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.



Time To Question Time: Part Two

Time is the most mysterious concept that you are likely to think about. You know exactly what time is, unless you actually have to explain it and then things bog down. If you admit that time is pure puzzlement, well you’re not alone as the nature of time has been endlessly debated by thinkers, good, bad and average, ever since humans had the ability to think. Okay, I’m a thinker, so here are my thoughts in Q & A form about time.  

Continued from yesterday’s blog…

Q. Is time travel to the future possible?

A. Time travel to the future is easy – you’re doing it right now at the rate of one second per second – boring – or when you fall asleep (or pass out drunk), next thing you know you are in the future, ahead by several hours. You’ve skipped or jumped over some interval of time. That’s what one usually means by travel to the future. It is jumping over some significant interval of time without having to experience or live through it, like say going from 2013 to 2015 and avoiding 2014 entirely. Of course when you arrive in the ‘future’, be it the following morning or by skipping 2014, it’s no longer the future but the present – the ‘now’. It’s actually impossible to be in or to exist in the future, it’s only possible to head towards the future, which you do anyway at the rate of one minute per minute. 

I guess you could construct a philosophical argument that relative to your point of view of yesterday, if you say skipped a day and landed in tomorrow, you are now in the future, but such convolutions don’t get us very far since the you that existed yesterday no longer has any existence or meaning either today or tomorrow or post tomorrow. In fact, the person you call “you” that existed one second ago has now come and gone and passed away into history. The only you that has any reality is the person you call “you” that exists right now.

Apart from your normal modes of time travel into the future, you can accelerate the process. There’s also Einstein’s Relativity twin paradox whereby relative to an outside observer, time, as in rate of change, slows down for someone who is travelling at velocities that are approaching some goodly fraction of the speed of light. So, a twin who heads off at a rapid rate of knots and boldly goes, when returning to meet and greet her stay-at-home twin, will find that though twins they might be, their ages are now different. The stay-at-home twin has aged more quickly, or the boldly going twin has aged more slowly depending on your ‘relativity’ point of view, which isn’t really a paradox, rather the consequences of what happens when you travel at a very rapid rate of knots relative to someone who doesn’t.

However, the same philosophy or argument from those several paragraphs above applies in that you, in this case the you that’s the boldly going twin, is never in the future, only in the now or existing in what passes for the present (along with your stay-at-home twin). That applies even if that present is tens of thousands of years after you were born, which is possible (and thus your stay-at-home twin has long since died and returned to dust). No matter which way you slice and dice things, you only have reality in the present that you find yourself in. 

Q. And what do you conclude about the viability of time travel to the future from the above?

A. Ultimately, to my way of thinking, time travel, even to the future (by skipping over periods of time), is impossible since again time is a concept and not a thing, like a road or a river you have to travel continuously on, up and down on. If time is just a concept, then time travel is illogical.

Q. Is there any other likely impediment to time travel?

A. Yes there is. When you visualise standard time travel stories or films to the past or to the future, your time machine or device keeps you firmly attached to the same set of terrestrial coordinates from which you started, so if you say start in New York City (2013) and go plus or minus say 200 years either to the future (2213) or to the past (1813), you’ll end up in the New York City of that time. That’s bonkers! In that 200 years, either way, Planet Earth on which New York City is attached, but you are not, has moved. Planet Earth is attached to the Sun (gravitationally) and the Sun is in orbit around the Milky Way Galaxy, which itself is moving in space, so when you materialize 200 years in the past or future, the odds are extremely likely that you will materialize into the depths of outer space! Even if you ignore all that, the Earth will not make an exact number of solar orbits and axis revolutions over 200 years to bring you back into exact alignment with the terrestrial coordinates you started out from. So, you just might materialize smack dab in the middle of the Atlantic Ocean. Oops! What one really needs is a time and space machine like the Doctor’s TARDIS where you can also set spatial coordinates. 

Q. Have all billionaires been time travellers to the past?

A. Maybe! It’s easy to imagine looking up say all the long shot horses who won their races in say over one particular year. Now travel back in time to that year and start placing reasonable bets on each ‘long shot’ (that proved a sure thing), make a super-bundle of loot, and hop back to your own era; your own present day and start living the good life. Of course there are many, many variations on this go-back-in-time and get-rich-quick schemes.

Q. We spend our entire lives in the “now” moment, and eternal “now”, yet each “now” moment lasts way less than a nanosecond before the “now” you vanishes into the limbo-land of the past only to be replaced by the future you that was just a theoretical probability that now becomes reality, for just a nanosecond before that you too slips away into the unreachable past. That’s confusing!

A. There’s no real mystery here. There are many examples from daily life of the difference between the continuum and the part of the continuum.

You’re driving along the road in your car. Your car is the continuum since you’re always in your car for the duration (that eternal “now”); the specific section of road you are travelling over is your nanosecond “now” which changes from nanosecond to nanosecond.

You’re swimming with the current in a river. The surrounding water is your eternal “now”; the section of riverbed you’re passing over is your nanosecond “now”. Or, you can reverse the scenario. If you swim exactly against the speed of the river current or flow, the part of the riverbed you are stationary over is now your eternal “now”, while the patch of water around you is ever changing and thus becomes your nanosecond “now”.

If you walk across the stage with the spotlight on you, the light is your eternal “now” but your place on the stage is constantly shifting – your nanosecond “now”.

If you lie in bed all day (and night), the bed is your eternal “now”, but the ticking of the clock, even if only via the changing position of the sun (in the day) and the stars (in the night), or that change from sunrise to sunrise, is your nanosecond “now”.

Note that all of the examples involve motion. Motion is change and change is what the concept of time is all about.  

Q. Does God exist within time or outside of time?

A. There is no God (or gods) so the question is immaterial, irrelevant and has no bearing on the proceedings. But if there is a God(s) they would exist inside of time since to exist is to undergo change and time is nothing but a measure of change. 

Q. When do I exist?

A. Now, and only now. The “you” that existed an hour, even a minute ago is no longer. That past you, actually all those entities you called you (plural) that existed in the past have been consigned to the history books. The “you” that (probably) will exist an hour or even a minute from now, actually all those entities you will call you (plural) that will exist in the future do not yet have reality of any substance.

Q. So again, what is time?

A. One heck of a metaphysical mess!

Time To Question Time: Part One

Time is the most mysterious concept that you are likely to think about. You know exactly what time is, unless you actually have to explain it and then things bog down. If you admit that time is pure puzzlement, well you’re not alone as the nature of time has been endlessly debated by thinkers, good, bad and average, ever since humans had the ability to think. Okay, I’m a thinker, so here are my thoughts in Q & A form about time.  

Are you confused about time? If so, join the crowd. I’m part of that crowd, and I’m confused, but I’ll try to work through my befuddlement via this hypothetical question and answer session which hopefully will enlighten me and you too. 

