Paradox Definition and 1000 Threads

In trying to come up with an example in S.R., I came up with the following: 2 rockets, a distance d apart as measured in the Earth frame, each have a speed of 0.8c and are on a head on collision with the other. What is the time to impact as measured in the Earth frame and on one of the rockets...

URGENT! T and U paradox Sorry I know I posted this already, but I realized that it isn't really introductory physics: Homework Statement I'm really confused about how I should do this problem and this is urgent so if anyone can help, it would be very much appreaciated. Thanks. T and U...

Hi Folks, I am stuck at a certain logic problem which is probably very common and easy for undergrad compsci students so forgive me if my question seems rather trivial. The question is this: 1. I believe the statement "This statement is false" is not a proposition and is paradoxical in...

Easy to understand problem (please read; I promise you'll understand): I've created my own financial spreadsheet. One of its functions is to allow me to automatically determine how much money I need to save every month m in order to accumulate x dollars in y amount of time. Normally...

was original EPR paper (as written by Einstein) contradicted uncertainty principal or was it against the copenhegon interpretation of QM? please tell me any website where original EPR paradox is discussed.

It is my understanding that the twin paradox arose from the fully reciprocal nature of special theory which shows that if a clock is moving past me in outer space that clock is ticking over at a slower rate than my clock but that from the point of view of a person accompanying that clock it is...

Hi, i thought of a paradox that I'm not sure i can resolve for myself. You have a 1-dim potential well of length L. You measure a particle to be within x=L/2\pm \sigma with equal probability. Assume sigma is very tiny. After a short time \Delta t the wavefunction has evolved to be...

This thing is making me pull my hair out: http://en.wikipedia.org/wiki/Bertrand%27s_box_paradox Can someone give me a good explanation of this? As for the Monty Hall Problem, I think I understand it. This is how I think of it: There is a 1/3 possibility of picking the correct door and 2/3...

I can't fully understand why a person who makes a journey into space in a high-speed rocket will return home to find his age less than an identical twin who stayed on Earth. It makes since for the twin who stayed on earth, but for the twin who traveled into space, he sees himself at rest and...

ok so this is kinda a silly idea i just came up with on the spot during math class because I am sure that like the rest of you on this forum, during high school 90% of math class was/is spent daydreaming because 90% of people need to be explained simple concepts a thousand times lol. so the...

The classical paradigm of how an object acquires gravitational potential energy goes like this: First, we take the case where the object is near the surface of the Earth which we define as the zero reference point. The object has a mass of 1 kg. We lift the object by an agent, such as a hand...

hi, recall the familiar round trip - it's more or less the same as in this arXiv article (http://arxiv.org/PS_cache/physics/pdf/0604/0604025v3.pdf) - round trip with acceleration g. me and my friends were wondering the following: imagine that the passenger abroad the rocket travels for 4...

I have a question about the Twin Paradox. I don't know if I'm right or wrong, but that's why I figured I would come here to ask. The way I understand things is that the twin on Earth's clock would end up being faster than the twin's clock out in deep space if the twin out in space was...

I have a paradox here. Please tell me what is wrong. I need to prove that \lim_{x \rightarrow a-}f(x) = -\infty f(x) = \frac{x}{(x-1)^2(x-3)} 1st case For all M , where M is a arbitrary large number, there exists \delta>0 such that f(x)<M whenever 0 < a-x < \delta 0 < a-x < \delta...

SR says that as an object reaches the speed of light its mass approaches infinity. How can light reach the speed of light without having an infinite mass?

Thought experiment / story: Albert the Alien sits atop a non-accelerating comet traveling 0.5c. He approaches earth, barely missing it, and passes on by. After he has passed Earth, he looks back toward it with his ultra-sensitive telescope and sees the face of Hyphy the Human. Hyphy the...

As I was reading Fabric of the Cosmos, I got stumped at the relativity of simultaneity section. This led me to Google for some additional explanation. I stumbled upon http://www.phys.unsw.edu.au/einsteinlight/jw/module4_pole_paradox.htm" which made me think of this question regarding the pole...

Einstein's resolution of the "clock paradox" I have read that most physicists believe that Einstein's resolution of the "clock paradox" or "twins paradox" is flawed and just plain wrong. I'm curious about what everyone here thinks about it. And I believe Einstein generally was interested in...

envelope paradox?? Maths can sometimes be nearly as interesting as physics... There are two envelopes on a table. Both have cash in, you don't know how much but one has twice as much as the other You can pick just one envelope, and you are allowed at most one swap. You choose envelope A say...

If we can agree that a black hole can exist, and that its gravitational field is intensified with its mass, the we can also agree that its gravity can create one hell of a gravitational lens. If that is the case, and EM radiation, whatever the frequency, is directed towards the black hole...

I may have discovered an explanation to the Zeno Paradox. However, in this explanation, the concept of a race between to objects at different speeds is simplified into one object traveling a given distance. The distance traveled in this example can be represented by the variable D. If the...

Problem Imagine a wheel of radius R consisting of an outer rim of length 2\pi R and a set of spokes of length R connected to a central hub. If the wheel spins so fast that its rim is traveling at a significant fraction of c, the rim ought to contract to less than 2\pi R in length by length...

Hi all, Physical law: I understand the derivation of the Planck law for the blackbody spectrum and why it takes slightly different forms whether you are doing the analysis in the frequency domain or the wavelength domain. That is to say, you cannot simply invoke the Planck relation...

I take a certain journey and due to heavy traffic crawl along the first half of the complete distance of my journey at an average speed of 10 mph. How fast would I have to travel over the second half of the journey to bring my average speed to 20 mph? [This is Problem 10 on page 18 in...

