Let's face it: to think that the universe has a history that started with a kind of birthday some 13.8 billion years ago is weird. It resonates with many religious narratives that posit that the cosmos was created by divine intervention, although science has nothing to say about that.
What happened before time began?
If everything that happens can be attributed to a cause, what caused the universe? To deal with the very tough question of the First Cause, religious creation myths use what cultural anthropologists sometimes call a "Positive Being," a supernatural entity. Since time itself had a beginning at some point in the distant past, that First Cause had to be special: it had to be an uncaused cause, a cause that just happened, with nothing preceding it.
Attributing the beginning of everything to the Big Bang begs the question, "What happened before that?" That's a different question when we are dealing with eternal gods, as for them, timelessness is not an issue. They exist outside of time, but we don't. For us, there is no "before" time. Thus, if you ask what was going on before the Big Bang, the question is somewhat meaningless, even if we need it to make sense. Stephen Hawking once equated it with asking, "What's north of the North Pole?" Or, the way I like to phrase it, "Who were you before you were born?"
To ask from science to "explain" the First Cause is to ask science to explain its own structure. It's to ask for a scientific model that uses no precedents, no previous concepts to operate. And science can't do this, just as you can't think without a brain.
Saint Augustine posited that time and space emerged with creation. For him, it was an act of God, of course. But for science?
Scientifically, we try to figure out the way the universe was in its adolescence and infancy by going backward in time, trying to reconstruct what was happening. Somewhat like paleontologists, we identify "fossils" — material remnants of long-ago days — and use them to learn about the different physics that was prevalent then.
The premise is that we are confident that the universe is expanding now and has been for billions of years. "Expansion" here means that the distances between galaxies are increasing; galaxies are receding from one another at a rate that depends on what was inside the universe at different eras, that is, the kinds of stuff that fill up space.
The "Big Bang" was not an explosion
When we mention the Big Bang and expansion, it's hard not to think about an explosion that started everything. Especially since we call it the "Big Bang." But that's the wrong way to think about it. Galaxies move away from one another because they are literally carried by the stretch of space itself. Like an elastic fabric, space stretches out and the galaxies are carried along, like corks floating down a river. So, galaxies are not like pieces of shrapnel flying away from a central explosion. There is no central explosion. The universe expands in all directions and is perfectly democratic: every point is equally important. Someone in a faraway galaxy would see other galaxies moving away just like we do.
(Side note: For galaxies that are close enough to us, there are deviations from this cosmic flow, what's called "local motion." This is due to gravity, The Andromeda galaxy is moving toward us, for example.)
Going back in time
Credit: Andrea Danti / 98473600 via Adobe Stock
Playing the cosmic movie backward, we see matter getting squeezed more and more into a shrinking volume of space. Temperature rises, pressure rises, things break apart. Molecules get broken down into atoms, atoms into nuclei and electrons, atomic nuclei into protons and neutrons, and then protons and neutrons into their constituent quarks. This progressive dismantling of matter into its most basic constituents happens as the clock ticks backward toward the "bang" itself.
For example, hydrogen atoms dissociate at about 400,000 years after the Big Bang, atomic nuclei at about one minute, and protons and neutrons at about one-hundredth of a second. How do we know? We have found the radiation left over from when the first atoms formed (the cosmic microwave background radiation) and discovered how the first light atomic nuclei were made when the universe was merely a few minutes old. These are the cosmic fossils that show us the way backward.
Currently, our experiments can simulate conditions that happened when the universe was roughly one trillionth of a second old. That seems like a ridiculously small number for us, but for a photon — a particle of light — it's a long time, allowing it to travel the diameter of a proton a trillion times. When talking about the early universe, we must let go of our human standards and intuitions of time.
We want to keep going back as close to t = 0 as possible, of course. But eventually we hit a wall of ignorance, and all we can do is extrapolate our current theories, hoping that they will give us some hints of what was going on much earlier, at energies and temperatures we cannot test in the lab. One thing we do know for certain, that really close to t = 0, our current theory describing the properties of space and time, Einstein's general theory of relativity, breaks down.
