Mystery Definition and 872 Threads

I was staring at my calculus book when this came to me, so apologies if its a little murky. I've been thinking about Hubble time and noticing something odd, that my astronomy professor really couldn't (or wouldn't) answer. t(u)= 1/H x 10e12 years which didn't quite work because if the...

There are two magnets stuck together through magnetic force but there is a pane of glass seperating them, when I spin the magnet closest to me clockwise, both of the magnets spin and move to the right and down, when I spin them anti-clockwise, they spin and move to the left and down. The...

What causes the horizontal lines that move down a computer or TV screen when you video tape it?

We know that Truthers always tell the truth but Liars will always speak falsely. An island comprises entirely of Liars and Truthers.. Precisely 45 people attended a dinner in the island. Each one of them sat at a big round table. After the dinner was over, each of the attendees was...

How does a photon move.If it is a particle and moves in a straight line,what do we mean by its frequency in E=hf?

An evil king has n bottles of wine, and a spy has just poisoned one of them. Unfortunately, they do not know which one it is. The poison is very deadly; just one drop diluted even a billion to one will still kill. Even so, it takes a full month for the poison to take effect. Design a scheme...

1. do different people have different dreams? 2. how often does one dream? 3.what affects the dreams that one has? 4. why do we often forget the dreams we had?

The color code for hidden text is #black. Some of these questions are insanely tough. I'll post the answers after sufficient participation. 1) The first is a picture of a person who starred in a famous American sitcom of the seventies. The second is of a famous director. The third is that of...

Wow, this forum seems to be full of engineering brilliance :P. Anyway can anyone help me with this. The stages in sand casting to produce: a) solid object that is thinner at the centre than at the ends b) hollow object with two openings of diameters less than the component diameter...

In fusor you react one deuterium with another one. So you should get [SIZE="1"]4He[SIZE="1"]2. Why does it ejects one proton or neutron from nucleus?

I saw a bright green meteor yesterday. What would cause a meteor to be bright green? Is this common?

At work we have these magnetic blocks which have arms attached to them for dial indicators. They are use to hold the dial indicators like an extra pair of hands. They work great. My question is how do they work!? The magnetic block has a switch on it. This switch will turn the magnet on...

Homework Statement Why F=ma? And what is mass? Homework Equations The Attempt at a Solution

I just thought of something, imagine this scenario: You have an empty bottle of sode\water(whatever) and you hold it lopsided, at the point where it theoretically would stand still. But then move the top half a millimeter towards the center, and then release it. Then it will "fall" to the...

Here I have an elusive schematic of a 20 dB amp at around 20 MHz. It works as a unity gain amp when the control line IFG2 is open. When grounded it amplifies by 20 dB. The diode is a pin diode and supposedly has 83 ohms when the current is flowing through it. The +10 volts comes from a...

I have found a quote I've been looking for. It's the lower one in my signature right now: "Science is everything we understand well enough to explain to a computer. Art is everything else." However I don't know just who said it. Most web sources say David Knuth, but some say Donald Knuth...

Today the professor wrote down the following for use in an integral: \frac{1}{2}cos(2\theta)=sin\theta cos\theta i am not sure is this is correct. i have tried to prove this and cannot, i have also not found it in an table of trig identities. Is this a valid identity? i am not sure since...

an electron moves within a uniform magnetic field of .2T at a speed of 5x10^5 m/s. What is the magnetic force on the electron? I used Fm=qvBSin and got 1.6x10^-14N but the answer is that it can't be determined with this info why not?

I do not know if this is the correct modern term, but it seems that particles can be thought of as wave packets? no matter what they are, what is manufacturing these packets in such a way that our universe is as we see it?

What IS this? Yesterday I was driving home from school when I saw that in the clouds there was what seemed to look like a portion of a rainbow :confused: :confused: I thought it was weird, so I took a picture of it while driving, with my cell phone, so it's not the best quality :redface...

Hey, I understand GR pretty well and I realize how and why light is constant and appears constant from any frame of reference. My question is that even though nothing can reach light speed except a photon (or massless particle), how would other photons appear to them? In other words, from a...

Ok so I mixed alum (aluminium potassium sulfate... I think), flower,and cornstarch in a 1:1:1 ratio, and put that in a covered pot and heated it till it produced no more smoke/fumes. This was an attempt to make a rapidly oxidizing powder in air. It was very blind science, I am sorry to say. It...

SkyBlue=WaterBlue? No! Hey guys, I always thought that water is blue because it reflects the color of the sky. Today when I was surfing through the web I found this webpage that says that water is blue because it really IS blue! Check it out...

faucet mystery (help!) I'm in a physics class and we have 3 sinks in the class room on the same wall.All the faucet are off. When you turn one faucet on all 3 faucet are on and the water is running from them. So; when you turn faucet 1 on , 2 and 3 are also on when you turn faucet 2 on , 1...

can anyone please help me with this. why is 0! = 1? :confused: thanks in advance to anyone who can help.

if a standing wave is a wave which transfers no energy, how is it that a guitar string produces a sound? because it produces it via a standing wave, and the sound is sound energy, so where does the energy come from?

