Paradox Definition and 1000 Threads

According to what I have researched in Relativity (thanks to you guys) there is no such thing as absolute motion, time, or distance. I had a question about this paradox mentioned. Paraphrase: Two people that are exactly 20 years old are on earth. One decides to fly to planetX and some...

Check it out: http://imgur.com/EpYQv Where's the trick?

We consider a typical version of the EPR paradox where an electron and a positron are produced collinearly in the +y and -y with the spins polarized in the positive and negative z directions. The pair is emitted with zero linear and zero spin-angular momentum. If the positron is detected in the...

Suppose you have a circle with a diameter of 1. If you draw a square with all four sides touching the circle, the perimeter of the square is 4. Now suppose you indent each corner of the square so that they all touch the circle-this will make a cross shape, and the perimeter of it is still 4. Now...

I am confused about the twin paradox. Let's imagine Mike and Angela are twins. Mike stays on Earth, and Angela rockets off, away from Earth at close to the speed of light, with the intention of making a round trip back to Earth at the end of her voyage. My question is this: why wouldn't...

I am really trying to get my head around SR, in particular the twin paradox I have read so much about. From my very elementary understanding of the twin paradox, the basic reason for the twin that is traveling aging less is because he accelerates and thus breaks the symmetry between the two...

2 parts: 1. What does it mean if you get a negative gauge pressure value when calculating from manometer containing compound liquid? When calculating absolute pressure how does atmospheric pressure affect this negative pressure ie. atmospheric pressure opposes the direction of force? 2...

Hi, i want to ask about the basic explanation of twin paradox. In the explanation it says one twin has to accelarate to come back and the symmetry is broken and so one twin is older than other. Could you explain this symmetry and aging relation?

1. Suppose, a fast moving train (600,000 km long) running on straight line at speed 0.999c, perpendicular to A. 2. A is at point P. B stands in center of train. M point. Distance P to M is 300,000 km. C stands at end of train. D stands in head of train. 3. Now B flash light. According to B...

My paradox, dead or not according to different observers! 1. Suppose, a fast moving train (600,000 km long) circling on track (radius is 600,000 km, radius can be even more, this is just convenience reason) at speed 0.999c. A stands at center of the track. 2. B stands in center of train. C...

Bob sets on a voyage with a velocity 0.8c for total 6 years, leaving back Dave on the space station. On return Dave finds him younger by 4 years. Reciprocal results in time measurements in relativity make the theory redundant but here we see application of time dilation equation. This is...

i just realized, Andromeda paradox is flawed. I feel good, as compared with penrose, I am really just started in this subject. it is flawed becuase penrose mistakendly consider the"each day" for the person in moving (although very slow) and the person are the same. They are not same. the...

This has most likely been mentioned before and if so I apologise, I have seen a few similar discussions though didn't really see any answers that I was able to understand/accept. The problem is if there is an infinite amount of time in the past then how is there a present? (I know there can...

It is my understanding that all things travel through spacetime at the same speed. Additionally , I am told we are moving through space at some velocity. My question is this: If an object were made to travel in a direction opposite to our direction of motion , would that object not then be...

Ok, so I'm not a physicist by any means, and I don't actually understand the first thing about physics. So, I'm guessing that somebody's probably realized this before, and I just want to know the name of this "paradox" (i'm not even sure it's the right word) so I can read up on it. Here's the...

The Klein Paradox is the name given to the following prediction of Klein Gordon's equations. If you send a current of electrons against a potential barrier of height V such that the energy of the incident electrons is less then V - m, you should observe a current of positrons coming out of the...

So I understand local realism (the moon is there when we aren't seeing it) and the notion that Bell's Theorem says that if local realism is true, then we could perform experiments that show observation is independent of reality and that we should expect certain probabilities to arise. But we...

Hi, I'm an undergraduate physics student trying to comprehend why the twin paradox is not a paradox. The standard reply usually amounts to this: the dude in the spaceship has to turn around at some point to come back to Earth. So he accelerated during his journey (by changing his direction...

Hi all, I've been around with this question for a while,I googled it and I found some information,But I want you to help me more, The question is : From the beginning of the universe,Anywhere of the Universe you see,there is reactions that due to them new materials are being produced,and...

I may not be right exactly but however i stand corrected where necessary. Twin paradox experiment explains time dilation in space time. My understanding is like this, assuming twins at 10yrs each. If one makes a space travel and the other is at stationed on Earth (both being at initial...

So according to all if you drop a feather and a bowling ball on Earth in vacuum it falls at the same speed. So that says acceleration of gravity is not affected by mass only the momentum. And this says that even a moon size iron ball would fall at the same speed to the Earth as a feather(in...

Its my first post here so i say hello to you. I have a 'problem' with understanding relativity. Here is the thing: We have a train and a station. Station and train have same lengths measured in rest (v=0). Station has attached two detectors, one at rear and one at front. They have built...

Hello, Can someone explain the http://demonstrations.wolfram.com/TheAndromedaParadox/" ? What does it mean, philosophically/etc? Local and non-local events. Time? Was this paradox an invitation for an explanation of the unknown concept at the time called "spooky action at a distance"? Which we...

I thought of this today while studying relativity. Imagine a very large disc spinning with an arbitrary angular velocity. Perhaps w=57 rad/s (this is the speed of a CD, got this from a random physics text, whatever, the speed is really not important).. The speed of light is c=3*10^8 m/s...

Consider we initially have a ground state particle of a harmonic oscillator: \psi = \exp ( - a{x^2}) (neglecting nomalization) And we have a detector far in space monitoring the local probability of finding a particle. Now if we suddenly turn off the harmonic potential, the wavefunction will...

