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3answers
77 views

On existence of mass in different form [closed]

(I'm a mathematician actually. This is my first question on this site. So please go easy on me if it's a trivial matter or mistake) Lately I've been thinking about special relativity. The thought ...
0
votes
1answer
88 views

How can light reach its speed? [duplicate]

The mass of a photon is said to be 0, But light (photons) get attracted due to gravity of a black hole, that means photons have a mass which is very very very small. And we know that any object with ...
0
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0answers
32 views

High speed and low speed photons (hypothesis - difference/relation)

In this question I found an interesting answer with the source. Quotation: A telescope viewing a supernova from over 16 billion light years away recently clocked the low energy photon arriving 5-...
1
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6answers
131 views

Is 'photons being massless' the reason everyone observes their speed to be the same?

When a man on a train throws a ball, the resultant velocity of the ball (as seen from ground) is the sum of the velocity of the train and the velocity imparted to the ball from the throw. However, if ...
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4answers
134 views

Do photons interact or not directly?

All I am asking about is photon (EM wavepacket) photon (EM wavepacket) interaction. I have read this question: If photon-photon interactions are impossible, how are higher harmonics generated? ...
2
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3answers
145 views

Four-velocity vector of light

Please note that my question is not a duplicate, it is not about the speed of light, my question is only technical about the four velocity vector for light, its definedeness, value and constantness. ...
0
votes
1answer
70 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?
1
vote
1answer
122 views

In what sense do photons exist?

In a photon's frame of reference travel is instantaneous, so presumably a photon cannot exist in its own frame of reference. I am not aware that a "beam" of photons interacts via gravity despite ...
2
votes
2answers
112 views

Photons’ Speed (light speed) in vacuum [duplicate]

In a vacuum, are photons always traveling at 100% light speed? Can photons go any slower in a vacuum? They have no mass which means they can go at 100% light speed, but do they have to?
7
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3answers
273 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 ...
0
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0answers
68 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 ...
2
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3answers
78 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
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2answers
75 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 ...
-2
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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 ...
-2
votes
3answers
347 views

Rest mass of the photon [closed]

Why is the rest mass of the photon is taken to be zero? If rest mass of the photon is non zero, then it leads to infinite energy of the photon (by $E=mc^2$ equation) and there is a violation of ...
-1
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1answer
29 views

Cooling photons to a solid state

Can we cool photons so the stop moving completely? So they can behave like particles in a solid.
2
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2answers
88 views

How do we know that light cannot travel faster than it does?

We assume the speed of light in vacuum is its maximum speed but can we not assume that it could be faster, or slower?
17
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5answers
6k views

Do Maxwell's equations predict the speed of light exactly?

I know that $\frac{1}{\sqrt{\mu_0\varepsilon_0}}$ is equal to the speed of light but is this prediction accurate? I mean is it 100 percent accurate?
0
votes
1answer
71 views

How can individual neutrinos have different amounts of energy?

Photons have no mass, travel at the speed of light, and their energy is related to their frequency. Neutrinos have a very small mass, travel at almost the speed of light; what is their energy related ...
2
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3answers
222 views

What is the fastest possible acceleration?

Context & Question In physics, the fastest possible speed is accepted as the speed of light. No other mass has been recorded to travel as fast as the photon. What is the acceleration of the ...
2
votes
1answer
84 views

What happens to a photon's speed when it reflects?

So, we have a photon going c, as they are wont to do. The photon travels exactly 1 light year where it is reflected 180 degrees and travels the same light year back to the start (our detectors). Is ...
1
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0answers
56 views

If time stops at the speed of light, how do photons vibrate in waves [duplicate]

I understand photons travel at light speed because they have no mass therefore they travel at the fastest possible speed, and at the speed of light time stops. If time is frozen at light speed how do ...
1
vote
1answer
113 views

Relativistic mass of photon [duplicate]

What is the relativistic mass of one photon, i.e. what is $N$ here: $10^{-N}$ kg?
1
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0answers
73 views

Why can’t we accelerate photons, and is it possible for a photon to have mass? [duplicate]

So I’m doing a science project and I’m trying to understand why the photon is massless. I’ve learned that neutrinos were thought to be massless at first, but then physicists found 3 types of neutrinos ...
4
votes
5answers
1k views

If light does not change speed, how does luminous intensity decrease?

Light is made up of photons. They hit our eyes to create sensation. Suppose two points A and B are in a very long distance apart in vacuum. If we shine a very weak light from point A, practical ...
1
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3answers
140 views

Does the space collapse to a singularity, for a photon?

Using some elementary concepts, I've arrived at the apparent conclusion that all the space seen from a particle moving at the speed of light always collapses to a singularity at distance 0 from the ...
0
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3answers
100 views

Is it possible to get steady photon?

