# What is Observed: Definition and 195 Discussions

Observation is the active acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the perception and recording of data via the use of scientific instruments. The term may also refer to any data collected during the scientific activity. Observations can be qualitative, that is, only the absence or presence of a property is noted, or quantitative if a numerical value is attached to the observed phenomenon by counting or measuring.

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1. ### I Expected number of random variables that must be observed

In my opinion, answer to (a) is ## \mathbb{E} [N] = p^{-4}q^{-3} + p^{-2}q^{-1} + 2p^{-1} ## In answer to (b), XN is wrong. It should be XN=p-4q-3 - p-3 q-2- p-2 q-1 - p-1. This might be a typographical error. Is my answer to (a) correct?
2. ### I Observed Redshift from Moving Source: Deriving the Result

If a galaxy is receding from us, then the 1+redshift observed on Earth is the product ##(1+z_{pec})(1+z_{cosm})## of the doppler redshift due to the peculiar motion of the galaxy and the cosmological redshift due to the FRW metric. It makes sense if we think about some intermediate observers...
3. ### I New anomaly observed in 12C X17

there is a new paper this time on C12 [Submitted on 22 Sep 2022] New anomaly observed in 12C supports the existence and the vector character of the hypothetical X17 boson A.J. Krasznahorkay, A. Krasznahorkay, M. Begala, M. Csatlós, L. Csige, J. Gulyás, A. Krakó...
4. ### I Has the Unruh Effect ever been observed?

A recent paper (June 2021) claims to have observed the Unruh effect: https://arxiv.org/abs/1903.00043 A more recent article (with links to the papers inside it) talks about a possible way to detect it (Barbara Soda et al., April 2022), while there are still skeptics (Anatoly Svidzinsky). Here is...
5. ### B Why do subatomic particles change what they do when observed?

Why do subatomic particles change what they do when observed? Does it matter who is doing the observing? What happens if a non-sentient robot does the observing? How does that compare with a sentient human doing the observing? Thank you.
6. ### I Why is the observed local region of space flat?

Hi, Also, I read this article, What Do You Mean, The Universe Is Flat? (Part I), on Scientific American; URL: https://blogs.scientificamerican.com/degrees-of-freedom/httpblogsscientificamericancomdegrees-of-freedom20110725what-do-you-mean-the-universe-is-flat-part-i/ I have few questions about...
7. ### I Majorana zero modes observed by Microsoft?

https://arxiv.org/abs/2207.02472 InAs-Al Hybrid Devices Passing the Topological Gap Protocol "We present measurements and simulations of semiconductor-superconductor heterostructure devices that are consistent with the observation of topological superconductivity and Majorana zero modes."...
8. ### I Has photoproduction of gluons been observed?

I am wondering if a process with an initial state of two photons leading to an end state with two (or more) gluons has been observed. I have seen some papers (like this one) that seem to suggest that this is the case, but none of them say so as clearly as I would like to be confident that this...

10. ### Angle observed in rest frame related to relativity

My answer is (A) since I think the motion of the spacecraft will alter the length of the spacecraft (length contraction) but not changing the orientation so the angle will stay the same But my teacher said my answer is wrong. What is my mistake? Thanks
11. ### I How well do cosmological models explain the observed µ vs. z data?

The following figure shows observed distance modulus (µ) vs. redshift (z) data (references of data sources are available): How well do cosmological models, such as ΛCDM and models based on non-expanding universe, explain these observed data? For explanation of terms, please see, Type Ia...
12. ### Doppler question - find the observed frequency

So first I calculate the final velocity by multiplying the time by the acceleration, 9.8, to get 88.2 m/s. Now I use the equation. (343/(343-(-88.2))*108.3 = 86.1477. But the answer should be 88.47. What am I doing wrong here?
13. ### B Question about "our observed universe"

I feel a bit troubled by the use of "our observed universe" as a concept of reason concerning the nature of universe. For example, the following is part of the answer of Halc to my previous question: [ Rotation around an attractor only works given the causal reach of the mass, so nothing outside...
14. ### I How Does a CMB Photon Travel Through Expanding Universe?

Suppose we receive a cosmic microwave background (CMB) photon from space. According to the Big Bang model, this photon became free to travel when the universe was about 0.38 million years (Myr) old. At that time, it was about 42 million light years (Mly) away from our location. Because of the...
15. ### I Does the wave function spread more quickly after it is observed?

For the sake of this question, I am primarily concerned with the position wave function. So, from my understanding, the wave function seems to 'collapse' to a few states apon measurement. We know this because, if the same particle is measured again shortly after this, it will generally remain in...
16. ### I Can Einstein-Chwolson rings be observed from a telescope on Earth?

