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Nigel G

Is our Universe 13.7 billion years old ? I'm not quite convinced

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.....and remember that the 13.8 bn years is as far as we can go back by collecting light, and that there are many thousands of years of the Universe before that, when it was opaque.

Doug.

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12 hours ago, Nigel G said:

In my mind things don't quite add up.

Hubble deep space image has galaxy's at 13 billion light years , ok I got it,  experts say this image would be much the same any direction hubble pointed. 

OK so if hubble turned 180° from the deep space image and done another million second image you would see galaxy's at 13 billion light years.

surely that makes our Universe at least 26 billion years old ?

Your thoughts please.

Nige.

Nope.  A light year is a unit of distance NOT time.  So you should be saying "surely that makes our Universe at least 26 billion light years big ?".  Which would be true provided we remember the "at least" in that statement.

(And do correct me if I've misunderstood anything - I'd always prefer to be corrected that be allowed to maintain erroneous understandings)

Ian

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I spent a long time trying to understand this.

The universe is much bigger than the observable universe - it may even be infinite. There are two reasons why it is bigger in size than 2 x its age in light years.

  1. Expansion cause it to grow huge at much more than the speed of light for a brief time at the beginning. This put some areas so far apart they will never be able to see each other.
  2. More profoundly and what I found hard to understand the universe did NOT start as a POINT. It may even have been infinite from the start, just with everything closer together. Boggled? I am...
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So.... 1 earth year after the big bang the universe is at least 2 light years across?  We ( The milky way )may be near the edge or the center , somewhere in the universe, we can only see light from the big bang 13.7bln years ago as there was no light before however there are bits of the universe that we can't see because it's moving away faster than light travels until gravity takes over an starts to collapse the universe if it ever does. Therefore any direction you will see 13.7 billion years + 1 more day into the past. 

Which makes travelling faster than light speed possible. This also brings up another question ☺

If I  was on a starship travelling to Andromida as I'm sure it's less than 13 billion ly away ?, my speed was warp 1.000000001 just over light speed. I was at the helm my partner was walking up behind me, if I looked would I see her coming ??

PS. I know it would take quite a while to get to Andromida. 

Nige.

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1 hour ago, cloudsweeper said:

 by collecting light, /

many thousands of years of the Universe before that, when it was opaque.

Because of your green emphasis I guess you are waiting for someone to jump in to say,,,  that is why we need LIGO and gravity wave telescopes :) 

Yes, approx 300 thousand I think is best guess for the interval before the Time of Last Scattering.

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13 minutes ago, Nigel G said:

This also brings up another question ☺ Oh ho !!!

 warp 1.000000001 just over light speed. // PS. I know it would take quite a while to get to Andromida. 

at 'just over' you would arrive there before you left.

Edit PS  at exactly the speed of light it would take you exactly no time at all to get there.

PPS but we that you left behind would have long white beards and would be very very old :)

 

Edited by SilverAstro
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7 minutes ago, SilverAstro said:

at 'just over' you would arrive there before you left.

Edit PS  at exactly the speed of light it would take you exactly no time at all to get there.

PPS but we that you left behind would have long white beards and would be very very old :)

 

?but would I see my Mrs behind me or would she just appear next to me?  Would she see me before I got into the driving seat although I  have  been  there for a few hours. 

I suppose what I'm trying to work out is could she slap me round the face before I got the slap ☺ 

Seriously though it's mind boggling but so interesting. I love having time to think.

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16 minutes ago, SilverAstro said:

at 'just over' you would arrive there before you left.

Edit PS  at exactly the speed of light it would take you exactly no time at all to get there.

PPS but we that you left behind would have long white beards and would be very very old :)

 

Time stops at light speed?

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20 minutes ago, SilverAstro said:

at 'just over' you would arrive there before you left.

Edit PS  at exactly the speed of light it would take you exactly no time at all to get there.

PPS but we that you left behind would have long white beards and would be very very old :)

 

Sure I would arrive at Andromida before I left from Earths point of view,  it would still take 2.5 million years to get there, if I looked back with my telescope and very long beard you would all be the same age or slightly younger and I would be getting ready to launch. 

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3 minutes ago, Nigel G said:

Time stops at light speed?

Ah well ,,  it all depends ! Your generalised question has no meaning in Albert's physics, there is only your time, my time and him-over-there's time and they are all different. Apart from the fact that we can not travel at light speed it did not stop Albert and his gedanken which led him to you-know-what and the conclusion that a photon (anthropomorphically) experiences no time at all even though we see photons taking a long time to arrive from Andromeda.

