Blogging – Page 16 – Super Facts

Every Symmetry is Associated with a Conservation Law

Super fact 36: Every continuous symmetry of the action of a physical system with conservative forces has a corresponding conservation law. This revolutionary insight was mathematically proven in 1915 by a relatively unknown woman, Emily Noether.

It is not easy to understand what this super fact means, and therefore it is easy to miss the fact it says something fundamental about the nature of reality. It says something profound about our Universe and all possible Universes. It is arguably one of the most profound discoveries in science. Since the discovery of Noeth e r theorem, we do physics differently and we view our physical reality differently.

In the book “The Theory of Almost Everything” the author, theoretical physicist Robert Oerter states that the standard model of elementary particles, or most of modern physics, rests on three pillars, special relativity, quantum physics, and Noether’s theorem. Which one of those three have you not heard of? I guess Noether’s theorem.

That question brings me to the second part of the super fact. Emily Noether did a lot for mathematics and physics in addition to her first theorem (stated above), and yet she is not well known. Albert Einstein said of Emily Noether : “Fräulein Noether was the most significant creative mathematical genius thus far produced since the higher education of women began”. Notice he didn’t say “woman genius”.

Why I consider Noether’s (first) theorem a super fact is because it tells us something fundamental about reality that is highly surprising and yet undisputable (mathematically proven) and not many of us know about it. The second part of the super fact, that despite being one of the greatest geniuses of the 20th century she is so unknown, is also surprising.

A young woman in Victorian clothing sitting at a small table. — This picture reminded me of Emily Noether a genius and one of the greatest mathematicians in human history. This is a submission for Kevin’s No Theme Thursday.

Noether’s Theorem What Does It Mean

Noether’s theorem, says that symmetries in the universe give rise to mathematical conservation laws. One way to understand this is by using an example. That the physical laws remain the same as you translate a system in time is an example of a continuous symmetry.

If you do an experiment twice at two different times, let’s say at 8:00AM and at 9:00AM, and everything is set perfectly identical both times you are likely to get the same result. Well barring statistical/quantum uncertainty. The point is that the physical laws did not change. If the physical laws do not change between 8:00AM and 9:00AM, then you have a continuous symmetry.

Noether’s theorem says that if you have a continuous symmetry, you also have a conservation law, and the conservation law in this case is the conservation of energy/mass. If the physical laws do not change between 8:00AM and 9:00AM then mathematically the total energy / mass of the closed system must remain constant.

It follows that energy is not destroyed or increased. At first it seems like the time symmetry and energy/mass conservation have nothing to do with each other, but the symmetry gives rise to the conservation law. So, if you ask the question, why is energy / mass conserved, the answer is because physical laws don’t change with time.

There are many symmetry-conservation law pairs in nature. Translational symmetry, the fact that the laws of physics stay the same if you move to the side or forward, results in the conservation of momentum. The symmetry of laws that does not change if moving around in a circle amount to the law of conservation of angular momentum. Other symmetries result in the conservation of charge.

The converse is also true. If you find that a quantity is conserved you can find a symmetry, and if you find a symmetry that is broken you can find a quantity that is not conserved after all. There is not much in science that is more fundamental than that and in addition Noether’s theorem is very useful.

The picture illustrates the collision of two balls. It features mathematics demonstrating that linear momentum (mass times velocity) is preserved | Every Symmetry is Associated with a Conservation Law — If the physical laws stay the same when translated in space then linear momentum is conserved. Conservation of momentum principle in isolated system Asset id: 2319593529 by MZinchenko.

Emily Noether

Emily Noether was born into a Jewish family in Germany March 23 in 1882. She was the daughter of the mathematician Max Noether. She studied mathematics and completed her doctorate in 1907. At the time, women were largely excluded from academic positions, but she worked at the Mathematical Institute of Erlangen without pay for seven years. She eventually gained paid positions. She made huge contributions to abstract algebra, calculus of variations, topology and other mathematical fields.

Her most important contributions are the Noether’s theorems, the first one described here. When Hitler came to power in 1933, she had to flee Germany. She got a position as a professor at Bryn Mawr in 1933. She died in 1935.

Black and white photo of Emily Noether wearing a white shirt, a darker skirt and a black bowtie. — Emily Noether in 1910. Unknown author Unknown author Publisher: Mathematical Association of America [3], Brooklyn Museum [4], Agnes Scott College [5], [6], Public domain, via Wikimedia Commons.

