Questions tagged [speed-of-light]

The speed of light is a fundamental universal constant that marks the maximum speed at which energy and information can propagate. Its value is $299792458\frac{\mathrm{m}}{\mathrm{s}}$.

Filter by
Sorted by
Tagged with
0
votes
1answer
59 views

Speed of light as the maximum speed and movement course

Assuming we have 3 objects d,e,f moving on the same line while e is stationary, d is moving to the left at 'almost speed of light' and f is moving to the right at 'almost speed of light'. What is the ...
0
votes
1answer
56 views

Journey away and back at close to the speed of light $c$

If a person drives away from a clock tower at a speed close to $c$ for one whole day, and then drives back to it at the same speed (for another day), what would he see during each of the journeys? I ...
7
votes
3answers
270 views

Are photons “born” travelling at the speed of light? In what manner do they propagate through space? [closed]

When an electron jumps from a high to a lower energy level and a photon is created, can the photon be detected from all vantage points or only from a discrete position? Does the atom nucleus cast a ...
5
votes
4answers
136 views

If a photon doesn't experience time, how can it have a frequency? [duplicate]

It is said that photons, moving at c, do not experience time. But then, if a photon doesn't experience time, how can it have a frequency?
2
votes
3answers
105 views

Answering simple questions about black holes to someone not knowing GR

In the Newtonian description of a black hole, it is a gravitating astrophysical object for which the escape velocity exceeds the speed of light in vacuum ($c$). But what does this actually mean for a ...
1
vote
1answer
80 views

How does temperature affect the refractive index of a vinegar?

I’m conducting an experiment on the relationship between temperature of vinegar and its refractive index.
0
votes
0answers
61 views

Why does Alfred Schild's time dilation experiment make sense?

From my understanding, the experiment is carried out between 2 observers under different gravitational acceleration. The first one fires 2 light pulses towards the second observer with a certain time ...
-1
votes
1answer
74 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
43 views

Speed of light dependent on source velocity in other medium [duplicate]

Does speed of light depends upon the velocity of source in a medium (like water) other than space? if yes, does the speed gets added up when the light source moves in direction of light?
0
votes
2answers
75 views

Spaceship A and Spaceship B move in opposite directions at half the speed of light, and A fires a laser at B, does the laser light reach Spaceship B? [closed]

This question has been bugging me for a week now! I believe it would, but logically, I feel like I'm missing something. Please give a full explanation.
2
votes
0answers
29 views

Do condensed-matter field theories with multiple fields generically have multiple speeds of sound?

It is well known that the low-energy physics of many non-relativistic condensed matter systems can be described by field theories that display emergent Lorentz symmetry. The heuristic way to figure ...
0
votes
1answer
60 views

Light moving toward a moving observer's reference frame

The speed of light is supposed to be the same for all observers in an inertial frame, no matter the observer's speed. As a result, time slows down for observers moving quickly, and this explains why ...
1
vote
2answers
83 views

Does Michelson-Morley experiment really disprove the existence of aether?

In the MM experiment, the speed of one light beam was supposed to slow down as it moved against the flow of aether, but when it bounced off the mirror, it would be moving in the opposite direction--...
-1
votes
1answer
49 views

Dimensional grid of spatial coherence on earth of Pole Star radiation

One spot on earth receives a constant stream of stellar radiation: this is the North Pole where the Pole star radiation flows constantly. Given that a point source of light is considered to emit a ...
0
votes
0answers
64 views

Where does light get its speed from? [duplicate]

One source of light is, IIRC my high school physics, when an excited electron jumps back to its normal position. This jump generates a photon. How can an event like that shoot of a particle at the ...
-1
votes
1answer
64 views

Can light be sped up to go 30 times fast than the speed of light in a medium?

Here's the link: https://sciencebulletin.org/researchers-develop-way-to-control-speed-of-light-send-it-backward/ Here's the line that makes no sense to me: Abouraddy and study co-author Esat Kondakci ...
2
votes
1answer
49 views

When a valence electron is excited, how fast does it move from ground state to excited state?

