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Author | Topic: Starlight | |||||||||||||||||||||||||||
kbertsche Member (Idle past 2160 days) Posts: 1427 From: San Jose, CA, USA Joined: |
quote:Setterfield was selective in the data which he used, he did not account for error bars when fitting his curve, and he had no physical motivation for the unusual functional form that he chose. FYI, Setterfield's claim that the speed of light has changed was debunked long ago by Aardsma, another young-earth Creationist: Has the Speed of Light Decayed?
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cavediver Member (Idle past 3672 days) Posts: 4129 From: UK Joined: |
Are these peer-reviewed journals ? They all propose a faster speed of light in the past. Yes, PRD and PLB are two of the most important journals for Theoretical Physics - probably the most prestigious is Nuclear Physics B (NPB). PRD does tend to get filled with plenty of crap, though. Variable speed of light theories (VSL) are nothing new. The albrecht paper is rather Mickey-Mouse in its approach - the ideas are ok but it is pure conjecture without any proposed mechanism - and the repeated use of "superluminal expansion" stinks of someone not quite getting it. Moffat is an old-timer, usually playing with fringe ideas. If you want to look at a modern paper on possible VSL (which is actually a variation in the fine structure constant, rather than c itself, as that is a fairly meaningless concept) then try this. Notice the observationally determined bounds on possible variation.
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Dr Jack Member Posts: 3514 From: Immigrant in the land of Deutsch Joined: Member Rating: 8.3 |
which is actually a variation in the fine structure constant, rather than c itself, as that is a fairly meaningless concept That's interesting; if it's not too complicated to explain, why is that?
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onifre Member (Idle past 2980 days) Posts: 4854 From: Dark Side of the Moon Joined: |
Hi Mr. Jack,
Cavediver writes: which is actually a variation in the fine structure constant, rather than c itself, as that is a fairly meaningless concept
Mr.Jack writes: That's interesting; if it's not too complicated to explain, why is that? Here's an article that can give you some basic understanding on it before Cavediver get's a chance to answer it.
The fine structure constant Alpha quote: Hopefully Cave can explain it better for us. Hope the article helps, though. - Oni "I smoke pot. If this bothers anyone, I suggest you look around at the world in which we live and shut your mouth."--Bill Hicks "I never knew there was another option other than to question everything"--Noam Chomsky
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riVeRraT Member (Idle past 445 days) Posts: 5788 From: NY USA Joined: |
I loosely studied on my own Astronomy around 10 years ago. I have an 8" Newtonian on an equatorial mount. I have seen down to 13th magnitude with it using averted vision.
I understand the Hubble concept, but I have a question. can we measure the red shift stars close to us, in our own galaxy. Do we only see their motion relative to our galaxy, or can we see the motion from the big bang?
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Taq Member Posts: 10085 Joined: Member Rating: 5.1 |
From my understanding, stars in this galaxy are gravitationally bound so there shouldn't be an observable redshift due to expansion. Redshift is seen between our galaxy and galaxies that are not gravitationally bound to our galaxy. As one example, there is an observed blueshift in the Andromeda galaxy because it is coming right for us.
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onifre Member (Idle past 2980 days) Posts: 4854 From: Dark Side of the Moon Joined: |
As I understand it...
can we measure the red shift stars close to us The redshift occurs with distant galaxies, not individual stars. Especially not anything in our Local Group - which is what I'm assuming you were visibly looking at. In fact, our Local Group, which the 2 largest galaxies are the Milky Way and Andromeda, are actually coming toward each other.
quote: Source Furthermore, both redshift and blueshift aren't a visible phenomenon, it's is a measurment of the frequency of the emited light.
quote: Same source as above.
Do we only see their motion relative to our galaxy, or can we see the motion from the big bang? Relative to us, and only when they are far enough from us. Hope this helped. - Oni "I smoke pot. If this bothers anyone, I suggest you look around at the world in which we live and shut your mouth."--Bill Hicks "I never knew there was another option other than to question everything"--Noam Chomsky
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cavediver Member (Idle past 3672 days) Posts: 4129 From: UK Joined: |
Hi RR - as Taq has already explained, stars within our Galaxy are in orbit about the Galactic core, and this massively dominates any effect of the Universal expansion. Likewise, neighbouring galaxies are far more affected by local gravitational effects than the expansion. You have to look past the Local Group of galaxies to start to see real evidence of the expansion.
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Taq Member Posts: 10085 Joined: Member Rating: 5.1 |
You have to look past the Local Group of galaxies to start to see real evidence of the expansion. Will this always be the case? If expansion is accelerating will there be a point where expansion overpowers the gravity within a galaxy?