I have this problem I just can't figure out. Current = A (Ampere) i(t)=z(e^t/(RC)) where z is the initial current at t=0, R is the resistance in Ohms and C is the capacitance expressed in secondary units as F (Farad) - Express the units of F in terms of seconds and ohms So, this...

I get the theory of special relativity, it is the logical conclusion drawn from the two facts that: a) the laws of physics are the same in all reference frames b) the speed of light is constant in all reference frames what I don't get is why einstein thought the speed of light was constant...

I understand why mechanical systems that are not capable of self repair wear out, but for years now I've been totally puzzled as to why things which do not have wearing parts wear out, such as - phosphores, rechargable batteries, capacitors, fluorecent lights, electrodes, vacuum tubes...

What's preventing Saturn's rings from condensing into a moon? Or Jupiter's, Uranus' and Neptune's for that matter?

a perfectly-circular pizza comes in a square box with a card in the box. the card measures 140mm by 70 mm. what is the diameter of the pizza? i tried similar squares but this did not work? any help anyone

I've just come across a problem and the equation within this problem isn't entirely explained in the text. I've searched on the net for this same 'lattice energy' equation, but there have been no results. Here is the equation: E = Aexp^ \frac{-r} { \alpha} - \frac{Me^2} {4 \pi \epsilon_0 r}...

Now this bugs me. First there were no negative numbers. Then there were no square roots to negative numbers. Then every real number had two square roots, but no word on imaginary numbers. Luckily for me, I had a calculator that told me the square root of i wasn't some other type of number or I...

In the cosmology forum I posted this statement: , to which a PF mentor kindly replied: I fully accept what he says, but would be interested if any of "the GR crowd" would like to comment further. What I am asking is: by what means does mass/energy shape the geometry of spacetime? Does...

Found this fossil on Manitoulin Island in Central Ontario - Canadian Shield area. I'd be interested in knowing what epoch they're from. I'm thinkin' it's tube worms? Graptolites? Or rebar.

Light cannot escape from a black hole; however, x-rays have been detected from black holes. How is this possible? is it because of the accretion disk? where does it come from? is that all there is to the answer? thanks

Today I'd like to draw the attention to the end of the last glacial period. Those who have looked at ice core graphs may recall that the Antarctic ice cores appeared to react first around 17,000 years ago and then with a relative mild change in isotope values (interpreted as temperature change)...

planet venus? i read sometime ago that the venus revolves in opposite direction around the sun as compared to other planets.please tell me is it true? if yes then WHY?

Or the ancient titanic, it sailed from Barfleur, anyone know anything about it? i will not give any more details so you do not go wasting your time googling, it is just that i need some details.

At a time when there was a hose pipe ban, a person down the village noticed water gushing up from her lawn, she called severn trent (the local water authority and they told her ( it is not our problem it is a natural spring) for 5 weeks this lady watched her lawn being washed down the drain...

im reading some of feynman's lecture notes, and i stumbled upon a statement which i do not understand... he says that we can use ANY three different colors to produce any other color. lets say we want to see the color X, and we use yellow blue and red (Y,B,R) then X = yY + bB + rR. where...

I was just reading about "Morgellons Disease". At first I thought this was a psychotic symptom. I've definitely heard of similar crawling sensations experienced by schizophrenia sufferers. But it sounds like there might actually be a strange dermatological condition that these people are...

I am new to number theory and i so far like it. I recently found this problem but there was no explanation of how they got it and i was wondering if any of you knew how they got it. It is this: 1/3+1/3^2+1/3^3... + 1/3^n=1/2(1-1/3^n) Then they used: 1/4+1/4^2+1/4^3... +...

carol's age in years, can be expressed by reversing the digits in her father's age, in years. the sum of the digits in each age is 10. the positive difference between carol's age in years, and her fater's age in years___36 a.> b.< c.= d.uncertain In my opinion, there are four pairs...

Pi is the most interesting number. I was thinking about the value for Pi that is accepted by the Scientific and Mathematic community, which starts off as 3.141592653... and so on to infinity. My question is, How did they get this value of Pi as the most approximate? Did they use extremely...

Ok, every time after i use my bed i make it, three times this week i have found money on it when i next go to use it, now i am the only one that lives here so i must be putting this money between 30 and 40p on the bed, but for the life of me i can not remember doing it, i must be leaving...

What is the real answer to the mystery? http://www.chicagotribune.com/news/nationworld/chi-0605010196may01,1,5656742.story?coll=chi-newsnationworld-hed&ctrack=1&cset=true

http://www.signonsandiego.com/news/northcounty/20060423-9999-1n23bigboom.html

Hi, all; An interesting question was posed this morning by the science correspondent on Canada AM. Apparently, it's also in New Scientist magazine. He claims that it's unsolved, and I figured there's no better place than PF to go when searching for engineering solutions. I'm putting it in GE...

I got this question on my physics test "What will happen if you blow over a piece of paper?" I answered that with enough blowing, the wind created would make the paper fly off. Apparently according to my teacher, the correct answer was that from Bernouilli's theorem, the air velocity above...