This is the realm of quantum mechanics, where distances are so tiny that we must rethink space not as a continuous sheet but as a granular environment. Unfortunately, we don't have a good theory to describe this granularity of space or the physics of gravity at the quantum scale (known as quantum gravity). There are candidates, of course, like superstring theory and loop quantum gravity. But currently there is no evidence pointing toward either of the two as a viable description of physics.
Physics' greatest mystery: Michio Kaku explains the God Equation | Big Think www.youtube.com
Quantum cosmology doesn't answer the question
Still, our curiosity insists on pushing the boundaries toward t = 0. What can we say? In the 1980s, James Hartle and Stephen Hawking, Alex Vilenkin, and Andrei Linde separately came up with three models of quantum cosmology, where the whole universe is treated like an atom, with an equation similar to the one used in quantum mechanics. In this equation, the universe would be a wave of probability that essentially links a quantum realm with no time to a classical one with time — i.e., the universe we inhabit, now expanding. The transition from quantum to classical would be the literal emergence of the cosmos, what we call the Big Bang being an uncaused quantum fluctuation as random as radioactive decay: from no time to time.
If we assume that one of these simple models is correct, would that be the scientific explanation for the First Cause? Could we just do away with the need for a cause altogether using the probabilities of quantum physics?
Unfortunately, not. Sure, such a model would be an amazing intellectual feat. It would constitute a tremendous advance in understanding the origin of all things. But it's not good enough. Science can't happen in a vacuum. It needs a conceptual framework to operate, things like space, time, matter, energy, calculus, and conservation laws of quantities like energy and momentum. One can't build a skyscraper out of ideas, and one can't build models without concepts and laws. To ask from science to "explain" the First Cause is to ask science to explain its own structure. It's to ask for a scientific model that uses no precedents, no previous concepts to operate. And science can't do this, just as you can't think without a brain.
The mystery of the First Cause remains. You can choose religious faith as an answer, or you can choose to believe science will conquer it all. But you can also, like the Greek Skeptic Pyrrho, embrace the limits of our reach into the unknowable with humility, celebrating what we have accomplished and will surely keep on accomplishing, without the need to know all and understand all. It's okay to be left wondering.
Curiosity without mystery is blind, and mystery without curiosity is lame.
Does the universe keep extending endlessly into the abyss of space, or does it have a defined end?
Of all the scientific questions you may ponder, "Is the universe infinite?" is one of the hardest. It is impossible to answer with certainty at this point. Scientists have proposed both possibilities, and each has its own supporters and detractors. Determining whether the universe has some kind of boundary ultimately depends on figuring out its shape, size, and how much of it we can actually observe.
Is the universe infinite? And what shape is it?
The shape of the universe would have a lot to do with its size. Cosmologists have theorized that a universe would likely come in one of three possible shapes, which are dependent on the curvature of space. As described in Discover Magazine, the universe could be flat, having no curvature, but spatially infinite. Or it could be open, shaped like a saddle (with negative curvature) and also infinite. Or it could be closed, look like a sphere, and be spatially finite.
So which shape really is it? Nobel Prize-winning cosmologist John Mather of NASA's Goddard Space Flight Center, also the chief scientist for the James Webb Space Telescope, maintains that recent observations of cosmic microwave background radiation (CMB) remaining from the time of the Big Bang support the idea of the universe being flat, without any curvature (at least to the limit of what is observable).
"The universe is flat like an [endless] sheet of paper," shared Mather. "According to this, you could continue infinitely far in any direction and the universe would be just the same, more or less."
The geometry of the universe is determined by the density parameter Ω within cosmological Friedmann Equations.Credit: NASA / WMAP Science Team
Measuring the size of the universe
Current calculations say that the observable universe extends 46.5 billion light-years in every direction, making its diameter 93 billion light-years across.
Consider this: The age of the universe is 13.8 billion years, which means it took 13.8 billion light-years for the light from the farthest edge of the observable universe to reach us. But in that time, the universe has continued to expand at a rate that appears to be speeding up. Now, the edge of the observable universe has moved and is 46.5 billion light-years away.
That vast amount of space includes anywhere from 200 billion to 2 trillion galaxies, according to varying estimates. And each galaxy has, on average, around a 100 billions stars.
These gargantuan numbers are almost impossible to grasp. How did scientists come up with them?
