Tagged Questions
0
votes
1answer
96 views
Neutrinos and Speed of light
Einstein's Special Theory of relativity postulates that the speed of light is same for all frames.
Suppose a neutrino is there moving at the speed of light. Then will that neutrino also be flowing ...
1
vote
1answer
115 views
Why does Lorentz factor not hold for relativistic mass when we apply it to photons? [duplicate]
We know that the photon itself is massless particle $m_0=0$. But we also know, that the mass of the objects does increase with their energy. And we know that under certain circumstances (gravity, ...
3
votes
3answers
100 views
Reaching the speed of light via quantum mechanical uncertainty?
Suppose you accelerate a body to very near the speed of light $c$ where $v = c - \epsilon$. Although this would take an enormous energy, is it possible the last arbitrarily small velocity needed -- ...
4
votes
1answer
47 views
Live feed from a Rocket traveling near the speed of light?
Okay, odd question popped up in my physics class today. If a rocket ship is traveling at .99c for 1 year, and is streaming a video at 30 frames/sec to earth, how would the earth feed be affected? ...
0
votes
3answers
106 views
Stuff can't go at the speed of light - in relation to what? [duplicate]
We all know that stuff can't go faster than the speed of light - it's length becomes negative and all kinds of weird stuff happens.
However, this is in relation to what? If two objects, each moving ...
0
votes
1answer
29 views
If there's a light ray and it's turned to a new location by a certain angle
Imagine that there's a light ray, with source at point A, and it's directed towards point B (which is very far from point A) and it continues for a huge distance.
How will an observer at point B ...
0
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3answers
158 views
Is there absolute proof that an object cannot exceed the speed of light?
Have any known experiments ruled out travelling faster than the speed of light?
Or is this just a widely accepted theory?
0
votes
2answers
159 views
Has anyone ever measured the one way speed of light perpendicular to the Earth at the Earth's surface?
1 - Has anyone ever measured the one way speed of photons traveling perpendicular to the Earth at the Earth's surface?
2 - Given our current understanding of Physics is there any way both the upward ...
3
votes
2answers
75 views
How does the wavelength change in relativistic limit?
In the text, it reads that the momentum of a particle will change if it is moving at speed close to light speed. In the general case, the wavelength is given as
$$
\lambda = \frac{h}{p}
$$
and
$$p ...
7
votes
4answers
349 views
How does $E=mc^2$ put an upper limit to velocity of a body?
How does $E=mc^2$ put a upper limit to velocity of a body? I have read some articles on speed of light and they just tell me that it is the maximum velocity that can be acquired by any particle. How ...
1
vote
3answers
89 views
Special Relativity - speed of light question
Just a basic question:
I know that if you are traveling at $x$ speed the time will pass for you slower than to an observer that is relatively stopped. That's all just because a photon released at the ...
0
votes
2answers
62 views
Special Theory of relativity on electromagnetic waves
Since time slows down and length contracts, when we travel almost at speed of light, if the speed of light (or EM waves) remains same and the wavelength of light remains same, do we measure the ...
5
votes
2answers
242 views
What if a faster-than-light particle is found?
What will be the consequence (severe ones) on laws of physics if a particle that travels faster than light is discovered?
I am looking for a more general answer so that a high school student would be ...
0
votes
0answers
103 views
About the theory of relativity
Why is speed of light constant in every non inertial frame of reference? Is there any theoretical explanation behind this postulate Since we cannot completely depend upon the experimental results?
0
votes
1answer
45 views
Wavefront emitted by bodies at traveling near the velocity of light
I studied that no body can travel with the velocity of light. But, assuming that when a body moves nearly velocity of light, will it obey length contraction law of Einstein or will it emit the same ...
0
votes
1answer
44 views
How the effect travel's? [duplicate]
Let us assume that we placed lot's of ball touching each other in a hollow cylindrical tube, now if we push one ball at the end the ball at the other end move's instantly. So how do the information ...
2
votes
1answer
90 views
Angular velocity and the speed of light
So, accelerate a particle to just under the speed of light, then send it round a bend, technically it accelerates due to the change of direction, will its speed exceed or match $c$?
