Tag: Super Facts

The Pole-Barn Paradox and Solution

Super fact 39 : Relativistic length contraction goes both ways. If two observers are moving compared to each other both will observe the length of the objects in the other’s system to be shorter in the direction of motion. The first observer will think that a yard stick in the second observer’s frame will be shorter whilst the second observer will think that the yard stick in the first observer’s frame is the shorter one.

Assume a pole and a barn are of equal length when both objects are stationary. If the pole is moving (at a high speed) compared to the barn, then the pole will be shorter than the barn from the barn’s perspective but longer than the barn from the pole’s perspective. Does the pole fit inside the barn or not? This is referred to as the pole-barn paradox, or the barn-door paradox, or the ladder paradox (if a ladder is used instead of a pole).

I call this conundrum a super fact because whilst most people have heard of relativistic time dilation and perhaps length contraction, the fact that it goes both ways comes as a surprising head scratcher. The situation is analogous to my super fact post “Time Dilation Goes Both Ways” where I state:

Super fact 38 : If two observers are moving compared to each other both will observe the other’s time as being slower. In other words, both observers will observe the other’s clocks as ticking slower. Time slowing down is referred to as Time Dilation. And this post is about how time dilation goes both ways.

Both the time dilation paradox and the pole-barn paradox are solved by the non-simultaneity in relativity. However, the pole-barn paradox is more concrete and perhaps more in your face. You can easily imagine the problematic paradox.

A picture of a girl, Amy who is speeding past a man, Alan and his barn. Amy has a pole. The pole is contracted along the direction of motion from Alan’s perspective and the barn is shorter along the direction of motion from Amy’s perspective | The Pole-Barn Paradox and Solution
Amy is speeding past Alan and his barn at a high speed. Amy has a pole. Because of the high-speed Amy’s pole appears shortened and will easily fit in Alan’s barn. However, to Amy it is Alan’s barn that is contracted, and her pole has the normal length and will therefore not fit in Alan’s barn.

Postulates of Special Relativity

The two postulates of special relativity are:

  • The laws of physics are the same in all inertial frames of reference. An inertial frame is a system that moves at a constant velocity.
  • The speed of light in a vacuum is constant for all observers, regardless of the motion of the light source.

The first postulate is called the principle of relativity and goes all the way back to Galileo Galilei. It means that no experiment can determine whether you are at rest or moving at a constant velocity. The reciprocity of length contraction follows from this postulate. If the length of the pole in the example above is half as long as the barn in both the barn frame and the pole frame then you could tell who was standing still and who was moving from that fact, and that violates the first postulate. The first postulate demands that if the pole is half as long in the barn frame and that the barn is half as long in the pole frame.

The second postulate is the more shocking one and is special to relativity. It was discovered experimentally at the end of the 19th century but was too difficult for scientists to accept at first so various ad hoc explanations were put forth to explain it away, until the theories of relativity were created. I designated this postulate as my super fact #4 and you can read about it here.

Length Contraction

Time dilation means that a time interval between two events in a certain frame is longer by a factor B in a frame moving relative to the first frame (see picture below). Let’s imagine Amy moving at the speed v compared to Alan and his barn. Amy passes the left side of the barn at a certain time and soon after the right side. The time difference from Alan’s perspective is T and the width of the barn is L, so L = vT. From Amy’s perspective the time difference is T’ and width of the barn L’ and L’ = vT’. We denote Amy’s measurements with a prime. Note the velocity must be the same in both systems. However, Amy’s clock ticks slower (from Alan’s perspective) so T’ = BT or T = T’/B (time dilation). So, L’ = vT’ = vT/B = L/B.

If the derivation of the formulas above is confusing to you, ignore the math, and just remember that Alan measures a shorter time for the passing of the pole (because Amy’s clock is slower) from his perspective and therefore the pole must be shorter as measured from his system. If Alan measures two seconds for the passing of the pole than Amy measures maybe four seconds. It is Amy’s pole, so her longer measurement corresponds to the proper length of the pole whilst Alan’s measurement is the contracted length. Note the length contraction can only happen along the direction of motion, not perpendicular to it. To read more about length contraction click here.

