# [Tycho?]

Senior Members

1192

1. ## Plumb bob

I dont really know, I'm just thinking of this off the top of my head. You would get a force vector from the wieght of the plum bob, this would be pointing to the center of the earth. Then you would have a force vector pointing outward, perpendicular to the axis of rotation of the Earth. Now before other people jump on me, "centrigual" force doesn't really exist, but thinking about it in this way can help a lot. So, you'll have those two force vectors. You'll need to figure out the angle between them, and then add or subtract some components. You'll be left with the component force vectors acting on the plum bob, and from there do a bit of pondering to figure out how it leans. Thats the best I'm willing to do without writing anything down. If you need more help, uhh, ask I guess and hope someone else answers.
2. ## Twin Planets

Oh dont mind me, I'm the jerk of these forums. My mission is to keep nonsense to a minimum. As an aside, I disagree with that first argument as yours. Even if you included Pluto's 2 other moons it would no be considered a quadruple system. To be considered a twin planet or double planet, the moon must be of a certain mass. Unofficially, the boundry is if the center of mass of the system is in space between the two bodies. Pluto and Charon orbit around a certain point in space. Earth and Luna do this as well, but the barycenter is inside the surface of the earth, so the Eearth Luna system is not usually considered a double system. Adding in Pluto's two other moons does not significantly change where the Pluto-Charon barycenter lies, hence it would not be a quadruple system. Just as Jupiter is not conisdered a double, triple, or any other sort of system. It has many moons, but these do not significantly contribute to the center of mass of the system. But yeah, dont let me discourage you from posting on these forums, I've been warned by the mods before about my attitude and you seem like a competent poster.
3. ## Plumb bob

So, whats a plum bob? Just by the way the question is phrased I assume this has to do with centrifugal [centripital] force. Assuming this is true you'll need the equation F=mv^2/r. The radius will be the distance from the point on the surface to the earths axis of rotation, which you can get with the latitude. You'll end up with some "centrifugal" force which you can subtract from gravititational force which you can also find. If this plum bob thing is hanging you might have to some extra trig work to find out the appropriate angles. If this isn't the question, then I dont know what to say.
4. ## Twin Planets

http://en.wikipedia.org/wiki/Double_planet There is no formalized definition of double planet. So its not improper to use it, especially in very easy cases like Pluto-Charon where its been called a double planet for quite a long time.
5. ## Twin Planets

What would posses you to bump an old thread for such a useless statement?
6. ## scale of quantum phenomena

Its usually very obvious if you need to take into account quantum mechanics. Ie if you are dealing with things molecule sized or smaller, its safe to say quantum effects can play a role. With things above that size you just can't measure any difference.
7. ## Antiparticles Question

Well most if not all anti-matter particles can be observed directly, so they defaintely are not just mathematical constructs. Anti-matter is a very real thing, which is why the observed inequality is such a big question.
8. ## Antiparticles Question

You're not missing anything. This is one of the fundamental questions in current physics. As far as we can tell, the universe is not biased towards matter or anti-matter. Yet, we observe everything being made of matter, and almost no anti-matter. This is very curious, and as far as I know nobody has offered a valid explanation for it.
9. ## Weird things happen at speeds close to c...

Eugh, decent post, but could you try an improve your spelling, grammar and punctuation? Trying to read about relativity should be made as easy as possible, and proper sentace structure goes a long way.
10. ## Variations in Earth's gravity

http://en.wikipedia.org/wiki/Image:Southern_ocean_gravity_hg.png Here is part of it, from wikipedia. And I guess it was wrong, since you can obviously see that its a pic of antartica.
11. ## I have an invention idea

I think I've used a device like you describe before, it was a kids toy I think. Its a decent idea for a blackboard though. The bad thing is that it may be fragile, so bumping against it or pressing too hard with the stylus may damage it (same as with electronic boards of course).
12. ## Variations in Earth's gravity

There is an interesting pic floating around the net of a "gravity map" of the earth. Some sattelite flew over the earth and measured acceleration due to gravity at each point. Its quite interesting to see how it varies, especially since it seems very random (it doesn't corespond to continents, oceans, mountains or anything else from what I can remember). Try looking up gravity in wikipedia.
13. ## change in entropy (ΔS) a state function?