When (almost any) system emits gravitational waves, does information carried by these waves also 'counted' as an information about a system? In case of BH informational paradox, when BH dissapears, we get not only Hawking radiation, but also information encoded in the gravitational waves of...

As everybody I have read or heard on the matter claims, the Axiom Schema of Separation was concocted to resolve a paradox that results from the Axiom of Unrestricted Comprehension. The Axiom Schema of Unrestricted Comprehension as I understand it is stated as follows (forgive my lack of...

E & M Magnetism Relativity "Paradox" :confused:In theory the laws of magnetism are derivable from coulomb's law and special relativity. Right. While my physics homework group were doing a problem set, I came up with this seeming paradox. (This isn't a homework question). There are 2 senarios...

Could someone please explain the math behind the Second Ace Paradox? Here's the problem: http://www.futilitycloset.com/2009/02/06/the-paradox-of-the-second-ace/ I want to know how the poster got those probabilities... I can't figure it out on my own.

ok, i just can't figure this one out. you have heard of the example of the 2 wires, and depending on their currents, they will attract or repel each other because they "see" different amounts of protons/neutrons. so, this is what we call "magnetism" I just can't tie in electromagnetic...

I heard this interesting paradox, which I haven't been able to find anywhere online! Now, bear with me while I set it up! Suppose a professor has a countably infinite number of students. This professor secretly assigns to each student a real number in the interval [0,1], and thus ends up with...

The paradox, is basically a theory about time travel. This thread requires the assumption of making time travel possible. Supposedly, you go back in time and kill your grandfather before he gets married. How did you end up there in the first place?

watz gung wrong here

Let’s take an ordinary household thermometer and expose it to the air. The molecules of the air impact on the surface of the thermometer and transfer kinetic impulses. The thermometer transfers kinetic impulses to the impacting molecules as well. Eventually, thermal equilibrium is reached and...

Again on twin paradox! Hi! I'm trying to definitely solve the twin paradox (after 5 years of efforts :) ) In every physics textbook, it is studied the motion of the twin in an inertial frame (so the proper time is that measured in the twin frame), so we can express time delta t in the Earth...

Is Schrodinger's cat paradox a poor pedagogical example for students of QM? In the traditional formulation of the paradox, the cat is declared to be both alive and dead at the same time, but no proof is offered of how the paradox can not be resolved by simply assuming the cat is either dead or...

If I have a container containing a liquid mixed with some other substance that has much a higher boiling point (i.e. water and salt). This liquid will be in equilibrium with its vapor (the salt vapor pressure is negligible). Now I quasi-statically adiabatically expand this vapor. Isentropic...

Hi, I asked a theoretical question here a month or two ago and someone was able to help me. I have another: Imagine an interstellar race. Starship 1 heads from Earth toward Alpha Centauri at a constant rate close to the speed of light, then makes a loop and returns home. Ship 2 is faster, and...

If the equivalence principle is true then it means that the Earth's gravity field is a constantly accelerating frame of reference. In any accelerating frame of reference the direction of acceleration is always opposite to the direction of attraction. That means that for all observers on the...

Folks, apologies for reviving a thread that I know has been picked over, but I am a bit confused. I understand the explanation that "solves" the Twin Paradox -- Twin B in the rocketship flying close to light speed undergoes acceleration and deceleration on his outbound trip away from Earth...

In general terms, but not too general.

Suppose you have a source that send a very strong straight beam of light (say laser ) Then you direct the light toward a distant wall with angle 45 degree as show in the drawing below Then if you rotate the source 90 degree in one second, what is the velocity of the visual effect (spot)on...

Is this a paradox? We have a satellite orbiting at a significant amount of the speed of light around the earth. Hypothetical numbers: The satellite ages 6 years; while the; earth ages 7000 years. How does the satellite communicate with Earth or vice versa? How is information...

Hi guys. I'm new here and pretty much a layman when it comes to physics and astronomy. I came across this hypothesis a few months ago, but have been looking at it the last few days. Anyway, I'm hoping you guys know about this so you can help me. Search wikipedia for it if not. I'm not...

Hi, I am currently working on probability densities and one simple question came to my mind: Say we lived in an "2^aleph_0 world" which contains 2^aleph_0 mathematicans (dont screem already!). Now each mathematician chooses one real number between 0 and one in a bijective way. Now we can pick...

The wake is made because the inertia forces in the system ,right? So if i have low Reynolds number the inertia forces are negligible and the flow doesn't separate ,right? So In every low Reynolds number the flow doesn't separate (no wake) but low Reynolds number also indicate a viscous flow...

Solve the paradox of set theory V7.5 by LiJunYu 2010.12.25 email: myvbvc@tom.com or 165442523@qq.com Brief:All power sets of real number set R: P(R),P(P(R)),P(P(P(R))),...,Pn(R),...Because all Pn(R) does not contain its own,in Russell's paradox,"all sets which does not...

I've been quite potty these days and started couple of new threads, so I don't mind start another one, and I believe PF would very likely welcome such behavior. (Bring in potential clicks and members, although this is a little bit far out notion) You see, for every custom human society would...

Hi, I'm trying to model a wheel that is placed on top of a moving platform. The problem is that I'm running into a situation that seems very counter intuitive. I'm not sure if its a problem with my model or not. I've attached a picture that demonstrates the problem. To begin, neither the...

Why is the "Grandfather Paradox" considered a paradox? Feedback exists in other disciplines, so why not in physics? Isn't disallowing feedback in time akin to stating that a negative feedback system can never exist in nature? (And, yet, they obviously do!) Why not assume that, as in other...