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 $299792458\frac{\mathrm{m}}{\mathrm{s}}$.
2,937 questions
0 votes
0 answers
50 views
Why is it said that in the distant future, all objects outside the local group will be forever out of our reach? [duplicate]
I've heard this statement from a few sources and the reasoning given is something the lones of that the expansion of the universe would have made objects too far and red shifted to observe, and reach. ...
8 votes
3 answers
1k views
Which wins the race, the neutrino or the photon? [closed]
You have an emitter at A and a reciever at B. Exactly half way between them is a star. The emitter simultaneously emits a burst of photons as well as a burst of moderatly high-energy neutrinos. The ...
- 3,645
11 votes
1 answer
2k views
Why doesn't the light slow down, even if it loses energy? [duplicate]
The speed of light is roughly 3*$10^{8}$ m/s. Why doesn't the speed change when it bounces off a mirror or gets absorbed by an electron? If you throw a ball in outer space, and it hits a wall, the ...
-1 votes
3 answers
184 views
Is it possible to explain how electromagnetic waves propagate through a vacuum solely using classical physics? [closed]
I'm struggling to understand how electromagnetic waves are able to sustain through a vacuum without thinking of them as photons instead of waves. Am I right in thinking of the situation as the wave ...
- 191
6 votes
3 answers
1k views
Does General Relativity allow sudden gravitational source changes?
When I was taught General Relativity as a student, many years ago, I was told that there was no way to create a gravitational "surprise", where the source strength of some system changed ...
0 votes
5 answers
250 views
Why does light travel at 45 degrees in spacetime diagrams?
When trying to visualize the movement of matter in Relativity a spacetime diagram is often used, where in one or two spatial axes are removed and an axis added in for time. The standard way to ...
- 101
1 vote
1 answer
91 views
Is it correct that you can change light's velocity but not its speed? [closed]
A laser is shone down the center of a vacuum corridor 1 light-year in length. The corridor has a lateral motion (perpendicular to the laser) of 10mph. Does the light hit the center of the far end, or ...
2 votes
2 answers
150 views
What is gravity near speed of light due to contraction?
observing a box traveling close to $c$ i would see the box shrink in the direction of travel. so the mass in the front approaches the mass of the back getting arbitrarily close as the box approaches $...
-1 votes
2 answers
163 views
Why does the Lorentz transformation preserve the speed of light specifically under the Minkowski metric but not under alternative quadratic forms?
I know that Lorentz transformations are defined as the linear transformations preserving the Minkowski metric $s^2 = c^2t^2 - x^2 - y^2 - z^2$. But suppose we consider an alternate metric $s^{′2} = c^...
- 903
3 votes
1 answer
95 views
What is velocity of light in Schwarzschild metric at distance $𝑟$ for observer that is infinitely far away?
This is a generalization of the question which more specifically asks for radial and tangential velocity only. Given a point at distance $r>r_s$ from a mass ($r_s$ the Schwarzschild radius), what ...
- 803
1 vote
1 answer
92 views
Relation between inductance and capacitance to the speed of light in a medium
The book CMOS VLSI Design, fourth edition, by Neil Weste, in chapter 6, topic 6.2.3 Inductance, claims the following: Inductance and capacitance also set the speed of light in a medium. I know that $...
- 21
1 vote
2 answers
98 views
Time derivative of electric field associated with moving charge
The electric field intensity at a given point in a lab frame will vary in time if the point's position relative to a charge varies in time. If the position of the point from the charge's reference ...
- 635
7 votes
1 answer
666 views
Do higher-order virtual images between two mirrors move faster than light?
I was studying the case of an object placed between two plane mirrors. Whenever a object is placed between two parallel mirrors, the distances between the successive images is found using the criss-...
- 139
-4 votes
1 answer
164 views
Wavelength and Energy relation [closed]
Wavelength $\lambda$ formula: $$\tag1\lambda=\frac h{mv}$$ Put here value of $h$ as $$\tag2h=\frac Ef$$ Then formula becomes: $$\tag3\lambda=\frac E{fmv}$$ In this formula, wavelength is directly ...
8 votes
3 answers
1k views
Does a distant observer see the light for a longer duration due to the effect of time dilation?
I am currently learning about the basics of relativity and the concept of time dilation. I was thinking of an event as described below and curious to know what would happen Suppose, one shines a laser ...
- 201