Observation Definition and 229 Threads

Had our observations shown shown that the Universe was not expanding, and was instead static, where would that have lead us as far as Cosmology is concerned?

First observation?? Dear Physics forum, Who would be, if anybody is watching, the first to sight an object approaching from interstellar space? Yours truly, Stanleverlock

I'm thinking about the two slit experiement. When you place detectors in front of the slits, the single photon of light behaves as if it has mass. But when you take the detectors away, the photon behaves as if it doesn't have mass. Could observation impart mass? Could the higgs boson...

I'm wondering how conditional probability relates to concepts of sample space, observation space, random variable, etc. Using the notation introduced in the OP here, how would one define the standard notation for conditional probability "P(B|A)" where A and B are both subsets of some sample...

http://physicsworld.com/cws/article/news/46375 Flipping spins, one proton at a time --- http://prl.aps.org/abstract/PRL/v106/i25/e253001 Phys. Rev. Lett. 106, 253001 (2011) [4 pages] Observation of Spin Flips with a Single Trapped Proton --- http://arxiv.org/abs/1104.1206 Observation...

I think I have figured out the translation for "Ryobi" I believe it means "I wish I bought a Bosch."

Ok so I've noticed in my time playing with electronics, which isn't that long, that sometime when something breaks and i just take it apart, pretend i know what I am looking for, and put it back together, it usually works. maybe circuits just feel lonely sometimes?

I'm just a physics dilettante, so if I make no sense, please forgive me. Imagine any setup that creates macroscopic effects from quantum events. The setup is isolated from observation. Schrödinger's cat would work, but I happen to like cats so we'll just say a light either goes on or doesn't...

Hello, I am given a random variable X with a p.d.f. fX(x;\theta) (depending on a certain deterministic parameter \theta) and I want to consider N sampled observations of that variable: x1,...,xN. Is it correct to consider each observation as a separate random variable xi with the same pdf...

The guiding premise of this thread is the following proposition: If fractals play a role in the behavior of partitions, then maybe, just maybe, they play a role also in the positioning of the primes; and if they do, then who is to say that the two, prime numbers and partition numbers, cannot at...

Homework Statement What is the best time of year to view the Glalactic Centre (RA=17h 45m Dec=-29[degrees]) with an optical telescope? Would it be visible from the uk?At what local sidereel time would it be highest in the sky, and what is its parallax if the galactic centre is 8 kpc away...

I'm having a bit of trouble understanding relativity, and would like some help with the following problems: 1. A spaceship passes a stationary observer at a speed that is 80% the speed of light. At rest, this ship is 65m long. What does the observer say about the length of the spaceship? How...

for... p'_n = {1 Union Prime Numbers} M_n = n-th Mersenne Number (2^n - 1) T_n = n-th Triangular Number (n^2 + n)/2 x = {0,1,2,3,13} --> F_(0, 1/2, 3, 4, 7) for F_n = n-th Fibonacci Number Then... ((p'_x*p'_2x)*(M_x - (T_x - 1))) / ((T_(M_x) - T_(T_x - 1)) is in N EXPANSION ((1*1)*(0 +...

What is an observation or measurement? If it is not known exactly I would like to at least have some good appreciation of what the fuzzyness of the boundary is.

Hello; In classical physics, measurement does not play a major role, but in quantum physics measurement plays an active role, correct? In the double-slit experiment, whether or not the path of the particle is measured - a detector finds which slit it passes through. I'm not questioning why...

I have 2 questions here. I know there is a lot of text, but don;t be scared or deterred from helping please, it is simple to understand and mostly just text/explanation. The Second one is very long, the first not so much. 1)Problem: Complete the proof of Observation 4.2 by showing that every...

«Common sense is the collection of prejudices acquired by the age of 18» Albert Einstein. At the very beginning of my small article I would like to pay attention of the reader to R. Penrose’s rather new book «Big, small and human reason» publishing house the Amphora, St.-Petersburg 2008...

I observed something odd this evening. When I inverted my ball point pen (writing side upwards-perpendicular to the ground level), there was no change in the level of ink. To my surprise, the ink started coming downwards (towards the open end of the refill) when I wrote with it ( inverted ) on...

Why are short wavelengths (of e.m. radiation say) required for observing the location of a small particle? Classically, I could imagine sending a wave train of light (or a photon) of different frequencies onto an atom in free space. Providing the electrons in the energy levels of the atom can...

So please pardon me for my naive question, before I even ask... Observation seems to be something that is more complex than what it appears to be on the surface. Another poster posed the question about Schrodinger's cat, and the fact that the cat must be an observer in the equation. However...

For some reason, I've seen several recent questions that can be answered by simply pointing to Newton's 3rd law (Action and Reaction). Then I stopped to think. The first law is observational. We've all seen enough (sort of) practical verifications of things not stopping or refusing to start. So...

In the double slit experiment, under observation, the electron acts like a particle rather than a wave. From my understanding this is because the photon that hits it for observational purposes adds enough energy into the system to affect the electron and make it chose one single path rather than...

I've never been formally educated in quantum mechanics but to my knowledge particles' behavior changes when they are being observed or measured. What causes this change and is there any theory as to why, or if it is possible to deliberately change behaviors to a desired outcome?

Homework Statement For my engineering assignment we are working in a group to research, build, test, and write a report on an observation deck. The little fork in the road we've hit is determining the tension in the cables. There needs to be a moment produced once there is between 20 and...

[b]1. An astronomer at the Dominion Astrophysical Observatory (DAO), located at latitude 48° 31' N in Saanich, near Victoria, B.C., is studying the K2 III star N'3148°α Arietis. The equatorial coordinates of α Arietis are right ascension=2h 07 m 30s and declination of 23°29' If the...

