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Information & the Speed of Light


Hi there! So, my question is a bit of a lengthy one: First off, suppose that you have two astronauts, one hovering above the earth and the other hovering above Mars. On average, earth and Mars are about 12 light minutes away from each other, meaning that it would take 12 minutes for one astronaut to communicate with the other via radio, and 24 minutes to hear a reply. This because, of course, nothing can travel faster than the speed of light. But my question is, if you were to take for example, a long, LONG metal rod, completely rigid, and stretch it that distance of 12 light minutes in between the two astronauts, and they were to push and pull that rod between them, would you not then have a system where you can communicate faster than light speed? If the astronaut above the earth pushes and pulls on the rod, he/she could communicate with the other one using morse code or binary.
But would it work? Would the astronaut on the other end feel those pushes and pulls immediately, thus sending and receiving information instantaneously, or would it take 12 minutes for the impulse to reach the other side of the rod, despite the rod being totally rigid?

I hope this makes sense- it’s just a hypothetical obviously, but I cant figure out if this would work or not. It seems to me that it would, but at the same time information is supposed to obey the light-speed barrier. So I’m hoping you can get back to me, I’d love to hear what someone much more knowlegable in physics says about this! 😀

Aiden Cook

Define doppler’s effect?

if there is a relative motion between source of sound and observer, the apparent frequency of sound heard by the observer is different from the actual frequency of sound emitted by the source. This phenomenon is called doppler’s effect.

Quantum entanglement

onsidering the big bang and the singularity, what role might quantum entanglement have on every particle that came from the big bang? Is it possible that everything has some quantum connection? Scientifically? Ive been pondering this for a few days and i would love to hear some feedback.

Posted by Amon Kavanaugh 

Does Newton’s Laws fail here? – Asks Dikshit Gautam

When does the Newton’s third law fail?

Consider a point charge placed in empty space. It will create it’s own electric field, then let an another point charge comes in electric field of first at a distance ‘d’ and first charge exerts a force on second but the second charge’s electric field takes d/c time to reach the first charge. So, for that d/c time Newton’s third law fails.

Posted By Dikshit Gautam

What do you think dear students and Physics teachers?

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EMI – A Rectangular loop entering a uniform magnetic field.

I have one question friends –
If a rectangular loop is entering a perpendicular magnetic field then using Fleming right hand rule how will you explain the direction of induced current in the loop.
Pl explain how

WhatsApp Image 2016-08-05 at 4.02.25 PM(Mr. Nath posted)



Initially an emf will be developed across AD from D to A according to Fleming’s Right Hand Rule.

When the loop is completely inside the magnetic field, the emf across AD will be same as the emf across BC. Therefore, though CD is at a higher potential and AB is at a lower potential, no net current flows since the two emfs oppose each other equally.

(Vivekananda Sir said: Loop is moving inside the field so induced current will be in the direction DABCB.)


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