This picture shows the formula for time dilation, the expression for the beta factor, and the formula for length contraction | The Pole-Barn Paradox and Solution
The beta factor used in the formula for time dilation as well as length contraction.

Solution to the Pole-Barn Paradox

So, Amy’s pole cannot fit in Alan’s barn. The pole is moving fast so it must move in and out of the barn. Now let’s create the paradox. Imagine the barn having doors on each side that open for the moving pole and then close for a moment to entrap the pole and then they open as the pole leaves the barn. Here is the paradox, if they open and close at the same time, than the pole can be inside the barn (entrapped) from Alan’s perspective but not from Amy’s perspective. From Amy’s perspective the pole does not fit.

However, the solution to the paradox lies in “open and close at the same time”. If the doors open and close at the same time from Alan’s perspective, then they don’t open and close at the same time from Amy’s perspective.

From Amy’s perspective the door on the left side will open first and let the pole in and then after that the right door will open. After the pole has fully entered the barn and some of it is sticking out on the right-hand side then the left door will close but the door on the right will remain open  until the pole is entirely outside. Relativistic non-simultaneity solves the paradox.

A picture of a girl, Amy who is speeding past a man, Alan and his barn. Amy has a pole. The pole is contracted along the direction of motion from Alan’s perspective and the barn is shorter along the direction of motion from Amy’s perspective. There are two doors on each side of the barn. In Amy’s world the left door is open letting the pole into the barn, whilst the right door is closed. In Alan’s world both doors are close thus enclosing his shorter pole.
In Alan’s frame the doors can be closed at the same time and enclose Amy’s pole. In Amy’s frame the doors open and close to let the pole through but they don’t open and close at the same time.

Finally, below is a YouTube video that explains and solves the pole-barn / barn-door / ladder paradox simply and efficiently in a little over two minutes.

Book Recommendations on Relativity

To see the other Super Facts click here

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 Noether 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 21st, 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

Many Popular Environmental Actions Are Ineffective

Super fact 33: Actions such as eating locally, buying organic produce, using paper straws, and recycling can be good for the environment but can also be worse for the environment and these actions often have a much smaller positive impact than alternative rarely considered actions. What are popular actions for the environment is often different from what is effective.

I consider this a super fact because the beliefs regarding what is good for the environment and what is bad for the environment and what has a significant impact and what has not, are often based on popular trends and culture rather than knowledge. We need to educate ourselves. Following trends is not the answer to good stewardship of the planet.

A big green hand is depicted to symbolize the protection of the environment, where climate-friendly topics are also depicted, such as wind turbines and recycling symbols | Many Popular Environmental Actions Are Ineffective
This content was generated by an Artificial Intelligence (AI) system. Asset id: 2531547331

Is Locally Grown Food Really Better for the Environment?

As I explained in this post eating locally is not necessarily ecological. Agricultural products that are grown off season or in non-native environments are often grown in greenhouses, which require a lot of energy and generate significantly more emissions than shipping the produce across oceans would. This is especially true for crops like tomatoes, cucumbers, mangoes and bananas, that require warmer climates to be grown in open fields.

Red cherry tomatoes | Many Popular Environmental Actions Are Ineffective
From pexels.com by Julia Nagy.

In some cases, the crop requires significant water resources or chemical inputs to thrive and may not be suitable for warmer climates, for example, apples. Some crops, like avocados or almonds require a lot of water but despite that they are grown in dry places like California (80% of California’s freshwater is used for agriculture). From an environmental perspective it would be better to grow these crops in a suitable environment and then transport them.

Is Eating Organic Really Good for the Environment?

As explained in this post eating organic is not necessarily ecological. Despite strong public perception of organic agriculture producing better environmental outcomes, conventional agriculture often performs better on environmental measures including land use, greenhouse gas emissions, and pollution of water bodies. There are, however, some contexts where organic agriculture may be better for the environment.

The graph below gives an overview of the environmental impact of various types of crops grown organically and conventionally. As you can see organic crop often require double as much land compared to conventionally grown crops. It is complicated.

