Black Moon

Today, December 30, 2024, we are having what is called a Black Moon. In Europe it will be December 31.  This is not a super-fact post. Just some lighthearted information about the Black Moon phenomenon.

What is a Black Moon?

The most common definition is that it is the second new moon in a single calendar month. That’s what we are having now. During a new moon the moon is located between the sun and earth, which means that the night side of the moon is directed towards us. At night it is usually below the horizon and during the day you can’t see it.

However, there is one exception to that and that is when you are having a solar eclipse. In that case the moon is directly in front of the sun. It is an unusually well-placed new moon if you will. Here in Dallas, we had a total solar eclipse on April 8 this year. It was a remarkable experience. It turned daker, cooler, some stars and planets came out, including Venus, and the birds and insects stopped singing. I have included some photos from that event below. What you see is the dark side of the moon with the sun hiding behind it.

I took this photo with my old Samsung 8+ phone before we had totality. Since the sun was still partially visible and bright I used a filter / a pair of glasses that I held in front of the phone.
A friend Denise Mosier-Wanken took this photo with her phone. The sun is almost gone. The fuzzy fog like light around the black circle is the sun’s corona.
My daughter Rachel took this photo with her iPhone.
A professional solar eclipse photo with filter. What we saw with our eyes was something in between this photo and the photos we took. The corona in our photos is too big. This one is too small. Stock Photo ID: 2344355767 by aeonWAVE.

Alternative Definitions of a Black Moon

As mentioned, the most common definition of a black moon is that it is the second new moon in a single calendar month. However, there are other definitions:

  • A month with no full moon
  • A month with no new moon
  • The third new moon in a season with four new moons. A season is defined as the period between a solstice and an equinox and is roughly three months.

A New Moon is a Star Gazing Opportunity

Since there is no moon in the sky the night is a little bit darker. This makes a significant difference in places that are very dark and very far away from city lights. There is so much light pollution here in Dallas, so it doesn’t matter here. However, I still took out my little telescope and observed easy objects, such as Venus, Mars, Jupiter and its four Galilean moons.

The three little dots are three of the four Galilean Moons. I roughly saw this in my telescope a couple of hours ago, but it is not my photo. Photo by Raoni Aldrich Dorim on Pexels.com

The Near Side and the Far Side of the Moon

The moon is always showing us the same side, the so-called near side. The far side, or the back side, you can only see from spacecrafts. Look at the photo below. The near side is on the left whilst the far side is on the right. During a new moon the near side (left) is dark, and the far side (right) is lit up by the sun. But again, you cannot see the far side (right), which is turned away from us.

During a full moon the near side (left) is lit up by the sun, and the far side (right) is dark. One interesting fact about the moon is that the near side (left) and the far side (right) are very different. The far side (right) not only looks different, it has a crust that is much thicker compared to the near side, and it is also densely cratered compared to the near side.

The near side of the Moon and the far side of the Moon. Comparison between the two hemispheres of the Moon. Elements of this image were furnished by NASA. Stock Photo ID: 2157518223 by Claudio Caridi.

Below is a youTube video showing an animation composed of actual satellite photos by NASA.

In this video the near side of the moon is dark. It is a new moon and the people on earth don’t see the moon. The sun is behind us and lights up both earth and the far side of the moon (the side people on earth do not see), so that is what the space craft see.

Happy New Year

Finally, a Happy New Year to all of you from Rollo and me. He may not look that happy but that is because I am leaving over the New Years. We have a dog sitter though. For the same reason I will not be on-line tomorrow.

Happy New Year from Rollo

To see the Super Facts click here


Global Warming is Happening and is Caused by us

Superfact 25: Global warming is happening. Or if you call it Climate Change or Climate Disruption is happening. And it is happening very fast. We also know that it is caused by us primarily as a result of our burning of fossil fuels. There is a long-standing scientific consensus on these two facts because the evidence is conclusive. Check the evidence below.

This is a long post. However, I summarized this somewhat complex issue in a post I hope is both comprehensive and easy to read at the same time. I believe you can learn a lot from reading it. Note in this post, Global Warming Is Happening And Is Caused By Us, I will use the terms climate change, climate disruption and global warming interchangeably, or nearly interchangeably. I am doing that on purpose.

A lot of people would like to dispute this fact. Including large segments of the public, politicians, and political organizations. I was once a so-called skeptic myself. However, climate scientists very rarely dispute this because of the large amount of compelling evidence. This is a good summary from NASA. We know it’s true, it is important, yet disputed, which makes it a super fact in my opinion.

