The Speed of Light (and Gravity?)

Within Relativity Theory, if there is anything unintuitive it is the fact that in the entire Universe, it is the speed of light (and gravity?) alone that is absolute or fixed, not something like space being absolute or time being absolute. It’s unintuitive in that all the other not-light bits and pieces that are in motion can be added or subtracted. The lone exception to that universal rule that velocities can be mathematically combined is the speed of light (and gravity?).

Repeat for emphasis: the anomaly here is that in any other scenario, anything that is not-light and in motion, velocities can be added and subtracted. Repeat again: with that one speed of light exception, velocities may be added or subtracted. If you are on a treadmill that’s moving left at 5 MPH, and you’re on it walking to the right at 5 MPH, to an external observer you are waking yet standing still. You’re much more likely to hit a home run if the wind is blowing towards the outfield fences; planes fly faster with a tailwind than with a headwind; you swim in the river faster going with the flow than against the current. If you are in a train that is moving at say 100 km/hour and you throw a ball at 10 km/hour in the direction at which the train is moving, to an observer outside the train, your ball is traveling at 110 km/hour. If you throw the ball towards the rear of the train, an outside observer will measure the ball as moving at 90 km/hour. If on the other hand, you shine a flashlight in the train, an outside observer will see the velocity of the resulting light beam moving at the speed of light – not the speed of light PLUS the velocity of the train, or the speed of light MINUS the velocity of the train, but at the speed of light! That’s nuts, but it’s scientifically nuts and been proven again and again in any experiment you care to devise. I have no issue with experimentally verified results. That doesn’t mean I don’t have issues with the anomaly.

The velocity of light is a constant to an external observer no matter what. Why that should be no one knows, but it is so. However, my take on this can of worms, which as a consequence requires somewhat counter-intuitively that both time and length have to be flexible, is one should always be a bit suspect when it comes to the lone ranger, the lone ranger being the exception to the rule*. I don’t tend to like exceptions to the rule. There’s something weird afoot here. Mother Nature is trying to tell us something we haven’t figured out yet.

All that said, the speed of light isn’t really a constant if you take into consideration the differing mediums that light can travel through. However, the speed of light is probably also a constant within whatever other medium it happens to be in. The speed of light in air at STP (standard temperature and pressure) is less than the speed of light in the relative vacuum of outer space; even less traveling through pure water and less again traveling through clear glass. One would presume that just as the speed of light in space is constant for observers regardless if they are traveling in a high velocity spaceship or as an astronaut ‘stationary’ on the International Space Station, the speed of light in water sould be a constant for the crew in a submarine that’s underway thus in motion or a diver standing on the seabed.  

That makes me sort of wonder, theoretically, if you could get an underwater submarine to go faster than the speed of light in water (or an aircraft to outpace the speed of light in air), though in either case that would be less than the speed of light in a vacuum, could you then claim, albeit with qualifiers (in water; in air), that you actually traveled faster than the speed of light, if only for the bragging rights? 

Apart from light (photons), presumably gravity, or gravity-waves, also propagate at the speed of light and thus a gravity-wave would have a constant speed regardless of any frame of reference for any observer. But I also presume that necessitates finding the hypothetical graviton particle (to mirror the photon) and that, for the moment, resides in the unknown basket.

That brings up yet another puzzlement. Is gravity just geometry as per General Relativity or is gravity a force transmitted by a force particle, the theoretical graviton, and thus more akin to electromagnetism’s photons (infinite extension; obeys the inverse square relationship) apart from lacking EM’s negative counterpoint – in the case of gravity, that’s antigravity.

Speaking of gravity (gravitons) and light (photons), if gravity can have an effect on light (i.e. – the gravitational lens), then it should be a two-way street and light should be able to have an observable affect on gravity, but I can’t recall ever reading about that aspect of the relationship. 

As per the speed of light being medium dependent; one speed in a vacuum, another in water, well that makes for an interesting question when considering gravity. If a gravity-wave is approaching Earth, will it have one constant velocity in the vacuum of space for all observers, then a differing velocity as it passes through our atmosphere, then another value as it passes through the ocean and yet others as it hits the various density layers inside the planet?    

As is often the case, there tends to be more questions than answers!

*Not that the differing rules for the speed of light vis-à-vis other not-light velocities is the only exception to the rule in modern physics. Quantum tunneling is one of those exceptions to the rule of causality. With respect to the standard model of cosmology and the Big Bang, first there was nothing; then there was something. That means the Big Bang event created both matter and energy out of less than thin air. That’s also a free lunch and one of those exceptions to the rule of physical law usually expressed as the conservation of matter and energy. All these exceptions to the norm suggest that some of the final chapters in modern physics haven’t yet been written.



The Quantum Realm: Part Two

Now the really interesting thing about quantum physics isn’t so much the physics but the philosophy behind it all. Why is it so? What does it mean? That these philosophical issues matter and should be of interest is because you, the macro reader, is made up entirely – from the ground up – out of the residents of the realm of the micro, the inhabitants of the realm of the quantum.

Continued from yesterday’s blog…

As a review, with commentary, these are my takes on quantum strangeness:

Case Study #1 deals with that double slit experiment. IMHO photons fired one at a time at the double slit should not form a classic wave interference pattern with or without slit detectors in place. The concept of superposition belongs in “The Twilight Zone”, though apparently, so the scenario goes, what’s emitted is a particle; what’s detected is a particle; but the flight or pathway in-between is a wave-of-probability. It’s the slit detector that changes wave-of-probability into location, but that exact location must have existed even had the detector (our stand-in observer) not been in place. How does that explain the one photon at a time interfering with itself and causing that classic wave interference pattern? It doesn’t, but it’s a better bet than trying to come to terms with the idea of a thing being in two places at the same time.

Case Study #2, dealing with entanglement, well let’s just say that a particle on one side of the Universe should be independent of the fate of a particle on the opposite side of the Universe. More superposition equals more of “The Twilight Zone”.

Case Study #3: There needs to be a bona fide causality inspired reason why an electron gives away a photon and drops to a lower energy level. It’s not a whim thing. Maybe it’s another photon bumping into the electron and discharging the absorbed photon, maybe not, but it’s not a whim thing.

Case Study #4: Neutrinos should not endlessly change their clothes on route. The fact that they do contributed to some serious reflection that the core of our Sun had actually shut down. Scientists when looking for electron-neutrinos emitted by the Sun’s solar furnace didn’t see enough of them and thought the worst. It wasn’t until much later that they realised they had missed all those electron-neutrinos that the Sun had actually given off but which had changed their attire between the Sun and the Earth.

Case Study #5 notes that if you are made of matter, it would not be a good idea to shake hands with your antimatter twin self! But why matter and antimatter should go poof at all is a bit strange. An electron has a negative charge and its antimatter twin has a positive charge (hence the name positron). They go poof upon contact. But a proton has a positive charge equal and opposite to that of an electron and they don’t go poof when brought into contact so there’s more than just opposite charges annihilating each other at work here obviously. There’s no question that chemical reactions can give off energy, but total annihilation – wow. 

Case Study #6: Quantum Tunnelling should happen for a reason – it doesn’t. Quantum Tunnelling shouldn’t happen instantaneously since that violates the cosmic speed limit – the speed of light. The fact that in the micro world, barriers, well ain’t, makes all human inmates wish they were subatomic particles! 

The overall image that keeps springing to mind is all those Hollywood special effects. They would be an excellent explanation for all of the above weirdness. Think about it!

Finally, we should also note that most of the above examples or case histories involve quantum probability, uncertainty, indeterminism, etc. with respect or relative to the observer which could be you or me.