Q. What is time?

A. Time is a concept, like Wednesday is a concept.

Q. A concept of what?

A. Change. Without change the concept of time is meaningless.

Q. What properties does time have?

A. Time has no properties, just like Wednesday has no properties. Time has no structure or substance; no mass or energy, no colour or spin or charge, it has no associated field, and it exerts no force and has no fundamental particles associated with it. 

Q. Does time have a beginning? Will time ever end?

A. No. Time is eternal. An eternal time removes those nasty philosophical questions of what came before; what comes after?

Q. Can time be created?

A. The concept of time can be created, but only by the mind blessed with some degree of sophistication, but that does not give substance and structure to time itself, any more than the JFK concept of ‘landing a man on the Moon and returning him safely to Earth before the end of the decade’ in and of itself made it so. The concept of a lunar landing is not a real lunar landing. Time itself cannot be created like a soufflé since there are no ingredients that collectively comprise time.

Q. Can time be destroyed?

A. Since time cannot be created, time cannot be destroyed. While that is similar to existing conservation laws, there is no conservation law in existence for time like there is for matter and energy since, unlike matter and energy, time cannot be altered from one form to another, since time is not a thing.

Q. Was the Big Bang event 13.7 billion years ago the start of time?

A. No. Since time cannot be created, the Big Bang banged in existing time which means there was a before the Big Bang. Something had to cause the Big Bang (a change) and that something could only have been an earlier event which happened in already existing time, since an event, a change, defines what time is.

Q. Where does time exist?

A. The concept of time exists only where change exists, and change only exists within that ongoing, yet ever paper-thin slice that we can the “now”. Change neither exists anymore in the past nor does it exist yet in the future.

Q. Are time’s related terms also concepts?

A. Absolutely. None of the following can be placed on the lab’s slab; none of the following are ‘things’, just mental concepts and conventions: past, present, and future; when, now and then; before and after; second, minute, hour, day, week, month, seasons, year, decade, century, millennia, and eon; any of the named days of the week; any of the names of the seasons; any digit that represents a year (i.e. – 2013); any date; yesterday, today and tomorrow; birthday, anniversary and holiday; weekend and weekday; noon and midnight.  A clock or calendar or metronome can be put on the lab’s slab, but a clock, etc. isn’t time, just like a thermometer isn’t temperature, and a Geiger counter isn’t radioactivity.

Q. Is time travel to the past possible?

A. Yes and no.

Einstein’s concepts of General and Special Relativity allow for time travel to the past (and the future), the usual scenario is via a rapidly rotating massive object that can twist space-time around in a loop where the starting point that joins up with itself to form the loop, like a snake swallowing its tail, isn’t any longer at the same point in time. However, the flaw I find with all of that is that this requires space and time, or space-time, to be a thing, which IMHO it is not. Space-time is a concept without substance and structure because both space and time are concepts without substance and structure. Be that as it may.  

The basic argument against going back in time is the creation of a paradox, something along the lines of killing your mother when she was a young girl thus preventing your very existence which means you couldn’t have gone back in time and murdered your mother, etc. Hells, bells, why not just do the suicide properly and go back in time a few months and kill your own self! But any trip back in time will create conditions back then that did not originally exist, and however minor, not only will they become an established part of history, but have that butterfly or ripple effect on down the line – chaos theory. If those new conditions, thanks to your time travelling presence, did not originally exist and now they do, that’s also a paradox as something cannot be and yet be at the same time, and that contradiction extends on down the line as history unfolds differently.

Further, you MUST go back in time (no free will in the matter) to ever create and ensure the conditions that came to pass back when, new conditions that you initially caused – only you never initially caused them since there’s an infinitely recycling causality loop here. You went back in time which caused a certain set of conditions which become a part of established history which means at some point in your life you are required to go back in time to create that certain set of conditions which become a part of established history, all to be endlessly repeated for all eternity. Presumably you couldn’t even commit suicide before you travelled back in time and thus break the cycle.

Of course if the past were somehow changed, then presumably you’d never know it since all records, including those of your memory, would be altered accordingly. But things would be messy if millions of people each travelled back in time and altered this, that and the next thing. History textbooks and other records would be rewritten and altered to conform to all those alterations every second. Then too, what if someone went back in time and altered history to the extent that mankind went extinct as a result – that’s the ultimate going back in time and killing your mother as a young girl!

Here’s a novel concept. Say it is the 10^th of the month. Go back in time to the 1^st of the month and meet and greet yourself. The both of you now wait until the 10^th of the month and then go back in time to the 2^nd of the month where you both can now meet and greet and join up with the other two of you that existed then. Then the four of you wait until the 10^th of the month and the four of you travel back in time to say the 3^rd of the month where the four of you link up with the four of you that existed on the 3^rd. The eight of you now wait until the 10^th of the month and then travel back in time to the 4^th of the month where you group together as a crowd of sixteen. Wait until the 10^th of the month and the sixteen of you travel back to the 5^th and join up with the other sixteen to form a mob of thirty-two, and so on and so on. Starting with just you, you could create an entire army of you!

Q. Where’s the paradox in creating an army just out of you?

A. The paradox here is that you are getting something for nothing, in this case extra copies of you. Where in fact does the extra matter and energy come from that creates that you army?

Q. Anything else?

A. Another reason time travel to the past is suss is that we don’t see any time travellers from our future paying us a visit. Though Einstein’s Special and General Relativity allows time travel to the past, and although the laws of physics are time invariant (they are valid from past to future and future to past), no visitors. Either our descendents don’t have any interest in us, or perhaps there aren’t any – descendents that is – if we go extinct or go back to the Dark Ages sooner rather than later. Or, perhaps time travel just isn’t possible after all or is in the too hard basket.

Q. You lie! What about the Second Law of Thermodynamics?

A. Ah yes, what about the Second Law of Thermodynamics which is held responsible for time’s arrow or the arrow of time (i.e. – things proceed from past (which you remember) to future (which you don’t remember). But the Second Law of Thermodynamics is misnamed since the second ‘law’ isn’t really a ‘law’, just a statement of probability, albeit extremely high probability. When things happen in a statistically probable way (eggs break or scramble; eggs don’t un-break or unscramble) that’s the arrow of time that we perceive. Put in a more thermodynamic context, a boiled egg cools off and heats up the kitchen until both are at the same temperature; the kitchen doesn’t cool down and transfer that energy to the raw egg and cook it.

Q. Anything else?

A. Yes, another postulate has it that one cannot travel further back in time than the time the time machine was constructed. So if our descendents come up with a first ever time machine in the year 2113, they couldn’t come visit us in 2013, though those living in the year 2213 could go back to 2113 (but no farther back).

The way out of that is what about an advanced extraterrestrial civilization’s time machine, say built in 2013 BCE, or over 4000 years ago. Say, what about those pesky UFOs? Instead of ET coming here from out there in their and our present, they come here from there in our present but from their future! The only problem with that is that UFO events and flaps are not clustered around what we would call historically important events, like say the Trinity A-Bomb test in 1945 or the launch of Apollo 11 in 1969 or the sinking of RMS Titanic in 1912. Of course, that they are conspicuous by their absence, well that just maybe our parochialism coming to the fore. Time travelling aliens may have a differing agenda. 