Below I created a top 10 list of evidence for the fact that climate change / global warming is happening. As well as a top 10 list of evidence for the fact that we are the cause for it. Primarily because of our burning of fossil fuels.

Evidence that Global Warning is Happening

  • (1) The temperature records collected by numerous organizations show that global warming is happening. Organizations such as NASA, NOAA, the Hadley Centre, the European Centre for Medium-Range Weather Forecasts, the Japanese Meteorological Agency, the World Meteorological Organization, and many more, use data from land-based weather stations, ocean buoys, satellite measurements, and other sources to monitor Earth’s climate. Comparison with the palaeoclimatological record shows that the rise in average global temperatures is extremely fast. This is the smoking gun. However, for those who question the data from all of these organizations there are other simpler types of evidence (see below).
  • (2) Global sea levels has increased by 20–25 cm (8–10 in) since 1900, with half of that increase occurring since 1980. Sea level rise occurs from a combination of thermal expansion and the melting of land ice, both which happen as a result of warming. This sea level rise has been the fastest in “at least the last 3000 years”.
  • (3) Arctic ice is melting. See the video from NASA below.
  • (4) Glaciers are retreating.
  • (5) The Antarctic ice sheet is losing ice at a rate of about 100–200 billion tons per year, which has increased in the past two decades.
  • (6) Eco zones are generally shifting northward and to higher elevations, meaning that plant and animal habitats are moving towards cooler regions as temperatures rise in previously suitable areas.
  • (7) Snow seasons are getting shorter
  • (8) Extreme events are increasing in frequency showing that climate is changing
  • (9) After extensive research and scientific debates in the past there is now a long-standing scientific consensus that Global Warming is happening. This is not physical evidence itself, but it does not an appeal to authority fallacy either. Think about it in terms of probability.
  • (10) Old guys originating from northern climates like me, have noticed that the seasons are changing. Even if you dismiss all the evidence from NASA, NOAA, IPCC, and all the world’s meteorological institutions, and you claim that all the world’s climate scientists are all in a massive conspiracy, you cannot convince me of something that is contrary to what I can see with my own eyes.

Graphs and Videos Showing Global Warming

To see the NASA web page from where the YouTube video of the shrinking arctic ice is taken click here .
Temperature anomaly graphs from NASA, Hedley Center, Japan Meteorological Agency, NOAA, and Berkley. Wikimedia commons << https://creativecommons.org/licenses/by-sa/4.0/deed.en>&gt;.
The so-called hockey stick curve depicting the last 1,000 years. The blue line is the first hockey stick curve ever created (by Michael Mann). He used proxy measurements such as tree rings, green-dots 30-year average, red temperature measurements. Wikimedia commons <<https://creativecommons.org/licenses/by-sa/4.0/deed.en>>. This graph is taken from this page
Temperature record for the last 150,000 years. Notice the sharp uptick towards the end. This picture is taken from this article.

Confusion About Climate Change

Before continuing I would like to address a couple of issues that sometimes trip up people. And prevent them from learning about this topic.

The question “climate has always been changing, why would we be the cause now?”, is a good question. If asked honestly. However, it is a bad question if it is asked like a gotcha or a dismissive statement. In this case it is a bad question. Because the paleoclimatologists and the climate scientists, in other words the experts on past climate, are the ones telling us that the current climate change / global warming is caused by us, it is not “natural”. They obviously say that because they know something that the dismissive laymen don’t. All everyone needs is a tiny bit of reflection to realize that you’ve got something to learn from them.

Sometimes you come across people who have a hangup over the fact that we use a few different terms interchangeably, global warming, climate change, climate disruption, inadvertent climate modification, etc. The people who have a hangup about this jump to the incorrect conclusion that there is some sort of deception or backtrack going on. If I talk about my dog and my mini-Australian Shepherd, I am not confused or deceptive or backtracking anything. It is the same family member. Whether you call it global warming or climate change or something else is a distracting non-issue, a red herring if you will.

To add some information about it. Climate change has become the more popular term recently, but the terms climate change and inadvertent climate modification predates the term global warming, which became popular in the 1980’s largely because climate scientist James Hansen likes to use it. Climate change is a broader term since it could include global warming and global cooling, but in the current context, global warming is a good term as well since that is what is happening now. 

One advantage of the term climate change is that the average warming trend is in itself not the major issue. The effects on the overall climate that warming has is the more important issue. You could say that you want some global warming when the weather is cold and it would make sense. But you don’t want the destruction of eco systems, oceanic and atmospheric circulation changes, sea level rise, worse storms, draughts, floods, wildfires, etc., that it causes.

