On Our New Picture of the Galaxy & the Likelihood of Alien Life
In the last few years, exoplanet research has painted a completely new picture of the galaxy. This picture radically changes our expectations of what is out there and, in fact, turns our old expectations on its head.
- As of 2020, about 18% of all sun-like stars have an Earth-like planet in the habitable zone, featuring liquid water [1].
- 0.6% of all planets we have discovered have been identified to be more suitable for the evolution of life than the Earth (super habitable planets).
- On average, every star has at least 1 planet of some kind.
Many people tend to say: “The universe is sooo huge, there must be life!”
This common phrase is an example of our old expectations. If someone has to invoke the entire universe, they do not yet know how abundant planets are as of right now.
In fact, you don’t even need to invoke our galaxy. We can just look at our immediate interstellar neighborhood. How many planets are in our vicinity? Does exoplanet research make extraterrestrial civilizations in our proximity likely? Should we begin to expect them? Let’s find out.
The Number of Habitable Worlds
The Milky Way galaxy is about 100,000 light-years (Ly) across. Let’s look at our backyard and estimate the number of stars within 50 and 1000 light-years from Earth in the following way.
There are about 512 sun-like stars within 100 Ly. Sun-like stars are called yellow dwarfs or G-type stars and make up about 7% of all stars in the galaxy. So within 100 Ly, we can estimate there are
\frac{512}{0.07} \, \approx \, 7314 \, stars.
However, the galactic disc is around 2000 ly thick and the Orion Spur (where we are) is 10,000 ly wide. That means as long as we stay within the Orion Spur, we can say the density of stars is about constant since all those stars are in the same spiral arm structure and not separated by empty space between the spiral arms. So it makes sense to average if we are just looking within 1000 ly radius around the sun. If we go further, we are going above and below the galactic disc.
The number of stars in a sphere with a radius of R light years is then:
\frac{512}{0.07} \cdot \left(\frac{R}{100\, Ly}\right)^3
For R = 1000 Ly this means there are about 7.3 million total stars and 512,000 G-type stars.
For a snuggly R = 50 Ly we estimate 914 stars and 64 G-type stars.
Since every star has at least 1 planet on average, there are 7.3+ million planets in 1000 Ly and 914+ planets within 50 Ly.
Remember, 18% of all G-type stars have an Earth-like planet in the habitable zone and 0.6% of all planets are more habitable than the Earth.
This means we have
- 92,160 habitable planets around G-type stars and 43,885 super habitable planets within 1000 Ly.
- 11 to 12 habitable planets around G-type stars and 5 to 6 super habitable planets within 50 Ly.
Super habitable planets (the ones better suited for life than the Earth) are especially expected around K-type stars. These are orange dwarfs, less massive and luminous than our sun. It turns out that our sun is not the nicest star to have because it produces a lot of ultraviolet light that damages DNA and thus hampers life from forming sooner. K-type stars produce much less ultraviolet light and are overall gentler. They also live many times as long as G-type stars, allowing ample amounts of time for life to arise.
At 13% abundance, K-type stars are about twice as common as G-type stars. We are currently not aware of how many Earth-like planets we can expect per K-type star (if you know, please reach out), so let’s assume it’s just half that of G-type stars (to make sure we rather under- than overestimate!). This means we can just about double the number of expected planets for G and K-type stars together.
The photo below shows 200,000 stars. This is also about the number of habitable planets we can expect within just 1000 light-years.
We have only had this new understanding since 2020. It’s time to update our expectations.
As we can see from this, even our immediate cosmic neighborhood is filled with vast amounts of planets (and moons).
Can Aliens Find Us?
Suppose an alien civilization existed within this radius of 1000 Ly. Would they know us already?
New stars form continuously and the first ones that could have planets began forming as early as 10 billion years ago. Our sun is only about 4.6 billion years old. The clock on most other planets started long before ours, which means the rise of lifeforms and civilizations is not even a race.
