On 3/10/2025 11:48 PM, Alan Grayson wrote:
On Tuesday, March 11, 2025 at 12:33:36 AM UTC-6 Brent Meeker wrote:
On 3/10/2025 11:04 PM, Alan Grayson wrote:
On Monday, March 10, 2025 at 11:15:07 PM UTC-6 Brent Meeker wrote:
On 3/9/2025 11:14 PM, Alan Grayson wrote:
I don't think you understand my question. Without a CC, or
equivalently setting it to zero, don't we get a universe
which is in UNSTABLE equilibrium, like balancing a pencil of
its writing tip, so the universe expands or contracts in a
very short time interval? Isn't this the issue Einstein
faced? If so, why would he choose a positive CC? AG
No, Einstein's model with the CC=0 was static. The model when
I was in grad school was an expanding universe with the CC=0
but the expansion kinetic energy was just balanced by the
negative gravitational potential, so the universe would
expand forever but slowing asymptotically toward static.
Brent
Now I am totally confused. If E's model was static with CC=0,
Sorry, I miswrote. I intended to say Einstein had to make the
CC>0 in order to balance the gravitational attraction.
Brent
OK. Does setting CC>0 result in unstable equilibrium as I think Clark
claimed, and discovered by Arthur Eddington? IOW, will the universe
suddenly contract if it is expanding? AG
No, it's unstable as a static universe, which was the general opinion of
astronomers at the time. The Milky Way was the only known galaxy. The
other smudges in the night sky were "nebula". So Einstein calculated a
value for the CC that would just balance the gravitational attraction of
the Milky Way, to explain why it hadn't collapsed. But this produced an
unstable equilbrium. It was about 10yrs later that Hubble discovered
the universe was much bigger than just the Milky Way and it was expanding.
Brent
it agreed with what astronomers thought in 1915, so why would he
add a positive CC, tantamount to a repulsive force as you earlier
claimed, to counteract what he then thought was a false
prediction of GR of an expanding universe? Does anyone have a
coherent answer to what's going on with the CC? AG
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