Physics Discussion Thread

[sudarshan]

Really saar, that post of UB's that you responded to wasn't even a one-liner, it was a one-worder. Were you really expecting anything different? My sympathies are with you regardless . And yes, I agree with your sentiment above - though I'm sometimes guilty of making such jokes myself.

P.S.: M&M can also be Mahindra & Mahindra. End of OT from me.

[member_27581]

^^ My last OT on this ....but this M&M was the first link out of my search and I kept searching for quite sometime more assuming Matter and motion and what not..thinking UB ji had some posted some UberBrilliant concept..which this Mensa (-120) guy doesnt know.and after all this u get that...

[UlanBatori]

An M&M is essentially

a dense ball of matter with a core of dark energy

Where do u think these Media Physicists get their Models to describe things that no one else can see? Or to listen to the sound of random noise on a badly-tuned radio and say that it is the Gravitational Wrinkling of the Noses of Space and Time from a mere 12 billion years ago. You don't find THAT funny?

There used to be a couple of yaks in Mongolia who drew fabulous Virtual Reality graphics about Space Settlemennts. They had a stock of whiteboard markers, erasers and ballpoint pens which is what they used as models of their rockets fuel tanks, greenhouses, and everything else.

[SSSalvi]

@UlanBatori

Reg 220 GHz source.

I doubt about commercial availability. It is borderline frequency between Microwave and Optical so electronic device design can possible be only be realized by semiconductor process. ( That is MY feeling .. may be totally wrong ).

BTW, where is it's application? ..

[SaiK]

http://www.esa.int/Our_Activities/Space ... es_to_come

can someone tell me this map as seen from where? and where are we?

[SriKumar]

^^Nice, cleanly-worded post, man. way to go.

This is a photographic map clicked (and digitally stitched together) by the space telescope Gaia, launched by Europe. ESA. It is a map of all stars/planets that this space telescope can see (optically). Gaia orbits around the sun between earth and mars. It is about 1.5 million k.m. from earth- but the exact orbit is still not clear to me. Supposedly, it is a very precise mapping of the universe compared to all previous measurements, and it also plots not just the position but also velocity vectors of the stars/planets as they move over time. It is creating a 3D map. It started mapping about 2.5 years ago.
https://en.wikipedia.org/wiki/Gaia_(spacecraft)

[Prem]

https://www.newscientist.com/article/21 ... 1474392663

Quantum teleportation over 7 kilometres of cables smashes record

A new world record for quantum teleportation has been set, bringing quantum communication networks that can stretch between cities a step closer. Two independent teams have transferred quantum information over several kilometres of fibre optic networks.Being able to establish teleportation over long distances is a crucial step towards exchanging quantum cryptographic keys needed for encoding data sent over the fibres.

Quantum teleportation is a phenomenon in which the quantum states of one particle can be transferred to another, distant particle without anything physical traveling between them. It relies on a property called entanglement, in which measuring the state of one particle immediately affects the state of its entangled partner, regardless of the distance between them.The record for sheer distance between Alice and Bob was set in 2012, when a group led by Anton Zeilinger at the University of Vienna achieved teleportation over 143 kilometres of free space between two of the Canary Islands. But there’s no obvious way to translate that feat into a practical quantum network that would work within a city, where free space is hard to come by and other interference would destroy delicate quantum states.Now, Wolfgang Tittel at the University of Calgary in Alberta, Canada, and colleagues have upped the ante. They extended the distance between Charlie and Bob and teleported quantum states using part of Calgary’s fibre optic network that isn’t being used for regular communications.“The distance between Charlie and Bob, that’s the distance that counts,” says Tittel. “We have shown that this works across a metropolitan fibre network, over 6.2 kilometres, as the crow flies.”Jian-Wei Pan at the University of Science and Technology of China and colleagues achieved a comparable separation between Charlie and Bob when they teleported quantum states using the city of Hefei’s fibre optic network. Their setup was slightly different, though: it was Charlie in the middle who created the entangled pair of particles and sent one to Bob, instead of the other way around.Pan’s configuration could prove useful for building a quantum network within a city, where many sets of Alice-Charlie-Bob links each communicate with a central quantum computer. But Tittel’s team argues that their setup could enable quantum communication networks that stretch between cities.
That’s because it would allow for the creation of quantum repeaters, to propel the signal further along the network. Say Alice and Bob are 100 kilometres apart, with Bob to the right of Alice. Both create a pair of entangled particles each, keep one and send the other to Charlie, who is midway between them. Charlie performs the Bell state measurement, entangling the particles still with Alice and Bob.Now say Bob repeats the process with Daisy, who is 100 kilometres to his right (with another Charlie between them). At this stage, Bob has two particles, one entangled with Alice’s and the other with Daisy’s. If Bob now does a Bell State measurement on his two particles, he effectively entangles Alice’s particle with Daisy’s — stretching teleportation a full 200 kilometres.“You can scale the whole thing up and can go, in theory, to arbitrarily long distances,” says Tittel.“The two experiments can be seen as milestones on the path to a long-term goal, namely to build a fibre-based quantum internet connecting large cities,” says Johannes Kofler at the Max Planck Institute of Quantum Optics in Munich.

