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Physics Discussion Thread

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Re: Physics Discussion Thread

Postby Amber G. » 17 Oct 2017 07:18

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

More reason to be happy - those black holes from the other GW were 1000 times further (Billions of light years):)

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Re: Physics Discussion Thread

Postby Mort Walker » 17 Oct 2017 07:32

^^^THANKS! I was looking for that earlier!

What about 43-Tc and 61-Pm, they haven't been accounted for yet?

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Re: Physics Discussion Thread

Postby Amber G. » 17 Oct 2017 07:33

ramana wrote:Dr. Karan Jani in Swarajya

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


Thanks!

Karan is part of LIGO team (one of the authors in the paper)! (You may know this, recent he was chosen as 30 under 30 Forbes list etc - and he was one of the person in the picture with Narendra Modi I posted in this dhaga some time ago. (NaMo, when he was in DC in 2016 met young Indian origin scientists and asked this young scientist to explain GW to him and he was impressed that NaMo took such an interest).

OT [sigh]
Unfortunately that picture sent the usual trolling character in a tizzy ..who ended up posting OT messages in this dhaga -unfortunately that post along with dozens of other nice posts disappeared in the cleanup.

Happy that this time this dhaga is free from trolling (till now at least) /sigh/


Last edited by Amber G. on 17 Oct 2017 23:51, edited 1 time in total.

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Re: Physics Discussion Thread

Postby Amber G. » 17 Oct 2017 07:50

Mort Walker wrote: ...
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.

Chandra (and other X-ray telescopes) were alerted not only by LIGO but also by Fermi's Gamma ray burst (noticed independently about 1.7 ms later!) Now Gamma Ray bursts are quite common - even lightning will produce it - but "interesting ones" alerts other telescopes to look in the area. After hearing from LIGO they knew this may be interesting.

But Chandra (and others too) did not see x-ray even they were looking for it. ... others telescopes (in visible, UV, infrared) did see it. So Chandra knew exactly where to look. Later Chandra did notice x-ray but it was much fainter than what it sees from other binary neutron stars..Anyway long story short - the x-rays are quite focused in narrow beam and so if you are not in the narrow beam the intensity will be much lower... (It is like seeng bright beam from side-ways - it will not look that bright).

All things did fit quite well. ("Wave was loud but flash wasn't bright, Yet they found that Einstein was right" as some one tweeted :))

One thing is impressive - absolute cooperation/team work along so many people (3500+ authors) -- 70+ Telescopes etc..Though rumors were flying, no one gave press conferences or tweeted the details before formal announcement. They did check and recheck.

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Re: Physics Discussion Thread

Postby Zynda » 17 Oct 2017 13:29

Thanks AmberG for your answers. Really illuminating posts...

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Re: Physics Discussion Thread

Postby JayS » 17 Oct 2017 16:33

Amber G. wrote:
Thanks!

Karan is part of LIGO team (one of the authors in the paper)! (You may know this, recent he was chosen as 30 under 30 Fortune list etc - and he was one of the person in the picture with Narendra Modi I posted in this dhaga some time ago. (NaMo, when he was in DC in 2016 met young Indian origin scientists and asked this young scientist to explain GW to him and he was impressed that NaMo took such an interest).

Truly a historic event. Anyone who has read anything about Theory of Relativity or Einstein in general would have at least some idea how important the discovery of Gravitational wave is.

In this article that ramana linked, the author mentions the third breakthrough from this event (apart from GW and origin of heavy elements) - Calculation of rate of expansion of universe and age from that. Any word on this..? How does this new estimate compares with previously widely accepted figures...?

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Re: Physics Discussion Thread

Postby Amber G. » 17 Oct 2017 21:34

JayS wrote:
Amber G. wrote:
<snip>

Truly a historic event. Anyone who has read anything about Theory of Relativity or Einstein in general would have at least some idea how important the discovery of Gravitational wave is.

In this article that ramana linked, the author mentions the third breakthrough from this event (apart from GW and origin of heavy elements) - Calculation of rate of expansion of universe and age from that. Any word on this..? How does this new estimate compares with previously widely accepted figures...?


