2
votes
4answers
78 views

How much could one slow down aging using existing spacecraft?

Imagine that I board a spacecraft and head away from the Earth at top speed until I've aged twenty years, then I turn around and come back. How much younger will I be than the unexciting folk who hung ...
1
vote
0answers
19 views

Twice the speed of light [duplicate]

If you were able to ride along a photon and a second photon passed you in the opposite direction, would what you observe be twice the speed of light? And would that change what you would see of the ...
-5
votes
2answers
91 views

Do the laws of physics that apply to all observers also apply to a non-observer? [on hold]

The Timelessness of a photon https://www.youtube.com/watch?v=5ELA3ReWQJY An observer's laws of physics are time based. "When you're traveling at the speed of light, time does not exist" - Neil ...
-1
votes
3answers
108 views

Twin Paradox speed of light

Twin Paradox Can anyone clarify and or correct the following for me? A space ship is flying at speed v equal to 0.8 times the speed of light. Within the ship are three stations, a transmitter at ...
1
vote
1answer
107 views

GPS Satellite - Special Relativity

I'm going through an old relativity assignment, and I've been asked to calculate the time dilation for a satellite which orbits the earth in 12 hours at 26000km from the surface, and travels at a ...
1
vote
1answer
32 views

Light cone and order of events?

If one event lies outside the light cone of another, can the events to some observers appear in a different order in one reference frame compared to the other, and is this the only time when this is ...
0
votes
3answers
74 views

Problem on speed of light

As I was reading special relativity, my book says the speed of light is $c$ with respect to any other thing. Does that mean the speed of an individual photon is $c$ even with respect to another ...
-1
votes
0answers
54 views

Does anything at speed of light won't be able to see anything? [duplicate]

They say that if a object travels at the speed of light will be able to pause time only for that object, but if it travels at the speed of light, will the object will not see the light and see total ...
0
votes
1answer
111 views

Why doesn't light travel instantly? [duplicate]

I've read that the faster you travel in space, the slower you travel in time. And when you reach the speed of light (which we won't be able to) time will stand still. So when light travels at the ...
2
votes
3answers
616 views

Would a craft travelling increasingly close to the speed of light appear to be decelerating?

I've been pondering the implications of time dilation. Is it right to assume that if a craft was travelling at a speed very close to the speed of light (>= 0.9999c for example), that to an external ...
3
votes
4answers
209 views

Traveling between two planets at rest to one another [duplicate]

If I travel at relativistic speed from planet A to planet B which are at rest relative to one another, I will be younger than people on A or B when I arrive. However how does this mesh with the fact ...
1
vote
1answer
102 views

Can special relativity be extended such that the frame of a photon makes sense?

Suppose I want to know what the universe looks like from the perspective of a frame of reference moving at $c$ relative to my current frame. As discussed at length in various other questions on this ...
1
vote
1answer
67 views

Lorentz transformations, why $t$ and not $t'$?

In the derivation of the Lorentz tranformation you get the fromuls: $$x=k(x'-ut')$$ $$x'=k(x+ut)$$ where $k$ is a constant that is yet to be determied ($k= \frac{1}{\sqrt{1-\frac{u^2}{c^2}}}$) ...
1
vote
2answers
187 views

Is time subjective?

In Minkowski spacetime time is subjective [or more precisely: time is different for every particle/ reference frame]. It is the coordinate time of an observer whose reference frame travels up the ...
0
votes
3answers
70 views

Is proper time an intrinsic value of Minkowski space?

What is proper time? Is it a part of Minkowski space (that is a mere spacetime interval)? Or is it an intrinsic characteristic of massive particles (a sort of "aging")? Example: In the following ...
0
votes
1answer
52 views

Deriving Lorentz transformation - Serway

in Serway, the derivation of Lorentz transformation started from these two equations $$x′=\gamma(x−ut),$$ $$x=\gamma(x′+ut′).$$ The book derived the first equation and then deduced the second. Is ...
0
votes
1answer
51 views

How much time passed for the passenger traveling with at speed-of-light spaceship? [duplicate]

Let's suppose we have a spaceship with the exact speed of light. If a traveller takes this spaceship to go to proxima centauri (approximately 4 years light away from Earth) and come back, we (as ...
2
votes
2answers
74 views