The graph shows the six food groups and their impact across greenhouse gas emissions, land use, eutrophication potential, acidification potential and energy usage | Many Popular Environmental Actions Are Ineffective
Shown is the relative environmental impact of organic and conventional agriculture across various ecological and resource indicators based on a meta-analysis of 164 published life-cycle analyses (LCAs) across 742 agricultural systems. Roughly, lower in the graph means organic is better and higher up in the graph means conventional farming is better. Data source: Clark & Tilman (2017) – Comparative analysis of environmental impacts of agricultural production systems, agricultural input efficiency, and food choice. In Environmental Research Letters. The data visualization is available at OurWorldinData.org<<Link-10>>. There you can find research and more visualizations on this topic. Licensed under CC BY-SA by the authors Hannah Ritchie and Max Roser.

What really matters though is the type of food you eat, not whether it is organic or not. For example, beef (from beef herd) causes emissions 188 times larger than nuts do for the same amount of protein provided. Another thing to note is that if you eat 300 steaks per year you will have a 100 times larger environmental impact from your meat eating compared to someone who eats 3 steaks per year. You don’t have to become a vegetarian to have a smaller environmental impact but quantity matters.

Is Recycling Important?

The common perception that recycling is one of the best things you can do for the environment is not correct. Its impact is often not very large and if not done properly it can be counterproductive. If you throw a greasy pizza box in the recycling, you can ruin the entire batch.

Surveys across 21,000 adults in 30 countries showed that the two actions among twelve that people believed saved the most greenhouse gases were recycling (59%) and upgrading lightbulbs (36%). As it turns out, those two saved the least greenhouse gases among the twelve options. The option saving the most greenhouse gases among the 12 was giving up an SUV, which saved 18 times as much greenhouse gases as recycling. 17% of respondents picked that one.

A filled recycling bag
Photo by Anna Shvets on Pexels.com

According to Our World in Data (and the book Not the End of the World page 114<<Link-6>>), which is based on this research, giving up an average SUV for a sedan would save 3.6 metric ton, or 22.5% of the carbon emissions for the average American. Switching to a plant-based diet would save 2.2 metric ton per person, or 13.8%. Recycling comes in at a savings of 0.2 metric tons according to the same data. EPAs estimates are slightly higher but still low in comparison.

Plastic straws versus paper straws

Producing a plastic straw requires 39 kilojoules of energy and produces 1.5 grams of carbon dioxide emissions. However, producing a paper straw requires 96 kilojoules of energy and produces 4.1 grams of carbon dioxide emissions. So, plastic straws are better for the environment from that perspective. However, this could be compared to a typical passenger vehicle, which emits about 4.6 metric tons of CO2 per year according to EPA. That corresponds to more than 3 million plastic straws and more than one million paper straws.

According to the same article the average passenger vehicle emits about 400 grams of CO2 per mile. So, driving just one mile corresponds to hundreds of plastic straws and paper straws.

Plastic straws
Photo by Christopher on Pexels.com
paper straws
Photo by Sarah Chai on Pexels.com

One advantage of paper straws is that they are easier to recycle, at least under ideal circumstances. Unfortunately, they often get soggy, and recycling plants don’t want that so they often throw them out. Another advantage is that paper straws decompose and don’t end up in our ocean.

However, not only are straws very small items, most of the plastic pollution in the ocean does not come from north America(1%) or Europe (1%). Paper straws versus plastic straws seem like a complex riddle but it may not be an important one. Whether you drive more or drive less is probably a lot more important.

Plastic bags versus paper bags

As with plastic straws versus paper straws plastic bags versus paper bags is a complicated question. From an environmental perspective they both have advantages and disadvantages. Plastic bags are less carbon intensive to produce, are easier to reuse several times, and the production of plastic bags require on average four times less energy than the production of paper bags.

On the other hand, paper bags are decomposable and easier to recycle. However, the chemicals and fertilizers used in producing paper bags create additional harm to the environment. It is a complicated question.

