Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [observers]

The tag has no usage guidance.

-2
votes
0answers
78 views

How does one's view of the universe change as one approaches the speed of light?

I found an interesting and fun question at worldbuilding.stackexchange.com , that to my surprise, I don't find that easy to answer. I would like to quote here that question , but with a small ...
-1
votes
0answers
22 views

The effect of the Eye on the double-slit experiment

I have a simple question and I would like you to think "outside of the box" about it and post a answer. Question: Can it be possible for an "Observer" to alter matter, not by the use of the mind/...
0
votes
1answer
44 views

Minkowski diagram

I have not well understood the picture of geogebra regarding the angle of time (t') that is inclined compared to (t) of 26.57°angle . In the picture we see that the velocity is setted at 0.5c, for ...
2
votes
2answers
66 views

Can a black hole event horizon form before the singularity for an outside observer?

This is not a duplicate, my question is not about whether BHs have or don't have a singularity, but my question is whether, because of time dilation, no matter has reached the center and formed a ...
0
votes
0answers
17 views

Rindler observers are at rest with respect to each other?

I'm studying a chapter about Rindler coordinates right now. In this they say that two Rindler observers at $x = 1/a_1$ and $x= 1/a_2$ will both have speed $v =0$ at $\tau = 0$ compared to the inertial ...
0
votes
1answer
62 views

Would an observer going faster than the speed of light in a vacuum be able to observe photons that they emit? [closed]

If I could exceed the speed of light in a vacuum, would I be able to see photons that I previously emitted? Would this be theoretically possible?
0
votes
1answer
133 views

Why does time slow down ONLY for objects travelling at high speeds?

Today in physics class, we learned about the theory of relativity and how it relates to time dilation. We were given the example of two photon clocks- one stationary relative to the Earth, and the ...
0
votes
1answer
62 views

How do we know who is moving? [duplicate]

If I am in a free float environment and there is another object at rest relative to me, and then I start to accelerate towards this object, do I know I am the one who is moving, since I am the one who ...
-1
votes
1answer
73 views

Thought experiment: if an observer can travel at the speed of light [closed]

What would the observer see if he could travel at the speed of light and shot a photon beam at the same time?
0
votes
1answer
71 views

In QM does the observer really perturb the system to make a measurement?

It is commonly taught in introductory QM courses that in order to get to know the position or momentum of a particle, be it by "sending a photon" or similar experiments, the measurement necessarily ...
1
vote
1answer
169 views

Is the M87 black hole really a black hole? [duplicate]

I apologize if this is a silly question, but... From what I've been told, new black holes cannot form, because time slows to nearly stopped as matter approaches the event horizon. Instead, a new ...
1
vote
2answers
142 views

Problem with speed of light

I constructed a thought experiment, can't figure the answer. Two long (say $1\ \rm{km}$ long) railway cars are on parallel east-west tracks in a zero gravity environment. Each car has a light source ...
5
votes
2answers
314 views

Definition of observer and time measured by different observers in general relativity

An observer in general relativity is defined as a future directed timelike worldline \begin{align*} \gamma:I \subset \mathbb R &\to M \\ \lambda &\mapsto \gamma(\lambda) \end{align*} together ...
0
votes
1answer
71 views

The ladder paradox - with equal lengths

Take the usual ladder paradox in special relativity, but this time the ladder and the barn have the same length, at rest. Since each one of them contracts when viewed in the rest frame of the other, I ...
2
votes
1answer
34 views

What would an external observer see happen to objects entering an evaporating black hole?