Concluding Summary

Noether’s Theorem changes how we view the Universe and the laws of physics. For example, the conservation of energy is not just something we empirically discovered. It follows mathematically from physical laws not changing by time. It represents a paradigm shift in science that arguably is as important as quantum mechanics or relativity and yet very few people have heard of it. I find that quite shocking.

To see the other Super Facts click here

Natural Disasters Kill Less People Now Than 100 Years Ago

Super fact 35: Natural disasters kill a lot less people now compared to 100 years ago. That is despite a larger population and despite the fact that climate change has increased the frequency and intensity of many types of natural disasters.

This is a super fact because surveys, such as this questionnaire from Gap Minder, show that the vast majority of the public (90%) believe that deaths from natural disasters have increased or stayed the same. Gap Minder is a Swedish highly respected non-profit founded by Hans Rosling that promotes increased use and understanding of statistics. Our World in Data (OWID), a renowned scientific online publication focusing on large global problems largely took its inspiration for Gap Minder and Hans Rosling.

The reason for the fewer deaths from natural disasters is not that there are fewer natural disasters, on the contrary, it is because we are now much better at predicting, handling and recovering from natural disasters. Our warnings systems, rescue systems and healthcare have improved significantly.

The graphics in this article from BBC show that the frequency of natural disasters has increased, and that the cost of natural disasters has increased, and yet the number of deaths has decreased.

The graph below comes from the Gap Minder article. It shows the annual deaths from natural disasters in ten-year intervals starting with 1930. In the 1930’s there were 971 thousand deaths per year from natural disasters and during the period 2010 to 2016 there were 72 thousand deaths per year from natural disasters, an improvement by more than 13 times.

However, it should be noted that there was a huge flood in China 1931 causing an estimated 3 million deaths, and it skews the numbers for the 1930’s interval.

Originally, I set the headline for this super fact to be “10 Times more people died from natural disasters a hundred years ago” but I changed it to “Natural Disasters Kill Less People Now Than 100 Years Ago” because I realized that the 1930’s peak is an outlier because of the 1931 flood. I don’t want my headlines to be click bait.

The graph shows 300 to 400 thousand annual deaths at the beginning of the 20th century, then 971 thousand annual deaths in the 1930’s, then it continuously gets lower until the annual deaths in the 2010 to 2016 period is 72 thousand deaths per year | Natural Disasters Kill Less People Now Than 100 Years Ago — This graph from the Gap Minder article shows the annual deaths from natural disasters in ten-year intervals starting with 1930. The trend is down.

This does not mean that we should not worry about the increase in frequency and intensity of natural disasters from climate change. First of all, there are no warning systems and healthcare available for Koalas and Elephants, secondly cost matters, and thirdly there is no guarantee that we can keep improving our ability of predicting, handling and recovering from natural disasters enough to match the accelerating risks for natural disasters.

What People Believe Regarding Disaster Deaths

The Gap Minder article above report on a question survey conducted by Gap Minder. They asked large groups of people in 14 countries the following multiple-choice question “How did the number of deaths per year from natural disasters change over the last hundred years?” The choices were:

A. More than doubled
B. Remained more or less the same
C. Decreased to less than half

Most people answered A, a lot

of people answered B, but only 10% got the correct answer C, decreased to less than half. In other words, if chimpanzees had answered this question by randomly picking an answer, they would have done better than people. This is why I consider this a super fact. Below is a graphics taken from the Gap Minder article that shows how people in different countries responded.

There are 16 bars divided into three colors, green for the correct answer – “decreased to less than half”, orange for “remained more or less the same”, and red for “more than doubled”. The 16 bars correspond to 14 countries, one for the average (10%), and one for random answers by chimpanzees (all 33.3%). The 14 countries are Finland, Norway, Japan, Sweden, UK, Australia, US, Spain, Canada, South Korea, Germany, Belgium, Hungary, and France | Natural Disasters Kill Less People Now Than 100 Years Ago — The histogram graphics above show the answers to the question “How did the number of deaths per year from natural disasters change over the last hundred years?” The correct answer “decreased to less than half” (in green) was rarely picked. The graphics is taken from the Gap Minder article mentioned.