Case Study #1 suggests that photons (or electrons or any other fundamental particle) are in a superposition of state, which suggests that they can be apparently in two (or more) locations at the same time, and it’s only based on probability as to exactly where that location is. But it is in just one location as the addition of actual slit detectors verifies. So, the key point is that the photon or electron or whatever is 100% at a specific set of coordinates even if the double slit experiment suggests that the photon or electron or whatever is smeared out over a wide ranging area and only probably here or probably there.  So probability really bites the dust since location (one slit or the other) is confirmed by observation – there’s location, location, location; not probable, probable, probable!

In Case Study #2 we have more about that superposition of state whereby a particle may actually be a particle or an antiparticle (probability is 50/50) or spin up or spin down (probability 50/50). But you know, and I know, that in reality, one particle IS a particle (probability 100%) and the other IS an antiparticle (probability 100%) or one particle IS spin up (100% probability) and the other IS spin down (100% probability). There is no indeterminacy even if there is no observer, there is only determinacy, positive actuality, whether or not one or the other is observed. There is no across the universe communication. There is no ‘spooky action at a distance’. There is no probability involved other than 100% probability, otherwise known as a sure thing.

In Case Study #3 we have an electron that absorbs a photon’s energy and thus quantum jumps to a higher energy level. It then becomes a matter of probability as to when that electron emits that photon and jumps back down to a lower energy level. But, as in the case of radioactive decay, the odds are 100% that it will happen. Probability need not apply here. Probability is not applicable. The key concept here is again, ‘sooner or later’.

In Case Study #4, we might not know why the neutrino changes clothes, or exactly when and under what circumstances, so, as far as we are concerned it’s all boiled down to statistical probability what clothes any particular neutrino will be wearing when detected. However, there’s no doubt in my mind that causality is operating and that it’s 100% certain that the neutrino is wearing the clothes that causality has dictated. There’s no probability involved, only the probability that we’re probably pretty dumb for not figuring out why.   

Finally, in Case Study #5 somehow particles and antiparticles seemingly ‘know’ when they meet and greet whether to go poof or not go poof. The mystery is how they ‘know’. But it’s total certainty one way or the other and the observer has no relevance or say in the matter.

Case Study #6: Quantum Tunnelling, as already noted, happens for no reason at all. It’s responsible for radioactive decay which happens for no apparent reason at all. There is no way, rhyme or reason that enables one to predict when a quantum tunnelling event will transpire. It’s all probability. Either that, or a subatomic particle has a free will mind of its own and the knowledge and the ability of a Harry Houdini.

I have one other observation while on the issue of causality and probability if you please. If something quantum happens for no reason at all (i.e. – unstable subatomic nuclei goes poof) why doesn’t everything micro happen for no reason at all. Or, if some quantum happenings are just probabilities, why aren’t all micro happenings probabilities. Now IMHO if 99.999% of all physical effects can be traced back to one or more causes, it’s pretty safe to suggest, even conclude if you’re a betting person, that 100% of all physical can be traced back to one or more causes, even if those causes remain as yet unknown.

Lastly, consider and reconsider the quantum mantra: Anything that isn’t forbidden is compulsory; anything that can happen will happen. Does that sound like a probability statement to you?

I suggest this puts the kibosh on quantum physics being steeped in probability. There is no probability once you eliminate the observer and the observer’s fixation on either where things are; where something is, or whether something is or is not going to happen, and when something is going to happen. Before there were observers, things were somewhere, fixed and absolute, things did their thing without any guesswork or decision-making involved, and things happened sooner or later with absolute certainty.



A Quantum Pane In The Glass: Part Two

In quantum physics, you may deduce that those residents of the micro realm, those elementary particles, have some very strange properties bordering on a quasi-free will.  They seemingly have the ability to ‘know’ things about their external world and their relationship to that and make decisions and act accordingly. There are experiments to back this up that include an observation you can make at home to verify this. Look outside your window. What do you see? A very big mystery is what you see, if your window is anything like my window or most windows.

Continued from yesterday’s blog...

CAUSALITY & CERTAINTY vs. PROBABILITY & CHANCE

I need state the obvious here – all photons are identical; the pane of glass in question is obviously identical to itself. Therefore, knowing that and only that, one could only conclude that when photon meets window pane, one and only one outcome is possible.

We, the observer say the photon has such and such a probability of going through, or being reflected from, the pane of glass. If seven out of ten photons go through the glass window, then there’s a 70% probability the next photon will go through. Wrong. As far as that photon is concerned, we, the observer, are irrelevant, and it’s 100% certain to either go through the glass or be reflected by the glass. We can be pretty damn sure that a group of photons won’t gather together in the middle of the glass pane and do an impromptu performance of a Wagnerian opera. There’s no probability involved. It’s one or the other. There’s no superposition of state. The photons aren’t in two places at once – passing through and being reflected.

Another way we can be sure causality is operating, albeit going up one level, is that every time you go to the inside of your window pane looking outside, you see both outside and a faint reflection of you and the interior. Not once in a while; not sometimes 100% outside and no reflection; not sometimes a 100% reflection but you can’t see outside (your window isn’t a mirror after all), but 100% of the time, each and every time, you see both the exterior outside the pane and the interior reflected inside the pane. 

SUMMARY, DISCUSSION & RESOLUTIONS

In summary here, some photons from the inside pass through a pane of glass to the outside; some outside photons pass through that glass to the inside; some photons from the inside reflect off the glass back inside and some outside photons reflect off the glass back outside. The big question is, how does the photon decide what to do? Here comes Ms. Photon heading toward the pane of glass. She has to make up her mind whether to pass on through or reflect back: decisions, decisions. To reflect, or not to reflect, that is the question! IMHO, photons should all go through, or all reflect, from the same pane of clear glass at the same time.

We note from the outset that the glass hasn’t been tinted or polarized – not that that would alter the general picture. What we have here is just an ordinary pane of glass.

Further, no external forces are apparently at work here. Both the photons and the glass are electrically neutral. Gravity plays no role and the strong and the weak nuclear forces are only applicable inside atomic nuclei.

To make a long story shorter, causality rules IMHO! Photons are not in a state of superposition; they are not in two places at the same time. Clearly photons are not in a position to ‘know’ anything. Photons have no decision-making apparatus; they have no consciousness of any kind, no free will to be or not to be. That can be demonstrated by adding a little extra thickness and/or density and/or energy.

But first, one could easily suggest that since even seemingly ‘solid’ stuff is 99.999% empty space, that a photon passing through the glass is passing through that entire void, and a photon reflected has hit a glass molecule and bounced back. One exception to that is that the reflection takes place at the surface of the glass pane, none from the interior of the glass. A second exception would be that reflections off of a solid molecular bit in the mainly empty glass pane would be totally scattered in many directions which is what we don’t see. Basic optics – the angle of incidence equals the angle of reflection. Yet clearly if photons are being reflected, they are bouncing off something. Or, perhaps they are being absorbed by the electrons within the glass matrix and then reemitted, though the photon that’s reemitted might not be the exact same photon – but that’s of no consequence since all photons are identical.    

