Tag Archives: multiverse

Horizons Out of Reach

Imagine you are walking on a terrain of rolling hills; in the distance you can see the horizon. Beyond that point you don’t know what you’ll find. When you arrive at the crest of a hill a whole new landscape appears with its own horizon. This is a common metaphor used to show how knowledge is usually acquired. Each horizon reached often presents another horizon (or question) in the distance.

The story of science is one of impressive discoveries. Many horizons have been reached, but many more are yet to be encountered. No one knows how far we can go and what we will find. I hesitate to limit what might be possible, because science has surprised us time and time again. If the human race survives long enough, is there anything we can’t find out? I would think that there are some questions we will not be able to answer, but which ones? One should think long and hard before ruling anything out, which I have done. For what it’s worth, I am left with two questions which appear out of reach. I’ll get back to this later but first a little context.

Horizons Reached

At present the knowledge base is immense, but it had to be acquired. Imagine going back 100, 500 or 1,000 years and contemplating the future. It’s possible that some future discoveries could have been predicted. However, there are other findings that few saw coming. It is practically impossible to provide a full account of impressive scientific discoveries. However, there are some that immediately stand out. What follows has been mentioned in prior blogs of mine; think of it as a short list of scientific highlights:

  1. The Idea of Natural laws: At around 500 BC the ancient Greeks documented the concept of natural laws. They suggested that patterns in nature could be recognized and attributed to natural laws. This was a major breakthrough in scientific thought.
  2. The Copernican Revolution: In 1543 Nicolaus Copernicus published his theory of the heliocentric model of the universe. He removed the Earth from the center of the known universe and replaced it with the Sun. This was a significant reality check, which would influence human philosophy for years to come.
  3.   Newton’s Laws: In 1687 Isaac Newton disclosed his law of universal gravitation and his three laws of motion. Newton laid the foundation for what later became known as classical physics. Now over 300 years later, Newton’s equations still apply (except for extreme circumstances).
  4. Einstein’s Relativity: With special relativity (in 1905) and general relativity (in 1915), Albert Einstein filed in the gaps in Newton’s laws. Einstein accounted for those extreme circumstances. His contribution led to a greater understanding of the large-scale universe.
  5. Darwin’s Theory of Evolution: Charles Darwin provided an explanation for how all life evolves with his famous publication in 1859. This one basically speaks for itself; few if any discovery is more impressive.
  6. Revealing the Atomic and Subatomic Realm: Beginning in the early 1900s, several people worked on theories such as quantum mechanics and the standard model of partial physics. A realm previously inaccessible was shown to be real and would unwittingly have a significant impact on human affairs.
  7. The Big Bang: In the 1931 George Lemaitre suggested that the universe began in a single geometric point. He arrived at this by applying general relativity to the observations of William Hubble. Lemaitre`s idea would eventually provide us with a truly universal origin story. 
  8. DNA: In 1962 James Watson, Francis Crick and Maurice Wilkins won a Nobel Prize in medicine for the discovery of the structure of DNA. This opened up a whole new science, which will undoubtedly impact us for generations.

Of course the list above could be significantly longer and still fall short. However, I present it just to give you a feel for how knowledge, particularly scientific knowledge, alters our perception of the world. It is debatable how many past discoveries could have been foreseen; nonetheless one can imagine some horizons in the distance which may be attainable. For example: figuring out how life on Earth began, or the discovery of life elsewhere in the universe. Closer to home, there is finding a cure for cancer (or most cancers), and maybe even weather forecasting weeks or months in advance. No one knows for sure which findings are coming, but I feel fairly certain that at least two questions will remain unanswered.

Contemplating the Unanswerable

The two questions I am referring to are as follows: 1) Why is there a universe in the first place?  2) Why is the universe the way it is and not some other way? Another question which I feel I must address before moving on to question 1, is this: Why is there something rather than nothing? You’ve probably heard this one before, and it is similar to question 1. However, I find it to be a peculiar question and here’s why. First let’s define what is meant by nothing. If by nothing, one assumes the absence of everything, then nothing is a non-entity. In other words, how can nothing be a reality if by definition nothing has no existence. The question gives us two options, something or nothing and it seems to me that something is real and nothing is not. By this logic one could conclude that there has to be something, but why a universe?

For some the existence of the universe doesn’t seem to be a big problem to solve. The standard answer is that God created the universe and that’s it. However, I can’t help but ask two simple follow-up questions: a) Why is there a God in the first place? b) Why is God the way he (she, it) is and not some other way? Do you see how this works, by inserting God as the explanation for the universe we’ve circled back to where we started. In essence the questions are identical. We have merely moved the starting point from the universe to God.