Agree that importance of can not be overstated..more when we have more such data and get a new event every month or every week (likely when India's LIGO and Japan's detector starts working fairly soon) and we observe many such events through telescopes also.

To answer your question, one who worked in this field for 30+ years, (and tried to improve on Einstein / prove him "wrong") said something like "That bugger Einstein is *always* right"!! (No small achievement).

ALL data fit his equations correctly.

Your question, I believe, is about the refinement of Hubble's constant..
Now with this new tool we can measure distance of binary neutron stars to *much* better precision. Up till now one of the best method to measure the distance of far away galaxy is to study binary neutron start inside. This was done optically (or through other EM telescopes) but there was quite a bit of uncertainty. The speed can be measured by Doppler shift fairly accurately.
More data will be nice to study more of the universe, ..but meanwhile recent paper :)

A gravitational-wave standard siren measurement of the Hubble constant

The detection of GW170817 (ref. 1) heralds the age of gravitational-wave multi-messenger astronomy, with the observations of gravitational-wave and electromagnetic emission from the same transient source. On 17 August 2017 the network of Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)2 and Virgo3 detectors observed GW170817, a strong signal from the merger of a binary neutron-star system. Less than two seconds after the merger, a γ-ray burst event, GRB 170817A, was detected consistent with the LIGO–Virgo sky localization region4–6). The sky region was subsequently observed by optical astronomy facilities7, resulting in the identification of an optical transient signal within about 10 arcseconds of the galaxy NGC 4993 (refs 8–13). GW170817 can be used as a standard siren14–18, combining the distance inferred purely from the gravitational-wave signal with the recession velocity arising from the electromagnetic data to determine the Hubble constant. This quantity, representing the local expansion rate of the Universe, sets the overall scale of the Universe and is of fundamental importance to cosmology. Our measurements do not require any form of cosmic ‘distance ladder’19; the gravitational-wave analysis directly estimates the luminosity distance out to cosmological scales. Here we report H0 =  kilometres per second per megaparsec, which is consistent with existing measurements20,21, while being completely independent of them.
Last edited by Amber G. on 17 Oct 2017 21:50, edited 1 time in total.

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Re: Physics Discussion Thread

Postby Bade » 17 Oct 2017 21:49

Amber_G, would like to bring to your attention this link which was not posted yet here.

http://i2.wp.com/www.gw.iucaa.in/wp-con ... raphic.png

from here at IUCAA, which has a lot more details and names of individuals involved from the Indian side.
http://www.gw.iucaa.in/news/gw170817/

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Re: Physics Discussion Thread

Postby Amber G. » 17 Oct 2017 21:53

Thanks Bade!!!

(From his link: the part about Hubble's constant and answer to Jay's query)
Image

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Re: Physics Discussion Thread

Postby Amber G. » 17 Oct 2017 22:02

Bade's link's graphic is really NICE!! Allow me to post it:
Image

(Nice to see this is also being shown in many Indian languages)
Here is one in Oriya (Thanks to Satya Mohapatra from MIT)
Image

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Re: Physics Discussion Thread

Postby Amber G. » 18 Oct 2017 00:00

Bade - Long time ago you mentioned Prof Abhay Ashtekar in this dhaga..
I am sure you know that he is now chair of LIGO/India's international advisory panel and was mentor to many of the people in LIGO team.
I posted this article about him recently after GW news but the post was lost in dhaga cleanup. Reposting again..if people have not seen it.