As shared in an interview with BBC by Caitlin Casey, an astronomer at the University of Texas at Austin, scientists use a variety of tools and methods called "the cosmic distance ladder" to estimate distances between objects in the vastness of space. They start out with distances they can actually measure directly, like through bouncing radio waves off nearby bodies in the solar system, noting the time required for the waves to come back to Earth.
For distances that are harder to gauge, like those for galaxies at the boundary of the universe, astronomers utilize inferences based on calculations and observational evidence.
For instance, they employ "parallax measurement" that relies on measuring a star's shift in relation to objects in its background, as well as "main sequence fitting," which takes advantage of our knowledge of stellar evolution. (Stars evolve over time, changing size and brightness.) Knowledge of how brightness is connected to distance is paramount in determining the location of distant objects. So is analysis of redshift, which involves measuring changes in the wavelengths of light coming from faraway galaxies.
What about the unobservable universe?
If you notice, the numbers above pertain to the observable universe, the ball-like part of the universe that can be somehow seen from Earth or detected using our space telescopes and probes. But what about parts of the universe we cannot see? Some portions of the universe may be just too far away for the light emitted after the Big Bang to have had sufficient time to reach us here on Earth.
One study from a group of UK scientists estimated that if you take that into account, the actual size of the universe could be at least 250 times larger. They found that if you refer to space in terms of a so-called Hubble volume, which is similar to the volume of space in the visible universe, a closed and finite universe would contain roughly 250 to 400 Hubble volumes.
Another possibility entertained by scientists like Nobel Prize-winning Roger Penrose is that the Big Bang was just one of the periods of cosmic regeneration that our universe has experienced. There could have been multiple Big Bangs, followed by Big Crunches, periods in which a universe would stop expanding and collapse upon itself.
If all we know about the universe is derived from how it expands after the latest Big Bang, the questions if the universe is infinite or what size it may be are almost moot. As is often the case, more study and confirmation of our theories is needed.
Is there an edge to the universe?
Whether we have a finite universe or an infinite universe like an ever-expanding bubble, does it still have an "edge"? Is there some place you can go and say, "Yep, this is the end of the universe"? The simple answer is likely no.
As explained to LiveScience by Robert McNees, an associate professor of physics at Loyola University Chicago, the universe is isotropic. That means it follows the so-called "cosmological principle" and has the same properties and follows the same laws of physics in all directions.
If that is so, then the universe is much like the surface of a balloon. Imagine being an ant walking along a balloon. You wouldn't know there's an edge to it if you kept walking forward. You'd likely come back to where you started eventually, but the journey around and around could keep going without end.
If someone were to blow more air into the balloon as you keep walking along it, you'd experience some parts of the balloon moving farther away from you. Still, you'd be no closer to finding the balloon's edge.
Much like the ants, we're unlikely to get to the end of the universe. But we may still be able to answer one day "is the universe infinite" or does it have an actual boundary?
Recently published research pushes the boundaries of key concepts in quantum mechanics. Studies from two different teams used tiny drums to show that quantum entanglement, an effect generally linked to subatomic particles, can also be applied to much larger macroscopic systems. One of the teams also claims to have found a way to evade the Heisenberg uncertainty principle.
One question that the scientists were hoping to answer pertained to whether larger systems can exhibit quantum entanglement in the same way as microscopic ones. Quantum mechanics proposes that two objects can become "entangled," whereby the properties of one object, such as position or velocity, can become connected to those of the other.
An experiment performed at the U.S. National Institute of Standards and Technology in Boulder, Colorado, led by physicist Shlomi Kotler and his colleagues, showed that a pair of vibrating aluminum membranes, each about 10 micrometers long, can be made to vibrate in sync, in such a way that they can be described to be quantum entangled. Kotler's team amplified the signal from their devices to "see" the entanglement much more clearly. Measuring their position and velocities returned the same numbers, indicating that they were indeed entangled.
Tiny aluminium membranes used by Kotler's team.Credit: Florent Lecoq and Shlomi Kotler/NIST
Evading the Heisenberg uncertainty principle?
Another experiment with quantum drums — each one-fifth the width of a human hair — by a team led by Prof. Mika Sillanpää at Aalto University in Finland, attempted to find what happens in the area between quantum and non-quantum behavior. Like the other researchers, they also achieved quantum entanglement for larger objects, but they also made a fascinating inquiry into getting around the Heisenberg uncertainty principle.