[SaiK]

Gaia has poor quality pics from what I could get on their web.

BTW, is the teleportation for real? I can send myself to desh for a coffee or mother's food for lunch and return back?

[PratikDas]

Karan Jani of LIGO team shared this amazing supercomputer simulation video on twitter, albeit with a horrible soundtrack of a screaming banshee. While I've only shared a poor quality animated GIF here, please click the link to see the smooth hi-res video.

Supercomputer simulations of Einstein's equations for parameters that matched with gravitational wave signal in LIGO

Questions:

• Is the black hole as large as the black circle or is it much smaller?
• If it is smaller, why don't we see anything for some space between the black hole and the perimeter of the black circle?

[Zynda]

Not in the physics profession, so take my reply FWIW and you probably may be aware of this and might be looking for a deeper explanation/answers.

There is something called as Event Horizon (sort of no escape zone) for all black holes. Once you are inside the event horizon, nothing can escape including light hence the dark/black circles. Now the core of the black hole may be at the centre but technically the black hole starts at the event horizon (perimeter).

Hope this answers your question.

[prasannasimha]

The event horizon is the area which is black. That is the point where light cannot escape(unless by Penrose radiation) and that makes the Black hole "Black" what happens inside is unknown.

[Zynda]

^^ You mean Hawking Radiation?

[PratikDas]

Not in the physics profession, so take my reply FWIW and you probably may be aware of this and might be looking for a deeper explanation/answers.

There is something called as Event Horizon (sort of no escape zone) for all black holes. Once you are inside the event horizon, nothing can escape including light hence the dark/black circles. Now the core of the black hole may be at the centre but technically the black hole starts at the event horizon (perimeter).

Hope this answers your question.

It does! Thank you.

[Gerard]

Apologies to all. Deleted a reported post then attempted to delete the report and deleted the thread instead. IOS is not the best platform for moderation tasks.
This is the old thread from TEF/GED. Plan was to merge this with the new thread.
Apologies again

[ArjunPandit]

Good article on
Gravitational waves
We ended up losing some very nice links by amber g

[Amber G.]

Is it easy to recover posts from backup? If so, it may be worth to do that.

Few latest posts here were about Gravitational waves, and as I said more than a year ago, it was a "big deal".. and as predicted it won the Nobel this year. I may repost a few links again in coming days.

Meanwhile, let me share an old song (30+years old) which I used to sing to my children (and now to grandchildren -
Bol, bol, bol mister golmatol
just how massive is a big black hole?
half the radius divide by G
and multiply by square of c.

(Clarify questions asked a few posts above about black holes )

[Amber G.]

