Faster than c?

@UtkarshPKumar said in #24:

at Akbar2thegreat (in #6): yes you are correct till certain extent, we have found out that the universe is expanding faster than light which means it might end in "big RIP" (thats a whole lot of another story) but don't forget motion is relative. It happens so, That our
galaxy is moving and the galaxy we are observing is also moving in the opposite direction so if you see it this way both of these bodies are moving 1/2C but we perceive the galaxy we are observing is moving apart at speed of light (because we think we are stationary).

That's not quite the reason we observe galaxies which seem to move away from us at c. I might be misunderstanding you here. I'm under the impression that you're arguing that we see a distant galaxy moving away from us at c because both our galaxy and the distant galaxy are moving through space at c/2 (relative to the Hubble flow), but in opposite directions, their relative velocity therefore adding up to c/2 + c/2 = c. That's not the case.

There are (to my knowledge) no galaxies with peculiar velocities (velocity relative to the Hubble flow) near c/2. Galaxies are not moving through space that fast. Typical peculiar velocities are in the hundreds of km/s, maybe in the low thousands of km/s in highly dynamic galaxy clusters (source: https://en.wikipedia.org/wiki/Peculiar_velocity#Cosmology). Nowhere near c/2 ≈ 150,000 km/s.

Even if there were, this model could not account for the observational fact that we see galaxies with apparent recession velocities in excess of the speed of light all around us. Our Milky Way galaxy cannot move at c/2 in two opposite directions at the same time (that's a contradiction).

Even if it could, you just cannot add relativistic velocities the way you add slow velocities in Newtonian mechanics. In special relativity the relative velocity u is given by u = (v + u')/(1 + (v*u')/c^2), not by u = v + u' (as in Newtonian mechanics), where v and u' are the individual velocities measured in an external inertial frame.
See: https://en.wikipedia.org/wiki/Velocity-addition_formula#Special_relativity
Adding velocities in special relativity can therefore never produce a velocity greater than c.

In your example of two objects moving away from each other at v = c/2 and u' = c/2 respectively (as measured in an inertial frame external to both objects), their relative velocity measured in this inertial frame would be: u = (4/5)c = 0.8c
This is only 80% of the speed of light.
Even if we increase both velocities to 99% of the speed of light, we will obtain a relative velocity lower than c (instead of the classically expected 1.98*c):

u = (0.99c + 0.99c)/(1 + (0.99c0.99c)/c^2)
u = (1.98c)/(1 + (0.9801c^2)/c^2)
u = (1.98c)/(1.9801)
u = (19800/19801)c
u ≈ 0.9999495c

The relative velocity would only be about 99.995% of the speed of light, even though the individual velocities were both already 99% of the speed of light. This is a direct consequence of the fundamental postulate of special relativity that the speed of light is always measured to be exactly c = 299,792,458 m/s regardless of the motion of the emitter relative to the observer ("The principle of invariant light speed").

The above treatment of velocity composition concerned velocities through space.
However, the recession velocity of distant galaxy is not (significantly) due to a motion of the galaxy through space (such a peculiar motion usually occurs at much less than 1% of the speed of light). It's due to the metric expansion of space between that distant galaxy and our galaxy. None of the two galaxies is travelling through space anywhere near the speed of light, the relative velocity just appears to exceed c because all of those billions of light years of space between them are slowly being stretched out.

Oh and also due to this motion of celestial bodies faster than C (in relative context) the observable universe will loose all its stars except for our local cluster and the space will be alone except of milkdromedia galaxy which our future generation would see dw we might find ways to go to other galaxies but thats for another story again.

Mind-boggling. And absolutely correct!

Dont see ahead if you want to be in peace...
To conclude things very nicely un-confusingly neutrino can travel faster than light... i guess you might Have figured that out of from the end of the video. Lemme eaze out things its still under debate.

You're probably referring to this: https://en.wikipedia.org/wiki/Faster-than-light_neutrino_anomaly
The experiment had limited accuracy. I quote:

"On July 12, 2012, OPERA updated their paper by including the new sources of errors in their calculations. They found agreement of neutrino speed with the speed of light."

So this doesn't look like a likely candidate for disproving Einstein's relativity. Neutrinos probably cannot travel faster than light. It has since been discovered that they actually have nonzero mass:
https://en.wikipedia.org/wiki/Neutrino_oscillation

They are so light that they are usually ultra-relativistic particles (travelling very near the speed of light). But special relativity predicts that they will not be able to reach the speed of light.

@natbee56 said in #21:

If that’s the case, we will be always dizzy, and the high tides to Low tides interval is like 1 second, and the time to the next earth quakes is less than 10 sec!
You are wrong. I can't explain you well as I am not an expert. Only a physicist can explain to you much better than me. Consult some known physicist. Also, note that some physicists believe that light is the ultimate speed. So, ask other section of physicists.

@SD_2709 said in #22:

Like what? 'Objects' as in planets or stars or as in particles?
Any type of objects, not specific, that can be faster than light.