Imagine an atom with a valence electron becomes excited and the electron moves to a higher orbital, is this transition between ground state and excited state at speed of light? If so, since it is not ...
0
votes
2answers
64 views

Explain the effects of differences in the velocities of electromagnetic waves to different substances

It's a GCSE specification point and I cannot find notes or answers on the internet. Can someone help me out?
1
vote
2answers
156 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 ...
0
votes
1answer
50 views

Difficulty in understanding the three classes of events of light-cone

Recently I'm reading Chapter 2: Space and Time of A Brief History of Time. The paragraph that follows the light cone says: Given an event P, one can divide the other events in the universe into ...
1
vote
1answer
41 views

How can the big bang be “observed”?

The Big Bang Observer is a proposed spacecraft to study gravitational waves. Especially the one that are thought to originate from the Big Bang. Question. How can we observe waves that has an origin ...
0
votes
0answers
24 views

Predictions followed from Fermat's Principle, according to Feynman

In his book Lectures on Physics, Feynman mentions two predictions followed from Fermat's Principle (chapter 26-4). 1) Given three media air (1), water (2) and glass (3) with indices measured against ...
0
votes
7answers
190 views

If the Earth is moving, then how is it possible to slow down light? [closed]

Given the following: Earth is spinning on its axis and also rotating around the sun. Light has no mass and is not affected by our moving atmosphere When we slow down light as is done here to a mere ...
0
votes
1answer
71 views

Speed of light and time dilation vs. mass and time dilation

Time slows for an observer the faster they come to the speed of light, large amounts of mass also also have an effect on time. How much mass would be needed to have the same effect on time as moving ...
23
votes
2answers
3k views

If a black hole is created from light, can this black hole then move at the speed of light?

Imagine we managed to squeeze light into a very tiny region of space so that the energy concentration at that point becomes a black hole. Can this black hole then move at the speed of light?
1
vote
1answer
93 views

What motivated Einstein's postulate on the speed of light? [closed]

I know that there are several experiments (conducted after Einstein's formulation of Special Relativity) that confirm to some extend Einstein's postulate that nothing can travel faster than light. But ...
3
votes
2answers
111 views

Is a finite lightspeed necessary for cause and effect to exist? [duplicate]

In this question I asked in somewhat unclear (unclear enough to be closed) fashion about the relationship between an infinite speed of light and the existence of cause and effect. In thís question, I ...
0
votes
0answers
79 views

How does electricity travel near the speed of light if electrons drift at a snail pace? [duplicate]

I was in a reddit argument with someone who said electrons didn't flow at the speed of light in a circuit. Then he linked the Wikipedia page for drift velocity and defeated me in one fell swoop. Now, ...
9
votes
4answers
2k views

Are cause and effect the same as in our Universe in a non-relativistic, Newtonian Universe in which the speed of light is infinite? [closed]

Suppose the Universe was non-relativistic so time and space would be independent of each other. In other words, both of them separately would be absolute and independent of an observer's motion (...
0
votes
1answer
29 views

Energy of light

If a beam of light is travelling in full vacuum in same medium ,then , the energy of the light beam will decrease or not while moving through space ? The wavelength of the beam of light will change ...
0
votes
1answer
75 views

What would the effects be on the world if light slowed down? [duplicate]

It would be really helpful if the effects were just given in a list form so I can research them. The reason why I am asking this is because I to write an essay regarding the effects of a change in a ...
20
votes
4answers
2k views

Light propagating through a sound wave

We know that the speed of light depends on the density of the medium it is travelling through. It travels faster through less dense media and slower through more dense media. When we produce sound, a ...
0
votes
0answers
56 views

It is said that an object cannot exceed the speed of light, because high speed makes the object closer to infinite mass, but speed relative to what?

That is, the speed of an object, when getting closer to speed of light, makes the mass of the object closer to infinite, but isn’t speed relative? So a man on earth feels a metal ball on the table has ...
2
votes
1answer
57 views

Will the log of wood sink in the water?

