Physics – Super Facts

Brief Answers to the Big Questions – Review

The goal of this blog is to create a list of what I call super facts. Super facts are important and true facts that nevertheless are surprising to a lot of people, mind-blowing, or misunderstood or disputed among non-experts. They are special facts that we all can learn something important from. However, I also create posts that are not super facts but feature other interesting information, such as this book review and book recommendation. The book is:

Brief Answers to the Big Questions by Stephen Hawking

Below I am listing the four editions of this book. I bought and read the hardback version.

Hardback – Publisher : Bantam (October 16, 2018), ISBN-10 : 1984819194, ISBN-13 : 978-1984819192, 256 pages, item weight : 12.8 ounces, dimensions : 5.55 x 0.8 x 8.1 inches. It costs $11.58 on US Amazon. Click here to order it from Amazon.com.
Paperback – Publisher : Random House Large Print (November 13, 2018), ISBN-10 : 1984887262, ISBN-13 : 978-1984887269, 352 pages, item weight : 10 ounces, dimensions : 5.3 x 0.82 x 7.8 inches. It costs $27.00 on US Amazon. Click here to order it from Amazon.com.
Kindle – Publisher : Bantam (October 16, 2018), ASIN : B07D6BBGKL, ISBN-13 : 978-1984819208, 227 pages, it costs $5.99 on US Amazon. Click here to order it from Amazon.com.
Audiobook – Publisher : Random House Audio (October 16, 2018), ASIN : B07FW4NT2X, Listening length : 4 hours and 51 minutes. $0.99 with membership. Click here to order it from Amazon.com.

The front cover features the title and the name of author Stephen Hawking author of A Brief History of Time. This is on a blue background featuring two blue circles. — The front cover of Brief Answers to the Big Questions by Stephen Hawking. Click on the image to go to the Amazon page for the hardback version of the book.

Amazon’s Description of the Book

“Hawking’s parting gift to humanity . . . a book every thinking person worried about humanity’s future should read.”—NPR

NAMED ONE OF THE BEST BOOKS OF THE YEAR BY Forbes • The Guardian • Wired

Stephen Hawking was the most renowned scientist since Einstein, known both for his groundbreaking work in physics and cosmology and for his mischievous sense of humor. He educated millions of readers about the origins of the universe and the nature of black holes, and inspired millions more by defying a terrifying early prognosis of ALS, which originally gave him only two years to live. In later life he could communicate only by using a few facial muscles, but he continued to advance his field and serve as a revered voice on social and humanitarian issues.

Hawking not only unraveled some of the universe’s greatest mysteries but also believed science plays a critical role in fixing problems here on Earth. Now, as we face immense challenges on our planet—including climate change, the threat of nuclear war, and the development of artificial intelligence—he turns his attention to the most urgent issues facing us.

Will humanity survive? Should we colonize space? Does God exist? These are just a few of the questions Hawking addresses in this wide-ranging, passionately argued final book from one of the greatest minds in history.

Featuring a foreword by Eddie Redmayne, who won an Oscar playing Stephen Hawking, an introduction by Nobel Laureate Kip Thorne, and an afterword from Hawking’s daughter, Lucy, Brief Answers to the Big Questions is a brilliant last message to the world.

This is my five star review for the book Brief Answers to the Big Questions

Smart but Brief Answers to Some Big Questions

People want answers to the big questions. Is there a God? How did it all begin? Is time travel possible? Is there other intelligent life in the Universe? Will artificial intelligence outsmart us? Will we survive on Earth? Should we colonize space? That’s some of the questions that Stephen Hawking address in this book. Stephen Hawking is answering these questions as simply and as briefly as possible at the same time as he uses advanced scientific knowledge and his deep insights and intelligence to do it. However, to read this book you need to be curious and open to using scientific knowledge and logic. The book is for those who intentionally seek the truth and not confirmation of their existing beliefs. That does not mean that Stephen Hawking will arrive at conclusive answers “Yes” or “No” answers.