For the record, this is usually more of a chemistry topic, and so future threads on the subject may be more appropriate in the chem forums. I dont remember the answer to your question though.
14. ## A year in a day

http://news.bbc.co.uk/2/hi/science/nature/5407038.stm Yikes! Those planets must be incredibly close to their stars to be able to make such a quick orbit. Well I just tossed out a quick calculation, with a period of 1 day, a planet the mass of 10^27kg (around that of jupiter) around a star of mass 10^30 (around that of the sun) I get a semi major axis of just over 2 million km (!) and an orbital velocity of 27 000m/s (!!). I have to think that planets in such a position much have fairly short life spans, as massive as they are they must be getting a ton of their mass blown off by solar radiation. Or maybe not, what do I know.

16. ## A no-arguing thread: your views in 75 words or less

I have no need for religion or spirituality. I was raised with no religious influence, and from a very young age found it totally illogical, and more harmful than good. My reason for not being religious is simply that I see no evidence that would convince me to become religious. My beefs with religion are varied and numerous. I try to be tolerant of religious people, I have several very close very religious friends. And while I am very tolerant, I dont think being religious is a decission I can truely respect, if I want to or not. I dont know how many words.
17. ## Diet COKE AND MENTOS

Yeah, thats very poor scientific method. Its clear the surface plays a role, but I doubt that's the only thing at play.
18. ## Theory about black holes

As has already been mentioned, the photon sphere is at one and a half times the schwarzchild radius (event horizon).
19. ## Theory about black holes

Angle isn't a good way to think about it, because it turns more and more as it starts to go into orbit. Not something you can easily express with angles I would think.
20. ## 1/4 impulse! light(literally) engines are here.

I would think so, yes.
21. ## us satellites outnumber the rest!

I dont find this suprising at all.
22. ## Habitable planets (new study out)

Can't really say. The conditions required for life to form are unknown, even for life here on earth. Liquid water is pretty much the prime one; if there is liquid water then you probably have the chance for life. Most of the other key characteristics can be implied by the pressence of liquid water. If there is liquid water then it is warm enough, at least for part of its year. Mass isn't really a problem; heavier or lighter than earth, life will adapt to those conditions. A fairly thick atmosphere is implied; water needs atmospheric pressure to remain liquid on the surface. Magnetic field is hard to say; its prime use would be defecting charged particles coming towards the planet that could harm life there. But a decent atmosphere should also be able to block most of the radiation, depending of course on what the star(s) in that system are like radiation wise.
23. ## Standard Model Chart

I myself would use it for just general interest stuff. I'm majoring in physics, and I dont know most of these particles. Whats a muon? Whats a lepton? A neutron is made out of 2 up quarks and 1 down, or wait, is it the other way around? It just encourages me to learn these sort of things. I also have a map in my room, it was one of the first things I bought. I dont *need* it, but its just a good piece of refference material to have around, it being in my room I tend to look at it, and learn it.
24. ## 1/4 impulse! light(literally) engines are here.

Hmm, well the wikipedia article is extremely critical http://en.wikipedia.org/wiki/Roger_Shawyer Some guy named John Spiller was in charge of verifying if the thing worked, and he said it did. But... I have no idea who this guy is, so that doesn't really explain much. Nothing has been published in a peer reviewed journal, and New Scientist has recieved some flak for being so lax in what they report.
25. ## 1/4 impulse! light(literally) engines are here.

Yeah I saw this online a few weeks ago, I just read it on Slashdot now so checked back to see if anyone made a thread about it yet... So yeah. Reactionless drives. Seems pretty sweet. I can't really judge the merits of such a device, but New Scientist usually isn't completely off the wall, especially since there is apparently a working prototype. It would be great for any kind of spacecraft. Hover cars would be way off in the distance, as you would need a ton of force to counteract gravity. Still, I hope it all turns out well. Here's a question though: I am learning relativity in university right now, and that it agrees with conservation of momentum. This drive seems to violate conservation of momentum. Does it really? Or is there a way around it using relativistic principals?
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