When light travels from low density medium to high density medium it's speed decreases according to refractive index of medium. And light is made of moving photons . That means photons are slow downed....
-3
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1answer
81 views

Light has Mass or not? [duplicate]

If there is no mass for the light, it should penetrate. But light is not penetrating through solid medium. If the speed of light is constant there is some work should be done to maintain the speed. ...
0
votes
1answer
65 views

Concerning the passage of light through a glass medium and it's apparent re-acceleration, is the absorption explanation supported by evidence? [duplicate]

When someone questions how light can re-accelerate after slowing down in a glass medium, the common answer is that it never really slows down, it is absorbed by the atoms and then released. Have ...
0
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0answers
69 views

Discrete structure of moving light in space-time. Does the light actually moving or it is triggered by cells of space-time? [duplicate]

I have an idea that seems for me interesting and exotic. It is not about a traveling with speed of light or observing a frozen light. Rather it is about the nature of light/photons and discrete ...
0
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1answer
39 views

Change in color

We have studied that when light changes medium, its speed along with wavelength, changes. Does that means that if we are inside a pool of water and a red flash light is pointed towards us, it will ...
1
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3answers
130 views

What is the mass of Photon or Light Particle?

We know that any particle moving at speed of light will have infinite mass. Since even Light has particles. Then what is the size of the Particle? How to imagine this with the mass of light particles....
1
vote
2answers
301 views

How can massless gluons interact with each other?

Massless particles, such as photons and gluons, move with the speed of light and consequently experience no time. According to Special Relativity, time stops at the speed of light. As a result, ...
0
votes
1answer
55 views

Light speed and red shift

D. Giovanni et al. showed that the speed of photons through space can be variable if certain structure is imposed on the photons themselves (see their arxiv submission or their published work in ...
1
vote
1answer
180 views

Can we have a photon at rest? [duplicate]

Theoretically, Photons don't have rest mass but they behave as material particles in many cases. But is it possible to stop a photon without destroying it ie. Can we slow it down so much to make it ...
3
votes
1answer
76 views

Regarding black holes and the speed of light [duplicate]

Prior to a black hole reaching sufficient (size ) to stop radiating light (due to excessive gravity ) would the speed of radiation of light slow smoothly down to zero (as the hole draws closer to the ...
1
vote
1answer
48 views

Shapiro test interstellar/intergalactic

I understand that the Shapiro time delay effect is one of the four classic solar system GR tests. I understand the EM waves have to pop back from a planet beyond the star and then pass next to the ...
-1
votes
2answers
1k views

Can a photon decay?

If supposedly someone is to argue that photon might be carrying a mass which is much smaller than our current detector can measure, and it could decay into something that moves at the speed of true ...
2
votes
2answers
71 views

Special theory of relativity - relative movement [duplicate]

If Mr. Einstein traveled at 99.99999999% speed of light in one direction and shined light backward, would the photon hang static in the air? Traveling speed of light away from its source that travels ...
-3
votes
1answer
56 views

Why does $a=v/t$ not work for light? [closed]

if acceleration = velocity/time and light takes approx. 8 minutes to reach from the sun to earth doesn't that mean light is accelerating at 37,500,000 m/s^2 ?
2
votes
0answers
66 views

Can we assume that in vacuum in an expanding universe all photons travel faster than light away from their source?

Asking this question I assume the example photons travel in vacuum. Once a source emits a photon they get separated by some space. Doesn't that space expand with the Hubble constant like the rest of ...
3
votes
4answers
342 views

Do photons slow down?

If $c$ is the 2-way speed of light and we can't measure the one way speed, how do we know with absolute certainty that photons don't loose speed after a first bounce off of a reflective surface? If we ...
-2
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1answer
278 views

Similarities between photons and neutrino? [closed]

Are there any similarities between photons and neutrino?
2
votes
3answers
102 views

Electromagnet would emit light?

Light is an Electomagnetic wave. When I create an electromagnet by passing electricity wound around a core and keep changing the electric field, does it emit photons? Is the frequency of ...
0
votes
1answer
43 views

Time Delay on Multiple Photons when travelling from one place to another

I'm trying to understand the time delay induced on each photon when several individual photons travel in an open space from a sender to a receiver for example in the application of Quantum Key ...
4
votes
2answers
195 views

Is the non-existence of a rest frame for photon in vacuum a consequence of the second postulate?

So there are multiple reasons given as to why does a photon (or any massless particle) have no rest frame (inertial, of course). I perfectly understand all the possible explanations one can give - it ...
0
votes
2answers
105 views

What will a photon say about the motion of other photon? [duplicate]

I have read that speed of light remains constant in every frame. If a frame moves with some noticeable velocity ( with respect to some other frame), Then in that frame ; time slows down, length ...
0
votes
2answers
829 views

Relativistic mass of photon in motion [duplicate]

There are two expressions regarding relativistic mass of photon; namely relativistic approach: $$m = \frac {m_0} {({1 - \frac {v^2 } {c^2 }) } ^\frac {1 } {2} }. $$ And, energy-mass equivalence ...
-1
votes
3answers
415 views

Does a photon not having a reference frame result in logical inconsistency? [duplicate]

So, I know that SR makes two statements. One is the first assumption it has: "Speed of light is the same with respect to all reference frames". Second, the statement: "A photon cannot have a ...
-1
votes
1answer
377 views

Does light really slow down when moving through a transparent medium? [duplicate]

I assume its speed doesn't change but the photons get absorbed and destructed by the materials' atoms and then they emit new photons. Is that true?