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

[DRT]

2 hours ago, Nigel G said:

If you bought a puppy 13 years ago  it would be approximately  65 years old.now ☺

For the first two years, a dog year is equal to 10.5 human years. After that, each dog year equals 4 human years. This calculation is based on studies that indicate dogs, except maybe larger breeds, develop more quickly in the first two years of life.

 

Actually, I think you will find that a 13 year old dog is 13 years old. It might be displaying aging characteristics similar to that of a 65 year old human, but it is still 13 years old

 

[cloudsweeper]

But for the first 400,000 years, it was opaque. (The Universe, not the dog.)

Doug.

[Pippy]

15 hours ago, Nigel G said:

develop more quickly in the first two years of life.

I think that applies to most all life forms on planet Earth apart from humans. If you're not ready to survive without mum or dad pretty quickly, you don't survive.

[DRT]

19 minutes ago, Pippy said:

I think that applies to most all life forms on planet Earth apart from humans. If you're not ready to survive without mum or dad pretty quickly, you don't survive.

I'm sure I read somewhere that this is a trade-off that permits humans to have such large brains. We are effectively all born premature so need further physical development to take place outside the womb before we can fend for ourselves. The reason for the premature birth is to ensure we are born before our heads are too big to pass through the birth canal.

[Stub Mandrel]

1 hour ago, DRT said:

I'm sure I read somewhere that this is a trade-off that permits humans to have such large brains. We are effectively all born premature so need further physical development to take place outside the womb before we can fend for ourselves. The reason for the premature birth is to ensure we are born before our heads are too big to pass through the birth canal.

And inextricably linked with adopting a vertical posture, which creates the need for a relatively narrow pelvis.

I wonder if these things create a feedback loop, where extended childhood leads to greater opportunities for cultural development and therefore greater benefits for more brain.

[Mak the Night]

So ... if a cat fires Zeno's Arrow at an orbiting Russian cosmonaut dog will it ever reach the target?

[andrew s]

1 hour ago, Mak the Night said:

So ... if a cat fires Zeno's Arrow at an orbiting Russian cosmonaut dog will it ever reach the target?

Every breath you take / Every step you make / Every bond you break / refutes Zeno's paradox which is why we went from philosophy to  evidence based science.

...but no because cats can't anatomically use bows.

Regards Andrew

 

[SilverAstro]

2 hours ago, andrew s said:

is why we went from philosophy to  evidence based science.

but as a famous philosopher once said " You've got to take time out to smell the roses" (Snoopy)

 

[andrew s]

52 minutes ago, SilverAstro said:

" You've got to take time out to smell the roses" (Snoopy)

Sounds like an experimentalist to me! 

Regards Andrew

[SilverAstro]

As for all this extrapolating backwards to the time of last scattering ( I thought it was more like 300,000y or has that been revised again ?) how do we know that a year was just as long   lasted as long back then as it does now ? Maybe that is why dogs are shrinking ?

@Andrew rekn yur right !

[DRT]

7 minutes ago, SilverAstro said:

Maybe that is why dogs are shrinking ?

My dog is 1kg heavier each time we go to the vet. I think he is working his way towards his own version The Big Bang

 

[SilverAstro]

5 minutes ago, DRT said:

My dog is 1kg heavier each time we go to the vet. I think he is working his way towards his own version The Big Bang

That is cos he is slowing down as he gets older and , , oh hang on that isnt what Albert said is it, hmmmm,  watch out tonight as he come to rest by the fireside, who knows what might happen ? Lorentz&Fitsgerald were right you know, I mean when did you last see a sausage dog ? Maybe the Russians 'did for' them all ?

 

[Pippy]

Time speeds up as more time passes. It's a well proven fact that it's a good fit to an exponential curve, anyone with a sufficient amount of accumulated years will tell you about said fact.

[Stub Mandrel]

37 minutes ago, DRT said:

My dog is 1kg heavier each time we go to the vet. I think he is working his way towards his own version The Big Bang

 

Depends if he a Great Dane or a Yorkie ;-)

Our labs are loosing weight because I'm on a diet - they follow me to the fridge religiously but now I've stopped snacking!

[DRT]

1 minute ago, Stub Mandrel said:

Depends if he a Great Dane or a Yorkie ;-)

Our labs are loosing weight because I'm on a diet - they follow me to the fridge religiously but now I've stopped snacking!