Take for example the question “Is there a God?” His answer is not “Yes” or “No”. His answer is to explain why the Universe does not need a creator and assuming that the cosmological viewpoint that time and space came into existence with the Big Bang, why the Universe cannot even have a creator. He is using modern physics and logic to deduct those answers, but they are not identical to a simple “No”. As to whether we will survive on Earth, he states that global warming, which is caused by us burning fossil fuels, is potentially a civilization destroying threat, which we may not survive during the next 1,000 years. He says the same thing about nuclear weapons, which do not seem to go away and instead more countries want to adapt. At some point during the next 1,000 years something could go very wrong, whether it is a total nuclear war or runaway global warming. He is also concerned that malevolent Artificial Intelligence could one day outsmart us. He talks about the doomsday clock. These are all well informed opinions but not definite answers.

Along the way we learn about a lot of concepts from science, especially physics. We learn about quantum physics, special and general relativity, black holes, gravitational collapse, the big bang, inflation (the cosmological kind), multiverses, the strong and weak anthropic principle, the information paradox, hawking radiation, antiparticles, virtual particles, supertranslations, cosmic strings, the Higgs Boson, the Large Hadron Collider, vacuum fluctuations, the Casimir effect, the chronology protection conjecture, nuclear fusion, nanocrafts, the technological singularity, etc. He does not explore these concepts in depth but explains them well enough to be useful for answering the big questions for laymen. He is obviously an admirer of Albert Einstein, and I think for good reason I should add.

This book is written for laymen, people who are not physicists, and not experts on these matters. It is well written and relatively easy to understand. Not everyone will like all of the answers but as a reader make sure you understand the arguments and facts before you reject an answer because you don’t like it. Stephen Hawkings was an amazing scientist and he is certainly missed. I highly recommend this book to everyone.

The back cover features advance praise for the book by the New York Times, as well as a list of the Big Questions that he is answering. The text is white on a dark blue background. — The back cover of Brief Answers to the Big Questions by Stephen Hawking. Click on the image to go to the Amazon page for the paperback version of the book.

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100 trillion Ghostly Particles Passes Through Your Body Every Second

Super fact 132 : An estimated 100 trillion ghostly elementary particles, called neutrinos, pass through your body every second, which is 237 sextillion particles in 75 years. Despite that fact the chance that even a single neutrino will interact with an atom in your body during your entire life is about 1 in 4. These extremely abundant particles pass right through you as well as planets without interactions, like ghosts.

The picture shows a transparent glass like human body and thousands of racing particles passing right through the body. | 100 trillion Ghostly Particles Passes Through Your Body Every Second — 100 trillion neutrinos, almost entirely undetectable elementary particles, pass right through your body every second, without touching a single atom in your body, as if you don’t exist. I generated the picture with the help of ChatGPT.

Neutrinos are tiny subatomic particles, often called ‘ghost particles‘ because they barely interact with anything else. They are capable of passing right through our planet Earth as if it wasn’t there. As mentioned, an estimated 100 trillion neutrinos pass through your body every second.

Neutrinos do not interact with electromagnetic forces and not with the strong nuclear force. The electromagnetic forces are what is governing molecules, atoms, and matter and the strong nuclear force governs the nucleus of atoms. The only forces that neutrinos interact with are the weak nuclear force and gravity, which both are weak forces, and the weak nuclear force has a very short range. In addition, the mass of neutrinos is extremely tiny. That is why neutrinos pass through atoms as if they aren’t there, and it is why trillions of neutrinos can pass through your body without touching you even the slightest and it is also why they are completely harmless. This also makes them extremely hard to detect.

The illustration depicts different kinds of radiation hitting different obstacles including a sheet of paper, a sheet of aluminum foil, a sheet of lead, a container / pool of water, and planet earth. There are different kinds of rays that are stopped by the different obstacles, except the neutrinos go through everything. — Alpha radiation is stopped by paper. Beta radiation (electrons) is stopped by aluminum foil. X-rays and gamma radiation (high energy photons) are stopped by a sheet of lead. Neutrons with certain energies can be stopped by a container of water. Neutrinos cannot even be stopped by a planet. Shutterstock asset id: 2313420693 by Anshuman Rath

An enormous amount of neutrinos flows right through your body as if you don’t exist. They are coming from the sky and from the ground below after passing through earth and none of them will touch any part of you. This is a mind blowing and surprising but not well known fact and therefore a super fact in my opinion.

The Mass of Elementary Particles

More than 200 subatomic particles have been discovered and there are probably many more that have not yet been discovered. Examples of subatomic particles are protons, neutrons and electrons. However, only some of them are elementary particles, or in other words fundamental particles. The electron is a fundamental particle, but the proton and the neutrons are not. Protons and neutrons are called composite particles and consist of quarks, gluons and mesons. The neutrino is an example of a fundamental particle like the electron. Quarks are other examples of fundamental particles.