@Akbar2thegreat said in #25:

Read:
bigthink.com/technology-innovation/what-travels-faster-than-the-speed-of-light/
You could have said "Particles in space move faster than light" not "Objects in space move faster than light"

@FC-in-the-UK said in #20:

I am sorry but that doesn't make any sense.
That clearly shows you know nothing about it. Kartikey seems to be intelligent guy who knows basic theory well but I have seen advanced and higher level physics on the matter that agrees with my earlier statement that light is not ultimate speed.

@natbee56 said in #33:

You could have said "Particles in space move faster than light" not "Objects in space move faster than light"
Take it that way then. But again it shows that speed of light isn't the ultimate speed which I was saying before. If it was, then literally everything in the entity (universes) would obey it. My point stands correct.

Faster than c?
some ppl say that fortran or assembler is faster than c

@absicht_MAUERzuBAUEN said in #1:

Why can nothing be faster than light? Surely, the more energy you have, the faster you are. And there is no maximum amount of energy you can have, right?
I tried to look online, but to say I do not understand a word would not be accurate at all.

I don't know if someone mentioned this already, but there is nothing that definitively proves that c is a constant. It has only been measured 2-ways, and therefore at the extremities, it could be considered instantaneous in one direction and c/2 in another.

@Akbar2thegreat said in #34:

That clearly shows you know nothing about it. Kartikey seems to be intelligent guy who knows basic theory well but I have seen advanced and higher level physics on the matter that agrees with my earlier statement that light is not ultimate speed.
Hey, you missed 'a' in my name. Why everyone miss letter a? And I am learning from my father as well as from YouTube.

@obladie said in #5:

Quantum Entanglement implies instantaneous information transfer, but discussing that will make your head hurt.

The way I understand it it's merely correlated spin. If I took a 2 DVDs of Shrek and gave you 1 and sent the other to the moon you could tell what the contents of the DVD on the moon is pretty much instantly. However if you burn Spiderman to your DVD that you have it will not modify the DVD on the moon, all you would be doing is destroying the correlation

because of this you cant really transfer information, all it really is, is a copy of the information

@Thalassokrator (in #31)

So this doesn't look like a likely candidate for disproving Einstein's relativity. Neutrinos probably cannot travel faster than light. It has since been discovered that they actually have nonzero mass:
en.wikipedia.org/wiki/Neutrino_oscillation

Thanks for that i used to believe its still under debate or under process of checking errors in the experiment or something.

In special relativity the relative velocity u is given by u = (v + u')/(1 + (v*u')/c^2), not by u = v + u' (as in Newtonian mechanics), where v and u' are the individual velocities measured in an external inertial frame.

Again thanks for the relative velocity formula. In books (of school) we are just given with definition and least possible formulas (i hope its the case for only pre 9th standards) so i thought of this at a smaller scale (a car and a man going in different direction) i concluded it as the right formula for finding relative velocities (lol). The next part of the formula ((1+v*u')/c^2) do anything with the light coming to us (the observer) from the object so it doesn't become faster than light?

None of the two galaxies is travelling through space anywhere near the speed of light, the relative velocity just appears to exceed c because all of those billions of light years of space between them are slowly being stretched out.

Wait what so you mean the space is getting stretched (so are the light spectrum and causing red shift) CMBR (cosmic background microwave radiation) became microwave due to streching of space so that means space(as whole) is expanding or is the universe the entire space ? Is big RIP about the space getting ripped ? I guess i might want to reconsider some of the previous video i watched before getting completely confused. I now get that how are galaxies going out of the observable universe if galaxies

@Vax_Mandates_Are_Bad in #37
Yes you are true what speed of light we are known to is a 2 way speed of light so we don't know the actual speed of light 1 way in any direction but the major problem (kind of a problem i guess because it no more a problem) comes is that we can never know 1 way speed of light
Think of it like: think we have colonised mars
Scenario: Suppose sending message from earth to mars took 20 minutes and from there to earth instant. And time is 1:00
To find one way speed of light we need the clock of the astronaut and the communicator on earths clock in sync so our communicator sent the time(right now i.e) to astronaut and told to add 10 to it (as It takes message 20 minutes from there to here and so the 1 way average time would be 20/2 i.e 10 mins note: no one is aware of the real 1 way speed of light). The astronaut receives It at sets time to 1:10 time on earth is 1:20 the clocks are no more in sync but for them they think they must be in sync due to 1 way average i.e 10 mins. The communicator before (at 1:10 earth time) had sent a message asking the time thinking he would have set his clock (1:10) the message reaches at 1:30 earth time on mars. The time on mars at 1:30 on earth as Set by the astronaut (1:10 at 1:20 earth time) now is 1:20. so he sends a message back saying its 1:20 as its instantaneous it reaches earth at 1:30. The commander adds 10 mins to 1:20 (1 way average that he thinks is the time taken by the message to reach earth from mars) which sums to 1:30 the same time on earth.
Conclusion: they couldn't prove that 1 way speed of light as we know is wrong.

What i'd like to say is in this relative time space. even if speed of light (as the EMW and not C or it will violate conservation of energy-mass) is not uniform and is based on direction:

1. we will never come to know
2. it wont make any difference to the scenario where 1 way speed of light is average of 2 way speed of light
3. still special relativity would apply the same and object wont be able to travel faster than speed of light in that direction