Wikipedia:Reference desk/Archives/Science/2017 July 19

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July 19

Endurance running hypothesis and eating meat

I was reading Endurance running hypothesis's criticisms, and I just wondered whether humans just co-hunted (is that even a word?) with wolves. Wolves have the biological tools to hunt prey. Humans don't. It may be easier just to get a tamed wolf to do the actual hunting and reward the wolf with treats. Also, the ground is full of bugs. But is bug hunting still hunting, or is that gathering? 50.4.236.254 (talk) 05:07, 19 July 2017 (UTC)

• The main theory is that dogs are basically domesticated wolves. So the answer to the first question is yes. Tigraan^{Click here to contact me} 09:48, 19 July 2017 (UTC)

If there was any such association it would have had to be long before dogs were domesticated. And dogs seem to be descended from the Grey Wolf not African Wild Dogs or anything like that. And any instances known now of people doing persistence hunting they don't use dogs. So I would guess no, there is no evidence of anything like what you say and no reason to suppose anything like that happened. People have used dogs while hunting but that is a more recent thing than anything talked about in the article. Dmcq (talk) 11:05, 19 July 2017 (UTC)

I am never convinced by models that suppose ancient humans were not as clever as we are, nor by those that suppose they did something without a reason. Keeping a dog as a "pet" is a modern vice of the decadent; if ancient men had (future) dogs, I think they had a reason. Wnt (talk) 11:26, 19 July 2017 (UTC)

Yes, but there are other reasons besides hunting or pets. Guard dog comes to mind. Just barking to alert you to intruders is the minimum required, but attacking an intruder is even better. Keeping rats, birds, etc., away from your crops is also an easy task for dogs. Hunting with people and herding require quite a bit more breeding and training. (The hunting with people part they would have trouble with is sharing the food with the people after they catch it. That's not something wolves would tend to do. And the herding part they would have trouble with is not attacking the herd.) StuRat (talk) 14:19, 19 July 2017 (UTC)

You might find Origin of the domestic dog#First dogs as a hunting technology of interest. William Harris • (talk) • 12:15, 19 July 2017 (UTC)

There are no known instance of band of men cooperating with a pack of wolves (as dolphins are seen cooperating with sharks, for instance). And taming is NOT easy, so no sane man can think "Eh mates, look, i have an idea: this wolf may seem untractable and dangerous, but let's tame it, and then, it will hunt for us, and we'll get to keep the valuable parts and just give it the bones and refuses". Domestication of animals is not that simple. Gem fr (talk) 13:45, 20 July 2017 (UTC)

That might be true. But the fun thing is that there's nothing impossible in biology. There is no way of knowing whether ancient man hit upon principles of being a "Dog Whisperer" that allowed them to work with wolves safely. I mean, we know that somehow modern men play with all manner of dangerous beasts, even lion tamers, seeming to control them while avoiding (usually) catastrophe. I would guess this sort of art is nothing that our sheltered modern tech life away from nature would give us an advantage with. Wnt (talk) 02:29, 21 July 2017 (UTC)

I just had the pleasure of updating the lede paragraph of Dog based on this news [1] citing this paper. I really ought to make a paragraph about it deeper in to match, but the gist is that dogs have been selected for Williams syndrome. Wnt (talk) 23:14, 21 July 2017 (UTC)

motor shaft adapter

I have a worm gear with a 8mm inner hole, and it has a M4 set screw for tightening onto flats.

I have two motors:

1. 1 has a 3mm output shaft, with no flats[2].

1. 2 has a 5mm output shaft, with no flats[3].

What's the best way to mount the gear on either of these motors? I tried Googling with various combinations of "shaft", "coupler", "adapter" but nothing relevant came up. Ideally I want to mount the gear as close to the motor as possible, with a 2.5mm or 1.5mm thick "sleeve" if possible ((8-3)/2=2.5mm and (8-5)/2=1.5mm respectively).Covfefe beans (talk) 14:01, 19 July 2017 (UTC)

This sort of sleeve is often called a bushing. I got a lot of vendors when I googled for [metric bushing]. DMacks (talk) 14:15, 19 July 2017 (UTC)

Here is an insert to reduce a bore hole from 8mm to 5mm. Blooteuth (talk) 15:44, 19 July 2017 (UTC)

Good find. Then Loctite 600 series the bushing to the motor shaft, assuming the bore is slightly bigger than the shaft. However, that's a 1 kW motor, rpm unspecified, I imagine it'll make short work of any coupling design that isn't properly sized and detailed. Unfortunately a little text box here is not the ideal way of describing more satisfactory arrangements. Both motors are actually intended to use collet style couplings. Can you post a picture of the worm gear?Greglocock (talk) 18:11, 19 July 2017 (UTC)