We note that the greater the thickness or the greater the density the more the pass through to reflection ratio changes. If you look through the exact same pane of glass, but this time edgewise, no photons pass through from one edge to the other edge. The X-ray case study above shows the role of increasing density. Both are an illustration that ultimately things become so thick and/or so dense that while there might not be total reflection, there would be any pass though either. The option for the photon might then be reflection vs. partial penetration. Of course that in itself doesn’t explain the either this or that option the photon takes, at least until such time that it becomes one or the other. In a vacuum it’s 100% pass through and 0% reflection; in the case of a metre thick lump of lead, a light photon will 100% reflect and 0% pass through. Restrictions placed in the photon’s way by density and thickness just tends to confirm an earlier notation that stuff is 99.999% void such that pass through equals boldly going through that void; reflection is a collision with that rare bit of stuff that sometimes gets in your way.

But that’s not the entire story. Thickness is also related to opaqueness though they are not the same thing. Photons can pass through Earth’s entire atmosphere from the fringes of outer space to ground level, yet if you dab a smear of black paint on your pane of glass, well that will strop the photons from passing through albeit black paint is a lot less thick than the Earth’s atmosphere.

Energy plays a role too. X-ray photons are more energetic than visible light photons, which is why X-rays are better for detecting structural flaws (like tooth cavities and bone micro-fractures) which are concealed by external surfaces which are opaque to light.

Air and glass are transparent to light photons, but are generally fairly opaque to the less energetic infrared photons. That’s the general principle or concept behind both the botanical greenhouse and the environmental greenhouse effect, although in the later case not all the components found in air are equally as opaque.

Ultimately invoking variations in properties like density, thickness, energy levels and opaqueness doesn’t totally explain why identical particles, with all other factors being equal too, have this Jekyll and Hyde property whereby some do and some don’t; some will and some won’t.

But we see that while things aren’t totally explained yet, we’re well on the way to determining the real factors that decide the photon’s fate, and it’s not photon’s free will either. 

A Quantum Pane In The Glass: Part One

In quantum physics, you often deduce that those residents of the micro realm, those elementary particles, have some very strange properties bordering on a quasi-free will. They sort of possess a ‘mind’ of their own. They seemingly have the ability to ‘know’ things about their external world and their relationship to that. They make decisions with respect to those relationships and act accordingly. They are not just little inert billiard balls. There are observations to back this up that include an observation you can make at home to verify this. Look outside your window. What do you see? A very big mystery is what you see, if your window is anything like my window or most windows.

Even if you don’t know or understand very much about quantum mechanics, or quantum physics (same difference), you have probably associated it with weirdness. Unlike the certainty and causality domination of your day-in and day-out macro world, the realm of the quantum is centred on probability, chance and randomness where things happen for absolutely no reason at all and identical scenarios will yield different results. One oft given example you can (and have) witnessed – how light (photons) interacts with a common pane of window glass.

GENERAL DESCRIPTION

Here is a common happening that you have experienced at home or in the office or in the car that you probably never gave a second thought to. That unregistered oddity you experienced is seeing the reflection of AND the passing through of light waves (photons) with respect to a pane of glass simultaneously. What’s so odd about that? Well, what’s odd is that light is both passing through and reflecting from the same pane of glass at the same time. Why both? Why not one or the other scenario? What’s odder still, assuming you are inside, is that not only can you see your reflection or the reflection of what’s in your background but what’s also outside and through your own reflection. You see your reflection and the outside image, both superimposed on top of each other. So photons are both passing through the glass (you can see the outside while you are inside) from the outside to the inside and at the same time reflecting from the inside to the inside (you can see the inside from the inside) both happenings at the same spot on the glass.

And if you go outside the reverse is also true. The outside is partly reflected by the glass surface back to you while you are outside looking in while at the same time light photons from the inside are passing through the entire glass so you can see inside your room though you are standing outside, both inside and outside as superimposed images.

Further, the ratio of pass through to reflection also depends on the thickness of the glass, so presumably the photon ‘knows’ in advance what that thickness is and acts accordingly. If all of that doesn’t strike you as odd, nothing will, though it’s so commonplace it probably doesn’t strike you as odd.

OTHER EXAMPLES

This ‘do I or don’t I’ oddity doesn’t just apply to panes of glass. This applies to a wide range of transparent, even translucent stuff. The same pass through vs. reflect back applies for example to your eyeball. Some photons enter your eye and deliver their message; some photons hit the identical spot but are reflected back, but can then hit a mirror and reflect back again this time entering your eye so that you see your eye that reflected in the mirror.

Speaking of eyes, you can ‘see’ an external bright light even with your eyelids shut, yet some of the light is also being reflected off the external surface of your eyelids.

Sunglasses are another obvious example. You can see your reflection in the outer side of the lenses, but clearly the sunglasses let through without any obstruction photons too.

You can see your reflection in still water and the bottom beneath the surface too if the water is pretty clear and the bottom is fairly shallow. This should also apply to say a polished diamond or other similar gemstones or crystal(s).

Another visual example – you see sunlight reflected off of the tops of clouds when in an aircraft that’s flying above them. As you descend through them and land, though the day is now overcast, clearly some sunlight photons are passed through the clouds. It’s the same clouds; and the same sunlight; and the same observer; but differing outcomes. So the pass through vs. reflection enigma applies equally to translucent objects (like clouds) too.

Though this is an obviously visual puzzle, well that in itself is obvious since we can only see visible light photons. However, photons come in a wide range of forms, from ultraviolet to radio; infrared to microwave; gamma rays to X-rays. Presumably this pass through vs. reflection phenomena takes place with non-light photons too. The most obvious example is that radio, TV or cell phone reception tends to be better outside than inside – one reason for your TV aerial or antenna. So, some radio/TV/cell phone photons are reflected off of the outside of your solid building but some pass through too, but this has nothing to do with frequency or wavelength since these transmissions are on a very narrow bandwidth.

In a similar vein, it’s been advocated for decades that the ideal location to do radio astronomy and/or SETI, searching for alien radio signals, is on the far side of the Moon because the Moon’s bulk is 100% opaque to terrestrial and human generated radio signals that just add unwanted noise to the signals the astronomers are looking for.

One clue that the pass through vs. reflection conundrum must be density related, not just thickness related, comes from X-rays. We’ve all seen X-ray photos of the human hand. The bones stand out; the wedding ring more so, but the flesh is visible too though less so. So some X-ray photons were reflected, greater reflection related to the density of the stuff the X-ray photon was hitting. Yet clearly some X-ray photons passed through since the image of the fleshy bits isn’t as strong as the bones and the bones weren’t as solid an image as the ring. Yet it was the exact same X-ray dose that hit all three substances – flesh, bone and metal.  

THE STANDARD SOLUTIONS

The basic postulate postulated by quantum physicists is that the photon pass through vs. reflection anomaly is an anomaly because it all happens for absolutely no reason at all. It’s all random. It’s all probability. Some photons pass through via the luck of the draw; other photons get reflected by that same random luck of the draw. How is that possible given that we have, in the original example, one identical pane of glass with identical photons impacting? Well, if you don’t invoke causality, you can just about get away with anything anomalous.

The other accepted answer is that any one photon is in a superposition of states. It can be in two places at the same time, so it can both reflect, and pass through the pane of glass at the same time. Either that or the photon has awareness of its external surroundings; it has a mind of its own and decides what it wants to do!

Superposition of state has been experimentally demonstrated via the classic quantum double slit experiment whereby particles, like a photon (but any type of particle will do, like an electron) fired one at a time at two parallel slits, will pass through both slits and thus will interfere with itself and cause a classic wave interference pattern on a target board behind the slits. The only logical conclusion has to be that one particle was in two places at the same time. Personally, I find that absurd, but it’s hard to debate hardcore experimental results.