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30 minutes ago, Nigel G said:

Time stops at light speed?

Flee the earth at the speed of light and look back from Andromeda. Assuming your scope is big enough you will see the clocks on earth still show the time you left. But you will be 2 million years older.

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Might be confusing age and size. The universe is more then 13.8 Bn light years in size, there are bits that are outside what we can see.

The age comes from what we can see, if we contract it back we get a point (the BB) and that 13.8 bn years ago.

So the size is more then we can see and owing to Hubble constant and so the Hubble radius what we see is limited in distance since space time between us and anything the other side of the Hubble Raduius is receeding from us at greater then the speed of light - the object is however not moving faster then light - the "nothing" between us is.

Quote

can one infinity be larger than another, yes it can

Easy to follow:

You have all the even integer numbers 2, 4, 6, 8, etc up to infinity.

You have all the odd integer numbers 1, 3, 5, 7, 9, etc up to infinity

How many integer numbers 1, 2, 3, 4, 5, 6, 7 etc have you?

One or two infinities?

Edited by ronin
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33 minutes ago, Nigel G said:

Sure I would arrive at Andromida before I left from Earths point of view,  it would still take 2.5 million years to get there, Nooooo !if I looked back with my telescope and very long beard you would all be the same age or slightly younger and I would be getting ready to launch. 

No it would not take you 2.5my, you would get there instantly, it is us left behind that would see you taking 2.5my to get there. in fact it gets worsly boggling, if you could travel like a photon ( you cant which is why these discussions always descend into sillyness !) if - then you can travel to any part of the universe instantly, the trouble is you wouldnt know where you had arrived nor when until someone or something there intercepted you. To go any further we would have to start talking about fields and manifolds and things ( and I dont mean car manifolds ! )

 

Edited by SilverAstro

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14 hours ago, Nigel G said:

In my mind things don't quite add up.

Hubble deep space image has galaxy's at 13 billion light years , ok I got it,  experts say this image would be much the same any direction hubble pointed. 

OK so if hubble turned 180° from the deep space image and done another million second image you would see galaxy's at 13 billion light years.

surely that makes our Universe at least 26 billion years old ?

Your thoughts please.

Nige.

We can (theoretically) see out to a certain distance, because light has only had so long to travel since the Big Bang. This is the radius of our observable universe.

You would think that in a universe that is x billion years old the observable radius would be x billion light years. This is not so, the reason being the cosmological expansion that goes on while the light is travelling. Instead, the radius turns out to be bigger than you would intuitively expect. How much bigger depends on the exact details of the expansion (in particular, whether there is a non-zero cosmological constant).

Quote from Wikipedia article "Observable Universe":

The best estimate of the age of the universe as of 2015 is 13.799±0.021 billion years[5] but due to the expansion of space humans are observing objects that were originally much closer but are now considerably farther away (as defined in terms of cosmological proper distance, which is equal to the comoving distance at the present time) than a static 13.8 billion light-years distance.[8] It is estimated that the diameter of the observable universe is about 28.5 gigaparsecs (93 billion light-years, 8.8×1026 metres or 5.5×1023 miles),[9] putting the edge of the observable universe at about 46.5 billion light-years away.[10][11]

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

So if the Hubble Space Telescope is pointing at a galaxy that is 13 billion years old, then the place where that light originated is now maybe, say, about 40 billion light years away. If the telescope is turned round to look at a 13 billion year old galaxy in the opposite direction, then again, the place where that light originated is now maybe about 40 billion light years away. This does not contradict the universe being 13.8 billion years old.

 

Edited by acey
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5 minutes ago, acey said:

It is estimated  //  at about 46.5 billion light-years away.[10][11]

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

 

Without checking all the refs ( better man than I Gungadin  and lunch needs preparing !) were they before or after we discovered the accelerating expansion ? which we still have not quantified with high precision

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6 minutes ago, SilverAstro said:

before or after we discovered the accelerating expansion ? which we still have not quantified with high precision

I should have said " ,, expansion and dark energy which ,, "   :)

 

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37 minutes ago, ronin said:

Might be confusing age and size. The universe is more then 13.8 Bn light years in size, there are bits that are outside what we can see.

The age comes from what we can see, if we contract it back we get a point (the BB) and that 13.8 bn years ago.