Is it ok to have two events $A$ and $B$ so that for one person $A$ occurs before $B$ but for another $B$ preceds $A$

Imagine two laser beams A and B are released at the same moment to bounce between two mirrors, A was moving and B was at rest, doing the calculations I found that for a person at rest B would reach ...
10
votes
5answers
474 views

Clocks in special relativity

One book on special relativity says: Any observer at rest relative to his own timepiece will see that other clocks moving with respect to him run fast - the greater their speed, the faster they ...
0
votes
1answer
66 views

Relative speed when approaching the speed of light [duplicate]

According to this chart of the Lorentz factor as a function of speed: If a spacecraft neared (roughly) 0.85c, would it appear to be traveling at 1.7x the speed of light from the perspective of ...
0
votes
5answers
192 views

The speed limit is with respect to what?

As I understand, an object with mass cannot reach the speed of light because its (relativistic) mass increases "exponentially" as it approaches light speed. So there is a relation between mass and ...
1
vote
1answer
58 views

Help with Special Relativity velocity addition formula

While looking for question about speed of light I saw this Physics.SE question where I found this: $$v_\text{rel} = \frac{v_1 - v_2}{1 - \frac{v_1v_2}{c^2}}.\tag1$$ But in another answer there was ...
8
votes
4answers
669 views

Is there always a frame in which spatially separated events are simultaneous?

In relativity, if two events are simultaneous in a specified frame, they cannot be simultaneous in any other frame. My question is this: given any two events, is there always a frame in which these ...
3
votes
2answers
187 views

How is time not a constant?

I am a visual person, so it's hard to imagine the information I keep getting, but shouldn't time be a constant? If you were traveling at the speed of light and your able to cover $299{,}792{,}458$ ...
1
vote
2answers
57 views

Field interaction betweeen two point charges?

[SOLVED] Consider two particles A and B having equal charges and placed at some distance. The particle A is slightly displaced towards B.So, Does the EM force on B increase(+/-) as soon as the ...
0
votes
0answers
37 views

How do you determine who is moving “faster” in relativity? [duplicate]

I suspect this question has a simple answer, but I can't get my head around it. The classic example of a person in orbit around the Earth at high speed experiencing a slower passage of time than the ...
0
votes
1answer
53 views

Construction of Observer Coordinates in General Relativity

In A First Course in General Relativity, Second Edition, by Bernard Schutz, on the bottom of Page 8, he is expanding on the spacetime diagrams in Figure 1.5. He states "[...] the four angles are ...
3
votes
3answers
355 views

Twin Paradox: Still a Paradox?

Alright, so David Griffiths in his "Introduction to Electrodynamics" states that the Twin Paradox is not a paradox at all since the traveling twin returns to Earth. By returning to Earth, the twin had ...
7
votes
2answers
593 views

If a neutrino has a rest frame, why can't a photon have a rest frame as well?

Concerning Rest Frame Wikipedia states: For example, in the rest frame of a neutrino particle travelling from the Crab Nebula supernova to Earth the supernova occurred in the 11th Century AD ...
-2
votes
2answers
153 views

Can we glue femto-cameras to photons? [closed]

I know its not as easy as saying to glue nano-cameras to photons. Please consider the following extract (related to Heisenberg's Uncertainty principle) from the Modern's abc of Chemistry: ...to ...
0
votes
0answers
54 views

What is the age of the Universe from the big-bang light perspective?

What is the age of the Universe from the big-bang light perspective? We all agree that the universe is around 14 billion years, from the perspective of a hypothetical observer moving in a galaxy, ...
0
votes
1answer
51 views

Speed=mass=time? [closed]

I was wondering why objects gain mass with speed? How can we measure speed if there is no truly stationary point to measure from? And if an object comes to a stand still will it loose its mass? ...
0
votes
2answers
106 views

The speed of light and unstable matter

Mr.E is on a luxury spaceship travelling about 1/2 the speed of light and finds a cubic lump of unstable matter(attached to a bomb) in his cabin. He of course is an expert with bombs but this device ...
2
votes
0answers
78 views

About the speed of light

If Mr. E is aboard a spaceship traveling near the speed of light the usual reason for the spaceship not going faster than $c$ is the (relativistic) mass of the ship increases without bound, I think. ...
0
votes
1answer
62 views

Relativistic addition of velocities of spaceships

If Spaceship 1 is traveling at speed $.5c$ relative to Earth, and Spaceship 2 is traveling at speed $.3c$ relative to Earth in the same direction, what does Spaceship 2 see Spaceship 1's speed as? I ...
1
vote
2answers
174 views

How an accelerated object sees another accelerated body in special relativity?

