Category Archives: Universe Mysteries

Illustration of cosmic expansion showing galaxies spreading apart over time in the universe.

How Is the Universe Going to End?

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At the begging of the Twentieth Century, almost every scientist believed the universe was eternal. That is to say, the universe always was and always will be—it is static. In the context of an eternal universe, questions about a beginning or an ending are meaningless. By definition, an eternal universe has no beginning, and it will have no ending. This is what they taught our grandparents as schoolchildren. Overall, the eternal universe found acceptance in both science and religion. Science proclaimed that the universe simply existed, with no evidence to the contrary. Religious leaders simply proclaimed God made the universe, which seems to imply the universe had a beginning. However, since science had no evidence to the contrary, science and religion did not butt heads over this. At the turn of the Twentieth Century, science and religion appeared content with their assertions of the universe. Poetically, you might say all was well in heaven and on Earth.

A little over eighty years ago, our cosmic bubble of an eternal universe was shattered. In 1929, Edwin Hubble,  using the 100-inch Hooker telescope at the Mount Wilson Observatory, discovered that extremely distant galaxies are moving away from us. Indeed, he discovered the farther away the galaxy, the higher the apparent velocity it is moving away from us. Therefore, a galaxy twice as far from us is moving away at twice the speed of a galaxy half the distance from us. Hubble noted that the universe was expanding in all directions. This was a profound discovery that caught the greatest scientific minds of the time, including Einstein, off guard. Prior to Hubble’s discovery, the prevalent theory held by the scientific community was that the universe was in a steady state, not expanding or contracting. Even though, the evidence was mounting before Hubble conclusively proved the universe was expanding, most scientists held strongly to their paradigm of a steady-state universe.

Surprisingly, Hubble was not the first to discover the universe was expanding. In 1912, Vesto Slipher measured the first Doppler shift (the length of a light wave) of spiral galaxies, and discovered that almost all spiral galaxies were receding from Earth. Unfortunately, not much attention was paid to Slipher’s findings. Slipher himself did not understand the implications of his discovery. In addition, telescopes in 1912 were relatively poor quality, and the nature of what he was measuring was not clearly understood as spiral galaxies. In fact, the term that was used to describe spiral galaxies in 1912 was “spiral nebula” (an indistinct bright patch).

Einstein’s equations of general relativity also predicted the universe was expanding. However, Einstein was convinced that this prediction was wrong and modified the equations by adding the “cosmological constant.” With this newly added mathematical expression, the equations of general relativity predicted a static universe. Later, though, as the evidence that the universe was expanding become incontrovertible, Einstein labeled his “cosmological constant” his greatest blunder. in fact, Starting with Hubble’s discovery of an expanding universe in 1929, within thirty-five years, most of the scientific community did a complete reversal, turning their backs on a static universe and now embracing an expanding universe.

As scientists began to think about an expanding universe, they reasoned that eventually gravity would play into the equation, halt the expansion, and even reverse it. In other words, up to 2008, mainstream science believed that the expansion of the universe would eventually be slowed by gravity, then halted, and gravity would pull everything back together in what science termed a “Big Crunch.” However, when the expansion of the universe was measured in 1998, by Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess, a startling discovery was made. The expansion was not slowing down. It was accelerating. Gravity did not appear to be playing a prominent role. In fact, a new and unknown force, termed “dark energy,” seemed to be in charge. This new force, dark energy, is still a mystery.

You may wonder at this point, what this all have to do with how the universe will end? Based on all known data, the accelerated expansion of the universe implies that eventually all galaxies will move away from us to the point they are beyond our cosmological horizon. We will no longer be able to see them. The Milky Way galaxy, the galaxy that is home to our planet Earth, will be completely alone. Eventually, all stars in the Milky Way galaxy, including our Sun, will exhaust their fuel and burn out. The Earth, itself, will be long gone by by the time the galaxy grows completely dim. Our Sun will eventually burn out in approximately five billion years. How long will it take for the Milky Way galaxy to to simply be reduced to cold remnants of rubble and dust? No one really knows. Most scientists agree it will take many billions of years, but no one knows the exact number of billions. Some theories calculate the end of the universe, but they hold little sway in mainstream science. All we know is that the universe is 13.8 billion years old, which suggests change on a cosmological scale moves slowly. The end is likely many billions of years in the future, but there is little doubt the universe will end and any remnants material, without stars to provide warmth, will be close or equal to absolute zero temperature. This may all sound like a grade B disaster movie. However, unlike many grade B disaster movies, this is real and doe not have a happy ending.

