How can quasars be so far away from earth?

[Alan McDougall]

I simple cant rap my mind around the fact that some quasars are said to be receding at 6 C and are 14.5 light years from earth.?

 

Please enlighten me?

 

Alan

[Reaper]

Quasars are billions of light years away from Earth first of all. And the reason they are receding so quickly is precisely because they are so far away; Hubble's Law states that the further a galaxy is, the faster it is receding away.

 

As to why there are quasars at that distance in the first place? I'm not quite sure about that one, but if I had to guess, it would probably be because the galaxies are quite young, and are thus much more active.

[Airbrush]

I simple cant rap my mind around the fact that some quasars are said to be receding at 6 C and are 14.5 light years from earth.?

 

Where did you read "receding at 6C"? The furthest quasars were much closer to us than 14.5 (you mean Billion) LY away when their light left them. Objects near the edge of our current visual horizon are not receding that fast. Now the furthest visible quasars and galaxies are about 30 Billion LY away, and they were between 12 and 13 Billion LY away when the light we now see started traveling towards us. The cosmic microwave background is now about 50% further, or about 45 Billion LY away.

 

Maybe someone can resolve this better than I can.

Edited June 6, 2009 by Airbrush

[Martin]

I simple cant rap my mind around the fact that some quasars are said to be receding at 6 C and are 14.5 light years from earth.?

 

Please enlighten me?

 

Alan

 

Reaper and Airbrush gave you about as good an answer as you can get with a question like that.

 

If you want to think about astronomy you have to train yourself to use numbers in a consistent reliable way. Don't confuse 14 with 14 billion. Don't confuse redshift z = 6 with 6c.

 

Don't confusion recession rate with speed. A recession rate is merely the rate that the distance is increasing, it is not the speed that something is moving.

 

If something moves or travels in the ordinary sense then it is going somewhere, it is getting closer to something else. A galaxy is not going anywhere (except for a little trivial local motion it may have within its group).

 

Geometry is dynamic. Distances between stationary objects change. All there is to it. That is what curved spacetime is about---Gnrl Rltvty---you heard about it. It is what causes the geometry around us to be Euclidean and what causes some largescale geometry to not be Euclidean. The Einstein equation decides how geometry acts, and whether or not distances between stationary points will increase or decrease, and what the angles of any particular triangle are going to add up to. You have no right to expect distances not to change.

 

Once you realize that Euclid geometry is not absolute and universal there is nothing to "wrap" your mind around.

 

Google "cosmos calculator". Put in .25 for matter, .75 for cosmo constant, 74 for Hubble rate, and 6 for the redshift.

This will tell you the present distance to a quasar with redshift z = 6. And it will tell you the present recession rate.

 

If you have a source for a quasar receding at rate 6c, I would like to see it. It is possible. But the highest redshifts of quasars I know of are around 6 or 7.

That means the distance to them is increasing at a rate which is about twice the speed of light, not six times.

 

In Dante's Inferno the people who were sloppy about numbers in their mortal lifetime are punished by wearing gasoline-soaked adult diapers which are on fire throughout Eternity. I forget which Canto this is in. Anyway Pagans and Illicit Lovers get off lightly compared with those unfortunate souls. So for heaven's sake reform your ways!

Edited June 6, 2009 by Martin

[Alan McDougall]

Where did you read "receding at 6C"? The furthest quasars were much closer to us than 14.5 (you mean Billion) LY away when their light left them. Objects near the edge of our current visual horizon are not receding that fast. Now the furthest visible quasars and galaxies are about 30 Billion LY away, and they were between 12 and 13 Billion LY away when the light we now see started traveling towards us. The cosmic microwave background is now about 50% further, or about 45 Billion LY away.

 

Maybe someone can resolve this better than I can.

 

Receding from each other at greater than the speed of light, because they are embedded into the fabric of the universe that is expanding and accelerating at near c

[Martin]

I simple cant rap my mind around the fact that some quasars are said to be...

 

Please enlighten me?

 

Alan

 

Receding from each other at greater than the speed of light...

 

Alan, how are you coming with the business of wrapping mind around features of the astro standard model?

 

Have you tried using one of the online calculators to convert redshift yet?

 

The redshift is the primary data. That is what they measure. The highest redshift observed objects are the farthest away, and they are the ones whose distance from us is increasing fastest.

 

The highest redshift I know of being observed is that of the cosmic microwave background z = 1090.

 

The next highest that I know of is a Gamma Ray Burst (GRB) observed in April 2009. z is around 8. One team said z = 8.2 and another team said at least 7.8.

 

It might help you orient yourself if you simply got some practice converting a redshift like z = 8 into the standard model distance estimate.