The illustration is a map of the 17 fundamental particles, but the anti-particles are not included. There are six leptons including the electron and neutrino, six quarks, and five bosons, the photon, gluon, Z Boson, W Boson, and the Higgs Boson. | 100 trillion Ghostly Particles Passes Through Your Body Every Second — There are 17 elementary particles, 34 if you count their anti-particles and 61 if you count all flavors. It is possible to count even more of them if you count left-right-handedness and polarization as separate types of particles. This is the Standard Model of Elementary Particles Shutterstock asset id: 2148276355 by alionaursu

Electrons are lightweight. They weigh 0.511 MeV/c², which is 1,836 times lighter than a proton, which weighs 938.272 MeV/c². The positron, which is the electrons anti-particle weighs exactly the same as the electron. The muon, which is very similar to an electron but is unstable and is 206.77 times heavier than an electron weighs 105.66 MeV/c². The tau is also similar to an electron and is about 3,477 times heavier than an electron and weighs 1,776.86 MeV/c². Quarks are also much heavier than electrons. Photons and gluons are massless.

The neutrino is a lepton and is in some ways similar to an electron, but it has no charge and does not interact with electromagnetic forces at all. The neutron also does not have any charge, but it does interact with electromagnetic forces, which makes it a lot easier to detect. As in the case for the electron there are lighter and heavier versions of neutrinos, the electron-neutrino, the muon-neutrino and the tau-neutrino. Here comes the shocker; the heaviest flavor of neutrino, the tau-neutrino weighs less than 0.12 eV/c² or 0.00000012 MeV/c² making it at least 4 million times lighter than an electron. However, the neutrinos may be a lot lighter than that. We don’t know. They have mass but it is very tiny.

Considering how tiny neutrinos are, and that they don’t interact with the electromagnetic force at all (unlike other neutral particles) and don’t interact with the strong nuclear force at all, it is understandable that neutrinos are like ghost particles, almost impossible to detect. Neutrinos are too light to be so called dark matter, but a hypothetical heavier form of neutrino called the sterile neutrino is a plausible candidate for dark matter.

Other Physics Related Super facts

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Everything is in Motion

Super fact 131 : There is no absolute reference point. All motion is relative. Since everything is in motion compared to something else, that means that everything is in motion. In addition, all material objects consist of particles that are in motion, and all objects with mass move through time.

I previously made a post on this topic called “Everything is in Motion – Stream of Consciousness”. For a Stream of Consciousness post you are supposed to write whatever comes to mind without editing, except for typos. Stream of Consciousness is a fun concept. However, it is not fit for a super fact post because a super fact post requires fact checking and linking to reputable sources and it needs to be well organized and well explained, and all that is editing. After writing Everything is in Motion – Stream of Consciousness I realized that “Everything is in Motion” is a super fact. It is an important observation and a fact that is far from obvious. With this post I am rewriting “Everything is in Motion – Stream of Consciousness” into a super-fact I call “Everything is in Motion”.

All Motion is Relative

All motion is relative and everything moves in comparison to something else. You may be sitting in your chair completely still thinking that you are not moving but you are. Earth rotates around its axis at 1,040 miles per hour at the equator, and at 733 miles per hour at latitude 45 degrees. Latitude 45 degrees goes through New York and other northern States, as well as Europe. Sitting at the geographic north Pole won’t help you either because Earth is also wobbling and it is rotating around the sun at roughly 67,000 miles per hour or 107,000 kilometers per hour.

Picture shows a man and his dog sitting in front of a computer. Earth and the sun are in the background. — Man thinking he is sitting still drawn with the help of ChatGPT

The picture below shows Earth’s three main orbital cycles. I used this picture in another context for super-fact #122 “Orbital Cycles are not the Cause of the current Global Warming”. In that context I wanted to point out that Earth’s orbital cycles are too slow (100,000 years, 41,000 years, and 26,000 years) to explain the sudden rapid rise in global temperatures that we are witnessing now. The orbital cycles are also currently slowly cooling Earth, not warming it. However, in this context I am using the picture for a different purpose, and that is to point out that even if you sit at the north pole (or anywhere else on Earth) you will be moving.

