Please explain how some quasars are so remote

[Alan McDougall]

Hi People,

 

I know that astronomy has estimated that they have picked of light from the very early universe, and some quasars are said to be receding at 6.0 c

or greater than the speed of light relative to us on earth.

 

I can accept that as a truth, but what I cant rap my brain around, how the heck do we on earth see objects from the beginning of time?.

 

When we target our telescopes at these unimaginably distant objects, they might have already ceased to exist.

 

Some Quasars are extremely energetic primordial galaxies living and dying in less than a billion years or so.

 

Our earth is about 5 billion years old and was born some 5 billion years after the creation of the universe.

 

Therefore our telescopes look out at the cosmos 10 billion years after the big bang.

 

But we are supposed to be observing light back from just after the big bang some 0.5 Billion years in fact.

 

Therefore the primordial quasars must have radiated energy into the universe for at least 10 billion years for us to notice it in our optical instruments

 

Or am I wrong and were these very young quasars (now extremely old) slow radiators of energy (to me this must be the case or we simply would not observe them or the calculated age of the universe is wrong)

 

Can you guys help, this is a real puzzle to many people and a simplified explanation would be much appreciated?

 

Regards

 

Alan

[D H]

The speed of light is finite. The light we see now coming from Proxima Centauri was emitted 4.2 years ago. The light we see now from the Andromeda galaxy was emitted 2.5 million years ago. We are seeing further and further into the past as our telescopes gaze ever further into the universe.

[Martin]

Hi People,

 

I know that astronomy has estimated that they have picked of light from the very early universe, and some quasars are said to be receding at 6.0 c

or greater than the speed of light relative to us on earth.

...

 

Alan I hope you proceed little by little and don't try to wrap your brain around too much all at once. Just take small steps and keep asking (that works for me and the students I've known anyway)

 

What DH said is right, so be sure you absorb that.

 

Then about the first thing you said, I don't know of any quasars that are estimated to be receding at 6c or better.

 

So let's get that straight for starters. Where did you get that?

 

Maybe I'm wrong, but I think that figure of 6c is way off. Maybe you could instead be talking about a redshift of 6, so let's get that straight for openers.

 

I'd suggest you learn how to use the Cosmos Calculator. Just google "cosmos calculator"

put in 0.25 for matter, 0.75 for lambda, 74 for hubble and you are ready to convert any redshift to a recession speed, or to a distance if that interests you.

[Alan McDougall]

Alan I hope you proceed little by little and don't try to wrap your brain around too much all at once. Just take small steps and keep asking (that works for me and the students I've known anyway)

 

What DH said is right, so be sure you absorb that.

 

Then about the first thing you said, I don't know of any quasars that are estimated to be receding at 6c or better.

 

So let's get that straight for starters. Where did you get that?

 

Maybe I'm wrong, but I think that figure of 6c is way off. Maybe you could instead be talking about a redshift of 6, so let's get that straight for openers.

 

I'd suggest you learn how to use the Cosmos Calculator. Just google "cosmos calculator"

put in 0.25 for matter, 0.75 for lambda, 74 for hubble and you are ready to convert any redshift to a recession speed, or to a distance if that interests you.

 

Thanks Martin!

 

Yes I was referring to a red shift of 6, if that is correct some quasars are receding relative to earth at greater than the speed of light. Not 6 times c sorry for that!

 

I am/was an amateur astronomer but even so I have difficulty with these enormous time spans and distances.

 

Perhaps if I phrase my dilemma a little differently. If we could use a hypothetical ruler and place it on the earth and the other end on a distant quasar , and the red shift indicated the quasar should be 13.5 billion light years from earth, would our very hypothetical ruler measure it off as 13.5 billion light years also.

 

I know this is a really silly way to approach my question, but all I really want to know if a photon hits or CCT camera on the Hubble telescope with a red shift indicating it left its source 13.5 billion years ago, is that object, the quasar in question, actually that far from the telescope at the exact moment it hit the telescope CCT camera??

 

http://www.solstation.com/x-objects/star2bir.jpg

 

Regards

 

Alan

[swansont]

If space were static, then yes, you could just use d = ct to find the distance or time, given the other. But space is expanding, which renders that analysis incorrect. An object will be further way because of the expansion after the photon was emitted.

[Alan McDougall]

If space were static, then yes, you could just use d = ct to find the distance or time, given the other. But space is expanding, which renders that analysis incorrect. An object will be further way because of the expansion after the photon was emitted.

 

Hi, My question is based on redshift and the expansion of the universe, So if we could somehow measure the distance between the earth and the extremely remote quasar"AT THE SAME INSTANT IT TIME". Would the quasar by exactly where it should be, based on its redshift.

 

My question is easy to resolve if it were based on a steady state static universe, my difficulty is how can we ever know for sure how far an object like a quasars actually is at any moment, from the earth.

 

Can I use another analogy please?

 

A baseball player throws a ball at you and at the same time is running away from you.

 

The quasar from 13.5 billion light years away from you throws a photon at the earth, and also races away from earth like the baseball runs away from the you. but unlike the baseball is receding from you but at almost redshift C.

 

The quasar is embedded in the fabric of space time, space is stretching, as soon as you measure the quasars reshift it is no longer where you thought it was, so where exactly is it at any moment in relation to earth

 

We are in fact looking at a very very ancient object, as it was when it was still extremely young

 

Much like someone taking a photo of me when I was a baby, with the photo only arriving when I am very old indeed at its destination.

 

I might be dead and my ashes thrown into the sea, but the person looking at my photo will think I am still a baby etc.

 

Hows my logic guys?

 

Alan