Aliens aside, you could easily imagine a time travelling Travel Agency existing several hundred years from now conducting guided tours to important historical events of their (and our) past, say tours in groups of one hundred per. After several thousand such tours, say to the battle of the Alamo or to Custer’s last stand at the Little Big Horn, things would be getting a mite crowded since each tour has to show up at the same place and date!

Q. And what do you conclude about the viability of time travel to the past from the above?

A. Ultimately, to my way of thinking, time travel, at least to the past, is impossible since time is a concept and not a thing, like a road or a river you can travel up and down on. You can travel in a car, but not in the concept of an automobile.

To be continued…

A Voyage To A Black Hole: Part One

Suicide missions are hardly unknown happenings, so presumably it wouldn’t be too hard to find a volunteer to take a long walk off a short pier and dive into the heart of a Black Hole. Well, let’s trade in the walk and the pier for a spaceship, with our suicidal pilot crewmember willing to boldly go. What might she expect? For that matter what might a chickenhearted outside observer expect to see?

Space isn’t really the final frontier; rather the inside of a Black Hole that’s inside of space really is the final frontier. Only the insanely suicidal need boldly go and explore, as it’s unlikely that the innards of a Black Hole will become a popular tourist attraction for many a millennia to come – if ever.

Okay, we have a depressed, suicidal, boldly going spaceship pilot, and she’s determined to go out in a blaze of glory and make her mark in the history books. No ordinary suicide for this woman! It’s across the event horizon threshold and down the hatch of a Black Hole. I need point out here and explain that technical term ‘event horizon’ – it’s just that location that divides the ability to return home safely from the point of no return, ever.

Countdown: Five, four, three, two, one – we have lift-off on the maiden voyage to boldly go and see what’s to be seen from the inside of a Black Hole.

As far as our suicidal pilot is concerned, everything from launch to crossing the event horizon is as normal as taking the cross-town bus to work. Time will tick by at one second per second; her mass will register normal; length ditto. However, due to Einstein’s concepts in all things being relative, an external observer will see our boldly going pilot’s reality slightly differently. 

An external observer, say relaxing back on Earth with a super powerful telescope, follows ionization trail of the boldly going voyager’s spaceship to the nearest Black Hole. Basically, what this person sees is that as the suicidal voyager blasts off from Earth, picks up speed, her ship and contents (including herself) start to shrink in length, increase in mass, and her rate-of-change (time) ticks by more slowly compared to Mr. Stay-At-Home’s own. Okay, that’s in keeping with Einstein’s relativity proclamations. 

But for some inexplicable reason, I’ve read several times some scientific author suggest that to an external observer, the suicidal pilot will not only be travelling slower and slower by the external observer’s clock as she approaches the event horizon, but in fact at contact with the event horizon her time, again as recorded by the external observer, will have stopped. In other words, the external observer will never witness the pilot’s crossover from outside the Black Hole’s event horizon to inside the Black Hole’s event horizon. The pilot will appear to be frozen in time at the event horizon, yet as far as the pilot is concerned, everything is normal in terms of time flowing at one second per second.

Now that’s a major paradox. The pilot can’t be crossing the event horizon at one second per second, while at the same time being frozen in time at the time of crossing, according to our stay-at-home observer. Of course the paradox is bullshit. To an external observer, time only comes to a screeching halt for someone external to them if they witness that someone travelling at the speed of light. Firstly, that’s a physical impossibility. There’s no reason to believe that our suicidal pilot is crossing the event horizon at light speed. There’s no absolute requirement that our suicidal pilot is crossing the event horizon at the speed of light. She in fact might have fired her retro-rockets to slow down just prior to crossing the event horizon in order to better savour the moment! So, in actual reality, our observer will see the pilot cross the event horizon, albeit at a way slower rate than the pilot herself because the pilot is travelling, hence doing the event horizon cross-over at less than the speed of light. IMHO, some ‘experts’ need to go back and redo Physics 101. 

In any event, once the external observer observes our boldly going suicidal voyager cross the event horizon, the show is over for him. Nothing that’s part and parcel of the voyager, not her ship’s reflected or emitted light, not her radio signals nor information signalling of any kind, will recross the event horizon in the outward bound direction and heading back to Earth. Our external observer can pack away his telescope and get back to more interesting pursuits, like watching daytime television. But that’s not quite the end of the story. 

And so it’s now over to the (never-to-be-revealed) recorded flight log of the voyager on her one-way trip to the Black Hole’s never-never land. Up to and including the crossover from the safe side of the event horizon to the ‘abandon hope all who enter here’ side of the event horizon, all is logged as 100% normalcy. Nothing shrinks, nothing grows in weight (increases in mass), and time does its one second per second thing as it always has done. It’s as easy as a trip from your home driveway to the supermarket parking lot, only once in the grip of the supermarket parking lot, forever in the grip of the supermarket parking lot. It’s a one-way ‘enter’ gate without a corresponding ‘exit’ sign.

Since we have no idea what the inside of a Black Hole actually is, since theoretical physics, quantum and relativity physics, break down into a mathematical mess, what our intrepid voyager will actually observe or experience is anybody’s guesstimate. There does appear to be one consensus however. Gravity rules, OK? Almost by definition there’s a hell of a lot of gravity to contend with once inside the supermarket parking lot – oops, sorry, inside the event horizon.

Now here on Earth, when standing up, gravity is pulling at your feet ever so slightly greater than it is tugging at your head – because your feet are slightly closer to Earth’s centre of mass. Earth’s gravity however is so weak that you don’t know or can’t feel the difference, but tests or experiments with extremely accurate atomic clocks show that this is true. Rate of change – time – is affected by gravity, so a clock atop a tall building runs slightly faster than an identical clock in the building’s basement. Now the gravity of a Black Hole is many, many, many orders of magnitude stronger than it is here on Terra Firma. So, it is speculated that if you are inside a Black Hole, say in free-fall, and say in a vertical position, then the gravity pulling on your feet will be not only vastly greater than if you were on Earth, but also the differential between feet and head will be orders of magnitude greater. Translated, gravity inside a Black Hole is going to stretch you out like a piece of taffy. Like in one of those fun house mirrors, you will be very, very, very tall and very, very, very thin. Ultimately you will be akin to a piece of string or spaghetti, but by that time you’ll be very, very, very dead as the human body wasn’t designed to be viable under such a state of affairs. Okay, that’s the consensus.

To be continued…

Reality: Heads or Tails? Part One

In science as well as in metaphysics there are often competing ideas about what’s real and what’s not real but might be real – an alternate reality not yet proven. Here are a baker’s dozen of examples of what we believe is a truism today, but could easily be shown to be mistaken tomorrow. In one case, the last, tomorrow is already here!

What was reality yesterday (a Flat Earth orbited by the Sun; Unicorns and Dragons, etc.) isn’t of necessity what is accepted reality today, and what’s reality today may not of necessity be reality tomorrow. Here are a few possibilities for tomorrow-land.