Homework problem given by Count Iblis to the PF community: Consider a box containing a pendulum of total mass M in a spacecraft that is in free falling motion. Suppose that the engines of the spacecraft are turned on and the spacecraft is accelerating at acceleration a, where a is...

Hi, I have the following problem: The formula for the Period of a classic pendulum is T=sqrt(L/g) Where: T: Period of the Pendulum suspended on a string. g: Earth's acceleration (=G*Mass_of_Earth/(Radius_of_Earth)^2 L: Length of the Pendulum String Now, let us...

Wikipedia: http://en.wikipedia.org/wiki/Rietdijk-Putnam_Argument Quote: "Two people pass each other on the street; and according to one of the two people, an Andromedean space fleet has already set off on its journey, while to the other, the decision as to whether or not the journey will...

Suppose i build a time machine , then go back in the past & kill myself . I die the instant i kill my past , but how in the first place i built the time machine ?

Take a look at this following paragraph that i wrote in another thread "think of two rockets moving at each other under inertia at a course so that they pass very close. Observer A will look at both clocks when the rockets pass. he will see his own as being T and he will see observer B,s...

I am just a little bit unsure about something I read on the "twin paradox". It talks about Dick and Jane who are twins, each 20yrs old. Dick departs at a speed of 0.80c to a star 20 light years away. So I'm sure you all know how the story goes, Dick is 50yrs old when he returns and Jane is 70...

So, I was thinking about a variation on the Twin Paradox, and was hoping someone could help me work through it. The motivation is the usual explanation for the Twin Paradox, namely that one twin accelerates and so breaks the symmetry. This begs the question of what happens when both twins ride...

http://en.wikipedia.org/wiki/Rietdijk-Putnam_Argument"

[SOLVED] Twin Paradox problem Here is a problem about twin paradox that I can't quite figure out. I got part a, but I can't get part b. I think that the 6 years spent doing research is kinda throwing me off. Help! The International Space Federation constructs a new spaceship that can...

The laws of Coulomb versus Ampere and the electromagnetic Machian "paradox" Here's an apparent paradox that has been tunneling about in my little mind lately. Maybe someone out there can help me with it. Imagine if you will, a vast empty region of space devoid of any visible distant...

Suppose one twin travel to a distance L and turn around, another twin travel to a distance L/2 and turn around. When they reunite at home, the twin travel longer will age less? Since they both experience acceleration, so acceleration is not the cause of age difference. Can acceleration break...

suppose we have a stationary observer 'A' at the origin. at t=0 rockets 'B' and 'C' pass the origin moving at gamma=10 but rocket B stops. when rocket 'C' reaches some point along the x-axis rocket 'B' accelerates to gamma=10 as measured by rocket 'C'. when rockets 'B' and 'C' meet its over...

According to the Wikpedia entry "[URL and this paper http://www.aapps.org/archive/bulletin/vol14/14_1/14_1_p03p07.pdf the conclusion reached by Bell in his paradox is still disputed even by some scientists today. Since the linked articles give plenty of mathematical explanations I...

There's one of the paradoxes with SR that I've never actually seen an answer for. There is a man on a train traveling at a velocity where length contraction starts to matter. Say, .3c. There are some dirty bandits that have rigged up a trap door system in a mountain up ahead on the tracks...

"twins' paradox" and acceleration Sorry to create another post with the twins' paradox as a central issue but I would like to explore one issue involved in it. Specifically, I have been told elsewhere that I am misunderstanding a claim about the twin paradox. As I understand it, the...

suppose we start with a long line of stationary, evenly spaced and perfectly synchronized clocks along the x axis. if the stationary twin is at the origin and at t=0 the other twin passes the origin moving at relativistic speed with gamma=2 then from the point of view of the stationary twin the...

Sorry about twin paradox again, I'll try to keep this simple as simple as I can. Initial situation: All participants are at rest, A1 and A2 are together at midpoint between B1 and B2. All clocks are in sync. _____________A1, A2 _____B1____________________B2 ---- A1 and A2 move...

Source: Physorg.com

Consider two point mass particles m1 m2 (with m1 different from m2) initially stationary relative to each other a distance x apart . The only force acting on them is attractive Newtonian gravity, i.e. Gm1m2/x^2 acting equally in opposite directions along the line of separation between the...

Quite often the explanation to the twins paradox is stated as acceleration breaks the symmetry or one twin feels acceleration while the other does not. I would like to add a new twist that analyses this explanation. Consider a push-me-pull-you rocket with two engines, one at either end so...

We know what is twin paradox is, and also why it is not a paradox, but my question is, "if we can not define absolute motion, how can we decide that the twin which went to space will age less, and not the home one?" That is to say that, when peter at home sees paul's clock moving slow (in...

Ok guys, Explain me this. In twin paradox, one of two twins, paul and peter, when paul goes for a space ride at very high speeds, and peter stays back at earth, when paul comes back, peter is older than him, and paul is still younger because of assymetric aging, also called time dilation...

Here is a very famous problem: A random two-child family with at least one boy is chosen. What is the probability that it has a girl? An equivalent and perhaps clearer way of stating the problem is "Excluding the case of two girls, what is the probability that two random children are of...

Hi! I am studying special relativity and I still don't understand completely the relativity of time dilation: each twin sees that the time of the other twin is dilated, so how can exist the asimmetry in the measurements (only one twin at the end has really dilated his time)? I'll make an...

Why do most explanations of the Twins Paradox claim that the twin on the spaceship ages less because he is the one who undergoes acceleration and/or changes direction, causing asymmetry between the points of view of each twin? It seems clear to me that the twin on the spaceship would age less...

I understand if this question sounds juvenile, because I thought of it after seeing a science fiction movie called Clockstoppers. In this film, a device (stopwatch) is used to speed up the molecular motion of an person body so that from their frame of reference, the rest of the world has slowed...