The electromagnetic radiation captured from 130 million light year distant galaxy GW170817 now confirms that elements heavier than iron are synthesised in the aftermath of neutron star collisions.
Here's an interesting periodic table which shows the origin of each of the elements:
The full story of the detection of cosmic gold may be read here: https://www.caltech.edu/about/news/caltech-led-teams-strike-cosmic-gold-80074
Here's an interesting periodic table which shows the origin of each of the elements:
The full story of the detection of cosmic gold may be read here: https://www.caltech.edu/about/news/caltech-led-teams-strike-cosmic-gold-80074
There's a horse going in the 1.40 at Newmarket today: Invictus Gold! 
To avert squabbling about who gets the prize here, and I am thinking about @Galu particularly, I have rethought my Quiz format.
Splendid Nunthorpe 5f Sprint victory yesterday by Hollie Doyle on the "back from the dead" horse Bradsell at 3-1:
https://www.theguardian.com/sport/a...s-hollie-doyle-bradsell-nunthorpe-racing-tips
Bradsell hit an impressive 42mph and 57.4s, but did not threaten the mighty Battaash's York Course Record.
I was surprised, and so no doubt were you. Perhaps Hollie should pack some sandwiches and a few carrots. For later.
To avert squabbling about who gets the prize here, and I am thinking about @Galu particularly, I have rethought my Quiz format.
Splendid Nunthorpe 5f Sprint victory yesterday by Hollie Doyle on the "back from the dead" horse Bradsell at 3-1:
https://www.theguardian.com/sport/a...s-hollie-doyle-bradsell-nunthorpe-racing-tips
Bradsell hit an impressive 42mph and 57.4s, but did not threaten the mighty Battaash's York Course Record.
8 Months.
64 Million Years.
I was surprised, and so no doubt were you. Perhaps Hollie should pack some sandwiches and a few carrots. For later.
To avert squabbling about who gets the prize here, and I am thinking about @Galu particularly, I have rethought my Quiz format.
There was no quiz and there was no prize. You simply got it wrong and can't admit it!
P.S. If I were interested in horse racing, I could get my fill over on your 'Brilliancy in Sport' thread:
https://www.diyaudio.com/community/threads/brilliancy-in-sport-your-favourite-moments.356611/page-44
It's a case of horses for courses!
I was interested in why elements 43 (Technetium) and 61 (Promethium) in the above periodic table (post #4,741) are only shown in grey.
I read that Technetium was detected in light from S-type red giant stars which indicated it was being produced in the stars by nuclear fusion.
Promethium has been identified in the spectrum of the star GY Andromedae and is thought to be be generated by the spontaneous fission of higher mass transuranic elements near the surface of this most peculiar star.
I followed this trail: https://en.wikipedia.org/wiki/Technetium, https://en.wikipedia.org/wiki/Promethium and https://en.wikipedia.org/wiki/GY_Andromedae
I read that Technetium was detected in light from S-type red giant stars which indicated it was being produced in the stars by nuclear fusion.
Promethium has been identified in the spectrum of the star GY Andromedae and is thought to be be generated by the spontaneous fission of higher mass transuranic elements near the surface of this most peculiar star.
I followed this trail: https://en.wikipedia.org/wiki/Technetium, https://en.wikipedia.org/wiki/Promethium and https://en.wikipedia.org/wiki/GY_Andromedae
Learning all the time! https://en.wikipedia.org/wiki/Technetium_star
The s-process (slow neutron-capture process) is involved in the production of Technetium - not to be confused with the r-process (rapid neutron-capture process) mentioned earlier. https://en.wikipedia.org/wiki/S-process#The_s-process_in_stars
Note: A simple explanation of why 43Tc and 61Pm are greyed out my periodic table (post #4,741) is that they were first created artificially (and only later found in nature in trace quantities). Technetium, for example, was created in 1937.
The s-process (slow neutron-capture process) is involved in the production of Technetium - not to be confused with the r-process (rapid neutron-capture process) mentioned earlier. https://en.wikipedia.org/wiki/S-process#The_s-process_in_stars
Note: A simple explanation of why 43Tc and 61Pm are greyed out my periodic table (post #4,741) is that they were first created artificially (and only later found in nature in trace quantities). Technetium, for example, was created in 1937.
I was regretting the loss of my stellar evolution textbook from 1970 in a move 1983. Now I see it was no loss. Totally obsolete.
I suppose this winter I should replace the quantum mechanics text that was lost at the same time. Psi=Chi*Phi. They do not even write the equation the same way anymore. Perhaps I will learn why Euler equations were so key to completing my unfinished homework.
Indeed, our knowledge has greatly expanded since 1970.
