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How come all the signals in the air are not interfering with each other? Say you have 3 sine waves as an example (pic related) the resultant would be gibberish. How does a router/reciever understand what is the information that is meant for it?
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Because each receiver is tuned to a particular frequency.
And then e.g. you have things as
http://ham.stackexchange.com/questions/137/what-frequencies-am-i-not-allowed-to-use-north-of-line-a-in-the-usa
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(I should add that in frequency space, your pic would be 3 functions that are very seperated from each other)
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>>8059672
Could you elaborate on how it is tuned to that particular frequency? In the example (take sine of 1Hz, 2Hz, 4Hz together) if you sample at 1Hz you'll be incapable of seeing wether it went down or up right? (As the others add their energy to the wave?)
>>8059677
Seperated how? As in in/out of sync?
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Here's something that's been on my mind lately with all the mars colonization talk...
On mars, water boils away easily, correct? How exactly does that play out with planetary heating and atmospheric thickening? What would be the proper order of events to ensure retention of as much moisture as possible? It'd be incredibly counterintuitive if we boiled away the ice caps in the process of heating the planet, turning it into even more of an uninhabitable desert than it already is.
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>>8059609
It's not really boiling like we think of it. More like evaporation.
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>>8059893
Is the moisture held by Mars' atmosphere or does the vapor escape into space? I would think water's escape velocity is high enough that Mars should be able to hold onto it, but I might be missing something.
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>>8059609
>On mars, water boils away easily
It boils because of the lack of atmosphere. You can see a similar, but less dramatic, effect on earth at high altitude. I've no idea how to answer the rest of your question.
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Hey /sci/, I know jack shit about astronomy.
How come we can observe other galaxies and shit but we apparently can't see this theoretical tenth planet?
Is it because its so dark?
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Yes. its much more distant and its not lit by a lightsource like our sun. we only discovered it because cassini recieved EM signals from the planet X
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>>8059597
Galaxies radiate light. Planets ... well ok planets do to but at a much much lower frequency and power.
https://en.wikipedia.org/wiki/Stefan–Boltzmann_law
That's the energy everything radiates at according to temperature. Apply that to any planet you want in the solar system. Remember the Sun's energy drops off significantly with distance because of the inverse square law. A planet at that distance will receive very little solar energy and emit extremely little.
Compare that to Earth for example. Earth is 1 AU (by definition) and receives 1380 Watts per meter squared. Pluto for instance is 39.5 AU. According to the inverse square law how many Watts per meter will Pluto receive light from the sun? You can then plug in to the energy balance equation to calculate at what temperature it emits light.
Compare that to stars. The sun's blackbody radiation curve is phenomenal when compared to the Earth. It radiates energy at 5778 kelvin (Earth radiates at about 285 K) and it's a SMALL STAR.
Long story short. Stars are huge radiators of energy, planets are not.
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>>8059608
Eh, sorry, here's a simpler energy balance equation that removes the greenhouse effect. In this case we can probably ignore it because Icy bodies like Pluto and further Kuiper Belt Objects will have no significant atmosphere.
It's also already solved for T
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What is the correct answer?
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50%
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-2/3 or 2/3 depending on how you solve the quadratic equation
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Always change your choice.
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Hello /sci/, I hope everyone's doing well. Let's get an interesting thread going, shall we?
There is a set $S$ of points in the plane with the property that any triangle with vertices in $S$ has area at most 1. Prove that there exists a triangle with area 4 containing all the points in $S$.
Let's see how /sci/ solves this.
(Problem is not original)
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are you allowed to make the triangle as big as you want, because then it would be easy
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>>8059520
OP here.
Let me ask you something, anon. Why are you still alive? Can you not fucking read?
'has area at most 1.'
'....there exists a triangle with area 4'
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I'm not going to autistically write out a rigorous proof for this.
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http://humansarefree.com/2016/02/big-pharma-is-injecting-us-with-cancer.html?utm_campaign=shareaholic&utm_medium=google_plus&utm_source=socialnetwork&m=0
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scary shit
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>>8059439
>Big pharma
Stopped reading there.
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>>8059439
>conspiracy
>vaccines
yadda yada into trash
An object travelling at the speed of light would have infinite mass. So, why don't we say that photons have infinite mass? Is it because it functions as a wave instead of a particle? Or is it just because infinite mass would imply infinite volume?
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It's duality phenomena
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>>8059395
photons aren't objects like you're thinking of
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>Infinite mass
Infinite momentum? How does it even work with the mechanics we know? Or is it guarded by something like: achieving c would also demand infinite amount of energy delivered.
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Could a man be so smart that others percieve him as dumb?
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Probably not. Besides, if people can only see that man as dumb, maybe he is just dumb.
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no. please stop posting.
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Yes.
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Friends! Reminding you once more there will be a transit of Mercury across the sun TOMORROW, May 9th. This event lasts 7 1/2 hours beginning at 7:12 A.M. Eastern time. The last time this occurred was 2006 and it won't happen again until Nov. 2019.
