In Our Time with Melvyn Bragg (Radio 4)

#1
++ The whole archive of In Our Time is now available to download here: BBC - Radio 4 - In Our Time - Podcasts ++



It's high time we had a thread dedicated to In Our Time with Melvyn Bragg (Radio 4).


As far as I'm concerned this is the best show on the radio and for those of you who aren't familiar I strongly recommend listening, the subjects are diverse as they are fascinating. The only other series I have come across which is similar is from The Teaching Company, but that’s not really a radio show and I honestly can’t fathom why the rest of the world hasn’t done something similar with authorities from Harvard or Copenhagen etc.


See here for the main site:
BBC - Radio 4 - In Our Time - Homepage


Archive for History:
BBC - Radio 4 - In Our Time - Archive by Genre: History - page 1


Archive for Culture:
BBC - Radio 4 - In Our Time - Archive by Genre: Culture - page 1


Archive for Philosophy:
BBC - Radio 4 - In Our Time - Archive by Genre: Philosophy - page 1


Archive for Religion:
BBC - Radio 4 - In Our Time - Archive by Genre: Religion - page 1


Archive for Science:
BBC - Radio 4 - In Our Time - Archive by Genre: Science - page 1


It would be great to discuss some of the subjects covered in more detail, perhaps we can listen to each show as it comes or just pick one of particular interest?


I'd also like to note that the entire series is available to download so you can listen to them all on an MP3 player or your phone etc which is invaluable for those who commute, but naturally I can't really post the details on a public forum. (Google and torrent is your friend but should you require further info just pm).


I'd like to get things rolling with this episode: The Speed of Light.
BBC - BBC Radio 4 Programmes - In Our Time, The Speed of Light


DC
 
#2
It's high time we had a thread dedicated to In Our Time with Melvyn Bragg (Radio 4).


As far as I'm concerned this is the best show on the radio and for those of you who aren't familiar I strongly recommend listening, the subjects are diverse as they are fascinating. The only other series I have come across which is similar is from The Teaching Company, but that’s not really a radio show and I honestly can’t fathom why the rest of the world doesn’t hasn’t done something similar with authorities from Harvard or Copenhagen etc.


See here for the main site:
BBC - Radio 4 - In Our Time - Homepage


Archive for History:
BBC - Radio 4 - In Our Time - Archive by Genre: History - page 1


Archive for Culture:
BBC - Radio 4 - In Our Time - Archive by Genre: Culture - page 1


Archive for Philosophy:
BBC - Radio 4 - In Our Time - Archive by Genre: Philosophy - page 1


Archive for Religion:
BBC - Radio 4 - In Our Time - Archive by Genre: Religion - page 1


Archive for Science:
BBC - Radio 4 - In Our Time - Archive by Genre: Science - page 1


It would be great to discuss some of the subjects covered in more detail, perhaps we can listen to each show as it comes or just pick one of particular interest?


I'd also like to note that the entire series is available to download so you can listen to them all on an MP3 player or your phone etc which is invaluable for those who commute, but naturally I can't really post the details on a public forum. (Google and torrent is your friend but should you require further info just pm).


I'd like to get things rolling with this episode: The Speed of Light.
BBC - BBC Radio 4 Programmes - In Our Time, The Speed of Light


DC
Quality DC... hope it takes off. I'll brb...
 
#3
Right... I can now advise the entire world all about light...what it is, how it works and where to buy the lamps.

The stuff that light travels through is much more interesting though... anyone want to know?
 
#4
You mean the reference to empty space or water?

I was quite interested by the fantastic claims of the tachyon, more info about that here:

Faster-than-light 'tachyons' might be impossible after all - space - 18 March 2009 - New Scientist

Faster-than-light particles, or "tachyons", may be fundamentally impossible, according to two mathematical physicists. If they're right, their new theory would also imply that time – seemingly one of the most fundamental facets of nature – is no more than a mirage.

Although it is commonly believed that Einstein's theory of relativity says nothing can go faster than light, that is not quite true. Relativity does forbid ordinary matter from ever reaching the speed of light, because it would require infinite energy.

But the theory does not rule out a realm of particles that can only travel faster than light. Named "tachyons" by physicists in the 1960s, these subatomic speedsters would actually need an infinite amount of energy to slow down to the crawl of light-speed.

Tachyons crop up as possibilities in several speculative physical theories, such as some versions of string theory. Physicists have searched for their expected signatures. If they are among the high-energy particles that hit Earth from space, tachyons would produce a signal similar to cosmic rays – except that they would reach ground-based detectors ahead of the secondary particles they created in the atmosphere.

