# swaha

Senior Members

159

1. ## define measurement of length

what if we have a continuous source of light? how do we know which light signal to observe. 2 signals may start at different times to reach us. pls explain.
2. ## define measurement of length

well then please explain how is actually length measured? suppose 2 people have 2 rods of same length when they were at rest. when one starts moving the other sees the length of the rod different. y?
3. ## a problem regarding interference.

i didnt understand. how can the photon interfere with itself? half a photon i didnt say what i meant was half the no of photons are in one beam the other half in the other beam. suppose u have water in a large pipe & want to distribute it in two equal pipes. half the no of molecules go in one pipe other half to the other. y this isnt true regarding photon particles??? pls explain.
4. ## measurement of length in relativity

well then how we actually measure it can u please explain.
5. ## black hole mystery

nucleus of an atom is the densest part for much of the rest is a vaccum. still density of nucleus is not as great so as to even stop lights to escape. does it mean within blackholes nucleus gets squeezed for any other arrangement i suppose the volume will be greater. if soth can be squeezed=> there must be some things within it too. ie protons etc are not fundamental. am i right by any chance? please explain.
6. ## a problem regarding interference.

i was reading quantum mechanics by dirac where i found he proposed that the same photon has equal probability to stay in two interfering beams simultaneously. i didnt get what is the difference in supposing the other way which is simpler that half of the photons are in 1 beam the other half in other beam. the proposition was regarding 1 photon so statistically the probability remains same. besides this idea was avoided in polarization case. why? where no new theory was required to be proposed. please explain.
7. ## how was speed of light measured?

we cannot observe any event before light coming from that point reaches our eyes. so how can we measure the relative velocity between any reference frame & light? & how can we say this remains constant?
8. ## measurement of length in relativity

if length is defined to be nothing but some times a standard length only then why 2 people one moving with respect to the other measures differently the distance between two points? previous answers i got from people is that it is so for the concept of simultanity differs to the two people. what i dont get is what it's got to do with length? if we cannot understand two distance to be same if light doesnt reach our eyes simultaneously then what if we are having a continuous source of light? two light rays started at different times may reach our eyes at the same time even when we r moving. ho
9. ## define measurement of length

i want to know how to measure length in relativistic mechanics. i mean if length is some times of a particular value of length ie what we call standard length why does it change/ appear to change when someone moves with speed comparable to the speed of light. i got the answer that since the concept of simultanity changes length seems different in two different reference frames one moving with a velocity not zero relative to the other. my question is what length has got to do with simultanity?
10. ## A Thought About Time Travel

if u travel time may be u dont become part of it just see it like u do in tv that may also serve the postulate.
11. ## time travel

if u travel faster than light may be u actually go to ur past but can anybody explain what to see then? for by lorentz transformations you get an imaginary length.
12. ## The Official "Introduce Yourself" Thread

hi i am new. pls tell me how to create threads & reply to other threads. have a few doubts.
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