Tag: Entropy

Yet more of the big question.

Time!

I wasn’t going to publish a post for today but then yesterday I read this article on The Conversation and wanted to share it with you. In fact it shares much of what I posted on the 1st, The Big Question. Because time and infinity are beautifully connected.

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What is time – and why does it move forward?

By Thomas Kitching, Lecturer in Astrophysics, UCL

Imagine time running backwards. People would grow younger instead of older and, after a long life of gradual rejuvenation – unlearning everything they know – they would end as a twinkle in their parents’ eyes. That’s time as represented in a novel by science fiction writer Philip K Dick but, surprisingly, time’s direction is also an issue that cosmologists are grappling with.

While we take for granted that time has a given direction, physicists don’t: most natural laws are “time reversible” which means they would work just as well if time was defined as running backwards. So why does time always move forward? And will it always do so?

Does time have a beginning?

Any universal concept of time must ultimately be based on the evolution of the cosmos itself. When you look up at the universe you’re seeing events that happened in the past – it takes light time to reach us. In fact, even the simplest observation can help us understand cosmological time: for example the fact that the night sky is dark. If the universe had an infinite past and was infinite in extent, the night sky would be completely bright – filled with the light from an infinite number of stars in a cosmos that had always existed.

For a long time scientists, including Albert Einstein, thought that the universe was static and infinite. Observations have since shown that it is in fact expanding, and at an accelerating rate. This means that it must have originated from a more compact state that we call the Big Bang, implying that time does have a beginning. In fact, if we look for light that is old enough we can even see the relic radiation from Big Bang – the cosmic microwave background. Realising this was a first step in determining the age of the universe (see below).

But there is a snag, Einstein’s special theory of relativity, shows that time is … relative: the faster you move relative to me, the slower time will pass for you relative to my perception of time. So in our universe of expanding galaxies, spinning stars and swirling planets, experiences of time vary: everything’s past, present and future is relative. 

So is there a universal time that we could all agree on?

The universe’s timeline. Design Alex Mittelmann, Coldcreation/wikimedia, CC BY-SA

It turns out that because the universe is on average the same everywhere, and on average looks the same in every direction, there does exist a “cosmic time”. To measure it, all we have to do is measure the properties of the cosmic microwave background. Cosmologists have used this to determine the age of the universe; its cosmic age. It turns out that the universe is 13.799 billion years old. 

Time’s arrow

So we know time most likely started during the Big Bang. But there is one nagging question that remains: what exactly is time? 

To unpack this question, we have to look at the basic properties of space and time. In the dimension of space, you can move forwards and backwards; commuters experience this everyday. But time is different, it has a direction, you always move forward, never in reverse. So why is the dimension of time irreversible? This is one of the major unsolved problems in physics. 

To explain why time itself is irreversible, we need to find processes in nature that are also irreversible. One of the few such concepts in physics (and life!) is that things tend to become less “tidy” as time passes. We describe this using a physical property called entropy that encodes how ordered something is.

Imagine a box of gas in which all the particles were initially placed in one corner (an ordered state). Over time they would naturally seek to fill the entire box (a disordered state) – and to put the particles back into an ordered state would require energy. This is irreversible. It’s like cracking an egg to make an omelette – once it spreads out and fills the frying pan, it will never go back to being egg-shaped. It’s the same with the universe: as it evolves, the overall entropy increases.

Unfortunately that’s not going to clean up itself. Alex Dinovitser/wikimediaCC BY-SA

It turns out entropy is a pretty good way to explain time’s arrow. And while it may seem like the universe is becoming more ordered rather than less – going from a wild sea of relatively uniformly spread out hot gas in its early stages to stars, planets, humans and articles about time – it’s nevertheless possible that it is increasing in disorder. That’s because the gravity associated with large masses may be pulling matter into seemingly ordered states – with the increase in disorder that we think must have taken place being somehow hidden away in the gravitational fields. So disorder could be increasing even though we don’t see it.

But given nature’s tendency to prefer disorder, why did the universe start off in such an ordered state in the first place? This is still considered a mystery. Some researchers argue that the Big Bang may not even have been the beginning, there may in fact be “parallel universes” where time runs in different directions

Will time end?

Time had a beginning but whether it will have an end depends on the nature of the dark energy that is causing it to expand at an accelerating rate. The rate of this expansion may eventually tear the universe apart, forcing it to end in a Big Rip; alternatively dark energy may decay, reversing the Big Bang and ending the Universe in a Big Crunch; or the Universe may simply expand forever.