Good Scientists Solve Problems, but Great Scientists Know What’s Worth Solving’
Image

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Re: Physics Discussion Thread

Postby ArjunPandit » 18 Oct 2017 00:28

I was wondering if rotating wormholes would give rise to gravitational waves, and here is what I stumbled upon

http://physicsworld.com/cws/article/new ... lack-holes

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Re: Physics Discussion Thread

Postby Amber G. » 18 Oct 2017 03:04

Let me post (again as the last post was gone in the thread cleanup) a video (about 2 minutes) from 2016 when Indian PM came to US and had encouraging words to say about LIGO project. (Thanks to such leaders, for LIGO india may actually open in about 5 years)
https://www.youtube.com/watch?v=2ASO2weDCKQ

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Re: Physics Discussion Thread

Postby Amber G. » 18 Oct 2017 04:10

This was posted a few days before Nobel Prize was announced. As predicted, Nobel was awarded to LIGO team (I named the people correctly too).. I am reposting this post. Worth a read.
Amber G. wrote:
This week, Nobel Prize in Physics, most likely will be awarded for LIGO...
In this respect, we must honor the gurus. Here is a nice writeup, very worth reading in full.
Why We Need To Thank Homi Bhabha for India's Role In The Discovery of Gravitational Waves
Image


Image
Interestingly the picture in the about article : shows, Einstein, Hideki Yukawa(Nobel 1949), John Wheeler and Bhabha!
(Einstein's theory predicted Gravitational Waves, John Wheeler (also Nobel Prize winner) is the person who coined the term "black hole".. his student Thorne won this years Nobel. (another of his student is Feynman).)
Last edited by Amber G. on 18 Oct 2017 20:38, edited 1 time in total.

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Re: Physics Discussion Thread

Postby Bade » 18 Oct 2017 06:20

The wire article on Ashtekar was a very good one. I had seen it before but skipped it to read more carefully and promptly forgot about it. Thanks for reposting it. I am not that frequent on these forums anymore.

The above old B&W picture of Bhabha I had seen first time in one of the magazines while still a school student in India...I think it was science today perhaps.

The wire had a nice article on the recent multi wavelength event too.

https://thewire.in/187957/neutron-star- ... ray-burst/

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Re: Physics Discussion Thread

Postby Amber G. » 20 Oct 2017 02:41

Today is 107 Birthday of Subrahmanyan Chandrasekhar!

Google is honoring him today!

Image

Twinkle, twinkle little star, how I wonder what you are.” Thanks to Subrahmanyan Chandrasekhar, we know! Today marks the 107th birthday of the first astrophysicist to win a Nobel Prize for his theory on the evolution of stars.

A child prodigy, Chandra published his first paper and developed his theory of star evolution before turning 20. By age 34, he was elected to the Royal Society of London, and soon after, became a distinguished service professor of physics.

The Indian-American physicist’s honors are astronomical, including the National Medal of Science, the Draper Medal of the US National Academy of Science, and the gold medal of the Royal Astronomical Society. Though originally met with skepticism in the 1930s, Chandra’s theories and equations won the Nobel Prize in Physics 50 years later.

Today’s Doodle illustrates one of the most important of all of S. Chandrasekhar's contributions to our understanding of stars and their evolution: The Chandrasekhar limit. The limit explains that when a star’s mass is lighter than 1.4 times that of the sun, it eventually collapses into a denser stage called a “white dwarf.” When heavier than 1.4, a white dwarf can continue to collapse and condense, evolving into a black hole or a supernova explosion.

Today we honor the original starman whose universal theories propel current space research and modern astronomy on their ambitious missions.

Happy birthday, Chandra!

Link: S. Chandrasekhar’s 107th Birthday

I am sure he would have been very happy to hear about recent discovery of Gravitational Waves and observation of coalescence of neutron stars!

The birthdate 19/10/1910 always looked curious. In 2010 -- 100th Birthday was a big event, both in India and in US.

I posted in Brf around that time - UC's president remembered him by telling a story. Chandra used to drive 50+ miles each way just to teach a class which had only two students. Such was his dedication. But, as the president reminded, every one in that class (Yang, Lee) got a Nobel in physics, so that was worth it. This was the only class, the president noted, where entire class and the professor got a Nobel! (Later some one corrected -- It wasn't exactly true that there were only two students, one more person sat in the class unofficially and occasionally.. this was Fermi!! (but he already had a Nobel)

I distinctly remember when the news of Nobel for him was announced which inspired a me to explain stellar structure to some people in my family :) . I was happy that he finally received the well deserved recognition -- I knew the family. His uncle also had a Nobel Prize in Physics. Many other people in his family were quite notable in sciences. Both US and India can be proud of him.