Keep it simple, ...
6
votes
3answers
315 views
Can something travel faster than light if it has always been travelling faster than light?
I know there are zillions of questions about faster than light travel, but please hear me out. According to special relativity, it is impossible to accelerate something to the speed of light. However, ...
-2
votes
1answer
64 views
How would time duration and space distance change when we move in the speed of light? [closed]
It is possible to figure out how time duration and space distance change when we are close to the speed of light - but I am not sure what happens to them if we travel in the speed of light.
1
vote
0answers
28 views
Why can't we accelerate to the speed of light? [duplicate]
Why can't we accelerate to the speed of light? It's just a speed and nothing else. Universe also crossed the speed of light at the time of big bang. Is this is just a interpretation or there is any ...
2
votes
1answer
113 views
Life of a photon [duplicate]
I am a student of class 12th and as far as i know when anything reaches about 99.99% of the speed of light it starts traveling in time or time for it slows down so that it don't breaks the speed ...
9
votes
3answers
342 views
How does a photon experience space and time?
To an an external observer it appears that time has stopped for photon. But this relation is reflexive, so for an observer travelling with the photon it appears the universe has stopped everywhere.
...
-2
votes
2answers
106 views
If we are travelling with the speed of light, can we see what's behind us? [closed]
If we are travelling with the speed of light, can we see whats behind us(like if we are moving away from earth can we able see the earth)? And how we see the things that we are approaching with speed ...
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0answers
27 views
Run with speed of light with a mirror in hand [duplicate]
Possible Duplicate:
Reflection At Speed of Light
Imagine you are able to run with the speed of light holding a mirror in your hand.
Now will you be able to see yourself in the mirror?
0
votes
1answer
106 views
What is the maximum time dilation between two objects, if one is standing still and the other is moving at $c$?
What is the maximum ratio in the rate of change in time in reference to object $A$ which is standing still and object $B$ which is moving at the speed of light?
0
votes
1answer
33 views
Speed of light and lorentzian factors [duplicate]
Possible Duplicate:
How can a photon have no mass and still travel at the speed of light?
If light travels at the speed of light, and anything with rest mass will experience relativistic ...
3
votes
1answer
238 views
How is the speed of light constant in all directions for all observers?
Please imagine the following thought-experiment:
Order of Events:
Pulse - A single pulse of light is emitted from the light towards the mirror
Reflect - The pulse hits the mirror and is ...
-1
votes
1answer
73 views
Speed astronauts measure moving at the speed of light
Lets suppose a spaceship travels with v = 0.9c relative to the Earth. The time inside the spaceship would pass slower than on Earth. Would the astronauts measure a different speed (that means, a ...
1
vote
6answers
253 views
What can $E=mc^2$ do?
In the famous equation $E=mc^2$, the variables stand for:
$E$ is energy, $m$ is mass, and $c$ is the speed of light (in vacuum).
And I understand the equation fairly but limited in knowing in ...
-1
votes
2answers
75 views
If airplanes' highest speed depends directly on the air it is moving through and not the ground,
If airplanes' highest speed depends directly on the air it is moving through and not the ground, does it mean we can build a time machine if only the air moves near the speed of light?
3
votes
2answers
112 views
Extended Rigid Bodies in Special Relativity
I was reading Landau & Lifhsitz's Classical Field Theory and I noticed that they mention that an extended rigid body isn't "relativistically correct".
For example, if you consider a rigid rod ...
9
votes
2answers
710 views
Is the “How to break the speed of light” minute physics video wrong?
I am referring to this video, on YouTube, by minutephysics, which has quite a lot of views.
In the video it states that if you flick your wrist while pointing a laser that reaches the moon, that the ...
9
votes
1answer
298 views
How is quantum mechanics compatible with the speed of light limit?
Consider a free electron in space. Let us suppose we measure its position to be at point A with a high degree of accuracy at time 0. If I recall my QM correctly, as time passes the wave function ...
10
votes
4answers
345 views
The definition of an inertial reference frame in Einstein's relativity
I'm reading Sean Carroll's book on general relativity, and I have a question about the definition of an inertial reference frame. In the first chapter that's dedicated to special relativity, the ...
