from Skeptics and True Believers by Chet Raymo. Page 47
Let this, then, be the ground of my faith: All that we know, now and forever, all scientific knowledge that we have of this world, or will ever have, is as an island in the sea [of mystery]…We live in our partial knowledge as the Dutch live on polders claimed from the sea. We dike and fill. We dredge up soil from the bed of mystery and build ourselves room to grow. And still the mystery surrounds us. It laps at our shores. It permeates the land. Scratch the surface and mystery bubbles up like a spring. And occasionally, at certain disquieting moments in history (Aristarchus, Galileo, Planck, Einstein), a tempest of mystery comes rolling in from the sea and overwhelms our efforts, reclaims knowledge that has been built up by years of patient work, and forces us to retreat to the surest, most secure core of what we know, where we huddle in fear and trembling until the storm subsides, and then we start building again, throwing up dikes, pumping, filling, extending the perimeter of our knowledge and our security.
Knowledge is an island in a sea of mystery.
The Wonders of the Universe
I want to share a few of the recent discoveries in the field of astronomy. I’m not an astrophysicist and I’m not a cosmologist. I like to observe and I like to teach. I’ve been doing astronomy since my parents bought me a telescope when I was about 10 years old.
Along with these discoveries, I also want to share some mysteries that scientists are working on today. Scientists love mysteries. For Chet Raymo there is a sea of mysteries. We can find these mysteries both along the edge of our knowledge and the depth of our understanding.
To that end, I’d like to share some recent discoveries and some recently discovered mysteries. I’m not an expert in any of these specialties, I just love teaching about them. We’ll begin with the whole universe, shrink our way down to our galaxy, and end with our quest for life elsewhere.
Let’s first remember our address, where we find ourselves. We live in the system with one star, 8 planets and some other stuff. That solar system is in the Milky Way Galaxy. And our Galaxy is part of a cluster of about 50 galaxies bound by gravity. There are other clusters out there, near and far.
Finally there are clusters of clusters, we call them super clusters. These huge collections contain many clusters of galaxies, and those in turn contain many thousands of galaxies.
The universe has about 100 billion galaxies, and they are not evenly distributed. We see voids, with few galaxies, strands, sheets, and walls.
In 1929 Edwin Hubble discovered evidence that the universe is expanding. Yes, the universe is bigger today than it was yesterday.
There seems to be a tension between two opposing forces, 1) gravity and 2) expansion. In a cluster, the galaxies can be relatively close together, making the force of gravity strong between them and holding the cluster together.
The distance between one super cluster and another super cluster can be great and that, in turn, makes gravity so weak that instead of gravity binding them together, the clusters are flying apart from one another.
In 1998 astronomers, using variable stars and supernova as standard candles, discovered that the expansion wasn’t slowing down, but was in fact speeding up. The universe is getting bigger faster today than it was yesterday.
In June 2016 astronomers working with the Hubble Space Telescope observed evidence that the expansion rate is even faster than they thought.
The universe is expanding 45 miles of new space per second per mega parsec. For every 20 billion-billion miles of space, expansion adds 45 miles of new space every second. This makes the distant superclusters become even more distant.
We’ve claimed a little more knowledge about our universe. Using Raymo’s analogy we’ve built some extra space on the island of knowledge. But when we scratch the surface, a mystery bubbles up.
Why is the universe accelerating in the first place? If we have an explosion on Earth, the pieces will fly away but gravity and friction will eventually slow the expansion and finally stop it.
What’s making the expansion rate of the universe accelerate?
We don’t know. Einstein hinted at it, and we still don’t know what this force is, but today we call it dark energy.
Just last year Gravity Waves were detected for the first time. The announcement described the detection of waves in the fabric of space-time and explained that the waves were caused by the merger of two black holes.
This physics is way above my pay-grade so please let me tell you that Gravity Waves are rooted in Einstein’s Theory of General Relativity. Gravity Waves may provide a completely different way to observe the universe.
From what scientists could tell, there’re two basic types of black holes.
Our galaxy has gas and dusk with the stars making a disk, and we have in the core a super massive black hole (SMBH). This massive object is about 4 million times the mass of our Sun and any star or planet that gets too close will fall in and never come back.
By definition, we cannot see black holes. They have so much matter packed so densely you would have to go faster than the speed of light to escape. Since nothing can go faster than the speed of light, nothing can leave a black hole. not even light.
So how do we detect something we can’t see? We can do this by the pull of gravity it’s mass has! Here’s an animation of six stars observed near the center of the Milky Way Galaxy. What are they orbiting?
Our SMBH is equivalent to about 4 million Suns! And we can’t see it! Physicists are working on a couple different scenarios that might explain how these monsters developed.
The other kind of black hole has been the solar mass black holes. These are just a few times the mass of the Sun, mostly around 5 to 10 solar masses, but sometimes up to about 20 solar masses. Black holes are sometimes created as the final stage of a very massive star.
