How Big is Our Universe?

How Big is Our Universe?

We are tiny creatures, living out short lives in an immense and ancient universe.  We’ve evolved to make sense of the scales of time and space that were relevant for survival of our ancestors, so it is remarkable that we have any inkling at all of just how small we are when we zoom out to the cosmic scale.  As Douglas Adams wrote in ‘The Hitchhiker’s Guide to the Galaxy’:  

“Space is Big.  You just won’t believe how vastly, hugely, mind-bogglingly big it is.  I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.”  

To try to make sense of the vast distances between the stars and galaxies, lets scale down the universe.  It is remarkable that even when we shrink things down quite a lot, we find that it is difficult to keep the sizes from rapidly becoming astronomical once again.  This exercise also helps make clear why interstellar travel is such a difficult prospect, and may be nearly impossible to accomplish, even for a very advanced civilization.  This is some of the fun you can have on a Saturday afternoon with some imagination, a calculator, and an understanding of how to use scientific notation.   So, lets begin!

All right, for our first scale down cosmos we will shrink our sun down to the very manageable size of a 1 inch marble.  That’s pretty small right?  That is about 2 one hundred billionths of the suns actual size.  So, with a 1 inch marble at the center of our solar system, here is what follows.  The innermost planet in our solar system, Mercury would be in orbit 3.5 feet from the sun, Venus would orbit at 6.5 feet, and Earth would be a tiny 0.23mm speck (barely visible) sitting 9 feet from the sun.   Next comes the planet Mars sitting 13.6 feet from the sun.  This is our inner solar system, and so far still pretty manageable – a solar system you could fit fairly easily in your living room.

  Next comes the outer solar system with the mighty Jupiter, a speck of 2.5mm flying around the sun at 46 feet from our marble sun.  Beautiful ringed Saturn is in orbit at 85 feet, Uranus at 172 feet, and Neptune at 269 feet.  Little Pluto, now sadly demoted to a dwarf planet, is in orbit at 354 feet.  From that distance our little marble sun would appear tiny, yet it’s the gravitational pull on the tiny dust mote of Pluto that keeps it chained to the solar system.   No longer can we hold the outer solar system in our living room.  We might need to move our solar system to the park to hold it all.  

Think for a moment of how empty our solar system really is.  Tiny specks of dust orbiting a tiny star.  Our model 1 inch sun holds almost all the mass in the solar system.  The rest is just a scattering of microscopic dots out hundreds of feet from the center, with mostly emptiness between them.  The solar system is really very very empty, indeed.

The New Horizon space probe, our fastest space craft yet, visited Pluto last year, taking nearly 10 years to make the trip from Earth.   How fast can we possibly get through the solar system.  Light, traveling at the fastest speed possible in the vacuum of space moves, you guessed it, at the speed of light.  At our little solar system scale the light leaving the sun would take 8 minutes just to pass the Earth 9 feet away.  After an hour of travel the photons of light would move only 64 feet through our little solar system.  That would be somewhere between the orbit of Jupiter and Saturn.  Think of a sphere of light traveling in all directions from our 1 inch sun and taking a full hour to move to a sphere with a radius of 64 feet.  That seems rather slow, but there is nothing known in the universe that can do better.

On this scale 1 light year (the distance that light travels in one year) would be 107 miles from our little sun, and the closest star to the sun – Proxima Centauri at 4.24 light years away – would be a staggering 454 miles out.   Our little 1 inch sun floating alone in the darkness of space with next closest marble sized star being over 450 miles out in the distance.  If the sun marble was located in Los Angeles, then Proxima Centauri would be located approximately at 100 miles further north than San Francisco.   Is it any wonder that interstellar travel is such a monstrous challenge?  To travel between the stars on human time scales seems like an unrealistic dream.

The star Trappist-1, which was recently in the news for having been confirmed to have 7 exoplanets in orbit around it (some of which are in the starts habitat zone)  At a mere 40 light years from earth it has been toted has being very close to us indeed.  On the scale of our model solar system  Trappist-1 would be a small marble 4226 miles from our sun.  Again, if our sun was in Las Angeles then Honolulu would be only 60% of the way out to where the little marble of Trappist-1 would have to be placed – that vast Pacific wildness becoming the vast empty ocean between the stars.  

From our model sun, the center of the Milky Way galaxy would be 2,675,000 miles away, or about 11 times further out than our moon.   The size of the galaxy from end to end would be 10,700,000 miles across.  The next large spiral galaxy to us is the Andromeda galaxy and that would be placed 271,000,000 miles away.  Now that is getting into scales that match the sizes found in our actual solar system.  For example, if our marble sun was sitting in the very center of our actual sun, the surface of the real sun would be 4040 light years on our scale model.  The mini Andromeda galaxy would be beyond the orbit of Mars.