Too bad that many recent exciting items and posts were deleted.
As I posted (in now deleted posts) about the rumor of major importance. -- hinted by Prof Weiss himself - he did not confirm or deny but asked people to wait - while all the data is checked/rechecked.
Everyone is talking about a major announcement ... Big rumor is that there is optical confirmation of gravitational waves..
(If true, only sources which give EM and Gravitational waves which LIGO can detect -- other than merging black holes - are super nova, or merging neutron stars. Rumors are that this has been detected by Chandra X-ray Observatory, and may be even by Hubble.

The announcement will be 7AM Pacific time, (7:30 PM Indian time) on October 16. So we will see.

http://public.virgo-gw.eu/ligo-virgo-scientists-to-discuss-new-developments-in-gravitational-wave-astronomy/

If what is said in rumor is true, all news papers will carry the story, so stay tuned.

[Amber G.]

^^^ Okay more on above:
- European Southern Observatory is billing as an "unprecedented discovery".
- The two organizations will be joined 70 other observatories ( with simultaneous briefings in multiple places).
IMO The scale of the announcement certainly suggests it is something big. (Bigger than their winning the Nobel this year)
NSF Statement:

The gathering will begin with an overview of new findings from LIGO, Virgo and partners that span the globe, followed by details from telescopes that work with the LIGO and Virgo collaborations to study extreme events in the cosmos,

”

For US people - the conference is due to take place at The National Press Club in Washington, on Monday 16 October at 8AM EST. One can watch it live on the National Science Foundation(https://www.nsf.gov/) or European Southern Observatory website.

Meanwhile today in Nature.com: Interesting article http://www.nature.com/news/global-networks-of-small-telescopes-will-chase-companion-signals-of-gravitational-waves-1.22828

[Amber G.]

xpost from other dhaga -- because there is real good information in the article..

Layman question here, why is noticing a pulse of two neutron stars merging such a big deal?

Have to post this answer from recent Wired Magazine -- !!!!

WHAT HAPPENS WHEN TWO NEUTRON STARS COLLIDE? SCIENTIFIC REVOLUTION

“If the detection is true, it would be transformative for the field and probably one of the greatest discoveries in astronomy,” said Enrico Ramirez-Ruiz of the University of California, Santa Cruz, who refused to discuss any specific results.

This is why I was saying it is a BIG deal!

[ArjunPandit]

I must say sir that you certainly bring excitement to these news. Hours of net browsing is eqtv to one few hours on some threads

[Amber G.]

^^^ Thanks. Yes discovery of gravitational waves has caused a lot of excitement. Not that any one doubted that these waves exist, but we were able to detect it experimentally. Prof Weiss and others have worked for this for 40+ years. The applications in other fields is the real payback.

[Amber G.]

Xpost:

Why Indian astrosat is not used for this

I knew some one will mention this!! I think it is being used. It is ideal in the sense that it gives Indian scientists faster and guaranteed access to the information as I think they have privileged access and some are excited about studying neutron stars from India (without having to wait for international support). Also according to some experts in one particular case Astrosat may be better than Chandra for detecting short-lived bursts of X-rays -- the kind LIGO is looking for.

Actually rumors are there and speculation is there for Astosat . LIGO team is tight-lip about it, and in all fairness we can wait in our speculation. (More optical /x-ray telescopes may be involved - we will know soon enough.


Also I believe, one of the things Astrosat is being used is to do "timing studies" of X-ray binaries..difference in timing is another way to study Gravitational waves ... more of this can be continued in physics dhaga.

(BTW IIRC it was in Indian newspapers - recent massive coronal explosion on the nearest planet-hosting star was observed by Astrostat (along with Chandra and Hubble)

[Zynda]

AmberG, what would be the outcome of two neutron stars colliding/merging? I've heard cosmologists say that result probably might be formation of a new black hole but is it possible due to the energy released from collision, the stars disintegrate and individual neutrons spread around (if such a thing could happen)? Probably using a wrong analogy here...like two planets colliding and result being shattered rocks? I hope this ain't a dumb thing to ask!

[Amber G.]