Natural Causes of Climate Change

There are many different kinds of natural causes of climate change. Two billion years ago cyanobacteria developed a form of photosynthesis that absorbed carbon dioxide and emitted oxygen, as well as a way of extracting nitrogen using a process called nitrogen fixation. This made cyanobacteria extremely successful. One consequence of this was that the carbon dioxide was largely removed from the atmosphere, and the earth got very cold, but the oxygen that was now present in the atmosphere paved the way for the existence of multicellular life and animals. To find out more about this, read this book

The planet changed but it took millions of years. The emergence of land plants did something similar. Examples of other slow-moving drivers of climate change are continental drift and the fact that the light from the sun has gotten 6% stronger over the last one billion years (0.006% per million years).

Cyanobacteria caused a global cooling two billion years ago while paving the way for the existence of multicellular life and animals. Stock Photo ID: 2197045895 by Andre Engelhardt.

65 million years ago an asteroid struck earth, which caused earth’s climate to change, which is probably what killed the non-avian dinosaurs. Another example of a past climate change driver is unusual volcanic activity. Volcanoes emit greenhouse gases, such as carbon dioxide (CO₂) and water vapor, during eruptions. 

However, their contribution to the total CO₂ emissions in modern times is very small compared to human activities. Annual volcanic CO₂ emissions are estimated to be around 200-500 million tons while humans add 37-40 billion tons, or 100 times as much. Therefore, it is unlikely that volcanoes contribute much to the current warming, but the fine sulfate aerosols emitted by volcanoes can cause a significant cooling effect for a few years.

Dinosaur and asteroids during extinction day Stock Illustration ID: 1438260563 by serpeblu
Volcano – An active volcano that erupts lava. Stock Illustration ID: 2497156167 by MERT1995

One type of important type of climate forcing that’s been the cause behind the multiple ice ages that we’ve had over the last two million years are earth’s orbital cycles, or the Milankovitch cycles. There are three of them, orbital eccentricity, change in axial tilt, and axial precession. Could they explain the current warming? No, they can’t because we are currently in a cycle that should be cooling the planet. And it was until now. Below I have included a video from PBS that explains these orbital cycles.

Illustration of Milankovitch cycles from MIT’s Climate Primer.<< Link-22>>.
From PBS explanation and overview of earth’s three orbital cycles.

There are also short-term solar irradiance cycles. There is an 11-year cycle and an 80-year cycle, but these correspond to small changes. The 11-year cycle corresponds to a temperature change of 0.05 degrees Celsius. 

In addition, the Sun’s irradiance has been slightly decreasing over the past few decades. Changes in the sun’s irradiance cannot explain the sharp warming we are witnessing. As you’ve seen above, neither can volcanic activity nor any known orbital cycles, slow moving climate drivers such as continental drift cannot explain it and we did not get hit by an asteroid recently. However, what fits the bill almost perfectly is our greenhouse gas emissions.

This is a brief overview from MIT.

What Does Climate Models Say About Climate Change

Unlike weather, the climate is not particularly sensitive to initial conditions (chaos). For example, we can be pretty certain that July will be warmer than January in Minnesota. We use climate models to try to predict future climate. All climate models rely on the laws of thermodynamics. But they vary in regard to the different understandings of the best ways to incorporate those laws in a representation of all of Earth. They do not come up with identical results. But they all get the average temperature of each region of the world right. 

In addition, the various old climate models from the 1990’s do a very good job of what has happened during the last 30 years. They aren’t perfect but they are useful and more importantly for our context they serve as powerful evidence that the current warming is caused by our emissions. You remove our emissions from the models and none of what we measure will happen. Climate models are therefore the smoking gun with respect to what is causing global warming, just like the temperature record is for the fact that it is happening in the first place.

Unfortunately, the climate models have been maligned and misrepresented by those who wish that the public do not pay attention to them. That’s why we need to mention additional types of evidence (see below).