Ok, time to change our scale model to make the universe more manageable again.  Lets suppose that instead of our sun being 1 inch in diameter, our entire Milky Way galaxy is just 1 inch in diameter.  On this scale the Andromeda galaxy is another small disk (a little larger than our Milky Way) just 2.1 feet away from us.  The Virgo cluster of galaxies, which contains thousands of galaxies would be 54 feet away, and the edge of the observable universe, 46.6 billion light years away, would be 7.35 miles in every direction from our little 1 inch disk galaxy.  I’ve heard of races where runners run “the solar system” and pass the orbits of planets at the appropriate places on their 10K race, but you could do a “Run the Universe” race too, where you run a 10K and pass, not only deeper into space but farther back into time until you reach the very edge of time and space at the finish line.   By the way, even though the universe is only 13.8 billion years old the edge is 46.6 billion light years away because the universe expanded much faster than the speed of light in the distant past.  Inside the disk of our tiny 1 inch galaxy, the distance from the Sun to Pluto would be just 1.59 Angstroms, which is very nearly the size of a Hydrogen atom.

What if we wish to make our entire observable universe the size of a friendly 6 inch diameter snow globe, so we can put it out on our desk and admire the whole of creation as we do our work?  What would that look like?  If the observable universe was 6 inches in diameter, then the Milky Way galaxy would be a speck in the very center of the globe (yes, we are in the center of the universe from our vantage point) that was a mere 160 nanometers across.  This would be approximately the size of a virus.  In fact, all the hundreds of billions of galaxies in your Observable Universe globe would be the size of viruses.  I’m not sure you would see anything when you looked in your snow globe universe since the galaxies themselves would be microscopic on this scale, but you could surely feel quite satisfied that when you held your snow globe every galaxy in the observable universe was in the palm of your hand! 

Happy Winter Solstice

By Rich Feldenberg:

Your Winter Solstice this year (2015) will take place on December 21st at precisely 10:49pm Central Standard Time. The Winter Solstice is a consequence of the tilt of earth’s axis in relation to the sun, and at this time each year, the Northern Hemisphere is maximally tilted away from the sun by -23.5 degrees. This results in the sun being at it’s lowest point in the sky from our earthly perspective in the Northern Hemisphere, and leads to the day with the shortest daylight hours and longest night. So, axial tilt really is the reason for the season.

It may be true that many people today are not terribly concerned about the Winter Solstice, but to our ancestors living in pre-modern societies, hoping to survive through another harsh winter, the Winter Solstice had extreme importance, and was perhaps reason for celebration. For it was now that the daylight would begin to return to the world again. The journey back to Springtime had finally begun. Imagine living in a world without electric lights, central heating, a reliable food supply, and the only the most primitive technology and medicine. Our ancestors had to use all the clues that mother nature provided to figure out what gave them the best chances to stay alive.

As Neil Degrasse Tyson pointed out in his article, “Stick in the mud astronomy”, if you place a stick in the ground you can learn a lot! You’ll find that the sun casts a shadow of the stick, and that you can trace this shadow throughout the year. If you use the stick-shadow method to observe where the sun rises each day of the year you’ll find that the sun rises in a different place through the course of the year. Follow it through for the entire 365 days of year and you will trace out a figure 8 pattern. This occurs due to the eliptical orbit of the earth around the sun. The sun will be at its lowest point on the horizon, and cast the longest shadow, on the Winter Solstice. On the Winter Solstice the sun will be directly overhead at noontime on the Tropic of Capricorn, in the Southern hemisphere. There will also be two days of the year where your stick will cast shadows in the exact opposite direction at sunrise and sunset. This is on the spring and fall equinoxes. Its possible that people have taken the time to measure the Winter Solstice in this way for thousands, if not tens of thousands of years. Why would they bother?

The monument at Stonehenge gives us some insight into the importance of the Winter Solstice to the prehistoric Neolithic people. Its huge stones are arranged to allow sunlight to pass through a certain configuration at the time of the Winter Solstice. One of its functions was to act as a celestial calendar, so the timing of the solstice could be precisely measured. Stonehenge is thought to have been built around 4000 to 5000 years ago, but there is evidence for wooden posts in the area that may have served similar functions, dating back 8000 years or more. Back in these ancient societies, farm animals were slaughtered at the Winter Solstice, so they didn’t need to be fed for the remaining winter time.

