The spelling is more akin to the 'Lallans' of our National Bard.
They took nae pains their speech to balance,
Or rules to gie;
But spak their thoughts in plain, braid lallans,
Like you or me.
—Robert Burns in Epistle To William Simson
They took nae pains their speech to balance,
Or rules to gie;
But spak their thoughts in plain, braid lallans,
Like you or me.
—Robert Burns in Epistle To William Simson
You've never expressed an opinion other than to dismiss the idea that it’s anything but just ‘time’, a blank canvas. Absolutely nothing wrong with that because in doing so you’re in the company of Newton and to some degree Einstein plus many other eminent people.
It may well be that time, reality- call it what you will - is just a giant set of ‘nows’ across the whole expanse of the universe. However, those ‘nows’ must have followed a specific path (in amongst many possible options)to arrive at the present otherwise you wouldn’t exist as you do now, or anything else. Therefore there is a past. And if something has longitudinal validity it must be a thing.
Time’s Arrow and Archimedes’ Point by Huw Price explains it very well, if you can get through it (it’s rather philosophical). Quick summary: if the universe were to slow down its expansion, stop expanding, then begin contracting, time’s Direction would reverse, too.
https://en.wikipedia.org/wiki/Arrow_of_time
https://en.wikipedia.org/wiki/Arrow_of_time
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Carlo Rovelli says the past and future exist because of heat.
The only law of physics that is not time-reversible is the second law of thermodynamics.
The 2nd law says that, as time goes by, the amount of disorder, or entropy, in the Universe will always increase.
Time travels in only one direction, but merely because we see things are irretrievably changed going forward. This is due to the irreversible progress of heat
Time's arrow therefore points from a low entropy past to a high entropy future.
I read the bulk of the above here: https://blog.12min.com/the-order-of-time-pdf-summary/
Attachments
Without wanting to appear like a gnat in the presence of an intellectual giant, I can agree with Carlo Rovelli. Heat always cools, and to my mind it creates time. But maybe it’s deeper than that. Whenever energy is expended, it creates time whether it is heat, acceleration etc. This happens because you are shifting an object’s time reference with respect to its surroundings. This even applies when an object cools.
I don’t know that there can be energy dissipation of any kind without invoking the idea of time. So if this is the case (and I am open to correction), could it not be that energy dissipation at the cosmos level creates time? That’s the question that bugs me. How does 10^54 watts (total output of all stars in the cosmos IIRC) translate to 73km/s per mega parsec expansion which is equivalent to a time rate production of 73km/c seconds per mega parsec? (Please correct my crude math if it’s wrong 😑)
I don’t know that there can be energy dissipation of any kind without invoking the idea of time. So if this is the case (and I am open to correction), could it not be that energy dissipation at the cosmos level creates time? That’s the question that bugs me. How does 10^54 watts (total output of all stars in the cosmos IIRC) translate to 73km/s per mega parsec expansion which is equivalent to a time rate production of 73km/c seconds per mega parsec? (Please correct my crude math if it’s wrong 😑)
It should be pointed out the question of time‘s direction is now moot, if the Direction of time is as Huw Price described it. Since they found out that the universe is not rpt not slowing it’s expansion but it’s expansion is accelerating. Maybe that explains why Huw Price’s book goes for about 5 bucks on Amazon.
Can a book on time be out of date? 🤔
Fact is, Price's book was published 27 years ago, whereas Rovelli's was published only 5 years ago.
I too was looking into Huw Price's credentials here, as is my wont in such hot matters as Cosmology, Geoff. Turns out he has an illustrious career as a Philosophy Professor at the University of Sidney and Sidney Sussex, Cambridge. But little evidence his Physics is up to much.
https://www.amazon.co.uk/Times-Arrow-Archimedes-Point-Directions/dp/0195100956
In fact his 1996 book seems to be a Word Salad about the Ancient Greeks and an awful lot of wordy speculation.
Some reviews:
No maths. Then not Science, IMO.
Gullible layman in other words.... 🙄
AFAIK, and this is based on CPT (Charge, Parity and Time) conservation, if time reversed, electrons/baryons would turn into anti-electrons/baryons and come right back to hit us and the whole thing would blow up! Hope you get the idea. It's just wild speculation by Prof. Price IMO.
