[ExI] Eternity in six hours: intergalactic spreading of intelligent life and sharpening the Fermi paradox
johnkclark at gmail.com
Wed Sep 11 15:23:07 UTC 2013
On Wed, Sep 11, 2013 at 5:38 AM, Andrew Mckee <andymck35 at gmail.com> wrote:
> I'm sure you're right, so far as we know. I just wonder if some really
> advanced civilizations might discover a wrinkle or two that enables them to
> develop technologies that to us, seem to violate our known scientific laws.
You can "maybe" yourself to death but it never gets you anywhere. Maybe ET
is made of klogknee particles that Earth scientists know nothing about; and
maybe it's a unknown law of physics that engineers made of those mysterious
klogknee particles must be crappy at their job and that's why the universe
doesn't look like it was engineered. Well maybe, but probably not.
>> We know very little about Dark Matter but one thing we do know is that
>> it doesn't interact with electromagnetic waves, that's why it's so hard to
> > Not to gleefully jump from the frying pan into the fire... But I'd reply
> that some would say Dark Matter and Dark Energy are really hard to detect
> because they are just huge fictional fudge factors added to prop up a
> seriously broken gravitational universe model
For years people have tried to modify the law of gravitation so that it is
consistent with what we see with our telescopes but it just doesn't work.
If you observe the Bullet Cluster what you see is 2 clusters colliding and
the regular matter that we can see staying in the center just as we'd
expect regular matter to do and the Dark Matter (detected by gravitational
lensing) remained spread out just as you'd expect Dark Matter to do. There
is no way modifying gravity can explain that.
And in addition, if you tinker with gravity so that galaxies like our own
Milky Way hold together and behave as they should then galactic clusters
like the Local group don't behave as we see them do. And if you tinker with
gravity in another way so that galactic clusters behave as they do in our
telescopes then individual galaxies don't. But if you invoke Dark Matter
then everything comes out fine.
As for Dark Energy, it's even more mysterious than Dark Matter. The best
guess, and it's only a guess, of what it is does indeed involve a
modification of Gravity. When you solve partial differential equations such
as those in General Relativity you end up with a function and a constant
term; Einstein first thought that the constant term, called the
Cosmological Constant, was nonzero, but then he changed his mind and said
it was zero and calling it nonzero was the greatest blunder of his life.
Today many are starting to think that Einstein may have been right the
first time around, among other things it can explain why the universe
changed from deceleration to acceleration just 5 billion years ago, long
after the Big Bang. Einstein was such a winner that his blunders are more
interesting than most people's triumphs.
And if you do the math you find that the amount of Dark Energy needed to
accelerate the observed Normal Matter and it's five times more common
brother Dark Matter by the amount we observe it to me accelerating, it
turns out that the universe has precisely the amount of mass-energy needed
to produce a flat universe; observations made just a few years ago showed
that the universe is indeed flat, or at least isn't curved much, over a
distance of 13.8 billion light years if the universe curves at all it is
less than one part in 100,000. I think that's unlikely to be a coincidence
John K Clark
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