 

Is there any reason you want to stick with quasars? Quasars do not hold the distance record. As I recall the furthest quasar is something like z = 6.5, roughly. So the GRB I am talking about is much further away. It's up to you. Pick some redshift you like, whether of a Gamma Ray Burst or of a quasar, and convert it to distance and recession rate. Get hands-on familiarity with this.

 

Here's a NASA report about the burst:

http://www.nasa.gov/mission_pages/swift/bursts/cosmic_record.html

 

Redshifts are your friend. They are what is actually measured, in most cases. They are nice moderate numbers, like 1.4 or 6.5.

They don't have confusing units like "billion light years" or "mega parsecs" tacked on to them. Once you realize that you can always convert a redshift to a distance if you want to, then you can be much more comfortable using redshifts as a handle on distance and other things. It's the way to go.

 

The pros found that out a long time ago. Over on campus in the astronomy building they typically are not talking about billions of lightyears, they are more apt to be talking in terms of redshift number. It's more convenient. You might convert to billions of lightyears when a TV camera is present or a reporter from some magazine is interviewing you.

 

Redshift 1.4 means that distances increased a factor of 2.4 while the light was on its way to us. Distances more than doubled. Redshift 8 means that distances increased 9-fold.

 

Is this helping or making it more difficult?

 

To convert a redshift, google "cosmos calculator", prime the calculator by typing in .25 for matter, .75 for cosmo-constant, 74 for Hubble rate, and then put in your redshift like 1.4 or 8, and go.

[Alan McDougall]

Thanks guys you have given me much to think about, I hope to return with an intelligent response

 

Alan

[Martin]

Thanks guys you have given me much to think about, I hope to return with an intelligent response

 

I'm sure you will! Here's the link to cosmos calculator, to save you trouble googling it

 

http://www.uni.edu/morgans/ajjar/Cosmology/cosmos.html

 

If it gets cranky please tell me. When you start a session you go to the boxes over on the left margin and put in .25 for matter, .75 for cosm.const., and 74 for Hubble rate. Those are the latest values of the three key parameters.

 

After that you can put in whatever redshift, and try a whole bunch of redshifts one after the other, if you choose.

 

Just as a check, once you have primed it with the three parameters, if you put in redshift 8, then you should get out that the distance now is 29 billion lightyears (or 29.39 but I rounded off) and the recession "speed" or more correctly the current expansion rate of that distance, is 2.22 c.

If you don't get those numbers please let us know. It's basic like knowing how to swim when you are around the pool, so I want to make sure it is working properly for you.

[Alan McDougall]

I'm sure you will! Here's the link to cosmos calculator, to save you trouble googling it

 

http://www.uni.edu/morgans/ajjar/Cosmology/cosmos.html

 

If it gets cranky please tell me. When you start a session you go to the boxes over on the left margin and put in .25 for matter, .75 for cosm.const., and 74 for Hubble rate. Those are the latest values of the three key parameters.

 

After that you can put in whatever redshift, and try a whole bunch of redshifts one after the other, if you choose.

 

Just as a check, once you have primed it with the three parameters, if you put in redshift 8, then you should get out that the distance now is 29 billion lightyears (or 29.39 but I rounded off) and the recession "speed" or more correctly the current expansion rate of that distance, is 2.22 c.

If you don't get those numbers please let us know. It's basic like knowing how to swim when you are around the pool, so I want to make sure it is working properly for you.

 

Thank you Martin, I looked it up I have some knowledge about asrtronomy and astrophysics because my hobby is that of an amateur astronomer

 

If we took the instrument below and put one point on the earth and the other on the receding quasar would the distance equate to actual according to red shift etc etc

 

 

 

http://www.fromoldbooks.org/Scranton-OrnamentalDesign-VolI/pages/011-drawing-a-circle-with-the-compasses/011-drawing-a-circle-with-the-

 

compasses-q75-447x500.jpghttp://www.fromoldbooks.org/Scranton-OrnamentalDesign-VolI/pages/011-drawing-a-circle-with-the-compasses/011-drawing-a-circle-with-the-compasses-q75-447x500.jpg

[Martin]

I think you are probably joking with your picture of a solid metal measuring instrument. In case there is some touch of sincerity in the question, I will answer seriously: a piece of metal that travels near the speed of light relative Background will be melted and/or vaporized by the dopplershifted background radiation

 

If, in sheer fantasy, by some miracle you could obtain a rigid measuring rod, 13 billion lightyears in length, with one end somehow anchored in this galaxy (so that it would move only negligibly relative background)

then assuming rod inelastic--unable to stretch--the other end would necessarily be moving at near c relative background, and would melt.