Another approach is to examine the possibility of a multiverse. There are scientific reasons that suggest that other universes may exist, but that is as far as it goes.  Although the multiverse is theoretical, it may shed light on question 2. Why is the universe the way it is and not some other way? If multiple universes actually exist, it could be that all possible universes exist, therefore it is not surprising that at least one universe is like ours. Although the multiverse idea is somewhat satisfying on the surface, it has its problems. For starters, it does not address question 1. Why is there a universe in the first place? It says nothing on why there would be a multiverse in the first place.

There is also the problem of testing the multiverse idea scientifically. How can we ever verify something outside the boundaries of our vast universe? Hypothetically, even if our science advanced to a point where universes outside our own could be detected, how could we know the full-scale of a multiverse? We would likely be unable to determine how many universes exist in total. Ultimately that’s where I think the multiverse idea falls short in terms of answering question 2. Why is the universe the way it is and not some other way? If we can’t know how many universes exist in total, we can’t explain why our universe is the way it is and not some other way. All possible universes have to exist in order for the multiverse to the job. Or at the very least, it would take an extremely high number of universes.

Why is there a universe in the first place and why is the universe the way it is and not some other way? I have thought about these two questions philosophically, religiously and scientifically and have made little progress. Each approach gains momentum only to fall short. There are undoubtedly still many horizons within our reach and it will be interesting to see what lies ahead. That being said, I have to conclude that there are at least two horizons that seem to be hopelessly out of reach.





The Anthropic Principle

the astronomerWhy are we here? This is perhaps the most fundamental philosophical question. One can imagine contemplating this question at any time in human history. Many stories have been inspired by this question, usually taking the form of myths, or religious and spiritual traditions. Today, ‘why are we here’ is also a scientific question. The anthropic principle arose as a response to the question of human existence. The idea was first proposed in 1973 by theoretical astrophysicist Brandon Carter. Since then it has been expanded and stated in several forms.

What is the Anthropic Principle?

The word anthropic is defined by the Merriam-Webster online dictionary as: “Of or relating to human beings or the period of their existence on Earth.” That’s a start. For simplicity I will stick close to Brandon Carter’s original formulation, which he expressed as two variants. I will paraphrase based on the description from a few sources:

  1. The Weak Anthropic Principle refers to our special location in the universe (both in time and space), which is conducive to our existence. The fact that we can observe the universe means that planet Earth must have the conditions necessary for our existence.
  2. The Strong Anthropic Principle refers to the fundamental laws of physics, which are precisely set for our existence. The strong principle takes into account the properties of the universe as a whole.

The Burden of Proof

habitable zoneIn a vast universe it is not surprising that a planet, like the Earth, has a special location (usually called a habitable zone or a Goldilocks zone). The specific laws of the universe needed for human life are more difficult to explain (usually called fine tuning). Using a legal metaphor, the strong anthropic principle has a greater burden of proof than the weak anthropic principle. In this case, burden of proof is a figure of speech, because the anthropic principle is as much a philosophical idea as a scientific one. 

In The Grand Design, Stephen Hawking and Leonard Mlodinow describe the weak anthropic principle as an environmental factor. They write:

“Environmental coincidences are easy to understand because ours is only one cosmic habitat among many that exist in the universe, and we obviously must exist in a habitat that supports life”

The strong anthropic principle is all-encompassing and generally more controversial. Hawkings and Mlodinow go on:

“The strong anthropic principle suggests that the fact that we exist imposes constraints not just on our environment but on the possible form and content of the laws of nature themselves”

Stating the Obvious or a Profound Insight

Is the anthropic principle a satisfying explanation? On the surface, it seems like an obvious statement that explains very little. But as I reflect on the idea, I am not so sure. Maybe it is suggesting something profound. Perhaps the answer to why we are here is simple: it could not be otherwise.

Lawrence KraussFor example, Lawrence Krauss provides an anthropic interpretation to one of the universe’s properties. In the book, A Universe from Nothing, he examines the relationship between the energy density of matter and the energy density of empty space. Yes, space has energy and it can be measured. The density of matter in the universe can also be measured. It turns out that now is the only time in cosmic history that both values are comparable. That’s a curious result.

The universe has been expanding since the big bang, and as it expands the density of matter decreases. Matter gets diluted as galaxies get farther apart from each other. Meanwhile the energy in empty space remains constant (there is nothing to dilute or increase in empty space). Therefore at the time galaxies formed the density of matter was greater than the energy in empty space. That’s a good thing, because the gravitational effect of matter was dominant, which allowed matter to come together.