Close-up of an ornate astronomical clock with zodiac signs and intricate golden details.

Is Time Travel Possible?

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Few topics in science capture the imagination like time travel. Science fiction, like H. G. Wells’ classic novel, The Time Machine, published in 1895, and science fact, like time dilation, continues to fuel interest in time travel. Let us start with the most important question: Is time travel possible?

Of course, time travel is possible. We are already doing it. At this point, I know my answer may come across a bit flippant. However, my answer has a kernel of truth. We are traveling in time. We continually travel from the present to the future. This is what philosophers refer to as the arrow of time. In our everyday experience, it moves in one direction, from the present to the future. I think, though, on a more serious note, what people want to know is can we travel back in time—or to a future date in time.

In theory, it is possible. Indeed, numerous solutions to Einstein’s special and general relativity equations predict time travel is possible. In general, no law of physics prohibits time travel. We will begin by considering two methods science proposes to travel in time .

Method 1: Time Travel to the Future – Faster-than-light (FTL)

Using faster than light or near the speed of light, time travel appears to offer methodologies grounded in science fact. Consider two examples:

1) Assume you build a spaceship capable of traveling near the speed of light. With such a spaceship, you literally can travel into the future. This may sound like science fiction, but it is widely accepted as scientific fact. Particle accelerators confirm it. We discussed it when we discussed time dilation and the twin paradox. All you need is the spaceship, and an enormous amount of energy to accelerate it near the speed of light. However, this is an enormous problem. From Einstein’s special theory of relativity, we know that as we begin to accelerate a mass close to the speed of light, it becomes more massive, and approaches infinity. Thus, to accelerate it close to the speed of light, we need an energy source that approaches infinity. Perhaps we would have to learn how to harness the energy of a star, or routinely create matter-antimatter annihilations to create energy. Today’s science is nowhere near that level of sophistication.

2) Assume you can move information (like a signal) faster than light. Theoretically, if we could send a signal from point A to point B faster than the speed of light, it would represent a form of time travel. However, a significant paradox occurs. Here is an example.
An observer A in an inertial frame A sends a signal to an observer B in an inertial frame B. When B receives the signal, B replies and sends a signal back to A faster than the speed of light. Observer A receives the reply before sending the first signal.

In 1907, Albert Einstein described this paradox in a thought experiment to demonstrate that faster-than-light communications can violate causality (the effect occurs before the cause). Albert Einstein and Arnold Sommerfeld in 1910 described a thought experiment using a faster-than-light telegraph to send a signal back in time. In 1910, no faster-than-light signal communication device existed. It still does not exist, but the possibility of its development is increasing. From quantum physics, it appears that certain quantum effects “transmit” instantaneously and, therefore, appear to transmit faster than the speed of light in empty space. One example of this is the quantum states of two “entangled” particles (particles that have physically interacted, and later separated). In quantum physics, the quantum state is the set of mathematical variables that fully describes the physical aspects of a particle at the atomic level. When two particles interact with each other, they appear to form an invisible bond between them. When this happens, they become “entangled.” If we take one of the particles, and separate it from the other, they remain entangled (invisibly connected). If we change the atomic state of one of the entangled particles, the other particle instantaneously changes its state to maintain quantum-state harmony with the other entangled particle. Significant experimental evidence indicates that separated entangled particles can instantaneously transmit information to each other over distances that suggest the information exchange exceeds the speed of light. Initially, scientists criticized the theory of particle entanglement. After its experimental verification, science recognizes entanglement as a valid, fundamental feature of quantum mechanics. Today the focus of the research has changed to utilize its properties as a resource for communication and computation.

