situations it can get better on its own^[3]) It is commonly said that acute loss of vision is a medical emergency, and you should have the right to treat it as such. Also -- this is not a suggestion of what you have; however -- it might be useful if you can observe if there is a particular time of day or night when your vision has gotten worse.^[4] There may even be ongoing clinical trials for very specific situations.^[5] Things like this are easily found on PubMed with the right search terms (this is but a sip from the fountain), so if you pay for a diagnosis, make sure you walk away with it in your hand. Wnt (talk) 13:25, 24 February 2014 (UTC)[reply]

Quick wash on washing machines

Is the quick wash setting on washing machines effective for killing microbes, and removing stains, grease and dirt? Some washing machines take 2 hours without quick was and this is shortened to an hour or so with quick wash. 82.40.46.182 (talk) 10:22, 22 February 2014 (UTC)[reply]

A large proportion of (quality?) clothes recommend washing at 40C or below, environmental recommendations are to wash at 30C, and (on our washing machine) both quick wash and the default standard wash are 40C. That's not going to kill many microbes. (You could of course wash at 60C, which I suppose would kill some.) I would imagine the effect is more to wash away the microbes, perhaps after dissolving the dirt/grease that they are living in and/or feeding upon (which is where the detergent comes into it).

My observations(!) suggest that some minor stains are removed by quick wash, some by a full wash, and some by neither. It seems to me that if you are washing clothes that you know are dirty (as opposed to just "worn for one day" and maybe sweaty) or stained, full wash rather than quick wash makes sense. (Since it would be pointless to do a quick wash, discover the stain is still there, then do a full wash.) For clothes that have merely been worn for a day, quick wash is fine. Having said that, if one has a full load of laundry then one might as well use full wash, since presumably some of the laundry might need it. --Demiurge1000 (talk) 10:50, 22 February 2014 (UTC)[reply]

As with hand washing with soap, the main aim of low temperature washes, as Demiurge said, is the physical removal of microbes rather than killing them. Washing machines with only a cold fill water connection tend to take a long time for the high temperature washes as they have to heat up the water they use - something to bear in mind when buying a new machine. We tend to wash most things on the quick cycle but spray any grease spots just before they go in with a kitchen cleaning spray to break up the grease. This gets the stains out most of the time and, providing you use a bit of common sense and don't use a spray containing bleach or acid, doesn't damage the clothes. Richerman (talk) 12:16, 22 February 2014 (UTC)[reply]

You may not want to read some research in How Nasty Germs Survive in Your Washer. Alansplodge (talk) 13:47, 22 February 2014 (UTC)[reply]

Physical removal of microbes is quite sufficient, with one exception I'm aware of, the microbes which cause mildew. I've found bleach to be the most effective way to kill those. Without bleach, the clothes seem OK if you dry them immediately after the wash, but the mildew microbes are just dormant, and if you leave them damp later (say a bath towel left in a humid bathroom after you dry off with it), the mildew smell quickly comes back. If you bleach them, this doesn't happen. Of course, bleach can also damage some clothes, so you need to be selective in it's usage.

As far as removing greasy stains, hot water helps here, but you could likely compensate for cold water by using more detergent. Environmentalists might not like this, though, so spot treatments would allow you to target a smaller amount of detergent directly on the stains. Ideally you would apply all the detergent directly to the stains (this requires liquid detergent), and add none separately. StuRat (talk) 14:05, 22 February 2014 (UTC)[reply]

This is all kind of silly. Germs on clothes are almost always harmless. The only real exception is a sterile operating theater, and even then it is essentially impossible to sterilize clothes -- the only way to achieve sterility is to cover them entirely with paper or plastic. Looie496 (talk) 23:58, 22 February 2014 (UTC)[reply]

But how then is it possible to ensure that the paper or plastic would be completely sterile? 24.5.122.13 (talk) 02:26, 23 February 2014 (UTC)[reply]

I have no idea, but all those things are single-use items, which come in sealed packages that you open just before use -- unlike clothes, which are too expensive to be used that way. Looie496 (talk) 15:18, 23 February 2014 (UTC)[reply]

They are autoclaved or single use items have often been irradiated. Richerman (talk) 19:45, 23 February 2014 (UTC)[reply]