The team's theoretical model was developed by Dr. Matt Woolley of the University of New South Wales. Photons in the microwave frequency were employed to create a synchronized vibrating pattern as well as to gauge the positions of the drums. The scientists managed to make the drums vibrate in opposite phases to each other, achieving "collective quantum motion."
The study's lead author, Dr. Laure Mercier de Lepinay, said: "In this situation, the quantum uncertainty of the drums' motion is canceled if the two drums are treated as one quantum-mechanical entity."
This effect allowed the team to measure both the positions and the momentum of the virtual drumheads at the same time. "One of the drums responds to all the forces of the other drum in the opposing way, kind of with a negative mass," Sillanpää explained.
Theoretically, this should not be possible under the Heisenberg uncertainty principle, one of the most well-known tenets of quantum mechanics. Proposed in the 1920s by Werner Heisenberg, the principle generally says that when dealing with the quantum world, where particles also act like waves, there's an inherent uncertainty in measuring both the position and the momentum of a particle at the same time. The more precisely you measure one variable, the more uncertainty in the measurement of the other. In other words, it is not possible to simultaneously pinpoint the exact values of the particle's position and momentum.
Heisenberg's Uncertainty Principle Explained. Credit: Veritasium / Youtube.com
Quantum skepticism
Big Think contributor astrophysicist Adam Frank, known for the 13.8 podcast, called this "a really fascinating paper as it shows that it's possible to make larger entangled systems which behave like a single quantum object. But because we're looking at a single quantum object, the measurement doesn't really seem to me to be 'getting around' the uncertainty principle, as we know that in entangled systems an observation of one part constrains the behavior of other parts."
Ethan Siegel, also an astrophysicist, commented, "The main achievement of this latest work is that they have created a macroscopic system where two components are successfully quantum mechanically entangled across large length scales and with large masses. But there is no fundamental evasion of the Heisenberg uncertainty principle here; each individual component is exactly as uncertain as the rules of quantum physics predicts. While it's important to explore the relationship between quantum entanglement and the different components of the systems, including what happens when you treat both components together as a single system, nothing that's been demonstrated in this research negates Heisenberg's most important contribution to physics."
The papers, published in the journal Science, could help create new generations of ultra-sensitive measuring devices and quantum computers.Sometimes, when you are looking for something ordinary, you find the unexpected. This is definitely the case with the strange 'Oumuamua, which made international headlines as a potential interstellar visitor. Its true identity remained obscure for a while, as scientists proposed different explanations for its puzzling behavior. This is the usual scientific approach of testing hypotheses to make sense of a new discovery.
What captured the popular imagination was the claim that the object was no piece of rock or comet, but an alien artifact, designed by a superior intelligence.
Do you remember the black monolith tumbling through space in the classic Stanley Kubrick movie 2001: A Space Odyssey? The one that "inspired" our ape-like ancestors to develop technology and followed humanity and its development since then? What made this claim amazing is that it wasn't coming from the usual UFO enthusiasts but from a respected astrophysicist from Harvard University, Avi Loeb, and his collaborator Shmuel Bialy. Does their claim really hold water? Were we really visited by an alien artifact? How would we know?
A mystery at 200,000 miles per hour
Before we dive into the controversy, let's examine some history. 'Oumuamua was discovered accidentally by Canadian astronomer Robert Weryk while he was routinely reviewing images captured by the telescope Pan-STARRS1 (Panoramic Survey and Rapid Response System 1), situated atop the ten-thousand-foot Haleakala volcanic peak on the Hawaiian island of Maui. The telescope scans the skies in search of near-Earth objects, mostly asteroids and possibly comets that come close to Earth. The idea is to monitor the solar system to learn more about such objects and their orbits and, of course, to sound the alarm in case of a potential collision course with Earth. Contrary to the objects Weryk was used to seeing, mostly moving at about 40,000 miles per hour, this one was moving almost five times as fast — nearly 200,000 miles per hour, definitely an anomaly.