Method 2: Time Travel to the Past – Using Wormholes

Scientists have proposed using “wormholes” as a time machine. A wormhole is a theoretical entity in which space-time curvature connects two distant locations (or times). Although we do not have any concrete evidence that wormholes exist, we can infer their existence from Einstein’s general theory of relativity. However, we need more than a wormhole. We need a traversable wormhole. A traversable wormhole is exactly what the name implies. We can move through or send information through it.

If you would like to visualize what a wormhole does, imagine having a piece of paper whose two-dimensional surface represents four-dimensional space-time. Imagine folding the paper so that two points on the surface are connected. I understand that this is a highly simplified representation. In reality, we cannot visualize an actual wormhole. It might even exist in more than four dimensions.

How do we create a traversable wormhole? No one knows, but most scientists believe it would require enormous negative energy. A number of scientists believe the creation of negative energy is possible, based on the study of virtual particles and the Casimir effect.

Assuming we learn how to create a traversable wormhole, how would we use it to travel in time? The traversable wormhole theoretically connects two points in space-time, which implies we could use it to travel in time, as well as space. However, according to the theory of general relativity, it would not be possible to go back in time prior to the creation of the traversable wormhole. This is how physicists like Stephen Hawking explain why we do not see visitors from the future. The reason: the traversable wormhole does not exist yet.

Hard as it may be to believe, most of the scientific community acknowledges that time travel is theoretically possible. If fact, time dilation of subatomic particles provides experimental evidence that time travel to the future is possible, at least for subatomic particle accelerated close to the speed of light. Real science is sometimes stranger than fiction. What do you believe?

 

A vivid blue cosmic scene showing a bright star surrounded by glowing nebulae and countless distant stars.

What Is Dark Energy?

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Is dark energy real or simply a ghost story? Unfortunately, the phenomena we call dark energy is both real and scary. If it plays out on its current course, we are going to be alone, all alone. The billions upon billions of other galaxies holding the promise of planets with life like ours will be gone. The universe will be much like what they taught our grandparents at the beginning of the Twentieth Century. It will consist of the Milky Way galaxy. All the other galaxies will have moved beyond our cosmological horizon, and be lost to us forever. There will be no evidence that the Big Bang ever occurred.

Mainstream science widely accepts the Big Bang as giving birth to our universe. Scientists knew from Hubble’s discovery in 1929 that the universe was expanding. However, prior to 1998, scientific wisdom was that the expansion of the universe would gradually slow down, due to the force of gravity. We were so sure, so we decided to confirm our theory by measuring it. Can you imagine our reaction when our first measurement did not confirm our paradigm, namely that the expansion of the universe should be slowing down?

What happened in 1998? The High-z Supernova Search Team (an international cosmology collaboration) published a paper that shocked the scientific community. The paper was: Adam G. Riess et al. (Supernova Search Team) (1998). “Observational evidence from supernovae for an accelerating universe and a cosmological constant.” Astronomical J. 116 (3). They reported that the universe was doing the unthinkable. The expansion of the universe was not slowing down—in fact, it was accelerating. Of course, this caused a significant ripple in the scientific community. Scientists went back to Einstein’s general theory of relativity and resurrected the “cosmological constant,” which Einstein had arbitrarily added to his equations to prove the universe was eternal and not expanding. Previous chapters noted that Einstein considered the cosmological constant his “greatest blunder” when Edwin Hubble, in 1929, proved the universe was expanding.

Through high school-level mathematical manipulation, scientists moved Einstein’s cosmological constant from one side of the equation to the other. With this change, the cosmological constant no longer acted to keep expansion in balance to result in a static universe. In this new formulation, Einstein’s “greatest blunder,” the cosmological constant, mathematically models the acceleration of the universe. Mathematically this may work, and model the accelerated expansion of the universe. However, it does not give us insight into what is causing the expansion.

The one thing that you need to know is that almost all scientists hold the paradigm of “cause and effect.” If it happens, something is causing it to happen. Things do not simply happen. They have a cause. That means every bubble in the ocean has a cause. It would be a fool’s errand to attempt to find the cause for each bubble. Yet, I believe, as do almost all of my colleagues, each bubble has a cause. Therefore, it is perfectly reasonable to believe something is countering the force of gravity, and causing the expansion to accelerate. What is it? No one knows. Science calls it “dark energy.”

