Observation Definition and 229 Threads

When we say, for example, an electron does not have an exact position around an atom until it is measured, what is meant by measured? Certainly it can't simply mean measured by a human. I'm guessing it means measured in the sense of interacted with by another system. And if that's the case, when...

Say a photon was emitted from very far away such that it would take billions of years to reach us. According to Feynman's infinite paths, the photon travels every possible path on its way to reach us. The superposition of infinite trajectories collapses when it hits something solid, say an...

Homework Statement Special relativity: A rod traveling with the relativistic velocity of 0.866c moving towards a garage. The length of the rod is L, that of the garage is L/2. From the reference frame of the garage, we find the value of Lorentz factor = 2 we say that rod would fit inside garage...

Dear All, I am doing the Special Relativity course at World Science U, and came across this question which I got wrong: When 100 nanoseconds have elapsed on traveling Gracie's watch, she immediately stops, turns around, and heads back toward George at the same speed of her outbound journey...

In quantum physics, one can change a system just by observing it, such as wave function collapse and quantum Zeno effect. I don't quite get how observation affects them, unless we are interacting with them when observing them.

If two observers on Earth in different locations around the globe, were both viewing the CMB with their equipment pointing at the same point in the sky, and charting the fluctuations in it, would they correspond or vary from each other greatly. In other words, if you made a graph of the CMB and...

The QM is saying that a particle in some potential pattern will have a wavefunction that describes the probability to find the particle. And then it also said that observation will make wavefunction collapse into measured value. For example, the electron in an atom will be in one position after...

Just wanted to share this, mainly because I really liked the videos (found in the supplementary section at the end). Moderators, feel free to move it to a more appropriate place. Observation of laser pulse propagation in optical fibers with a SPAD camera Recording processes and events that...

So, proposals are soon going to be accepted for the NASA's Chandra X-ray Observatory and the professor that I am currently working on asked us to come up with ideas for a proposal, they can be anything! However, because I am just starting research, I am not sure yet what I want to observe, but I...

Hi, here are image of situation. We have observer in point A. He have clock and know distance L between points B and C. He is observing rocket travel from point B to point C at speed near light speed. Can he calculate the speed of rocket using v = L / TimeA? In rocket at point B here are...

My question about the double slit experiment is this: why is it that nobody suspects that the detectors used to detect particles as they pass through the slits in the double slit experiment aren't causing some interference with the experiment which makes it seem as though they are acting like...

Thanks in advance to all who reply. Forgive me if this naive, I am not scientifically inclined, but I am VERY curious. After re-watching a documentary on quantum physics, I have a "thought experiment" that I would like feedback on. Maybe this experiment (or something like it) has already been...

The observation model will be ##z=H\theta+v##, where ##z## is column vector containing the results, ##H## is the observation matrix, ##\theta## is the parameter vector and ##v## is a vector containing random additive noise. b.) In this case ##z##=[1 1 0; 1 0 1; 0 1 1; 1 1 1]*[##m_1## ##m_2##...

I'm wondering if anyone can answer this question for me. Suppose we send a spaceship to the moon at 299,792,457 m/s (1m/s less than c). That's 99.9999997% of the speed of light. Plugging the numbers into the time dilation formula, we get that the 1.2822 seconds that it takes for the spaceship...

To start off I'd like to apologize ahead of time for the grammatical errors and lack of eloquence that are sure to follow, it's the middle of the night and my mind is wandering but my cognitive capacity to express my self is pretty low at this time. With that out of the way, I'd like to ask...

If car passes very very very quickly in front of you, you will not be able to see it... We will not be able to observe it... As seeing is believing, So which proof we have that this car really existed and passed in front of us?I Think the concept of electrostatic isn't it?

Starting in the fall of this year, I'm going to get to start my own year-long undergraduate research project. To summarize as briefly as possible: Resources Available: Our university has access to the SMARTS consortium's three telescopes: - 1.5m CHIRON telescope - 1.3m ANDICAM telescope...

Hello. I don't know exactly if my question can be treated physically but so... Let us have a 3D space with non-constant metric. We are in the first region with a euclidian metric. ds^2=dx^2+dy^2+dz^2 So the distance between two points is got through pythagorean theorem Then near us we have the...

Premise 1: From the frame of reference of the earth, observing a thing falling into a black hole (crossing the Schwarzschild radius) is impossible -> the thing is observed falling toward but never reaching the radius, i.e. the process takes an infinite amount of time. Premise 2: Observation...

I dropped out of physics in college and have several career choices now for the near future being all vocational. In the far future I want to end up in planetary sciences again. So, I'll want to work again with planetesimals, dwarf planets, evolution of planets, their geology, and astrobiology...

Does atom really looks and behaves like as that explained in quantum mechanical model? Or is it just a Mathematical Tool to express the observations? Is it like that that scientist were unable to find any clue about real atomic structure and just created a mathematical tools following the...

I think this is just a quickie. I'm interested in what is assumed about entangled photons/particles before they are observed. Is it correct to assume that the photons/particles exist in all possible states simultaneously? Thank you.

As I understand it, in the double slit experiment electrons were found to exist in both wave and particle form depending on observation. The electron is a tiny speck of matter, and so does observation have the same effect on all matter? Max Planck said there is no matter as such. Is this because...

It is said the axiom of QM is observation.. but if observation is secondary effect of more primary dynamics that don't involve observations.. could it still be called QM, and what's it supposed to be called? In other words. Say QM is emergent from a deeper reality.. and we are to study the...

