On 5/31/2025 9:00 PM, Alan Grayson wrote:
On Saturday, May 31, 2025 at 5:39:19 PM UTC-6 Brent Meeker wrote:
On 5/31/2025 3:22 PM, Alan Grayson wrote:
On Saturday, May 31, 2025 at 2:24:00 PM UTC-6 Brent Meeker wrote:
And to be clear it was thought that the Hubble parameter was
decreasing asymptotically to a constant value. But /even
with the Hubble parameter constant/ a receding galaxy is
slower when it's close and recedes faster as it gets further
away. The recession speed is proportional to the distance;
that's Hubble's law.
Brent
*
*
*This is confusing. Does Hubble's law hold in a universe where
the expansion is speeding up? TY, AG
*
*Depends on what you mean by the speed of expansion. Hubble's
parameter is the expansion speed per distance, so speed is
proportional to distance. Hubble's law assumed this to be a
constant. Then since every galaxy is moving to a greater distance
then every galaxy is speeding up.
Brent*
*
*
*Doesn't that imply that distant galaxies, at earlier times, were
moving faster than nearby galaxies, *
More distant galaxies are always receding faster than less distant
galaxies. But in the past those more distant galaxies and the nearby
galaxies were both closer than they are now and so were both receding
more slowly than they are now.
*and thus contradicts the fairly recent finding that the rate of
expansion is increasing, not decreasing? *
"Rate of expansion" is NOT the speed of galaxies. It's the Hubble
parameter, the constant of proportionality, H, in the equation
(recession speed of galaxy at distance d) = H*d. Note H has the
dimension of 1/time, NOT length/time. The recent discovery is that H is
increasing. Any value of H>0 implies that more distant galaxies are
receding faster than less distant galaxies.
Brent
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion visit
https://groups.google.com/d/msgid/everything-list/da9577d9-91b5-4444-8933-22d8f13c16e2%40gmail.com.