Drill a hole through the side of the bushing and grind a flat area on the motor shaft, then you can use a longer set-screw and get a more direct transfer of torque to the gear? But that could put some unusual sideways force on the set screw. I've done it for low-torque low-speed applications, no idea about this apparent 'copter rotor part. DMacks (talk) 21:06, 19 July 2017 (UTC)

Thanks, guys, I'll try sourcing one of those bushings. Covfefe beans (talk) 23:49, 19 July 2017 (UTC)

Why is magnetism not "toxic"?

Why is magnetism not detrimental to biological processes? The body is full of metalloproteins that would by "common sense" be severely disturbed by external magnetic fields. It's easy to find extraordinary videos of what happens if you bring things made of steel near a MRI scanner, yet if you put a person inside he or she will not be effected at all (save for a pacemaker, of course) even though the body is filled with iron ions in different compounds. — Preceding unsigned comment added by 83.226.140.123 (talk) 21:10, 19 July 2017 (UTC)

If the magnetic field strength was high enough, it would indeed interfere with biologic processes. However, the proportion of magnetic materials in our cells is quite low, so that field strength would need to be extreme. For an experiment to demonstrate what I'm talking about, first observe the effect of a magnet on some iron filings. Now tape them to a block of wood, and see if a magnet still affects them noticeably. StuRat (talk) 21:47, 19 July 2017 (UTC)

Magnetic fields can indeed harm the human body. "There are established biological effects from acute exposure [to magnetic fields] at high levels (well above 100 µT) [micro-Tesla] that are explained by recognized biophysical mechanisms." From the WHO, see fact sheet here [4]. SemanticMantis (talk) 22:02, 19 July 2017 (UTC)

A changing magnetic field certainly create change in the body, as exploited in transcranial magnetic stimulation, although the effects are argued to be through electromagnetic induction.Klbrain (talk) 22:28, 19 July 2017 (UTC)

Note that a lump of steel is ferromagnetic but an atom of iron is only going to be paramagnetic. There are certainly applications for magnetic beads (hmm, that should links somewhere, but there are a bunch of relevant articles in the search results), and there are magnetic beads in many animals (magnetoreceptors) used for navigation. I have no idea if (some?) humans might have functioning magnetic organelles that could be savaged by MRI, or whether small ferrite particulates in air pollution that are transported to the brain might do additional damage. But overall, humans just make lousy magnets, and would be expected to feel far less of an effect. Wnt (talk) 01:29, 20 July 2017 (UTC)

Strong enough magnetic field would kill all unprotected persons but state of the art levitation ismagnetic fields strong enough to levitate frogs and mice by their water and they lived and likely wouldn't be hurt if there was an ethics board so magnetism strong enough to kill must be incredibly strong. Sagittarian Milky Way (talk) 04:00, 20 July 2017 (UTC)

Can methane emissions trigger other GHGs?

Are there any known or strongly-suspected feedback mechanisms whereby a release of methane into the atmosphere could trigger a release of longer-lasting greenhouse gases? (My understanding is that methane is a much stronger greenhouse gas per mole than carbon dioxide, but that it doesn't persist as long in the atmosphere, and that's why it receives less attention as a cause of climate change.) NeonMerlin 22:45, 19 July 2017 (UTC)

I suppose methane releases, in combination with other events, such as lightning strikes, could start a forest fire, which would then cause a large release of carbon dioxide and particulates. StuRat (talk) 23:40, 19 July 2017 (UTC)

• Does clathrate gun hypothesis lead you anywhere interesting?--Jayron32 02:03, 20 July 2017 (UTC)
• Every molecule of methane (CH₄) will eventually result in one molecule of carbon dioxide (CO₂) (and two water molecules). I think the CO₂ qualifies as a greenhouse gas. -Arch dude (talk) 04:37, 20 July 2017 (UTC)
• When I studied geology almost 20 years ago - ulp! this was suggested as the cause of the Late Paleocene Thermal Maximum (as we called it then). I haven't read the article fully, but it appears that is still considered a possible cause, although there are apparently "several major problems" with that hypothesis. Iapetus (talk) 11:04, 20 July 2017 (UTC)

Every such "known or strongly-suspected feedback mechanism" would be mentioned in runaway climate change Gem fr (talk) 11:54, 20 July 2017 (UTC)