As I understand it, objects passing the event horizon of a black hole from their perspective will, from an external perspective, seem to keep approaching but never reach the event horizon. Given this, ...
0
votes
2answers
46 views

Is Einstein's train-lightening thought experiment consistent with Special Relativity? [closed]

Einstein’s train-lightening thought experiment contains only inertial motion so SR says we can ascribe relative motion and relative rest to either reference frame. Although it is not stated in the ...
0
votes
0answers
21 views

What creates the physical difference in ageing when travelling close to the speed of light? [duplicate]

I probably have a fundamental misunderstanding, so correct me if I'm wrong. When travelling close to the speed of light, movers experience time dilation, which is what results in the phenomenon of ...
2
votes
4answers
150 views

Communication near a black hole

One ship is in a stable orbit outside of the event horizon of a very large black hole so that there is significant time dilation. Another ship is in its own orbit around the same black hole, but at a ...
1
vote
2answers
99 views

Relativity Confusion

In the time dilation formula $\Delta t=\gamma\Delta t_0$, I am confused about what $\Delta t$ and $\Delta t_0$ measure. If we have two people, Tom and Bob, moving at constant velocity relative to ...
1
vote
1answer
66 views

Recordings of journey traveling near speed of light

If you had two identical video cameras and started recording synchronized atomic clocks recording at the same speed and you put one on the spaceship and sent it out traveling at 99% of the speed of ...
3
votes
4answers
106 views

Present vs Past in Cosmological time

My question is in regard to “seeing back in time” when observing objects in space. I understand the concept that light takes a certain amount of time to reach the earth and we can determine the ...
1
vote
1answer
44 views

Train and lightning bolts: why the time difference does not depend on the position of the moving person?

So imagine two lightning bolts hit the ground, simultaneously to a stationary observer. There is also a person on a train traveling to the right at a constant velocity. I know that if he started in ...
39
votes
4answers
9k views

Is there a frame of reference in which I was born before I was conceived?

I'm struggling to understand the relativity of simultaneity and position. If my conception and birth are separated by time but not space, a frame of reference in which my birth and conception are ...
1
vote
1answer
51 views

Why do external observers see LIGO results if an object falling into a black hole never reaches the event horizon? [duplicate]

If I throw a clock towards a black hole, its time slows down, it is redshifted, and according to many theories it never reaches the event horizon from my point of view. How is it then, that a star can ...
0
votes
2answers
79 views

Would a human age faster if these certain conditions are met?

So, a human would travel in a rocket in outer space. There is little to no gravity, and the pressure may or may not have an affect (?) on what i'm about to ask. It has been proven that when a human ...
0
votes
1answer
78 views

Do gravitational waves affect the flow rate of time?

Since LIGO has been able to detect the presence of gravitational waves, this implies that there is a density wave traveling through space with a high potential front and a low potential back side. ...
0
votes
0answers
68 views

Does absolute motion/stillness exist?

I am not a physicist :) I (think I) understand the idea that motion can be relative in the sense that, I'm standing still inside a moving train in regards to the moving train itself, but I'm moving ...
0
votes
0answers
21 views

What is the definition of coordinates of an observer? [duplicate]

I am confused about coordinates of an observer. Suppose we have an observer $A$ whose world line $\gamma$ is a geodesic and another observer whose world-line $\gamma$ is not. Since coordinates is just ...
3
votes
3answers
117 views

What exactly does the observer's coordinate system mean in special relativity?

This seems like a very basic question but I'm having a hard time understanding it, more precisely hard time visualizing it. Let say there is an observer, and we wish to somewhat formalize his ...
2
votes
0answers
50 views

How are the predictions of the Schwarzschild solution consistent with our observations of black holes? [duplicate]

I am fully aware that there may be many misunderstandings in the following. However, in recent lectures we covered the Schwarzschild solution, and after some interesting mathematics we reached ...
0
votes
5answers
192 views

Is Relativity of simultaneity just a flaw in perception?

So I went through a couple of different books on special relativity ( including Einstein's own book) and I just can't seem to accept relativity of simultaneity as a real thing. I'll explain my ...
0
votes
1answer
53 views

Do Events Conditional to Simultaneity Occur in Every Reference Frame?

Imagine a train with a table that contains a light on both ends (so that the line between the two sources of light is parallel with the line of motion of the train) and a light sensor in the perfect ...
1
vote
1answer
87 views

Einstein's Simultaneous Lighning and the Lorentz Transformation

I am reading Einstein's book, "Relativity: the Special and General Theory" translated by Robert W. Lawson, and I have some questions concerning Special Relativity -- specifically, the thought ...
1
vote
1answer
48 views

Biological aging interval equals Proper Time interval?