The one flaw I find in that standard pane of glass situation explanation is that if the photon is in two places at the same time, then both the inside reflected image and the external image – the pass through the glass image – should be equally as vivid. Usually the pass through the glass image is the more obvious of the two superimposed images assuming just one light source, say external sunshine, or the reflected image is the stronger, assuming the prime light source is inside, like say at night.

To be continued…

More Random Thoughts In Physics

* In our Universe there are two kinds of astronomical objects. There are cosmic faucets like stars and anything else that gives off or reflects electromagnetic (EM) waves. That’s the cosmic “In Tray”. Then there are cosmic sinks and drains that absorb electromagnetic waves – Black Holes, the cosmic “Out Tray”.

It would seem to me that over the course of 13.7 billion years, an awful lot of EM (light, IR, UV, radio, microwave, gamma-ray, etc.) photons, not to mention neutrinos and cosmic rays, would have gobbled up and removed from the Universe’s inventory by being sucked into and forever residing in the insides of Black Holes. Since all astronomical observations, hence conclusions about the state of the Universe, rely on the detection of that which is emitted or reflected by cosmic faucets, then it stands to reason that in order to arrive at valid conclusions, what cosmic sinks and drains remove from the Big EM Picture must be taken into account. But is it? I’ve never read any account where the removal of EM photons from the Universe’s inventory has been considered.   

One example that springs to mind is the minor temperature variations in the cosmic microwave background radiation (CMBR) – perhaps those slightly cooler spots are due to a large Black Hole between our measuring device and the CMBR that is sucking up those microwaves before they reach our measuring telescope or space probe or high altitude balloon. I seem to recall cosmologist George Gamow back in the 1940’s making a theoretical prediction that the (then undetected) CMBR would be somewhere between 5 to 7 degrees Kelvin, instead of the roughly 2.7 degrees Kelvin that eventuated. Perhaps, the overall cooler than Gamow expected CMBR is due to Black Holes sucking up lots of those CMBR photons over all those billions of years.

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* Another case of non-causality that’s oft given is when an electron gives off a photon, loses energy, and drops to a lower ‘orbit’ around a nucleus. The opposite isn’t lacking in causality however. A photon is absorbed by an electron which gives it additional energy which kicks it upstairs into a higher ‘orbit’ around a nucleus. Now it’s nuts to suggest that a process has causality in one direction while lacking causality in the exact opposite direction. We may not know why an electron gives up a photon and loses energy in the process, but there is most definitely a why causality – of that I’m convinced.

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* To be honest, I reject the idea that space itself is expanding. To me distant galaxies are expanding farther and farther apart throughout an already existing space. That makes way more sense. Expanding space appears to me to be a case of getting a free lunch – something from nothing – in violation of standard conservation principles.

Is there any actual observational evidence that proves conclusively that it is space expanding and not cosmic flotsam and jetsam moving apart through existing space? Not to my knowledge but I can think of a possible test that might conclude the issue. Two objects receding apart, like the Earth and the Moon (due to tidal forces) are going with the expanding space grain and should be separating more rapidly than otherwise would be the case due to tidal forces alone. The experiment, measuring the increasing Earth/Moon separation should be a relatively easy experiment to do. Due to the reflective mirrors left on the lunar surface by the Apollo moonwalkers we know the Earth-Moon distance to extreme precision. It should be straightforward whether the Moon is receding from the Earth faster than tidal forces can account for.  

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* The cosmos is easily divided into matter and energy related ‘things’ (products of nature) and space and time related ‘not things’ (concepts invented by humans and maybe by other animals). IMHO, ‘things’ are probably those which ultimately reside in the world of the quantum and are discrete. Many ‘not-things’ can be divided and divided indefinitely and are continuous.

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* If an electron acquired enough mass (say by being accelerated to near light speed), would it become a Black Hole, and if so, would the ‘inside’ still be an electron, which after all, is considered a fundamental particle? 

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* If you like symmetry, then the most perfect object of all things symmetrical is a sphere.

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* We frequently read of a “world without time” or “time standing still” or “time doesn’t exist” when it comes to that never-never-land of singularities, be then Black Hole related or that which was at the moment of the Big Bang which somehow created time. I consider that an impossibility since the absence of time means that nothing changes or conversely if nothing every changes it would be meaningless to talk about the existence of time. But the froth and bubble of the vacuum energy is omnipresent (even inside a Black Hole or the structure that was the Big Bang event) and that involves change and therefore the concept of “no time at all” is kaput.

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* It is said the electron is a fundamental particle that cannot be divided or split into simpler components. An electron can of course be converted to energy (all mass can be) say by coming into contact with a positron, the electron’s antimatter alter ego. An electron can emit and absorb a photon, but it doesn’t decay into anything simpler. So I gather if you could smash two electrons head on with as much oomph as one could muster, you’d end up with as close to as makes no odds, that is nearly, a case of the irresistible force failing to move (shatter) the immovable (un-shatterable) object. Another case illustrating the irresistible force and immovable state of affairs – it is impossible to isolate a quark (they come as a trio take all) or its force particle, a gluon.

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* Space is not the final frontier. The ultimate challenge is to ‘boldly go’ past the event horizon of a Black Hole and see what’s to be seen. 

The Quantum Perils of Schrodinger’s Cat

How can you have a cat that is both alive and dead at the same time? Such was the question quantum physicist Erwin Schrodinger posed in rebuttal to the weirdness of the Copenhagen Interpretation of quantum physics, an interpretation that he in fact through his theoretical research contributed to. He ultimately rebelled!

When debating the nature of quantum physics, you question what does it all really mean? One of the central points requiring pondering features a thought experiment by physicist Erwin Schrodinger. He, along with Albert Einstein, didn’t agree with the idea that probabilities rule the quantum universe, and that observations or measurements were central to turning a probability into a certainty. By linking a quantum uncertainty event, with a macro outcome, Schrodinger hoped to show the absurdity of the former.

Schrodinger’s Cat has got to be one of the strangest thought experiments ever conceived, but it was conceived with the idea of putting the boot into the Copenhagen Interpretation of all things quantum.  The Copenhagen Interpretation basically means that everything is in a state of probability until, and only until, an actual observation or measurement is made; then, and only then, probability morphs into reality and certainty. Prior to that observation or measurement, the various possibilities are said to be in a state of superposition. Translated, if you throw a dice and it rolls under the sofa out of sight, the top value of the dice is in a state of six superpositions. The top of the dice is at the same time simultaneously one, two, three, four, five and six. That superposition of state, that combination of all possibilities is called the wave function of, in this case, the dice. Only when you remove the sofa and look will the six probability superpositions collapse (the collapse of the wave function) into one actual value. The point is, according to the Copenhagen Interpretation, prior to looking, the top face of the dice actually, in reality, has a value of one, two, three, four, five and six - simultaneously.

Okay, now back to the cat. The idea is that you have some unstable (radioactive) atom, and there’s a 50/50 chance that it will go ‘poof’ and give off a decay particle within one hour. That’s the quantum or micro bit. Now you have a box that contains a Geiger counter or some radioactive decay particle detector (that’s part of the macro part). You also have a hammer in the box poised over a glass vial of poison gas (also part of the macro part). If the Geiger counter detects a decay particle, it triggers a switch which releases the hammer which smashes the vial, releasing the poison gas. Oh, there’s also a cat in the box (the really essential macro part). After one hour, there’s a 50/50 chance that the cat is either alive or dead. That’s what rational people would say. Some, those of the Copenhagen Interpretation School, would argue that the cat exists in a dual state of both 50% aliveness and 50% deadness until such time as an observer looks into the box and measures the cat’s 100% aliveness or 100% deadness. Then, and only then, does nature make up her mind (in quantum theory, the wave function – a measurement of probability – collapses to an exact value) and you find either a dead cat or an alive cat, which tells you whether or not the radioactive substance did, or did not, emit a radioactive decay particle. In a way, the cat itself serves as a sort of Geiger counter!