There may be too much absorption and distortion by the atmosphere of the faint images when viewed from Earth.
17. ### B Has there ever been a planet-planet eclipse (i.e., observed from Earth)?

The upcoming conjunction of Jupiter & Saturn has got me thinking. I wonder if it has ever been observed (and hopefully photographed) of one planet's disc even partially taking over another's. I have seen a photo of Saturn doing this with the Moon, but I don't think I've ever seen one of a pair...
18. ### I Have we observed asymptotically free quarks?

At high energies, quarks behave like single particles, due to the asymptotic freedom in QCD. Have we observed these free quarks yet in experiment? Does the freedom energy match the theoretical models?
19. ### I What stars were observed @ 1919 solar eclipse to prove relativity?

Was there a published report of exactly which stars which were supposed to be at position A but were observed at position B, etc.?
20. ### B Understanding the Age of Observed Light: A Scientific Perspective

Not to get off subject but, when I gaze at the Triangulum Galaxy how “Old” is the light I’m observing?
21. ### B How does the observed version of the double slit get by without math?

Send a classical particle into a three dimensional potential well. 0 Probability of it tunneling. It's a classical trajectory with wobble from uncertainty. It's not a wave, but gets wobble from the quantum field influencing it. https://farside.ph.utexas.edu/teaching/315/Waveshtml/node95.html...
22. ### I Things that can be observed in a snapshot view of the universe

If we took a snapshot of the entire universe (or if we stopped time) but still had the power to move around and measure, we could observe static properties such as: Mass Force Position From the above, we would be able to infer acceleration. But we couldn't observe present velocity and...
23. ### What is the observed wavelength of the Hα line?

Homework Statement A star moves away from us at a speed of 10 km / s. the angle between the speed direction and the line of sight are 30 °. What is the observed wavelength of the Hα line? Then we suppose the observer is also moving at a speed of 20 km / away from the star. What is the observed...
24. ### B Ratio between the sizes of the Observed and the Entire Universe

Hello. I have some questions regarding Alan Guth's book on the Inflationary Universe. The following, from pages 185 & 186, has piqued my interest. I have reproduced Figure 10.6, above. Please read on. My questions follow. Please also take note that I can only understand these matters at a...
25. ### I Doppler like effect affecting observed time for a moving object

This is only something I’ve noticed, and in my eyes it’s odd, it may be utterly wrong or already well known but with some fancy term that I don’t know. Suppose an object- say, a clock- is moving towards you, at about .5c. For the moment, we will assume time dilation is negligible, and that you...
26. ### Vibration testing on shaker - High amplitude observed

Hello everyone, I wanted to gather opinion from anyone experienced in vibration regarding one of test fixtures I have created for small satellites. The image below shows the Test-POD that I am testing on a single axis shaker. In one of the tests, I had troubles that the amplitude got higher than...
27. ### B Does light only behave like a particle when observed?

My question is - is all light a wave until observed, then wave function collapses and behaves as a particle? This is far fetched (and i don't subscribe to it!), but theoretically could light from a distant object passing through a double slit experiment and exhibiting a particle pattern be...
28. ### I Can an observed atom collapse back into a wave?

I don't really know where my brain is taking me on this one. I was wondering a couple things.. You set up everything for a Slit Experiment. You shoot an atom and observed it before the slit, then somehow collected the particle. It loops back and shoots it out again, this time with the particle...
29. ### Observed battery set discharge unbalance

I previously posted the below as a footnote on one my posts on the Mechanical Engineering Forum and it was suggested I start this thread on the subject here. "PS On a general note about battery replacements. On my field GPS I use rechargeable batteries and always test them before recharging...
30. ### I Can the Christoffel connection be observed?

[Moderator's note: Spun off from a previous thread about Maxwell's Equations and QFT.] Perhaps, but Christoffel connection is also an observable. You feel it in your whole body when you accelerate. One usually calls it the inertial force.
31. ### I Fringes observed between the fingers

In Feynman lectures on physics 26 Optics 5 --- Then put two fingers in front of one eye, so as to look through the crack, and squeeze the light to zero very gently. ... Also you will notice, if you are very careful, side maxima, a lot of fringes along the edges too. Furthermore, the whole thing...
32. ### B Subatomic particles and the observer

I have read that when an electron is observed, it behaves differently to when it is not being observed. Could someone please expand on this, or indeed correct me. In what way does an observed particle behave differently to a particle that isn't being observed by somebody's consciousness?
33. ### B What happens to things that aren't ever observed?