Three illustrated orbital cycles. On the left orbital eccentricity, in the middle is the axial tilt and on the right axial precession. | Everything is in Motion — Illustration of Milankovitch cycles from MIT’s Climate Primer.

In addition, the sun is rotating around the center of our galaxy, the Milky Way at 514,000 to 560,000 miles per hour or 792,000 to 828,000 kilometer per hour, and our galaxy and the Andromeda galaxy are approaching each other at the speed of 110 kilometers per second, which is 396,000 kilometers per hour, or 246,000 miles per hour. Whether it is the Andromeda galaxy that is approaching us or our galaxy that is approaching the Andromeda galaxy is just a point of view. We are also moving at millions and billions of miles of hour compared to some other galaxies.

Photo of the Andromeda Galaxy — Photo by Pixabay on Pexels.com

You are also Moving Through Time

As mentioned, motion is not absolute. It is always relative to something else. The universe has no center, no ether to compare with, there is no absolute reference point. It is not possible to declare anything as truly standing still. Understanding this is the first step towards understanding the theories of relativity. According to the theories of relativity the speed of light, or the speed of light in vacuum if you will, is a universal constant c = 299,792,458. The speed of light in vacuum is the same for all observers regardless of their speed and the direction in which they are going. In other words, you are moving at the speed of c = 299,792,458 compared to all light.

A spaceship on the right is shooting out a laser beam towards the left. Alongside the laser beam are four rockets trying to catch up with the light beam.Everything is in Motion — Four rockets, A, B, C, and D, are traveling along a light (laser) beam. No matter how fast they travel along the light beam, the light beam will always travel c = 299,792,458 meters per second faster than they do. I generated this picture with the help of ChatGPT.

In addition, c = 299,792,458 is not a speed in a regular sense, but a conversion factor between space and time. All particles/objects without mass (light particles called photons, gluons and gravity waves) must always travel at this speed, whilst all objects that have mass can only travel slower than c = 299,792,458 (compared to other objects with mass).

The E = mc2 formula — Mass is energy and vice versa, a direct result of the way time and space are related. Stock Photo ID: 2163111377 by Aree_S

You could say that compared to the reference frame of my choosing, which happens to be the chair I am sitting in, I am sitting still. I am not sure that would be fair but according to the theories of relativity you are also moving through time at the speed of c = 299,792,458. Well, that is assuming you have mass. For mass-less particles, like photons, time does not exist. Anyway, the fact that you are always moving kind sneaks in, no matter what you try.

An eye with photons streaming into it. | Everything is in Motion — Billions of photons coming into the eye. For them time does not exist. Shutterstock asset id: 2629068895 by muratart.

You could raise a couple of objections to some of the claims in the last paragraphs. Very far away, beyond the limit of the visible Universe, galaxies can move away from us faster than the speed of light. However, they are not moving faster than the speed of light compared to the space where they are. What is going on is that space and time are stretching fast due to the expansion of the Universe.

Another objection might be that light can move slower than c = 299,792,458 through transparent materials such as glass and water. So, how can the claim that all massless particles must always move at exactly the speed of light in vacuum be true? The answer to that is that the light particles (photons) in those materials are being absorbed and re-emitted as new photons by the atoms. However, in between the atoms the photons move exactly at the speed c = 299,792,458, or more correctly at the time-space conversion factor c = 299,792,458.

From left to right, an atom absorbs a photon, which excites an electron that jumps into a higher orbit. Then it emits a photon and the electron falls back to the ground state again. — From ground state to excited state, absorption and emission of a photon in an atom. Shutterstock asset id: 2180385419 by rktz.

All Matter Consist of Molecules and Atoms that move

But wait, we are not done. Another fact is that everything is made of atoms and molecules that are never completely still. Temperature is a measure of their average kinetic energy (energy of motion). Even at the temperature absolute zero molecules and atoms are still moving. Yes, even at the lowest possible temperature they are still moving. It is impossible for atoms and molecules to stand completely still, just like children.

A vibrating protein molecule. — Thermal vibration of a segment of a protein’s alpha helix. Its amplitude increases with temperature. User:Greg_L on English wikipedia, uploaded to commons by User:Frokor, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons.