That is the state of science as I write this book in the latter half of 2012. The universe’s expansion is accelerating. No one knows why. Scientists reason there must be a cause countering the pull of gravity. They name that cause “dark energy.” Scientists mathematically manipulate Einstein’s self-admitted “greatest blunder,” the “cosmological constant,” to model the accelerated expansion of the universe.

Here is the scary part. In time, we will be entirely alone in the galaxy. The accelerated expansion of space will cause all other galaxies to move beyond our cosmological horizon. When this happens, our universe will consist of the Milky Way. The Milky Way galaxy will continue to exist, but as far out as our best telescopes will be able to observe, no other galaxies will be visible to us. What they taught our grandparents will have come true. The universe will be the Milky Way and nothing else. All evidence of the Big Bang will be gone. All evidence of dark energy will be gone. Space will grow colder, almost devoid of all heat, as the rest of the universe moves beyond our cosmological horizon. The entire Milky Way galaxy will grow cold. Our planet, if it still exists, will end in ice. How is that for a scary story?

A colorful simulation of cosmic web structure showing galaxies and dark matter distribution in the universe.

A New Theory of Dark Matter

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In my last post, “What Is Dark Matter,” I mentioned that most of the scientific community accepts the experimental evidence confirming the existence of dark matter. Rightly so, since the experimental evidence of its existence is incontrovertible. Here are the salient facts that experimentally indicate the existence and location of dark matter:

  • The rotation of stars, planets, and other celestial masses orbit galaxies, like ours, too rapidly relative to their mass and the gravitational pull exerted on them in the galaxy. For example, an outermost star should be orbiting slower than a similar-size star closer to the center of the galaxy, but we observe they are orbiting at the same rate. Based on this observation, the scientific community asserts there is more mass in the galaxy than we are able to observe. The call this mass dark matter.
  • We can see the effect dark matter has on light. It will bend light the same way ordinary matter bends light. This effect is gravitational lensing. The visible mass is insufficient to account for the gravitational lensing effects we observe. Once again, this suggests more mass than what we can see.
  • We are able to use the phenomena of gravitational lensing to determine where the missing mass (dark matter) is, and we find it is throughout galaxies. It is as though each galaxy in our universe has an aura of dark matter associated with it. We do not find any dark matter between galaxies.

While it is true that all evidence has led the scientific community to believes that dark matter is real and abundant, making up as much as 90% of the mass of the universe, its true nature is still a mystery. The current theory among the scientific community is that dark matter is  a slow-moving particle that travels up to a tenth of the speed of light, and neither emits nor scatters light. In other words, it is invisible.  Scientists call the mass associated with dark matter a “WIMP” (Weakly Interacting Massive Particle).

For years, scientists have been working to find the WIMP particle to confirm dark matter’s existence. All efforts have been either unsuccessful or inconclusive. This raises a significant question. Are we on the right track? Is there a WIMP particle? To address this question, let’s consider the experimental evidence:

  1. The Standard Model of particle physics does not predict a WIMP particle. The Standard Model, refined to its current formulation in the mid-1970s, is one of science’s greatest theories. It successfully predicted bottom and top quarks prior to their experimental confirmation in 1977 and 1995, respectively. It predicted the tau neutrino prior to its experimental confirmation in 2000, and the Higgs boson prior to its experimental confirmation in 2012. Modern science holds the Standard Model in such high regard that a number of scientists believe it is a candidate for the theory of everything. Therefore, it is not a little “hiccup” when the Standard Model does not predict the existence of a particle. It is significant, and it might mean that the particle does not exist.
  2. No evidence of the WIMP particle has surfaced from particle accelerator data, including data gather from experiments using the the Large Hadron Collider (LHC). This is particularly concerning since super colliders have successfully given us a glimpse into the early universe, the time frame from which most of the scientific community believes dark matter originated.
  3. To sum it up, all experiments to detect the WIMP particle have to date been unsuccessful, including considerable effort by Stanford University, University of Minnesota and Fermilab.