He is a Black Lab / Rottweiler cross. Not a good weight control combination, but lots of fun so he makes time travel quickly

 

[andrew s]

If the universe goes on long enough this thread will return to its original topic - Poincare recurrence theorem.

Regards Andrew

[Alien 13]

29 minutes ago, andrew s said:

If the universe goes on long enough this thread will return to its original topic - Poincare recurrence theorem.

Regards Andrew

Talking of the original topic about the observable universe are there any indications/theory's about the size of the whole universe.

Alan

[SilverAstro]

28 minutes ago, andrew s said:

If the universe goes on long enough this thread will return to its original topic - Poincare recurrence theorem.

Are you sure about that ? /Heisenberg

Entropy would suggest otherwise but you are right to point out that it is a bit entangled.

[DRT]

47 minutes ago, andrew s said:

If the universe goes on long enough this thread will return to its original topic - Poincare recurrence theorem.

Regards Andrew

Sorry, I got thrown off the main sequence by the whole dog aging thing

 

[Dave In Vermont]

I think this is the first time, in SGL anyways, I've seen a thread on acid! 

evaD

[andrew s]

29 minutes ago, SilverAstro said:

Entropy would suggest otherwise

Strangely not! For a classical closed mechanical system it can be shown that it must, in a finite time, return to its original state. There is still a major outstanding problem in deriving the observations of entropy  increase (and more generally classical thermodynamics) from a statistical approach to thermodynamics.

 

29 minutes ago, SilverAstro said:

Are you sure about that ? /Heisenberg

I am in an superposition of being sure and unsure and looking forward to a collapse into a comatose state once I have finished this glass of wine.

Regards Andrew

[andrew s]

44 minutes ago, Alien 13 said:

Talking of the original topic about the observable universe are there any indications/theory's about the size of the whole universe.

Alan

I pinched this from Physics Forums 

The consensus is: if we keep all the assumptions used in describing the observable universe, then the universe as a whole is consistent both with being infinite in extent, and with being finite but very large.

The assumptions concern homogeneity and isotropy, i.e. the cosmological principle. It is perfectly possible for the laws of physics to differ in other, causally disconnected regions of the universe, in which case anything goes. But if we were to assume that they don't change, and everything does look pretty much the same as in our patch of visible universe, then the size is determined by curvature.

Curvature measurements keep narrowing down with consecutive astrometric missions, and seem to zero-in on the flat case. However, by the nature of any and all measurements, it is impossible to obtain a result not burdened with uncertainty, so there will be always a range of possible curvatures indicated, and as a result - a range of sizes (in case of positive curvature). The error bars currently allow for all three of curvature families - open, flat and closed (so, both finite and infinite). However, the current precision lets us estimate the smallest possible radius of the curvature as 205 billion light years (using the PLANCK 2015 results for H0=67.8+/−0.9H0=67.8+/−0.9 and Ω=0.000+/−0.005Ω=0.000+/−0.005.

See here https://www.physicsforums.com/threads/shape-of-the-universe.882702/  for the original. 

Regards Andrew

[SilverAstro]

1 hour ago, Pippy said:

Time speeds up as more time passes. It's a well proven fact that it's a good fit to an exponential curve,

I have long said similar : that the time scale could be logarithmic not linear, that way the problem of the singularity forever recedes further and further into the past and becomes of errr 'little' consequence ! Standard procedure for unfortunate singularities in equations, make them go away or at least renormalise them away.

 

12 minutes ago, andrew s said:

Strangely not! For a classical closed mechanical system it can be shown

Ah yes, however I was chancing my arm and about to jump dogs horses and say " not in the case of a bouncing big bang universe(s)

19 minutes ago, Dave In Vermont said:

 I've seen a thread on acid! 

Shouldnt visit SGL after taking a trip !

[SilverAstro]

15 minutes ago, andrew s said:

Curvature measurements keep narrowing down with consecutive astrometric missions, and seem to zero-in on the flat case.

Yes it is a bit concerning that it is tending to that special case But is it asymptotic to flat or just that we are near the top of the curve, a bit like with high summer ( should we ever get one ! )

[Stub Mandrel]

1 hour ago, Alien 13 said:

Talking of the original topic about the observable universe are there any indications/theory's about the size of the whole universe.

Alan

Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly 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.