However, if the values for matter and energy had been comparable at the epoch of galaxy formation, galaxies would not have formed. Empty space exerts a repulsive force, which would have canceled out normal attractive gravity. Matter would not have clumped together. Krauss writes in A Universe from Nothing:

“But if galaxies hadn’t formed, then stars wouldn’t have formed. And if stars hadn’t formed, planets wouldn’t have formed. And if planets hadn’t formed, then astronomers wouldn’t have formed!”

It seems highly coincidental that the energy values for matter and space are roughly equal now, but they could not have equalized too much earlier. Otherwise, no one would be here to observe it. Similarly, if one of a number of physical properties were slightly different, we would also not be here. That’s when anthropic reasoning steps in: An observer must observe the conditions of the universe that allows the observer to exist.

astronomersMaybe a change of perspective is needed: Instead of focusing on our present circumstances and looking back, we can look at the evolution of the universe. Life is a latecomer to the process, of which an incalculable series of events occurred. Our existence is the result of all that came before. Although it does appear that the universe was made for us, it is in fact, the universe that made us. We were formed from the conditions that were set long before conscious beings could observe any of it.

Is Physics an Environmental Science?

The traditional approach of physics is to discover and understand the universe we live in. The fundamental laws and the values for the constants of nature are consistent throughout the observable universe. The physical laws discovered on Earth can be applied to the universe as a whole. But there can only be one exact set of laws and history that allow for our existence. That’s unless our universe is not the only one.

For some, recent scientific evidence is suggesting that there are many universes (a multiverse). Others point out that inferring a multiverse is not science; because by definition other universes cannot be observed directly (they would exist outside our observable universe). If we apply the strong anthropic principle to the multiverse theme, it does partly explain the exact parameters of our universe.

If the cosmos is populated with many universes, possibly infinite universes, then the laws of physics could be purely random. They would simply emerge as an environmental consequence. Some physicists have compared the multiverse to a foam of bubbles (each bubble representing a universe). The laws could be different in every bubble of an endless cosmic foam. Some bubble universes could be similar to ours, others vastly different.

Of course, this is a hypothetical argument. Nevertheless, if we could observe every universe in a multiverse, every single one would be finely tuned for its own existence. Anthropic reasoning would state that there is nothing special about our universe. In all the non-life generating universes there is no one to observe them, in ours there is. It’s that simple. Obviously, the anthropic principle (inferring a multiverse or not) is not a proven argument, but it’s one of many possible answers to the question: Why are we here?


References: Stephen W. Hawking and Leonard Mlodinow, The Grand Design (New York: Bantam Books, 2010), 155.

Lawrence M. Krauss, A Universe from Nothing (New York: Free Press, 2012).


Nature’s Fine Tuning and the Multiverse

numbersThere are a number of fundamental physical constants of nature, in which their values seem to be finely tuned. Examples of  such constants are: the speed of light, the strength of gravity, the mass of the elementary particles, and the strength of the atomic forces. The fine-tuning angle comes into play when one considers the exact parameters of the constants. Hypothetically, if one were to adjust the values just a little bit, the universe would be vastly different. This fact alone does not present a problem. However, physicists have noted that minor changes to the values of the constants would not allow life to develop. It is as if the universe knew we were coming, or is it?

The values of the physical constants are critical for giving our universe the structure that it has. For example: the precise strength needed to hold the atomic particles together in stable arrangements, and the gravitational force needed to clump matter into stars and planets. If the strength of gravity was slightly weaker, matter in the early universe would have spread apart too quickly; thus preventing stars from forming. Conversely, if the gravitational force was a little stronger, matter would have come together too quickly and everything would have collapsed. It is clear to scientists that gravity, as well as other values, could not be adjusted very much without erasing the possibility for life.

The Most Extreme Fine Tuning

Although the apparent fine tuning of the constants demand an explanation, nothing compares to the level of fine tuning of one particular constant. This is called the cosmological constant (also called dark energy), and it represents the value of the energy in empty space. The cosmological constant is believed to exert an outward force, which is causing the universe to expand at an accelerated rate. In 1998, the value of the cosmological constant was measured by two teams of astronomers. The number they came up with is extremely small, a decimal point followed by 122 zeros and a one (measured in Planck units).

The energy in empty space, represented by the cosmological constant, is only relevant at the largest of scales. As the universe expands the amount of space is also increasing, thus increasing the effect of the dark energy. But in the distant past when the universe was much smaller, the total energy in space would have produced a far lesser effect. And here is the catch. If the outward push of the cosmological constant was slightly larger by a few decimal points, it would have counteracted the pull of gravity too quickly. This would have prevented stars, planets and galaxies from forming. In this scenario life would not exist.

