On 9/9/2024 12:51 PM, John Clark wrote:
On Sun, Sep 8, 2024 at 9:13 PM Alan Grayson <[email protected]>
wrote:
*>> if you extended a line from you to any point on the sky it
would eventually hit the center of a star, and so every point
on the nighttime sky would be as bright as the sun. But that's
not what we observe.*
/> As for the *unobservable* part of the universe, moving away at
faster than light speed, I conjecture that Inflation is the cause./
*I'm not talking about inflation, just the normal everyday expansion
of the universe, which has been known since the mid-1920s, means that
stars a finite distance away are moving away from us faster than the
speed of light , and so the light from them will never reach us. *
/> if we run the clock backward, they would eventually come back
into view, /
*Yes there are stars that we can see today that we won't be able to
see tomorrow, 1 trillion years from now we won't be able to see any
stars except those that are in the Milky Way because those stars are
gravitationally bound together.
*
*And not just the Milky Way but also Andromeda, with which we will have
collided by then, plus several small galaxies that are part of the local
group. https://en.wikipedia.org/wiki/Local_Group
*
/> I disagree with your final conclusion. Even if the universe is
infinite, many stars that are directly in our line of sight, might
be too faint to be seen, as is the case of nearby brown dwarf
stars, which comprise 50% of stars in our relatively nearby
neighborhood, but too faint to see./
*SiriusAis the brightest star in the sky but it has a companion,
Sirius B, which is hotter and, because the light emitted of a hot
object is proportional to the size of the object and to the fourth
power of the temperature, is much much brighter, and yet it is
impossible to see unless you have a fairly large telescope. That is
because although its light is very intense Sirius Bis far smaller than
Serious A. One has a diameter of about 1,000,000 miles while the other
has a diameter of only 6800 miles, so even though it's very intense
the total amount of light given off is much less than SiriusA.
*
*I think his idea is that there are dark bodies and so Olber's paradox
is resolved by there being enough dark bodies to intercept you
line-of-sight and create the dark background of space. I don't believe
it, but it could be true in a different universe.
Brent*
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