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If you click on Jorries calculator
http://www.einsteins-theory-of-relativity-4engineers.com/LightCone7/LightCone.html
you see in the default table that immediately comes up (without your doing anything) that the present-day CEH is 16.5 billion ly. What does that mean to you? How do you picture what is happening around that distance?
More precisely 16.472 but let's round it to 16.5.
Here's how I picture what that distance means. If some light from a distant galaxy is heading in our direction today it will eventually reach us only if it is already within the CEH. It will get here eventually only if has already made it within the magic circle and is within 16.5 Gly of us.
That light may have come from much farther away. It might have been emitted a long time ago from a galaxy which today is, I don't know, 40 or 50 billion lightyears from here. In fact it could even be losing ground at present: aimed at us but being dragged back by expansion. But it will still make it eventually if it is today within 16.472. The CEH is a kind of threshold.
Let's say the light is now at 16.47 Gly. Well the current Hubble radius, the distance that today is expanding at c, is 14.4 (as you can see if you clicked the link--it's one of the things the calculator gives you up front.)
So 16.47/14.4 = 1.14.
That light is in space that is receding at 1.14 c and it is traveling towards us at c, so it's net recession is 14% of the speed of light. But it will eventually get here! because it is within the Cosmic Event Horizon distance.
http://www.einsteins-theory-of-relativity-4engineers.com/LightCone7/LightCone.html
you see in the default table that immediately comes up (without your doing anything) that the present-day CEH is 16.5 billion ly. What does that mean to you? How do you picture what is happening around that distance?
More precisely 16.472 but let's round it to 16.5.
Here's how I picture what that distance means. If some light from a distant galaxy is heading in our direction today it will eventually reach us only if it is already within the CEH. It will get here eventually only if has already made it within the magic circle and is within 16.5 Gly of us.
That light may have come from much farther away. It might have been emitted a long time ago from a galaxy which today is, I don't know, 40 or 50 billion lightyears from here. In fact it could even be losing ground at present: aimed at us but being dragged back by expansion. But it will still make it eventually if it is today within 16.472. The CEH is a kind of threshold.
Let's say the light is now at 16.47 Gly. Well the current Hubble radius, the distance that today is expanding at c, is 14.4 (as you can see if you clicked the link--it's one of the things the calculator gives you up front.)
So 16.47/14.4 = 1.14.
That light is in space that is receding at 1.14 c and it is traveling towards us at c, so it's net recession is 14% of the speed of light. But it will eventually get here! because it is within the Cosmic Event Horizon distance.