Might I be so bold as to ask a question about the "double slit experiment". Was wondering...have scientist ever considered...turning the observation on and off...? Is it even possible...? Experiment says...when observed...particles react one way...and when not observed...they react a different...

I read that state preparation is simply measuring and confirming the system. Filtering type observation is when the observation doesn't destroy the system. But googling doesn't produce the extra words "Filtering type observation".. why is these words only in physicsforums.. what are the other...

Greetings - We speak of astronomical objects as being x number of light years away, which is also a statement about the age of the data. So our knowledge of M83, for example, is about 15 million years old, etc, etc. I'm just wondering why there never seems to be any attempt to move this...

Is it possible to rig a Truss Dobsonian telescope like this one so that you can control it remotely from inside of a building while the telescope itself is on the roof of the building? Then is it possible to attach some sort of adapter to the telescope that would allow you to hook up a camera...

[Moderator's note: this discussion has been spun off from another thread.] This is probably a silly idea, but I haven't got any reputation to preserve, so I'll mention it anyway. My very limited (and probably very wrong) understanding of quantum theory tells me that until something is...

Are all the radio galaxies in the (approximarely) same distance from us? And is the reciveing frequency from all of them in radio band? I am wondering whether the difference between a radio and x-ray galaxy is their redshift or their emission mechanism ?

I believe that when we say that this is radio telescope, it means that reciving frequency of it is in radio band. And also it means an observed object by that is in a particular redshift that its emission has a particular frequency that when receives us, is in radio band. Am I right? For ex. We...

Now, we humans observe time to be absolute and always progressing into entropy. However, mathematically it really just seems like a axis which helps determine energy and entropy at points along the grid. I guess what I'm curious about is if there is a bias as to how time progresses, I mean...

I think entanglement swapping shows the difference between measurement and observation. A measurement isn't as important as observation at least to subatomic particles. Here's some key points...

I suppose a related question is in regard to the fundamental nature of quantum superposition. Does any system in superposition "necessarily" demonstrate interference on a macroscopic scale?

Are there any high resolution observations of the gravitational lensing by dark matter, good enough to determine if dark matter is clumped or spread out at small scales?

I suppose I am not the first to notice this, but if you are going at say, 0.999c you will have shrunk by a factor of about 20 and everything else on the craft. Suppose the spacecraft is 2000 meters long, at 0.999c it will shrink to about 100 meters long. So suppose a person 2 meters tall...

I thought this might be of interest: NY Times article on evidence of pop III stars. diogenesNY -------------------------- New York Times - June 17, 2015 Astronomers Report Finding Earliest Stars That Enriched Cosmos By DENNIS OVERBYEJUNE 17, 2015 Astronomers said on Wednesday that they had...

Homework Statement The intensity of the Sun's radiation is about 1380 Wm-2 at Earth's distance, 1.5x1011m. Earth absorbs this radiation as a black body, and radiates its own energy back into space. a) How much Energy per second falls on the Earth's surface? (Diameter of Earth = 12800km) b)...

So, I'm new around here and I'm not entirely sure if this is in the right section, but today I noticed something which I found thought-provoking. Before I go into this, I should point out that I'm 16, so all of my physics knowledge above high-school level is entirely self-taught, so I still have...

Hello. Probably a stupid question, but hey why not. Since Neutrino's do not interact with electromagnetic fields, but cosmic rays and other particles (that would overwhelm a neutrino signal if observed in an environment not at least partially shielded from their signals as at SNO etc) DO...

I have just started reading about a classical electromagnetic treatment of light-matter interaction (beginning with dispersion relations, and then moving on to the standard phenomena - reflection, refraction, etc.). The discussion begins with a forewarning that light is not 'continuous' as the...

Firstly, I apologise for any lack of understanding, incorrect assumptions or misinterpretations of the very little I know about physics, quantum mechanics & quantum computing. I am not an academic, scientist or mathematician, but a software engineer with an interest in quantum computing and...

Hello. If time is infinitely dilated at the edge of the EH, how do we observe accretion?

If an observer was traveling with a Lorentz factor that would make that observers time slower than someone's on Earth, what would that observer see watching a live video feed, or if it was possible to observe Earth with a telescope, and vice versa? I understand that either party would only see...

My question is a little more broad than I could make clear in the title but here goes. First of all, to be clear, am I correct in understanding that light behaves in precisely the same way as an electron in the sense that there exists a wave function which evolves according the Schrodinger...

Hi! :) This is my first message here. The reason I joined this forum is because there are some knowledgeable people here who might be able to shed some light on an observation that I cannot explain. It happened during the night of July 28, 2013, at around midnight, and it still keeps me...

Hi all, I'm not really seeing why entanglement is such a big deal, if total spin was 0 and the particles it creates can only have spin 1/2 and spin +1/2 then if one is down the other must be up, so they have spins designated at birth so to speak, what makes us think they don't have spin till...

I've been reading a lot of hype about Sonny White and his attempts to look for Alcubierre warp bubbles. If objects do in fact non-locally travel at de facto superluminal speeds, how can these objects be observed to be traveling at such speeds? Wouldn't the observer just see the light outside of...

As a writer, light is as crucial as it is to physicists. But I'm struggling with some conceptual understanding surrounding light. If you could supply any answers to this science layman I would be very grateful. 1) Without light there is no way of observing and measuring. So light is both itself...

There are various different ways to try to add up the effective total mass of a configuration of masses in GR in such a way that it comes out to be equal to the total of the source mass as measured locally minus the gravitational binding energy. One of these is for example the Komar mass, which...