1) Quantum Mechanics: The Copenhagen Interpretation (reality) vs. The Many Worlds Interpretation (alternate reality): Actually nobody has a handle on what constitutes reality in the realm of the quantum other than it is a realm of probabilities. When you have a lot of states or things that could be only a measurement or observation will turn one of these probabilities into a certainty. The other probabilities collapse and fall by the wayside once that observation is made. That’s the guts of the Copenhagen Interpretation of quantum probabilities. The alternate reality is called the Many Worlds Interpretation which suggests that all probabilities happen; none is favored; none fall by the wayside. The way that happens is that when crunch comes crunch and its time to turn the cards face up, the world splits as many times as necessary to allow for each possible outcome to achieve reality, one outcome in this world and another outcome in another world. So, right or left at Oak Street? It’s not either/or. In this world you go say to the left. But that very act generates another separate and apart world where you turn right. 

2) Quantum Mechanics Probability (reality) vs. Quantum Mechanics Causality (alternate reality): As noted above, quantum mechanics is the realm of chance or possibilities or probabilities. One thing that is never certain in quantum mechanics is being able to predict certainty, which is certainly not the case with classical physics. There’s no doubt the Sun will rise in the morning; that you can predict eclipses hundreds of years in advance; that you can use the laws, relationships and principles of classical physics to send a space probe to the planet Mars. In classical physics, causality rules: if A, B & C then X, Y and Z will follow. In quantum physics, if A, B & C then X, Y and Z might follow, or maybe not. Not everyone accepts that. Some suggest that lurking beneath quantum’s probabilistic nature lays hidden variables that will restore quantum mechanics to the realm of cause-and-effect. In quantum physics, causality might prove to be your alternate reality.

3) Traditional Particle Physics (reality) vs. String Theory (alternate reality): Traditional particle physics views the fundamental particles (electrons, etc.) as tiny little billiard balls or for the sake of making the mathematics easier, point (zero-dimensional) particles. If all particles actually were zero-dimensional, then you too would be dimensionless since you are composed of those point particles, and zero plus zero plus zero (plus billions more zeros) ultimately equal zero. String Theory on the other hand replaces little billiard balls (or point particles) with stringy bits that vibrate. The rate of those vibrations, determine what kind of fundamental particle it is; and the particle can be either a closed string (like a doughnut or rubber band) or an open, cut string – one with two separate and apart ends. String Theory however represents alternative reality because 1) after three decades of theoretical speculation it remains just theoretical speculation – nothing experimentally confirmed, and 2) String Theory proper requires a minimum of nine spatial dimensions in order for the mathematics to maintain logical consistency.

4) Three Spatial Dimensions (reality) vs. Four [or more] Spatial Dimensions (alternate reality): You have absolutely no doubt in your mind that you wander through the weird and lurid landscape of three dimensional space. You can go back and forth; up and down; and left and right. You couldn’t exist is less than three dimensional space. You could probably exist in a four dimensional space, or five or six, even seven, eight or nine dimensions. That’s the alternative reality claim of theoretical physicists who adopt a String Theory worldview. However, in your day-in-and-day-out battle against the elements and the powers-that-be, one battle you don’t encounter is negotiating and wandering through a maze of additional spatial dimensions. If they exist, and that’s a big if, they are irrelevant to you, and you probably could therefore care less. But if for all practical purposes they are irrelevant to you, and String Theory physicists can’t provide any evidence, far less proof for their existence in any event, then for all practical purposes they don’t exist. Till they do, this alternative reality is kaput.  

5) General Relativity Space-Time Gravity (reality) vs. Quantum Gravity (alternate reality): Gravity; it’s what holds you firmly to Terra Firma. If I ask you what holds you firmly to Terra Firma you’d answer “gravity”. But if then asked to explain exactly what it is and how it works you’d be stumped. The Newtonian equation of gravity makes predictions but doesn’t give explanations.

However, there are two explanations for gravity if I read the textbooks correctly. One is wrapped up in the General Theory of Relativity whereby gravity is a continuous force operating throughout space-time; the second is non-continuous gravity in the realm of the quantum.

* Gravity is just the geometry of space-time: Mass ‘tells’ space-time how to warp, and warped space-time ‘tells’ mass how to move – seemingly experimentally verified more than several times over. The movement of mass in warped space-time is what we interpret as the ‘force of gravity’, but gravity is actually the actions of mass moving in space-time geometry. If gravity is just a continuous geometry and mass deviates from the straight and narrow path because lots of other mass has warped space-time from the flatland Great Plains to the peaks and valleys of the space-time Rockies, then there’s no apparent need or reason that I can see to unify gravity with the other forces and their particles. There is no graviton. If there is no causality link with the other three (quantum level) forces, there’s no need for a Theory of Everything (TOE). There’s no need to reconcile the 98 pound of weakling gravity with the Atlas physiques of electromagnetism, etc. 

* Gravity is just another force: Secondly, there are in this worldview four fundamental forces: the electromagnetic force, the strong and weak nuclear forces, and gravity. Forces have accompanying elementary particles witch convey the force. In the case of the electromagnetic force, the particle is the photon. The particle associated with gravity has been dubbed the graviton. Unfortunately, it has never (to date) been detected. Now the central issue here is trying as they might, physicists cannot unify the four forces into one whole, called that Theory of Everything or TOE. Since everything should be related to everything else, gravity should be, if not a brother or sister to the other three force-related siblings, at least a kissing cousin. Alas, it’s an unrelated hermit that wants no ancestry with the other three. If however gravity should be shown to be a non-continuous force, that is there is this unit of gravity, and that unit of gravity, but nothing in-between, or in other words, you can’t divide a graviton in half – it’s as fundamental as the electron or the gluon or the photon – then gravity will join the world of the quantum. But that happy marriage date has not yet been set, and maybe never will be.

To be continued…

It’s About Time – For a Change: Part Two

Introduction: The real nature of what we call ‘time’ is one of the Big Questions. It’s been debated ever since humans evolved thought and language. That puzzlement remains true to the average person today, although ‘time’ has become the professional subject or province of philosophers, metaphysicists, and theoretical physicists, not to forget many a science fiction author! Here’s my two cents worth – ‘time’ is an illusion!

Continued from yesterday’s blog…

Travel through Time? The question remains despite my earlier negation; can you revisit and experience a past event? Can there be an instant (or not so instant) replay? Take the example of the now dispersed ink in the bowl of water. If all the ink bits (particles) were to exactly retrace their movements (that’s just so highly improbable that you’d wait longer than the age of our Universe to actually see it), they would eventually come together as an ink drop. If they now retrace those retraced movements (ditto on the statistical improbability) you get back to the exact same configuration of dispersed ink bits in the bowl of water. You will have witnessed an instant (or not so instant) replay of a past event. You would have in a sense travelled back in time to ‘record’ an event that had already happened. Of course you would have ‘time’ travelled with respect to that specific event and only that event.

