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New Theories / Re: Can I convince you that consciousness (and therefore spacetime) is involved?
« on: 12/06/2019 08:20:05 »
Define consciousness, and we'll talk.
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2
Technology / Re: Why do aeroplane propellers appear curved?
« on: 09/06/2019 15:45:25 »
"I say, chaps, the prop seems to have stopped but we are still flying"
"Praise the Lord"
"Praise the Lord"
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3
Physics, Astronomy & Cosmology / Re: How does gravity exert its influence infinitely?
« on: 28/05/2019 19:07:16 »
Now if electromagnetic energy has a gravitational field, photons travelling through otherwise unoccupied space will tend to clump together (since gravity always sucks) , so the intensity of light received from distant stars will increase with distance, by self-focussing. And there will be stars out there that we can't see because their self-focussed beam isn't pointing in our direction.
Really?
Really?
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4
Technology / Re: When will driver-less cars become a reality?
« on: 25/05/2019 09:05:51 »
So far, driverless (or at least "driver-assist") vehicles work well on motorways and similar controlled, predictable environments. Things go wrong when you have to make a choice.
Dog in the road. Stop, drive round it (which way?), blow horn, or slow down and drive straight at it? The last is probably the safest as the dog will recognise the threat and move, but you don't know which way. But a bull or a ram is quite likely to hold its ground to defend its family, so your car needs to recognise species (Been there! We stopped, and the ram charged at the car!)
Arrive at destination, turn off the main road onto a building site with temporary signs that have been changed since yesterday. Can your car read handwritten "office closed - report to traffic marshal for parking"? Is the truck in front of you stopped to allow other traffic to pass, parked, or unloading?
Motorways aren't a problem anyway. People die on side streets, city roads, country lanes and work areas (including supermarket car parks), where programmed vehicles tend to get confused.
Dog in the road. Stop, drive round it (which way?), blow horn, or slow down and drive straight at it? The last is probably the safest as the dog will recognise the threat and move, but you don't know which way. But a bull or a ram is quite likely to hold its ground to defend its family, so your car needs to recognise species (Been there! We stopped, and the ram charged at the car!)
Arrive at destination, turn off the main road onto a building site with temporary signs that have been changed since yesterday. Can your car read handwritten "office closed - report to traffic marshal for parking"? Is the truck in front of you stopped to allow other traffic to pass, parked, or unloading?
Motorways aren't a problem anyway. People die on side streets, city roads, country lanes and work areas (including supermarket car parks), where programmed vehicles tend to get confused.
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5
Technology / Re: When will driver-less cars become a reality?
« on: 22/05/2019 18:11:42 »
But you just did!
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6
Physics, Astronomy & Cosmology / Re: Does a photon self propagate due to the interactions of the electric and magnetic fields?
« on: 19/05/2019 23:02:20 »
Even then, you need to remember that "observation" is introduced as an auxiliary and explanatory concept in physics, rather like "cross section" in engineering. Nobody is going to cut a ship in half to make it work, but drawing what it would look like if cut in half, is very helpful in explaining how it works.
The natural world does what it does, and we petty beings try to understand and model it as though we were observers to every action.
To go back a couple of paragraphs, the properties of longitudinal compression waves are pretty much independent of frequency, so they are all "sound" whether we, bats or transducers can sense them, but the interaction of electromagnetic radiation with matter is strongly dependent on its frequency so we assign specific names to parts of the spectrum, and the tiny bit that excites transient chemical responses in the eye is called light.
The natural world does what it does, and we petty beings try to understand and model it as though we were observers to every action.
To go back a couple of paragraphs, the properties of longitudinal compression waves are pretty much independent of frequency, so they are all "sound" whether we, bats or transducers can sense them, but the interaction of electromagnetic radiation with matter is strongly dependent on its frequency so we assign specific names to parts of the spectrum, and the tiny bit that excites transient chemical responses in the eye is called light.
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7
Physics, Astronomy & Cosmology / Re: Does a photon self propagate due to the interactions of the electric and magnetic fields?
« on: 15/05/2019 17:25:26 »
Electromagnetic radiation propagates according to Maxwell's equations,which are based on the observation that a moving charge creates a magnetic field (see any electromagnet) and a varying magnetic field induces charge (see any dynamo).
The electromagnetic spectrum is continuous but some sources of em radiation emit discrete quanta with a specific frequency.
The "observer" is irrelevant since the photon, phonon or whatever has no concept of observation and the source, which may be a few billion light years away, really doesn't care what happens to the energy it radiates.
Sound is longitudinal pressure waves of any frequency in any medium. The effect of a sound wave has nothing to do with the auditory system. You can play your violin in front of an audience of bats, humans and neurologically deaf humans - the effect on their tympani and auditory ossicles is exactly the same, and the same on a microphone diaphragm that converts it to an electrical signal. The violin and the connecting air have no interest in the nature or presence of a receiver.
The electromagnetic spectrum is continuous but some sources of em radiation emit discrete quanta with a specific frequency.
The "observer" is irrelevant since the photon, phonon or whatever has no concept of observation and the source, which may be a few billion light years away, really doesn't care what happens to the energy it radiates.
