Wikipedia:Reference desk/Archives/Science/2006 November 8

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2006 (UTC)

It's not a typical cell like those that you encounter in bodily tissues. It is a gamete, essentially half a cell. --Russoc4 21:12, 8 November 2006 (UTC)
This is just so weird to think about. So what organelles do gametes have? — BrianSmithson 22:38, 8 November 2006 (UTC)

See Ovum and Sperm for more details. bibliomaniac15 Review? 00:06, 9 November 2006 (UTC)

All of your mitochondria come from your mother's egg. That is true of all vertebrates as far as I know. The sperm's mitochondria do not survive in the zygote. alteripse 01:11, 9 November 2006 (UTC)

Contents

[edit] Repent! The End Is Nigh!

I was thinking about how the gravitational pull of the moon gives us tides, and how that body of water goes ahead and absorbs energy which I figure must come from the moon's orbit and the moon will have to change it's orbit to accomodate loss of energy. I can't remember whether it will move further or closer but there is a loss of potential energy if it moves closer, so is the moon gonna fall in on earth? --Username132 (talk) 16:15, 8 November 2006 (UTC)

Farther. Good explanation [1] here. JBKramer 16:19, 8 November 2006 (UTC)
Hey Kramer, thanks for the article, but there are a few things I don't understand. Why is this?

it h

when it's in the part of its orbit closest to the Sun, it's closer, but when it's in the part of its orbit farthest from the Sun, it's farther away.
Maybe I am misreadig this, but I interpret this to mean when the moon is in it's orbit around the Earth it is closer to the Earth when it is closer to the Sun, and farther away from the Earth when it is on the side away from the Sun. This is counter-intuitive to me as the Sun should be pulling it away from the Earth when closer to the sun, and pulling it closer to the Earth when on the far side.
Please sign your posts. The article means that the Moon is, when its orbit has grown, even closer to (or farther from) the Sun at those times than before: because its orbit is bigger, its distance to the Sun varies more (and reaches higher maxima and lower minima). --Tardis 19:40, 8 November 2006 (UTC)
This is also confusing.
Tidal friction, caused by the movement of the tidal bulge around the Earth, takes energy out of the Earth and puts it into the Moon's orbit, making the Moon's orbit bigger (but, a bit pardoxically, the Moon actually moves slower!).
The moon should move faster when more energy is added to it's orbit. Now, the angular velocity slows down as it takes longer to make it around the Earth, but the article does not make that distinction.
No, it really goes slower. Look at [[orbital tidal locking, with the Earth always having the same face turned toward the Moon, as well as vice versa; as I said when this came up in the "blowing up the Moon" question just above, I think the resulting "day = month" would be about 40 of our present days. For the Moon to fall for this reason is impossible; that could only happen if the day was longer than the month, so the forces would act the other way. --Anonymous, 05:00 UTC, November 9.

Oh, okay, I understand. So eventually some poor people will be stuck with an eternal eclipse and places would get awfully cold while the sun wasn't shining on them?--Username132 (talk) 10:53, 9 November 2006 (UTC)

I'm not sure where Anonymous above got the some of his/her ideas. First, the idea that angular momentum from the Earth would be transferred to the Moon. Second, that there is only one particular speed is possible for a given orbital radius. Third, the idea that the Moon moving further away from the Earth would contribute to tidal locking (the same face of the Moon always faces the Earth already and tidal locking would cause the same face of the Earth to always face the Sun)
It is possible that the Moon could collide with the Earth, although not before the Sun dies. The Moon (as well as any other body in orbit around any other body, or even any accelerating body) loses energy via gravitational radiation. In the case or orbiting bodies this will cause them to orbit more closely the center of mass of the system. This would, however, take an extremely long time to happen and there are far better things to worry about.
First, because angular momentum is conserved and has to go somewhere. The relevant force is acting between Earth and Moon, so if one loses angular momentum, the other gains it. Second, Kepler's Laws. Third, because tidal locking is the end situation for the process we're talking about. The Earth feels a stronger tide from the Moon than from the Sun (tide varies as m/r³) and would become locked to the Moon, not the Sun. --Anon, writing in a hurry, 02:54 UTC, Nov. 10.
Well orbital velocity depends on the relevant masses of the bodies as well as the distance between them. Ergo not all orbits at the same distance have the same period. Kepler's (third) law (actually formulated to describe motion of planets around the Sun) do hold for systems of bodies of the same masses and ensures conservation of orbital angular momentum - ignoring intrinsic angular momentum. If you move the Moon further from the Earth but decrease its velocity (as per Kepler's law) you will not increase its angular momentum.
It is possible to show how the Moon may move further from the Earth, but it requires a general relativistic treatment.

[edit] Buyoancy of wood

I have a piece of driftwood that I want to sink to put in my aquarium. I know it will take a while for the wood to soak enough to no longer float. Is there a way to speed the process?

TrekBarnes 19:39, 8 November 2006 (UTC)

Increased pressure? (That is, put it in some kind of a pressure vessel and apply pressurised water.) (I ASSUME that the heat of a pressure cooker would damage the wood.)
Add some non-toxic ballast, concealled within the driftwood? Rocks? Stainless steel? Embed or cement the driftwood into a rock or concrete base?
Atlant 20:01, 8 November 2006 (UTC)
Aquarium driftwood is supposed to be boiled for a couple of hours before it is placed in the aquarium AFAIK. Reducing buoyancy is not the only reason this is done for. Cooking the driftwood also disinfects it; that is, reduces the tendency of wood to rot and, more importantly, reduces the tendency of fish to die... Also, cooking removes excess resin and sap. The resin, especially of conifer driftwood, is certainly not something the fish would like to swim in. So, just keep your driftwood in boiling water for a couple of hours, weighted down by some iron (I used a pair of weights I exercise with). Beware that boiling the driftwood can be quite messy; the vessel will no longer be suitable for cooking food. Let the driftwood cool completely before placing it into aquarium, and let your filter run for a day or so after you put the driftwood in; only then you can start to populate the aquarium with fish. --Dementios
Oh, and there is still a chance the driftwood would float even though it was boiled. Apparently, boiling removes most of the trapped air, but not all of it. In such a case, weight the driftwood down in the aquarium with a decorative stone piece (also boiled, to disinfect it). Hope this helps. --Dementios

