Apologies to Dr. Alex Klimek for this TLDR rant.
Time Is Physics
Humans think of time as a line of moments that is ordered in one direction.
There is a past that is only there because it is recorded in something we see in the present like old fossils on a mountainside that used to be on the ocean floor half a billion years ago. The present exists. The future is open.
Philosophers call this presentism. …..basically they take any word and add “ism” to it which turns it into a whole damn specialty in philosophy. Medicine does the same thing with organs of the body.
Speed slows time down. This is Einstein’s special relativity thing. The famous 1971 experiment that flew two jets around the earth in opposite directions showed this. Right now you are heading east at 1000 miles an hour because the earth is rotating east. If you fly east on a jet increasing your speed relative to the earth’s 1000 mile an hour rotation eastward time slows down exactly as the lorentz transformations in the equations of relativity say. Speed up more and more and time slows down and down. So a photon going at the speed of light does not experience time (like whatever tf that means) because time has stopped.
Gravity also slows time down. This is Einstein’s general relativity theory. This is because mass slows down time. More and more mass (same as closer to the earth) the clock ticks slower. So at the surface of a black hole there is, just like for the photon, no time because the ticking of the clock has slowed to zero.
A remembered time that can't be cheated on Is it just an illusion that keeps us keepin' on
Time Is Statistics
The past is different than the future...Duh! However the equations of physics (except those of thermodynamics) do not have this distinction because they are all what math and physics folks call “time invariant”. An equation of motion does not know which way time goes but humans do. We look at the video and know right away that the pieces on the ground of the Eggman who fell off the wall in a Lewis Carroll skit do not just jump back up on the wall fully formed back into the Eggman. The equations of physics don’t “know” this.
Thermodynamics is the only science which gives us a narrative for why time goes one way. It is a strange story. We have to start with a little history (which is a sadly missing thing these woke, partisan, and entitled days).
Starting in the late 1700’s the French Revolution was interdigitated with the Scientific Revolution. The first revolutionary mayor of Paris was an astronomer. The great chemist Lavoisier was active in politics....so active, in fact, that the revolutionaries cut his head off….AND..
The mathematician, Lazare Carnot turned France’s army into a professional force to be reckoned with.
Carnot really liked the Persian poet Saadi Shirazi.Shirazi who wrote these words
that now stand at the entrance of the headquarters of the UN in New York. Yes, I agree, the UN has evolved into a sick parody. Sad.
Carnot even named his first son Sadi in honor of the poet Saadi. Sadi loved steam engines that were changing the world by using fire to make an axle turn, thereby doing work.
He wrote a pamphlet about how this fire turns an axle in a steam engine. He thought (wrongly) that heat is like thin congee soup that makes energy (that does the work) by falling or flowing from hot things to cold sorta like water in a waterfall falls and makes energy and does work. He was however, right about one thing: steam engines function because the heat passes from hot to cold.
Sadi’s pamphlet is read by the Prussian professor Rudolf Clausius. High school physics in Canada used to talk about him, but with the great dumb down of school, not any more.
His fundamental contribution was to see that a falling body (the water in the waterfall) can bounce (like a ball) but heat can’t bounce. It is lost….forever.
Clausius comes up with that entropy thingy….the change in entropy is never less than zero..…..in a closed system...the last phrase is the key...in a CLOSED system. So the universe will die a heat death….if the universe is closed. Big question!
But the real insight is made by the tragic Ludwig Boltzmann.
Ludwig Boltzmann committed suicide in 1906 while on vacation with his wife and small child in no small part due to being mocked by the scientific establishment of the time. He believed in atoms...many at the time did not. He believed the more atoms jiggled the more heat there was….many at the time did not. And he believed answer to time in the equations of physics was STATISTICAL.
He thought the jiggling of atoms was like a continuous shuffling of cards. If you have a new pack in order shuffling the pack disorders the cards. This one way disordering of cards is like the one way progression of hot to cold which is like the one way progression of time.