Assume two objects are moving with a constant acceleration $a_1$ and $a_2$, which are the measured accelerations by respective object (or constant force being applied to each of the objects). My ...
2
votes
2answers
74 views

Is speed of light ( Sun-to-Earth ) related to the movement speed of solar system?

The speed of light has been measured to be 299 792 458 m/s. Now, the Solar System is traveling at an average speed of 828,000 km/h (230 000 m/s). Summing up the numbers we get close to 300 000 000 m/s ...
9
votes
3answers
1k views

What happens when relativistic effects stop?

I'm currently learning special relativity in high school and we only primarily deal with what happens when an object is moving at constant relativistic speeds. But what if the object slowed back down ...
0
votes
1answer
75 views

In space I am moving wrt to what?

Let us suppose I am running on a street. When my eyes are open, I can see many things moving backward, and thus it gives me an idea that I am moving wrt those things. Not even this, even if I close my ...
0
votes
1answer
68 views

Observers in Special Relativity

Suppose I am an observer in Minkowski space, observing a particle traveling with a constant velocity $v$. If I want to calculate the particle's Lorentz factor, given that the particle is traveling at ...
1
vote
3answers
276 views

Derivation of the general Lorentz transformation

The standard Lorentz transformation or boost with velocity $u$ is given by $$\left(\begin{matrix} ct \\ x \\ y \\ z \end{matrix}\right) = \left(\begin{matrix} \gamma & \gamma u/c & 0 & 0 ...
1
vote
1answer
107 views

Does the light speed change in media? [duplicate]

Does the light speed change? The Theory of Relativity says that the speed of light in vacuum is the same and unchangeable, while I read that the speed of light in glass is lower than in air, and that ...
0
votes
1answer
67 views

How does time dilation work in this situation?

It is my understanding that when moving near the speed of light, time slows down relative to other things not moving so fast. Based on this principle, would it be theoretically possible to travel a ...
0
votes
0answers
68 views

does an object travelling close to the speed of light in an inertial frame of reference behave Relativistically

The two tenants of Special Relativity are: The laws of physics are the same in all inertial frames of reference. The speed of light in free space has the same value $c$ in all inertial frames of ...
0
votes
0answers
51 views

Can we travel faster than light? [duplicate]

Consider two cars going in opposite direction one at speed $c/2$ and other just greater than $c/2$, then one bus will appear to other moving at speed more than $c$. How can an object travel at speed ...
1
vote
2answers
46 views

How would an electron bunch/beam look different in the rest and lab frames?

With respect to special relativity, I was wondering how the spatial dimensions would differ between the rest and LAB frame of an electron beam. System: Electron bunch/beam traveling in linear motion. ...
0
votes
4answers
118 views

Two clocks along different worldlines

I have been reading and watching videos about this subject for a while now. I just can not seem to grasp the idea. Let's say we have two clocks. I leave one at home and keep one in my pocket. Then, ...
4
votes
4answers
185 views

What will be the relative speed of a photon in a light ray to another photon of opposite direction light ray?

If two light rays start simultaneously in the space from exactly opposite ends in opposite direction that is separated by a distance of 600000 km in a way they meet at the mid point (300000 km from ...
3
votes
1answer
114 views

Can a simulated Universe simulate Special Relativity

I know there are theories (or postulates) that hold that our Universe could be a simulation. I was wondering, if Special Relativity states that two events which are not causally linked can be judged ...
0
votes
3answers
72 views

Question about relative speeds on a different “scales of perception”

I was kind of puzzled yesterday when thinking about this. If we observe an object moving away from us with 10m/s we would say the object is moving away from us really slowly But if we (humans, ...