Relativistic mass is a measure of the energy E of a particle, which changes with velocity.
As the wikipedia quote says, the prefered terminology for the mass of an object is its invariant mass, which is zero for a photon.
However, we can say that the photon has relativistic mass if we really want to.
One answer to the question "If light has no mass, how can it be deflected by the gravity of a star?" is that all particles, including photons, move in the curved spacetime of general relativity and the path they follow is independent of their mass.
I don't have the grasp of general relativity to find that answer particularly satisfying!Another answer is that light has energy and momentum which couples to gravity. This is apparently because "the energy-momentum 4-vector of a particle, rather than its mass, is the gravitational analogue of electric charge".
I don't have sufficient grasp of the mathematics to find that particularly satisfying either!Interestingly, the energy and momentum of light should also generate curvature of spacetime. Therefore, general relativity predicts that light will attract objects gravitationally. This effect is far too weak to have yet been measured.
The question of whether or not light has mass is partly concerned with semantics, as this full discussion, from which I've extracted the above information, suggests:
Does light have mass?
I am a great expert on General Relativity, having this week watched the ripping movie yarn known as "Interstellar"! 😀
Interstellar (film) - Wikipedia
Long story short, the Astronauts are seeking out new habitable planets since Planet Earth is undergoing some sort of environmental meltdown. Sounds familiar? The three most likely candidates are orbiting a spinning Black Hole known as Gargantua in another galaxy.
No plot twist is left unturned. Clocks speed up and down, and a wormhole near Saturn is navigated. The aliens have somehow mastered the Fifth Dimension, so regard time as a spatial co-ordinate. Naturally, Matthew McConaughy manipulates the whole sorry screenwriting mess into a satisfactory, if confusing conclusion. I was so bewildered by the physics, that I couldn't even fault it. 😀
Michael Caine had a nice role. My only criticism was that Sigourney Weaver and Sandra Bullock had no cameo Space roles. 😱
Tonight's main even is the Harvest Moon doing its "Shine On" thing. I took a snap of it next to Jupiter. On the way back I took a snap of the local council's complete muddle of lighting in the Avenue De Caen. Whatever were they thinking of? Where is the reduction in light pollution they promised me when canvassing my vote? 😕
Hope to move onto Quantum Chromodynamics shortly. A more satisfying theory of colours and the strong force, which the local council could learn a thing or two about.
Interstellar (film) - Wikipedia
Long story short, the Astronauts are seeking out new habitable planets since Planet Earth is undergoing some sort of environmental meltdown. Sounds familiar? The three most likely candidates are orbiting a spinning Black Hole known as Gargantua in another galaxy.
No plot twist is left unturned. Clocks speed up and down, and a wormhole near Saturn is navigated. The aliens have somehow mastered the Fifth Dimension, so regard time as a spatial co-ordinate. Naturally, Matthew McConaughy manipulates the whole sorry screenwriting mess into a satisfactory, if confusing conclusion. I was so bewildered by the physics, that I couldn't even fault it. 😀
Michael Caine had a nice role. My only criticism was that Sigourney Weaver and Sandra Bullock had no cameo Space roles. 😱
Tonight's main even is the Harvest Moon doing its "Shine On" thing. I took a snap of it next to Jupiter. On the way back I took a snap of the local council's complete muddle of lighting in the Avenue De Caen. Whatever were they thinking of? Where is the reduction in light pollution they promised me when canvassing my vote? 😕
Hope to move onto Quantum Chromodynamics shortly. A more satisfying theory of colours and the strong force, which the local council could learn a thing or two about.
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It appears that Interstellar may be languishing on a DVD I've recorded from the TV, as the plot does not stir my memory.
Here's what space.com has to say about the science: The Science of 'Interstellar': Black Holes, Wormholes and Space Travel | Space
Here's what space.com has to say about the science: The Science of 'Interstellar': Black Holes, Wormholes and Space Travel | Space
Interesting read here
Giant 'mega comet' up to 200 miles wide spotted making its way into our solar system
Hopefully I’m still around in 10 or 15 years to witness this!
Giant 'mega comet' up to 200 miles wide spotted making its way into our solar system
Hopefully I’m still around in 10 or 15 years to witness this!
Fortunately, mega comet Bernardinelli-Bernstein, as it is called, will not strike Earth. Its closest approach will be at the distance of the orbit of Saturn.
The largest comet previously known is Comet Sarabat, the "Great Comet of 1729", which was easily visible to the naked eye.