Now Carlo Rovelli is a proper Physicist, even if in the very vague Loop Quantum Gravity camp. I have read a couple of his books and certainly like his ideas about information theory as being important.
I am struggling to follow you here, m'learned friend, Bonsai.
I don't get the bit about a modest 160,000 mph expansion (73km/s ) over a distance (A Million Parsecs) slightly further away than the Andromeda Nebula (2.5 million light years) creating Time at all. Why should it?
My current Physics Books, got them today from Central Library Portsmouth. The Feynman book is awesome:
Guy was SO bright. I am sure I shall agree with everything Professor Lisa Randall of Harvard has to say, too. On inspecting the jacket, I discover the woman is a BABE!
😍
The expansion is modest locally, but at 13.8 billion LY it is not, as you well know. And objects that are gravitationally bound, as is the Milky Way and Andromeda, will not experience expansion. You know that as well.
What is the point you are trying to make in this discussion?
What is the point you are trying to make in this discussion?
Could it be that time is an emergent property of the underlying vacuum energy of 'empty' space.
As random quantum fluctuations of force fields happen in the vacuum of space, time itself may happen - tick by tiny tick! 🤓
'Empty' space is a seething cauldron of energy, and therefore a potentially endless progenitor of time!
Huw Price’s book was way ahead of the times at that time, now he’s behind the times. He must be in imaginary time. 😬 But you never know, maybe the book is timeless..
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Yes, The two galaxies are expected to merge with each other in about 4.5 billion years time.
Andromeda looks to have merged with another member of our local group of galaxies in the past.
Observations show its nucleus to have two supermassive black holes circling each other. It is believed that this is the result of Andromeda merging with another galaxy which also contained a supermassive black hole.
The Hubble Space Telescope image of Andomeda's nucleus (The right hand image above) reveals two bright spots, each thought to be a densely packed swarm of stars around a supermassive black hole.
The brighter spot is thought to be the nucleus of the galaxy swallowed by Andromeda because the true centre of the Andromeda galaxy coincides with the dimmer spot.
The problem with the ‘seething cauldron of vacuum energy’ and actual equivalent real energy (2-3 hydrogen atoms per cubic meter in intergalactic space) is 120 orders of magnitude. One of the great mysteries of physics.
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There you go - the beginning of a big crunch... i.e. the next turn of the big tumbler... the guy is a genius 😉
//
re The Big Crunch, excerpt from wiki page fir The Big Crunch,
The Big Crunch is a hypothetical scenario for the ultimate fate of the universe, in which the expansion of the universe eventually reverses and the universe recollapses, ultimately causing the cosmic scale factorto reach zero, an event potentially followed by a reformation of the universe starting with another Big Bang. The vast majority of evidence indicates that this hypothesis is not correct. Instead, astronomical observations show that the expansion of the universe is accelerating rather than being slowed by gravity, suggesting that the universe is far more likely to end in heat death.[1][2][3] However, there are new theories that suggest that a "Big Crunch-style" event could happen by the way of a dark energyfluctuation; however, this is still being debated amongst scientists.[4]
The Big Crunch is a hypothetical scenario for the ultimate fate of the universe, in which the expansion of the universe eventually reverses and the universe recollapses, ultimately causing the cosmic scale factorto reach zero, an event potentially followed by a reformation of the universe starting with another Big Bang. The vast majority of evidence indicates that this hypothesis is not correct. Instead, astronomical observations show that the expansion of the universe is accelerating rather than being slowed by gravity, suggesting that the universe is far more likely to end in heat death.[1][2][3] However, there are new theories that suggest that a "Big Crunch-style" event could happen by the way of a dark energyfluctuation; however, this is still being debated amongst scientists.[4]
I've mentioned before, TNT, that we may be heading for a Big Rip in around 22 billion years from now!
If the accelerating expansion of the universe increases constantly, the end result will be that the distances to galaxies will be stretched to infinity (hence the term Big Rip), and the diameter of the observable Universe will shrink to zero.
However, you'll know that this is only yet another hypothesis regarding the fate of the Universe! 🤓