New answers tagged inertial-frames
2
votes
Accepted
How to show only direction is changed in collision between unequal atoms?
It comes from including conservation of energy.
Let's work in the centre of momentum frame where we have:
$$ m_1 v_1 + m_2 v_2 = 0 $$
so:
$$ v_2 = -\frac{m_1}{m_2} v_1 $$
Then the initial total ...
0
votes
What is the meaning of universal speed limit?
Consider two objects with mass: A baseball and a train.
A train has more mass than the baseball. So it is harder to move the train than the baseball. It requires more power to move the train.
When an ...
1
vote
What is the meaning of universal speed limit?
Causality ensures that cause precedes effect, so any event can't influence others outside its future light cone. The speed of light is the universal speed limit, as dictated by special relativity, ...
1
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What is the meaning of universal speed limit?
According to the postulate of special relativity (and to the many confirming experiments) light speed $c$ does not depend on the relative speed of a moving source or the detector. Hence, no matter how ...
6
votes
What is the meaning of universal speed limit?
Does exceeding the speed of light mean exceeding the speed of light
relative to all other objects in the Universe?
I think a better statement is exceeding the speed of light means exceeding the speed ...
11
votes
What is the meaning of universal speed limit?
Fun fact: Suppose that astronaut Allen has a laser mounted to his spacecraft that sends pulses of light off toward infinity. Allen performs an experiment proving that the pulses travel at speed, C. ...
15
votes
What is the meaning of universal speed limit?
It means the following: suppose the object has a good clock and a light that can flash in all directions (and for simplicity assume everything is transparent to this light). At $t=t_0$ on the object’s ...
0
votes
Is conservation of momentum and energy valid for non-inertial frames?
Balance of momentum and energy (and also angular momentum) is valid in any frame and any coordinate system. It's important here to make a distinction between a balance law and a conservation law.
For ...
1
vote
Is Schwarzschild spacetime in Eddington-Finklestein coordinates flat at Schwarzschild radius?
weeab00 wrote: "Is the spacetime really flat to an observer hovering around Schwarzschild radius?"
Locally the spacetime is flat at every r except r=0, but the local patch becomes smaller ...
3
votes
Is Schwarzschild spacetime in Eddington-Finklestein coordinates flat at Schwarzschild radius?
Choice of coordinates does not change the nature of the spacetime around a black hole.
Spacetime always looks flat locally. How locally such an approximation will work depends on the second ...
2
votes
How do different observers decide if they are looking at the same thing?
I think a way to visualize this is if you imagine that the ball suddenly popped into existence at time $t$ and position $x$ for observer $A$. Then observer $A'$ would see the ball pop into existence ...
6
votes
How do different observers decide if they are looking at the same thing?
I see a leaf fall from a tree. You see a leaf fall from a tree. We want to know whether we both saw the same leaf fall from the same tree.
Here's how we can tell: I use my meter sticks and clocks ...
10
votes
Accepted
How do different observers decide if they are looking at the same thing?
Many presentations of relativity start with this business of reference frames and observers. Those concepts are useful, but before invoking them, first get thoroughly fixed in your mind that there is ...
3
votes
How do different observers decide if they are looking at the same thing?
Coordinates, like $x$ or $x’$ are not physical quantities. They are convenient mathematical labels that we define.
Specifically they are labels that label real physical events with quadruples of ...
6
votes
How do different observers decide if they are looking at the same thing?
What you ask is not so much a special relativity thing as it is a metrology thing. How do you set up an experiment such that you can measure what you seek to measure.
If you are trying to confirm ...
9
votes
How do different observers decide if they are looking at the same thing?
You are over-thinking it. An event is a position in spacetime, so in any given frame it has three spatial coordinates and a time coordinate. Consider the event of me typing the letter Q in this ...
0
votes
Order of events is invariant in timelike intervals
You have set this problem up in the most confusing way possible. It's best to address these things systematically, with actual events using coordinates, not just ambiguous sentences.
Now we have 3 ...
1
vote
Accepted
Order of events is invariant in timelike intervals
Eric's comment is correct. If two spatially separated events are simultaneous in some frame, then they must be space like separated, so their order can be reversed in other frames. If they were time ...
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Related Tags
inertial-frames × 2745special-relativity × 1892
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observers × 542
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spacetime × 298
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