On 9/11/2024 1:16 AM, Quentin Anciaux wrote:
Le mer. 11 sept. 2024, 10:08, Alan Grayson <[email protected]> a
écrit :
On Tuesday, September 10, 2024 at 3:50:08 PM UTC-6 Quentin Anciaux
wrote:
Le mar. 10 sept. 2024, 23:19, Alan Grayson
<[email protected]> a écrit :
On Tuesday, September 10, 2024 at 2:19:42 PM UTC-6 John
Clark wrote:
On Tue, Sep 10, 2024 at 3:57 PM Alan Grayson
<[email protected]> wrote:
*>> Even if you ignore Dark Energy and
postulate that the Hubble constant really is
constant, every object a megaparsec away (3.26
million light-years) is moving away from us at
about 70 kilometers per second. So if you try
to look at objects a sufficiently large number
of megaparsec away you will fail to find any
because they are moving away from us faster
than the speed of light.*
>/That was in the past. At present, the universe is
expanding at about 70 km/sec./
*Galaxies are receding from the Earth at 70 km/sec for
EACH megaparsecdistant from Earth they are. The
further from Earth they are, the faster they are
moving away from us, so if they are far enough away
they will be moving faster than the speed of light
away from us. *
*
*
/> You're assuming the universe today is infinite,/
*NO! I said IF the entire universe is infinite today
then it was always infinite, and IF it was finite
10^-35 seconds after the Big Bang then it's still
finite today. I also said nobody knows if the entire
universe is infinite or finite. *
*>*///Hubble's law applies to the past, not to the
future,/
*What the hell?!*
*How about an intelligent reply? Obviously, if the
universe is infinite today, it was always infinite. But
that's what I am questioning. For galaxies to fall out of
view, they have to moving at greater than c. Now they
aren't receding that fast. How will they start moving that
fast? You're applying Hubble's law without thinking what
it says. Just because a galaxy is now receding at less
than c, how will continued expansion increase that speed
to greater than c? AG *
The farther they are the faster they are receding from you, so
as they continue to get farther away they receed faster from
you till the point they receed faster than c and go out of
your horizon.
Quentin
Prove it, if you can. I see the separation distance increasing
linearly as the radius of the sphere expands, so light can reach
either galaxy, from either galaxy. AG
To address your point about the linear increase in distance, here's
how distant galaxies can still recede faster than the speed of light,
even with constant expansion:
1. Hubble’s Law:
Hubble’s Law shows that the recession velocity (v) of a galaxy depends
on its distance (d) from us:
v = H0 * d
Where H0 is the expansion rate. This means that as the distance
increases, the recession velocity increases proportionally.
No. Note that v is just ddot = H*d So it's a differential equation
with solution d=c*exp(Ht) where c is the distance at time zero.
Brent
2. Linear increase in distance:
You're right that, with a constant expansion rate, the distance
between two galaxies increases linearly with time. However, because
recession velocity depends on distance, the farther apart two galaxies
are, the faster they recede from each other. So, even if the distance
grows linearly, the recession velocity grows proportionally with distance.
3. Hubble Distance:
The key point is the Hubble distance:
d_H = c / H0
At distances greater than this, the recession velocity exceeds the
speed of light (c). This doesn't violate relativity, as it's the space
between galaxies that expands faster than c, not the galaxies moving
through space.
4. Analogy of the balloon:
Think of two points on the surface of an inflating balloon. As the
balloon expands at a constant rate, the distance between the points
increases linearly. However, if the points are far enough apart, they
will move away from each other faster than a closer pair of points.
Similarly, in the universe, even though the expansion rate is
constant, galaxies farther apart recede faster due to their increasing
distance.
5. Why light can’t reach us:
For galaxies beyond the Hubble distance, the space between us expands
faster than light, meaning their light can never reach us. This is why
galaxies eventually move out of our observable universe.
In summary, even with a linear increase in distance due to constant
expansion, the recession velocity increases with distance, and for
sufficiently distant galaxies, this velocity eventually exceeds c.
*John* K Clark See what's on my new list at
Extropolis <https://groups.google.com/g/extropolis>
hwt
--
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 on the web visit
https://groups.google.com/d/msgid/everything-list/5485c7a2-a527-448a-b337-3c8c60466d73n%40googlegroups.com
<https://groups.google.com/d/msgid/everything-list/5485c7a2-a527-448a-b337-3c8c60466d73n%40googlegroups.com?utm_medium=email&utm_source=footer>.
--
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 on the web visit
https://groups.google.com/d/msgid/everything-list/829f73fd-cd48-41d2-813a-18c576f447a4n%40googlegroups.com
<https://groups.google.com/d/msgid/everything-list/829f73fd-cd48-41d2-813a-18c576f447a4n%40googlegroups.com?utm_medium=email&utm_source=footer>.
--
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 on the web visit
https://groups.google.com/d/msgid/everything-list/CAMW2kAqckvzcs4bUy4cBSvcM9WUaT%2B35MdB7UuA1QaxmrkdXdg%40mail.gmail.com
<https://groups.google.com/d/msgid/everything-list/CAMW2kAqckvzcs4bUy4cBSvcM9WUaT%2B35MdB7UuA1QaxmrkdXdg%40mail.gmail.com?utm_medium=email&utm_source=footer>.
--
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 on the web visit
https://groups.google.com/d/msgid/everything-list/93f5c232-108e-48e4-a5b9-a3fc486b05dc%40gmail.com.
