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The wiki article on the Hubble volume says that the Hubble volume is often confused with the limit of the observable universe. This thread: When will the Hubble volume coincide with the volume of the observable Universe? seems somewhat inclusive and is related, but not identical. Is it possible for us to see beyond the Hubble sphere? I would think it isn't because it makes no sense if you think about seeing something which is receding faster than light. I think that light from us will never reach the body, and hence will never reflect off the body to come back to us. But apparently it works somehow.

My focus is upon the counter-intuitive nature of the Hubble Volume's definition, rather than the actual equations which describe the furthest point identifiable.


marked as duplicate by Pulsar, stafusa, Sebastian Riese, glS, AccidentalFourierTransform Jun 26 '18 at 0:22

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A crucial mistake in the question's reasoning is that the electromagnetic radiation doesn't need to be emitted by us and reflected by the receding body. Any radiation from there can help us see.

But yes, we can see objects beyond the Hubble sphere right now. The main concept behind this is the fact that the Hubble sphere is expanding as the universe expands.

Let's imagine a photon traveling towards us from a body beyond the Hubble Sphere. The definition of the Hubble Volume tells us that the photon's traveling through a region which is receding from us faster than the speed of light, hence the photon will be receding from us as well, at the difference between the speed of expansion of the universe at that point and the speed of light.

However, sometimes the speed at which the Hubble sphere is expanding is faster than this speed at which the photon recedes. So at some point of time, the photon will end up inside the Hubble sphere, after which we deal with it easily.