Arjun Pandit asked about books, one good book about his life is(By Wali (Chandra).
(About a year ago, there was this post with reference to Chandra.. some may find it interesting,

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Re: Physics Discussion Thread

Postby Mort Walker » 20 Oct 2017 03:13

It should also be noted that SC also expected postulated gravity waves when the "heavy" star collapsed into a black hole.

Happy Diwali!

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Re: Physics Discussion Thread

Postby Mort Walker » 20 Oct 2017 03:14

BTW, LIGO is being shut down temporarily for an upgrade. It's suppose to take a while from what I understand.

Here's yet another link about LIGO detecting a neutron star merger.
New LIGO discovery is an astronomer’s dream come true.

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Re: Physics Discussion Thread

Postby Amber G. » 20 Oct 2017 03:26

^^^In recent press conf, per MIT's David Shoemaker, the next joint observation run is planned for the Autumn of 2018. Some enhanced sensitivity will make a big difference. He said something like:
With the next observing run planned for Fall 2018 we can expect such detections weekly or even more often.

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Re: Physics Discussion Thread

Postby Mort Walker » 20 Oct 2017 04:14

^^^Yes. It is the intersection of engineering and physics. The question to ask about such large complicated and sensitive projects such as LIGO is that when there is a systematic error, how will it be detected and then corrected? Understanding the science, even though it is complicated, is doable. Building, maintaining and making accurate measurements falls into the hands of engineers who are limited to the tools that are available at present. The engineering problem that LIGO presents is formidable from the electro-mechanical hardware to the software. We're talking about detecting oscillations in the tens-of-Hertz over a period less than a couple of minutes. You could conceivably make a gravity wave detection without it being corroborated by other sensors such as Chandra X-ray telescope, Fermi gama ray telescope, and neutrino detectors. Einstein thought that detecting gravity waves would never happen, but it has.

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Re: Physics Discussion Thread

Postby sanjaykumar » 20 Oct 2017 09:01

Sensitivity of interferometry inherently makes the job easier. What has been detected is interpretable as gravity oscillations. Much as black holes fit a system of theory whereas an alternate, boson stars?, may be turn out to be the reality ultimately.

These are findings that arise from internally consistent models. It may be hubris to assume that is the way the universe works.

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Re: Physics Discussion Thread

Postby Amber G. » 20 Oct 2017 10:48

Sensitivity of LIGO is remarkable .. almost hard to believe..

It is equivalent to measuring the distance between here and Alpha Century (40,000,000,000,000 Km) with precision of thickness of a human hair. Amazing.
Isolating from seismic, thermal noise, vibration etc is remarkable. Small waves in the ocean, people walking nearby, lightning 100's of miles away and literary around 100,000 other causes have to be filtered out (their "signature" included in computer noise reduction etc). As they were telling, when they started LIGO in LA, it was hunting season and bullets fired by hunters in the woods near by, which they did not encountered before in WA, has to be taken into account.

One part which I did not realize, was his mentioning of gravitational gradient - For example air waves where one part of air is denser than other produces effects due to gravitational attraction -- even though there is vacuum in the tubes. (According to them, it is still the hardest thing to filter-out - Although the hope that Japan's machine (which will be underground) and at low temperature will be better.

Tremendous advances in Lasers, seismic isolation techniques etc.

40 years of hard work - they never thought they will actually find GW - They justified the funding because they convinced NSF that learning new technologies will be enough pay back even if they never actually found any GW. They were very fortunate that equipment/technologies became better and better (by a factor of 10^12) in those 40 years.

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Re: Physics Discussion Thread

Postby Amber G. » 20 Oct 2017 10:56

^^^ Next step LISA (or eLISA) is to be built in space. Better vacuum, much less thermal noise, seismic activity - much much better isolation.