EF3 Tornado in Dallas

In October 2019 an EF3 tornado ripped through our neighborhood. It left a 2-3 miles long trail of destruction. Roofs were lifted off houses, cars and buses were flown around, hundreds of houses were destroyed, bricks were flying around in the wind, trees were uprooted, and tree branches were flying around, and pieces of concrete crashed into buildings and hit steel fences so forcefully that it bent even quarter inch thick steel fences.

Unlike many of our neighbor’s houses, our house stood, but our chimney was smashed by a piece of concrete coming off a neighbor’s house, we had to replace our roof, our garage door, the wiring in the attic, our fence and my grill flew around in the yard. The amazing thing was that no one in the neighborhood died.

Why did no one die? Was it maybe because no one was outside walking the dog, or driving around, because everyone had received the alarm on their mobile phone about the approaching tornado and was therefore sheltering inside in a safe place? Imagine the same thing happening in the 1930’s.

Below are a few photos from that day and here are two links with more photos, link-1 , link-2. On the five-year anniversary of this event NBC news interviewed me about this event. To see the interview click here . My interview is at one minute and ten seconds.

A neighbor’s house with the roof ripped off after the EF3 Tornado in Texas. — NBC used this photo. A neighbor’s house the morning of October 21^st, 2019. Again, click on the image, or here, to see the interview. My interview is at one minute and ten seconds.

The photo shows a severely damaged house and lots of debris consisting of wood and trees and tree branches after the EF3 Tornado in Texas. — Another neighbor’s house. This house was about 100 yards from our house. It took a direct hit from the tornado.

This photo shows a house that is completely destroyed after the EF3 Tornado in Texas | Natural Disasters Kill Less People Now Than 100 Years Ago — Another house in our neighborhood.

My wife Claudia asked me to go check on her parents. I drove about 50-100 yards when a neighbor’s roof lying across the road stopped me. I turned around but this time I was stopped by a large pile of trees lying across the street. So, I started walking, but this time I was stopped by a group of firemen telling me that it was too dangerous to be outside. They told me to go back home, and I did. The next day we were able to visit her parents and below is what we saw.

The photo shows my wife Claudia walking into a house with debris everywhere after the EF3 Tornado in Texas. — Inside my wife Claudia’s parents’ house. This was the morning after. In the photo we are walking into their house to check on them (that’s my wife).

To see the other Super Facts click here

Scientists Agree that Global Warming is happening and that we are the Cause

Super fact 34: Climate Scientists agree that Global Warming or if you call it Climate Change is happening, and that it is caused by us primarily because of our burning of fossil fuels. There is a long-standing scientific consensus on these two facts because the evidence is conclusive. Typically, studies show an agreement of at least 97% or 98% among climate scientists.

This is a super fact because surveys show that this is not what the public believes and yet it is true. The public incorrectly believes that there is a large disagreement among scientists on this topic. A note, to understand why the evidence is conclusive as to why global warming is happening and is caused by us click here.

Note : I will use the term “global warming” in this review. Whether you call the phenomenon climate change, climate disruption, or global heating, is not important.

The Scientific Consensus

This extensive survey from 2013 of 12,000 climate papers (papers published over two decades) by Dana Nuccitelli and Cook, etc., concluded that 97.1% of climate scientists endorsed the consensus position that humans are causing global warming.

They also did a science author self-rating which concluded that 97.2% of climate scientists endorsed the consensus position that humans are causing global warming. Another conclusion from the survey was that the consensus had increased from around 90%, perhaps less, in the early 1990’s.

A later review of six independent, peer-reviewed studies examining the scientific consensus about global warming have concluded that between 90% and 100% of climate scientists are convinced human-caused global warming is happening. A more recent study (2021) found that as many as 98% of climate scientists are convinced global warming is happening and is human-caused. Numerous other surveys have concluded the same thing.

People’s Beliefs About Global Warming

This 2024 survey from Yale University show that most Americans (61%) understand that global warming is mostly human caused. By contrast, 28% think it is caused mostly by natural changes in the environment. Most Americans (58%) <<Link-6>> understand that most scientists think global warming is happening. This percentage has trended generally upward since this survey began in 2008. By contrast, about one in five (22%) think there is a lot of disagreement among scientists about whether global warming is happening.

The green graph is going up slightly starting from 46% in 2009 and ending in 58% in 2023. The black graph starts at 33% in 2009 and ends in 22% in 2023. The yellow graph starts at 2% in 2009 and ends in 2% in 2023 | Scientists Agree that Global Warming is happening and that we are the Cause — The green graph corresponds to “most scientists think global warming is happening (%).” The black graph corresponds to “there is a lot of disagreement among scientists (%)”. The yellow graph corresponds to “Most scientists think global warming is NOT happening (%)”. Graph taken from the Yale Program on Climate Change Communication.