This thought experiment was to illustrate the apparent absurdity that in quantum theory some ultimate outcome can have before-the-fact equal but mutually exclusive possibilities (something can both be and not be at the same time – the upper dice face can be all six values at the same time) or that in quantum physics, there’s no definite state of existence until there is a measurement or observation (same difference).

The idea is that if in the micro or quantum world something can have equal but mutually exclusive possibilities (again, an outcome can both be, and not be at the same time - wave-particle duality comes to immediate mind), yet the macro or classical world is made up of micro or quantum bits, then that suggests that macro objects (like a cat) can simultaneously exist in two mutually exclusive states or possibilities (the cat can both be, and not be, alive at the same time). In this case, the cat is both alive and dead until such time as someone looks!

Perhaps a better analogy is in showing how probability remains probability until an observation is made is in a hand of cards. All possibilities are equally probable, all possibilities are realised in actuality, but you don’t know the specific outcome, your precise hand, until you look and the probability wave function, that superposition of all possible outcomes, collapses to one, and only one certainty. The observer is the be-all-and-end-all.

On that point, does it have to be a human that does the measuring or observing if all it takes is an observer to collapse the wave function in order for Mother Nature to decide either this or that? Could any observer do? I mean the cat itself is an observer! So if after only one minute a decay particle is given off, the cat will observe the results (hammer falling; vial breaking) just prior to dying, and there will be a dead cat in the box for the next 59 minutes. What if an insect crawled into the box and observed the cat. What about a bacterium in the box. Would nature, via the bacterium then decide that the cat is to be declared really dead and act accordingly? What if a computer, or some form of artificial intelligence or a robot did the observing? Of course it doesn’t have to be a visual observation. I mean if you hear the cat meow, the cat is alive. If you smell the rotting corpse (or the poison gas), then obviously the cat is dead. If you feel the cat and it’s moving, then it’s obviously alive, and so on.

However, back in the macro world of the relatively very large, to me it’s obvious that there’s no bloody way from a human perspective of knowing after one hour if the cat is alive or dead without observing (via one sense or another). One thing the cat most certainly isn’t is both alive and dead at the same time and I think it’s absurd to suggest otherwise – yet that remains one valid interpretation of quantum physics. Is there a way of knowing, without peeking, whether or not that unstable (radioactive) atom emitted a decay particle?

I suggest replacing the vial of poison gas with nitro-glycerine, or for even greater effect, say a thermonuclear bomb (and leave the cat out of it). After the one hour is up (if not before), there will be no doubt, no need for debate, no need to even look, about whether there was, or was not, a radioactive decay particle emitted. There cannot be simultaneously both an intact and unexploded, and an exploded vial of nitro (or a thermonuclear bomb). It’s either/or time.

What this thought experiment actually tells us about quantum physics remains a bit of a philosophical puzzlement to me I’m afraid, and the fact that it’s discussed in nearly every book on quantum physics suggests that it has lost none of its strangeness.

There’s another aspect to this that’s equally as strange. Both the radioactive atom and the cat are entangled. What that means is that if you know the state of one, you know the state of the other. Say you observe the radioactive atom and note that it hasn’t decayed; it hasn’t gone ‘poof’, then you know, instantaneously, that the cat must be alive. If you note that the atom has gone ‘poof’, you know the cat is dead – instantaneously.  Ditto, if you observe that the cat is alive, the atom didn’t go ‘poof’; if you find a dead cat, the atom did decay. Again, if you know one outcome, you know the other outcome – instantaneously. That’s true even if the cat and the radioactive atom were on opposite sides of the observable universe. You have received a bit of information faster than the speed of light! When you think about it, information usually has to travel from a source (say from a computer screen or a flash of lightning or the sound of a gun going off) through to your senses hence to our brain. That takes a finite amount of time. It’s not instantaneous. Because in an entangled situation you can receive information instantaneously – faster than light speed – Einstein was not at all amused. He’s quoted entanglement as being a case of ‘spooky action at a distance’. The more usual thought experiment is the creation of a matter-antimatter pair of particles that go their separate ways across the cosmos. Millions of years later, they are on opposite sides of the Universe. If someone ultimately observes one of the pair, then that observer instantaneously knows the state of the other particle even though that particle is so far away that it normally would take millions of years for that state-of-the-particle information to reach the observer: spooky action indeed. 

Still, when it comes to the nitty-gritty of trying to pin down the specifics of quantum activities, all is probability, and things can both be and not be at the same time with equal probability, only becoming either/or when the observer struts her stuff and observes. [The observer can be an instrument, but ultimately that instrument transmits the observation to the human that operates the instrument.] But what if there is no observer? Would the cat remain in a limbo state for all eternity? Clearly that’s not, and can not be, the case. The cat is either alive, or it is dead, and the observer be damned! The observer is irrelevant. There seems to be a philosophical if not an actual physical contradiction here. That was Schrodinger’s point.

There is one other fly in this ointment. You have the cat-in-the-box experiment. After one hour an observer enters the room and looks into the box. The wave function collapses and as far as that observer is concerned, the cat is now dead, or alive. But now what about the state of the cat to people outside the room? As far as they are concerned, everything is still in a superposition of state. The cat is still in limbo. Extend that to people in another building, in another suburb, in another city, state, or country. Even if everybody on Earth knew the state of the cat after one hour, what about an astronaut on the Moon? Is the cat still in limbo because an extraterrestrial light years away hasn’t received the news? As far as that extraterrestrial is concerned, the answer has to be ‘yes’, even though all Earthlings know that the state of the cat is no longer the subject of speculation.

Perhaps when all is said and done, quantum paradoxes, well weirdness anyway, explains the most popular interpretation of quantum physics. It’s called the ‘shut up and calculate’ interpretation. In other words, just do the experiments; just crunch the numbers; just apply the technology, and don’t worry about what it all means! 

Addendum: Consider the following real and verified experiment – send one photon at a time, say one per minute, at a beam splitter – a half-silvered mirror. The important bit is that one photon starts and ends its journey between the device that emits the photon and the device that detects the photon, before the next photon is released. The photon has a 50-50 chance of going straight through the half-silvered mirror towards a fully reflective mirror, which then reflects off that and heads back towards the half-silvered mirror where it will be further reflected towards a photon detector. Or, the photon when originally emitted will be reflected off the half-silvered mirror. If the photon is reflected, the photon would then again meet a fully-silvered mirror and be reflected, heading back towards the beam-splitter (the half-silvered mirror) to be directed to the photon detector. Thus there are two possible pathways – call them the ‘alive’ path and the ‘dead’ path. The two pathways are identical in length. What happens is, the upshot of the experiment is, at the photon detector, the detector detects a classic wave interference pattern, against all possible expectations. That means the lone photon interferes with itself, which means the photon took both pathways, and thus was in two places at the same time, and thus was both ‘alive’ and ‘dead’ at the same time! Now if you peek, the lone photon’s wave function, the superposition of states, will collapse and you’ll find the lone photon either on the ‘alive’ path or on the ‘dead’ path – either/or, not both. No wonder Schrodinger invented his hypothetical dead-alive cat to illustrate the absurdity of it all. Alas for Schrodinger, the photon experiment has been done, and the dual state of alive-dead verified. 