And the tubes, instead of 4 Km, could be millions of Km long. (You don't need tubes, just multiple sats)
(All of this will be in about 20 years).

Meanwhile, in about 5-7 years - addition of LIGO-India, and Japan - the sensitivity is going to be 10x, resulting 1000x times detecting of GW. Probably one event of so every day -- we may start mapping the universe using GW.

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Re: Physics Discussion Thread

Postby Dumal » 20 Oct 2017 11:54

Beginner question:

The graphic in this page answered my first question - i.e., does a gravitational wave also travel at the speed of light/em wave? - and the answer it says is - yes, it does! Does the detection of the event at or near the earth in August 2017 mean that it took place 130 million lights years ago?

Also a broader question. I understand that Einstein's theories and science since then confirm that no body which has any mass or energy can travel at speeds faster than that of light. Does this then imply any meaningful exclusion? Is there such a thing that has no mass or energy that is fundamentally relevant and moves at a greater speed than c?

Also do the theories of big-bang explosion, the expansion following it and the theories around the rapidly expanding universe, all get limited by the speed of light?

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Re: Physics Discussion Thread

Postby Amber G. » 20 Oct 2017 12:21

Dumal wrote:Beginner question:

The graphic in this page answered my first question - i.e., does a gravitational wave also travel at the speed of light/em wave? - and the answer it says is - yes, it does! Does the detection of the event at or near the earth in August 2017 mean that it took place 130 million lights years ago?

Also a broader question. I understand that Einstein's theories and science since then confirm that no body which has any mass or energy can travel at speeds faster than that of light. Does this then imply any meaningful exclusion? Is there such a thing that has no mass or energy that is fundamentally relevant and moves at a greater speed than c?

Also do the theories of big-bang explosion, the expansion following it and the theories around the rapidly expanding universe, all get limited by the speed of light?

Yes - Gravitational Waves travels with the speed of light (=c) .
Yes - The Event detected on August 2017 happened 130 million years ago.
Any particle which has mass (rest mass greater than zero **note 1 *)* can travel with a velocity less c .
Particles (or waves - same thing) of zero rest mass can travel with velocity = c.
With exception of things like imagination , or abstract "shadows"/waves(note *2) , nothing moves faster than light. Particularly One can not pass INFORMATION from point A to point B faster than c.
Yes, expansion of universe is limited by speed of light.
Hope this helps.
Note 1 ** In relativistic theory mass is not constant - it depends of the speed. So we talk about "rest mass" (mass at v=0) as fundamental property of a particle. Thus a photon which may have energy, but it has zero rest-mass.

Note 2 **There are theoretical concepts (like certain phase velocities) where one can have velocity > c (good example is one's imagination) but it is not practical way to move information. There are theories of "Tachyon" particles which moves faster than light.
(Nice theory by Great Indian Physicist Sudarshan) but they have not been observed. (Neither do they violate the Einstein's theory).
Hope this helps.

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Re: Physics Discussion Thread

Postby srinebula » 20 Oct 2017 12:31

Swarajya carried on article on Chandrasekhar's birth anniversary:
https://swarajyamag.com/science/chandra ... gle-doodle

Chandrasekhar would recall how one Father Saldanha, a Christian missionary from Kerala, would slip books into his cabin that characterised Hindu gods as primitive, evil and corrupt. While other Hindu students would fume at the missionary, Chandrasekhar would silently listen to him “more out of politeness than anything else” and yet he “never left him in doubt that he did not share his views”.

Chandrasekhar’s astrophysics guru at Trinity was Sir Arthur Eddington.


The day 11 January 1935, which should have been a dream launch for a brilliant career of a genius astrophysicist, turned into a nightmare for the young Indian. Yet Eddington, who “himself had flirted with the idea that a dead star might collapse indefinitely in this manner”, without any warning attacked Chandra’s result with convoluted and flimsy arguments. The event would leave a scar on the young Indian physicist prodigy, who was just 20 at the time. Later, Chandrasekhar would recall that Eddington was the only astrophysicist who, with his “enormous physical insight”, would understand that what Chandra proposed implied black holes. Had Eddington accepted that, “he would have been 40 years ahead of anybody else”.