As you can see, cosmic time is so vast that alien lifeforms are very unlikely to arise at nearly the same time, so they must be hundreds of thousands or millions of years older. Given the number of planets, we can expect many life-baring planets and civilizations, but each one has to have arisen far apart in time, say, a million years between each one. Two species being at the same level of development like we depict in science fiction is highly unlikely.
They’ve had time and we are late to the game of life. A planet that formed 9 billion years ago could have had complex animal life by the time the Earth just started forming.
Given the new fundamental theory on UAP propulsion, UAPs can move at least close to light speed. This means that a civilization in our backyard only needs to build 7.3 million probes and send each to another star. Within 1000 years, all of the stars in this radius would be reached, scanned by the probes, and another 1000 years later they return home. Within 2000 years, a civilization in our back yard would have discovered every single planet and biosphere in that radius, including ours.
Note that 2000 years is nothing compared to the hundreds of thousands or millions of years that they would have been around by now. This leads us to a fundamental rule when thinking about extraterrestrial civilizations.
Everything has already happened. Everything we can imagine out there has already taken place eons ago. If they exist, they have always known the Earth and every other biosphere of which ours is only one.
The New Picture of The Galaxy
The Milky Way has 150 – 400 billion stars. Let’s take 200 billion so we don’t overestimate.
Since every star has at least one planet, that makes at least 200 billion planets in the galaxy.
7% of those planets are around G-type stars and 18% of them are habitable. That makes 2.5 billion planets.
13% of those planets are around K-type stars and (our guess from before) 1/2 of 18% of them are habitable. That makes 2.34 billion planets.
0.6% of all planets are more habitable than the Earth: 200 billion x 0.006 = 1.2 billion super habitable planets.
A few billion habitable planets have existed much longer than Earth, giving these planets more time to produce life.
A Brief History of Earth and The Likelihood of Complex Life
Many of my fellow scientists say that microbial life is probably everywhere – but no complex life. This is a common misconception and due to a missing piece of knowledge. Fungi are the bridge between microbes and complex life that barely anyone studies. Mycology, the study of fungi, is a field of research that is completely underfunded and underappreciated, yet it deals with the most important organisms of all time. They are so important that we should call the Earth a fungal ocean world, not an ocean world.
Let us fill this gap in knowledge a little.
Life on Earth began when it was only ~200 million years old. This was the first moment life could have started as the time before was the formation of the Earth. Since life started immediately, its formation is common and hence scientists say that microbes are probably everywhere. Back then, the Earth was just bedrock, acidic water, and it was surrounded by poisonous gasses. It was habitable but not beautiful and got terraformed by microbes and fungi.
The following numbers aren’t exact and have been subject to change over the years as they are difficult to determine and different methods yield different results. The point, however, is not accuracy but to give a simplified overview of how things progressed here and how they can progress on other planets.
- Microbes formed around 4.28 billion years ago and began terraformation of the ocean and atmosphere [1].
- Our earliest fossils of fungal-like structures date back 2.4 billion years ago [2].
- ~1.5 billion years ago, fungi as we know them today evolved from their fungal-like ancestors.
- ~1 billion years ago, the first sea-based animals split from fungi.
- ~0.5 to 1 billion years ago, fungi colonized land. They spread over the land and formed the first layer of soil. The exact time is very unclear due to gaps in the fossil record.
- ~460 to 500 million years ago, plants & animals colonize the land [3]
Fungi are simple strands of cells that form network structures. Due to their simplicity, they arise very easily and thus early, as seen on Earth. Evolution will easily optimize that network structure into a mathematical optimum.
Fungal networks are like an internet of fibers that penetrate all the soils of Earth. They are externalized lifeforms. They digest food and breathe oxygen externally via their billions of endpoints. Each endpoint is constantly probing the molecules it is in contact with, checking whether it is a food source or a pathogen. Whenever it can do anything with a molecule and there is a chemical reaction, this information goes back into the network and the network becomes educated. They are self-learning and have been demonstrated in the laboratory to have cellular intelligence.