Here are the confidence levels we have (as of Aug 2020) regarding our knowledge of the origin of the elements:
Certain
The Big Bang created the lightest elements
Stars fuse nuclei to form new elements
Supernovae make new elements
Dying low-mass stars make heavy elements
High confidence
Cosmic rays make most of the Li, B and Be in the Universe
Medium confidence
Slow and rapid neutron capture processes make 99% of the heavy elements
Merging neutron stars make the majority of r-processed material
Novae contribute important amounts of some isotopes
Low confidence
All processes that form elements in stars have been identified
Strictly for the enthusiast, herein are the details: https://royalsocietypublishing.org/doi/10.1098/rsta.2019.0301
Here are the confidence levels we have (as of Aug 2020) regarding our knowledge of the origin of the elements:
Certain
The Big Bang created the lightest elements
Stars fuse nuclei to form new elements
Supernovae make new elements
Dying low-mass stars make heavy elements
High confidence
Cosmic rays make most of the Li, B and Be in the Universe
Medium confidence
Slow and rapid neutron capture processes make 99% of the heavy elements
Merging neutron stars make the majority of r-processed material
Novae contribute important amounts of some isotopes
Low confidence
All processes that form elements in stars have been identified
Strictly for the enthusiast, herein are the details: https://royalsocietypublishing.org/doi/10.1098/rsta.2019.0301
I’ve been reading Fukujita and Peebles ‘Cosmic Energy Inventory’. Ignoring dark energy and dark matter, I am struck by now little mass is bound up in stellar objects. Ignoring everything below black holes in the 3rd section below, all stellar objects account for just .00745 of the cosmos’ mass (ie .745%). Warm intergalactic plasma accounts for 4% and all other forms of energy are about 0.25% roughly speaking. Seems to me the cosmos is a whole lot of nothing, and going back to our ‘water universe’ discussion a few months ago, supports the conclusion I drew that there was remarkably little baryonic matter distributed across the cosmos.
https://arxiv.org/abs/astro-ph/0406095
https://arxiv.org/abs/astro-ph/0406095
I notice the figures in the inventory are based on a Hubble parameter of h = 0.7, a figure upon which the critical density needed to overcome the expansion of the Universe depends.
As you've mentioned before, the critical density is roughly 10^-26 kg/m3, equivalent to 4 or 5 hydrogen atoms in a cubic metre of space.
This is analogous to the density obtained by distributing a grain of sand over the volume of the Earth. Yes, the Universe is fantastically empty!
We haven't heard from Steve since Saturday.
He may have a greater than expected sensitivity to criticism, in which case I regret the strict tone of my reply to him.
I didn't like the wording of the final sentence in my above post, so I'm re-writing it below.
"This is analogous to the density that would result from distributing the atoms in a grain of sand throughout a volume equal to that occupied by the Earth."
That's my mild OCD talking! My father had it worse. Everything in his house had to be spick and span and in its place. One time he whisked my plate from under my nose in order to wash it, even though I was still eating the food off it!
Elsewhere, the wonders of our Milky Way galaxy continue to unfold:
The supergiant rich cluster Barbá 2.
The Gaia space telescope has revealed that a 24,000 light-year distant star cluster is packed with red supergiant stars that can be hundreds of times the diameter of the Sun and up to 1,000,000 times as luminous as the Sun.
Apparently such clusters are very rare and tend to be very far away, but they play a crucial role in understanding key aspects in the evolution of massive stars. https://www.space.com/milky-way-supermassive-stars-open-cluster
He may have a greater than expected sensitivity to criticism, in which case I regret the strict tone of my reply to him.
I didn't like the wording of the final sentence in my above post, so I'm re-writing it below.
"This is analogous to the density that would result from distributing the atoms in a grain of sand throughout a volume equal to that occupied by the Earth."
That's my mild OCD talking! My father had it worse. Everything in his house had to be spick and span and in its place. One time he whisked my plate from under my nose in order to wash it, even though I was still eating the food off it!
Elsewhere, the wonders of our Milky Way galaxy continue to unfold:
The supergiant rich cluster Barbá 2.
The Gaia space telescope has revealed that a 24,000 light-year distant star cluster is packed with red supergiant stars that can be hundreds of times the diameter of the Sun and up to 1,000,000 times as luminous as the Sun.
Apparently such clusters are very rare and tend to be very far away, but they play a crucial role in understanding key aspects in the evolution of massive stars. https://www.space.com/milky-way-supermassive-stars-open-cluster
It would appear that space.com is incorrect in referring in their article title to an "open cluster" in relation to the super massive stars.
Apparently there are eleven thousand open star clusters in the Milky Way so those could not be described as 'rare'.
Open clusters are "loosely bound by gravity" or "unstably bound together", meaning that the velocity needed to escape a cluster's gravity is less than the velocity of the stars it contains. Open clusters survive a few orbits of the galaxy before their stars begin to diffuse away.
That and additional information on open clusters may be found here: https://astrobackyard.com/open-star-clusters/
The Pleiades (or Seven Sisters) shown above is an example of an Open Cluster.
Apparently there are eleven thousand open star clusters in the Milky Way so those could not be described as 'rare'.
Open clusters are "loosely bound by gravity" or "unstably bound together", meaning that the velocity needed to escape a cluster's gravity is less than the velocity of the stars it contains. Open clusters survive a few orbits of the galaxy before their stars begin to diffuse away.
That and additional information on open clusters may be found here: https://astrobackyard.com/open-star-clusters/
The Pleiades (or Seven Sisters) shown above is an example of an Open Cluster.