No tachyons have ever been detected, however, and now James Wheeler and Joseph Spencer of Utah State University think they know why.
Abstract space

Their line of reasoning is subtle. "We've been embroiled in this calculation for one-and-a-half years," says Wheeler. The pair wanted to understand how physical models are related to the measurements we make.

They started by imagining a universe that only has distances, with no time dimension. The simplest measurement in this universe is to compare two distances: and a one-metre stick should be half the length of a two-metre stick, no matter what your point of view, whether you look from a different angle or a different place.

All these points of view form a more complex abstract space, the "space of measurement symmetries".
Light cone

Mathematically, this turns out to look a lot like "phase space", which is at the heart of quantum mechanics and other physical theories. Phase space describes not only the position of an object, but also its momentum - loosely, the object's trajectory.

In their model, all the trajectories get bundled up into two cones meeting at a point. It looks like one set of trajectories coming in from the past, passing through a point at the present, and heading out again into the future. Something equivalent to time has emerged.

In fact, this bundle of trajectories mimics the "light cone" of relativity, traced out by the paths in space-time of particles travelling up to and including the speed of light. The light cone also divides past from future.

In relativity, it is possible to conceive of tachyons, travelling outside the light cone. But in Wheeler and Spencer's model, that is inconceivable, since the cone is actually defined by the set of all possible trajectories.
Emerging time

Why should their complicated space of symmetries have any relevance to the "real" space and time that we inhabit? The reason is that it links timeless space to something like our familiar space-time, meaning that these two descriptions are equivalent. Any events that can be described in the space-time picture can be modelled just as well by a structure in timeless space.

The consequences could be profound. The timeless space can't change, so that could mean that our universe is deterministic, with the future set in stone.

Wheeler suspects that our perceived "time" corresponds to the distance from a special point in the four-dimensional timeless space he modelled. If so, that point might mark the apparent beginning of time at the big bang.

Mathematician Shahn Majid of Queen Mary, University of London, also works on the question of how time could emerge from timelessness.

He believes that Wheeler and Spencer's result is limited, because it depends on a particular mathematical approach. But he doesn't dismiss the work. "It's suggestive, and gives the right answer [that time emerges]," he told New Scientist. "And there are now several approaches to this question, which could all tie up. There seems to be an emerging theory of emerging time."




DC
 
#5
You mean the reference to empty space or water?

I was quite interested by the fantastic claims of the tachyon, more info about that here:

Faster-than-light 'tachyons' might be impossible after all - space - 18 March 2009 - New Scientist

DC
I can visualise the fabric of existence being everywhere, infinite and eternal...time is static. Imagine a block of this stuff...as light appears to pass through it like a wave or as a single particle, it is rather like flotsam becoming visible on the crests and then sinking down out of sight. The photons actually travel nowhere...the wave just exposes what is there hidden or switched off. So everything, matter and energy is in some way connected and pops into existence according to forces like wind from within the void...

Tachyons are probably the theoretical way of expressing stimuli across space as if connected by string... push or pull in any dimension and it has an instant effect... What appears to be movement is the illusion...the waves simply change the infinite states of potential at any point within the existence stuff...ok?

I'm just going to nip back to my shed to check the maths.... brb.... :)

.....distance in this model is meaningless.
 
#6
I can visualise the fabric of existence being everywhere, infinite and eternal...time is static. Imagine a block of this stuff...as light appears to pass through it like a wave or as a single particle, it is rather like flotsam becoming visible on the crests and then sinking down out of sight. The photons actually travel nowhere...the wave just exposes what is there hidden or switched off. So everything, matter and energy is in some way connected and pops into existence according to forces like wind from within the void...

Tachyons are probably the theoretical way of expressing stimuli across space as if connected by string... push or pull in any dimension and it has an instant effect... What appears to be movement is the illusion...the waves simply change the infinite states of potential at any point within the existence stuff...ok?

I'm just going to nip back to my shed to check the maths.... brb.... :)

.....distance in this model is meaningless.

Pretty deep stuff, so you're suggesting that light plays an important role in the existence of matter and if there were no light waves there wouldn't be any matter either?

One of the most interesting parts I found was the life extension of particles travelling close to the speed of light. I have The In Our Time book with full texts from the conversations, I'll see if it's in there.

DC
 
#7
Time travel to the future is uncontroversial and we see these effects of time travel to the future almost on a daily basis in particle accelerators, so if you accelerate elementary particles their lifetimes will change compared with the lifetimes of particles that sit still and are not accelerated.

