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{{QuoteBox|The problem is this: even assuming the big bang timescale, there has not been enough time for light to travel between widely separated regions of space. So, how can the different regions of the current CMB have such precisely uniform temperatures if they have never communicated with each other? This is a light-travel–time problem.<ref name="Lisle" />}}

{{QuoteBox|The problem is this: even assuming the big bang timescale, there has not been enough time for light to travel between widely separated regions of space. So, how can the different regions of the current CMB have such precisely uniform temperatures if they have never communicated with each other? This is a light-travel–time problem.<ref name="Lisle" />}}

A number of solutions to this problem have been proposed, including several versions of an "inflationary model", in which space itself expanded faster than the speed of light early in the Big Bang, but ''after'' different areas exchanged radiation to even out the temperature.

A number of solutions to this problem have been proposed, including several versions of an "inflationary model", in which space itself expanded faster than the speed of light early in the Big Bang, but ''after'' different areas exchanged radiation to even out the temperature. This model fits the data, as the CMB is only uniform at certain scales; over large enough areas anisotropies are visible in the field that match what one would expect from a rapidly expanding gas. However, there is no consensus on which explanation is correct, and each of the proposed solutions has its own problems.<ref name="Lisle" />

However, there is no consensus on which explanation is correct, and each of the proposed solutions has its own problems.<ref name="Lisle" />

== Flaws in arguing for an old universe based on starlight ==

== Flaws in arguing for an old universe based on starlight ==