Paradise Cafe Discussions - A Place For Bible Research And Christian Encouragement

Hi Folks

According to the BBC: "Nasa's Hubble Space Telescope (HST) has captured its deepest view of the Universe, producing images of galaxies that have never been seen before."
http://news.bbc.co.uk/1/hi/sci/tech/8401374.stm

Now, I'm curious about a couple of things in this article - but the main thing is this statement:

"This highly sensitive camera can see starlight from far-off objects - light that has been "stretched" by the expanding Universe."

If it is light itself that has been "stretched", what is the speed limit of this "stretching"? It cannot be merely the speed of light, because it's light itself that is stretched!

That would be like saying the road itself is limited to the speed limit of the road!

If you had a 1,000 mile stretch of road, in which the speed limit was 50 miles an hour, does that mean the 1,000 mile stretch was laid down in 20 hours? (1000 miles divided by the speed limit of the road, ie. 50 miles an hour).

Of course not. The speed limit of the road has nothing to do with the length or age of the road!

And yet this is what they do when they estimate the age of the Universe.

They take the distance they can see.. say, 15 billion light years (the "road")... and then use the speed of light (the road's speed limit) to determine its estimated age.

But as the article says, it's LIGHT ITSELF that was "stretched"!

So in what way does the speed of light have anything to do with the age of the Universe?

Surely it's the speed of the "stretching" that really matters! And THAT is not restricted merely to the speed of light.

The speed at which the road was laid down has no correlation with the road's speed limit.

:coffeeread:

ya...and the light that is 30 billion years away won't be seen by our eye balls for another 15 billion years...correct? don't fret...it's on its way...patience now, patience.

:funnyface:

"Space," it says, "is big. Really big. You just won't believe how vastly hugely mindbogglingly big it is. I mean you may think it's a long way down the road to the chemist, but that's just peanuts to space, LISTEN!" and so on..."

- The Hitch Hiker's Guide To The Galaxy, Douglas Adams

:D

One of the "must reads"... after the Bible, of course :redface:

Hi Int,
Iso knows far more than me on this subject.

I think the BBC quote must be referring to the, Red Shift.

If you remember; light from fast receding galaxies, appears to have undergone a frequency change and looks to be centred on a lower frequency/longer wavelength by the observer. Hence the spectrum is moved in the red direction. Of course, the relative speed of the light has not changed, as is the case in the sound Doppler Shift. Since the received light is longer, from one peak of the frequency cycle to the next, the light has therefore been stretched.
The speed of light, apparently, cannot change, according to Einstein.

You will be a brave stout fellow if you put old Einstein to rights! :)

Derek

When I studied astronomy it was called the Doppler-Fizeau effect.
On stars receeding from us it is called the red shift.
If they were moving toward us, it would be the blue shift.

We know what stars contain from the light that reaches us.
We look at the apparently white light through a spectroscope which splits the light into its spectrum.
That light will contain absorption lines from Carbon, Iron etc. and emission lines from glowing gasses such as Helium. These appear as dark and light lines in their spectrum respectively, at specific places in the spectrum. Each element has its own distinctive pattern.

Now the speed of light does not change, but the frequency of its wavelength does.
So if a star is moving away from us, the dark absorption lines that should be in the blue area of the spectrum, will have shifted slightly toward the red end.
The greater the shift, the greater the speed of the star that is receeding........hence red shift.

When the distintive line pattern of an element has shifted up or down the spectrum we know the star is receeding or advancing (as in a binary star).

So the spectra of stars tell us their contents, their speeds and any reflected light from planetary bodies which contain other lines tell us what those planets contain too. So sunlight reflected from Jupiter contains extra lines and tells us it contains methane.

Besides those good answers, the age of the universe estimate is only the youngest that it could be. As gogh alluded, there may be galaxies beyond the apparent limit whose light has not reached our telescopes yet. So the Universe could be older still.

Re: "...beyond the apparent limit whose light has not reached our telescopes yet"

When we do get to take a peek......the star (source of light) will be long gone.....:whistle:

actually, gogh, the fact that the star may or may not be long gone isn't really relevant. the light it emitted at a certain point in time (past) has been travelling at -- drum roll please -- the speed of light :huh: in all 360 degrees and all three dimensions (of our spatial perception). so, holding all other factors aside, it would reach us eventually here at our little ole' earth. but (don't ya just hate it when there's a 'but'?) :readthis: here's the real kick in the side. if said star is receding from us faster than the speed of light (yes, that is quite possible due to the exponential rate of the expansion of space itself), then we will never see it; but not because the star is no longer there. once the light emitted by the star leaves its stellar source, the light is on its own. :thinking: know what i mean?

incidentally, yes einstein's theory of special relativity does mandate that the speed of light is constant and is the maximum speed limit of all things physical -- all else being equal. but there are exceptions to every rule, and this rule is no expection. :D it gets kinda complicated from here, so this is where i'll stop. :funnyface:

questions for pondering:

how far and how fast can space ultimately "expand"? what exactly does that mean? :dontknow:

is there a "limit" (boundary) to space itself? if so, what is beyond? :dontknow:

it can get pretty "existential" in a hurry, can't it? :whistle:

iso-don't know nuttin' ;)

Howdy iso. This can be a fun topic, yes?

Re: "...if said star is receding from us faster than the speed of light..."

If one was on the other side/receiving end/in front, of said receding star...would one see it?...grin

:thinking:

You would see it, but would you see it before it hit you?

yep. and as may be deduced from some of the discussion above by others, that light would be blue-shifted (compressed; the opposite of "stretched-out") to the observer to whom the star is approaching, rather than receding.

it would not be unreasonable to postulate that space is expanding at some multiple (a number greater than one) of the speed of light. which means we won't ever know what all is out there; i.e., how "big" the universe is. :whistle:

Dawn of the Galaxies

http://antwrp.gsfc.nasa.gov/apod/ap091209.html

:coffeeread:

Good morning Everybody:

All -Sky Milky Way Panorama


http://antwrp.gsfc.nasa.gov/apod/ap091125.html

Onward and Upward Everybody! Maybe one day we'll see some of this "stuff" up close, Jah and Jesus willing!!!

Much Christian Love and Prayers to ALL:grouphug::heartbeat:
sis

Hi Isomam

If it's not "unreasonable" that the expansion of space could be expanding faster than the speed of light... could it ALSO therefore be possible then that the Universe is younger than distance we can see (i.e. 13.7 billion light years)?

Also, what is the speed limit of the expansion of space?

I would imagine THIS is the critical factor for determine the real age of the Universe.