AmberG, what would be the outcome of two neutron stars colliding/merging? I've heard cosmologists say that result probably might be formation of a new black hole but is it possible due to the energy released from collision, the stars disintegrate and individual neutrons spread around (if such a thing could happen)? Probably using a wrong analogy here...like two planets colliding and result being shattered rocks? I hope this ain't a dumb thing to ask!

Far from being "dumb" this is a very interesting question -many physicists have been studying this for years.
Short answer: Three possibilities:
1) a stable neutron star,
2) - black hole, or
3) a supramassive neutron star, (sNS -- a large neutron star that’s supported by its rotation but will eventually collapse to a black hole after it loses angular momentum)

Whether a binary-neutron-star merger results in another neutron star, a black hole, or a super massive neutron star depends on the final mass of the remnant and what the correct equation of state is that describes the interiors of neutron stars (This is something people have been working for a long time --It is a longstanding astrophysical puzzle)... One of the thing people are excited about is that they may learn more from this new data and eventually pin down the correct equation of state for NS in coming years)

Best estimates at present for our universe (from observations and computer models/statistics) IMO is in around (80%-100%) of the cases it is a stable Neutron star or a sNS.

For more, check out Tolman–Oppenheimer–Volkoff limit from wiki.

[Amber G.]

Zynda - Also see this recent paper .. exactly the same question you asked !
http://iopscience.iop.org/article/10.3847/2041-8213/aa7f2f/meta;jsessionid=5CEA612A1D826478B45D6159F1EB9541.c4.iopscience.cld.iop.org
/Cut and Paste of the abstract as it may require subscription)
>>>

The Fate of Neutron Star Binary Mergers
Anthony L. Piro1, Bruno Giacomazzo2,3, and Rosalba Perna4
Published 2017 July 27 • © 2017. The American Astronomical Society. All rights reserved.
The Astrophysical Journal Letters, Volume 844, Number 2
358 Total downloads

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Article information
Abstract
Following merger, a neutron star (NS) binary can produce roughly one of three different outcomes: (1) a stable NS, (2) a black hole (BH), or (3) a supramassive, rotationally supported NS, which then collapses to a BH following angular momentum losses. Which of these fates occur and in what proportion has important implications for the electromagnetic transient associated with the mergers and the expected gravitational wave (GW) signatures, which in turn depend on the high density equation of state (EOS). Here we combine relativistic calculations of NS masses using realistic EOSs with Monte Carlo population synthesis based on the mass distribution of NS binaries in our Galaxy to predict the distribution of fates expected. For many EOSs, a significant fraction of the remnants are NSs or supramassive NSs. This lends support to scenarios in which a quickly spinning, highly magnetized NS may be powering an electromagnetic transient. This also indicates that it will be important for future GW observatories to focus on high frequencies to study the post-merger GW emission. Even in cases where individual GW events are too low in signal to noise to study the post merger signature in detail, the statistics of how many mergers produce NSs versus BHs can be compared with our work to constrain the EOS. To match short gamma-ray-burst (SGRB) X-ray afterglow statistics, we find that the stiffest EOSs are ruled out. Furthermore, many popular EOSs require a significant fraction of ~60%–70% of SGRBs to be from NS–BH mergers rather than just binary NSs.

..

[Zynda]

AmberG, thx for the info. Very interesting...the full paper needs a paid subscription.

[Amber G.]

^^^ You are welcome. Hope Gravitational Waves study increase our understanding of merger detail.
For the record, let me also put the pdf file of the GW famous paper published in PRL on Oct 5. This will be for history books.
(This has all the 1000+ authors listed.. what an honor for them to appear in this historic paper)
Breakthrough Prize last year was shared between 1000+ authors (including Weiss, Throne etc who won Nobel too) what a honor for all of them.
PRL Paper: GW170814: A Three-Detector Observation of Gravitational Waves from a Binary Black Hole Coalescence

[Amber G.]

In about 16 Hours from posting of this message, watch..

New Gravitational Wave Discovery (Press Conference and Online Q&A Session)



Edited Later: Going on NOW

[Amber G.]