This incident was also mentioned in Hawking's book "A brief history of time".

What happened to Chandrasekhar in Cambridge is not an isolated phenomenon. It had also happened to Jagadish Chandra Bose in 1901 at the Royal Society. A whole century and a decade after biophysicist V A Shepherd would point out that science had vindicated Bose: “In 2011 it is understood that most and perhaps all plant cells are excitable, responding to stimuli such as heat, cold, wounding, touch and changes in extra-cellular osmotic pressure with electric signals.”


Yellapragada Subbarow (1895-1948) discovered ATP (adenosine triphosphate), the biological energy coin, in 1929. He was then a graduate student at Harvard Medical School. He also discovered a host of other biochemical remedies for various diseases. However, he never received full credit for his discovery then because “his PhD supervisor Cyrus Fiske took credit for his work”. George Hitching, a fellow student at Harvard, who went on to share the Nobel prize in physiology for the year 1988, said that “some of the nucleosides isolated by Subbarao had to be rediscovered years later by other workers because Fiske apparently out of jealousy, did not let Subbarao's contributions to see the light of the day” (Krishna R Dronamraju, Popularizing Science: The Life and Work of JBS Haldane, Oxford University Press, 2017).

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Re: Physics Discussion Thread

Postby Dumal » 20 Oct 2017 13:18

Amber G. wrote:Yes - Gravitational Waves travels with the speed of light (=c) .
Yes - The Event detected on August 2017 happened 130 million years ago.
Any particle which has mass (rest mass greater than zero **note 1 *)* can travel with a velocity less c .
Particles (or waves - same thing) of zero rest mass can travel with velocity = c.
With exception of things like imagination , or abstract "shadows"/waves(note *2) , nothing moves faster than light. Particularly One can not pass INFORMATION from point A to point B faster than c.
Yes, expansion of universe is limited by speed of light.
Hope this helps.
Note 1 ** In relativistic theory mass is not constant - it depends of the speed. So we talk about "rest mass" (mass at v=0) as fundamental property of a particle. Thus a photon which may have energy, but it has zero rest-mass.

Note 2 **There are theoretical concepts (like certain phase velocities) where one can have velocity > c (good example is one's imagination) but it is not practical way to move information. There are theories of "Tachyon" particles which moves faster than light.
(Nice theory by Great Indian Physicist Sudarshan) but they have not been observed. (Neither do they violate the Einstein's theory).
Hope this helps.


Thank you Amberji! This is very helpful. Thank you also for the additional points and the clarification on the "rest mass".

BTW, what would be a good beginner (senior school) level book/material to understand relativity. There is a Stanford online course on "Understanding Einstein: Special theory of relativity" on Coursera that just started, but find it too time-consuming with the long videos. Would be great to have a book to read along with that.

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Re: Physics Discussion Thread

Postby Zynda » 20 Oct 2017 14:48

If you are not looking to understand it at a technical level i.e. mathematics, very deep understanding but at a high-level conceptual level, then my suggestion is to pick up any of the science books written for general audiences by well known physicists. They do a pretty good job of simplifying the concepts to a level which can be understood by layman.

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Re: Physics Discussion Thread

Postby Amber G. » 21 Oct 2017 02:17

^^^ Agree with above. To add some specific recommendations:
Dumal wrote:BTW, what would be a good beginner (senior school) level book/material to understand relativity. There is a Stanford online course on "Understanding Einstein: Special theory of relativity" on Coursera that just started, but find it too time-consuming with the long videos. Would be great to have a book to read along with that.

For general audience: There are many good books on special theory, not that many good books on General Relativity.
IMO best (certainly my favorite, and mentioned in this forum *many* times ) are: George Gamow's One Two Three Infinity
and of course, Mr. Tompkins in Wonderland

Both books, written by a master, explains concepts of both SR and GR in layman's terms but are very serious books.
Another gem for special relativity is "What is Relativity" by Landau (greatest Russian Physicist of our time). I bought a copy (translation, original is in Russian) for 1 Rs in India. But is is one of the best books for concepts. Landau's series (every branch of modern physics - set of books "Course in Theoretical Physics"(https://en.wikipedia.org/wiki/Course_of_Theoretical_Physics)) also covers these topics but the popular book (about 50-60 pages) mentioned above is written for layman.