The combinatorial explosion (big time exponential compounding which makes Warren Buffet’s financial compounding seem tiny) is enormous in these mathy systems. Consider the possible ordering of a deck of cards...52 factorial (52!)…..you know...52x51x50 ….dot dot dot all the way down to 4 times 3 times 2 times 1. This 52! thingy is10 to the 68th power…a 1 with 68 zeros after it...just think about this number for a second or two...the YUGNESS of this number as trump (yes, small t) would say…billions of humans shuffling for millions of years won’t get to even a miniscule fraction of the possible number of different shuffles.
Boltzmann understood this. He came up with a famous formula
which is on his tombstone in the Central Cemetery of Vienna.
PS- That log thing is just the way that math makes big un-comprehensible (might be incomprehensible) numbers more understandable for humans.
Remember the blue and red balls of entropy from high school?...low vs high entropy….ordered on the left….low entropy...shuffled on the right….higher entropy….the universe only goes low to high....
Now what if you are colour blind and can’t tell red from blue. And what if you had great vision for texture and could tell that half the balls came from a different factory and had a slightly rougher surface than the other half. This is exactly the same as being able to see the cards ordered with respect to suit,
versus seeing them ordered with respect to number..
We choose blue and red or rough and smooth. We choose how to measure entropy. So we choose time. The big question then becomes, why were things more ordered in the past?
I will tell you why. Entropy was lower yesterday because it was even lower the day before yesterday and it was lower last year because it was even lower two years ago.… all the way back to the big bang. The End. Just accept it? Hey, I thought science wasn’t supposed to be dogmatic, like religion!
Ehhh…eh…What about that mammoth in the room?
The mammoth is very very smooth uniform cosmic background radiation. As you go back in time things become smoother and smoother...at the BB everything was perfectly smooth….perfectly smooth means maximal entropy...so according to this reasoning the entropy gets smaller and smaller as you go into the past….until the big bang when it is at a maximum. This is NOT an unnoticed paradox in the physics.
Time is lasting Fat neutrinos fall The math hits a wall Paradox will not be answered by asking But it is better than not asking at all
Time Is Biology
Neuroscience has shown that human brains are better with space evidence than time evidence. This is taken to mean that sometime in the past evolution co-opted areas of the brain that sensed space to sense time. A Nobel Prize was even handed out recently for something called place cells in rats. Or, maybe it was in mice. I forget.
Your brain is a time machine. Allostasis is the important word in neuro research these days which means that evolution made our human brain computationally big enough to run an energy budget to predict error (allostasis) versus just immediately reacting to correct error (homeostasis). Yes, this has something to do with consciousness.
All languages have phrases like we had us a long day, l am looking forward, in hindsight as remnants of this biological evolution. Time is the most used noun in the english language. We find time. We lose time. We save time. We spend time.
Neuroscience is saying that we are the time machine not the universe.
Or to put it a different way, as the now famous quote says, the 2nd law of thermodynamics is the 1st law of psychology.
Perhaps human time has something to do with human reaction time which is about a tenth of second...typically a human needs 100 milliseconds to register a finger pin prick in the brain and pull back the hand....a fly only needs 10 milliseconds..that’s why to the fly when you trying to kill it without a flyswatter your hand and arm seems to be moving in slow motion to the fly.
Here’s how to think about it. The earth is 12,000 km across. You stand on the earth and around you there is a big bubble of 100 milliseconds. Multiply this 100 milliseconds by the speed of light...so a tenth of a second times 300,000 km a second and you get 30,000 km...inside this bubble with a diameter of 30,000km our biological approximations are good enough...outside this sphere is completely different world..for a fly with a reaction time of only 10 milliseconds the bubble is 3000 km.
Maybe the wall clock looks different now? Just like it did for Salvidor Dali?
Does the world create our minds or our minds create the world Don’t ask me man because I firmly believe that space is curled Time may just be a loud crazy and nutty acid rock tune That we listen to with Rocket Man flying to the moon
PSS-for all the financial gurus out there managing risk….if there is no time there is no risk….have to leave this for another rant as I’m afraid Dr. Klimek will say this one is already too long.