Ah, that word ‘record’. Of course you could have filmed the original ink drop to dispersed ink event then watched the film at a later date, but that’s cheating a bit, don’t you think?

Assuming for a moment that time is actually something tangible and that travel through it is possible (that’s in agreement with Einstein’s General Theory of Relativity). Einstein’s Relativity aside, I’d maintain that travel backwards in time is probably nonsense.

If you go back in time with a view to either preventing something from happening or inaugurating something and you succeed, then when you return to your own present time the original motive to go back in time in the first place has ceased to exist. That’s because in your now altered present, there’s nothing motivating you to go back in time and so you don’t, but if you don’t then you couldn’t have changed the past in the first place. That actually suggests that your actions have split the Universe and generated two timelines (or universes), one in which you go back to fix something, and one in which you don’t because there’s nothing that needs fixing.

If you don’t succeed, if you can’t tamper with the past* then it’s all an exercise in futility and so there’s no point being a damn fool about it. If at first you don’t succeed, give up!

If you go back in time just to observe (as historian, scientist or even tourist), your very presence in the past has introduced a change that didn’t previously exist, and any change has a ripple effect which will change, even if only slightly, your own present, in you’re your before-the-fact time travelling present was different to your after-the-fact time travelling present, which could, as we’ll see, generate a paradox. You may not care about the alteration, but other people may not be so happy and laid back with your inadvertent meddling.

But wait a second. Those other people probably wouldn’t know or be aware that anything had altered. Having reset the clock when you went back in time, the ripples would have become part and parcel of their world view, so only you, upon your return (having bypassed all the rippling) would notice the change.

But what if you go back in time only to materialize in front of a speeding train and are killed. Of course that doesn’t affect your ancestors so presumably they still meet and marry and breed and ultimately your born – again – only to go back in time and get hit by that train!  

Or, you materialize back in time and so startling someone of that era into failing to notice that train and gets killed. Now say that someone was your father-to-be; your father before he met your mother. Now you have two universes – timelines – again. One timeline is where you went back in time and presumably returned; one in which you were never born.

That’s one of many variations on the ‘grandfather paradox’ which in general has as a plot where you go back in time and somehow prevent your own birth by say, killing your grandfather before he met your grandmother, or in a less gruesome way, prevented them from ever meeting. When I was a teenager I remember writing a short story (never published) where a group of scientists travelled back in time some four billion years to just after the Earth formed and solidified and cooled. One of the scientists was a pipe smoker, and after finishing his smoke, tapped out the pipe ashes into a small puddle of water. Of course that puddle was the very puddle that was to have given rise to that first proto-cell, but the pipe ash polluted the puddle and so that origin of life event never happened, and so back in what would have been the 20^th Century, the sun shone down on a sterile planet! The only trouble with the story was that four billion years ago, there was no oxygen in Earth’s atmosphere so one couldn’t smoke. Still, it was the mother of all grandfather paradoxes!   

Here’s another time travelling curve ball coming your way. You have a set of coordinates with respect to Planet Earth – latitude, longitude, and altitude. But you also have a set of coordinates with respect to the Moon – lunar latitude, longitude and altitude. You have a set of coordinates with respect to the Sun (solar latitude, longitude and altitude). Ditto Mars, and ditto the nearest star and ditto the centre of the Milky Way Galaxy, etc. In fact, although they change from moment because of relative motions of all the bodies concerned (that also applies to you and Planet Earth since you move around), you have a set of coordinates with respect to every bit of matter in the Universe. The question is, when you time travel, what set of coordinates do you take with you? Where exactly do you end up? It’s taken for granted in works of fiction that its Earth’s coordinates, but is it necessarily so? What if you retain your exact position (relative to where exactly is a mystery) but travel in time. Then presumably when you materialize else-when, the Earth will have moved far away, and there you are flailing around in empty space, breathing a deep vacuum!

So we see that while time travel stories are a staple of the sci-fi authors’ bag-of-tricks – they stir up those little grey cells – there doesn’t appear to be much chance of time travel in any physical reality we know of. Time travel is only a reality in the imagination. We in fact have a version of the Fermi Paradox here. While the Fermi Paradox referred to aliens that should be knocking on our collective doors (“where is everybody?”), if time travel were possible, as astrophysicist Stephen Hawking has so absolutely pointed out, then where are all those gawking time travelling tourists and historians from our future?

*Akin to astrophysicist Stephen Hawking’s Chronology Protection Conjecture which states that there is as yet some undiscovered principle in physics which will make it impossible to travel back in time and thus make the Universe safe for historians.

Further recommended readings about time and time travel:

Carroll, Sean; From Eternity to Here: The Quest for the Ultimate Theory of Time; Dutton, New York; 2010:

Davies, Paul; About Time: Einstein’s Unfinished Revolution; Penguin Books, London; 1995:

Gott, J. Richard; Time Travel in Einstein’s Universe: The Physical Possibilities of Travel Through Time; Phoenix, London; 2002:

Hawking, Stephen & Penrose, Roger; The Nature of Space and Time; Princeton University Press, Princeton, New Jersey; 1996:

Hawking, Stephen W. et al.; The Future of Spacetime; W.W. Norton and Company, N.Y.; 2002:

Le Poidevin, Robin; Travels in Four Dimensions: The Enigmas of Space and Time; Oxford University Press, Oxford; 2003:

Lockwood, Michael; The Labyrinth of Time: Introducing the Universe; Oxford University Press, Oxford; 2005:

Mahid, Shahn (Editor); On Space and Time; Cambridge University Press, Cambridge; 2008:

Randles, Jenny; Breaking the Time Barrier: The Race to Build the First Time Machine; Paraview Pocket Books, New York; 2005:

Toomey, David; The New Time Travelers: A Journey to the Frontiers of Physics; W.W. Norton & Company, New York; 2007:

It’s About Time – For a Change: Part One

Introduction: The real nature of what we call ‘time’ is one of the Big Questions. It’s been debated ever since humans evolved thought and language. That puzzlement remains true to the average person today, although ‘time’ has become the professional subject or province of philosophers, metaphysicists, and theoretical physicists, not to forget many a science fiction author! Here’s my two cents worth – ‘time’ is an illusion!

What Is Time? Time is, IMHO, an illusion. Time has no real independent existence – it can’t stand by itself. If you removed all the matter and energy from the Universe, would there be left anything we could address as time? Time is just our way of keeping track of, and measuring rate of change in matter and/or energy. If nothing ever changed it would be nonsense to talk about time. The flow of time; the arrow of time; is just the flow of macro things changing. If everything were somehow ‘frozen in time’ – like a single frame from a film – then there is no actual time that can be discussed or measured. So we don’t in any sense measure something that is time, we measure rate of change and call that time.

