Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Platonic shapes and the Universe's best telescope

  • Please log in to reply
12 replies to this topic

#1 rxeddie2003

rxeddie2003

    Vostok 1

  • *****
  • topic starter
  • Posts: 133
  • Joined: 11 Apr 2016
  • Loc: Arcadia, CA

Posted 22 September 2019 - 07:45 PM

One could argue the most perfect sphere found in the universe is perhaps a neutron star or the singularity of a black hole.  A pulsar is perhaps the most accurate clock.  And finally, the most powerful and most perfect optical lens in the universe is a black hole.



#2 B 26354

B 26354

    Viking 1

  • -----
  • Posts: 863
  • Joined: 05 Jan 2017
  • Loc: Southern California semi-desert (NELM mag 5.3)

Posted 22 September 2019 - 07:55 PM

Well... I'm no astrophysicist... but it strikes me that a super-high-rotating essentially-fluid object is definitely not going to be spherical.



#3 areyoukiddingme

areyoukiddingme

    Skylab

  • *****
  • Posts: 4371
  • Joined: 18 Nov 2012

Posted 22 September 2019 - 08:07 PM

Why "argue". There should be clear data on regularity of pulsars. I'm going to guess that aren't as good as a quantum mechanical clock. Apparently getting to +/- 1s every 5B years. Pretty decent.



#4 rxeddie2003

rxeddie2003

    Vostok 1

  • *****
  • topic starter
  • Posts: 133
  • Joined: 11 Apr 2016
  • Loc: Arcadia, CA

Posted 22 September 2019 - 08:07 PM

I heard it is debated whether orz neutron stars are mostly solid or liquid; however, I thought  the extreme gravity will shape it to a highly spherical shape.  Are there any astronomers or physicists that can chime in?



#5 DaveC2042

DaveC2042

    Vostok 1

  • -----
  • Posts: 140
  • Joined: 18 Jul 2018
  • Loc: Sydney, Australia

Posted 23 September 2019 - 05:00 AM

Don't underestimate the extreme angular momentum a gravitationally collapsed object will have, to act against the extreme gravity.

There are neutron stars out there rotating a thousand times a second.

I think that's likely to be the norm for them and black holes, just on the grounds that zero angular momentum for a pre-stellar nebula is vanishingly unlikely, and the gravitational collapse will always amplify it enormously.

So I suspect oblateness is pretty universal and none of these things are perfect spheres, or even close.

Of course I'm not really an expert. Anyone know more?

#6 llanitedave

llanitedave

    Humble Megalomaniac

  • *****
  • Posts: 29338
  • Joined: 25 Sep 2005
  • Loc: Amargosa Valley, NV, USA

Posted 23 September 2019 - 09:44 AM

Don't underestimate the extreme angular momentum a gravitationally collapsed object will have, to act against the extreme gravity.

There are neutron stars out there rotating a thousand times a second.

I think that's likely to be the norm for them and black holes, just on the grounds that zero angular momentum for a pre-stellar nebula is vanishingly unlikely, and the gravitational collapse will always amplify it enormously.

So I suspect oblateness is pretty universal and none of these things are perfect spheres, or even close.

Of course I'm not really an expert. Anyone know more?

Under the right conditions, magnetic or tidal forces can slow that rotation down.  Whether it can do it effectively enough to make the object spherical in the lifetime of the universe, I couldn't say.



#7 rxeddie2003

rxeddie2003

    Vostok 1

  • *****
  • topic starter
  • Posts: 133
  • Joined: 11 Apr 2016
  • Loc: Arcadia, CA

Posted 23 September 2019 - 10:59 AM

My random thought was about this was that under extreme conditions such was the gravitational pulls of black holes and neutron stars, as well as the collision of the LHC, material objects appears to sometimes become idealized, Platonic, and ultimately mathematical objects.  So far all the recent breakthroughs, such EHT's photo of the blackhole, the detection of gravitational waves from LIGO, or the discovery of the Higgs particle from the LHC, only confirm exactly what the mathematical models predicted.  The surprising things about them were that there were no surprises.    