Virtually everything I was speculating here (and more) was confirmed.
The event happened on August 17..
Yes, the gamma ray burst was noticed by 7 space based observatories (including India's) coherently.
There were 70+ other telescopes confirmed it. -- (Less than 1 in 20,000,000 chance that this was a coincidence)
Neutron stars were about the same the mass of our sun...
Also the question I answered about merger of Neutron Stars -- about learning about EOS of NS -- lot of new data.

And actually some one just asked did ask the panel - "Can one get a black hole when two neutron star collide" and answer was very close to the one I put here in brf!! )

[Amber G.]

Discussion of Gravity waves and neutron star merger is obviously a big news, and at present every newspaper is carrying the story.

What I have not seen in details yet is the Indian connection. Hope our newspapers etc contact our Indian Institutes and tell their story with pride.

Few things I know and it can be shared - I hope there are more standard sources appear in newspapers. (Some info was shared in emails or informally with many scientists before but everyone respected the wishes of the team, so as not to announce it unless it is checked and double checked)

These items , related to Indian connection, are in random order (BY NO MEANS a complete list):

The paper in ARL has about 3500 authors - Many Indians ( 50+ prominent 15 Indian Institution). Fields - computational analysis, General Relativity, Nuclear Physics, EOS of neutron stars, Astronomy, Astrophysics etc)

(Example: Prof Bose helped on how to strategically point telescopes to find the electromagnetic counterparts -- and it was successfully used by the Very Large Array radio telescope in New Mexico - which observed radio waves of thee merger.)

Several Indian telescopes such as the Astrosat, Giant Meter-wave Radio Telescope and the Himalayan Chandra Telescope were part of this team effort. (Astorsat could not observe the x-ray but failure to detect was actually provided very good understanding in its own way. Chandra did not initially see x-ray (even though it was looking for it very carefully) and has to wait for many days -- the signal was very faint, arrived several days after the gamma-ray pulse, but all this data actually helped understand the phenomena - the story is interesting and can be seen in other places)

Another very crazy part was the question about merger of two neutron stars. The remnant mass in this case is about 2.7 Solar mass. Quite interesting. Less than 2 and we can predict it will merge into a neutron star. Greater than 5, it will be a black hole. So from crude calculation alone - this is either a very large NS or very small black-hole or sNS.

[Amber G.]

AmberG, what would be the outcome of two neutron stars colliding/merging? I've heard cosmologists say that result probably might be formation of a new black hole but is it possible due to the energy released from collision, the stars disintegrate and individual neutrons spread around (if such a thing could happen)? Probably using a wrong analogy here...like two planets colliding and result being shattered rocks? I hope this ain't a dumb thing to ask!

In this case, believe it or not, we finally started understanding- in case of NS they are not "shattered rocks" but Gold and Platinum (and some uranium etc)... Actually pure gold weighing something around 10,000 times the mass or earth!

This is *another* BIG discovery.

For the first time we now are certain how some of the heaviest elements came here. So all the gold you see now on earth has come from such a Kilonova event. The first time we have seen the spectrum of thiss.. and as one scientist put it literally

pot of gold over at the end of a rainbow (spectrum)

[Zynda]

AmberG, I've got a few more questions regarding Neutron Stars. Hope its OK. And thanks for providing additional info including the excellent infographic of the discovery. I've heard that heavier elements such as gold are also product from massive star cores...

1. If a normal star is in very close proximity of a black hole and if the black hole is feeding off on the star, we get a streak of matter which then forms an accretion disk before going in to the black hole like what is rendered in the image below. Does this happen if a neutron star is in very close proximity to a black hole as well?



Guess what I am asking is, since a neutron star is more tightly packed compared to a normal star, what kind of energies are required to make a patch of material separate from its host star?

2. If the merger of the two neutro stars like the event that happened on Aug 17th, results in the formation of a new neutron star, does the new star retain the same density?

[Amber G.]

AmberG, I've got a few more questions regarding Neutron Stars. Hope its OK. And thanks for providing additional info including the excellent infographic of the discovery. I've heard that heavier elements such as gold are also product from massive star cores...