For GR, unfortunately one needs math to appriciate it fully. Good classic books (used as text books) for serious students are IMO from 1) Weinberg, 2) Misner, Thorne and Wheeler and 3) Hawkins and Ellis... But one of the recent book I have seen is a *very* good introductory book (actually given as a gift from my son) - is by Carroll ( Introduction to GR - Space Time and Geometry). (Advance UG or graduate level but still much easier to read than other books I have seen).

I have been very lucky to take a course from CN Yang who was an excellent teacher - but that was long ago. (Yang was student of both Einstein, and also Chandrasekhar BTW).

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Re: Physics Discussion Thread

Postby Amber G. » 21 Oct 2017 03:52

Will be good if someone here can provide an official source (or other source), whenever it is available for public, to officially confirm what everyone is assuming.

Third LIGO detector (INDIGO) is going to be in Hingoli ( Maharashtra). Third LIGO facility and the only one outside US. (This will add to VIRGO in Europe and KAGRA in Japan). ( Expected to cost 1000+ crore) Exciting new field of gravitational wave astronomy! Expected date 2023-2024

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Re: Physics Discussion Thread

Postby arvin » 21 Oct 2017 08:42

Thanks Amber G for the detailed explanations and simplifying things regarding gravitational waves.

As per web, land acquistion is in progress in Hingoli but exact location is still confidential.
https://timesofindia.indiatimes.com/cit ... 882081.cms

The link below looks like website for indian LIGO.
http://www.gw-indigo.org/tiki-index.php?page=LIGO-India

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Re: Physics Discussion Thread

Postby Amber G. » 22 Oct 2017 00:52


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Re: Physics Discussion Thread

Postby ArjunPandit » 24 Oct 2017 09:46

Amber sir,
any recommendations for science magazine subscription for myself, was thinking from these one scientific american, new scientist and sciencenews.

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Re: Physics Discussion Thread

Postby Amber G. » 24 Oct 2017 20:47

Amber G. wrote:
Another gem for special relativity is "What is Relativity" by Landau (greatest Russian Physicist of our time). I bought a copy (translation, original is in Russian) for 1 Rs in India. But is is one of the best books for concepts. Landau's series (every branch of modern physics - set of books "Course in Theoretical Physics"(https://en.wikipedia.org/wiki/Course_of_Theoretical_Physics)) also covers these topics but the popular book (about 50-60 pages) mentioned above is written for layman.
.

I was checking, and found that Landau's book is still available and still quite inexpensive. It is available online for free too. Excellent book, only about 50-60 pages.
(Apparently I am not the only one who liked this somewhat unknown gem)
Novel Prize physicist L. D. Landau and his distinguished colleague G. B. Rumer, employ a simple and straightforward manner to illuminate relativity theory's more subtle and elusive aspects. Using such familiar objects as trains, rulers, and clocks, the authors explain the reasoning behind seemingly self-contradictory ideas in which the relative seems absolute, but the absolute proves to be relative. A series of playful cartoons highlights the authors' witty observations on the laws governing inertia, the speed of light, the relationship of work and mass, and other relativistic concepts.
"The exposition is masterful . . . a superb book." — New York Times Book Review.
Last edited by Amber G. on 24 Oct 2017 21:03, edited 1 time in total.

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Re: Physics Discussion Thread

Postby JayS » 24 Oct 2017 20:51

Amber G. wrote:Thanks Bade!!!

(From his link: the part about Hubble's constant and answer to Jay's query)
Image


Thanks a ton AmberG for the info. Looks like the value is in the ballpark (well better than ballpark actually) of existing estimates. So no big surprise.