However, only one in five Americans (20%) understand that nearly all climate scientists (more than 90%) think that human-caused global warming is happening. The aforementioned Dana Nuccitelli refers to this in his book Climatology versus Pseudoscience as the consensus gap. Again, this large discrepancy between public perception and reality makes the consensus gap a super fact. Research has shown that this discrepancy has a large impact on people’s other beliefs regarding global warming.

This is bar graph. It shows that 2% believe the answer is 0-10%, 2% believe the answer is 11-20%, 3% believe the answer is 21-30%, 3% believe the answer is 31-40%, 8% believe the answer is 41-50%, 7% believe the answer is 51-60%, 7% believe the answer is 61-70%, 13% believe the answer is 71-80%, 13% believe the answer is 81-90%, 20% believe the answer is 91-100%, 22% don’t know | Scientists Agree that Global Warming is happening and that we are the Cause — The question was, To the best of your knowledge what percentage of climate scientists think that human-caused global warming is happening? Graph taken from the Yale Program on Climate Change Communication.

Why is there a Consensus Gap?

In his book Climatology versus Pseudoscience Dana Nuccitelli explains that a relatively small group of so-called climate skeptics, or more accurately called climate contrarians have received a lot of attention from media. Even though their science is bad, and they’ve published their error ridden papers in obscure or discredited journals, and the fact that their predictions have failed repeatedly many times over, they have had an enormous influence on public discourse. Conservative politicians, and many talk show hosts are blindly devoted to their falsehoods, whilst real scientists are being attacked.

It is not just rightwing media who are using them for their purposes, but mainstream media are giving the contrarians undue attention as well. Sensationalism is one issue. A science contrarian claiming that all the climate scientists are wrong, and that he is the only one who finally got it right is a lot more interesting of a story than a repeat of the consensus. Another issue is false balance. Journalist should not feel that they must give equal time to evidence-based science and nonsense, but that is often the case. To read my review of this book click here.

The Oregon Petition

I am mentioning the Oregon petition because I fell for it myself. The Oregon petition was an official looking petition circulated by climate contrarians, claiming that there is no evidence that human-caused global warming will cause catastrophic heating of earth’s atmosphere and disruption of earth’s climate, and that adding more carbon dioxide to the atmosphere would even be beneficial for plants and animals. It got an impressive number of signatures, 32,000 after some years.

However, it turned out that the signatories rarely had climate expertise, and were not scientists, and the survey listed many falsified names such as the names of the Spice Girls and several fictional characters. Less than 200 of the signatories were climate researchers.

It was a con, but it was touted in a lot of media as the truth. I saw it over and over and I believed it. I was later surprised to learn that it was a con and that a scientific consensus existed on global warming / climate change. Learning that I had been bamboozled on this matter was one of the red flags that prompted me to start doing some fact checking on the issue global warming.

To see the other Super Facts click here

Quick Easy Introduction to Astrophysics

The goal of this blog is to create a list of what I call super facts. Important facts that are known to be true and yet they are surprising, shocking or disputed among non-experts. In a sense it is myth busting. However, it is not the only type of posts I do. This is a review for a popular book on Astrophysics called “Astrophysics for People in a Hurry” by Neil De Grasse Tyson. It is a New York Times best seller and the #1 best seller in Astronomy & Astrophysics on Amazon. It has almost 37,000 ratings/reviews on Amazon and more 194,000 reviews/ratings on Goodreads.

Below is a list of the four formats in which it comes on Amazon.

Hardcover – Publisher : W. W. Norton & Company; First Edition (May 2, 2017), ASIN : 0393609391, ISBN-10 : 9780393609394, ISBN-13 : 978-0393609394, 224 pages, item weight : 2.31 pounds, dimensions : ‎ 7.3 x 4.8 x 0.9 inches, it costs $6.21 – $13.26 on US Amazon. Click here to order it from Amazon.com.
Kindle – Publisher – W. W. Norton & Company (May 2, 2017), ASIN : B01MAWT2MO, 222 pages, it costs $9.00 on US Amazon. Click here to order it from Amazon.com.
Audiobook – Publisher : Blackstone Audio Inc (May 2, 2017), ASIN : B06XB2PX7G, it costs $10.20 on US Amazon. Click here to order it from Amazon.com.
Audio CD – Publisher : Blackstone Publishing; Unabridged edition (May 2, 2017), ISBN-10 : 1538408015, ISBN-13 : 978-1538408018, it costs $24.95 on US Amazon. Click here to order it from Amazon.com.