Actually you measure rate of change by another rate of change. For example, the rate of change from birth to death is usually measured by the rate of change in position of the Earth orbiting the Sun (years and fractions of years) and rate of change of position of the Earth rotating around on its axis (days and fractions of days). Another example: The rate of change between the beginning of your lunch hour and the ending of your lunch hour is usually measured by the rate of change of the hands of a clock (sixty 360 degree sweeps of the minute hand or a 30 degrees clockwise change in the hour hand) or the rate of change in the numbers on your digital watch, say from 1:00 to 2:00. Translated, a variable or uncertain rate of change (lifespan; length of a lunch ‘hour’) is usually measured by a standard, invariable, predictable rate of change.

Now rate of change is affected by gravity – a function of mass – the greater the mass the greater the gravity and the slower things change from A to B in that gravitational field, but that slowness is only relative to someone else also measuring A to B but who is in a lesser gravitational field. A clock at the top of a tall building (lesser gravity being further from Earth’s centre) ticks at a faster rate than an identical clock at street level (which has higher gravity due to being closer to Earth’s centre). Rate of change is also affected by velocity. The faster you go, the slower things change from A to B, again however it’s relative to someone else also measuring A to B but who is moving at a lower velocity relative to you. That’s why it’s the theory of relativity! The standard example is the twin paradox – if your identical twin zooms off in a spaceship at extreme velocities to the distant stars, stops, reverses direction, and returns at that high rate of speed to Planet Earth, and to you, you’ll find your twin has aged to a far lesser degree than you. You now have grey hair and wrinkles; your interstellar travelling twin is still in her youthful prime of life.

Time vs. Time Travel: I’ll poor water on this fire at the outset by stating again that time is but an illusion. Time doesn’t exist; therefore time travel isn’t possible. Time is but a label, like your own name is but a label, and has no more reality than the label ‘Wednesday’. We just arbitrarily call every 7^th ‘day’ Wednesday, but you can no more hold Wednesday in your hands and you can time. Time, repeating myself, has no independent reality. You can’t assign any physical properties to the concept. I mean time isn’t a solid, it isn’t a liquid, and it isn’t a gas. Time has no size, weight, colour, texture, density, it doesn’t vibrate or have a wavelength, ditto no odour or flavour, it has no temperature or pressure, it doesn’t consist of any known combination of known forces and/or elementary particles, it corresponds to no known element or compound. You can’t pour time into a bottle and store it; you can’t confine time in a force field or in a prison cell or trap it on a piece of sticky fly paper. Therefore, if time has no substance, one can not actually travel through time.

What we perceive as ‘time’ is, again repeating myself, nothing but change – change in our environment; in our natural world; in our mechanical devices; and even in ourselves and associated companions (animal and human). Repeat – time is but an illusion. Change is real (cause and effect) since it involves forces and particles; energy and matter, the sorts of things that when you kick them, they kick back. We measure ‘time’ by the rate things change; rate of change is what we call ‘time’. Repeat - it’s the change (in something) that is real. 

Now on the macro scale, that is scales we interact with on a day-to-day basis, change appears to all intents and purposes to go one way (usually from a state or high order to a state of disorder) and so we view time as flowing from past to present to future – in one direction; order to disorder – past to present to future. But change in just one direction (order to disorder – past to present to future) is ultimately a function of numbers and probability. The simple illustration is to introduce a drop of ink into a bowl of water. That’s a high order situation. Now left to itself, there will be a change. The ink will disperse throughout the bowl of water. That’s a state of disorder. If a disordered uniform mix of ink and water separated all by itself into a drop of pure ink and a bowl of pure water (high order), that too is change, but we would interpret or view such an event as going backwards in time. If you viewed such a happening on film, you’d immediately conclude the film was being run backwards.

There’s a far greater probability for individual ink particles to spread out throughout a large volume than to come together in a small space. There’s lots of pathways to spread out; far fewer pathways to come together. But at the micro level, the level at which those individual ink particles do their thing, they don’t care where in the bowl of water they are. They are just as ‘happy’ to be all together as a drop of ink, as dispersed and diluted. If they do come together as a drop of ink from a dispersed/diluted state, that’s statistically unlikely, but such an event violates no laws of physics. It would be going from a state of maximum disorder to a highly ordered state; or, from an apparent future to present to past ordering. Such a change would appear for all practical purposes as apparent time travel – going backwards in time.

The catch – there’s always a catch – is while all those ink particles are defying statistical probability and undergoing apparent time-reversal, the rest of the cosmos is acting in a statistically normal way – going forward in ‘time’. So, perhaps we have a Universe where for 99.9999% of the time, 99.9999% of events within the Universe march to the beat of the standard past – present – future ordering of things. That is, in terms of change happening in a statistically probable way. While now and again tiny pockets of the Universe reverse direction, they do so at least just temporarily.  One can only defy statistically probability for only so long. So the ink particles come back together again as a drop of ink within a bowl of water – then what? They no doubt reverse direction again and proceed normally.

An analogy might be that while some individuals are winners while playing the slot machines (high order), the club still rakes in the profits from the vastly greater majority of (disordered) losers, and that no doubt the few highly ordered winners will eventually descend into a state of disorder and contribute ultimately to the club’s profit margin! It’s more statistically likely for a winner to become a loser than for a loser to become a winner.

Consider electrons. On average, any given electron has a very high probability of participating in a changing set of circumstances consistent with statistically probability. That is, the electron is moving forward in ‘time’. But if in those rare (loser to winner) occasions the changing set of circumstances goes against the grain of statistically probability, then we would view that electron as moving backwards in ‘time’. But there ultimately is no backwards or forwards in time, just change which statistically goes or moves in one general direction (order to disorder), but which can now and again, albeit briefly, go the reverse direction (disorder to order).

To belabour the point, what we call the past is change which has already happened; the present is change which is happening; the future is change that will happen.

To be continued…

A Unified Theory of Time Travel: Part Two

The work of Albert Einstein and the ideas of Stephen Hawking differ when it comes to the even theoretical possibilities of time travel to the past. However, both points of view can be accommodated by invoking the concept of parallel worlds. It’s a case then of having your time travel cake and eating it too but without fear of creating a paradox tummy ache.  

Continued from yesterday’s blog…

What’s to prevent those from a parallel universe meddling and altering our time stream? It’s not enough for them to have a Prime Directive against that – we all know Prime Directives are meant to be broken! So, it looks like Hawking’s Chronology Protection Conjecture must apply to those visitors from parallel universes to our Universe as well. I mean what difference does it make to your existence whether you travel back in time within your own universe and kill your mother before you were conceived, or some serial killer escaping from a parallel universe to our Universe who kills your mother before you were conceived – even though in the latter case there’s no paradox, you still wouldn’t have been conceived of here in anyone’s philosophy!

OK, so relativity allows time travel back in time, but only to parallel universes. The Hawking Chronology Protection Conjecture not only prevents time travel paradoxes in general, but it also prevents parallel universe time travellers meddling and altering our timeline; ditto we humans time travelling to someone else’s parallel universe. But how would the Hawking Chronology Protection Conjecture actually accomplish this? My best guess is that parallel universes aren’t in phase – they aren’t polarized or synchronized in-phase like a laser beam, or the light that passes through your polarized sunglasses – otherwise we’d have some rather hard evidence of them; certainly way more than we do now.