If it's well-weathered driftwood that I gather from the lake, and sunbleached, I just weight it with rock and put it in. You should have some cleaner fish that really like to chew driftwood! --Zeizmic 00:23, 9 November 2006 (UTC)

My guess is the cleaners eat bacteria/fungi growing on that wood not the wood itself! -- 85.179.3.83 11:47, 10 November 2006 (UTC)

[edit] Transit of Mercury

Survey: before reading this, did you know that a transit of Mercury is going on right now? Just curious. --Bowlhover 21:43, 8 November 2006 (UTC)

Note: transit will end November 9 00:10 (UTC).  --LambiamTalk 23:13, 8 November 2006 (UTC)
Yes
  • Yup. Melchoir 21:53, 8 November 2006 (UTC)
  • I did. --Cody.Pope 22:45, 8 November 2006 (UTC)
  • I did, i just saw it through a telescope around 1 hour ago. there is also a rather large sunspot at the moment, it appears bigger than mercury. Xcomradex 23:13, 8 November 2006 (UTC)
Lucky you. I waited to see the transit for more than a year. It was clear for the entire week last week, but it's completely overcast today. (Oh well, at least I saw the 2004 Venus transit by an incredible stroke of luck.)
By the way, which sunspot did you see?? --Bowlhover 23:28, 8 November 2006 (UTC)
my sunspot was roughly where that arrow is, at about the 8 o'clock to 8:30ish (top of the sun being 12:00). at the time, mercury was at about 1:30 position, about 1/4 to 1/3 of a radius in from memory. but from the simulation, i'd say the image was inverted. Xcomradex 00:18, 9 November 2006 (UTC)
it looked a lot like this[2]. Xcomradex 00:35, 9 November 2006 (UTC)
  • A'yup, I knew -- but New England has been overcast. 'Darned shame, too -- I got some nice pictures of the transit of Venus not so long ago. -- Atlant 17:19, 9 November 2006 (UTC)
No
  • No. But I knew that they could only happen once every \frac1{\frac1{88}-\frac1{365.24}}\approx116 days or so. (Not that they do that; the article seems to suggest that about 5% of the potential transits occur due to inclination and such...) --Tardis 22:40, 8 November 2006 (UTC)
  • No. As long as Mercury isn't retrograde...  --LambiamTalk 23:13, 8 November 2006 (UTC)

[edit] Animal twins

When mammals get litters or 4 or more offspring, are they from one egg cell (like identical human twins) or an egg cell each (like non-identical twins) or a combination thereof?

  • They're certainly not always identical -- look at any litter of puppies or kittens. Are some of them identical? Sometimes, I imagine -- and I'd guess about as frequently as human identical twinning. --jpgordon∇∆∇∆ 23:05, 8 November 2006 (UTC)
  • Nine-banded armadillos, however, always have identical quadruplets. StuRat 23:17, 8 November 2006 (UTC)

It's normally non-identical twins. Of course, there're exceptions, as StuRat has pointed out. --`/aksha 11:13, 10 November 2006 (UTC)

[edit] Viagra

1) Do you need a prescription to get it in Canada? (Vancouver, BC)

2) Does it increase stamina for men with no rectile problems at all?

3) Is it safe.. side effects?

4) How much does it cost?

Viagra is for erectile dysfunction, not "rectile" (although, the gay partners of men taking Viagra might possibly suffer from rectal problems, as a result). StuRat 23:13, 8 November 2006 (UTC)
Oo! Do you think thats wise?--Light current 23:58, 8 November 2006 (UTC)


1) Dunno.
2) Yes.
3) You can have a heart attack during sex.
4) Check your email.
--Kurt Shaped Box 00:39, 9 November 2006 (UTC)
1) Yes, though my information is 3 years old and there was talk of releasing it non-prescription even then. There may now be a low-dose version that can be obtained off-the-shelf.
2) For men without erectile difficulties, an increase in stamina isn't necessarily a good thing and can cause problems, not to mention discomfort.  freshofftheufoΓΛĿЌ  03:06, 9 November 2006 (UTC)

1) Do you need a prescription to get it in Canada? (Vancouver, BC) - Yes
2) Does it increase stamina for men with no rectile problems at all? - maybe
3) Is it safe.. side effects? - see Viagra#Contraindications and Viagra#Side_effects
4) How much does it cost? - ask your pharmacist
- Cybergoth 22:33, 9 November 2006 (UTC)

[edit] Zinc Production in Port Pirie, South Australia

What are the benifits of Port Pirie as the location for a zinc smelter? I believe it has something to do with the deep ocean bay or dock, but I am looking for more specific answers. --203.28.159.168 23:12, 8 November 2006 (UTC)

Possibly the proximity of Broken Hill which had one of the largest Pb-Zn-Ag orebodies in the world. The article on Ore genesis might have more helpful links.---Sluzzelin 23:54, 8 November 2006 (UTC)
Also, have you considered that there was also a town already there before the smelters were built, which is easier than starting from scratch. --Robert Merkel 01:07, 9 November 2006 (UTC)
You also need to consider the proximity of major electicity supplies, Port Pirie is only an hour south of Pt Augusta which has a major power plant because of coal mining at Leigh Creek.