Imagine the water in a river is flowing with speed very close to the speed of light. There is a log of wood tied to any object outside the river so that it doesn't go ahead with water and is at rest ...
2
votes
3answers
74 views

How does a single photon behave propagating through glass?

Take a normal pane of window glass and a photon somewhere within the visible range. My limited understanding is that when light passes through glass one shouldn't think of little spheres travelling ...
0
votes
1answer
88 views

How is reflection of light possible at all? [duplicate]

If a photon cannot be accelerated or decelerated, how is reflecting them possible at all?
3
votes
1answer
158 views

How to derive $c=1/\sqrt{\varepsilon_0\,\mu_0}$ from integral form of Maxwell equations? [closed]

I've read similar questions and answers given thereto but find them unsatisfactory. So please don't mark my question as "duplicate". The question may as well be a duplicate, but it's still waiting for ...
-1
votes
1answer
66 views

Escape velocity of Kerr black Hole [duplicate]

Do the event horizon of Kerr black Hole have escape velocity is equal to the speed of light same Schwarzschild black hole?
1
vote
1answer
67 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 ...
0
votes
0answers
64 views

The hypotenuse of the triangle in the Michelson and Morley experiment

In Michelson and Morley experiment, light is travelling from light source to partially silvered glass plate. The plate splits an incoming beam of light, and the two resulting beams continue in ...
0
votes
1answer
23 views

Speed that a galaxy-sized newton's cradle would propagate motion

This doesn't necessarily have to be a newton's cradle, but the important point is that the length of the chain of spheres is exceptionally large (on the order of light years). Ignoring the effects of ...
2
votes
2answers
220 views

How do we get a expression for speed of light $\frac{1}{\sqrt{\mu\epsilon}}$ using Maxwell's equation? [duplicate]

I am a $12^{th}$ class student in India. I am quite new to these interesting concepts. And, I think I've learnt about electrostatics, magnetism, Maxwell's equations very thoroughly. But, my books ...
1
vote
1answer
79 views

How can someone calculate distance between Earth and Moon using a laser?

I have a book stating: When astronauts of the Apollo missions visited the moon, they placed a mirror on its surface, facing the earth. Then scientists on the earth sent a strong laser beam, which ...
-1
votes
2answers
44 views

Role of motion in experimental results

This page contains:"If you are in a closed room on a ship sailing at a constant speed and the ride is perfectly smooth...[t]here’s no physical experiment you could conduct to tell whether you’re ...
0
votes
1answer
63 views

How does every ray of light or photon can follow the same Snell's law in a very random states of matter like gases and liquids?

We know that to study refraction at the interface of two media, we use Snell's law which is $$μ=\frac{\sin(i)}{\sin(r)}$$ or $$μ=c/v$$ (for vacuum as one of the media). I know this is an ...
0
votes
2answers
74 views

Relativity and Momentum of photons

I read somewhere that as the speed of a particle approaches c, its mass tends to infinity. Light is composed of particles (photons). If that is the case, then why don't we feel an enormous weight ...
3
votes
3answers
122 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 ...
50
votes
2answers
8k views

Why didn't Lorentz conclude that no object can go faster than light?

Based on Lorentz factor $\gamma = \frac{1}{\sqrt {1-\frac{v^2}{c^2}}}$ it is easy to see $v < c$ since otherwise $\gamma$ would be either undefined or a complex number, which is non-physical. Also, ...
0
votes
2answers
90 views

What would happen if a planet's escape velocity exceeded the speed of light?

What would happen if a planet's escape velocity exceeded the speed of light? Would it also collapse into a black hole (by Heisenberg's uncertainty principle and Pauli's exclusion principle) or would ...
-2
votes
1answer
57 views

Photon speed is it the same as light speed? [closed]

The speed of light is about 186000miles per sec. however, the light is also a wave. If the photon follows the wave path, then to progress at 186000miles / sec. in a linear direction must be ...