The largest comet previously known is Comet Sarabat, the "Great Comet of 1729", which was easily visible to the naked eye.
It probably won’t outgas (if it’s a comet) at that distance, but should make for some interesting discussions. Some of the comets that have come through over the last 30 years have had cores of only 5-10 kilometers in diameter, so only a fraction of B-B, but developed spectacular tails.
I checked!
On the 22nd June, Las Cumbres Observatory observed cometary activity at a distance of around 20AU and they produced a composite image which revealed a coma.
ATel #14733: Newly discovered object 2014 UN271 observed as active at 20.18 au
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I watched Neutrino: Hunting the Ghost Particle on BBC 4 tonight.
If you stayed the one hour course, you were rewarded with a glimpse of the IceCube Neutrino Observatory which is deployed in a cubic kilometre of ice at the South Pole and tasked with revealing unseen parts of the universe. IceCube to appear in BBC and PBS documentaries - IceCube
Then we were schooled about sterile neutrinos, theoretically predicted particles that offer an intriguing possibility in the quest for understanding dark matter. The search for the sterile neutrino | symmetry magazine
If you stayed the one hour course, you were rewarded with a glimpse of the IceCube Neutrino Observatory which is deployed in a cubic kilometre of ice at the South Pole and tasked with revealing unseen parts of the universe. IceCube to appear in BBC and PBS documentaries - IceCube
Then we were schooled about sterile neutrinos, theoretically predicted particles that offer an intriguing possibility in the quest for understanding dark matter. The search for the sterile neutrino | symmetry magazine
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I have certainly been following the Autumn Equinox with great interest. Though I have little patience for ancient Druids or old sects. Modern Druids must far prefer the LHC to instruments like Stonehenge. Nor do they wear beards, which are scruffy IMO. You can't live in the past! 😀
I was struck by the resemblance between the Chief Druid's and Professor Leonard Susskind's beards. Below.
Are they by any chance related? As we all know, the Stonehenge astronomical calculator is now operated by the wretched "English Heritage" organization who are content to run it into the ground without adequate maintenance. Half the capstones are missing! £15 a visit too? Really... 😱
To me, what is interesting about the Equinoxes is that the Sun at Noon falls on the exact hour on those days. A fact that was discovered by the Scottish Physicist Galu:
Naturally I have been out and about to scientifically investigate this current Mabon/Green Man/Harvest Moon stuff.
A more revealing view is below. You doubtless wondered what the silhoetted 2001-like black obelisk is. It seems to attract weird messages from the mentally disturbed!
Anecdotally, the Full Moon fell on 12.47AM, Sept 21. The next high tide was 12.48PM! Exactly when I was swimming. 😱
A man I met told me his wife had been swimming naked with the girlfriends on Sept. 20 for some related reason. He himself was planning on swimming on Sept 21 at 6.30AM. They are in my Tai Chi class, so I shall ask him what he concluded next week. My notion is that this clearly proves the Full Moon drives people mad. QED!
I will get back to the "Interstellar" movie in due course. A shockingly bad piece of work IMO. 5 dimensions just doesn't work:
Kaluza–Klein theory - Wikipedia
I was struck by the resemblance between the Chief Druid's and Professor Leonard Susskind's beards. Below.
Are they by any chance related? As we all know, the Stonehenge astronomical calculator is now operated by the wretched "English Heritage" organization who are content to run it into the ground without adequate maintenance. Half the capstones are missing! £15 a visit too? Really... 😱
To me, what is interesting about the Equinoxes is that the Sun at Noon falls on the exact hour on those days. A fact that was discovered by the Scottish Physicist Galu:
Naturally I have been out and about to scientifically investigate this current Mabon/Green Man/Harvest Moon stuff.
A more revealing view is below. You doubtless wondered what the silhoetted 2001-like black obelisk is. It seems to attract weird messages from the mentally disturbed!
Anecdotally, the Full Moon fell on 12.47AM, Sept 21. The next high tide was 12.48PM! Exactly when I was swimming. 😱
A man I met told me his wife had been swimming naked with the girlfriends on Sept. 20 for some related reason. He himself was planning on swimming on Sept 21 at 6.30AM. They are in my Tai Chi class, so I shall ask him what he concluded next week. My notion is that this clearly proves the Full Moon drives people mad. QED!
I will get back to the "Interstellar" movie in due course. A shockingly bad piece of work IMO. 5 dimensions just doesn't work:
Kaluza–Klein theory - Wikipedia
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I saw on the telly a few days ago that they were cementing capstones in place at Stonehenge.
