Peter Lamont writes:
Percy, how can you say the expansion deccelrerated? There is absolutely no evidence - zero - for any 'slowing down' or 'deccelerating' of the expansion. If I say you are talking thru' your hat, you can't prove me wrong.
I can only repeat what I already told you way back in
Message 72. When the expansion settled down after the period of inflation around 13.8 billion years ago, it was decelerating. The expansion was decelerating for billions of years until it began accelerating between 5 and 10 billion years ago. This is from the
Wikipedia article on the Accelerating Universe:
Wikipedia writes:
In 1998, observations of type Ia supernovae also suggested that the expansion of the universe has been accelerating since around redshift of z~0.5
A redshift of z~0.5 corresponds to around 5.5 billion years ago. Here's an excerpt from the abstract of a technical paper titled
The Turning Point for the Recent Acceleration of the Universe with a Cosmological Constant:
T. X. Zhang writes:
The universe turned its expansion from past deceleration to recent acceleration at the moment when its size was about 3/5 of the present size if the density parameter in matter is about 0.3 (or the turning point redshift is 0.67).
A red shift of .67 corresponds to about 9 billion years ago. Gee, Peter, how could you not know that the expansion hasn't always been accelerating?
Percy, any accelerating expansion is inward.
Yes, we know you think this. So since the expansion was decelerating until around 5 billion years ago when it began accelerating, how did an outward expansion suddenly become an inward expansion?
--Percy