Young Earther cosmology:

Originally posted by twhitehead
Why? I don't understand how you come up with that.

I don't see why you put a 6,000 year limit on the universe.

I'm not the one who put a 6,000-year limit on the age of the universe; a literalist (YE) interpretation of Genesis puts a 6,000 year limit on the age of the universe.

If the universe is only 6,000 years old, then light can have traveled at most 6,000 years to get here. Ergo, 6,000 light-years is the maximum radius of the universe. That's obvious.

Einstein's theory assumes that the speed of light is fixed. This implies that the size of the universe depends on its age. The YE-hypothesis, which we are discussing here, assumes that one of the other parameters is fixed (namely, the age of the universe). This implies that some other parameter must be altered in order to account for the observed size of the universe.

There are two choices: either a) the speed of light is fixed, which means the universe must be much smaller than we actually measure it to be (which requires an explanation why our measurements are wrong, not merely an assertion that they are wrong). Or b) the universe is as big as it appears to be, in which case the speed of light must be variable (for which there is as yet no experimental evidence).

Unless some YE-er has another plausible explanation for how big the universe is (or appears to be) within his fixed horizon of 6,000 years.


Light would have have to have travelled almost instantaneously for Adam to see any stars.

It gets worse. Light would have to have travelled almost instantaneously for the universe to be as big as we now measure it to be in only 6,000 years. It would then have to have slowed down from near-instantaneousness to it's present speed. For which there is as yet not only no experimental evidence, but not even a plausible hypothesis how this could be possible.

I think we can both agree that the YE-hypothesis hasn't a leg to stand on, given our present state of knowledge of physics and astronomy. But we knew that last Thursday !

EDIT: If Einstein's theory is correct, then space cannot be stretched any faster than the speed of light. So 'space stretching' doesn't salvage the YE-hypothesis either.

It is an intriguing question whether Adam saw any stars. I'd never thought about that before. Our nearest luminous neighbor (apart from Sol, of course), is Proxima Centauri (a trinary system) at 4.2 l-y. This means that Adam could have seen it at the soonest 4.2 years after he was created. Before that, the night sky must have been devoid of stars. Before that, the night sky must have been black, apart from the moon and planets.

Here is a list of our nearby luminous neighbors.

https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs

Barnard's Star would have appeared after Alpha and Beta Centauri (the other two members of the Centauri trinary); Barnard's is 5.9 l-y away and would therefore have been visible no sooner than 5.9 years after creation (if the YE-hypothesis were correct). At least a dozen other stars are 12 - 15 years away, so they would have appeared very close in time to each other--a veritable stellar fireworks display.

One would think that cosmic events such as the night sky changing from pitch black to spangled would have merited a mention in the ancient history books. No such thing was recorded; the night sky was spangled long before people looked up at it. Looks dim for the deniers of deep time.

Originally posted by menace71
How would light be effected by let's say a young universe 6000k to 10000k years old if as RJ states that God stretched out space ? it should be severly redshifted right ?

Not only would it be severely red-shifted but things would not appear to be so far away. The light you would see would be from when they were still receding as the stretch was taking place.

Originally posted by moonbus
If the universe is only 6,000 years old, then light can have traveled at most 6,000 years to get here.

Ergo, 6,000 light-years is the maximum radius of the universe. That's obvious.

Only if the speed of light is constant. If it isn't then your unit of measurement "light-years" is incoherent. So no, it is not obvious, it is incoherent.

Einstein's theory assumes that the speed of light is fixed.
Not really. It assumes the maximum possible speed of causation is fixed. Not quite the same thing.

This implies that the size of the universe depends on its age.
No, it doesn't. It does imply that the size of the visible universe puts a lower bound on its age.

I think we can both agree that the YE-hypothesis hasn't a leg to stand on,
Of course.

EDIT: If Einstein's theory is correct, then space cannot be stretched any faster than the speed of light. So 'space stretching' doesn't salvage the YE-hypothesis either.
I don't think Einsten's theory fixes the speed of light. i.e. it doesn't say that it has always had a specific value.
Space stretching doesn't salvage the YE-hypothesis for many other reasons. The main one being that it doesn't in any way solve the problem. ie if space was stretched out you still wouldn't see the stars at a great distance. You would either see them close up or not at all.

Originally posted by moonbus
Barnard's Star would have appeared after Alpha and Beta Centauri (the other two members of the Centauri trinary); Barnard's is 5.9 l-y away and would therefore have been visible no sooner than 5.9 years after creation (if the YE-hypothesis were correct). At least a dozen other stars are 12 - 15 years away, so they would have appeared very close in time to each other--a veritable stellar fireworks display.

The centre of the Milky Way is about 27,000 light-years from us, so the Milky Way would not have been visible at all to this day.

This implies that the size of the universe depends on its age.
"No, it doesn't. It does imply that the size of the visible universe puts a lower bound on its age. "

I grant that the visible universe may not be all there is. There is a visible 'horizon', in a manner of speaking, represented by how far light can have traveled since the universe cooled off enough to become transparent to light. If there were anything beyond that, it would be invisible.

Originally posted by moonbus
EDIT: If Einstein's theory is correct, then space cannot be stretched any faster than the speed of light. So 'space stretching' doesn't salvage the YE-hypothesis either.

Actually Special/General Relativity does not say that 'space cannot be stretched faster than light'.

This is the basis for many a proposed faster than light propulsion system for just that reason...
You may not be able to travel through space faster than light... but if you could just move the
patch of space you're floating in faster than light....