At this moment there are cosmic ray nuons that are passing through us at quite high speeds and hitting the earth everywhere. If Einstein's picture of space and time were not true we would not see these particles. They're made high up in the top of the earth's atmosphere when cosmic rays hit the top of the atmosphere and they move very, very close to the speed of light but they only live for a microsecond or so, so should decay long before they ever reach the earth's surface. They should only travel 600 metres, but they manage to travel 6,000 metres and reach the earth's surface and the reason is because their clocks go slow. They live longer because they're moving at such high speed, or equivalently the distance that they're travelling from the atmosphere to the surface is contracted by relativistic effects. So these transformations of length and time in order to keep their ratio of the speed of light the same for everybody are things that you see on a regular and routine basis.
Interesting.

DC
 
#8
The speed of light and the concept of time seem to me to be part of what is only a human viewpoint on existence. We are trapped in a dimension that appears to work in a particular way but we could be reading it all wrong...

Infinite layers and possibilities exist within the fabric of what we call space/time... Black holes are random points in this fabric that are sucking stuff back into 'nothingness'... where the laws of physics break down into the unknown. Time, speed and size may have no meaning. Perhaps exceeding the speed of light also penetrates this barrier...one would disappear into the void.

My dog has volunteered for a high speed experiment in our tumble drier, the drum is geared to the rear wheel of a Volvo so it should be possible to accelerate him out of this existence....The time machine is patent pending.
 
#9
The speed of light and the concept of time seem to me to be part of what is only a human viewpoint on existence. We are trapped in a dimension that appears to work in a particular way but we could be reading it all wrong...

Infinite layers and possibilities exist within the fabric of what we call space/time... Black holes are random points in this fabric that are sucking stuff back into 'nothingness'... where the laws of physics break down into the unknown. Time, speed and size may have no meaning. Perhaps exceeding the speed of light also penetrates this barrier...one would disappear into the void.

My dog has volunteered for a high speed experiment in our tumble drier, the drum is geared to the rear wheel of a Volvo so it should be possible to accelerate him out of this existence....The time machine is patent pending.
Remember it must spin the opposite way to the earth to go back in time and the same way as the earth but faster to go forward, might be a good idea to rig it all up to the mains too to create an electromagnetic field. Have you had the machine blessed by the appropriate faiths? Wouldn't want to sacrifce fido or send him into low level orbit without the conscent of the Egyptian Dog God, perhaps he might even team up with Laika?

Sounds like you're describing the Ether, the fabric of space/time is rather a good subject for our next podcast, but it also has a lot in common with the speed of light so we can keep that general convo going too.

The Vacuum of Space:
BBC - BBC Radio 4 Programmes - In Our Time, The Vacuum of Space

There's a mention of you in there too.

I'll leave it a few days before posting another podcast otherwise we might miss additional comments.

DC
 
#10
Remember it must spin the opposite way to the earth to go back in time and the same way as the earth but faster to go forward, might be a good idea to rig it all up to the mains too to create an electromagnetic field. Have you had the machine blessed by the appropriate faiths? Wouldn't want to sacrifce fido or send him into low level orbit without the conscent of the Egyptian Dog God, perhaps he might even team up with Laika?

Sounds like you're describing the Ether, the fabric of space/time is rather a good subject for our next podcast, but it also has a lot in common with the speed of light so we can keep that general convo going too.

The Vacuum of Space:
BBC - BBC Radio 4 Programmes - In Our Time, The Vacuum of Space

There's a mention of you in there too.

I'll leave it a few days before posting another podcast otherwise we might miss additional comments.

DC
The dog survived...but came back with a message in his collar. An invoice for carpet cleaning...

Ether theory is probably only partly flawed because the stuff that exists in there is pure potential, nothing else and can't be detected....it can be described as a field with zero density where only quantum fluctuation happen. Disturbed by events from dimensions within, light is a parameter for this existence so is relative....manifested by the interaction of mass and energy, the detectable tip of a legacy with roots in the void...fields within fields within nothing. The Higgs is likely to be invoked at some kind of super high frequency threshold or resonance. Mass is running at detectable lower frequencies.

I had a thought after hearing that last podcast. Imagine that you are sat on the rotating axis of a huge metal dial millions of miles long. It is spinning so fast that the extreme tip of the dial exceeds the speed of light. What would you see happening to the tip?

a. From your POV.

b. From a million miles above the dial?

