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! 

Why New Horizon’s journey to Pluto is so important for us here on earth.

Why New Horizon’s journey to pluto is so important for us here on earth.

by Rich Feldenberg

  

Almost like a time traveler sent 10 years too far back in time before an important event, I’ve been waiting for July 14th, 2015 for a long time.  Ever since the New Horizons space probe was launched from Cape Canaveral, way back on January 19, 2006, I knew this day would get here eventually.  It just seemed like our little space probe was taking its sweet time.  Nine and a half years is a long time to wait to see a new world – a world never before seen up close and personal.  In actuality, New Horizons was doing anything but taking its time.  It has been speeding towards its destination at over 36,000 miles/hour!  It passed earths moon in a mere 9 hours.  It happens to be the fastest man made object ever.  It’s just that it had a very long way to go to reach its destination.  Today New Horizons will make its closest encounter with Pluto, and almost certainly will increase our knowledge and understanding, not just of Pluto and its entourage of little moons, but of the origins and history of our solar system.  

Pluto was only discovered as recently as 1930 by Clyde Tombaugh at the Lowell Observatory.  Even from the beginning it seemed a little odd in comparisons to the other planets.  It takes about 247 years to orbit the sun and has a very eccentric orbit with its closest point in orbit at 2.7 billion miles from the sun (and inside the orbit of Neptune), and its farthest point in orbit being around 4.5 billion miles away from the sun.  It has five known moons, but the largest is Charon, which has a diameter that is more than half as big as the diameter of Pluto itself.  No other planet has a moon so close to its own size.  For that reason, many planetary scientists consider the Pluto/Charon system a binary system.  

Today’s post will go live on Tuesday instead of the usual Darwin’s Kidneys Original Wednesday (sorry Atomic Tuesday) to coincide with this historic occasion.  In this post I’m not going to write about the New Horizons discoveries, or much about the mission itself.   I’m not even going to write about whether Pluto should be classified as a planet or not.  I don’t really care that Pluto got “demoted” to dwarf planet because no matter what we label it, Pluto is a fascinating object with a history as old as our solar system.  Instead this article will focus mostly on why we should be interested in a tiny, human made hunk of electronics, computer chips, and metal, speeding to the edge of the solar system to photograph and measure a dark, frozen, ancient celestial body whose chance of harboring life is somewhere between zero and not bloody likely.  Why should we, as a society, spend money and resources to design, build, and launch this thing that may not even make it all the way there intact.  

We are a species of explorers.  Our ancestors traveled the globe and colonized nearly every part of it.  We are no strangers to taking risk, and thinking big when it comes to wondering what’s over the next hill or beyond the distant horizon.  Human consciousness first awakened on this planet on the continent of Africa, and from there spread to all corners of the world, from stone age Europe and Asia, and over the frozen Bering Straits of the last Ice Age, into North and South America.  Early humans even sailed across the forbidding oceans to Australia and the Pacific islands.  We have adventure in our blood.  

Pluto the most distant target that we have tried, so far, to reach out and touch.  Not a journey that humans, with laughably fragile bodies susceptible to harm from radiation and microgravity, and entirely too needy for food, oxygen, warmth, and even companionship, can make anytime soon.  Instead we send our stoic little robot ambassador out on a entirely peaceful mission of scientific discovery.  It represents the best part of humanity with no thought whatsoever to invasion, conquest, or exploitation of new territory for gain or profit.  It represents what’s best in us – our childlike curiosity, enthusiasm for discovery, and sense of awe at living in a universe that is so much bigger than our everyday concerns.  

Going to Pluto inspires us to be great by doing great things.  It is no trivial task to design, build, and implement a machine to do what New Horizons is doing right now.  That’s, of course, why it has never been done before.  The accuracy necessary for the mission to reach its target, and the durability of its components to remain functional after 9 years in the cold vacuum of space, are a triumph of human engineering and understanding of Newtonian mechanics.  The challenge of the mission elevates us up onto a more noble plane.  Teams of individuals made the mission possible, but also the millions of taxpayers that contributed to a successful human achievement, are all part of the process that show we as a society care about things beyond the mundane and everyday.  We are all apart of the mission, and we all have a right to see what New Horizons can tell us about the edge of our cosmic neighborhood block.  