Other Super Facts Related to Relative Motion

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Pulsars the Cosmic Lighthouses

Super fact 108 : A Pulsar is a rapidly rotating neutron star that emits beams of electromagnetic radiation from its magnetic poles. The radioactive beam from a pulsar that is located where the sun is located would heat earth’s surface to tens of thousands of degrees. The pulsar may rotate hundreds of times per second, and we only detect the beam when it crosses our line of sight. A neutron star, or a pulsar, is vastly denser than the Sun, typically hundreds of trillions of times denser.

As mentioned, a pulsar is a rapidly rotating neutron star that emits beams of radiation from its magnetic poles. A neutron star is an ultra-dense remnant left behind when a massive supergiant star runs out of fuel and collapses. You can read more about neutron stars in my post here and you can read about neutron stars that act like super magnets called magnetars here. This web page feature a calculation of what the intensity of a pulsar beam would be if it hit Earth and the pulsar is located where the sun is.

A blue pulsars / neutron star directs a beam toward earth and burns the surface. — The beam from a pulsar hits earth causing destruction. This is an AI picture generated by me and ChatGPT.

I consider this a super fact because pulsars are a very extreme type of star, which existence I believe comes as a surprise to many people.

Blue neutron star on black background with two bright blue beams. Compact supermassive object. | Pulsars the Cosmic Lighthouses — Pulsar with energetic jets in space. Shutterstock asset id: 2697475389 by Nazarii_Neshcherenskyi

Below is a one and a half minute NASA video explaining what a pulsar is. It is taken from this website.

Different Types of Neutron Stars and Different types of Pulsars

At top there is some text stating “A neutron star is a dense core left behind after a massive star goes supernova and explodes. Though only about 10 to 20 miles (15 to 30 kilometers) wide, they can have three times the mass of our Sun, making them some of the densest objects in the universe, second only to black holes. A teaspoon of neutron star material would weigh 4 billion tons on Earth. There are several types of neutron stars.” : Below the text at the top there is a picture of a magnetar, a pulsar and a magnetar plus pulsar. The text for each picture says: Magnetar - A magnetar is a neutron star with a particularly strong magnetic field, about 1,000 times stronger than a normal neutron star. That's about a trillion times stronger than a normal neutron star. That's about a trillion times stronger than Earth's magnetic field and about 100 million times stronger than the most powerful magnets ever made by humans. Scientists have only discovered about 30 magnetars so far. Pulsar - Most of the roughly 3,000 known neutron stars are pulsars, which emit twin beams of radiation from their magnetic poles. Those poles may not be precisely aligned with the neutron star's rotation axis, so as the neutron star spins, the beams sweep across the sky, like beams from a lighthouse. To observers on Earth, this can make it look as though the pulsar's light is pulsing on and off. Magnetar + Pulsar – there are about six known neutron stars that are both pulsars and magnetars. — Courtesy NASA/JPL-Caltech, Attribution, via Wikimedia Commons

Neutron stars are extreme stars. They are small super dense stars with extreme gravitational fields. They are in a sense like a gigantic atomic nucleus. Perhaps it is not surprising that they are extreme in other ways as well. There are pulsars, neutron stars which emit twin beams of radiation from their magnetic poles. Those poles may not be precisely aligned with the neutron star’s rotation axis, so as the neutron star spins, the beams sweep across the sky, like beams from a lighthouse. To observers on Earth, this can make it look as though the pulsar’s light is pulsing on and off.

There are different types of pulsars. Some spin extremely fast. They rotate hundreds of times per second, even 700 times per second. They are called Millisecond Pulsars. There are pulsars that emit beams of radio waves and pulsars that emit only gamma rays. A black widow pulsar a star system consisting of a rapidly spinning pulsar and a companion star that is being consumed by the pulsar like a black widow spider eats its mate. This link feature animation videos from NASA showing a star being consumed by a black widow pulsar.

Finally, there are magnetars, neutron stars with extremely powerful magnetic fields trillions and quadrillion times stronger than Earth’s magnetic field at the surface. You can read about them here.

Other extreme Celestial objects

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The Second Law of Thermodynamics Does Not Contradict Evolution

Super fact 73 : The second law of thermodynamics, or the fact that entropy is always increasing in an isolated system does not contradict evolution. Life is not a closed system. The environment is providing energy, the sun is providing energy, geological forces are providing energy, etc.

A lot of people have never heard of the second law of thermodynamics, or entropy and are unaware of the claim that the second law of thermodynamics contradicts evolution. So how can debunking this claim be surprising, and a super fact? The reason is that this is a popular claim among creationists and according to this Gallup poll 40% of Americans believe in creationism. The fact that this popular but false claim is rooted in a very basic misunderstanding of the second law of thermodynamics and what entropy is makes it super fact.