That is all the experimental evidence we have. Where does this leave us? The evidence is telling us the WIMP particle might not exist. We have spent over a decade, and unknown millions of dollars, which so far leads to a dead end. This appears to beg a new approach.

To kick off the new approach, consider the hypothesis that dark matter is a new form of energy. We know from Einstein’s mass-energy equivalence equation (E = mc2), that mass always implies energy, and energy always implies mass. For example, photons are massless energy particles. Yet, gravitational fields influence them, even though they have no mass. That is because they have energy, and energy, in effect, acts as a virtual mass.

If dark matter is energy, where is it and what is it? Consider these properties of dark-matter energy:

  • It is not in the visible spectrum, or we would see it.
  • It does not strongly interact with other forms of energy or matter.
  • It does exhibit gravitational effects, but does not absorb or emit electromagnetic radiation.

Based on these properties, we should consider M-theory (the unification of all string theories that mathematically suggests there may be ten spacial dimensions, not three, as well as a time dimension). Several prominent physicists, including one of the founders of string theory, Michio Kaku, suggest there may be a solution to M-theory that quantitatively describes dark matter and cosmic inflation. If M-theory can yield a superstring solution, it would go a long way to solving the dark-matter mystery. I know this is like the familiar cartoon of a scientist solving an equation where the caption reads, “then a miracle happens.” However, it is not quite that grim. What I am suggesting is a new line of research and theoretical enquiry. I think the theoretical understanding of dark matter lies in M-theory. The empirical understanding lies in missing-matter experiments.

What is a missing-matter experiment? Scientists are performing missing-matter experiments as I write this book. They involve high-energy particle collisions. By accelerating particles close to the speed of light, and causing particle collisions at those speeds, they account for all the energy and mass pre- and post-collision. If any energy or mass is missing post-collision, the assumption would be it is in one of non-spatial dimensions predicted by M-theory.

Why would this work? M-theory has the potential to give us a theoretical model of dark matter, which we do not have now. Postulating we are dealing with energy, and not particles, would explain why we have not found the WIMP particle. It would also explain why the Standard Model of particle physics doesn’t predict a WIMP particle. Postulating that the energy resides in the non-spatial dimensions of M-theory would explain why we cannot see or detect it, except for its gravitational effects. Why is dark matter able to exhibit gravity,, especially from a hidden dimension? That is still a mystery, as is gravity itself. We have not been able to find the “graviton,” the mysterious particle of gravity that numerous particle physicists believe exists. Yet, we know gravity is real. It is theoretically possible that dark matter (perhaps a new form of energy) and gravity (another form of energy) are both in a different dimension. This framework provides an experimental path to verify both M-theory and the existence of dark matter (via high-energy particle collisions).

This is a conceptual framework, but fits the observations. I am not suggesting we abandon our search for the WIMP particle. However, I suggest we widen our search to include the possibility that dark matter is not a particle, but a new form of energy.

 

Microscopic view of a network of blue fluorescent neurons or cells interconnected by fine filaments.

What Is Dark Matter?

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Dark matter is real, mysterious, and necessary for our existence. Without it, we would not have a universe. It is a good thing with an ominous-sounding name. So, what is dark matter?

The most popular theory of dark matter is that it is a slow-moving particle. It travels up to a tenth of the speed of light. It neither emits nor scatters light. In other words, it is invisible. However, its effects are detectable, as I will explain below. Scientists call the mass associated with dark matter a “WIMP” (Weakly Interacting Massive Particle).

In 1933, Fritz Zwicky (California Institute of Technology) made a crucial observation. He discovered the orbital velocities of galaxies were not following Newton’s law of gravitation (every mass in the universe attracts every other mass with a force inversely proportional to the square of the difference between them). They were orbiting too fast for the visible mass to be held together by gravity. If the galaxies followed Newton’s law of gravity, the outermost stars would be thrown into space. He reasoned there had to be more mass than the eye could see, essentially an unknown and invisible form of mass that was allowing gravity to hold the galaxies together. Zwicky’s calculations revealed that there had to be 400 times more mass in the galaxy clusters than what was visible. This is the mysterious “missing-mass problem.” It is normal to think that this discovery would turn the scientific world on its ear. However, as profound as the discovery turned out to be, progress in understanding the missing mass lags until the 1970s.