I have cola-bottle (1.5L) that is half-filled with water. The other half was air, of course. I put it in the fridge (~ -14 C) and after about an hour, before i could see ice formation but when it was very cold nonetheless, i saw that the bottle hull was deformed to the inside, the same way if...

Thinking about the hypothetical concept of time expansion mentioned in https://www.physicsforums.com/showthread.php?t=389378" made me consider something for the first time: The primary signature of spatial expansion is, of course, redshift of the light that reaches us from the distant...

Let me know if there are any errors or holes in my logic, facts, or assumptions. I was thinking in regards to time being relative to the observer and the resulting impossibility of an objective measure of time: In determining the age of the universe, our current estimation is about 13.2...

I have some very vexing questions regarding light. We seem to know so little about it. 1. What happens to light when it is not traveling ? 2. Does it accelerate in reaching C ? If not does it "jump" to C ? 3. Can it be destroyed ? If not it seems to me that the amount of light in the...

I have a simple question... say two firecrackers explode simultaneously, and there's an observer in the same reference frame at rest. The observer is standing closer to one firecracker, but since she is at rest, does she observe them to explode simultaneously? If not... I cannot find the...

In spite of the widespread ball point pen, I still use a fountain pen for calculations.. One day, I ran out of ink while writing (duh..) and opened the cap of my ink bottle to refill my pen. Now, as I opened the cap, a thin film of ink was formed around the mouth of the bottle.. in other words...

Hi, I'm a writer and I've just started researching a story about astronomy. I'm not a physicist (actually I'm a biologist by trade) but I really want to get the science right. I know a lot of work has been done lately with things like the Sloan Digital Sky Survey but I was wondering what...

I was messing around in class, and I found that there's a small set of rules one can use to draw a directed acylic graph (it looks like a tree, but isn't) such that the number of nodes at a distance d from a "start" node is equal to the (d+1)th Fibonacci number. The graph is pretty neat...

Hello I was just revising for my Quantum Mechanics A exam and was considering the 1D double well model of an H2+ molecule. As I understand it Psi2 is non zero between the wells and therefore there is some negative charge present to which the H+ nuclei are attracted resulting in a covalent...

hello, I don't really fully understand quantum mechanics, nor could I even hope to dip my toe into even the most basic of formal mathematics it uses without at least a year of study :( however, I have one quick question if I may The Double Slit Experiment with electrons As I...

As I was reading some information on Quantum Mechanics, I came across the following statement: (http://www.thekeyboard.org.uk/Quantum%20mechanics.htm) From this, several questions arose, but I'll only share a few. If indeed nothing is real until it is observed, and something must exist...

I observed a really bright star in the sky a few minutes ago its still there. Its in the west sky low just a few degrees above the horizon. I'm assuming its a planet because i live in the city of London, Ontario which is a pretty large city for Canada. I'm also assuming its Venus...

I got a vial of fruit flies from my AP Biology teacher for Christmas, lol. Gotta observe them for two weeks and then we're going to study genetics by breeding them.

Homework Statement A person fishing from a pier observes that four crests pass by in 7.35 s and estimates the distance between two successive crests as 7 m. The timing starts with first crest and ends with fourth crest. What is the speed of the wave? Homework Equations f = 1/T v = f*d...

I use to think that algebra was very fundamental but it now seems not the case. The study of functions (in general) and sets would be more fundamental. Just an observation. What do you people think?

Am I correct in thinking that the act of observing which slit a "particle" goes through causes the wave function to collapse, ergo making the source of the "particle" we detect on the back screen to actually be on our detection side of the slits rather than the emitter side? I've drawn it, in...

Tonight I happened to check a "live" lightning map for activity, and noticed something odd. In about five separate areas of activity over the State of Oregon, separated by hundreds of miles and the Cascade mountains, the strike rate of all systems were changing, but ~equal, over a period of an...

So I'm embarking through Brian Greene's magnificent book The Fabric of The Cosmos and in the quantum section he goes through the whole idea about how observation of a particle leads to collapse of the wavefunction into a definite location. He also uses the double slit experiment for photons and...

I just cannot understand the rationale behind the fact that whatever object we see 'enter' a black hole will appear to slow down to infinity next to the event horizon and never quite cross it. Would we not observe old black holes with a myriad of objects hanging around near it that it has...

Can anyone explain to me what how is the act of observation defined in quantum mechanics? It is commonly said that the double slit experiment shows that if one simply observes the state of the electron as it passes through the slits, it effects the results. Many forms of observations are...

Can 1+1 be proven? If so, then is mathematics a science?

I am new to this field as will be apparent from my questions. I have a doubt in the basics that has been bugging me for days. This is about the original double slit experiment. As we all know that in the experiment, there is a double slit and a screen that displays the result of a photon...

I want to solve this by observation: Consider a step function: F(t)=1 for 0<t< \frac{\pi}{\omega} F(t)=-1 for -\frac{\pi}{\omega}<t<0 and the same pattern is repeated over time. What should be the Fourier Series: (A) \frac{4}{\pi} \sum^\infty_1\frac{sin(n\omega\ t )}{n}...

Why is it that when observing an electron or photon it causes the wave function to collapse, surely the photons that cause this collapse were still "colliding" with it when we wern't looking. Or does it only collapse the wave function from the observers viewpoint? (I'm abit of a noob so if...

Due to people who think they know what they are talking about i have heard different anwsers to the same question. By observing a wavefunction of an electron in an experiment such as young's double slit. Does the act of physically being observed with a photon collapse the wavefunction or...