I think they were last secured some decades ago.
I think they were last secured some decades ago.
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Puts on investigative hat:
I am aware of this latest folly by English Heritage. This shows what utter buffoons they are. Why would replacing old cement with lime mortar be appropriate? Maybe on an old country mansion, but hardly appropriate for a 5,000 year old Druidic construct. 😕
The Romans invented cement and concrete. The ancient Druids relied on dry stone construction. I know about English Heritage, and am deeply suspect of an organisation that has its headquarters in a pentagonal construct in Portsmouth. It screams "Occult" to me.
I have spent much undercover time at Fort Cumberland, and discovered it is guarded by hissing Dragons! A story I may relate if pressed. 😱
My ancient ancestor, The Revd. William Ponsford (Pauncefoote) of Drewsteignton (Druid's Teign Town), Devon was a more C19 serious preserver of Menhirs and Dolmens in the local environs of this mysterious village. He made it his mission to re-erect them on Dartmoor. I discovered this whilst reading the tourist guide while having a beer in the local Drewe Arms (Druid's Arms) pub. Surprisingly, his church yard has many graves of Pauncefootes.
Back on-topic, King Arthur's Round Table is preserved at another mystical spot, Winchester. You know, "Sir Gawayne and the Green Knight" and all that. The location of Camelot has also been uncovered in the course of my tireless investigations. It is at a hillfort above Compton Pauncefoote in Somerset, near the River Camel. 😎
Today's mission on my way back from swimming and the bookies, is to investigate further the mysterious obelisk near Southsea bandstand:
I shall take a notebook to find the messages and a camera. You must be curious too! 🙂
I am aware of this latest folly by English Heritage. This shows what utter buffoons they are. Why would replacing old cement with lime mortar be appropriate? Maybe on an old country mansion, but hardly appropriate for a 5,000 year old Druidic construct. 😕
The Romans invented cement and concrete. The ancient Druids relied on dry stone construction. I know about English Heritage, and am deeply suspect of an organisation that has its headquarters in a pentagonal construct in Portsmouth. It screams "Occult" to me.
I have spent much undercover time at Fort Cumberland, and discovered it is guarded by hissing Dragons! A story I may relate if pressed. 😱
My ancient ancestor, The Revd. William Ponsford (Pauncefoote) of Drewsteignton (Druid's Teign Town), Devon was a more C19 serious preserver of Menhirs and Dolmens in the local environs of this mysterious village. He made it his mission to re-erect them on Dartmoor. I discovered this whilst reading the tourist guide while having a beer in the local Drewe Arms (Druid's Arms) pub. Surprisingly, his church yard has many graves of Pauncefootes.
Back on-topic, King Arthur's Round Table is preserved at another mystical spot, Winchester. You know, "Sir Gawayne and the Green Knight" and all that. The location of Camelot has also been uncovered in the course of my tireless investigations. It is at a hillfort above Compton Pauncefoote in Somerset, near the River Camel. 😎
Today's mission on my way back from swimming and the bookies, is to investigate further the mysterious obelisk near Southsea bandstand:
I shall take a notebook to find the messages and a camera. You must be curious too! 🙂
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That's another one of your 'black cat in a coal cellar' photographs, Steve, but I can just make out the red glow of those mysterious messages.
Regarding the "hissing dragons", I fear you may be spending too much time touring the Portsmouth Distillery which has made its home within Fort Cumberland! 🙂
Fort Cumberland Gin - Google Search
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I have to be careful what I say, but IMO anything coming out of Pentagram-shaped Fort Cumberland is deeply suspect!
I never noticed a Gin Distillery there on my investigations. And to market a product called Fort Cumberland 1968 is a clear attempt to defraud the public. It was brewed and distilled somewhere else IMO. Probably Southampton.
I am friendly with the Fort Cumberland Guard who are old re-enactment Soldiers. I learned a great deal about firing cannons from them whilst enjoying Tea and Biscuits in their Hide.
Back to the Obelisk. Actually an electrical junction box to power poor but free musical performances at Southsea Bandstand. They attract the worst kind of crazy people. Vegans, Anti-Vaxxers, Animal Rights Activists. And the worst thing is they have to tell you all about it!
Messages on the Obelisk:
Anywhoo. A good day.
Swimming: Done!
Bookies: Horse "Nayef Road" came in at 9/2!
Nayef Road (IRE) | Horse Profile | Sky Sports Horse Racing
Investigations: Charlatans and crazies exposed!