To best of our understanding -
Yes heavier elements come from star core's but only up till Iron.
- Elements H, and He were there / got created around big bang...
- Elements from Li to Fe (Iron) are formed inside stars (Carl Sagan's words "We are star stuff")

Elements heavier than elements came from Nova/super Nova/ or Kilonova -- neutron stars collide. {new discovery}
- Theories / observed spectrums of Super Nova explosions accounted for nearly half of heavier metals nicely but not everything fit
-till the recent observation (observed from spectrum) sheds new light. About half of the heavier elements (like Gold, Platinum, Uranium) are from Neutron start collision...
And this discovery is quite important.. very big deal.

1. If a normal star is in very close proximity of a black hole and if the black hole is feeding off on the star, we get a streak of matter which then forms an accretion disk before going in to the black hole like what is rendered in the image below. Does this happen if a neutron star is in very close proximity to a black hole as well?

Actually LIGO team did not deny (until today) that the possible event was Neutron Star/Black hole merger. Yes this can take place.
(Like BH/BH, BH/NS, or NS/NS) and they will produce waves which LIGO can detect.

(Actually what exactly happens obviously depend on lot of factors ... I think more experimental data we get, more we know the details.

If the merger of the two neutro stars like the event that happened on Aug 17th, results in the formation of a new neutron star, does the new star retain the same density?

Neutron star density (about the same range as nucleus) does obviously vary depending on size (or even how far inside the crust).. it is quite heavy ..on average from (4)*10^17 to 6*10^17 heavier than water.. (near crust - density could be billion times less, but still billions time that of water)... Any way a real massive NS can collapse (increasing it's density) and may even become a black hole.

Hope this helps.
(I have also checked Wiki articles and most, I'll say are quite good so they may be good resources too).

BTW - Per LIGO team, we still don't know if the recently detected merger resulted into black hole or not. It requires further study.

[Amber G.]

Here is the historic Paper -- Hot of the press!
GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral

[Amber G.]

(From above:)

.....The authors also gratefully acknowledge research support from these agencies as well as by the Council of Scientific and Industrial Research of India, the Department of Science and Technology, India, the Science & Engineering Research Board (SERB), India, the Ministry of Human Resource Development, India,..

(Wonder if these institutes get recognition they deserve from Indian Press / Bloggers /Forums /)

[ramana]

Dr. Karan Jani in Swarajya

https://swarajyamag.com/science/gravita ... especially

[Mort Walker]

I'm happy this happened 100 million light years away, otherwise big trouble if it happened within a few hundred light years away.

[Mort Walker]

Actually LIGO team did not deny (until today) that the possible event was Neutron Star/Black hole merger. Yes this can take place.
(Like BH/BH, BH/NS, or NS/NS) and they will produce waves which LIGO can detect.

Couldn't this be confirmed by the Chandra or other X-Ray telescopes? I would think if NS/BH merger would mean we wouldn't detect gamma rays from near earth.

[Mort Walker]

Here is the historic Paper -- Hot of the press!
GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral

I don't know enough about this, but the statement:

The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0×10^4 years.

As an engineer this really bothers me reading the source paper as to how they calculated the SNR.

[Amber G.]

To best of our understanding -
Yes heavier elements come from star core's but only up till Iron.
- Elements H, and He were there / got created around big bang...
- Elements from Li to Fe (Iron) are formed inside stars (Carl Sagan's words "We are star stuff")

Elements heavier than elements came from Nova/super Nova/ or Kilonova -- neutron stars collide. {new discovery}
- Theories / observed spectrums of Super Nova explosions accounted for nearly half of heavier metals nicely but not everything fit
-till the recent observation (observed from spectrum) sheds new light. About half of the heavier elements (like Gold, Platinum, Uranium) are from Neutron start collision...
And this discovery is quite important.. very big deal.

Here is a very nice picture: (Where elements came from)... (This is up to date - Thanks brf - where this nice q was asked)