1
vote
1answer
107 views
Photons and Relativity
Consider a Photon from Sun and travels with a velocity $c$. Now think we are that photon. For us, it looks like Sun is moving away from us with a velocity $c$. So, why don't we get attracted back ...
0
votes
1answer
196 views
Calculating the speed of an object moving relative to another moving Object (Frame of reference) [duplicate]
Possible Duplicate:
How to deduce the theorem of addition of velocities?
Let's say that you are in a rocket speeding at 90% the speed of light away from Earth. Now fire a bullet inside the ...
12
votes
2answers
279 views
What does a sphere moving close to the speed of light look like?
What shape does the viewer in a reference frame with $v=0$ perceive? I suppose that since the sphere moves in one direction only (oX only, not oY) its section would change into an ellipse, where the ...
2
votes
2answers
147 views
Is there a way to formulate relativistic dynamics in a way that “hides” the finite speed of light?
I'm not referring to the dimensional choice that makes $c=1$; rather I'm imagining something more about replacing all references that apparently involve velocities with the appropriate $\gamma$ ...
4
votes
1answer
128 views
Could we have assumed the speed of light to be different in different reference frames?
Ptolemy's model of universe assumes that our earth is the static center of universe and everything else move relative to it (ref: The grand design ch:3). This model would give us a consistent picture ...
4
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2answers
415 views
Is 2.5x speed of light possible between two objects?
These news are in Finnish:
http://www.hs.fi/ulkomaat/Kaukaisin+havaittu+galaksi+et%C3%A4%C3%A4ntyy+maasta+valoa+nopeammin/a1305618680897
The main excerpt is:
"Distant galaxy moves away from us as ...
2
votes
2answers
151 views
Is there any law that prevents an object with mass to become massless?
I got into a discussion with my physics teacher about the speed of light and I asked
What if an object with mass was to lose mass as it gained speed-- would that allow for an object to eventually ...
2
votes
2answers
199 views
Another faster-than-light question
Imagine we have something very heavy (i.e supermassive black hole) and some object that we can throw with 0.999999 speed of light (i.e proton). We are throwing our particle in the direction of hole. ...
10
votes
1answer
609 views
How realistic is the game “A slower speed of light”?
The game "A slower speed of light" from MIT claims to simulate effects of special relativity:
Visual effects of special relativity gradually become apparent to the
player, increasing the ...
1
vote
1answer
112 views
Time dilation $t'=(1-\frac{v}{c})t$ instead of $t'=\frac{1}{\gamma} t$
Suppose we have a train moving. When the origin of train's frame coincides with the origin of observers frame; the the time is set to zero. At that very instant, a photon is emitted from train towards ...
-1
votes
1answer
86 views
Faster than light due to reference position [duplicate]
Possible Duplicate:
Travelling faster than the speed of light
Please try to follow and clarify me I've been curious about this for a long time as it seems a bit paradox due to the rule that ...
15
votes
3answers
741 views
What is the length of 1 second in meters
If time is treated as a fourth dimension of spacetime, what is relation between length and time units?
Or in other words, how can I convert time units to length units, for instance seconds to meters?
...
0
votes
2answers
218 views
Is it possible to reduce speed of light? [duplicate]
Possible Duplicate:
What really cause light to appear slower in media?
This came to me as a question from one of my friend while I was convinced that the answer is NO. But I have read in ...
1
vote
2answers
306 views
Faster Than Light Communication Using Gravity?
Suppose two parties $A$ and $B$, some distance apart and at rest relative to each other both had control of one massive local object each.
If party $A$ lifted their local object upward relative to ...
2
votes
0answers
43 views
Reaching the speed of light, rockets [duplicate]
Possible Duplicate:
Double light speed
Someting almost faster than light traveling on something else almost faster than light
Well I've been wondering quite a long time about this ...
3
votes
5answers
324 views
Measure absolute speed
Currently I'm 17 years old, going to secondary school. So, my ideas might be totally wrong...
I know that everything is relative. In the example of speed, the earth moves, and the galaxy moves, etc.
...