But would any of these future scenarios end time? Well, according to the strange rules of quantum mechanics, tiny random particles can momentarily pop out of a vacuum – something seen constantly in particle physics experiments. Some have argued that dark energy could cause such “quantum fluctuations” giving rise to a new Big Bang, ending our time line and starting a new one. While this is extremely speculative and highly unlikely, what we do know is that only when we understand dark energy will we know the fate of the universe.

So what is the most likely outcome? Only time will tell.

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Let me explain, in part, entropy. Because while I and many others sort of understand it, the principle behind entropy is much more detailed.

It is explained pretty well on WikiPedia, from which I reproduce the first paragraph.

Entropy is a scientific concept, as well as a measurable physical property that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamics, where it was first recognized, to the microscopic description of nature in statistical physics, and to the principles of information theory. It has found far-ranging applications in chemistry and physics, in biological systems and their relation to life, in cosmologyeconomicssociologyweather scienceclimate change, and information systems including the transmission of information in telecommunication.[1]

There’s a little bit more to read … 😉

Again, I am going to finish with sharing that image from Unsplash.

Imagine the universe is constant whichever direction one looks in, to 1 in 10,000. That is truly amazing!

Up, Up And Away?

It is very hard to avoid hyperbole when one speaks of global warming.

I am indebted to The Nation magazine, May 8/15 Issue, in which is included a feature article authored by Bill McKibben. My sub-heading is much of what Bill wrote in his first line.

It is hard to avoid hyperbole when you talk about global warming. It is, after all, the biggest 
thing humans have ever done, and by a very large margin.

A few sentences later, Bill offers this:

In the drought-stricken territories around the Sahara, we’ve helped kick off what The New York Times called “one of the biggest humanitarian disasters since World War II.” We’ve melted ice at the poles at a record pace, because our emissions trap extra heat from the sun that’s equivalent to 400,000 Hiroshima-size explosions a day.

Yet what scares me, scares me beyond comprehension, is the almost universal disregard being shown by Governments and those with power and influence right across the world to what in anyone’s language is the most pressing catastrophe heading down the tracks. Not next year; not tomorrow, but now!

Or in Mr. McKibben’s words, once more from that Nation article:

But as scientists have finally begun to realize, there’s nothing rational about the world we currently inhabit. We’re not having an argument about climate change, to be swayed by more studies and journal articles and symposia. That argument is long since won, but the fight is mostly lost—the fight about the money and power that’s kept us from taking action and that is now being used to shut down large parts of the scientific enterprise. As Trump budget chief Mick Mulvaney said in March, “We’re not spending money on that anymore. We consider that to be a waste of your money to go out and do that.” In a case this extreme, scientists have little choice but to be citizens as well. And given their credibility, it will matter: 76 percent of Americans trust scientists to act in the public interest, compared with 27 percent who think the same thing about elected officials.

Whatever your response is to what I have already presented, the one thing that I do know is that you have been aware of humanity’s effect on our atmosphere for many, many years. Indeed, Bill McKibben wrote his first book twenty-eight years ago!

His 1989 book The End of Nature is regarded as the first book for a general audience about climate change, and has appeared in 24 languages; he’s gone on to write a dozen more books.

But I would be the first to acknowledge that back in 1989 while I did become aware of Bill McKibben and did purchase and read that book of his, I didn’t see the effects he prophesied. In addition, I didn’t understand the mechanisms that would bring those effects into place.

Now, today, it’s very difficult to deny that global weather systems are behaving in ways that most do not understand albeit we do understand how those weather changes are affecting our lives.

One person who did, and still does even more, understand the physics involved in our changing weather, is Patrice Ayme. For some nineteen years after Bill McKibben’s first book, Patrice published a post on his blog. I have been following Patrice’s blog for some years and while I would be the first to stick my hand in the air and declare that some of his posts are a little beyond me, there’s no question of the integrity of his writings and his bravery in spelling out the truth of these present times. (OK, the truth a la Monsieur Aymes but I would place a decent bet of PA being closer to the core truth of many issues than Joe Public.)

I am indebted to Patrice for granting me permission to republish that post. Please read it. Don’t be put off by terms that may not be familiar to you. Read it to the end – the message is very clear.

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Applying Equipartition Of Energy To Climate Change PREDICTS WILD WEATHER.