They are externalized stomachs, externalized lungs, externalized neurological structures, tenacious, and have achieved their final forms before plants even existed. The oldest fossils of umbrella-like mushrooms are more than 800 million years old.
Animals are the opposite archetype. We are internalized lifeforms, surround our lungs, stomachs, and neurological net in tissue. We put food and oxygen inside of us because we are mobile platforms that move around the landscape rather than being part of the landscape itself.
Evolution will inevitably explore both of these types of lifeforms.
Animals split from fungi, likely in the form of some piece of the network that wormed around in the ocean. Since it was born from a mathematically optimized network structure, it was easy to evolve a simple nervous system to control that proto-body. Eventually, this became all the animals. We are fungal bodies and walk around the lands without noticing it. Our systems of blood vessels and the brain were born from this network archetype. It did not need to evolve from scratch because we already split from it. Plants used to be a marginal thing at the edge of the water before fungi terraformed the bedrock, making all the soils, providing essential minerals, and allowing life to spread across the landmasses into large ecosystems. Fungi are the real terraformers.
Complex intelligent animal life arose from an organism that is simple and arises easily.
This means that complex animal life is as likely as the evolution of fungal networks themselves if given enough time.
What’s more, the fungal network does not need light and uses heat and radiation as an energy source. This enables them to protect the biosphere against asteroid impacts. We have had several such impacts. Each time, debris gets launched into the atmosphere that blocks the sunlight and causes a nuclear winter and mass extinction. But the fungi gobble up the forests and whatever else passes away and provides nutrition to every lifeform that lives in close symbiosis with the fungal network.
It is as though a big sieve was swept over the Earth, removing everything that is not in symbiosis. This is why life on Earth today all leans on each other. Every species, in one way or another, needs every other species, like books on a shelf that hold each other in place. This intimate symbiotic web encompasses the species that made it through the asteroid impact events. Plants don’t even exist by themselves, as there are hundreds of species of fungi that grow inside of them – all the way into the leaves. Life on Earth is a complex intertwined web of symbiosis.
Fungi form easily, terraform the land, split into animals, and protect the biosphere from catastrophe. This is the history of life on Earth we now know.
Going back to my fellow scientists who say microbial life is probably everywhere but no complex life, we can see what the problem is. They are missing the bridge between microbes and complex life. Physicists are not mycologists.
Mycologists say that microbes and fungi are probably everywhere.
Conclusion
Considering G- and K-type stars, we end up with around 6 billion habitable planets, 1 billion of which are more habitable than our own. As our statistics from exoplanet research got better, these numbers have only ever increased, not decreased. It is likely they are going to continue to increase some more.
This does not take into account cooler stars like F-type, M-type, etc. And we also can’t estimate how many habitable moons there are. Gas giants like Jupiter can have moons the size of the Earth and they can be habitable as well. Our solar system has at least 5 moons with liquid water oceans where we can expect at least microbial life to exist. How many moons with an atmosphere and land masses might there be? There is no way to know right now. But since we have over 200 moons in our system, it is safe to say there are suitable moons in large numbers. If a Jupiter-like planet was in the habitable zone of its star, its moons can have liquid water on the surface.
Consider the large number of worlds, life on Earth forming immediately, and the easy formation of fungal networks that birth animals. We see that with our new data of the galaxy and knowledge of the history of life on Earth, the existence of vast numbers of worlds with complex animal life is not unlikely anymore. It only used to be unlikely when we had no data. The chance for alien life in the galaxy has actually turned on its head from near zero to near certain. And that near-certainty is not just for one planet or moon with complex life but large numbers of them. The public and even most scientists have not had time to update their views and expectations, as most people are not aware of this new understanding.
We cannot continue to expect ourselves to be alone given this data. To continue arguing our old view means to argue an option with a near-zero chance of being correct.