Whale Shark swimming in the ocean about to swallow a plastic bag.
Plastic Ocean pollution. Whale Shark filter feeds in polluted ocean, ingesting plastic. Asset id: 1120768061 by Rich Carey

Having a Significant and Positive Impact on the Environment

Some of the allegedly sustainable practices and actions mentioned above are counter productive and others have a very small effect, for example, carbon emissions savings that are a few grams. According to the “Our World Data” and the book “Not the End of the World” page 114, a compilation of data research, some actions that you can take that will significantly reduce carbon emissions are  (savings in metric tons per year, for flight it is per trip):

  • Giving up an SUV 3.6 tons
  • Go car free (average car) 2.4 tons
  • Switch to plant-based diet 2.2 tons
  • Avoid transatlantic flights 1.6 tons
  • Buy green energy 1.5 tons
  • Switch to electric car (from average sedan) 1.2 tons
  • Switch from electric car to none 1.2 tons
  • Avoid medium flight 0.6 tons (1,700 miles each way going and returning)
  • Laundry in cold water 0.25 tons
  • Hand-dry clothing 0.2 tons
  • Recycle 0.2 tons
  • Upgrade light bulbs 0.1 tons

As you can see in the graphs below, the largest contributor of greenhouse gas emissions in the World and in the United States is electricity and heat. Unfortunately, the composition of the electric grid is something we as consumers have very little control over. We can save energy, get solar panels for our roof, or buy our electricity from green energy companies, but we cannot easily change the composition of the grid. Energy companies and politicians must do that.

However, we can make our voices heard by calling and writing to our representatives. This might be the single most impactful action that you as an individual can take. Your congressman, senator, or state legislator will probably not read your letter. They have hundreds of thousands or millions of constituents and get lots of letters every day. What is likely to happen is that a staff member will skim the letter and note the concern in a database.

Just make sure that your letter is politely written so it does not go in the wastebasket. Also make sure that you are a constituent. Writing to Ted Cruz when you live in Florida is not going to have an impact. They are interested in finding out what the concerns of their constituents are and according to staff members and other information I have come across, this really has an impact.

The largest contributor of greenhouse gas emissions in the World is electricity and then comes Transport. After that comes manufacturing and construction, agriculture, industry, fugitive emissions, buildings, waste, land-use change and forestry, aviation and shipping, other fuel combustion | Many Popular Environmental Actions Are Ineffective
Data source : Climate Watch (2024). Note : Land use emissions can be negative. OurWorldinData.org/co2-and-greenhouse-gas-emissions| CC BY
The largest contributor of greenhouse gas emissions in the US is electricity and heat but it has gone down. Transport is number two. Then comes buildings, manufacturing and construction, fugitive emissions, agriculture, industry, waste, aviation and shipping, other fuel combustion, land-use change and forestry | Many Popular Environmental Actions Are Ineffective
Data source : Climate Watch (2024). Note : Land use emissions can be negative. OurWorldinData.org/co2-and-greenhouse-gas-emissions| CC BY
Conclusion

The survey mentioned above showed that among the twelve environmental actions an individual could take, the one with the second to smallest positive impact was the one that the majority thought had the biggest positive impact, despite it having a relatively tiny impact. The actions that could really make a huge difference were hardly considered.

We, the public, are very bad at determining what is good or bad for the environment and what has a significant and positive impact or not, even though the data is out there and we easily can look it up. Maybe the biggest positive impact one could have on the environment is to look up the facts and get better educated.

To see the other Super Facts click here

Eating Locally is not Necessarily Ecological

Super fact 30: Eating locally is often promoted as an environmentally friendly choice, but that is not always the case.

Whether the food you eat is sustainable and environmentally friendly or not depends on a lot of factors including agricultural methods, whether greenhouse farming or monocropping was used, and whether the crop is natural to its environment. In addition, inefficient local transportation can result in higher emissions than faraway transport by ships and trains. If a crop is grown locally in greenhouses, the extra energy that is needed, and the resulting extra carbon emissions are often much larger than the emissions from the transport.

Cargo ship at sunset. Emissions from the transport of produce is not the main factor for emissions.
Photo by aries nha on Pexels.com

I consider this a super fact because it is often assumed that buying locally is the best choice for the environment. After all, transporting something across the world causes a lot of emissions, right? It turns out not to be that simple.