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onifre Member (Idle past 2980 days) Posts: 4854 From: Dark Side of the Moon Joined: |
Hi Taq,
If expansion is accelerating will there be a point where expansion overpowers the gravity within a galaxy? According to the Big Rip hypothesis that's exactly what will happen.
quote: Hope this helped. - Oni Edited by onifre, : No reason given. Edited by onifre, : No reason given. "I smoke pot. If this bothers anyone, I suggest you look around at the world in which we live and shut your mouth."--Bill Hicks "I never knew there was another option other than to question everything"--Noam Chomsky
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cavediver Member (Idle past 3672 days) Posts: 4129 From: UK Joined: |
If expansion is accelerating will there be a point where expansion overpowers the gravity within a galaxy? Not under normal accelerative expansion - the gravitationally bound elements will stay gravitationally bound. This will probably extend as far as our own supercluster. The Big Rip scenario described by Oni is a "what if" scenario, where the dark energy component actually grows as the Universe expands, creating a divergent expansion. This would tear apart not just galaxies but eventually even nucleons! Interesting but pure speculation at this stage. The dark energy component could well decrease with expansion, such that gravitational attraction once again dominates, and the Universe could well collapse (given sufficient density.)
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riVeRraT Member (Idle past 445 days) Posts: 5788 From: NY USA Joined: |
onfire writes: The redshift occurs with distant galaxies, not individual stars. Especially not anything in our Local Group - which is what I'm assuming you were visibly looking at. I could find my old log, but I believe I looked at a few galaxies through my scope. I remember, m-101, m-31, m81 and 82, I think m-105.
onfire writes: Furthermore, both redshift and blueshift aren't a visible phenomenon, it's is a measurment of the frequency of the emited light. Yes, that I knew. Like measuring Doppler with sound equipment.
cavediver writes: Hi RR - as Taq has already explained, stars within our Galaxy are in orbit about the Galactic core, and this massively dominates any effect of the Universal expansion. I think that is wrong? Objects we measure using Hubble's law are only measured relative to us. Everything in our galaxy is moving with us, so universal expansion is undetectable. (I just realized/remembered this)
cavediver writes: Likewise, neighbouring galaxies are far more affected by local gravitational effects than the expansion. You have to look past the Local Group of galaxies to start to see real evidence of the expansion. I think galaxies close to us, are also moving with us, so we can't detect their expansion relative to the universe. If M-33/31 are only 2 million light years away, then it has only separated from us very little compared to the 14 billion light years we have traveled from the center. So it is moving too slowly away from us to measure using Hubble's law.
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onifre Member (Idle past 2980 days) Posts: 4854 From: Dark Side of the Moon Joined: |
I could find my old log, but I believe I looked at a few galaxies through my scope. I remember, m-101, m-31, m81 and 82, I think m-105. No need, I'm sure you did as there are many within our Local Group.
Everything in our galaxy is moving with us, so universal expansion is undetectable. I believe you are getting a few facts confused here, RR. The galaxies within our Local Group are measurable, they show a Blue Shift indicating that they are coming toward us. This is the affect that Cave was talking about due to the Galactic core's gravitational attraction. The Blue Shifting of the galaxies within our Local Group is a measured fact.
So it is moving too slowly away from us to measure using Hubble's law. The galaxies within our Local Group have been measured and are Blue Shifting rather than Red Shifting. PS. If you don't mind could you split the posts and not put both me and cavediver on the same post. He knows a shit load more than I do and I'd hate for him to miss a question that can help both you and I because he may not notice that you replied to him on the post for me, thanks. - Oni Edited by onifre, : No reason given. "I smoke pot. If this bothers anyone, I suggest you look around at the world in which we live and shut your mouth."--Bill Hicks "I never knew there was another option other than to question everything"--Noam Chomsky
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Coragyps Member (Idle past 763 days) Posts: 5553 From: Snyder, Texas, USA Joined: |
The galaxies within are Local Group are measurable, they show a Blue Shift indicating that they are coming toward us. Some of the local group galaxies are blueshifted, but some are redshifted. Since the three big ones, the Milky Way, Andromeda, and Triangulum, are in mutual orbits of some complicated sort, and the little ones are in orbits around the big ones, any particular galaxy can be heading toward us or away in any particular megamillenium. I made that last word up, I think. Local Group - Wikipedia lists 'em - the Leo Dwarf is one that is redshifted.
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onifre Member (Idle past 2980 days) Posts: 4854 From: Dark Side of the Moon Joined: |
Some of the local group galaxies are blueshifted, but some are redshifted. Since the three big ones, the Milky Way, Andromeda, and Triangulum, are in mutual orbits of some complicated sort, and the little ones are in orbits around the big ones, any particular galaxy can be heading toward us or away in any particular megamillenium. Thanks for the correction, Coragyps. I knew I should have looked that up to make sure, but I also knew if I was wrong someone would catch it. So question, is the megamillenial shifting to and from caused by Dark Energy - versus - gravity of the Galactic center/core? As I was reading up I noticed they mentioned Leo I was one of the furthest.
quote: Does it's distance have anything to do with it's red shifting?
I made that last word up, I think. Apparently some Russian (I'm guesing by the letters and movies I've seen) gaming website has the name. Games is the only english word I saw. So it looks like the Russian gaming nerds beat you to that word. - Oni Edited by onifre, : No reason given. "I smoke pot. If this bothers anyone, I suggest you look around at the world in which we live and shut your mouth."--Bill Hicks "I never knew there was another option other than to question everything"--Noam Chomsky
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