Parallel Universes: Part One

Parallel universes, or alternative universes or mirror universes have had a long run of popularity in science fiction and science fantasy, in both print and visual formats. One need only look at an “Alice in Wonderland” or look no further than the “Star Trek” universe (our Universe in less than obvious disguise) to view the near endless plot variations that such parallel / alternative / mirror universes provide our heroes and heroines. Do they actually exist and do they explain anything?

There are apparently two theoretical counterparts in our real world, or in our physics. Firstly, there’s the idea that from the beginning, there’s an infinite number of parallel universes where all things that can happen, do happen. Our Universe is just one of that infinite set. In five of those universes, you 1) flip a coin – in one, it’s a heads you flip; in another, tails; in the third, the coin stands on edge! Or, in a fourth universe you decide not to flip a coin at all, or in universe #5 you decide to flip something else instead.

The other theoretical set of parallel universes is a set that ever increases, staring with just one. Universes split whenever an either/or choice is forced upon it, such that all results that can happen, happen. In this (our) Universe you decide not to flip a coin – but that decision results in a division, the universe splits and in that split, in the new universe, you do flip a coin. In that universe it comes up heads. But, that universe then splits into two and yet another universe where your flip has tails comes up. There’s also another universe where the coin lands on edge! There’s also a universe that originally splits off where you decide to flip something other than a coin. This is known as the ‘Many Worlds Interpretation’ theory, (which resulted out of a need to explain certain quantum phenomena). With every passing second, more and more universes branch off (actually trillions per second).

I’ve never been a fan of the Many Worlds Interpretation of all things quantum. That is, the universe keeps splitting each time it comes to a fork in the road. The question of where all the matter/energy comes from – created out of nothing apparently – I’ve yet to see addressed in the texts. But, many top notch scientists adopt it – perhaps as the least of all the evils certain quantum phenomena dish up. As to where they fit, all those extra universes, that’s not as much of a problem. A motel with an infinite number of rooms never has to put out a ‘no vacancy’ sign – if you get the analogy. Oh, the Many Worlds Interpretation also means that there’s no such thing as free will. You may think you have free will in deciding to wear your red dress instead of your green dress, but in the Many Worlds Interpretation, you do both – so no free will.

However, I myself go for the Copenhagen Interpretation* – when you come to a fork in the road, one and only one choice is made – the other possible choice(s) are never realized and ultimately never have any reality. But, if you start out from scratch with an infinite number of universes, or at least a vast number, then the issue of ‘where’ all the universes are is irrelevant, and the creation of all the stuff that makes them up is equally irrelevant. In the beginning, it was so!

You can have an infinite number of universes in an infinite amount of space. An analogy – there are an infinite number of whole numbers like 1, 2, 3, 4, 5, 6, etc. There’s also an infinite number of even numbers such as 2, 4, 6, 8, 10, 12, etc. Ditto an infinite number of odd numbers. Yet the infinite set of even numbers, plus the infinite number of odd numbers, equals the infinite set of whole numbers. Infinity + infinity = infinity! Or, if you like, think of your house (volume) with just one molecule (universe) in it. You’d agree there’s room for one hell of a lot more molecules (universes). If your house had infinite volume, then…

I had always assumed, and followed the assumptions of others infinitely more brilliant than I, that such theoretical constructions, such parallel / alternative / mirror universes, was forever beyond our actual reach – works of fiction aside of course. We could construct them as an intellectual exercise, but could never verify and understand the actual existence of these mental or thought experiments. That’s because these universes, if they exist, would not be part of our space-time continuum and thusly we could never interact with them.

But what if that assumption is wrong? What if parallel / alternative / mirror universes not only exist, but can and do interact with ours, and thereby give some additional credence to the adventures of our “Alice in Wonderland” and “Star Trek” characters, not to mention the reputations of those physicists who propose infinite universes or Many Worlds Interpretation theories. 

Micro & Macro Mysteries: Well, those assumptions just might now be put to the test. I’d love to be able to say I thought of this idea, even independently, it’s just that brilliant. Alas, I didn’t, and I’m kicking myself because it’s just so simple and elegant.  The credit for this goes to physicist David Deutsch, and for a fuller and better outline of his proposals, see his book cited below**. 

The basics are as follows and deals with the paradoxical and famous ‘double slit’ experiment with light – an experiment with photons.

If you shine a light (millions of photons worth) at a slit, you’ll get a blob of light on the surface behind the slit. No problems – the photon ‘bullets’ go through the slit and impact on the surface behind.

Now you shine the light (millions of photons) at two slits. Contrary to expectation, you don’t get two blobs of light – one opposite each slit – but a classic wave interference pattern of alternating light and dark areas on the surface behind. So photons aren’t ‘bullets’; light must be a wave.

Thus is demonstrated the classic wave-particle duality or paradox of light. Is light a continuous wave, or is it a collection of individual ‘bullet’ particles?

Instead of firing millions of photons at these slits at a go, redo the experiment by firing off photons one at a time – say one per hour. That can actually be done. If you fire the one per hour photons at a single slit, the picture that emerges over time is your blob of light behind the slit. Photons are behaving as ‘bullet’ particles as before.

Now, fire the photons – one per hour – at the two slits. Clearly, you’d expect two blobs of light to ultimately form on the (say photographically sensitive) surface that is behind each slit. Sometimes the single photon would go through one slit; sometimes the other. Alas, you still get a wave-like interference pattern! How can this be? What’s interfering in real time with the actual photons that you’re shooting off?

The only object capable of interfering with photons, to cause wave-like interference, an alternating light-dark pattern, is other photons. But there are no other photons in the vicinity if they are shot out at one per hour and your photon source is the only photon source!

The inescapable conclusion is that there must be other photons around that can’t be detected (seen). Call these photons virtual photons, or shadow photons or ghost photons. Where do they come from? The answer is from our parallel / alternative / mirror universes. There is therefore a form of weak interaction between universes.

How do they, parallel universe photons say, actually get here? Well, at the quantum level, all manner of virtual particles pop into and out of existence from what’s called the vacuum energy. At the extremely microscopic level, what’s often called the ‘quantum foam’, is a level seething with activity, including the popping into and out of existence of micro wormholes, wormholes that can connect one universe with another, even if only for nanoseconds. But, that’s enough to allow the transfer of micro objects, like photons, and electrons, etc. from one universe to another. It’s like seeing the ocean from space. It looks really smooth and tranquil. However, at rowboat level, there’s this twenty foot wave about to come crashing down on top of you.

To be continued…

*But with one very, very important caveat. The Copenhagen Interpretation of the quantum requires that Nature makes up Her mind when, and only when an observer or an observer’s measurement is made. Until then all is probability and nothing has reality or actual existence. The Moon has no reality unless someone is observing or measuring it! To me, observers are irrelevant – reality is reality, with or without observers. 

**Deutsch, David; The Fabric of Reality; Penguin Books, London; 1998:

Can Black Holes Evaporate? Part Two

While there is a constant transfer of matter and radiant electromagnetic energy (photons) between bodies throughout the cosmos, there are sinks, ultimate final resting places where matter/energy can retire to and be removed from the rest of the cosmos. These cosmic sinks are Black Holes. But is that retirement permanent, or can stuff re-enter the cosmic workforce? Can Black Holes evaporate? The theoretical short answer is “yes”; the long answer is “no”.