So the size is more then we can see and owing to Hubble constant and so the Hubble radius what we see is limited in distance since space time between us and anything the other side of the Hubble Raduius is receeding from us at greater then the speed of light - the object is however not moving faster then light - the "nothing" between us is.

Easy to follow:

You have all the even integer numbers 2, 4, 6, 8, etc up to infinity.

You have all the odd integer numbers 1, 3, 5, 7, 9, etc up to infinity

How many integer numbers 1, 2, 3, 4, 5, 6, 7 etc have you?

One or two infinities?

One and it is the same infinity as the other two. However, there are larger ones

Regards Andrew

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47 minutes ago, ronin said:

Hubble Raduius is receeding from us

Nice typo, very good :)    I dunno I dont understand these things cos I'm just an amoeba, you'll have to ask my cousin Andrew who has evolved into a radulus  :):)

Edited by SilverAstro
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5 hours ago, SilverAstro said:

No it would not take you 2.5my, you would get there instantly, it is us left behind that would see you taking 2.5my to get there. in fact it gets worsly boggling, if you could travel like a photon ( you cant which is why these discussions always descend into sillyness !) if - then you can travel to any part of the universe instantly, the trouble is you wouldnt know where you had arrived nor when until someone or something there intercepted you. To go any further we would have to start talking about fields and manifolds and things ( and I dont mean car manifolds ! )

 

I disagree,  Andromida is 2.5 million ish light  years away ok. Therefore travelling at light speed would take 2.5 million years correct?  

Also if I  was at just over L S you wouldn't see me as I'm travelling faster away from you than my light travelling towards you. Surely. 

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I hope you all had a good day :) ? Following on from the Jura/Talisker/etc discussions of last night y'all be pleased to know that today I was given a bottle of Grant's ( ok blended but hey, gift horses etc !) so it can only get better/worse (strike out as you see fit :) )

To illustrate the daftness of this journey to Andromeda under Albert's regime : as you accelerate towards light speed you will become incredibly large, extraordinarily thin, vastly massive and bork every planet and star anywhere near your geodesic !!

oh we are about to cross in the post again !

" Therefore travelling at light speed would take 2.5 million years correct? "

Correct for me, not for you, our rates of times are different,,,   it would as far as I would clock it here on earth left behind, but for you on the ship it would only take a blink of an eye ,see the Twins Paradox    

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30 minutes ago, Nigel G said:

Therefore travelling at light speed would take 2.5 million years correct?  

21 minutes ago, SilverAstro said:

" Therefore travelling at light speed would take 2.5 million years correct? "

Correct for me, not for you, our rates of times are different,,,   it would as far as I would clock it here on earth left behind, but for you on the ship it would only take a blink of an eye ,see the Twins Paradox    

Actually, it is even sillier than that :

You leave here at nearly the speed of light and moments (see what I said earlier about photons experiencing no time ), later as far as you are concerned, arrive at Andromeda, you then send a radio signal back this way to say " I've arrived". I will get that great bit of news a tad over 9million years from when you said goodby.

 

 

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23 minutes ago, SilverAstro said:

You leave here at nearly the speed of light and moments (see what I said earlier about photons experiencing no time ), later as far as you are concerned, arrive at Andromeda

If we could do this on the M1 it would go a long way to solving the problem of kids sitting in the back asking "are we there yet"? :smile:

 

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I have always had a problem with the speed of light in that speed is not an absolute rather than a function of d/t we know distance ie  space moves or expands at any speed so how can we be sure of anything, I will stick to my view that the universe is smaller than an atom and everything else is just an illusion/hologram.

Alan 

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46 minutes ago, Alien 13 said:

will stick to my view that the universe is smaller than an atom and everything else is just an illusion/hologram.

Very like one of my troubling nightmares : how do we know that the universe is expanding, perhaps it us and our measuring devices that are getting smaller ?

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1 hour ago, SilverAstro said:

Actually, it is even sillier than that :

You leave here at nearly the speed of light and moments (see what I said earlier about photons experiencing no time ), later as far as you are concerned, arrive at Andromeda, you then send a radio signal back this way to say " I've arrived". I will get that great bit of news a tad over 9million years from when you said goodby.

 

 

Are the photons of light from Andromeda taking 2.5 million years to get here? Or are they instant, are we not seeing it as it was 2.5 m y ago. 

This one has me slightly confused. :happy6: Must be time for a Jura 

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