If the Universe is 13.8
billion years old and cosmic speed limit is 386,000 mi/s, how can the radius of
the universe be 46.5 billion light-years?
Modern instruments see light
that is 13.8 billion years old. Due to the expansion of the universe, its waves
have been stretched into microwaves, the cosmic microwave background (CMB).
But, while that light traveled 13.8 billion years to get here, the universe
was busy accelerating outward in all directions, taking that object with it, up
to 46.5 light-years away.
For example, telescopes
see GN-z11 (picture below) as it was 13.39 billion years ago. Meanwhile, that galaxy was swept many more billions of light-years away by of the expanding universe.
Light from the oldest objects has already been stretched never reach Earth.
There is no limit on how fast the universe can expand, only on how fast things
inside the universe can move relative to each other.
It’s somewhat like the
case of two inchworms crawling in opposite directions on a 10-inch elastic band
at one inch per minute. If the band is stretched to twice its length during the
first minute, the inchworms will be four inches apart rather than the two inches
predicted by their top speeds.
As the expansion
continues, more and more distant objects cross the horizon of observability where not even light-speed travel would be fast ever catch up to it.
So, we have an estimate from
science of 93 billion light-years for the diameter of that part of the universe
whose objects beam light that could reach Earth at some point in the future. Studies
of the CMB suggest that the radius of universe is 250 times that.
We can’t rule out the
possibility of an infinite universe. It’s possible that the observable portion
of the Big Bang is but a small ripple in an infinite universe that is unknowable.
That doesn’t mean that
the universe would have been around for an infinite amount of time. Infinity is
not a measurement. It’s a concept. Even if an infinite amount of time could
produce an infinite universe, a doubtful assumption, an infinite amount of time
has not yet passed. So, if the universe as a whole is infinite, it must be
without beginning.