 

Solid measuring instruments above a certain size will self-destruct in the universe as we know it.

 

Besides the quasars we have been talking about are not even that close, they are more like 20 billion, rather than 13 billion. And a 13 billion lightyear rod is already a physical impossibility.

 

So your thought experiment does not work.

 

Special rel would prevent you from anchoring to anything that was already out there because to do so would require accelerating the object (star, galaxy) towards us at near the speed of light.

[Alan McDougall]

I think you are probably joking with your picture of a solid metal measuring instrument. In case there is some touch of sincerity in the question, I will answer seriously: a piece of metal that travels near the speed of light relative Background will be melted and/or vaporized by the dopplershifted background radiation

 

If, in sheer fantasy, by some miracle you could obtain a rigid measuring rod, 13 billion lightyears in length, with one end somehow anchored in this galaxy (so that it would move only negligibly relative background)

then assuming rod inelastic--unable to stretch--the other end would necessarily be moving at near c relative background, and would melt.

 

Solid measuring instruments above a certain size will self-destruct in the universe as we know it.

 

Besides the quasars we have been talking about are not even that close, they are more like 20 billion, rather than 13 billion. And a 13 billion lightyear rod is already a physical impossibility.

 

So your thought experiment does not work.

 

Special rel would prevent you from anchoring to anything that was already out there because to do so would require accelerating the object (star, galaxy) towards us at near the speed of light.

 

Yeh I am!! but the question remains is the quasar really the distance "the red shift indicates" at the "exact moment" measured by out best astronomical telescopes etc?

 

The earth is some 5.9 billion years old , so for us to see the quasar it must have radiated energy for at least as long or it would/could have vanished into a black hole by now.

 

You might be surprised how many people have difficulty understanding this question and its solution

 

It must be somewhere else to my limited mind!!

Edited June 8, 2009 by Alan McDougall

[Martin]

Yeh I am!! but the question remains is the quasar really the distance "the red shift indicates" at the "exact moment" measured by out best astronomical telescopes etc?

 

It must be somewhere else to my limited mind!!

 

Well we've gotten to a place of just repeating incomprehension so perhaps I'll say farewell. We all have very limited minds, and scientists have been trying to punch a hole in Gen Rel ever since 1915 when it was published. They like to test and if possible falsify theories, because if you catch a theory out then you get to construct an improved one. And so far Gen Rel has passed all the tests with flying colors (6 decimals precision etc etc.)

 

GR is a theory of geometry---it is also the prevailing picture of how gravity works---but first and foremost it says how geometry changes. And cosmology is about the geometry of the U as a whole, and it derives from GR.

 

So the answer to your question is that YES as far as we can tell, and there are a lot of very skeptical professionals whose job it is to doubt and test theories who would love to poke a hole or catch cosmology out. But they haven't yet. whenever someone thinks he has and goes to a reporter at New Scientist and gets interviewed and makes a big fuss, well 6 months later it is usually found faulty or explained, and it goes away.

 

The only challenge I see making steady progress is Loop-style quantum geometry and the associated quantum cosmology derived from it. That is for now. A new approach could appear next year. But for now that is about it, and Loop has a long way to go.

 

So if you are fated not to personally understand the current work going on in cosmology, don't worry. Nobody can be informed about everything there is to know. The people whose job it is are extremely skeptical and scrutinizing and checking all the time. And the answer is yes, you can rely on the standard cosmo model---the things are currently at about the distances the calculator says. The model fits observational data remarkably well.

[Alan McDougall]

Well we've gotten to a place of just repeating incomprehension so perhaps I'll say farewell. We all have very limited minds, and scientists have been trying to punch a hole in Gen Rel ever since 1915 when it was published. They like to test and if possible falsify theories, because if you catch a theory out then you get to construct an improved one. And so far Gen Rel has passed all the tests with flying colors (6 decimals precision etc etc.)

 

GR is a theory of geometry---it is also the prevailing picture of how gravity works---but first and foremost it says how geometry changes. And cosmology is about the geometry of the U as a whole, and it derives from GR.

 

So the answer to your question is that YES as far as we can tell, and there are a lot of very skeptical professionals whose job it is to doubt and test theories who would love to poke a hole or catch cosmology out. But they haven't yet. whenever someone thinks he has and goes to a reporter at New Scientist and gets interviewed and makes a big fuss, well 6 months later it is usually found faulty or explained, and it goes away.

 

The only challenge I see making steady progress is Loop-style quantum geometry and the associated quantum cosmology derived from it. That is for now. A new approach could appear next year. But for now that is about it, and Loop has a long way to go.