“Astrophysics for People in a Hurry” by Neil De Grasse Tyson front cover | Quick Easy Introduction to Astrophysics — Front cover of the book Astrophysics for People in a Hurry. Click on the image to go to the Amazon page for the hardcover version of the book.

Amazon’s Description of Astrophysics for People in a Hurry

Over a year on the New York Times bestseller list and more than a million copies sold.

The essential universe, from our most celebrated and beloved astrophysicist.

What is the nature of space and time? How do we fit within the universe? How does the universe fit within us? There’s no better guide through these mind-expanding questions than acclaimed astrophysicist and best-selling author Neil deGrasse Tyson.

But today, few of us have time to contemplate the cosmos. So Tyson brings the universe down to Earth succinctly and clearly, with sparkling wit, in tasty chapters consumable anytime and anywhere in your busy day.

While you wait for your morning coffee to brew, for the bus, the train, or a plane to arrive, Astrophysics for People in a Hurry will reveal just what you need to be fluent and ready for the next cosmic headlines: from the Big Bang to black holes, from quarks to quantum mechanics, and from the search for planets to the search for life in the universe.

This is my four-star review for Astrophysics for People in a Hurry

The reason I gave the book four stars instead of five is because I felt that if you have an interest in the topic, you will have heard it all before. However, in retrospect that might not be a good reason to deduct a star. After all, the book seems to be targeting people who do not know much about the subject and thus will not have heard it all before.

Quick and Entertaining Overview of Astrophysics

I’ve read a number of Neil DeGrasse Tyson’s books and I love them. This book is a compressed version of what he has been explaining in other books. If you’ve already read a number of Neil De Grasse books, or perhaps other popular science Astrophysics books such as those by Stephen Hawking, you will not find much new in this book. However, I think it is a brief but good summary of Astrophysics written for a layman. It is 208 pages, each page having about half as much text per page as a typical popular science book. It is an easy and fairly quick read.

He briefly explains the Big Bang, physical laws, spectra, nebulae, the speed of light, very briefly relativity and quantum physics, the cosmic background radiation, galaxies, gravitational lensing, dark matter, dark energy, neutron stars, the composition of the solar system and exoplanets. He covers a lot of ground quickly and he makes it easy to understand without simplifying so much that it becomes misleading. This book is exactly what the title says. However, as I mentioned, if you’ve read a lot on the topic already, especially if it is Neil DeGrasse Tyson’s books, you’ve seen it before. I still think it was very enjoyable though and I still learned something new. He is a very entertaining author.

“Astrophysics for People in a Hurry” by Neil De Grasse Tyson back cover — Front cover of the book Astrophysics for People in a Hurry. Click on the image to go to the Amazon page for the hardcover version of the book.

To see the Super Facts click here

Marsupial Planet

Image above by Kevin from The Beginning at Last

There Are Three Types of Mammals

Placentals, Monotremes, and Marsupials

All mammals are warm-blooded, have fur, and produce milk. However, there are three main types of mammals, placentals, monotremes, and marsupials, distinguished by how they give birth. Placentals give birth to well-developed young, and they nourish their young in the uterus through the placenta. Examples include gorillas, humans, whales, rodents, tigers, and bats. Monotremes lay soft-shelled eggs. Examples include the platypus and the echidna.

Then we have Marsupials, which give birth to small and underdeveloped young. Most female marsupials have pouches. Examples include kangaroos, wallabies, wombats, possum, opossum, Tasmanian devils, and koalas. Below is a kid friendly overview of the three types of mammals.

Marsupials on Three Continents

Close to 70% of the 334 extant marsupial species are concentrated on the Australian continent, including mainland Australia, Tasmania, New Guinea, and nearby islands. The remaining 30% are distributed across the Americas, primarily in South America. The Virginia opossum is the only marsupial native to the United States, but it is quite common. For example, we have lots of them in our neighborhood in Dallas. It should also be noted that there are a lot of marsupial fossils in Antarctica, which means that marsupials once lived there.