What's not to like?
p.s. You may laugh at my story about hissing Dragons at Fort Cumberland, but you were not there when I, alone onsite, saw two glowing eyes staring at me, accompanied by a hissing noise! 😱
I never noticed a Gin Distillery there on my investigations. And to market a product called Fort Cumberland 1968 is a clear attempt to defraud the public. It was brewed and distilled somewhere else IMO. Probably Southampton.
I am friendly with the Fort Cumberland Guard who are old re-enactment Soldiers. I learned a great deal about firing cannons from them whilst enjoying Tea and Biscuits in their Hide.
Back to the Obelisk. Actually an electrical junction box to power poor but free musical performances at Southsea Bandstand. They attract the worst kind of crazy people. Vegans, Anti-Vaxxers, Animal Rights Activists. And the worst thing is they have to tell you all about it!
Messages on the Obelisk:
Anywhoo. A good day.
Swimming: Done!
Bookies: Horse "Nayef Road" came in at 9/2!
Nayef Road (IRE) | Horse Profile | Sky Sports Horse Racing
Investigations: Charlatans and crazies exposed!
What's not to like?
p.s. You may laugh at my story about hissing Dragons at Fort Cumberland, but you were not there when I, alone onsite, saw two glowing eyes staring at me, accompanied by a hissing noise! 😱
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The secret of the mysterious obelisk has been revealed. We have got the message(s)! 😀
I'd ask to hear more about those "glowing eyes", but fear the story may 'drag on'! 😉
I'd ask to hear more about those "glowing eyes", but fear the story may 'drag on'! 😉
OK, long story short. The hissing noise tormented and disturbed me for days. Sounded like a relief valve on a compressed air device, and hard to locate. Eventually I pointed my torch 12 feet upwards.
It was a nesting baby Wol! I checked on Wikipedia, and to my surprise learned the grown Wols go "Hoot" and "Too Whit Too Whoo" and all that, babies hiss for Mama Wol when alarmed.
Doubtless imitating Dragons to deter Foxes and Humans too. Cunning, eh? 😎
I do want to move on to Quantum Chromodynamics now. A gentle introduction to some most interesting symmetry considerations.
First we need to understand octagonal symmetry. Something exhibited by a Radar Reflector on a yacht. Three squares of metal at 90 degrees produces all the 8-fold symmetry we need.
Secondly, we need to understand the three primary colours, Red Green and Blue.
Because we also need anti-Red, anti-Green and anti-Blue, we must also understand the complimentary colours Cyan, Magenta and Yellow.
This will explain Mesons and Baryons. Particularly the Pion involved in the Strong Force between Baryons. The interested student will now get up to speed on the Primary and Complimentary colours before the next episode.
It was a nesting baby Wol! I checked on Wikipedia, and to my surprise learned the grown Wols go "Hoot" and "Too Whit Too Whoo" and all that, babies hiss for Mama Wol when alarmed.
Doubtless imitating Dragons to deter Foxes and Humans too. Cunning, eh? 😎
I do want to move on to Quantum Chromodynamics now. A gentle introduction to some most interesting symmetry considerations.
First we need to understand octagonal symmetry. Something exhibited by a Radar Reflector on a yacht. Three squares of metal at 90 degrees produces all the 8-fold symmetry we need.
Secondly, we need to understand the three primary colours, Red Green and Blue.
Because we also need anti-Red, anti-Green and anti-Blue, we must also understand the complimentary colours Cyan, Magenta and Yellow.
This will explain Mesons and Baryons. Particularly the Pion involved in the Strong Force between Baryons. The interested student will now get up to speed on the Primary and Complimentary colours before the next episode.
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Yes, all good so far. I am winging it a bit at the moment. How hard can it be?
Quark model - Wikipedia
We are looking at SU(3) symmetry here, which surprises us by giving eight solutions, not 9.
Gluon - Wikipedia
Unitary Matrices have a determinant of magnitude one, so associate with rotations or reflections in three planes if I understand.
All done with mirrors...
I was going to buy three shaving mirrors at Boots to do experiments before this lockdown business scuppered the idea. Maybe tomorrow! 😀
Quark model - Wikipedia
We are looking at SU(3) symmetry here, which surprises us by giving eight solutions, not 9.
Gluon - Wikipedia
Unitary Matrices have a determinant of magnitude one, so associate with rotations or reflections in three planes if I understand.
All done with mirrors...
I was going to buy three shaving mirrors at Boots to do experiments before this lockdown business scuppered the idea. Maybe tomorrow! 😀
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