Continued from yesterday’s blog…

Clearly a Black Hole isn’t isolated from the rest of the cosmos and objects therein. If you were just outside the event horizon you’d ‘see’ photons (of all wavelengths) because you’d see stars and galaxies, etc. just like you can locally. Neutrinos would still pass right through you on their way to their doom once passing through the event horizon. The Universe is full of interstellar and intergalactic atoms and molecules and dust and of course lots of larger stuff a Black Hole can snack on. Black Holes will sweep up stuff just like Earth does, only more so since it has more gravity with which to grab hold of stuff with, and also because once caught there’s no escape for the cosmic fish. Unlike Earth, everything that crosses that event horizon, that hits the Black Hole, won’t be reflected back (like photons). Neutrinos that can pass through light-years worth of solid lead without even ‘breathing hard’ will be imprisoned when they try that trick in a Black Hole’s inner sanctum. And of course atoms, molecules, interstellar dust, the big chunks will also get imprisoned.  

But we can imagine an idealized cosmos where all Black Holes have swallowed up all existing radiated particles (photons), all the atoms,  molecules, the dust and all the bigger stuff – all those stars and planets; asteroids and comets; even all that mysterious ‘dark matter’. So you have a cosmos of just Black Holes and the vacuum energy (well maybe a few bits and pieces escaped, but so few to be of no consequence).  Of course there is one further logical extension. Black Holes can swallow other Black Holes. Black Holes can merge to form bigger Black Holes. The final product is that the cosmos consists of one Black Hole – the Mother of all Black Holes – plus the vacuum energy!  So you end up with one Black Hole left standing with nothing left to eat.

Okay, so the only scenario now possible is that this Mother of all Black Holes evaporates via Hawking radiation. It might take trillions upon trillions upon trillions of years, but evaporate it does. Since matter and energy can neither be created nor destroyed, once the Mother of Black Holes has finally gone ‘poof’, the Universe is right back where it started from – full of stuff from photons to fundamental particles which them undergo chemistry to form atoms and molecules and stars and planets and perhaps life – and new Black Holes!

Perhaps this is a new and improved version of a cyclic/oscillating universe! - But then again, maybe not. There’s a fly in that ointment (but I had you going for a while back there!). That “idealized cosmos” was only a ‘what if’ thought experiment.

Firstly, it’s actually very, very unlikely all the Black Holes in the Universe will ever merge together as long as the Universe keeps expanding. Since the galaxies are getting farther and farther away from each other due to that expansion, the collection of Black Holes contained within each galaxy keep getting further and further apart from other clusters of Black Holes contained within other galaxies. It’s like the passengers in one car get more and more remote from the passengers in another car when each car is going at different velocities and heading in different directions.

Now the collection of all Black Holes in any one galaxy could well coalesce into one super Black Hole galaxy. You have a galaxy that instead of containing billions and billions of stars and debris and particles now consists of just one Black Hole – the car only has one occupant. You have a pure Black Hole galaxy, or a galactic sized Black Hole. 

One might end up with a Universe composed of just these pure Black Hole galaxies, all spreading farther and farther apart over time. 

But secondly, there’s another fly in the ointment. All the space that separates these pure Black Hole galaxies from each other isn’t a perfect vacuum, quite apart from the vacuum energy. All the radiating stars and stuff may have been gobbled up within each galaxy, but all of interplanetary space, all of interstellar space, and all of intergalactic space, isn’t pure vacuum. There’s still the ‘it’s everywhere, it’s everywhere’ Cosmic Microwave Background Radiation (CMBR).

So what’s this CMBR?  If you have a massive hot explosion (like the Big Bang event is alleged to have been), and all that heat energy expands and expands, then you’d expect the temperature of the area occupied by that energy to drop, the temperature ever decreasing as the volume that finite amount of energy occupies increases. As the energy expands it gets diluted and thus cools, but can never reach an absolute zero temperature for reasons already noted. And that’s just what we find on a universal scale. There’s a fine microwave energy “hiss” representing a temperature a few degrees above absolute zero that’s absolutely everywhere in the cosmos. That’s the diluted heat energy of the very hot Big Bang – well it has been a long time since the Big Bang event (13.7 billion years worth of time) and that energy is now spread throughout a lot of cosmic volume. That microwave “hiss”, called the CMBR, was predicted way before it was discovered. There’s no doubt that it exists.

Since the CMBR is just photons with very long wavelengths, Black Holes could suck up the CMBR photons as easily as light photons. Removal of CMRB photons, already representing a temperature just slightly about the theoretical minimum – absolute zero – would mean the Universe gets even colder, which it would anyway since the Universe is ever expanding and thus available electromagnetic energy (photons) is ever diluting. Combining the two effects and the Universe is a chilly place indeed and will get even colder.

However, it’s probably not possible for Black Holes collectively to swallow up all of the CMBR since there will come a point of diminishing returns. What happens when the temperature of Black Holes equals the temperature of the Universe at large – the CMBR? The answer is thermal equilibrium like when your hot cup of coffee cools off to room temperature. Input into Black Holes from the CMBR will equal output via Hawking radiation. For every photon emitted via Hawking radiation, a CMBR photon gets sucked in. What does that mean? It means a Black Hole can not evaporate.

What about very tiny (micro) Black Holes that are relatively ‘hot’? Might they go ‘poof’ before thermal equilibrium is achieved? Will the contents of the Black Hole evaporate into the surrounding cosmos before they can equate to the surrounding temperature? The analogy might be like a hot drop of water could evaporate into the cold atmosphere before the liquid water drop can attain the temperature of its surrounding environment.

Even so, I still imagine that in the current matter and radiation dominated Universe, incoming would still exceed outgoing.

Of course if you could take a Black Hole, isolate and shield it from the rest of the cosmos and all that it contains, so all you have is the Black Hole and its internal energy (including the all pervading vacuum energy therein). An isolated Black Hole would be in a setting equivalent to putting it into an absolute zero temperature environment. If that’s the case then outgoing would exceed incoming since there could be no incoming, and therefore that Black Hole would then radiate and slowly evaporate and eventually go ‘poof’. BUT, and there’s always a BUT, I can not envision any scenario where a Black Hole can exist in such a theoretical isolation. So, Professor Hawking is quite correct – in theory. In practice, in the here and now, input exceeds Hawking radiation output, and even in the unimaginably far distant future equilibrium will be established where input equals output. 

The Nature of Gravity: Part Two

Gravity – we all feel it; it limits much that we can do or build; and we don’t understand it!

Continued from yesterday’s blog…

Presumably for there to be gravity there has to be mass (or matter), so an electron has gravity; you have gravity; the Planet Earth has gravity – and so on. But a photon, that ‘particle’ that carries the electromagnetic force, doesn’t have gravity since it can’t have any mass (because it travels at the speed of light and only something without mass can do that).

So gravity can deflect the electromagnetic force. We’ve all read about that famous experiment where the positions of stars were pinpointed that should be very near the limb of the Sun during a solar eclipse. The starlight from those stars was deflected by the Sun’s gravity and thus, during the eclipse, the stars seemed slightly out of position in the sky. This was in accordance with Einstein’s General Relativity predictions and the merger of theoretical prediction and observational reality elevated the physicist from that of a scientist known and respected by colleagues to that of international superstar known to the masses – the scientist who overthrew Newton’s Theory of Gravitation. There’s another astrophysical effect of the deflection of electromagnetic radiation by gravity, and that’s known as gravitational lensing. While predicted by Einstein, he felt it would never have any practical applications. But today’s astrophysicists have used the phenomena – that of massive (high gravity) objects in space deflecting and focusing the light (like a lens) from more distant objects behind them – to study same. It’s by this technique that the presence of ‘dark matter’ has not only been confirmed, but mapped, as ‘dark matter’ has gravity and can act as a gravitational lens!