So, if we go to parallel universe B or those from parallel universe B visits us, we’ll, or they’d be respectively out of phase with respect to the universe they are now in. Translated, they, or we, could look, but not touch for all practical purposes. I say for all practical purposes as now and again what’s out of phase (high probability – the usual state of affairs) will sync into phase (that’s rare). But the in-phase times are so few and far between, and last for such a brief duration that it’s unlikely to result in any inadvertent or deliberate timeline alterations. That’s my rendering of the Hawking Chronology Protection Conjecture – he could well have other ways and means in mind.

So another way of putting this is that time travellers would be spectral or ghostlike in their host universe, and maybe that’s where our traditions of ghosts and other things that go bump in the night come from! This is much like the parallel universe ghost or shadow photons that are conjectured to explain some highly mysterious aspects or phenomena contained within the famous quantum double slit* experiment. Now an obvious question is how do all the parallel universe ghost photons get into our physics labs where double slit experiments are carried out? I mean there are no local macro Black Hole or wormhole exits present – are there? Yes in fact there are! Not a macro wormhole, but a micro wormhole – actually wormholes. Theoretically, micro wormholes should exist all around you. It’s just that they are at quantum levels – incredible tiny; way subatomic in size. And they exist for just nanoseconds before collapsing.  They are just part of the quantum foam** reality at super microscopic levels, a reality at the level where all things exhibit the quantum jitters or quantum fluctuations. Thus, every second of every day, everywhere, there are little quantum gateways – quantum sized wormholes connections between universes which quantum sized particles – like photons – can traverse! From the standpoint of the double slit experiment, it doesn’t matter whether the parallel universe’s ghost photons came from the past, future or present – just as long as they are, indeed, present!

Now you may think it would be easy to detect these ghostly photons. Just put a photon detector in a totally dark and sealed room. Well, not quite so easy. Some photons can pass through ‘solid’ matter. X-Ray photons anyone? Radio wave photons pass through the walls of your home. If you look at a bright light, you’ll still see light even if you close your eyes. So, your photon detector in your dark and sealed room could easily detect our local variety.

The ghostly bits aside, parallel universe time travelers (or even ordinary time travelers from within our Universe assuming Hawking is wrong)) might explain the sometimes uncanny, often incredible look-a-likes that we all seem to have. A long shot to be sure, but something interesting to ponder.

There’s still one more problem on the horizon. Just because a macro Black Hole or wormhole plunks you into a parallel universe (and of course you’ve got to be able to survive the trip itself which might be problematical), doesn’t mean you’re going to be with spitting distance of your ultimate destination(s) – say a parallel Earth(s). So, time travelers might also need more conventional transport – like Flying Saucers (okay, forget the saucers – like spaceships with fins and rocket motors). But then what’s really there to distinguish a visiting time traveler from a parallel universe from say a  run-of-the-mill extraterrestrial from within our own Universe? Maybe you could just put out the welcome mat for both options!

One final thought. Could there be a Clayton’s time travel? - Time travel without traveling in time? At the risk of making Einstein turn over in his grave; I’m going to propose a universal NOW across all universes. Now I know that NOW, when it comes to observers, is a relative thing. An observer in Martian orbit sees Mars’ NOW somewhat before you on Planet Earth sees the same Mars’ NOW because the speed of light is finite. And relative motions and velocities complicate what is NOW. But, I propose (a thought experiment remember) to instantaneously freeze-frame the entire collection of universes’ NOW. Everyone and everything everywhere comes to an instant standstill. Right! We now have a universal NOW that we can study at our leisure (the freeze doesn’t apply to you and me – we’re outside the space-time continuum).

Let’s focus on that subset of all parallel universes – all parallel Earths and time travel between them. Now there’s no reason to assume that all parallel Earths are identical in all aspects. Indeed, some parallel universes may not even contain a parallel Earth! There maybe some parallel Earths identical or so close to identical to our Planet Earth as makes no odds – abodes you’d feel right at home in. Other Earths would differ in various ways, some minor, some major. Still others might be really weird and alien, as in having evolved a dinosaur society, civilization and technology. There was no parallel asteroid impact 65 million years ago; thus no human beings around the traps 65 millions later.

Your subset of parallel Earths would show near infinite diversity in infinite combinations. I say ‘near’ because you can only stretch the term ‘Earth’ or ‘Earth-like’ so far and no farther, before it’s not Earth or Earth-like. A 100% oceanic world is not Earth. If a parallel ‘Earth’ has Venus-like temperatures, it is not Earth-like. If it has a density approaching that of a neutron star, it is not Earth-like. If it has no life on it, even though in all other respects it is a near carbon copy of our Earth, it is not Earth-like. 

Now it’s back to the NOW subset of parallel Earths and Earth-like abodes. There’s no reason to assume that evolutionary development; that evolutionary development rates would proceed in each and every case in an identical fashion. Some parallel Earths would still be in the dinosaur era (if they had dinosaurs of course). In some parallel Earths, cavemen and sabre tooth tigers rule. In others, it’s Biblical times, or Medieval times or the era when Britannia ruled the waves. Others in our absolute NOW, on yet other parallel Earths, or parallel earthlings, might have just invented the wireless or landed on their Moon (if they have one). On some parallel Earths it may already be what to us will be the 23^rd or 24^th Century with interstellar warp drive capabilities at hand – and even way beyond that. So, you could seemingly travel to the past and future while actually remaining in our NOW. You’ve travelled in time without really travelling in time, or, time travel without the paradoxes – but maybe that spoils all the intellectual fun of contemplating time travel in the first place!

*The problem solved here is how can you get a classic wave interference pattern behind two slits you fire photons through; even when you fire the photons at say a rate of one per hour? Who you gonna call – ghost photons of course to the rescue.

**Quantum foam – the world may look pretty smooth from a distance, but as you keep magnifying the finer details, the micro world gets ever so slightly bumpier. Close in some more and things get rougher still, until at quantum level everything is a seething cauldron of tumultuous activity. It’s like the sea that looks perfectly smooth and tranquil from Earth orbit, but at rowboat level, you’re terrified as that 50 foot wave comes crashing down on you.

Further recommended readings about time travel:

Gott, J. Richard; Time Travel in Einstein’s Universe: The Physical Possibilities of Travel Through Time; Phoenix, London; 2002:

Hawking, Stephen W. et al.; The Future of Spacetime; W.W. Norton and Company, N.Y.; 2002:

Randles, Jenny; Breaking the Time Barrier: The Race to Build the First Time Machine; Paraview Pocket Books, New York; 2005:

Toomey, David; The New Time Travelers: A Journey to the Frontiers of Physics; W.W. Norton & Company, New York; 2007:

A Unified Theory of Time Travel: Part One

The work of Albert Einstein and the ideas of Stephen Hawking differ when it comes to the even theoretical possibilities of time travel to the past. However, both points of view can be accommodated by invoking the concept of parallel worlds. It’s a case then of having your time travel cake and eating it too but without fear of creating a paradox tummy ache.  

Albert Einstein’s theory of general relativity suggests that time travel to the past is possible via rotating wormholes and/or black holes.  The actual technical practicality of actually carrying out such journeys need not concern us since this essay is in the realm of the thought experiment.  Now Stephen Hawking says time travel to the past is not possible because he proposes that there is such a thing as a yet undiscovered Chronology Protection Conjecture that prevents this and thus makes the world safe for historians. I’ve come up with a unified theory of time travel into the past that incorporates Einstein’s general theory of relativity; Hawking’s Chronology Protection Conjecture, along with other assorted bits like parallel universes that are thrown into the mix.

Time travel is a staple in sci-fi stories, novels, films and TV series. And, time travel is possible – in theory. We all know about journeying to the future which we do at the rate of one second per second whether we like it or not.  Apart from that, if one travels at close to light speeds relative to your  place of origin then you can travel to the distant future (with respect to that place of origin) without aging an equivalent number of years (the twin paradox). Travel to the past is apparently allowed too, via the weird physics inherent in rotating worm holes and maybe Black Holes which is where Einstein’s general theory of relativity comes into play.  The problem there is that relativity theory predicts worm holes, if they exist at all, will exist for nanoseconds and be very tiny to boot, and thus not very useful in the foreseeable future for the purposes of time travel. Because we don’t know exactly what the inside of a Black Hole is, and where it leads, if anywhere, current thinking suggests that jumping into Black Holes are a more useful means for committing suicide than for travelling to the past, but the jury is still out on that one.

Anyway, the fun bit about time travel is the various paradoxes that arise, the most famous one being the grandfather paradox. That is, what if you travel back in time and kill your grandfather before he sired your father (or mother). If you did that it means that you could never have been born, but if you were never born you couldn’t go back in time to kill your ancestor. This is the sort of stuff sci-fi authors (and philosophers) love – ditto physicists! My favourite time travel paradox however is the one where you get something for nothing. Say you have this edition of “Hamlet”, and you want Shakespeare to autograph it. So back you go in time to Shakespeare’s era. You knock on his door, but the housekeeper says he’s out for the day but if you leave the book he’ll autograph it and you can come by and collect it next morning. When Shakespeare comes home, he sees the book, reads it, and is so impressed he spends the night making a copy. You come back the next morning, collect your now autographed edition of “Hamlet”, and return to the present day with your now very valuable book.  The question now becomes, where did the original “Hamlet” come from? You didn’t write it; but Shakespeare didn’t either as he plagiarized your copy which he then passed it off as his own work.

Another favourite is you meeting yourself. Say you’re 50 and not all that well off. You get the brilliant idea to travel back in time and convince your younger self to invest in some stocks you know will pay off big time later on down the track. And so it comes to pass that your younger self so invests, and becomes filthy rich, only, in leading such a high life, dies of a heart attack at the age of 45! Or you always regretted not proposing to the love of your life when you were young, and thus go back and convince your younger self to muster up the courage and do so. He does, but as they fly off on their honeymoon, the plane crashes with no survivors. Sometimes you don’t know when you’re well off.

Or if you can travel back in time, then of course others can to. Naturally there’s going to be lots of people interested in particular events, maybe even at the time, seemingly trivial events (yet which turn out in the long run to have had major impact(s)). And so you might have any number of people going back to particular historical focal points, each with their own particular agenda (most of which will be mutually exclusive), and ultimately causing havoc. I mean if person one goes back and influences an event producing a new outcome, then person two might go back and has a go at that result and things get altered again, which will then prompt person three to go back and influence things more to his liking, etc. In other words, history would never be fixed, rather always be fluid. The world is not safe for historians. Since we believe that history (or the past) is fixed, then that what’s written on your history book page today will not alter overnight. Thus, you have probably concluded that time travel cannot happen, will not happen, and has not happened, however much you yourself might wish to go back in time yourself and change something. (Don’t we all really wish some past something, personal and trivial, or perhaps something of major significance could be changed and you’d be that instrument of change?)

Its paradoxes and situations such as the above that prompted Stephen Hawking to postulate that there is as yet an undiscovered law or principle of physics which prohibits time travel to the past – he calls it his ‘Chronology Projection Conjecture’. Since we have never seen, according to Hawking, to the best of our knowledge at least, any time travellers – tourists or historians - from our future, he’s probably right.

So, putting it all together, here’s my theory of time travel: my unified theory of time travel, at least to the past.

Relativity theory has passed every experimental test thrown at it, so the theory isn’t in much doubt and one can have a high degree of confidence in what it predicts, even if that prediction is currently beyond any experimental test. Relativity theory allows for time travel into the past, but, IMHO, only to parallel universes (otherwise known as alternative or mirror or shadow universes) where no paradoxes can happen.

Why only parallel universes? The ways and means by which you can use relativity theory to time travel backwards involves rotating Black Holes or wormholes. There are serious reasons behind the speculation that what’s on the other side of a Black Hole and/or wormhole is another universe. So, therefore it’s relativity’s time travel allowance, but probably to another universe. The Black Hole or wormhole ‘exit’ isn’t within our Universe.

Whatever you do in that parallel universe is predetermined. It’s fate. It’s destiny - all because causality rules. Therefore, there are no unexpected ripple effects other than what was destined to happen. You were meant to be there and do what you do. Therefore, there will be no paradoxes arising.

Astrophysicist Stephen Hawking has proposed his Chronology Protection Conjecture that prohibits time travel to the past within your own universe because of the possible paradoxes that could arise. Why can’t you go back in time in your own universe? That would mean that at a specific time and place you both were not (originally) and were (as a result of going back) present. That’s a paradox. And if you were to travel back in time to a set of time and space coordinates you were actually originally at, then there would be two copies of you occupying the same space at the same time – also a paradox.

But take the grandfather paradox. If you go back in time and kill your grandfather, but your grandfather in a parallel universe, then you don’t prevent your existence, just the eventual existence of yourself, your other self, in that parallel universe.  In the case of Shakespeare and “Hamlet”, you gave your copy to a parallel universe Shakespeare. In your original (our) Universe, Shakespeare is still the legitimate author. 

Once you time travel from your universe A, to parallel universe B, you can’t return again to universe A because of Hawking’s Chronology Protection Conjecture – paradoxes could arise. However, you could go from parallel universe B to parallel universe C, but, hence never return to either universe A or B – Hawking’s Chronology Protection Conjecture again.

Perhaps some people you’ve seen or known or heard about might be time travelers from a parallel universe’s future. If they then time travel to another parallel universe, then that might account for some missing persons’ cases!

In short, we can time travel to other parallel universes but not to our own; entities from other parallel universes can visit our Universe. No paradoxes need arise. Both Einstein (relativity) and Hawking (Chronology Protection Conjecture) are satisfied and happy campers. 

Is that right? No, it’s wrong! There’s still one very nasty loose end here.

To be continued…