That's not strictly correct. There are a number of manufacturers of reusable fabric surgical gowns, drapes, and other surgical gear, which may be preferred in the operating theater for an assortment of reasons. (Google reusable surgical gowns or similar to find lots of choices.) It is true, however, that in general clothing and other fabrics are challenging to sterilize, and that typical off-the-rack clothing isn't made to stand up to the rigors – vigorous laundering followed by autoclaving – of normal sterilization cycles. TenOfAllTrades(talk) 16:40, 23 February 2014 (UTC)[reply]

Something that has not been mentioned regarding bacteria, is the advantage of washing and drying. Take one's kitchen crockery for an example. Washing removes most of the crude but does little to kill the the remaining bacteria. Placing the plates, knives and forks etc,. to drain and dry immediately, causes the fine film of 'active' bacteria remaining to desiccate and die. It is this procedure, that has reduced the incidence of food poisoning – not the detergent. One could scours the pots and pans with sand and achieve the same result. What hardened spores (not the active bacteria) which remain, are easily coped with by ones immune system. To get food poisoning or any other infection, one needs (or should I say doesn’t need) a large enough cohort of bacteria to evoke a clinical infection. So back to the OP's question. A quick wash is OK, but long-or-short, always dry the cloths as quickly as possible.For jeans and cotton shirts etc, I favour good old washing soda. Over the course of a year, it is much cheaper and really does the job. Good excuse to treat the family with a night out once in a while with the dollars saved. In an operating theatre, one's very effective skin barrier against infection has been perforated. Thus, more exacting hygiene is required. The skin barrier is very,very good. When WHO was running around the world, inoculating people against smallpox, they instructed their clinical teams to draw blood with their Bifurcated needles to puncture the skin barrier before applying the vaccine. Otherwise a proportion of each vaccinated group didn't react and get immunity, and that was for little things like a highly contagious virus. Therefore, an ordinary short wash followed by thorougher drying will be all you reasonably require. --Aspro (talk) 18:33, 23 February 2014 (UTC)[reply]

Parts still "hand" machined (without robots) for jets and cars

Are there any parts of, say, the latest Boeing jet that are made by a human running a drill press, lathe, milling machine, or otherwise human-operated machinery, which is to say, specifically not robotically manufactured? Any automobile parts left that humans do? 75.75.42.89 (talk) 13:24, 22 February 2014 (UTC)[reply]

I believe some luxury cars boast "hand-stitched leather". More important for aesthetics, though, is to manually match the leather grain, etc. Real wood has similar issues. StuRat (talk) 14:08, 22 February 2014 (UTC)[reply]

Aston Martin and Morgan are among the luxury cars in the UK that still hand-build cars. --TammyMoet (talk) 16:15, 22 February 2014 (UTC)[reply]

See The Morgan Motor Company's Hand Build Wood Car... - untouched by robot hands. Alansplodge (talk) 16:59, 22 February 2014 (UTC)[reply]

I wonder how the heat produced by the engine doesn't sear the engine mounts, or whatever the wood nearest to the engine is. Auto engines get very hot.75.75.42.89 (talk) 21:28, 22 February 2014 (UTC)[reply]

The exterior of an engine does not normally get hotter than boiling water, except for the exhaust manifold and exhaust pipe, where metal heat shields usually protect body parts. —Quondum 01:43, 23 February 2014 (UTC)[reply]

Furthermore, the engine of a Morgan sits on a steel rolling chassis, it's the coachwork that consists of an ash frame with aluminium panels fastened onto it.[6] All cars used to be built that way. Alansplodge (talk) 18:31, 24 February 2014 (UTC)[reply]

There are far fewer robots than you might think and far more human work. See 777s for example: [7] 75.41.109.190 (talk) 18:38, 22 February 2014 (UTC)[reply]

Most aircraft (including Boeing jets) are hand-riveted during the assembly of the airframe -- does this count? 24.5.122.13 (talk) 20:23, 22 February 2014 (UTC)[reply]

As a rule of thumb, the shorter the manufacture series, and the larger the parts, the less robots make sense. Other large manufacturing machinery, other than robots, may be relevant. DanielDemaret (talk) 12:09, 24 February 2014 (UTC)[reply]