By Patrice Ayme, March 8th, 2008.

Lately, the world weather has been especially perplexing, influenced by the cold ocean temperatures of a La Niña current in the equatorial Pacific. For Earth’s land areas, 2007 was the warmest year on record.

This year, record cold is more the norm. Global land-surface temperatures so far are below the 20th-century mean for the first time since 1982, according to the National Climatic Data Center. Last month in China, snowstorms stranded millions of people, while in Mumbai, officials reported the coldest day in 46 years.

Yet, England basked in its fourth-warmest January since 1914, the British Met Office reported. The crocus and narcissus at the U.K.’s Royal Botanical Gardens at Kew flowered a week earlier than last year — 11 days ahead of their average for the decade and weeks ahead of their pattern in the 1980s. In Prague, New Year’s Day was the warmest since 1775.

“It is difficult to judge the significance of what we are seeing this year,” said Kew researcher Sandra Bell. “Is it a glitch or is it the beginning of something more sinister and alarming?”” (Robert Lee Hotz, Wall Street Journal, March 8, 2008).

Many scientists have pondered this question, as if they did not know the answer, but it is a straightforward application of thermodynamics.

A basic theorem of equilibrium thermodynamics, the EQUIPARTITION OF ENERGY theorem, says that the same amount of energy should be present in all degrees of freedom into which energy can spill.

(How does one demonstrate this theorem? Basically, heat is agitation, kinetic energy at the scale of atoms and molecules. This agitation can spill in a more organized manner, in great ensembles, such as vast low and high pressure systems, or large scale dynamics. See the note on entropy and negative temperatures.)

In the case of meteorology, this implies, oversimplifying a bit, that only one-third of the energy should go into heat (and everybody focuses on the augmentation of temperature). Now, of course, since the energy enters the system as heat, non equilibrium thermodynamics imposes more than one-third of the energy will be heat.

As time goes by, though, the other two degrees of freedom, potential energy (represented as the geometry of gradients of pressures, high and low pressure systems, hurricanes) and dynamics (wind speed and vast movements of air masses of varying temperatures and/or pressure; and the same for sea currents) will also store energy.

Thus the new heat created in the lower atmosphere by the increased CO2 greenhouse will be transformed in all sorts of weather weirdness: heat, cold, high and low pressures, wind, and big moves of big things. Big things such as vast re-arrangements of low and high pressure systems, as observed in the Northern Hemisphere, or the re-arrangement of sea currents as apparently also observed, and certainly as it is expected. Since it happened in the past (flash ice age of the Younger Dryas over Europe, 18,000 years ago).

As cold and warm air masses get thrown about, the variability of temperatures will augment all over.

In other words, record snow and cold in the Alps and record warmth simultaneously in England is a manifestation of the equipartition of energy theorem applied to the greenhouse warming we are experiencing. It is not mysterious at all, and brutal variations such as these, including sudden cold episodes, are to be expected, as more and more energy gets stuffed in the planetary climate, and yanks it away from its previous equilibrium.

Wind speed augmentations have already had a spectacular effect: by shaking the waters of the Austral ocean with increasingly violent waves, carbon dioxyde is being removed as if out of a shaken carbonated drink. Thus the Austral ocean is now a net emitter of CO2 (other oceans absorb CO2, and transform it into carbonic acid).

Hence the observed variations are the beginning of something more sinister and alarming. Climate change is changing speed. Up, up, and away.

Patrice Ayme
Patriceayme.com
Patriceayme.wordpress.com.

Note on entropy: Some may object that transforming heat into collective behavior of vast masses of air or sea violates the Second Law Of Thermodynamics, namely that entropy augments always, in any natural process. Well, first of all, the genius of the genus Homo, not to say of all of life itself, rests on local violations of the Second Law. Secondly, the most recent physics recognizes that fundamental considerations allow systems where increased energy lead to increased order (such a system is said to be in a negative temperature state).

Even more revealingly, a massive greenhouse on planet Earth would lead, as happened in the past, to a much more uniform heat, all around the planet, that is, a more ordered state. Meanwhile, the transition to the present order of a temperate climate to the completely different order of an over-heated Earth will bring complete disorder, as observed.

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Going to leave you with a picture taken from weather.com

An emaciated polar bear is seen on a small sheet of ice in this image taken in August in Svalbard, north of mainland Norway. (Kerstin Langenberger)

Please, please, please: make a difference! Environmentally, domestically and politically, please make a difference.