In 1975, Vera Rubin and fellow staff member Kent Ford, astronomers at the Department of Terrestrial Magnetism at the Carnegie Institution of Washington, presented findings that reenergized Zwicky’s earlier claim of missing matter. At a meeting of the American Astronomical Society, they announced the finding that most stars in spiral galaxies orbit at roughly the same speed. They made this discovery using a new, sensitive spectrograph (a device that separates an incoming wave into a frequency spectrum). The new spectrograph accurately measured the velocity curve of spiral galaxies. Like Zwicky, they found the spiral velocity of the galaxies was too fast to hold all the stars in place. Using Newton’s law of gravity, the galaxies should be flying apart, but they were not. Presented with this new evidence, the scientific community finally took notice. Their first reaction was to call into question the findings, essentially casting doubt on what Rubin and Ford reported. This is a common and appropriate reaction, until the amount of evidence (typically independent verification) becomes convincing.

In 1980, Rubin and her colleagues published their findings (V. Rubin, N. Thonnard, W. K. Ford, Jr, (1980). “Rotational Properties of 21 Sc Galaxies with a Large Range of Luminosities and Radii from NGC 4605 (R=4kpc) to UGC 2885 (R=122kpc).” Astrophysical Journal 238: 471.). It implied that either Newton’s laws do not apply, or that more than 50% of the mass of galaxies is invisible. Although skepticism abounded, eventually other astronomers confirmed their findings. The experimental evidence had become convincing. “Dark matter,” the invisible mass, dominates most galaxies. Even in the face of conflicting theories that attempt to explain the phenomena observed by Zwicky and Rubin, most scientists believe dark matter is real. None of the conflicting theories (which typically attempted to modify how gravity behaved on the cosmic scale) was able to explain all the observed evidence, especially gravitational lensing (the way gravity bends light).

Currently, the scientific community believes that dark matter is real and abundant, making up as much as 90% of the mass of the universe. However, dark matter is still a mystery. For years, scientists have been working to find the WIMP particle to confirm dark matter’s existence. All efforts have been either unsuccessful or inconclusive.

The Department of Energy Fermi National Accelerator Laboratory Cryogenic Dark Matter Search (CDMS) experiment is ongoing, in an abandoned iron mine about a half mile below the surface, in Soudan, Minnesota. The Fermilab is a half mile under the earth’s surface to filter cosmic rays so the instruments are able to detect elementary particles without the background noise of cosmic rays. In 2009, they reported detecting two events that have characteristics consistent with the particles that physicists believe make up dark matter. They may have detected the WIMP particle. However, they are not making that claim at the time of this writing. The Fermilab stopped short of claiming they had detected dark matter because of the strict criteria that they have self-imposed, specifically there must be less than one chance in a thousand that the event detected was due to a background particle. The two events, although consistent with the detection of dark matter, do not pass that test.

From an article written in Fermilab Today (December 13, 2009), the Fermilab Director Pier Oddone said, “While this result is consistent with dark matter, it is also consistent with backgrounds. In 2010, the collaboration is installing an upgraded detector (SuperCDMS) at Soudan with three times the mass and lower backgrounds than the present detectors. If these two events are indeed a dark matter signal, then the upgraded detector will be able to tell us definitively that we have found a dark matter particle.” As of this writing, Fermilab and other laboratories maintain their quest to find the WIMP particle. To date, we are without conclusive evidence that the WIMP exists.

If it exists, there is a reasonable probability that the WIMP particle can be “created” via experiments involving super colliders (such as the Large Hadron Collider (LHC) built by the European Organization for Nuclear Research (CERN) over a ten-year period from 1998 to 2008). Super colliders have successfully given us a glimpse into the early universe. Since most scientists believe that dark matter exists as part of creation at the instant of the Big Bang, super colliders may provide a reasonable methodology of directly creating dark matter. As of this writing, scientists using the Large Hadron Collider are attempting to create WIMP particles via high-energy proton collisions.

Are we on the right track? Is there a WIMP particle or is dark matter related to something else? We’ll explore the nature of dark matter in more depth in my next post?