Episode #125 of the Stack Overflow podcast is here. We talk Tilde Club and mechanical keyboards. Listen now

# Questions tagged [observers]

The tag has no usage guidance.

70 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
132 views

### Role of the observer in Gödel's universe

I am here to clarify myself about the role of the observer in Gödel's solution (1949) of Einstein's field equations. The Universe we are dealing with is anisotropic, since the axis of rotation ...
559 views

### What happens to objects sucked into a black hole after the black hole evaporates away?

Suppose an object falls into a black hole that's so massive that it wouldn't get torn apart at the event horizon. What happens to it after the black hole evaporates away? According to the theory ...
126 views

### In special relativity, is there a prescription to find the coordinate transformation to a general (for instance accelerated) observer? And in GR?

Suppose we are in an inertial frame, so that the metric in our coordinates is just the Minkowski metric, \begin{align} \text{d}s^2 = -\text{d}t^2 + \text{d}x^2 + \text{d}y^2 + \text{d}z^2. \end{align} ...
118 views

### Does the relative speed of time mean there is less energy where time is slower?

Time runs relatively slower near a planet than in outer space. Does this mean that there is less energy near the planet? Is there a relationship between energy and the speed of time? If so, this ...
92 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 ...
100 views

### Could you actually see the event horizon of a Black Hole?

For years I thought to myself that surely you'd be able to see the event horizon of a Black Hole when looking at it against the surrounding light. I thought that it would be similar to this: Where ...
60 views

### Centre of mass in General Relativity

In the paper from Costa 2014, Figure 1, it discusses how the velocity of an observer influences where the center of mass of a spinning object is measured. If an observer is moving with velocity $v$ ...
54 views

### Gravitational time dilation and the pace of time

If we are in empty space far from a black hole, at rest relative to the hole, we would look at a clock and a light source inside the gravitational field of the hole, then we would, according to the ...
193 views

### Does an object travelling at speeds approaching $c$ observe an increase in the expansion rate of the universe?

According to the theory of special relativity as an object approaches light speed it experiences length contraction. This means that the distance it observes between it and it's destination reduces as ...
312 views

### Observers in (Schwarzschild-) de Sitter spacetime

In (pure) de Sitter spacetime, the cosmological horizon is said to be ‘observer dependent’. I imagine that as the observer always being in the center of that horizon. Another (spacelike separated) ...
239 views

### Clarification of proper time and inertial frame of reference

“Standing beside railroad tracks, we are suddenly startled by a relativistic boxcar traveling past us as shown in the figure. Inside, a well-equipped hobo fires a laser pulse from the front of the ...
119 views

### Operational Definition of Reference Frame in General Relativity

Most treatments of GR begin with the assumption that spacetime is a pseudo-Riemannian manifold (or, sometimes, that it is a more general manifold). But this entails quite a few tacit assumptions about ...
350 views

### Does a complete theory of quantum gravity require anthropic post-selection?

Does a complete theory of quantum gravity require anthropic post-selection? Certainly the black hole complimentarity and causal patch conjectures highlights the essential role of observers, at least ...
24 views

### Curved space relative motion

Suppose I live in a 2d curved space. I can describe intrinsically the motion of a particle which moves in my 2d manifold using time "t" as a parameter. Now suppose there is a second observer (let's ...
72 views

### Reference systems in Special and General Relativity

I am enthralled by the notion of placing observers along with standard identical clocks in a line spaced from one another according to rods of standard length when place next to one another at the ...
82 views

### Why can't we take space as universal frame of reference?

Suppose we have a ball filled half with water in space with nothing else around (nothing else in the whole space except the ball) and suddenly it accelerates for time t. obviously, there would be ...
105 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 ...
59 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. ...
48 views

### Entropy and observers

Struggling to understand the stance Bousso takes in his paper, The Entropic Landscape, https://arxiv.org/abs/1001.1155 Is he saying that because only by observing an increase in available state we ...
236 views

### Why is the double slit experiment highly regarded as mysterious?

I read in Wikipedia: The need for the "observer" to be conscious has been rejected by mainstream science as a misconception rooted in a poor understanding of the quantum wave function ψ and the ...
89 views

46 views

### Is there an observer dependent temperature everywhere in spacetime?

A temperature $T=\dfrac{\hbar a}{2\pi c k_B}$ is associated to an uniformly accelerated observer. He feels this temperature all along his trajectory. The inertial observer will not assign this ...
We know the the speed of light/c is the same to all observers. But i cant grasp something. Observer is moving at $0.5c$ in relation to us. He doenst have any point of referece and everything around ...