Its no coincidence that many celebrations were observed throughout the millennia by ancient peoples around the time of the Winter Solstice. The Feast of Juul was celebrated in Pre-Christian european societies, and the Juul log (Yule log) was a tradition where a large log or tree was burned to honor the god Thor. Saturnalia was observed by the Romans to honor the god Saturn. There were the traditional exchange of gifts and lighting of candles and bonfires, but it sounds as though this was also a rather unpleasant time as it typically degenerated into a period of murder, robbery, rape, vandalism, and so on, as there was no enforcement of the law during Saturnalia. Of course, in our modern society Christmas is celebrated on and around December 25th. The bible does not give a specific date for the birth of Jesus, but many scholars believe the date for Christmas celebration was chosen because of the pagan celebrations of Saturnalia and others could then more easily abandoned by switching one set of traditional celebration with a new set. The first known celebration of Christmas was in 336AD by the Roman Emperor Constantine.

Not really related to the Winter Solstice, but worth pointing out is that Sir Isaac Newton was born on December 25th 1642. Many science enthusiasts and secular humanists enjoy celebrating Newton on this day to honor his important contributions to science. Newton was a founder of modern science, inventing calculus to complete his calculations of physical motion. He is also known for his many additional contributions, including his law of gravitation, study of light and optics, improvement in telescope design, and more mathematical developments, as well. He was born on December 25th by the calendar in use at the time – the Julian calendar. The Gregorian calendar, which is our modern version, replaced the Julian calendar because it was more accurate, using the concept of the leap year to keep the seasons from drifting into other parts of the year. It’s original purpose was to prevent Easter from moving into other months as the earths rotation around the sun is not an exact 365 days. By the Gregorian calendar, Newton would have been born on January 4th, 1643. Anyway, Merry Newtonmass to my fellow science enthusiasts.

Merry Newtonmass to you good Sir!

The Winter Solstice is a reminder that we are still just inhabitants of planet earth, exposing our kinship to our cosmic environment. We have gained so much more knowledge -thanks to the ingenuity of our species – than our prehistoric ancestors had about what the earth and sun really are, how they move through space, and where we come from, but at the same time we seem to have lost the sense of oneness with the universe that our ancestors must have felt. We are riding on a spinning mass of rock as it circles a star in an enormous galaxy. The ancients knew that they were connected to the clockwork of the heavens. In our modern society we all too often forget that we also have that connection with the earth and solar system. We don’t worry as much that our families might not make it through the winter, this time. That our entire village might die of starvation, cold, or sickness. Most of us have enough food to eat, heated homes, and access to medical care. Sure, we all have new and different kinds of worries that our distant ancestors wouldn’t have understood, but they may have displayed some wisdom that we can still benefit from if we pay attention. So Happy Winter Solstice. May you and your family be happy and safe this holiday.

References:
1. Winter Solstice, The Telegraph, Dec. 20. 2015. 
2. Stonehenge Wikipedia. 

You Must First Invent the Universe…

By Rich Feldenberg

This year Carl Sagan Day is being celebrated Saturday, November 14th. Sagan, who was born on November 9th, 1934 has been an inspiration to generations of scientists and science enthusiasts. Unfortunately, he passed away on December 20th, 1996 at the age of 62. Way too young, and certainly way too soon for a world that desperately needed his carefully measured dose of rationality, skepticism, and his poetic style of revealing the awe of the cosmos we inhabit together.

There are many great and inspiring Sagan quotes, or Saganisms as they’ve come to be known, but one of my favorites is, “If you want to make and apple pie from scratch, you must first invent the universe”. The meaning, of course, gets one to think deeper about where the origin for all the things we take for granted actually came from. The ingredients for an apple pie may include things like apples, flour, sugar, eggs, salt, etc. But where to these ingredients come from? To get these ingredients you must first invent a universe with laws like our own, that can lead to the formation of galaxies full of stars, which can fuse hydrogen atoms into heavier elements, which can then form planets. Some of these planets must have conditions that allow life to arise, which can evolve into things like apple trees and chickens (for the apples and eggs respectively) and for the evolution of intelligent beings that can put them together to make an apple pie. Some of the ingredients, like the salt (NaCl) and water (H2O), are relatively easy to produce, and just require the hundreds of millions of years necessary for stars to produce the heavy elements oxygen, sodium, and chloride (the hydrogen for the water was produced in the Big Bang itself). The other ingredients require billions of years in the making, for life forms and their evolution to take place. How brilliant and wonderful and simple a statement to make. Many people around the globe, that continue to honor and remember Carl make it a tradition to eat a slice of apple pie on Carl Sagan day. I know I plan to have a piece this year!