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Re: Physics Discussion Thread

Postby Dumal » 24 Oct 2017 21:10

Amber G. wrote:
Amber G. wrote:
Another gem for special relativity is "What is Relativity" by Landau (greatest Russian Physicist of our time). I bought a copy (translation, original is in Russian) for 1 Rs in India. But is is one of the best books for concepts. Landau's series (every branch of modern physics - set of books "Course in Theoretical Physics"(https://en.wikipedia.org/wiki/Course_of_Theoretical_Physics)) also covers these topics but the popular book (about 50-60 pages) mentioned above is written for layman.
.

I was checking, and found that Landau's book is still available and still quite inexpensive. It is available online for free too. Excellent book, only about 50-60 pages.
(Apparently I am not the only one who liked this somewhat unknown gem)
Novel Prize physicist L. D. Landau and his distinguished colleague G. B. Rumer, employ a simple and straightforward manner to illuminate relativity theory's more subtle and elusive aspects. Using such familiar objects as trains, rulers, and clocks, the authors explain the reasoning behind seemingly self-contradictory ideas in which the relative seems absolute, but the absolute proves to be relative. A series of playful cartoons highlights the authors' witty observations on the laws governing inertia, the speed of light, the relationship of work and mass, and other relativistic concepts.
"The exposition is masterful . . . a superb book." — New York Times Book Review.


You're right. Not only is it quite thin and inexpensive, when googling it up, I also found it available for download in archive.org. Looks like a fun book for beginners to get used to the concepts. Thanks again!

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Re: Physics Discussion Thread

Postby Amber G. » 24 Oct 2017 22:05

^^^ Agree, the book is very good.
Landau's 10 Volume set is one of my most valuable possession. (Excellent books on course in Theoretical Physics). Landau, of course, is now considered as Russia's greatest scientist (honor equivalent to Einstein).

BTW, legend has it that Landau "wrote" much of the series (1000's pages) in his head while in Russian prison (40's)]. Actual writing of at least the early volumes was done by his student Lifshitz. (That's why many say about those books "not a word of Landau and not a thought of Lifshitz).

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Re: Physics Discussion Thread

Postby JayS » 25 Oct 2017 15:30

I used to read from this collection of Scientific American off-print collection, when I was in Junior college - "Readings in the Physical Sciences and Technology: v. 1-3". Some of the articles are brilliant, explaining basic concepts like Uncertainty Principle, Exclusion Principle, Relativity, Particle zoo, anti-matter (written by prominent physicists). I used to love the articles. Its 1969 edition and quite old now for a lot of topics, but still a good read, I would say.

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Re: Physics Discussion Thread

Postby ArjunPandit » 25 Oct 2017 17:23

JayS wrote:I used to read from this collection of Scientific American off-print collection, when I was in Junior college - "Readings in the Physical Sciences and Technology: v. 1-3". Some of the articles are brilliant, explaining basic concepts like Uncertainty Principle, Exclusion Principle, Relativity, Particle zoo, anti-matter (written by prominent physicists). I used to love the articles. Its 1969 edition and quite old now for a lot of topics, but still a good read, I would say.

Thanks JayS

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Re: Physics Discussion Thread

Postby JayS » 25 Oct 2017 20:14

Amber G. wrote:^^^ Next step LISA (or eLISA) is to be built in space. Better vacuum, much less thermal noise, seismic activity - much much better isolation.

And the tubes, instead of 4 Km, could be millions of Km long. (You don't need tubes, just multiple sats)
(All of this will be in about 20 years).

Meanwhile, in about 5-7 years - addition of LIGO-India, and Japan - the sensitivity is going to be 10x, resulting 1000x times detecting of GW. Probably one event of so every day -- we may start mapping the universe using GW.


Wasn't there a proposal to build 3 sat system to detect GW..? I remember to have read about quite a few years ago. And as you already mentioned, the system will be ultra sensitive.

OK, googled for it- It LISA which was joint venture between NASA and ESA. Never really took off.

Nice gif showing proposed orbit.

https://en.wikipedia.org/wiki/File:LISA_motion.gif


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