I'm relatively new to Quantum Mechanics (QM), so please correct me if I'm wrong at any point. As I currently understand QM, everything exists as a non-tangible wave consisting of all possible outcomes until observation forces that wave to collapse into a single outcome, which becomes real. Is...
34. T

### Which harmonics would be observed on an electric guitar?

Homework Statement The electric guitar radiates very little sound directly, but instead relies upon pick-ups (transducers) placed beneath the strings. Establish, showing clearly how you reach your answer, which harmonics of the open string you are likely to observe if the pick-ups are placed...
35. ### I GW170608 - Another Binary Black Hole Merger Observed

On November 15, 2017, LIGO Scientific Collaboration announced the observation of another binary black hole coalescence. The gravitational waves were observed by the twin LIGO detectors on June 8, 2017. This is the lightest black hole binary observed so far, with component masses 12 and 7 times...
36. I

### Colors Observed in Photoelastic Media

When a photoelastic material experiences stress, its internal structure changes such that a position-dependent birefringence occurs. This means that the material effectively becomes a wave-plate, changing the polarization of incident light. It has long been known that when placed between two...
37. ### I Can quantum superpositions be observed

I heard about something called interaction free measurement which allows us to measure a quantum system without disturbing it. Now I am wondering if this can allow us to observe how an object is like in a superposition because no interaction means no wavefunction collapse...
38. L

### Is External Influence the True Source of Human Actions?

The inventor Tesla stated that all living things' actions appear to come from the will but actually come from the outside. He stated to the effect "we are corks upon the sea". For example you are sitting at your computer and start typing. You don't start typing because you want to but because...
39. ### B Double-slit experiment observed by split brain

Hello all, Does anybody here know whether the double-slit experiment has been conducted with a split brain patient as observer?
40. ### B What is the smallest particle which can be visually observed

What is the smallest particle which can be visually observed with a microscope?
41. ### The observed wavelengths of the hydrogen spectrum

can be calculated using the following formula: 1/ λ = R (1/n2f - 1/n2i) Where nf and ni are integers that can have values nf = 1, 2, 3, . . . , ∞ and ni = nf + 1, nf + 2, nf + 3, . . . , ∞. Which of the following sets of integers give the wavelength of a line in the Balmer series? (Note: more...
42. ### Chi-square goodness of fit cannot find expected values

Homework Statement An article in Business Week reports profits and losses of firms by industry. A random sample of 100 firms is selected, and for each firm in the sample, we record whether the company made money or lost money, and whether or not the firm is a service company. The data are...
43. ### Probability observed value not in range for prediction

Homework Statement Hello all, I created a predictive model from a data set of observed values and am looking for probabilities for accuracy. Data set A (observed) and data set B (predictive model) have a correlation of 84 % using linear regression. Data set A and B are both normally...
44. ### I Equations for observed distance/velocity in SR

Hello everyone. I've just recently found this forum and it has been a lot of fun browsing around. I've recently taken a stronger interest in the topics of relativity in physics and have recently developed a much better understanding of SR (and somewhat of GR) than I'd had previously and its been...
45. ### I Does this explain the Zeno effect observed

Quantum zeno effect states that an unstable particle can be prevented from decaying by being observed/measured. It has been experimentally proven. However, this observation/measurement does not refer to simply looking at it. This effect vanishes as we zoom out to the macroscopic world. Hence, a...
46. ### Time Dilation - measured vs observed time interval

Homework Statement Consider an observer Bob in S standing close beside the x-axis as Alice, who is holding a clock, approaches him at speed VS'S along the axis. As Alice and her clock move from position A to B, Alice’s clock will measure a (proper) time interval ∆t0, but as measured by Bob’s...
47. ### Observed speed of pitch different than catcher's view?

I was reading Walter Isaacson's biography of Einstein recently, and I thought of moving walkways in airports. Let's say we have a pitcher and a catcher on the moving walkway 80 feet apart, and the pitcher throws the ball to the catcher, and the time that it takes to travel from the pitcher to...
48. ### B What is the least likely event that has been observed?

I don't know if this is the best forum for my question, hopefully this is not just a lead balloon question. I expect that the statistically least likely events to ever be observed have been observed in a particle accelerator. Does anyone have any idea what takes the award for the statistically...
49. ### I Does observed light travel faster or slower than unobserved?

I realize that unobserved light it going to be difficult to measure, but could the double slit experiment be set up to give us an average air time for the particles? I find it hard to believe that a particle acting as a wave would travel at exactly the same speed as an observed one.
50. ### What is V of the small rocket as observed from inside it?

Homework Statement If the total relativistic velocity of small rocket is 0.75c after being launched from a larger rocket traveling at 0.60c, what is the velocity of the smaller rocket as observed from inside it? Can someone put this in layman's for me please. I solved many relativistic...