Sound is longitudinal pressure waves of any frequency in any medium. The effect of a sound wave has nothing to do with the auditory system. You can play your violin in front of an audience of bats, humans and neurologically deaf humans - the effect on their tympani and auditory ossicles is exactly the same, and the same on a microphone diaphragm that converts it to an electrical signal. The violin and the connecting air have no interest in the nature or presence of a receiver.
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8
That CAN'T be true! / Re: Does the Apollo 11 space craft contain the fuel required for the moon mission.
« on: 07/05/2019 23:23:33 »Why does not a penny in the ISS stick to the walls?Because Orbit chewing gum is a terrestrial breath freshener, not astronaut issue.
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Physics, Astronomy & Cosmology / Re: Is earth moving at close to the speed of light?
« on: 24/04/2019 12:45:52 »
But we are! We see red and blue shifts out there, which means that, simultaneously, other observers see us as red or blue shifted, and all shades between.
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That CAN'T be true! / Re: LIGO represents an mirror displacement of what?
« on: 20/04/2019 11:41:31 »
Wikipedia says
My inclination is to say that an electron probably has the same density as a proton or neutron, so its radius is probably calculable if not directly measurable.
We can also set a lower limit to its radius from the knowledge that you can't bind two electrons together by gravity, so the maximum gravitational attraction Gme2/d2 must be less than the electrostatic repulsion qe2/4πε0d2 where d is the diameter of an electron, with mass me and charge qe.
Quote
According to modern understanding, the electron is a point particle with a point charge and no spatial extent.which I suppose is rather stretching the meaning of "understanding".
My inclination is to say that an electron probably has the same density as a proton or neutron, so its radius is probably calculable if not directly measurable.
We can also set a lower limit to its radius from the knowledge that you can't bind two electrons together by gravity, so the maximum gravitational attraction Gme2/d2 must be less than the electrostatic repulsion qe2/4πε0d2 where d is the diameter of an electron, with mass me and charge qe.
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11
That CAN'T be true! / Re: LIGO represents an mirror displacement of what?
« on: 20/04/2019 09:50:07 »
A problem arises if you consider an electron to be a point charge with no radius: having a measurable mass, it would have infinite density. This would give it an infinite gravitational potential. There are quite enough black holes in the universe without postulating several more inside every atom.
Just one more example of the inappropriateness of classical modelling in a quantum universe.
Just one more example of the inappropriateness of classical modelling in a quantum universe.
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12
Physiology & Medicine / Re: Can contaminants in food cause water retention?
« on: 16/04/2019 22:50:17 »it foams as it comes out of the tap, has a horrible metalic taste etc.The brown foamy stuff is called beer. It's supposed to taste like that.
Fact is that London and Essex water is dead hard, like us. You can stand a spoon up in it and a wet shave puts hair on yer chest, mate. We even have special tea for hard water 'cos that wet northern stuff don't cut it. Why do they call them jellied eels? Cos you ave to blast them out of the Thames wiv gelignite, the water's that hard.
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13
New Theories / Re: Can a photon be visualized ?
« on: 07/04/2019 14:43:51 »
The particle model doesn't predict the speed of light in vacuo because there is nothing there to absorb and re-emit particles.
Maxwell's equations show that you don't need any medium to transmit light, and imply that the speed of light in vacuo is independent of direction, with values of ε0 and μ0 chosen arbitrarily to rationalise the system of units in use - they don't refer to the properties of a medium but are the "fudge factors" that make electrostatics and electromagnetics mutually consistent.
Maxwell's equations show that you don't need any medium to transmit light, and imply that the speed of light in vacuo is independent of direction, with values of ε0 and μ0 chosen arbitrarily to rationalise the system of units in use - they don't refer to the properties of a medium but are the "fudge factors" that make electrostatics and electromagnetics mutually consistent.
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14
Physics, Astronomy & Cosmology / Re: Why don't atmospheric gases separate according to specific gravities?
« on: 30/03/2019 00:34:25 »
They do separate, despite thermal and turbulent mixing. The upper atmosphere does contain slighty less oxygen and a lot less carbon dioxide than the lower atmosphere.
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15
Physiology & Medicine / Re: what do adheliolysis and laminectomy have in common?
« on: 23/03/2019 08:09:39 »
1. Worth checking the website, at least - they seem to offer very short waiting times: www.welcomebackcentre.com
2. Yes, sadly, there are all sorts of jokes about orthopedic surgeons, but having had a hip joint replaced by an old friend who really does do woodwork in his spare time, I've nothing but respect!
2. Yes, sadly, there are all sorts of jokes about orthopedic surgeons, but having had a hip joint replaced by an old friend who really does do woodwork in his spare time, I've nothing but respect!
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Physiology & Medicine / Re: what do adheliolysis and laminectomy have in common?
« on: 22/03/2019 07:38:58 »
Google "upright MRI Canada". There is apparently only one, in BC, but several (around 80) within reach in the USA (try Chicago and New York - I haven't found one in New England, despite trying to set up a clinic in Boston myself!) and at least half a dozen in the UK. Worth a visit - a transatlantic flight costs less than an MRI scan!https://www.uprightmri.co.uk/london.php has the best images - not a commercial as I no longer own the company!