A telescope with at least 60x magnification, and a solar filter over it is the ideal way to view the event, though there will be many observatories showing live streams. One of such can be found here: http://main.slooh.com/event/transit-of-mercury/
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Western Europe, Eastern North America, and much of South America can see the entire transit. Most of the rest of the world may catch at least part of the event. Australia & east Asia is boned.
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>> Just graduated college yesterday
>> Implying I'm going to wake up at 7 am to see a fucking transit
>> What kind of astrophysicist am I
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>>8059279
I understand that's actually sadly common, for astrophysics or astronomy students to never once go out and actually look at the sky.
Anonymous
Alien Contact! When? Why? How? 2016-05-08 15:42:06 Post No.8059117
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Alien Contact! When? Why? How? 2016-05-08 15:42:06 Post No.8059117
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Alien Contact! When? Why? How?
Anonymous
2016-05-08 15:42:06
Post No. 8059117
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When do you think first contact will take place? What do you think about the great "roar" Which is blocking out signals or the object which follows earth? Post your thoughts! :)
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>>8059117
Fuckoff and die.
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Never
Never
Never
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Heard of black knight satelite?
Anonymous
Is there such thing as sensation without emotion? 2016-05-08 15:35:47 Post No.8059107
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Is there such thing as sensation without emotion? 2016-05-08 15:35:47 Post No.8059107
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Is there such thing as sensation without emotion?
Anonymous
2016-05-08 15:35:47
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I can't think of a better board to ask on
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>>8059107
u wot
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I'm not certain, but I think emotion and sensation are other parts in the brain. They are linked but not in the same place, so I guess you can have sensation without emotion if you cut that connection.
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>>8059107
hunger, pain, temperature, thirst and such are sensations aren't they?
I guess even a very emotionless person can still feel hunger, pain and etc.
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We could devolve back into monkeys if we tried or evolution is an one way street?
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>>8059073
technically that is an ape
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>>8059078
Apes are a special case of monkeys.
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>>8059073
>Devolve
Learn what evolution is before shit posting about it on /sci/
Short answer: technically, I guess.
Long answer is that we can technically a tempt to fuck up our genetics intentionally so we get a fucked up baby but that's illigal and stupid anyways.
Longer answer: http://www.nature.com/scitable/topicpage/genetic-inequality-human-genetic-engineering-768
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How would you find out the angular velocity of a wind turbine only knowing the RPM and wind speed?
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>>8059040
waaaaaait a second, is this homework?
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>>8059046
Theres a wind turbine right over there see? I took a picture of it.
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wind speed right now is 13 mph
so 5.811 m/s
and it's spinning at about 65 RPM
so angular velocity must be...
Anonymous
I don't want your opinion, I want just the mathematical truth 2016-05-08 14:40:24 Post No.8059014
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I don't want your opinion, I want just the mathematical truth 2016-05-08 14:40:24 Post No.8059014
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I don't want your opinion, I want just the mathematical truth
Anonymous
2016-05-08 14:40:24
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The function
[math] f: \{ 0,1,2,3 \} \to \{6,7\} [/math]
defined by
[math] f(0):=6 [/math]
[math] f(1):=6 [/math]
[math] f(2):=7 [/math]
[math] f(3):=6 [/math]
is surjective: Its range (the set of values, 6 and 7) indeed equals its codomain ([math] \{6,7\} [/math]).
The function has a right inverse
[math] r: \{6,7\} \to \{ 0,1,2,3 \} [/math]
For example,
[math] r(6):=3 [/math]
[math] r(7):=2 [/math]
makes it so that [math]f \circ r[/math] is the identity function on [math] \{6,7\} [/math]:
[math]f(r(6))=f(3)=6[/math]
[math]f(r(7))=f(2)=7[/math]
It's easy to write down some right inverse if the sets involved are finite.
But does every surjective function have a right inverse?
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>does every surjective function have a right inverse
Yes, this is the definition of surjectivity.
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>>8059014
https://proofwiki.org/wiki/Surjection_iff_Right_Inverse
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>>8059022
That proof uses the axiom of choice.
So I take it you say the axiom of choice is true?
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Explain this, /sci/
I am dumb but I think simple logic proves airfoils are designed upside down.
The curved surface on the top would displace more air, creating a higher pressure than the flat surface on the bottom. This means that the lower pressure area on the bottom of the foil would suck the aircraft downwards, instead of upwards.
Am I just stupid? I don't get this at all. Please help. Assume the angle of attack is totally flat and the flat foil is totally flat also.
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In this picture it's perfectly clear that the top surface has a greater surface area than the bottom, meaning it displaces more atoms and would have greater pressure on it....
Right?
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>>8058957
>Assume the angle of attack is totally flat
That's not how wings work, senpai.
...and that's pretty much the answer to your question.
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>>8058957
It's dynamic pressure, and since sum of dynamic and static pressure in.given area is constant, static pressure is pulling the wing from above and pushing from below.