When a massive star runs out of fuel in the core, the very center, exciting events begin to happen quickly. Inside the star, the outward pressure caused by nuclear fusion stops and gravity pulls the upper layers of the star and they fall hard onto the core. These layers then rebound out into space in what we call a supernova explosion.
Some supernova explosions obliterate the whole star, recycling all those elements into space. And some supernova leave a lump several times the mass of our sun that is so dense, it disappears from our vision.
So we had solar mass black holes and SMBHs.
Putting celestial objects into categories is one of the things scientists do. We look for similarities and differences between like objects. This helps us understand. We’ve claimed a few more feet of island ground. Our island of knowledge has gotten a bit larger, but still, look at the shore and out over the sea, and we see that we’re surrounded by mystery.
The detection of gravity waves also ushered in another discovery. If our understanding of physics is correct and our observations are accurate, the two black holes that merged to cause these first gravity waves were a new class of object. They were each about 30 solar masses!
More massive than stellar black holes and less massive than SMBH, these Intermediate mass black holes are an exciting discovery.
Let’s go back to the SMBHs in the center of galaxies. It appears every galaxy has one.
Galaxies have a collection of stars gas and dust, sometimes in a spiral shapes, and galaxies have a SMBH.
And scientists began to wonder, which came first, the SMBH or the stars and gas and dust?
Sort of like the chicken and the egg question, which came first? Did a SMBH form first, and then it gathered a collection of stars and gas and dust around it? Or did a disk of stars give birth to the SMBH? We don’t know… Scratch the surface and we have … a mystery!
In 2009 NASA began the Kepler mission. Kepler is a space telescope dedicated to finding planets in orbit around other stars in a very small section of the sky.
Scientists working with the Kepler telescope have confirmed 2,000 new planets and have almost 5,000 more candidates to study.
Just yesterday (July 23, 2016) NASA announced that the planet K186f, about 500 Light Years away, is both Earth-sized and in the habitable zone. That means it’s massive enough to hold onto gas (an atmosphere?) and close enough to its star to have liquid water on its surface.
One thing we’ve learned is that almost every star has at least one planet.
Most of the new exoplanets are larger and more massive than the Earth. Probably not good for live as we know it.
Some of these planets are Earth-size. NASA Just announced that they found that one of these Earth-size planets is in the habitable zone, where water could exist as a liquid.
In our solar system, one of the eight planets has life, maybe intelligent life, but certainly life that has developed technology to communicate. That’s one planet out of 8, or 12 %. Now 12% of these 2,000 confirmed Kepler-telescope planets is 240.
And the nearest of the Kepler-telescope planets is only about 12 Light Years away. That means that any kind of electromagnetic radiation (light, X-rays, radio waves) would take 12 years to san the distance one-way. So right about now they should be catching the last season of “Friends” and the first season of “House.”
If our solar system is not that unusual, there ought to be about 240 communicating civilizations among these first 2,000 confirmed planets.
Where are they? If there are probably so many communicating civilizations out there, why haven’t we picked up their radio or TV shows? Why aren’t we watching their version of House?
Maybe they don’t want us to know they’re out there. If they are picking up our radio and TV news programs, maybe they’ve had second thoughts about revealing themselves.
Or maybe we’re looking wrong. After all, we’ve just detected gravity waves. Maybe we are searching incorrectly. Could it be that we haven’t developed that technology yet?
Or maybe we happen to be the first to advance this far. After all, someone has to be first. But I doubt it. The odds are against us being the first civilization advanced enough to make telescopes. We probably aren’t first.
The sea of mystery surrounds us. Lapping at our shore of knowledge are mysteries. We observe and ask more questions.
What is Dark Energy?
Which formed first in the Milky Way Galaxy, the collection of stars or the SMBH?
And where is ET?
The structure of our universe is called the Cosmic Web. And, as Carl Sagan said, “we are a way the universe can know itself.”
In astronomy we learn a few things and we think of more questions to ask. So we have more mysteries. Could the detection of gravity waves be the next “tempest of mystery” that will force us to rewrite our paradigms, re-think our theories and rebuild our models?
I think of Sir Isaac Newton’s Third Law of Motion, that for every action there’s an equal and opposite reaction. When that light from the planet, star, or galaxy comes through my telescope, it will exit through the eyepiece and touch my eye. If there’s an equal and opposite reaction, I’m touching back.
Maybe when we look, and observe, and think about these objects we are showing respect. When we try to understand a small part of it, maybe we’re showing respect.
I hope you will too. Every clear Friday the Cline Observatory on the Jamestown campus of GTCC is open to the public. I invite you to come out and respectively touch the universe with us.
Thank-you for allowing me to share a few mysteries with you.
As surely as we belong to the universe
we belong together.
We join here to transcend the isolated self,
to know ourselves to be at home,
here on earth, under the stars,
linked with each other
By The Rev. Margaret Ada Keip (UU minister emeritus, Carmel California)