In special relativity does proper time interval equal biological aging interval in every inertial reference frame?
1
vote
3answers
74 views

Method to observe clocks on spaceships moving near $c$?

I have read the explanation for clocks slowing down on a spaceship moving relative to a stationary observer -- something like a beam of light between two mirrors taking longer for the observer to ...
-2
votes
2answers
66 views

Relativity from a basic assumption

Is it possible to derive Lorentz transformations just by assuming that if two spaceships are moving away from each other with a constant speed, it is impossible for them to tell who is moving, even if ...
0
votes
0answers
37 views

Equivalence in all inertial frames

Suppose there is a train moving to the right. and inside the train there is an observer, A. Outside the track, there is another observer B. When the train passes in front of B, right at the instant ...
0
votes
0answers
72 views

Is there any change in temperature due to special relativity? [duplicate]

Say I am travelling in a spaceship very close to the speed of light. Would there be any change in temperature in the spaceship relative to outside the spaceship? Please explain in detail.
2
votes
2answers
87 views

Is there a connection between the energy distribution and time dilation?

Can anyone please help me understand what is descibed bellow? Scenario 1. We have a pair of atomic clocks. Let's call them clock A and clock B. We switch both of them on at the same time. Clock A ...
1
vote
1answer
55 views

How do we observe an electron? [duplicate]

When an electron is observed it acts like a particle and its wave function collapse. This statement is very famous in quantum mechanics, but what is meant by observing an electron? Which devices are ...
1
vote
0answers
52 views

Apparent FTL speeds seen by observer

MY guestion is if I was in a ship orbiting a black hole (not very close to the event horizon) I am orbiting pretty far and I am experiencing that my time is slowing down realitive to people on earth. ...
35
votes
14answers
8k views

How could quantum effects occur in the early universe without an observer?

In inflationary cosmology, primordial quantum fluctuations in the process of inflation are considered responsible for the asymmetry and lumpiness of the universe that was shaped. However, according to ...
1
vote
2answers
99 views

Double slit experiment record but not look at it

I am having a tough tough stressful week trying to write an article about quantum mechanics. I know there was a question asked the same thing before, but I didn't understand nor I did not want to wake ...
-2
votes
1answer
76 views

How can I go and also not go faster than light?

Suppose I am in a spaceship. In this spaceship there is also my friend. So my friend and my relative velocity is zero. So no matter how fast my ship goes my friend's velocity relative to me is zero($0$...
0
votes
2answers
100 views

Clock in a sealed box at half the speed of light. How would it know it is moving?

Consider a clock enclosed in a sealed box here on earth syncronized with my wrist watch. I send the boxed clock around the galaxy a couple of times at half the speed of light (or the full speed of ...
23
votes
5answers
3k views

What is physically different about a moving vs still object in space?

If I have two asteroids. One dead still in space and one whizzing by at 10,000mph. What is the difference between the two, physically? If I freeze time and look at the two of them - what differences ...
0
votes
1answer
42 views

Interdependence of time, the speed of light and distance in General Relativity

In the relation $$ \text{time}\cdot\text{speed of light} = \text{distance}\,,$$ by definition, the speed of light is constant. When bringing a clock, like in a GPS satellite, up into orbit, i.e. ...
2
votes
1answer
125 views

Proper time vs time

I'm reading about relativity and I thought I understood things clearly about proper time / coordinates until I read the analysis of the Doppler effect. A and B are 2 fixed points, there is a clock in ...
1
vote
4answers
117 views

How do we determine who is the “observer” when calculating time dilation? [duplicate]

I was reading about time dilation and I thought of a question. I really think that I am just misunderstanding something, so please bare with the question. But, I would appreciate if somebody could ...
3
votes
1answer
45 views

Bekenstein Bound and frame of reference

According to Wikipedia, this is the formula for the Bekenstein bound $$ S \le \frac{2\pi k RE}{\hbar c}$$ where $E$ is the total mass-energy. That seems to imply that the presence of a black hole in ...