Be careful in your choice. Most "open" MRIs can't actually scan you standing or sitting. The FONAR upright system is a big beast: it can accommodate almost any size and posture and is the most technically advanced. Paramed is a close second, but considerably easier to install so may offer a more local service. I owned a FONAR and two Parameds and have referred family and friends to either. Esaote make a smaller unit with some limitations, mostly used for limbs but if you are reasonably slim it will produce loadbearing images of the spine. Other systems may be available (including a venerable GE "double donut" that never went into volume production) but I haven't worked with them.
The trick is to use a steel-frame magnet rather than the air-cored superconducting solenoid of "conventional" MRI. This allows us to orient the field perpendicular to the patient (which improves signal capture) and put the magnetising coils out of the way, so you walk in between the poles. Imaging is a bit slower than a tunnel unit, but that isn't a problem for skeletal anatomy as the target doesn't pulsate or squirm. The downside of steel magnets is an upper limit on field strength of about 1tesla, and a lot of mechanical and electrical engineering: the big machine weighs over 150 tons and eats 200 kW of electricity, which is why there aren't many around.
Be careful in your choice. Most "open" MRIs can't actually scan you standing or sitting. The FONAR upright system is a big beast: it can accommodate almost any size and posture and is the most technically advanced. Paramed is a close second, but considerably easier to install so may offer a more local service. I owned a FONAR and two Parameds and have referred family and friends to either. Esaote make a smaller unit with some limitations, mostly used for limbs but if you are reasonably slim it will produce loadbearing images of the spine. Other systems may be available (including a venerable GE "double donut" that never went into volume production) but I haven't worked with them.
The trick is to use a steel-frame magnet rather than the air-cored superconducting solenoid of "conventional" MRI. This allows us to orient the field perpendicular to the patient (which improves signal capture) and put the magnetising coils out of the way, so you walk in between the poles. Imaging is a bit slower than a tunnel unit, but that isn't a problem for skeletal anatomy as the target doesn't pulsate or squirm. The downside of steel magnets is an upper limit on field strength of about 1tesla, and a lot of mechanical and electrical engineering: the big machine weighs over 150 tons and eats 200 kW of electricity, which is why there aren't many around.
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17
Physiology & Medicine / Re: what do adheliolysis and laminectomy have in common?
« on: 21/03/2019 08:16:10 »
It's a general term for relieving adhesion between bits that shouldn't be stuck together by scar tissue.
https://paindoctor.com/treatments/adhesiolysis describes its specific application in spinal stenosis. Clever stuff and less invasive than fusion or laminectomy, but if you can get an upright MRI beforehand, that will give a more reliable indication of the correct target area than a recumbent scan.
https://paindoctor.com/treatments/adhesiolysis describes its specific application in spinal stenosis. Clever stuff and less invasive than fusion or laminectomy, but if you can get an upright MRI beforehand, that will give a more reliable indication of the correct target area than a recumbent scan.
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18
Physiology & Medicine / Re: where does excess bone go in a laminectomy?
« on: 18/03/2019 08:49:38 »
Laminectomy diagrams show complete removal of the spinous process and its supporting arch laminae to decompress the nerve sheath, so any cutting debris will have been removed by suction during the cutting process.
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19
Technology / Re: What is the net environmental impact of biofuels?
« on: 15/03/2019 09:53:05 »
The net impact has not been impressive to date. Fossil hydrocarbons have an inherently high energy density because they have been dehydrated and compressed over zillions of years, so in principle you can just pick up a lump of coal or a bucket of crude oil and set fire to it, whereas anything derived from recently living plants has to be harvested, dried, compressed, and possibly boiled or fermented before it becomes useable. Even domestic firewood needs more energy input from chainsaws and trucks than coal, per unit heat output, because you are handling around 50% water in the raw product.
The more subtle problem is in fact water. Fermentation produces low molecular weight alcohols which are usefully combustible (though less energy dense than diesel) but hygroscopic, and also tend to corrode many rubber and plastic parts, so there's a limit to the amount of biofuel you can use in an existing internal combustion or jet engine. It takes as much energy to build a new car as it will use in its life, so rapid fleet replacement is not energy-efficient, even if you can design an engine that tolerates low-mw fuels. Except for methane, which has a very low energy density but can be used in a petrol engine with very little conversion.
The more subtle problem is in fact water. Fermentation produces low molecular weight alcohols which are usefully combustible (though less energy dense than diesel) but hygroscopic, and also tend to corrode many rubber and plastic parts, so there's a limit to the amount of biofuel you can use in an existing internal combustion or jet engine. It takes as much energy to build a new car as it will use in its life, so rapid fleet replacement is not energy-efficient, even if you can design an engine that tolerates low-mw fuels. Except for methane, which has a very low energy density but can be used in a petrol engine with very little conversion.
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New Theories / Re: Split from "How fundamental is time?"
« on: 13/03/2019 23:48:09 »
No. An EM wave is information
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