The image shows the distribution of marsupials being Australia, south America and parts of North America. — This map shows the distribution of marsupials. Blue indicates places in which marsupials are native and purple where they have been introduced. The image is from Wikipedia commons created by Michal Klajban under https://creativecommons.org/licenses/by/4.0/.

DNA evidence supports a South American origin for marsupials, with Australian marsupials arising from a single Gondwanan migration of marsupials from South America, across Antarctica, to Australia. These continents were connected and part of the supercontinent Gondwana back then. The ancestors of the marsupials, the metatherians split from placentals around 100 million to 120 million years ago during dinosaur times.

Bamboozled by an Opossum

We’ve found opossums in our house, behind our laundry machine. We’ve seen them along the street, on lawns in the neighborhood and we’ve seen them climb trees. They are pretty common in our neighborhood. It should be noted that they are not possums even though they are sometimes called that. Possums is an Australian relative to the Opossum.

An Opossum sitting on top of a fence looking down at the photographer. — A photo of an Opossum. Author Sergey Yarmolyuk. From Wikimedia commons https://creativecommons.org/licenses/by-sa/4.0/

One day when my wife and I were out walking the dogs we saw an opossum lying on the alleyway behind our house. He looked dead. However, when I checked, he was warm and appeared to be alive even though he was unconscious. We put him in a box containing a soft blanket and took him to the veterinary. We were willing to pay for any treatment or surgeries needed. At the veterinarian he woke up and they later placed him in a nature sanctuary. We did not need to pay anything.

Later on, we learned that when an opossum is threatened or harmed, they will “play possum“. They mimic the appearance and smell of a dead animal. This response is involuntary, like fainting, and not a conscious act. That might have been what was going on. So, I might have been bamboozled by an opossum. Bamboozlement seems to be the story of my life. Luckily, he was a male and the veterinary said it looked like he had been hit by a car, so us taking him to the veterinary probably did not do much harm. However, the “playing possum” thing is something to keep in mind with these animals.

Australia and our Photos of Marsupials

When our kids were young, we traveled to Australia where we encountered a lot of marsupials in the wild, in nature preserves and at zoos We encountered a lot of kangaroos but also wombats, koalas, and Tasmanian Devils. I can add that checking out kangaroos and other marsupials was not the only thing we did in Australia. We also spent a week in Great Barrier Reef where we did snorkel and scuba diving.

The first picture below was from our visit to the Blue Mountains. We stopped to have lunch, and I decided to go and take a leak. As I approached a bush, I heard some noise and when I looked behind the bush, I saw that there was a kangaroo behind it. What you see in the picture below is what I saw. The kangaroo was just two yards away. He seemed to be as startled as I was, and we stared at each other for a few seconds. I had my camera hanging around my neck, so I decided to take a photo. Then he hopped away. I am so glad I did not pee on his lunch.

A kangaroo standing behind a bush munching on foliage while staring into the camera | Marsupial Planet — A surprise encounter with a kangaroo in the wild. I am so glad I did not pee on his lunch.

Our son in a blue shirt and our daughter in a pink rain jacket surrounded by three kangaroos. — Our oldest son and daughter feeding small kangaroos (or wallabies) at a nature preserve outside Brisbane, Australia.

My wife and younger son in yellow rain jackets and our daughter in a pink rain jacket surrounded by three kangaroos that are close up. — Our younger son and daughter feeding small kangaroos at a nature preserve outside Brisbane, Australia. They are laughing because one of the kangaroos grabbed the entire bag of food and then spilled it.

The kangaroo is putting his face straight into the camera, very close | Marsupial Planet — A small kangaroo/wallaby is sniffing my camera (at the same nature preserve).

Note : Koalas are often called Koala bears, but they are not bears.

A koala is sitting in a tree branch curled up with its eyelids shut. — A Koala sleeping in a tree at Brisbane Zoo.

Our six-year-old daughter is sitting in a chair and holding a koala. — Our daughter holding a Koala at Brisbane Zoo.

The Tasmanian Devil is behind a fence, and he is looking up to the camera | Marsupial Planet — A Tasmanian Devil at the Brisbane Zoo.

A wombat in a cage eating straw | Marsupial Planet — Wombat at Brisbane Zoo

One interesting fact about Wombats is that they produce cubic shaped poop. This makes the poop stackable, and the wombats use it to mark their territory and attract mates.