Going to Pluto also inspires curiosity in the unknown.  From earth, even from the Hubble Space Telescope, Pluto is not much more than a dim dot in the night sky.  We want to know, what is it like on Pluto?  Why is it so different than the planets like the Earth, Mars, Jupiter, and so on?  What is it made of and why is its orbit around the sun so unusual?  Does it hold clues to the formation of the solar system and the planets?  Could it hold clues to the origins of life’s chemical building blocks that lead to our own origins on earth?  We humans really want to know the answers to things.  When we have a real mystery it inspires a lot of careful thinking, formulation of hypotheses, and ideas about how to test those hypotheses.  Being curious is one of our most outstanding traits as a species.  Far from the old adage “curiosity killed the cat” in reality, curiosity is how we learn who we are, where we come from, and what our place in the universe really is.  “Curiosity killed the cat” is meant to keep us afraid and in the dark.  Curiosity keeps us moving forward, but the spirit of curiosity is easily doused by others who are perfectly satisfied by not knowing and who have long ago lost their curiosity.  We need to keep that spark of curiosity alive.  Not only is a mission like New Horizons the scratch to satisfy the itch of our innate curiosity, but it inspires new levels of curiosity in those sharing in the discoveries, and in the imaginations of young people who then begin thinking about what is next out there to explore.

There are also the unforeseen consequences from a mission like New Horizons.  It is not why these missions are undertaken, but we have reaped the benefits of the collateral developments (the opposite of collateral damage) of basic science research before.  From the World Wide Web developed by theoretical physicists at CERN, to advances in computer and laser technology, basic science research has provided benefits to society at large that were never predicted or expected.  When Nobel prize winning physicist, Edward Purcell was asked what practical applications his discovery of nuclear magnetic resonance in bulk matter could ever be used for, which he developed to better understand the quantum transition of hydrogen atoms from one energy state to another, his answer was, “I can see no practical applications”.  It turned out that this discovery changed modern life giving us Magnetic Resonance Imaging (MRI) in medicine to peer into the living body in exquisite detail, as well as transforming the field of chemistry with Nuclear Magnetic Resonance (NMR) which has revolutionized our understanding of molecular structure and material science.  The truth is that we don’t always know what the final impact of fundamental research may be for our everyday lives.  The knowledge we gain from studying Pluto might help us better understand the threat of comets and asteroids to life on planet earth, and perhaps aid in our survival as a species.  The most likely benefit will be ones we don’t see coming at all.   There are also economic gains that programs, such as the space program provide to our country, as far as more jobs, and it signals to the world our national strengths and that intellectual endeavors are an important priority.  Being a leader in science and space exploration is no small thing in the eyes of the rest of the world.  

Missions like New Horizons remind us that we live in a much bigger universe than we are used to thinking about.  On a day to day basis, it’s easy to focus on the minor details, to think your little neighborhood is all there is.  We don’t look up at the night sky and observe the stars very often- not nearly enough.  Going to Pluto forces us to think about our place in the cosmos.  The solar system is big and the planets are far away.  How much bigger is our galaxy than the solar system, and what about the billions of distant galaxies?  We are not just in the universe, the universe is in us.  We are a part of the universe and it’s good to be reminded of that from time to time.

I’ve waited a long time for today.  I don’t know what pictures and information will be sent back to earth by our little robotic probe as it speeds past Pluto, but I know it will be amazing.  Just to know that something of earth is out there, so far from home and continuing its flight outward into the galaxy, is pretty cool in itself.  And once New Horizons leaves Pluto behind, there will continue to be new and exciting discoveries to anticipate, some from future robotic space missions, others from telescopic observatories examining the universes largest structures, and still others from basic science research facilities like CERN examining the universes smallest components and fundamental forces.  We will continue to have a lot to learn and look forward to so long as we as a society continue to decide that the nobel pursuit of new knowledge is a goal worth achieving.  For today, I just want to say, “Hello Pluto, it’s great to finally meet you”.

References:

1. NASA New Horizons website.

https://www.nasa.gov/mission_pages/newhorizons/main/index.html

2. Pluto:  Wikipedia

https://en.wikipedia.org/wiki/Pluto

3. Cylde Tombaugh:  Wikipedia

https://en.wikipedia.org/wiki/Clyde_Tombaugh

4.  Pluto Safari is a cool app you can down load on your tablet from iTunes.