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Ho distant can we look into space by using a telescope? With "telescope" I mean here any device able to detect photons of any wavelength.

In terms of distance, is it correct to sat that observing the cosmic microwave background (CMB) is the ultimate limit we can look at? Since only at that time photons decoupled from matter.

m137
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  • Universe is expanding i.e the radius of spherical universe is increasing since Big-Bang.How could we detect some photon which is very far away if we try to detect then it need to move with speed greater than light which is not permitted by ST Relativity. – baponkar Dec 11 '19 at 12:40
  • Well yes thats the limit. We cannot observe further than that – seVenVo1d Dec 11 '19 at 20:39
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    @baponkar This is incorrect. According to FLRW, we can see light from the areas receding away from us at three times the speed of light: https://physics.stackexchange.com/questions/518543/at-what-cosmological-redshift-z-does-the-recession-speed-equal-the-speed-of-l/518558#518558 – safesphere Dec 12 '19 at 04:53

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