Hyperbolic trajectory of ʻOumuamua through the inner Solar System.Credit: nagualdesign / Tomruen / JPL Horizons via Wikipedia and licensed under CC BY-SA 4.0
Intrigued, astronomers tracked the visitor while it was visible, concluding that it indeed must have come from outside our solar system, the first recognized interstellar visitor. Contrary to most known asteroids that move in elliptical orbits around the sun, 'Oumuamua had a bizarre path, mostly straight. Also, its brightness varied by a factor of ten as it tumbled across space, a very unusual property that could be caused either by an elongated cigar shape or by it being flat, like a CD, one side with a different reflectivity than the other. The object, 1I/2017 U1, became popularly known as 'Oumuamua, from the Hawaiian for "scout."
In their paper, Loeb and Bialy argue that the only way the object could be accelerated to the speeds observed was if it were extremely thin and very large, like a sail. They estimated that its thickness had to be between 0.3 to 0.9 millimeters, which is extremely thin. After confirming that such an object is robust enough to withstand the hardships of interstellar travel (e.g., collision with gas particles and dust grains, tensile stresses, rotation, and tidal forces), Loeb and Bialy conclude that it couldn't possibly be a solar system object like an asteroid or comet. Being thus of interstellar origin, the question is whether it is a natural or artificial object. This is where the paper ventures into interesting but far-fetched speculation.
I'm not saying it was aliens, but it was aliens
First, the authors consider that it might be garbage "floating in interstellar space as debris from advanced technological equipment," ejected from its own stellar system due to its non-functionality; essentially, alien space junk. Then, they suggest that a "more exotic scenario is that 'Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization," [italicized as in the original] concluding that a "survey for lightsails as technosignatures in the solar system is warranted, irrespective of whether 'Oumuamua is one of them."
You can shoot down as many hypotheses as you want to vindicate yours, but this doesn't prove yours is the right one.
I have known Avi Loeb for decades and consider him a serious and extremely talented astrophysicist. His 2018 paper includes a suggestive interpretation of strange data that obviously sparks the popular imagination. Theoretical physicists routinely suggest the existence of traversable wormholes, multiverses, and parallel quantum universes. Not surprisingly, Loeb was highly in demand by the press to fill in the details of his idea. A book followed, Extraterrestrial: The First Sign of Intelligent Life Beyond Earth, and its description tells all: "There was only one conceivable explanation: the object was a piece of advanced technology created by a distant alien civilization."
It came from outer space.Credit: Scott Barbour via Getty Images
This is where most of the scientific establishment began to cringe. One thing is to discuss the properties of a strange natural phenomenon and rule out more prosaic hypotheses while suggesting a daring one. Another is to declare to the public that the only conceivable explanation is one that is also speculative. An outsider will conclude that a reliable scientist has confirmed not only the existence of extraterrestrial life but of intelligent and technologically sophisticated extraterrestrial life with an interest in our solar system. I wonder if Loeb considered the impact of his words and how they reflect on the scientific community as a whole.
This is why aliens won't talk to us
Earlier this year, in a live public lecture hosted by the Catholic University of Chile, Avi Loeb locked horns with Jill Tarter, the scientist that is perhaps most identifiable as someone who spent her career looking for signs of extraterrestrial intelligence. (Coincidentally, I was the speaker that followed Loeb the next week in the same seminar series and was cautioned — along with the other panelists — to behave myself to avoid another showdown. I smiled, knowing that my topic was pretty tame in comparison. I mean, how can the limits of human knowledge compare with alien surveillance?)
The Loeb-Tarter exchange was awful and, it being a public debate, was picked up by the press. Academics can be rough like anyone else. But the issue goes deeper.
What scientists say matters. When should a scientist make public declarations about a cutting-edge topic with absolute certainty? I'd say never. There is no clear-cut certainty in cutting-edge science. There are hypotheses that should be tested more until there is community consensus. Even then, consensus is not guaranteed proof. The history of science is full of examples where leading scientists were convinced of something, only to be proven wrong later.
The epistemological mistake Loeb committed was to make an assertion that publicly amounted to certainty by using a process of elimination of other competing hypotheses. You can shoot down as many hypotheses as you want to vindicate yours, but this doesn't prove yours is the right one. It only means that the other hypotheses are wrong. I do, however, agree with Loeb when he says that 'Oumuamua should be the trigger for an increase in funding for the search for technosignatures, a way of detecting intelligent extraterrestrial life.