Articles on Transportation of Food in my French Book

The first time this issue was brought to my attention was in my French class. I am learning French, just as a hobby. There was an article in our French book on the transportation of food around the world “Notre planète ne tourne pas rond!”.

We read that cashews were grown in the Ivory Coast in Africa and then sent for peeling and cleaning in Brazil and then sent to France to be sold. The cashews travelled 10,000 kilometers or 6.250 miles. We read about cod that was caught in Norway then sent to China to be cut into filets and then sent to France to be sold. That cod travelled 15,000 kilometers. We all thought it was crazy, and very bad for the environment, so much unnecessary emissions from transportation. But we all learned a few new French words.

Then at our next class, we turned the page “Consommer local, vraiment bon pour la planète?” / “Consuming locally, really good for the planet?”. Wait what? The next article confused us since it stated that in many cases eating locally was bad for the environment, not good for the environment. Transporting the food around the globe might be good for the environment.

Incidentally, at the time I was reading “Not the End of the World, How we can be the first generation to build a sustainable planet” by Hannah Richie, the research director for “Our World in Data”. “Our World in Data” is a highly regarded free and open-source website that collects and analysis vetted statistics on a large range of topics. In that book she stated that the data showed that tomatoes imported to Sweden from Spain caused less carbon emission than tomatoes grown locally in Sweden.

The Problem with Locally Grown Tomatoes

This article from University of Southern Denmark claim that importing tomatoes from warm countries are better for the environment than buying locally. The reason being that when tomatoes are grown in an open field, the production emits an average of 80 kg CO2 per ton, but if the tomatoes are grown in a greenhouse, they emit up to 700 kg CO2 per ton. In northern countries it is common to grow tomatoes in greenhouses, especially when they are out of season. The long transport of the tomatoes causes much less emissions than that.

This scientific article analyses the issue a bit deeper and concludes that “that the distance travelled by the tomatoes is not the most important environmental burden”. Whether the tomatoes were grown in greenhouses or not matters a lot, but there are many other factors. In short, it is complicated.

Lots of fresh red tomatoes | Eating Locally is not Necessarily Ecological
Photo by Julia Nagy on Pexels.com

This study of local vs. imported tomato production in Canada concludes that locally grown tomatoes grown in greenhouses on average cause 1,070 grams of carbon emissions per kilo of tomatoes grown and tomatoes grown open field in Mexico cause 775 grams of carbon emissions per kilo of tomatoes, despite the 3,800-kilometer journey from Mexico to Ontario, Canada. The reason for the higher emissions for locally grown tomatoes is again that greenhouses use a lot of energy.

Naturally, this would change if you grew the tomatoes in season without using greenhouses. The article also notes that carbon emissions are not the only issue for sustainability. Water usage is another important factor.

The Problem with Locally Grown Vegetables and Fruits

Tomatoes are just one example. The same hold true for cucumbers, lettuce and salad greens, potatoes, bell peppers, hot peppers, green beans and other bean varieties, berries, pineapples, bananas, mangoes, other tropical fruits. In addition, some of these crops can deplete the soil and require large amounts of water, which can be bad if they are being cultivated in areas where water resources are already scarce such as growing avocados in California. In general, growing vegetables and fruits in their natural environment tends to be the most sustainable.

Fresh yellow bananas | Eating Locally is not Necessarily Ecological
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The Problem with Locally Grown Apples

The problem with apples tends to be the opposite, geography wise. In warmer areas, they might require significant water resources or chemical inputs to thrive. Apples from cooler climates need less water and fewer chemicals, reducing their ecological impact.

Lots of apples | Eating Locally is not Necessarily Ecological
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Local versus Imported It’s Complicated

I should point out that growing locally sometimes being worse for the environment than importing does not mean that importing produce is better for the environment. It just means that it is complicated and that you need to make that determination on a case-by-case basis. The environment is also not the only concern. Another consideration is the protection of local farmers and the local economy.

My opinion is, instead of worrying a lot about local versus imported produce, it is better to focus on things that we know cause a lot of emissions. A dirty grid, coal power stations, a non-hybrid SUV with an internal combustion engine, unnecessary business trips, eating a lot of red meat, basically start with the low hanging fruit.

Eating Locally is not Necessarily Ecological
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