In the past I’ve read many creationist books that make the claim that the second law of thermodynamics contradicts evolution. One of them was Scientific Creationism (1985) by Henry M. Morris (the father of modern creation science), where he stated that the second law of thermodynamics says that everything tends towards disorder, making evolutionary development (ordering) impossible. The Death of Evolution: Restoring Faith and Wonder in a World of Doubt by Jim Nelson Black, another book I read, and which I gave a one star review on Amazon, makes the same claim. I’ve also come across a lot of people making this claim.

The people who make the claim that the Second Law of Thermodynamics contradict evolution typically do not understand the second law of thermodynamics and do not know what entropy is. Despite that fact they see it as a powerful argument against evolution. I’ve even seen it used against highly respected physics professors who “believe in”, well accept the reality of evolution, by people who had no understanding of the second law of thermodynamics. At one point I even believed the claim myself. Then I studied physics, and well, oops, I was forced to admit that I had been bamboozled.

The Second Law of Thermodynamics

The Second Law of Thermodynamics states that the total entropy (disorder) of an isolated system always increases over time. This means that natural processes tend to move from order to disorder (within the isolated system). It should be noted that disorder is a popular but imperfect metaphor for entropy. Entropy is not the same thing as what people think of as disorder. In physics entropy refers to the logarithm of the number of microstates compatible with the system’s measurable macroscopic state. As molecules randomly arrange themselves into new macroscopic states, the number of possible microstates will increase.

It also means that heat will spontaneously flow from hotter to colder objects, but never the reverse. Another thing it means is that mechanical energy can be converted to thermal energy, but never the reverse. It turns out that those seemingly different statements are physically identical.

Second law of thermodynamics. S corresponds to entropy. Ludwig Boltzman’s formula from 1874 — Second law of thermodynamics. S corresponds to entropy. Shutter Stock Vector ID: 2342031619 by Sasha701

It is very possible that the entropy of an organism is lower compared to a blob corresponding to all its molecules randomly distributed within a blob. However, that organism did not evolve in isolation inside a hermetically enclosed box without any energy from the outside. Life and evolution operate in an environment full of energy coming from the sun, the Earth, winds, oceans, geological forces, radiation, etc. Evolution does not take place in an isolated system.

It is also important to understand that within an isolated system, pockets of lower entropy can form if they are offset by increased entropy elsewhere within the system. That’s what the word “total” in total entropy means. Crystal formation is an example of creating local pockets of lower entropy (less “disorder”) within a system, but this is always accompanied by a greater increase in entropy in the surroundings. The Universe is an isolated system so the entropy within the Universe should always increase, but again the local pockets of lower entropy that evolution may create are accompanied by a greater increase of entropy elsewhere.

Crystal structure. This is model of a unique arrangement of atoms in a crystal. — Atoms in a crystal. The crystal represents a pocket of lower entropy. As this pocket of lower entropy forms there is equal of greater increase in entropy in the surroundings. What is true for the crystal is true for the molecules in living beings. Neither the formation of crystals nor the evolution of life contradicts the second law of thermodynamics. Asset id: 689181712 by BK_graphic.

Below is a YouTube video explaining how the second law of thermodynamics does not contradict evolution.

Entropy – Arrow of time

An interesting aspect of the second law of thermodynamics is that it makes entropy serve as an arrow of time. In general, the fundamental laws of physics are time reversible. The equations work the same forwards and backward in time. The equations for gravity, electromagnetism, and the strong nuclear force work the same regardless of time’s direction. An example is if you filmed a planet orbiting a star and played it backward, it would still follow the laws of motion the same way.

Throw a bunch of billiard balls on the floor and film them bouncing and hitting each other and the walls. If you then run the film backwards and forwards it would be far from obvious which is forward and which is backwards, except for the fact that the balls will slow down due to friction. However, balls slowing down due to friction is mechanical energy turning into heat, which is an example of the second law of thermodynamics. The fundamental laws of physics are time reversible, but the second law of thermodynamics is a notable exception. Entropy always increases in an isolated system (like the Universe). By measuring entropy, you can distinguish the past from the future, giving time a direction

Another evolution related post is: Evolution is a fact