Pity others are skipping this exellent thread... :)
 
#11
At this moment there are cosmic ray nuons that are passing through us at quite high speeds and hitting the earth everywhere. If Einstein's picture of space and time were not true we would not see these particles. They're made high up in the top of the earth's atmosphere when cosmic rays hit the top of the atmosphere and they move very, very close to the speed of light but they only live for a microsecond or so, so should decay long before they ever reach the earth's surface. They should only travel 600 metres, but they manage to travel 6,000 metres and reach the earth's surface and the reason is because their clocks go slow. They live longer because they're moving at such high speed, or equivalently the distance that they're travelling from the atmosphere to the surface is contracted by relativistic effects. So these transformations of length and time in order to keep their ratio of the speed of light the same for everybody are things that you see on a regular and routine basis
I think 'nuon' should be 'muon' (unless you're Jewish, already).

I have a vague recollection of measuring muon behaviour at Uni. ... here's a brief calculation I've just knocked up on my latest toy, Mathcad Prime, to show just how much longer it lives in our inertial frame (well, sort of inertial).

arrse 28 May 11.jpg
 

Attachments

#12
I had a thought after hearing that last podcast. Imagine that you are sat on the rotating axis of a huge metal dial millions of miles long. It is spinning so fast that the extreme tip of the dial exceeds the speed of light. What would you see happening to the tip?
You wouldn't - the situation would not arise because the tip could not exceed the speed of light.
 
#13
Perhaps exceeding the speed of light also penetrates this barrier...one would disappear into the void.
Great idea, but a *teeny* bit impossible. As the article (and excognito) stated, no normal matter can travel faster (or exactly as fast as, for that matter) than light. If it were possible, you would most likely be observed to be moving more slowly than you actually are (I think, though it would be neither a Lorenz contraction nor time dilation effect, but one caused by the fact that you would be moving faster than the photons advertising your presence), or you may become invisible, as the photons that enable organisms to see us will not be able to catch up with you in order to bounce off and into an observer's eyes. That said, it won't ever happen (I'll do a detailed explanation of why not via pm on request- decent grasp of mathematics helpful).
 
#14
I think 'nuon' should be 'muon' (unless you're Jewish, already).

I have a vague recollection of measuring muon behaviour at Uni. ... here's a brief calculation I've just knocked up on my latest toy, Mathcad Prime, to show just how much longer it lives in our inertial frame (well, sort of inertial).

View attachment 43872
Cogi, sorry I don't understand your post....any chance of informing me in simple terms what measuring the behavior of the muon has actually told us. That it lives longer because of velocity or something like that?

You wouldn't - the situation would not arise because the tip could not exceed the speed of light.
Yes, I know that... but what is the physical barrier? And if it was possible would the tip disappear into another dimesion?

Great idea, but a *teeny* bit impossible. As the article (and excognito) stated, no normal matter can travel faster (or exactly as fast as, for that matter) than light. If it were possible, you would most likely be observed to be moving more slowly than you actually are (I think, though it would be neither a Lorenz contraction nor time dilation effect, but one caused by the fact that you would be moving faster than the photons advertising your presence), or you may become invisible, as the photons that enable organisms to see us will not be able to catch up with you in order to bounce off and into an observer's eyes. That said, it won't ever happen (I'll do a detailed explanation of why not via pm on request- decent grasp of mathematics helpful).
Thanks for that... I obviously don't know anything about maths so everything I say is from imagination, poor science fiction sorry. Without observing the tip of the dial what would be happening to it as it reaches the speed of light? It's a bit like the problem of being in a spacecraft at the speed of light I suppose...to an observer it would disappear but being inside everything would be normal? Do the properties of matter break down and leave this existence above the speed of light, Back to the Future style?
 
#15
Relativity forbids ordinary matter (the disk edge) from ever reaching the speed of light, because it would require infinite energy. If you were on the edge I imagine things would appear normal but time would slow down relative to you. Though apparently the tachyon, if it exists, has no mass and actually generates energy when it goes faster than the speed of light.

Good thought experiment btw I might try and think of one too.

DC
 
#16
Relativity forbids ordinary matter (the disk edge) from ever reaching the speed of light, because it would require infinite energy. If you were on the edge I imagine things would appear normal but time would slow down relative to you. Though apparently the tachyon, if it exists, has no mass and actually generates energy when it goes faster than the speed of light.

Good thought experiment btw I might try and think of one too.