Evidence that Global Warming is Caused by US

  • (1) Climate models – as we have seen above, climate models are the smoking gun evidence that we humans are causing global warming / climate change. In addition, both simplistic and complex climate models show that 100% of global warming is caused by humans.
  • (2) Greenhouse gases will make the planet warmer, and we are emitting a lot of them.
  • (3) The upper troposphere is cooling, which shows that the heating is from greenhouse gases and not the sun or orbital cycles. To understand how the lower atmosphere is warming while the upper is cooling, think of the greenhouse gases as a blanket.
  • (4) winters and nights are generally warming faster than other seasons and times of day due to the increased presence of greenhouse gases in the atmosphere, which trap heat more effectively during colder periods. This is considered a key indicator of human-induced climate change.
  • (5) The speed of the warming, 0.31 degrees Fahrenheit per decade, or 0.17 degrees Celsius per decade is extremely fast. Known natural climate forcing tends to be slower.
  • (6) Human activities is the only known explanation for the current global warming. One way that we know that the current warming is caused by human activity is because we are currently in a cycle that should be cooling the planet. The same is true for the sun’s irradiance. It is not volcanoes or any other known cause. See the section above called “Natural Causes of Climate Change”.
  • (7) Isotope studies show that the origin of the greenhouse gases added to the atmosphere are from burning fossil fuels. This is referred to as the isotopic footprint.
  • (8) The observed temperature rise mirrors industrialization.
  • (9) More than 90% of excess heat from global warming is absorbed by the oceans, causing significant increases in ocean temperatures. Oceans absorb about a quarter of human CO₂ emissions, leading to lower pH levels. This is unprecedented in at least 26,000 years and is directly linked to anthropogenic CO₂. These effects have been carefully studied and observed.
  • (10) Nearly all actively publishing climate scientists say humans are causing climate change. This is not physical evidence itself, but it does not appeal to authority fallacy either. Think about it in terms of probability.
This is a short one-minute overview of the causes behind global warming that is happening.
This video from NASA is a bit longer, 13 minutes. Click here to see the page this is coming from
Natural causes for global warming / climate change would have cooled the planet, not warm it. Click here to visit this NASA web page regarding the causes behind global warming.<<Link-31>>
The carbon dioxide concentration measurements began in 1958 at the Mauna Loa Observatory on the island of Hawaii. Since then, several other ways of measuring carbon dioxide concentration have been added.
From Scripps institute. Keep two things in mind. First the warming from CO2 is delayed and may result in positive feedback that can manifest decades and centuries later. Secondly, human civilization developed during a period of stable climate. That CO2 levels and temperatures were higher millions of years ago is not much comfort.
Going back 800,000 years. From Scripps institute.
A Global Warming protest. It’s their future. Stock Photo ID: 1427361263 by manpeppe

To see the other Super Facts click here

Smallpox Killed 300 million People in the Last Century Before Eradication

Superfact 24: Smallpox killed 300 million people in the 20th century. However, there have been no naturally occurring cases of smallpox since 1977, and the world was declared free of smallpox on May 8, 1980, by the 33rd World Health Assembly.

Smallpox vaccine Stock Illustration ID: 1782022109 by Novikov Aleksey

300 million people is an astonishing number. It is six times the 50 million people who died from the Spanish flu. It is about four times as many people as the 70 to 85 million people who died in World War II. It is close to the entire current population of the United States. That’s how many people died from this very dangerous disease. It was eradicated by a vaccination campaign.

I think this fact qualify as a super-fact, first of all because of the astonishingly huge number of deaths but also for the fact that it is gone. It is hard to believe that this happened. It is hard to believe that the world has changed so drastically for the better. It is a shocking but true fact. Thanks to the vaccination campaign we are living in a much better world.

This world map shows when smallpox was eradicated from different countries. The source is Our World in Data, originally Fenner et al. at CDC.

What is Smallpox?

Smallpox is an infectious disease caused by the variola virus<<Link-1>>. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (WHO) certified the global eradication of the disease in 1980.  The disease begins with fever and vomiting followed by the formation of ulcers in the mouth and a skin rash that later turns into fluid filled blisters with a dent in the middle. These blisters get scabbed and leave scars. The death rate was about 30%.

Child with smallpox in Bangladesh 1975. Wikimedia commons photo by CDC/James Hicks.

The Eradication of Smallpox and Vaccines

The smallpox vaccine has a long history that begin in China where smallpox inoculation had existed long before it did in Europe. In 1796 the English physician Edward Jenner demonstrated the effectiveness of cowpox to protect humans from smallpox. Soon after several countries enacted mandatory vaccinations.

In 1807, Bavaria became the first country in the world to introduce compulsory vaccinations. In 1958 the World Health Assembly was called upon to eradicate smallpox. At this point 2 million people still died from smallpox every year. In 1967 the World Health Organization intensified the global smallpox eradication. As mentioned, smallpox was eradicated at the end of the 1970’s.