By removing just a few zeros from an already small value, a universe suitable for life would disappear. Physicists are at a loss to explain why the number is so small and so finely tuned for our existence. In addition, the value of the cosmological constant revealed by observations is far less that what theory predicts. That is, the theory of the microscopic realm (quantum mechanics) predicts that the energy in empty space should be much larger. The mismatch between theory and observation does not sit well with physicists, as it shows that there is something missing with this picture.

Possible Solutions

The specific values of the physical constants require an explanation. Some people will look for a metaphysical solution. This will usually imply a creator for the universe who setup the constants for a purpose. The word God is the preferred choice, and it suggests that the universe was planned for our existence. Yet for others, crediting God for designing the universe in a special way is a non-explanation. One would still have to explain where God came from and why he was there in the first place.

Another line of reasoning would be to accept that mere chance accounts for the constants. But given the amount of fine tuning, this seems akin to winning a lottery with an infinite number of combinations. Chance alone is not a very satisfying solution. There is also the possibility that we don’t have enough information to solve the problem. Maybe a deeper understanding of the laws of physics is needed, and someday physicists will find the answer.

 The Multiple Universe Proposal

multiverseThe word universe has traditionally been used to describe all that exists. However, cutting-edge physics is requiring that a change of perspective is needed. Through a variety of physical discoveries the idea of multiple universes is being considered. The words parallel universes, parallel worlds, alternate universes, multiverse and others are being used. In the multiple-universe theme, the word universe has a slightly different meaning. Universe no longer means all there is, but rather means a region of a larger cosmos that is separated from other regions.

Physicist and science writer Brian Greene states, in The Hidden Reality, why the concept of multiple universes is compelling:

” The subject of parallel universes is highly speculative. No experiment or observation has established that any version of the idea is realized in nature… That said, I find it both curious and compelling that numerous developments in physics, if followed sufficiently far, bump into some variation on the parallel-universe theme.”

Although not yet experimentally tested, having large numbers of universes (possibly infinite) could explain the fine tuning of the physical constants. The logic is simple. With many universes, with different possible values for the constants, it is likely that one has the values we observe. Therefore, it is not surprising that we find ourselves in a universe that allows life. In the universes that have conditions that don’t allow life, there is no one to observe them, no one to say that they are not finely tuned for life.

As Brian Greene suggested, there are several theories in physics that imply a multiverse. The reasoning is technical, though I will list a few examples, which point to the possibility of a multiverse:

  • Eternal Cosmological Inflation: The extreme burst of spatial expansion at the early moments of the universe is known as inflation. Inflation is a cosmological principle, which in theory could happen anywhere, thus giving rise to multiple big bangs.
  •  A Spatially Infinite Cosmos: By inferring an infinite expanse of space-time, there is a limit to ways particles of matter can be arranged. Conditions in one location would eventually have to repeat somewhere else, creating parallel universes.
  •  The Extra Dimensions of String Theory: String theory proposes that at the tiniest of scales there exist extra spatial dimensions. It also states that there are many possible shapes for the extra dimensions of space. However, string theory cannot determine which of the shapes corresponds to our universe. If string theory is correct, the different possible shapes for these extra dimensions could be realized in different universes.
  • The Many-Worlds Interpretation of Quantum Mechanics: The atomic/subatomic realm is governed by randomness and understood using probabilities. Interpretations can vary. The many-worlds interpretation states that all the possible outcomes associated with quantum mechanical probabilities really happen, resulting in parallel worlds.

parrallel universeNot all the multiple universe proposals would yield different values for the constants. Some would produce exact replicas of our universe, or very close copies. Hence the term parallel universe. Yet other proposals would allow for different laws of physics or different values for the constants. These could be universes that are totally foreign and barely recognizable to us.

Whether we live in one of multiple universes is anyone’s guess. Presently, there is no known method that could observe them. Nevertheless, there are plenty of cases where physical theories or mathematics have pointed toward a phenomenon in nature, even before it was observed. And then at some later date, observations confirmed the theory. Therefore, if modern physics is suggesting the existence of a multiverse, it provides an interesting argument for the fine tuning of the physical constants of nature.


References: Brian Greene, The Hidden Reality (New York: Alfred A. Knopf, 2011), 8, 9.

Leonard Susskind – Is the Universe Fine-Tuned for Life and Mind? (Closer to Truth), Published on Jan 8, 2013. https://www.youtube.com/watch?v=2cT4zZIHR3s

 The Fabric of the Cosmos – Universe or Multiverse (Published on July 16, 2014) https://www.youtube.com/watch?v=ib0RNqVusoU