On Monday, March 31, 2025 at 7:14:59 AM UTC-6 John Clark wrote:
On Mon, Mar 31, 2025 at 3:23 AM Alan Grayson <[email protected]> wrote: > *For Einstein to get his equations to permit a steady state solution, wouldn't his CC have to augment gravitational attraction, and thus be negative, but after it was discovered that the universe's expansion was accelerating, the sign of the CC was changed to positive? AG * *The Cosmological Constant would've been a property of space that gave it a constant negative pressure, and that would have been a sort of anti-gravity. If the negative pressure had been just strong enough to exactly counteract gravity and no stronger or weaker then it would have permitted a static universe, although it would have been unstable, the slightest nudge would have caused the universe to either collapse or expand forever. However Einstein didn't realize that at the time, if he had I don't believe he would've ever proposed it. As soon as astronomers discovered that the universe was expanding Einstein quickly abandon the entire Cosmological Constant idea.* *When in the late 1990s astronomers discovered that the universe was accelerating the cosmological constant hypothesis came back big-time because it could explain why the universe is accelerating (if it had just the right value) and quantum mechanics provides an easy way to explain how empty space could produce negative pressure. But they were problems, the amount of negative pressure that quantum mechanics says empty space should have is too large, 10^120 times too large. And very recently the evidence started to mount that the rate of acceleration of the universe is decreasing, and that doesn't fit the cosmological constant model because a property inherent to space itself, wouldn't be expected to change its strength with time. To put it in technical language, the cosmological constant died because the universe behaved like a jerk (**d³x(t)/dt³)*. *So if those recent astronomical observations turn out to be correct then dark energy must be dynamic. One possibility is Quintessence, a fifth fundamental force that produces negative pressure by way of a scalar field, that is to say a field gives every point in space an intensity but not a direction and that can change with time. Another idea is that dark energy (whatever that is) might decay into dark matter (whatever that is); this could explain why dark matter and dark energy are of the same order of magnitude today when there is no reason to believe that they should be anywhere close. * * John K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis>* Thanks for that data dump. When E was contemplating the CC, he knew that gravity was attractive and NOT the cause of the expansion implied for some values of the CC. Why then would he think that by assuming a repulsive CC which eliminated gravity, would imply a steady-state universe? AG awc -- 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/e65f518c-cfbe-487f-91b1-9c5fcc733579n%40googlegroups.com.
