We tend to think of science as exact, measurable, certain. Well, that isn’t always the case. Scientists are constantly testing theories, re-checking Einstein’s findings, questioning the old and the new.
We think everything is tested and known, right? I got to thinking about three great scientists and their theories about what we don’t know. In some ways, it might be greater than what we do know.
Heisenberg
So, let’s start off with one of my favorites, Heisenberg’s Uncertainty_principle. It is more of a realization than a theory, really. Werner Heisenberg (1901 – 1976) was a German theoretical physicist and a pioneer in the field of quantum mechanics. He was one of Germany’s premier scientists attempting to develop the atomic bomb for Hitler during World War II (he and his team came close). But he also made major contributions in the fields of “hydrodynamics of turbulent flows, the atomic nucleus, ferromagnetism, cosmic rays and subatomic particles,” according to Wikipedia.
Simply put, his Uncertainty Principle states that the more precisely we know a particle’s exact position, the less we can know about its momentum. And vice versa. Although we are talking about sub-atomic particles, let’s go real-world here, just to get a handle on it. If we have a marble rolling down a ramp, we can measure its exact location at any one point in time but because it is accelerating, it makes it difficult to measure both speed and location at the same time, since they are both simultaneously changing.
We can also think of this as a car speeding down the highway at 90 MPH. The state trooper’s radar catches us at 90 and pulls us over. We get a speeding ticket with a reading of 90 but no exact location. Sure, the ticket says you were “caught” on Highway 10 at mile marker 230.4 but it does not specify the exact location. This is because he or she got your exact speed but not your exact location at the point of infraction.
It is difficult to know where an object is when it is moving through a plane. Motion and location are indeterminate. Instead of looking at this as a problem, look at it as an epiphany.
Fermi
One day in 1950, Enrico Fermi, an Italian American physicist, went to lunch with a few other scientists. After a discussion about UFOs, he asked “Where is everyone?” The outline of his argument (known as fermi-paradox) goes like this (cosmosmagazine.com, 1/13/22):
- The Milky Way (just one galaxy among trillions of others) contains hundreds of billions of stars, and billions are similar to our sun.
- Highly likely that some of these stars will have planets similar to Earth.
- Intelligent life should exist on some fraction of the Earth-like planets.
- Some intelligent life forms could develop advanced technology and even interstellar travel.
- Interstellar travel is extremely time-consuming but since so many stars are billions of years older than our sun, there has been plenty of time for such travel to have occurred.
- Given all this, why haven’t we met or seen any trace of aliens? Where is everybody?
Drake
Then there is Frank Drake, known for the drake-equation. To narrow it down, we need to estimate the number of civilizations we could communicate with. It is used to estimate the number of active, communicative extraterrestial civilisations in our Milky Way Galaxy.
The Drake formula is:
N = R* x Fp x Ne x Fl x Fi x Fc x L
N = number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone); and
R* = average rate of star formation in our galaxy
Fp = the fraction of those stars that have planets
Ne = the average number of planets that can potentially support life per star that has planets
Fl = the fraction of planets that could support life that actually develop life at some point
Fi = the fraction of planets with life that actually go on to develop intelligent (civilizations)
Fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space
(credit: en.wikipedia.org/wiki/Drake_equation)
Wow, that was easy. Where do you even begin? Pull numbers out of thin air? As you study the formula, you realize it is a constant winnowing down of the starting estimate, R*: a whole number reduced to fractions of fractions.
Most conservative estimates produce a total number less than one. Meaning we are alone in the Milky Way.
And the Habitable Zone (or the Goldilocks area), where a planet’s distance from its star allows liquid water to exist on its surface, will greatly vary based on the intensity/size of the sun and the distance to the planet. This would be identified in the Drake formula as Ne.
But according to Astronomy magazine 2018, Drake’s original estimates were between 20 at the low end and 100,000,000 at the upper end, based on different assumptions.
As one could imagine, estimates (and criticisms of the formula) are all over the place. I found a great website where you can see the equation in action:
www.spacecentre.nz/resources/tools/drake-equation-calculator.html
It allows you to see how the number can change as you change any of the criteria.
Fortunately, we had the Kepler Space Telescope (retired by NASA in October, 2018 when it ran out of fuel) which discovered 2,600 exoplanets. Hubble and other satellites and telescopes are constantly updating our known planet database. As of January 30, 2022, NASA reports 4,908 confirmed exoplanets in the Milky Way with more being discovered every year.
So we really are quite uncertain if life even exists outside of Earth in our own galaxy. Outside of that, we still wonder if life could be somewhere in the universe. But as Fermi asked, where are they? And we’re not even certain of a marble’s location once we ascertain its speed.
Granted, the universe is enormous and the distances between stars is enormous. According to MIT Technology Review (by Emerging Technology from the arXiv, 6/22/18) it would take us 6,300 years to reach the closest star to our sun, Proxima Centauri, 4.2 light years away traveling at today’s fastest technology of 434,960 mph, which is the speed the Parker Solar Probe will reach. The planet near that star is Proxima b, a possible habitable world.
But the distance between galaxies is almost unfathomable to consider. According to Lawrence M. Krauss and Glenn D. Starkman, in The Distance Scale of the Universe, published 2020, the average distance between galaxies is 1,000,000 light years. It would require that many light years to communicate just one-way. Two-way communication would require more than double that since it would take some time to decode and come up with an appropriate response to, “Is anybody out there?”
I’m uncertain that my WiFi connection will work today. Who will win the Super Bowl? Did Tom Brady really retire? How can we possibly know the answers to the universe?
So we may have uncertainty but we inch closer to the truth. We will get clarity but I don’t expect to get these answers in my lifetime. It is still fascinating to wonder and speculate how close we will ever get to answering the truly big questions.
Chris Ebel
1/30/22
Image credit: @immrchris