More to the point, it currently looks like the future of the universe may well be a 'big rip' scenario
where 'dark energy' makes space expand faster and faster until even atomic nuclei are pulled apart.

Even looking at today's universe there is an event horizon beyond which we cannot and can never
see because the space between us and them is expanding faster than the speed of light.
[say, for example the expansion was 1m/s per 46 ly, then objects about 13.8 billion ly away would
be receding from us at about the speed of light... Objects farther from us than that are receding
from us at more then the speed of light. We will never see them. As the rate of expansion appears
to be increasing the distance to this event horizon is shrinking. At some point every galaxy we can
currently see will disappear behind it, then the other stars [or their remnants] in this galaxy will
disappear... and then everything left will be ripped apart.]

Originally posted by twhitehead
Only if the speed of light is constant. If it isn't then your unit of measurement "light-years" is incoherent. So no, it is not obvious, it is incoherent.

[b]Einstein's theory assumes that the speed of light is fixed.
Not really. It assumes the maximum possible speed of causation is fixed. Not quite the same thing.

This implies that the size ...[text shortened]... ll wouldn't see the stars at a great distance. You would either see them close up or not at all.

I was at Bell Labs working on Ion Implanters and there was a talk there given by Alan Guth about BB inflation theory.
He mentioned some numbers, which I forget now, of the starting size, basically zero, and something like 1/10^23 second later it was the size of a football, something like that, but using those numbers I came up with a number of how fast inflation proceeded at the start: 22 orders of magnitude greater than the speed of light.
During the question and answer period I asked the same question about the speed of light limit and how could the universe break that limit.

His answer: 'You did your arithmetic correctly' 🙂 and went on to explain space does not obey the speed of light limitation, he was acknowledging my 'arithmetic' was correct that the fledgling universe indeed had that great a rate of expansion, 22 orders of magnitude greater than c.

Originally posted by googlefudge
Even looking at today's universe there is an event horizon beyond which we cannot and can never
see because the space between us and them is expanding faster than the speed of light.
[i][say, for example the expansion was 1m/s per 46 ly, then objects about 13.8 billion ly away would
be receding from us at about the speed of light... Objects farther ...[text shortened]... om us than that are receding
from us at more then the speed of light. We will never see them.

Actually, we would see them.

http://users.etown.edu/s/stuckeym/AJP1992a.pdf

Originally posted by sonhouse
.... and went on to explain space does not obey the speed of light limitation

Well that should be obvious given that space expansion is not movement through space.

I also have to point out that it is not known that the universe is finite so the bit about 'the size of a football is incorrect'. To be more accurate you should say that two points were the diameter of a football apart after that time period.

I am curious to know how one would determine or measure that space had expanded if there were no objects in the space to use as reference points.

Originally posted by moonbus
I am curious to know how one would determine or measure that space had expanded if there were no objects in the space to use as reference points.

I assume this is done mainly by observing the vast number of the most distant galaxies that we can see and note their average Doppler shift to see if they are generally moving away from us.
This, of course, is using the assumption that such a general outward movement of the most distant galaxies cannot be so adequately explained by those galaxies simply moving through space relative to us but without space itself expanding (I haven't yet really thought of the problems that would arise trying to account for that outward movement if we assume that space itself did NOT expand; anyone? What is the most serious problem with that?)

Originally posted by moonbus
I'm not the one who put a 6,000-year limit on the age of the universe; a literalist (YE) interpretation of Genesis puts a 6,000 year limit on the age of the universe.

If the universe is only 6,000 years old, then light can have traveled at most 6,000 years to get here. Ergo, 6,000 light-years is the maximum radius of the universe. That's obvious. ...[text shortened]... faster than the speed of light. So 'space stretching' doesn't salvage the YE-hypothesis either.

Thanks this is a great explanation that YEers have to contend with. As far as we know there has not been a decay in the speed of C.... My only question as many YEers believe is that God stretched Space-time which there is credence for this ( expansion of space-time) at a rapid pace objects might appear to violate the speed of C then right?

Manny

Originally posted by menace71
Thanks this is a great explanation that YEers have to contend with. As far as we know there has not been a decay in the speed of C.... My only question as many YEers believe is that God stretched Space-time which there is credence for this ( expansion of space-time) at a rapid pace objects might appear to violate the speed of C then right?

Manny

The young-universe hypothesis requires so many miracles -- not only creation ex nihilo, but 'bending' laws of physics, stretching space, altering the speed of light etc. etc. -- that you might as well just call the whole thing black magic. Given that none of what it proposes matches empirical observations, it does not even deserve the name "theory".

This is not to say the Big Bang Theory explains everything, but at least it does not require us to put laws of physics in abeyance or to suppose that laws of physics were radically different 6,000 years ago.

For example, if the speed of light had radically changed some time in the last 6,000 years, I would expect there to have been something analogous to a sonic boom (a photonic boom?, or at any rate a noticeable 'blip' ), traces of which should still be visible somewhere in the cosmos.

EDIT: the current candidate for the most distant object yet observed in the universe is about 13 billion l-y away from us. I don't see how any amount of fiddling with the numbers of space-stretching or the speed of light can account for the discrepancy between a supposed Biblical age of the universe of about 6,000 years and that light having been underway for 13 billion years. Not even a creative accountant can fiddle the numbers that much.


http://phys.org/news/2012-11-hubble-candidate-distant-universe.html

Originally posted by humy
What is the most serious problem with that?

It would put us at the centre of the expansion making us special and there is no good reason to think we are special.
The second issue would be one of density. If matter were expanding away from us we would expect a significant fall off of density with distance - which we do not observe.