Can gravity deflect gravity? In Newtonian physics, the gravitational force travels instantaneously. If the Sun were to somehow vanish now, we’d feel the Earth orbital effects, now. In Einstein’s Special Theory of Relativity, gravity travels at the speed of light, and thusly gravity and EM (of which light is a part) share a common bond. Thus, if the Sun were to somehow vanish now, it would be eight minutes before we’d notice Earth’s orbit being perturbed. Experiments have to date only proved gravitational influences travel at very close to light speed, but as yet, not an exact match. Close, but no cigar. Of course it’s only fair to point out that these experiments are incredibly difficult to carry out, and the final verdict is still far off.

All the four forces have particles associated with them – particles that convey the force from Point A to Point B. In the case of the electromagnetic force, it’s the mass-less photon. The strong nuclear force has the gluon. In the case of gravity, the assumed theoretical particle (it hasn’t been actually detected yet) is the graviton.

If the particle assumed to carry the gravitational force (the graviton) travels at light speed, it should be mass-less, and with analogy with the photon, be deflected by another gravitational field. If a photon passes near a Black Hole (a high gravity object), its pathway will be bent. If a graviton (say part of a gravitational wave – something predicted by Einstein’s General Theory of Relativity) were to pass near the same Black Hole, its pathway should be equally bent. If a graviton has some mass and thus travels at somewhat less than light speed, that too will show up as a change in its pathway as it passes close to a Black Hole. Equally, a graviton, if there is such an animal, should be sucked into a Black Hole if it hits the Black Hole’s bulls-eye.

It might be surprising that if gravity can deflect gravity as well as radiation, then how can gravity ‘escape’ from a Black Hole and radiation* can’t? Of course gravity is an intrinsic property of mass, and there’s certainly lots of mass in a Black Hole, so obviously a Black Hole has gravity and it’s not as if it were escaping or leaking out. Of course one could, perhaps should, argue that gravitational waves are just ripples in space-time geometry, and gravity is just geometry, and geometry can’t be sucked into a Black Hole the way matter/energy can be. Translated, gravity again is just different – it’s not a force like the other forces, it shares no commonality with electromagnetism or the strong and weak nuclear forces, its just geometry in which case there might be no need for a gravitational force particle.

An interesting side question is can light deflect light? Unfortunately, light doesn’t stand still, but what if, as a thought experiment, one fired a laser beam in one direction and another laser beam at right angles to it, but say just a fraction higher (so the two beams don’t make contact). Would the pathways of the two laser beams alter as they crossed? Would two laser beams fired off in parallel slowly be drawn together and eventually merge? How about two laser beams fired head on towards each other? I suspect the two beams would just pass through one another. To the best of my knowledge, light only interacts with light as wave phenomena, not as particle phenomena, causing constructive or destructive interference. So, two beams at right angles, or fired in parallel, wouldn’t display any particle sorts of properties – that is, deflections. Again, the photon is mass-less so shouldn’t have any sort of deflection influence on other photons. That’s my guess anyway. So…

John’s musings one: gravity is a quantum phenomenon; gravity is not a continuous phenomenon; there is a unit of gravity that can not be subdivided; the graviton is the fundamental particle that conveys the force we feel as gravity. There will eventually be an experimentally verified Theory of Everything.

John’s musings two: gravity is a consequence of geometry. Mass distorts space-time’s geometry (which would be absolutely flat in the absence of any mass) which in turn distorts how mass moves (which would be in a straight line in the absence of any geometry other than flat space-time geometry). Gravity has bugger-all to do with quantum physics and just can not be reconciled with it. There is no fundamental unit of gravity and no need for a gravity-bearing particle.

Now this mass/space-time dynamic is very interesting. Mass tells space-time how to curve or warp (which determines the geometry); space-time geometry tells mass how to move, movement which in turn alters the geometry, which in turn alters the motion, and so on, and so on. Very dynamic! It’s also very circular, sort of like the chicken and egg question.

How exactly does space-time affect the motion of mass? Well, that’s pretty straight forward – I think. It’s one of the fundamental axioms of physics that an object once set in motion, stays in motion, and travels in a straight line – unless acted on by an external force. If you hit a hockey puck across the ice, it keeps on going on (if you ignore friction) in the direction you hit it. If some other player then hits the puck, the puck (probably) changes both speed and direction. But, what if, instead, the puck hits a slight slope in the ice. The puck will change direction. Geometry has affected the motion of a mass. Geometry has mimicked a force. Or, take the unfortunate S.S. Poseidon sailing along on a smooth sea until a sudden rogue wave rudely alters her course and speed in real quick-smart time. The sea’s geometry changed, resulting in, in this case, a good cinema experience!

So how exactly does mass warp space-time? I don’t know exactly (in case you were expecting a revelation at this stage). You might think the entire concept crazy. I mean we’ve all seen the Sun and the Moon, and the Apollo astronauts have seen the Earth from afar, and we know these objects have mass and hence gravity, but have you, or the astronauts, seen any warping of space-time in the vicinity of the Sun, Moon and the Earth (unlike that – by analogy – the bowling ball on the rubber sheet illustration beloved in all physic’s texts)? Okay, there’s noting apparent to the naked eye that anything is warped, there’s no psychedelic effects apparent, no distortions, etc.  The Moon doesn’t appear as a shimmering now-you-see-it-now-you-don’t object. But then, we do have that starlight defection experiment verified during solar eclipses (tick to Einstein). Perhaps these worlds aren’t massive enough to imprint their distortions on our retinas. The more the mass, the more dramatic would be the result, and anyone who has seen long duration time exposure photographs of massive galactic-sized objects, the gravitation lens at work, witnessed the formation of Einstein’s Rings (or arcs), has certainly seen space-time warping or the pathway of light deflected by mass (tick to Einstein). 

I suspect the answer as to how exactly mass warps space-time is probably straight forward. As the Earth travels in its orbit around the sun, space (or space-time) has to give way to accommodate our planet. Or, if you toss a ball through the air, the air is displaced as the ball passes through. The air has been slightly, and briefly, warped. Or, back to the S.S. Poseidon, her sailing along on calm seas causes displacement in the ocean and generates bow waves causing the ocean’s geometry to change. The bow waves, radiating outwards (like gravity waves?) hence cause a rocking of a small rowboat far away.

So, experimental conclusions (to date): Einstein one; quantum physics/string theorists zero.

In matters of theoretical physics and accompanying mathematics, one must temper the ‘thought experiment’ results with liberal does of healthy common sense – attention string theorists. In matters of observational and verified experimental physics, healthy common sense must take a back seat to confirmed results. Despite gravitational lensing, etc. gravity (the how and the why) still seems to reside largely in the theoretical realm, and I’m sure we’d all like to see this very mysterious force emerge in the light of total understanding based on a lot more experimental data. In the meantime, in the here and now, string theorists, and those proposing models of quantum gravity, better get their experimental act together!

A further recommended reading about gravity:

Schutz, Bernard; Gravity from the Ground Up: An Introductory Guide to Gravity and General Relativity; Cambridge University Press, Cambridge; 2003:

*Actually theoretical astrophysicist Stephen Hawking showed that Black Holes weren’t entirely black; some radiation can escape from them, know known as Hawking Radiation. It’s actually a now and then quantum phenomena. Normal everyday electromagnetic radiation can’t escape from a Black Hole once trapped behind the Black Hole’s event horizon. However, the energy associated with a Black Hole, via Einstein’s famous equation relating mass and energy, can morph into virtual particles outside the Black Hole’s event horizon – that region and below of no escape.