 

So if you are fated not to personally understand the current work going on in cosmology, don't worry. Nobody can be informed about everything there is to know. The people whose job it is are extremely skeptical and scrutinizing and checking all the time. And the answer is yes, you can rely on the standard cosmo model---the things are currently at about the distances the calculator says. The model fits observational data remarkably well.

 

Farewell so soon you have hardly got to know me, if you hang around you might find me an interesting old gripe

 

http://www.scienceblog.com/cms/three_distant_quasars_found_at_edge_of_the_universe

 

During the past year, members of the Sloan Digital Sky Survey team obtained further spectra of the quasars with the 10-meter (400 inch) Keck Observatory in Hawaii, the 9.2-meter (368 inch) Hobby-Eberly telescope in west Texas and the 3.5-meter (158 inch) Calar Alto Observatory telescope in southern Spain.

 

"The spectra show unambiguously that the three quasars have redshifts of 6.4, 6.2 and 6.1," said Don Schneider, a collaborating Sky Survey astronomer at Pennsylvania State University. "Only one quasar had been previously known to have a redshift larger than six." The previous record-holder, at redshift of 6.28, was discovered in 2001 by the Sloan Digital Sky Survey consortium.

Cosmologist Robert Becker of the University of California-Davis and the Lawrence Livermore National Laboratory, noted that "the Sloan Survey has now discovered the seven most distant known quasars."

 

"The Sloan Survey has generated a sample of quasars which stretches through all of cosmic time, from 800 million years after the Big Bang to the present," said James Gunn of Princeton University, and the project scientist of the Sloan Survey. "These data will be invaluable for the next major effort of the Sloan Survey quasar team, namely to characterize the evolution of quasars from their formation to the present."

(A complete list of people contributing to the discoveries of new, more distant quasars is posted on the NEWS Section of the Sloan Digital Sky Survey web site at

 

Are those quasars we see in our scopes still there??

Edited June 8, 2009 by Alan McDougall

[Martin]

"The spectra show unambiguously that the three quasars have redshifts of 6.4, 6.2 and 6.1," said Don Schneider,

Are those quasars we see in our scopes still there??

 

Those were results from 2002. Those are not the farthest redshift quasars. Ones with larger redshifts have been found.

 

The matter should still be there, where it always was*. Why would it have moved? The individual motion of galaxies relative background tend to be fairly trivial, can usually be neglected.

 

As time passes matter takes different form and evolves. A cloud becomes a star, a star maybe explode and become a cloud and a neutronstar etc. Presumably quasars too, have a life cycle.

 

So the matter may look different but that which was a quasar when it sent us the light, however it looks now, must still be there.

 

* in the comoving coordinates that cosmologists most commonly use. The comoving distance is what the calculator normally gives. Comoving distance is a handy way to locate things because it doesn't change as U expands. If you know the balloon model it is like the latitude longitude of a spot on the balloon which doesn't change as the balloon expands.

 

If you want to know the actual distance from us at times in the life of some quasar (say with redshift 6.1) then just use the calculator as I suggested. It will tell you how far from Milky the quasar matter was then when it sent the light we see. And it will tell how far it is now (when for all I know it may have burnt out, or look different due to some kind of aging.)

Edited June 8, 2009 by Martin

[Alan McDougall]

Those were results from 2002. Those are not the farthest redshift quasars. Ones with larger redshifts have been found.

 

The matter should still be there, where it always was*. Why would it have moved? The individual motion of galaxies relative background tend to be fairly trivial, can usually be neglected.

 

As time passes matter takes different form and evolves. A cloud becomes a star, a star maybe explode and become a cloud and a neutronstar etc. Presumably quasars too, have a life cycle.

 

So the matter may look different but that which was a quasar when it sent us the light, however it looks now, must still be there.

 

* in the comoving coordinates that cosmologists most commonly use. The comoving distance is what the calculator normally gives. Comoving distance is a handy way to locate things because it doesn't change as U expands. If you know the balloon model it is like the latitude longitude of a spot on the balloon which doesn't change as the balloon expands.

 

If you want to know the actual distance from us at times in the life of some quasar (say with redshift 6.1) then just use the calculator as I suggested. It will tell you how far from Milky the quasar matter was then when it sent the light we see. And it will tell how far it is now (when for all I know it may have burnt out, or look different due to some kind of aging.)

 

I know that that matter come energy will never vanish from the universe if we discount a black hole, what I meant the far away quasar is right before the near of the moment of the big bang (of course in cosmological terms) thus we see it as it was when it was "young" and maybe this "old quasar" has vanished as a composite object

 

What are we doing out here in the grand somewhere looking at an object that is no longer??

 

By the way my physics goes only up to that needed for my Mechanical Engineering Degree