#8 Inkswitch

Inkswitch

    Ranger 4

  • *****
  • Posts: 305
  • Joined: 09 Nov 2003
  • Loc: Walhonding, OH USA

Posted 23 September 2019 - 01:16 PM

Regarding the Platonic solids:  I have read many a book on how we know what we know about the universe.  If I distill them in my mind and take a high level view it comes out like this:  Back in the day a bunch of guys examined the universe.  These guys were called geometers because they had a belief in the perfection of Platonic solids and geometry in general.  They came up with convoluted schemes to explain the motion of the stars and the seven celestial bodies that didn't follow the usual rules.  These schemes were based on spheres and geometry and for some reason crystal.  You likely know the middle part of the story, Copernicus, Kepler, Newton.  By then we understood that geometry was more or less out the window and the new force called gravity held sway.  Newton didn't explain everything, uh Mercury?, so along comes Einstein (and predecessors) and he says "Good news people, geometry is back in vogue".  So in a way Plato was right all along.

 

Therefore, while you may be unable to make a perfect clock or a perfect telescope using a neutron star, keep thinking along these lines.  You can be assured that Plato rests easy since general relativity came out.



#9 goodricke1

goodricke1

    Viking 1

  • -----
  • Posts: 558
  • Joined: 18 May 2013
  • Loc: Ireland

Posted 23 September 2019 - 02:45 PM

Don't underestimate the extreme angular momentum a gravitationally collapsed object will have, to act against the extreme gravity.

There are neutron stars out there rotating a thousand times a second.

I think that's likely to be the norm for them and black holes, just on the grounds that zero angular momentum for a pre-stellar nebula is vanishingly unlikely, and the gravitational collapse will always amplify it enormously.

So I suspect oblateness is pretty universal and none of these things are perfect spheres, or even close.

Of course I'm not really an expert. Anyone know more?

 

A slow-spinner is the roundest object discovered to date -

 

https://www.sciencea...-known-universe



#10 llanitedave

llanitedave

    Humble Megalomaniac

  • *****
  • Posts: 29338
  • Joined: 25 Sep 2005
  • Loc: Amargosa Valley, NV, USA

Posted 23 September 2019 - 02:49 PM

Ellipses and oblate spheroids are geometry too.


  • Inkswitch likes this

#11 DaveC2042

DaveC2042

    Vostok 1

  • -----
  • Posts: 140
  • Joined: 18 Jul 2018
  • Loc: Sydney, Australia

Posted 23 September 2019 - 06:08 PM

A slow-spinner is the roundest object discovered to date -

 

https://www.sciencea...-known-universe

That is fascinating, thanks.  But it is still spinning, albeit slowly, and it so isn't a perfect sphere, and the distortion is small, but large enough we can observe and measure it.


  • B 26354 likes this

#12 EJN

EJN

    Skylab

  • *****
  • Posts: 4397
  • Joined: 01 Nov 2005
  • Loc: Between what is and what's not there

Posted 23 September 2019 - 09:25 PM

One could argue the most perfect sphere found in the universe is perhaps a neutron star or the singularity of a black hole.

 

The singularity of a rotating black hole described by the Kerr metric is a ring. Just sayin'

 

 

 

 

 

And finally, the most powerful and most perfect optical lens in the universe is a black hole.

 

This is quite untrue, in the geometry of spacetime a gravitational lens does not have a focal point,

but a focal line perpendicular to the gravitational lensing object.

 

An analogy to conventional optics would be a lens with varying refractive index, higher at

the middle and lower at the edges. Not very useful.

 

 

However, a gravitational lens mated with a fluorite or FPL-53 element is a different story... yay.gif


Edited by EJN, 23 September 2019 - 10:19 PM.

  • rxeddie2003 and B 26354 like this

#13 rxeddie2003

rxeddie2003

    Vostok 1

  • *****
  • topic starter
  • Posts: 133
  • Joined: 11 Apr 2016
  • Loc: Arcadia, CA

Posted 23 September 2019 - 10:22 PM

You're absolutely right.  The black hole would refract the light and thereby amplify the image only in the focal line.  Also as you indicated the image would be halo-like.  In theory, however, one could reconstruct the original image if you combine the light along this focal line (factoring in the time differences that the light had to traveled)




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics