# Does the present really exist?

Firstly a warm welcome to all new followers; we were fortunate enough to be featured on WordPress Discover recently which gave a wonderful flurry of new support. We endeavour to stay in touch and interact with as many of you as possible; and hope that science and mathematics continues to be an area of interest for everyone. The pool of human knowledge is after-all our most valuable asset, which we share collectively.

Now for our second exploration of time (if you missed the first you can find it here). The theory of relativity is our best theory of the macroscopic world. The theory of Special Relativity was introduced by Einstein in 1905 brought about a wide range of insights into the nature of reality including length contraction, time dilation, a universal speed limit of the speed of light and the relativity of simultaneity. It is the latter that shall interest us today.

Recall the familiar light beam on a train thought experiment? If not you can see a detailed explanation of it here. In brief; a beam flight is emitted from a bulb placed in the middle of the carriage on board a train – which is moving with a steady speed away from the platform. Due to the fixed, universal speed of light the observer on board the train will see the flashes of light hit the back and front of the carriage at the same time. This is because he is in the same reference frame as the train – relative to the observer on board, the train is stationary. However the observer watching from the platform will see light hit the back of the carriage before the front – as the light has (according to the observer on the platform) less distance to travel to reach the back of the carriage because the back of the carriage is also moving forwards in the direction of the bulb from his perspective. This is the relativity of simultaneity, the event ‘the light beam hits the back of the carriage’ occurs simultaneous with different things for the different observers. In a moment the on-board observer calls ‘now’ the beam hits the back and front simultaneously. In a moment the off-board observer calls ‘now’ the beam just hits the back. Now in our ordinary perspective of the universe and time there is a common, universal ‘now’ which we see as a cosmic wide present moment and during which we all agree on what is happening in that instant. Special relativity throws this intuitive notion out the window. What is happening ‘now’ becomes a judgement call made by an observer depending on their position and velocity in the universe. Believe it or not this is what special relativity is telling us about the nature of time – and seeing as it’s our best theory of the macroscopic world – we should take its implications seriously.

View point of the light beam from observer on board

View point of the light beam from observer on the platform

Now the reason we don’t have such disagreements about what’s happening ‘now’ with our neighbours is because such effects only cause discrepancies with signals of very high speed i.e. the light beam or on extremely large distances – we’re talking intergalactic. So sadly you can’t put down your lateness to meeting a friend as a consequence of the differing idea of ‘now’ (though this would be the best excuse i’d ever heard).  Here is the famous Andromeda Paradox by mathematician Roger Penrose that extends this phenomena to the judgement of events very far away. The argument uses the tool of the Spacetime diagram as an aid but I will try and explain it without a such a concept in this post.

There are two people walking past each other in the street. One is walking in the direction of the Andromeda galaxy, and the other is walking away. Now the technical terminology for what comprises now for a certain observer is the set of events that lie on their ‘plane of simultaneity.’ A plane of simultaneity is in essence the collection of events that comprise the three-dimensional universe for that particular observer, in their experience of the present moment. For example I am sitting here in my room typing this, I see the curtain blowing in the wind, the noise of the birds, a shooting star crossing the night sky – all these events lie on my plane of simultaneity. However, for other observers moving at different velocities to me our planes of simultaneity differ slightly. The velocities are not big enough to cause an difference over what we regard as happening ‘now’ in the local vicinity but if you extrapolate these planes far far out, out to intergalactic distances the slightest movement left or right can cause the observer’s three-dimensional universe to have differing content. This is all part of the big idea of spacetime. (A post of spacetime and spacetime diagrams coming soon) Back to the paradox – so for the observer walking towards the galaxy the events in occurring in Andromeda on their plane of simultaneity may be hours or days or weeks in advance of that for the observer walking away. If on Andromeda they are planning an invasion on Earth, for the observer walking away they may still be planing but for the observer walking towards they may already have left!

Now I know you must be thinking but these observers can’t possible receive signals from such inter-galactic distances or ‘see’ what’s going on in the first place to have the evidence to compare. But this is the beauty of thought experiments and the basis of theoretical physics. This is what the theory tells us about the nature of time when extrapolated to boundaries beyond the ability of our tiny human probes, and seeing as this theory has been stood the test of all our experiments so far we should take its wider consequences seriously.

The fundamental axiom of Special Relativity is that no reference frame is preferable over any other. As such no observer has the right to claim his experienced present moment is the ‘real’ now. Therefore if there is no distinguished, cosmic, fundamental ‘now’ we can no longer clearly divide events into past and future, using the now as the unambiguous barrier. Time and its once rigid tenses begin to disintegrate and crumble beneath us. The once solid passage of time and the idea of a cosmic now moving ever forwards and clearly bringing future events to present and present events to past is no more. Each observer has their own set of present events that they consider to be make up the three-dimensional universe. But each is different and thus with these multiple different three-dimensional universe we reach the conclusion that the universe is four-dimensional. Now four dimensions are very hard to imagine or visualise so for the sake of our human brains imagine the analogy but with one dimension less. The universes of the observers are like different two-dimensional slices or cross sections through a three-dimensional block or cube.

The four dimensions of this block are the three of space and the one of time and within this four-dimensional block universe are all the events that ever existed, exist or will exist. The block universe theory states all events from the birth to the death of the universe and everything in between ‘pre-exist’ in the block. There is now cosmic now but only a present plane of simultaneity from the perspective of observers who float through the block. All events behind the floating observer are regarding as past from them, all ahead as future and as the observer floats through his life he cuts slices through the block, parallel to his trajectory which represent his present set of affairs.

So there we have it, the nature of time according to Special Relativity and the four-dimensional block universe theory. No fundamental passage of time, no cosmic-wide now just perspectives of three-dimensional beings in a four-dimensional block. If that doesn’t blow your mind, I don’t know what would. Although, the theory does give me some weird sort of comfort and it seems to have done for  Einstein as well as he said to his friend after the death of her husband “now he has departed from this strange world a little ahead of me. That signifies nothing. For those of us who believe in physics, the distinction between past, present and future is only a stubbornly persistent illusion.”

I hope I managed to convey this theory and it’s consequences with some clarity – confusion around such a counter-intuitive subject is of course to be expected. There are however theories that try to salvage the fundamental passage of time and universal present moment even in light of the theory of Special Relativity… In fact I wrote my thesis on this topic with the conclusions the present moment does after all exist!  I’ll let you in on my thoughts on that reassuring idea in the future.

## 92 responses to “Does the present really exist?”

1. There’s no such thing as ‘the present’ as events keep moving into the future, and the future keeps coming into the present, but for a fleeting second before shifting into the past – hope things are quite clear now in the present! 😉

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• Indeed this is a troubling thought and thank you for bringing it up! – how can the present have a finite duration surely it must be instantaneous as otherwise part of it is always in the future or past? Sadly this is a slightly different question and this argument assumes an instantaneous present moment does exist, but observers disagree as to what three-dimensional state of affairs it constitutes due to their relative movements in the universe! Thank you so much for stopping by 🙂

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• You’re welcome! BTW, the present, past or future are moments that exist in a relative sense only, for living beings, as everything pertains to time which keeps flowing in a linear sequence marking events occurring in an irreversible succession. However, ‘the present’ moment does exist fleetingly bridging
the future and past moments in time – got to stop here for want of time in the present! 😉

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2. Love your post. Keep it up.

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3. there are many mysteries in this universe.. i think “now” is such an illusion as i mentioned in my post “https://wordsandnotion.wordpress.com/2016/10/05/is-now-is-an-illusion/”

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• I have read your post and indeed! Very topical with this one. Certainly an issue where if you thought on it for too long you would go entirely mad

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• ya… mentally mad.. not so far appeared to be in the eyes of others..;)

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4. What is time?
Could you please elaborate upon the distinction between past,present and future during the particle interactions, say the tree level electron-electron repulsive interaction? The processes are time reversible. Future and past do not make sense then. Do they?

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• Forgive me if I do not understand your question properly. Just because these particle interactions are reversible does not, in my mind, mean they refute the existence of time or the tenses. An event (be it a particle interaction) still always has a cause and the cause always comes before the effect regardless of which reference frame the observer is in – the order of the interactions remain the same but the moment an observer experiences a certain step of the interaction may not be the same as an observer travelling with a different relative velocity. In a nutshell the argument holds that the distinction of past, present and future still exist but, as everything in relativity, their perception is relative to the observer. If I didn’t answer what you meant to ask please let me know!

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• You did in a way answer something. I was just trying to dig deeper into the nature of time itself because Thermodynamic definition of time is entropy driven and relativistic notion of time is velocity dependent. The time reversal symmetry in particle interaction in my question was that if u apply a time reversal operator on an interaction the Feynman diagram would reflect the same process going in the past apparently, without violating the micro-causality ofcourse. The momenta will be all reversed in sign. Does the time envisaged as a linear flow hold at all the levels of physical existence?

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5. Your use of the block finally made time understandable to me. Thank you.

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• Thank you for reading! Very happy to have helped

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6. Congratulations on the Discovery Mekhi, happy that WP has such a system as it connected me and others to your great site. Time is such a mysterious concept for me, I remember being amazed at the idea of differences in time between those who live on a mountain versus at sea level (and as long as I’m going there, the age difference between my feet and head). The idea that we all have some sort of gravity/time distortion is cool. Reading your words, so fluid in explaining such a topic was fantastic, and again makes me wonder of the distinction between past, present and future. The perception of time I wrote about a few months ago is the other tie-in that makes me wonder if our brains need to present an illusion for us in order to function properly in this world.

Also, you make a good argument for going for a run, as it will keep us young…correct?!? Cheers to a great weekend ahead!

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• Thank you for this wonderful comment! Indeed this is true it seems like you’re very well acquainted with the notion of time dilation close to gravitational masses – I’ll have to write a post on this to bring those who aren’t up to speed soon. Thank again for your very kind words. I’ll make sure to check out your post. I completely agree – perhaps time is nothing fundamental at all and just a mental construct that we create in order to aid our perception of the world, sort of like an underlying fabric upon which we can order events and make sense of our consciousness. Haha yes – get out for a run, move that little bit quicker through spacetime and your fraction of the speed of light will be greater through space and less through time – (by a negligible amount but still) “younger” through time dilation and an increased age expectancy through fitness – win win! Have a great weekend too

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• Acquainted as much as a non-theoretical physicist could be perhaps 🙂 Would love to see you post on this! I do think time is as you mention, just out there and our brains construction something to make sense of it…at least the idea sure is cool. Off for a run 🙂

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• Time: ‘our brain’s construction’? Am sure that’s part of its reality because I’ve often noticed our bathroom clock’s speed can vary in the morning! After breakfast I’m ready to motor into the day and see my subsequent habitual bathroom routine can be done in less or longer period than previously. Maybe others have noticed their time can run at different rates than anticipated?

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7. Very nice post!! You have got a knack of explaining complex things in very simple ways! Keep it up.

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• Thank you so very much, comments like these are the best compliments I could hope to achieve with my writing!

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8. It’s always comforting, being neither physicist nor “working student of”, that whenever I read your and Joe’s posts I manage to grasp a little more of the subject – for instance, The Block illustration above.

Thanks, as always, for a marvelous post.

Pearl

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• Thank you Pearl for your continued support and kind words!

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9. Thanks Mekhi for one of your best posts. Your para beginning ‘The fundamental axiom…’ may be so not only scientifically but spiritually too. There’s an intriguing possibility that the concept of planes of simultaneity may explain how biblical and contemporary prophecies and predictions can exist and are perceived. So we don’t need to consider galactic frames of reference alone but those immediately to hand on earth. Thus we can get a handle on the prophetic, especially when fulfilled (eg 2008 & 2013 re economy and politics).

After all, as Jesus Christ is Lord of Lords, the Alpha and the Omega – Beginning and End and beyond Time, then he’s the real Time Lord (not Dr Who!). I thus regard him as ‘The Always Now’ – and as ‘now’ constantly exists, then ‘always’ may somehow be equated to ‘now’ or just simply ‘now = always’ (dependant upon frame of reference)?

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10. Time is linear? Imho, we need to recall it has cyclical connotations and applications based upon moon’s and earth’s orbits, especially in field of economics. There, I noted one leading analyst used a similar simile that I’d blogged of time being like a turning corkscrew, or spiral. Perhaps this cyclical feature is related to the curvature of space-time?

Soon after launching a blog five years ago my focus upon Christian prophecies included data on those findings and so I introduced my readers to occasional items on time, cycles, quantum theory and their relevance to Christian beliefs. So your and Joe’s blog is a valuable resource and I plan to recommend and re-blog to my readers as soon as practicably possible.

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• Yes good point Richard – time does have many cyclical connotations and if time is in fact nothing more than a human construction, its nature is inherently tied to the way we use it. Thank you for your support!

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• Ace point, thanks Mekhi. Am posting recommendation and will follow with reblogs soon. You may like to consider that brief covering post via its pingback?

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• I shall do thank you very much as always Richard!

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11. Wow! I am impressed! I have thought some of this myself, but not with so many words! 😄

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12. Answering a question like this is really laudable…. Ossum!!

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• Thank you very much!

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• Thank you!

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13. To claim the present does not exist is most peculiar since the present is all I ever sense. If time is a dimension and we move through it then the present is equivalent to here in spacial dimensions, If you move in space then here is where you are and it surely exists although it is different from anyone else’s here. The same with the present in time.

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• What is being refuted to exist is the idea of a universal present, or ‘cosmic now’ – a present moment that all observers agree upon, as is thought to exist in the conventional, and humanly intuitive, idea of time!

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• Then what you deny is that there is no future to go to. Which, perhaps, indicates that the present generates the past out of nothingness, somewhat like toothpaste coming out of a the end of a toothpaste tube that isn’t there. I find that interesting, but rather odd. Something like the continuous generation of all the mass from nothing. A rather weird kind of a big bang without the bang.

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• Not quite – the block universe theory states that all events in time pre-exist so from this higher perspective yes there is no distinction of events into past, present, future. However from the point of view of observers moving through the block, they perceive their plane of simultaneity to represent the present and from their perspective, events can be divided into past and future – their future events move into their plane of simultaneity (their present) and then pass into their past. But the theory states that there is no universal distinction of past, present and future events – everything is relative!

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• In other words the future does exist but the plane of the present is not flat but passes through the different observer’s consciousnesses at different points in the space-time continuum. But that plane is continuous because in traveling through space one moves on that surface of both space and time.

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• On second thought, that surface which is the present traveling into the future is not necessarily continuous since as you approach the speed of light in traveling through space the shape of the present surface changes and is responsive to velocity. This makes the present quite a complex affair.

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• Extremely complex indeed! But at least we’re being brave enough to think about it!

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14. I haven’t read the Comments yet, so can speak uninfluenced by them.

To my own unlettered worldview, all exists simultaneously (ouch) and we define our existence by our present moments (being where we ‘currently’ are on the timeline). Being limited to our basic four dimensions we are unable to see the ‘future’. It suits us, but makes a mockery of any concepts of the religious Free Will. How can anyone possibly ‘choose’ to do the inevitable, or any would-be alternative?

The best anyone might offer is ‘alternate universes’ which would have to mean an infinite number of different universes being created every moment—a bit unbelievable at best.

And now to read the comments …

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• You’re very right to bring up the point of free will in this context! Indeed the block universe does bring up very many challenges against the notion -as if all events do ‘pre-exist’ then surely we are just following an already fixed timeline where all our decisions have already been made. I’ll have to do another post on these implications when i’ve had the chance to think about them more – free will is a great philosophical topic. Your interpretation of alternate universes representing free will in a sense is also very interesting and I had never thought of this angle before! Thank you very much for your comments!

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15. Have read comments. Some good thoughts, interesting ideas … and I wondered how long it would be before “the Lord Jesus Christ” made an appearance.

And now to explore your blog further, you explain very well indeed.

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• I am with you on the negation of free will if only to understand how we cope with this mysterious venture through the four dimensional continuum. Not only would free will violate the natural laws controlling everything else but the concept is totally useless in working within the constraints of making sensible decisions (or the illusion of making decisions) since we live in a situation where we must safeguard ourselves judging on whatever is going on around us.

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• It’s a bit of a toughie indeed. To understand it better try looking at any recent day, but this time from both ends simultaneously (this is the advantage of hindsight).
Your day was filled with decisions—but you merely chose to do what you were going to do (at this point with most folks I get a triumphant “But! But, but I could have chosen other!” and when I say wisely “but you didn’t, did you, and therefore you could never have—the decision was in place waiting for you before you buttered your cornflakes that morning, before the First World War started, before Robin Hood hid in the forest, before the first block was laid for the Great Pyramid etc etc and absolutely inevitable.”

I get lots of blank stares especially from the Free Will people.
Usually I smile as nicely as I can and back away leaving them something else to think about, normally to the effect “Then pity God—for alone in the universe, He is incapable of a spontaneous thought …”

Someone whose name I’ve long forgotten said words to the effect that “In this fixed/static universe the only thing that moves is your perception.” (Something like that.)

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• As far as I understand it, free will was conceived as getting God off the hook of responsibility for His obvious screw-up of producing a creature who was deeply embedded in violating God,s explicit commands, thus releasing the Creator’s highly violent fury to massacre considerably large batches of his unfortunately imperfect creations. Since God was assumedly perfect and could not, by definition, manufacture imperfectness, something had to be invented to justify human misbehavior. Thus free will was invented, a theological counterpart to quantum theory.

I am a bit taken aback by the concept of buttering cornflakes. Aside from the fact that the enterprise would consume most of the day (unless one could quickly spray the bowl with a liquid butter fluid), the flavor of buttered cornflakes has no appeal to me at all.

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16. Did Argus perhaps mean buttered your toast? As opposed to cornflakes? I’m also intrigued by this breakfast choice.

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17. You can “lock” the “present” in your head for as long as you want to … but time is infinitely passing while you’re doing so.

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18. Reblogged this on Richard's Watch and commented:
Physicist Mekhi’s scientific definition of ‘now’ usefully augments my previous post on Justin Abraham’s outline of relativity and time. Also, the diagram usefully illustrates his description of slices of time and ‘before the beginning’, or pre- and post-Genesis. Don’t overlook the ensuing discussion from readers.

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19. I do not even know the way I ended up right here, however I thought this post used to be good. I don’t recognize who you might be but certainly you are going to a famous blogger in case you aren’t already 😉 Cheers!

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• Thank you very very much! To be honest i’m just a physics student attempting to popularise science in a day where it seems to have got lost amongst the masses 🙂

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20. I’ve blogged about time dilation and relativity a few times. For example here

https://thecuriousastronomer.wordpress.com/2013/05/30/einstein-and-time-travel/

and here

https://thecuriousastronomer.wordpress.com/2015/02/11/time-dilation-in-general-relativity/

So, no, “the present” is too local (personal) a concept, as what happens in the present and simultaneously is different for different observers. But, certainly the concept of time and something happening to you at the current time (in your frame of reference) are as real as anything else that we experience or observe.

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• Oh wonderful thank you very much – I shall be sure to give your posts a read!

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21. I never had a word for my belief about space and time until today – Four Dimensional Block Universe. Great explanation for the layperson. Now Einstein’s got my back so I will sound less crazy. maybe.

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• Thank you! Sadly when trying to talk about space and time in our society many people often think we’re crazy in the first place.. but in my opinion all the best people are.

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22. A very good, and easily understood, explanation of space-time. Me like it 🙂
But how does this tie into quantum mechanics? If the past, present and future, is one solid pre-defined body, and our “now” simply a hyperplane through this 4 dimensional solid, this implies that randomness doesn’t exist, right? How can randomness still exist at the quantum level …?

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23. If you look at a two dimensional painting as an insect crawling on its surface the present would be that spot it is consciously aware of at some point in its journey.The colors it observes on its journey may seem to be more or less extensive as it moves and causation seems to be their previous extent which increases or decreases in a kind of logic. But suddenly a strange dot of an unexpected color arrives in its movement. That would be a random event.

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24. I am reminded of the disciples asking their mentor, what happens tommorow. And the mentor says, be in the now, dont worry what happened before, dont worry of tommorow. As if he was really saying, Time is of the now. Whereas Einstein’s block simplifies what the mentor said and expanded on it.

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25. Heya are using WordPress for your blog platform?
I’m new to the blog world but I’m trying to get started and create my own. Do you require any coding expertise to make your own blog?
Any help would be greatly appreciated!

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• Hi – no coding software it’s just 100% wordpress

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26. Thanks for the insights into the illusion of “the present” and the idea that it is just a slice of a greater reality, just our own little frame of reference.

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27. God is eternal and we are eternal because all time is “now.” Now isn’t really “the present” since it’s all just now. Time is a human invention/convention… The universe is so unified that it can be bounded in less than a nutshell. This is all abstraction unless we move into the perception. I haven’t in my human self, but then I’m not really the human self, am I? What’s the practical takeaway? We can expand our ideas of the world and what it is and our conception of good and God. We can shift into something that works better for ourselves and humanity.

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• Illusion or whatever, the present is our handle on reality – it is where we can grab hold and shove and it’s all we’ve got. Humanity is that very odd species that has been able to take the fragments of perception donated by evolution to survive and prosper and fit it into a complex with all sorts of possibilities. The current world we have fabricated has enabled our control to create a huge perpetual conflict which profits only a self selected very few and squanders the wondrous gifts of our unique planet towards massive catastrophe. Einstein’s fabulous gifts have been diverted into the greatest crime imaginable which is nuclear weaponry hugely coveted by unimaginative powers of great stupidity who cannot conceive that this radioactive monster once freed will end everything. If there is a God, which I sincerely doubt, his sense of humor leaves me greatly unappreciative.

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• God’s humour? I think He and we would agree it’s not at all funny for He weeps over the situations we get ourselves in.
As for having a sense of humour, you won’t believe it!

It took me years to realise He was kindly chuckling over me. Having been contemptuous of Christians I’d heard some disagree with my universalist views and vowed I wouldn’t touch Baptists with a barge-pole ‘cos they’re such biblical bigots!
Eventually He came to sort me out and I found myself in a fellowship but didn’t know what variety of church as it was going through changes. Turned out to be Baptist!
One young elder use to say God has a humour, which is ridiculous – so I thought. Eventually I recalled that vow and twigged He certainly gets the last laugh – and had put me there to get a good grounding in His written word.

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• I have no way to presume the existence or non-existence of a being so superior to myself as people describe God but if humanity was so created I can judge the intent of a creator by its results and the very dark humor of energetic self destruction by humanity so totally mishandling the gifts of this planet can only fit the context of a frightful joke.

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• Thanks for explaining your perspective jiisand. It’s not a God I recognise however.

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28. I’m not going to try and be clever. The mind is boggling too much. I’m sure it’s good exercise.

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29. Pingback: Saving the Present·

30. Gosh I loved this. My obsession with the concept of time comes from a purely romanticised place. The physics of it, however, is an absolute wonder. Looking forward to broadening my horizon through this page.

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31. How about just BE, DO and HAVE…no thought to past, present or future.

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32. Pingback: Every Now and Zen: Time – Daedelus Kite·