... "theoretical physicist Claudia de Rham explains her work on an alternative explanation called “massive gravity” to host Janna Levin.
"In some sense, I’m studying gravity because it’s possibly the simplest thing you can ever study."
//
Do We Need a New Theory of Gravity?
"In some sense, I’m studying gravity because it’s possibly the simplest thing you can ever study."
//
Thanks TNT, your link contains a comprehensive discussion on the nature of gravity.
Claudia's book is entitled "The Beauty of Falling".
Consider a satellite that is falling around the Earth under the influence of gravity.
Newton described gravity as a force between the mass of the Earth and the mass of the satellite.
Then along came Einstein who explained that the real cause of gravity was the fact that the two masses curve spacetime.
So far, so familiar!
However, we now appear to enter the realms of quantum gravity with Claudia's claim that Einstein’s theory breaks down at a particle level. This has led her to develop a new hypothesis of “Massive Gravity”.
So what is "Massive Gravity"? Apparently it is the hypothesis that a graviton (the force carrier of quantum gravity) could actually have mass.
This hypothesis seems to rely on the possibility that "hidden particles" may exist undetected alongside our known world of particles.
I've written in the past that "hidden particles" are contrary to the laws of physics, but are necessary to maintain the integrity of the Standard Model.
Claudia's book is entitled "The Beauty of Falling".
Consider a satellite that is falling around the Earth under the influence of gravity.
Newton described gravity as a force between the mass of the Earth and the mass of the satellite.
Then along came Einstein who explained that the real cause of gravity was the fact that the two masses curve spacetime.
So far, so familiar!
However, we now appear to enter the realms of quantum gravity with Claudia's claim that Einstein’s theory breaks down at a particle level. This has led her to develop a new hypothesis of “Massive Gravity”.
So what is "Massive Gravity"? Apparently it is the hypothesis that a graviton (the force carrier of quantum gravity) could actually have mass.
This hypothesis seems to rely on the possibility that "hidden particles" may exist undetected alongside our known world of particles.
I've written in the past that "hidden particles" are contrary to the laws of physics, but are necessary to maintain the integrity of the Standard Model.
I've been finding out a bit more about Claudia de Rham's new theory (actually just a hypothesis) of Massive Gravity.
The problem is that the rate of expansion of the Universe is speeding up, which Einstein's theory predicts should not be happening.
De Rham's solution to the problem is to make a change to Einstein’s theory of general relativity. Instead of assuming that gravitons are massless, as Einstein did, she suggests that they do have some mass.
If gravitons have a mass, then gravity is expected to have a weaker influence on very large distance scales, explaining why the acceleration is happening and eliminating the need for Dark Energy.
She is hopeful that advances in gravitational wave astronomy will make it possible to test the predictions of Massive Gravity within the decade.
More here: https://www.theguardian.com/science...y-theory-solved-impossible-dark-energy-riddle
The problem is that the rate of expansion of the Universe is speeding up, which Einstein's theory predicts should not be happening.
De Rham's solution to the problem is to make a change to Einstein’s theory of general relativity. Instead of assuming that gravitons are massless, as Einstein did, she suggests that they do have some mass.
If gravitons have a mass, then gravity is expected to have a weaker influence on very large distance scales, explaining why the acceleration is happening and eliminating the need for Dark Energy.
She is hopeful that advances in gravitational wave astronomy will make it possible to test the predictions of Massive Gravity within the decade.
More here: https://www.theguardian.com/science...y-theory-solved-impossible-dark-energy-riddle
Here's a question that came up when I was thinking about Einstein's equivalence principle:-
Imagine two atomic clocks X and Y of equal mass coasting along in close proximity in flat space-time. The clocks are initially synchronised to each other and read the same time, the light time difference between them notwithstanding; a very distant observer would see the same time on both clocks.
A force is applied to X and it accelerates away from Y. Since everything is relative, it is just as acceptable to say that Y is accelerating away from X if we choose X as the reference.
My question is, on the accelerated clock X, it will feel 'weight' during acceleration, but if we turn things around and consider X as the reference so that it is Y that is moving away rapidly, does Y feel weight during the acceleration phase?
I'm erring on the side of time is relative, but not inertia (what the X clock body feels while being accelerated).
Imagine two atomic clocks X and Y of equal mass coasting along in close proximity in flat space-time. The clocks are initially synchronised to each other and read the same time, the light time difference between them notwithstanding; a very distant observer would see the same time on both clocks.
A force is applied to X and it accelerates away from Y. Since everything is relative, it is just as acceptable to say that Y is accelerating away from X if we choose X as the reference.
My question is, on the accelerated clock X, it will feel 'weight' during acceleration, but if we turn things around and consider X as the reference so that it is Y that is moving away rapidly, does Y feel weight during the acceleration phase?
I'm erring on the side of time is relative, but not inertia (what the X clock body feels while being accelerated).
When the unbalanced force is applied to X it will accelerate away from Y and gain speed.
Since no unbalanced force has been applied to Y it will not accelerate and will continue moving at its original speed.
These two situations are surely not equivalent.
Unlike X, Y has no change in motion to oppose, so will not exhibit "inertia" or experience "weight".