In 1998 & 2002 vaccination was dealt a blow by the Wakefield studies claiming that the MMR vaccine caused autism. Even though the studies were debunked, and several later studies showed no link between the MMR vaccines and autism, the fear of vaccines began to spread.  

For example, in 2024 the American Veterinary Medical Association reported 37% of the dog owners surveyed believe canine vaccination could cause autism in their dogs. Not only is there no link between vaccines and autism, but technically speaking, dogs cannot be autistic as the condition is unique to humans. Unfortunately, the unnecessary fear of vaccines causing autism seems to only be getting worse.


To see the other Super Facts click here


Are you vaccinated against smallpox?

What Can We Do About Climate Change

The goal of this blog is to create a list of what I call super facts. Important facts that we know to be true and yet they are surprising, shocking or disputed among non-experts. Super facts are important facts that people get wrong. However, I also create posts that are not super facts but other interesting information, such as this book review and book recommendation.

Saving Us: A Climate Scientist’s Case for Hope and Healing in a Divided World

Saving Us: A Climate Scientist’s Case for Hope and Healing in a Divided World by Katharine Hayhoe is a book about human caused Climate Change, how bad it is, and what we can do about it. The good news is that we are not all going to destroy ourselves. It is still bad, but we can do a lot to avoid making it really bad. However, there are a lot misunderstandings regarding what really makes a difference. This book examines these issues with a good dose of realistic optimism and science. I read the hardback version (and my review on Amazon is currently the top review).

  • Hardcover –  Publisher : Atria/One Signal Publishers (September 21, 2021), ISBN-10 : 1982143835, ISBN-13 : 978-1982143831, 320 pages, item weight : 1.05 pounds, dimensions : ‎6 x 1 x 9 inches, it costs $19.14 on US Amazon. Click here to order it from Amazon.com.
  • Paperback –  Publisher : Atria/One Signal Publishers (September 20, 2022), ISBN-10 : 1982143843, ISBN-13 : 978-1982143848, 320 pages, item weight : 8.8 ounces, dimensions : 5.5 x 0.7 x 8.38 inches, it costs $17.22 on Amazon. Click here to order it from Amazon.com.
  • Kindle –  Published : Atria/One Signal Publishers (September 21, 2021), ASIN : B08BZW2BQG, 318 pages, it costs $14.99 on US Amazon. Click here to order it from Amazon.com.
  • Audiobook –  Published : September 21, 2021, ASIN : B08D4RGYM8, Listening Length : 8 hours and 7 minutes, it costs $16.40 on US Amazon. Click here to order it from Amazon.com.
Front cover of Saving Us. Click on the image to go to the Amazon page for the hardcover version of the book.

Amazon’s description of the book

“An optimistic view on why collective action is still possible—and how it can be realized.” —The New York Times

“As far as heroic characters go, I’m not sure you could do better than Katharine Hayhoe.” —Scientific American

“It’s not an exaggeration to say that Saving Us is one of the more important books about climate change to have been written.” —The Guardian

United Nations Champion of the Earth, climate scientist, and evangelical Christian Katharine Hayhoe changes the debate on how we can save our future.

Called “one of the nation’s most effective communicators on climate change” by The New York Times, Katharine Hayhoe knows how to navigate all sides of the conversation on our changing planet. A Canadian climate scientist living in Texas, she negotiates distrust of data, indifference to imminent threats, and resistance to proposed solutions with ease. Over the past fifteen years Hayhoe has found that the most important thing we can do to address climate change is talk about it—and she wants to teach you how.

In Saving Us, Hayhoe argues that when it comes to changing hearts and minds, facts are only one part of the equation. We need to find shared values in order to connect our unique identities to collective action. This is not another doomsday narrative about a planet on fire. It is a multilayered look at science, faith, and human psychology, from an icon in her field—recently named chief scientist at The Nature Conservancy.

Drawing on interdisciplinary research and personal stories, Hayhoe shows that small conversations can have astonishing results. Saving Us leaves us with the tools to open a dialogue with your loved ones about how we all can play a role in pushing forward for change.

This is my five-star review for Saving Us

Climate Change; what can we do? Talk about it!

This is an extremely well written, informative, and hopeful book on climate communication. A decade ago I was doubtful that human caused climate change was anything to worry about even though it physically made sense that it was happening. I thought environmentalists were exaggerating and distorting the facts. In general I did not trust or respect environmentalists whom I thought were driven by leftist agendas.

I studied the topic on my own by reading books and scientific articles on the topic, and I learned what climate scientists, not opinionated bloggers, said about the topic. I was especially impressed by a book by James Hansen.