DC
The hunt for dark matter may be part of the puzzle...having pushed through the barrier it now exists in another state beyond detection except by observing it's effect on gravity..... Back to the shed eh ...:)
 
#17
It may well be poor science fiction, but it's questions like those that inspired me to study physics (even though I abhor maths!). Even as one approaches light speed, some pretty odd effects occur. An example of this is called Lorentz Contraction, whereby matter traveling extremely fast shortens along the direction of travel, but only to an external observer. This relativistic effect occurs all the time, but the contractions are so incredibly small that nobody notices them. Another one is Time Dilation, where the "clock" of that which is being observed will appear to run slowly relative to that of the observer. Again, this is present all the time, and is nothing to do with inaccurate instruments: these effects are all a part of the world that we live in, and have been confirmed indirectly by experiment. For the "stationary" observer (the imaginary observer travelling on the moving body, as they're stationary relative to the body) time will appear to run as normal. Now if you think that that's a mindfuck, try superstring theory ;)
 
#18
It may well be poor science fiction, but it's questions like those that inspired me to study physics (even though I abhor maths!). Even as one approaches light speed, some pretty odd effects occur. An example of this is called Lorentz Contraction, whereby matter traveling extremely fast shortens along the direction of travel, but only to an external observer. This relativistic effect occurs all the time, but the contractions are so incredibly small that nobody notices them. Another one is Time Dilation, where the "clock" of that which is being observed will appear to run slowly relative to that of the observer. Again, this is present all the time, and is nothing to do with inaccurate instruments: these effects are all a part of the world that we live in, and have been confirmed indirectly by experiment. For the "stationary" observer (the imaginary observer travelling on the moving body, as they're stationary relative to the body) time will appear to run as normal. Now if you think that that's a mindfuck, try superstring theory ;)
Yes...it's the most interesting subject of all. What lies beyond the barriers of our physical limits... Perhaps all theories are possible inluding superstring stuff...it may be a combination of everything. Anti-matter is connected to this existence by something...right? Inner space is also infinite... a fantastic thought.
 
#19
Not quite- you're getting too imaginative again... Antimatter exists in this reality; it looks like normal matter, weighs the same, and has the same rest energy a normal matter. It does, however have opposite values in terms of charge (Q), baryon number (B)*, Lepton number (L)*, Strangeness (S)*, and Spin**. This means that if a particle of matter (say a proton) meets its antiparticle (in this case an antiproton), they 'annihilate', literally destroying each other, and creating two photons of equal energy, satisfying the conservation of mass-energy law. Quite simple really.

Unfortunately the general point on theories is not as clear cut- sadly, not all theories can be correct, given that for any unexplained phenomenon there are likely to be different, conflicting theories (there are exceptions to this though, such as the dualistic wave-particle nature of light, where both Newton's corpuscular or particle theory of light, and Huygens's wave theory of light were both technically right- if you want to learn more, research Louis De Broglie and Paul Dirac). String theory is probably the best and most complete reconciliation of General Relativity and Quantum Mechanics attempted to date, given it's inherent mathematical consistency, but it's entirely impossible to prove experimentally, given the constraints of both modern technology and the wavelength of visible light***. If you want to learn more about string theory, there's a very good book called 'the elegant universe' (google it, can't remember the author) which deals with the problem of combining General Relativity and Quantum Mechanics, and the solution in string theory- it's pitched at non-scientists and those with no mathematical education beyond O level/GCSE, so I'm sure you'll find it accessible.

* Baryon number, Lepton Number, and Strangeness are just physical metrics of sub-atomic particles. Baryons are loosely defined as particles that are made of quarks (each quark has B= 1/3, a proton B= 1). Leptons are particles not made up of quarks, like electrons. Strangeness is complicated, but a strange quark has S= -1; there's other stuff, like it's conserved in strong force interactions, but I can't be arsed to explain at this time of night.

** spin is another property of a particle, and really does measure how much a particle spins; it can vary in value, but as a rule protons and neutrons have integer (whole number) values of spin. I think. I'll check in the morning.

*** Put simply, if something is smaller than the wavelength of visible light, then it can't be seen with an optical microscope. There are other ways, like using electrons, which have even smaller wavelengths, but it becomes increasingly difficult to find things to use in order to make micrographs of ever-smaller objects. Also, bombarding things with electrons changes the nature if that which is being observed, which is known as the 'observer effect', and gives rise to Heisenberg's uncertainty principle- google it, it's nearly midnight and I'm even beginning to bore myself, which is never a good sign.
 
#20
Higgsy may have a point regarding the different dimensions, perhaps the Uncertainty Principle, the burrowing effect of electrons and wave particle duality have something to do with atomic particles existing in more than one dimension? I believe this is also the case for String Theory as the string’s spin is actually a term for them spinning in other dimensions too. Of course trying to prove this mathematically is one thing but whether or not we'll ever be able to prove the existence of other dimensions is another.

The concept of infinity existing is also an interesting notion because it’s inherently paradoxical, although Hawking suggests that it exists in the singularity of a black hole having infinite mass. If it does exist in the universe it would lead to some very bizarre properties.

DC
 

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