Speed of Light: Distant Galaxies & Observability

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Distant galaxies can recede from us faster than the speed of light due to the expansion of space, which does not drag light with it, making some objects unobservable. While objects moving faster than light may seem unobservable, light from these galaxies can still reach us if they are within our observable universe's light cone. The Hubble recession velocity can exceed the speed of light, with galaxies at certain redshifts moving away at velocities greater than c. The mathematics of this phenomenon is complex, but it aligns with models of cosmic expansion. Understanding these concepts is essential for grasping the nature of the universe and its observable limits.
cosmicpencil
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how can it be that the distant galaxies moove away from us faster than the speed of light and thus are not observable. now don't get me rong i know its not the objects mooving but space itself, any relevant theories on this ? thanks
 
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Objects moving at/above the speed of light are not necessarily unobservable just as objects moving faster than the speed of sound are not necessarily inaudible. You just have to be inside the light or sound cone to see/hear them. Ie, if an object passes you at twice the speed of sound at a distance of 1100 feet, you hear it 1 second after it passes since the speed of sound is 1100 fps and the sound only has to travel 1100 feet to get to you (draw a picture based on that and you can construct the shape and angle of the mach cone).

An object moving faster than the speed of sound isn't dragging its sound with it and an object moving faster than light (ie, via the expansion of space) is not dragging its light with it, though the expansion of space makes the math a little more difficult for light than for sound as there is a visible horizon to the observable universe.
 
cosmicpencil said:
how can it be that the distant galaxies moove away from us faster than the speed of light and thus are not observable. now don't get me rong i know its not the objects mooving but space itself, any relevant theories on this ? thanks

We can see (receive light from) objects with Hubble recession velocities greater than the speed of light (c). Objects at the particle horizon (redshift = infinity) have Hubble recession velocity = 2c in the flat, matter-dominated model, for example. In that model, objects with redshift equal to 3 are receding at c today and were moving away from us faster when the light was emitted long ago. If you want a popular explanation, see

"Misconceptions about the Big Bang," Charles H. Lineweaver & Tamara M. Davis, Sci. Am. 292, #3, Mar 05, pp. 36-45.

For an explanation for undergrad physics students, see

"Can galaxies exist within our particle horizon with Hubble recessional velocities greater than c?" W.M. Stuckey, Am. J. Phys. 60, #2, Feb 92, pp. 142-146.
 

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