Sagan was an Astronomer, and one of the first astrobiologists. He was involved in important scientific research on the atmospheric composition of Venus and Mars. He played a major role in the Viking mission to Mars and the Voyager probes to the outer solar system. And, of course, he made communicating scientific findings to the public, and demonstrating the importance of the scientific process, a priority.

When I was growing up, the book Cosmos and the mini-series, by the same name, came out. Both were inspiring, thought provoking, and in some ways life altering, and Sagan tackled everything from Astronomy, evolution, the brain, and the importance of being skeptical of pseudoscientific claims. He had a mesmerizing way of delivering his message with intelligence and passion. The TV series was recently redone by Astrophysicist and science communicator, Neil Degrasse Tyson, who didn’t attempt to remake the original episodes, but who did an excellent job of continuing on where Sagan left off.

Sagan also wrote quite a few other excellent books. These included, “The Dragons of Eden”, “Broca’s Brain”, “The Demon Haunted World”, and “Billions and Billions”. These books really fueled my scientific curiosity growing up, as I’m sure they have done for many others who grew up to love science. After all these years, his books are still worth reading, if you haven’t done so already. He also wrote the science fiction novel, “Contact” that was made into a motion picture in 1997 with actress Jodie Foster. In the novel he attempted to show what first contact with an advanced alien species might be like.

I did have the opportunity to see Carl Sagan in person on one occasion. At the time I was a chemistry major in the mid-1980s at The University of Missouri – St. Louis. Sagan came to deliver a lecture to our university on the dangers of nuclear war and the importance of nuclear disarmament. He was a great dynamic speaker and the lecture hall was completely full. I think, at the time I was hoping he was going to talk about astronomy, but in retrospect I now understand the importance of his social concerns for our future and continued existence.

Sagan also introduced me to the concept of scientific skepticism, at a relatively early age. He was critical of how to tell the difference between science and pseudoscience (something now called the demarcation problem). He showed us that there are no beliefs that should be immune to skeptical inquiry, including religious belief. He came up with the “Baloney Detection Kit” that everyone should have in their skeptical toolbox.

Carl passed away right when the first exoplanets were just being discovered. Now we know of more than 1000 planets that circle other stars. We have made a much more thorough exploration of Mars and the moons of the outer solar system. We have strong evidence for liquid water deep under the crust of the moons Europa, Enceladus, and Ganymede. There is liquid methane on Saturn’s moon Titan. These discoveries make the possibility for life in our outer solar system a little more likely, and for life outside of our solar system very likely, by the sheer number of planets in our galaxy alone. At the same time the skeptical movement has gained momentum and is going strong. We have learned more about cognitive psychology and our innate biases and predisposition towards distortions of memory and perception. Flaws we must recognize in ourselves if we are to take the first steps to learn to become a more rational species and rise out of our superstitious past. I believe Carl would find all this fascinating and exciting. We could really use Carl’s wisdom now, but at the very least we still have him with us in the form of his writing and video.     

Happy Carl Sagan Day. Have some Apple Pie and be sure to learn something new today!
References and other items of interest:
1. Carl Sagan Wikipedia article: https://en.wikipedia.org/wiki/Carl_Sagan
2. Article detailing the “Baloney Detection Kit”: https://www.brainpickings.org/2014/01/03/baloney-detection-kit-carl-sagan/
3. Trailer for the movie “Contact” based on the book by Carl Sagan: https://www.youtube.com/watch?v=jl7Xe80_0MY
4. The Demarkation Problem on the Rationally Speaking Blog.
http://rationallyspeaking.blogspot.com/2013/08/philosophy-of-pseudoscience.html
Also check out the excellent “Rationally Speaking” podcast. The current host is Julie Galef, and excellent skeptic and teacher of all things rational! The previous host was Massimo Piglucci and scientist and philosopher and all around brilliant guy. Well worth checking out!
5. The Rationally Speaking Podcast with Julia Galef: http://rationallyspeakingpodcast.org
6. Some great Julia Galef youtube videos on rationality: https://www.youtube.com/user/measureofdoubt
7. Massimo Piglucci’s homepage: https://platofootnote.wordpress.com/massimo-central/
8. My contemplations on the possibility of what it would take for life to evolve on Titan:
http://darwinskidneys-science.com/2015/08/05/musings-on-the-biochemistry-on-saturns-moon-titan-part-i/