I came to realize that human caused global warming definitely was real and a serious problem. I think I was able to change my mind so easily because I never had a strong affiliation with a political tribe, I respected scientific expertise and my encounter with science deniers in other fields had inoculated me against their kind of rhetoric (it’s fairly universal). I’m an abstract thinker who loves pro-con-lists, and I prefer going in deep and I am not afraid of math, but I don’t think that’s typical.

The backside of that is that it made me a pretty crappy and easily frustrated climate change communicator once I came around. I felt I needed to take action so I joined Citizens Climate Lobby (CCL), a bipartisan volunteer organization with good solutions and good practices. From CCL I learned how to communicate better. In this book Katherine Hayhoe praises CCL and use it as a model for how to approach climate change with respect to solutions and communication.

In addition to climate change communication she gives a high level overview of why we know that global warming is happening (there are 26,500 lines of independent evidence for climate change), how fast it is happening (10 times faster than the last ice age warming), and how we know it isn’t natural. It’s a simple overview, not a deep dive. I thought her analogy about driving while looking in the rearview mirror as you hit a curve to be genius.

She also discusses our cognitive biases, and why not to engage with the 7% who are dismissives, the abuse she’s been a victim of, and so called zombie arguments. Zombie arguments are dismissive arguments that have been thoroughly debunked over and over but won’t die because they fulfill an emotional need for those who are dismissive of climate change. She discusses the political divided in the US, the “blame and shame the consumer” tactic and the misguided “population control solution” and solutions aversion in general.

She describes our situation lucidly. That there is no particular known limit that will doom us all. It is like smoking; you don’t get lung cancer after a certain amount of cigarettes, it’s just better to stop as soon as you can. She discusses solutions and the economy, including cap and trade and a price on carbon, and she states we don’t have to harm the economy to solve climate change, and a lot is already being done the world over. It is a mostly hopeful view.

I was surprised to learn that if you take into account, production subsidies, tax breaks, land leases on public lands below market rates, and the cost of pollution, the IMF estimates that fossil fuel subsidies in the US top $600 billion per year, twenty times clean energy subsidies. That’s about $2,000.00 per person and year, or $8,000.00 per family per year. That’s a lot of money.

Because of my experience with CCL I recognized a lot of what Katherine Hayhoe was saying in this book, but I still had a lot to learn, and besides the book is hopeful, and intelligently written and therefore a pleasure to read. She stresses that the most important thing we can do to solve climate change is to talk about it. I love this book and I highly recommend this book.

Back cover of Saving Us. Click on the image to go to the Amazon page for the kindle version of the book.

To see the Super Facts click here


GPS uses relativity for accuracy

Superfact 23: GPS uses relativity for accuracy. Global Positioning Systems or GPS uses Special Relativity and General Relativity to guide you to your destination. In fact, GPS systems would be rendered useless without the Theories of Relativity.

Stock Photo ID: 2502019165 by mayam_studio

Did you use Einstein’s Theories of Relativity to get to the grocery store today?

The theories of relativity may seem strange and impractical, something you only use for astrophysics, black holes, cosmology and extreme velocities. They feature strange concepts such as time dilation, the stretching and bending of space, events simultaneous to some are not to others, the universal constancy of the speed of light in vacuum, the energy and mass equivalency, etc. 

Therefore, it is a bit surprising that without the theories of relativity the GPS app on your phone would not be able to guide you to the grocery store. That’s why I call it a super fact that GPS uses relativity for accuracy.

Stock Illustration ID: 1372134458 by Boris Rabtsevich

GPS and Time Dilation

GPS is a satellite-based radio navigation system that provides location information and time anywhere on Earth. The fact that the information is provided by satellites that orbit earth at high speeds and high above earth’s surface makes General Relativity and Special Relativity necessary

The GPS system needs to calculate precisely the time it takes for signals to travel from the satellites to a receiver on Earth for it to work. GPS satellites travel at high speeds causing a large enough time dilation that has to be accounted for. In addition, they orbit earth high above earth’s surface where earth’s gravitational field is weaker than on earth’s surface. Clocks run faster in weaker gravitational fields due to gravitational time dilation, so you must correct that as well.

If you ignore relativity, you will accumulate a discrepancy of six miles in one day.  You are not going to find the grocery store that way, unless you use the old-fashioned method of reading a map. In a sense, if your GPS device finds the grocery store for you, you have proven Einstein right.


To see the other Super Facts click here