Tag Archives: dark matter

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

What the Difference Between Dark Matter and Dark Energy?

Categories, Physics, Universe Mysteries, , , ,

Dark matter plus dark energy makes up over 90% of the matter in the universe, and science doesn’t understand the nature or either of them. Normal matter, the stuff we can typically see and touch, makes up only 5-10% of the matter of the universe. That means that science does not understand over 90% of what makes up the universe. In this article, I will confine my discussion to the 90% we don’t understand, dark matter/energy.

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). Dark matter has a long history, that goes back to 1993. For purposes of brevity, I won’t delineate the history here. However, I want to point out that modern science believes that dark matter is the invisible glue that holds galaxies, like our Milky Way, together. It is an experimentally observed fact that the outer most stars in our galaxy are orbiting at the rate at the inner most stars. If the galaxies followed Newton’s law of gravity, the outermost stars would be thrown into space. This implies that either Newton’s laws do not apply, or that most of the mass of galaxies is invisible, hence the name dark matter. Even in the face of conflicting theories that attempt to explain the phenomena, most scientists believe dark matter is real. None of the conflicting theories (which typically attempted to modify how gravity behaves on the cosmic scale) is 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 above is a brief thumbnail sketch of dark matter. Now, let’s discuss dark energy.

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. Prior to 1998, scientific wisdom was that the expansion of the universe would gradually slow down, due to the force of gravity. However, 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.

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. 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 article in April 2015. Galaxies should be flying apart, but they don’t. Science postulates that a slow-moving particle traveling up to a tenth of the speed of light that neither emits nor scatters light is responsible, and they call that particle “dark matter.” However, there is no solid theoretical or experimental evidence to support its existence. The universe’s expansion should be slowing down due to gravitational attraction, but instead it is accelerating. No one knows why. Scientists reason there must be a cause countering the pull of gravity. They name that cause “dark energy.”

Dark matter and dark energy have two things in common. They both have the word “dark” in their name and they are both a mystery to modern science.

 

 

 

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

A New Theory of Dark Matter

Categories, Physics, Universe Mysteries, ,

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?

Categories, Physics, Universe Mysteries, , , ,

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?

A visualization of cosmic web structure showing interconnected filaments and dense clusters of galaxies in space.

Why Most of the Universe Is Missing?

Categories, Physics, Universe Mysteries, , ,

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. 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. Scientists call the mass associated with dark matter a “WIMP” (Weakly Interacting Massive Particle). However, the WIMP particle is speculative and to date has not been proven to exist. In addition, it is not predicted by the standard model of particle physics. (Some physicists have performed reformulations of the standard model to have it predict the WIMP and other particles. However, none of the particles predicted by the reformulated standard model have ever been verified.)

There is little doubt, though, that dark matter is real. There experimental evidence is solid. 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. This means they are not obeying Newton’s laws of motion or Einstein’s general theory of relativity. This faster orbit of the outermost stars suggests more mass is associated with the stars than we are able to see. If not, the stars would fly free of their orbits, into outer space.
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 there is no doubt that dark matter is real, its nature remains a mystery. Is it a particle? Is it a new form of energy? All effort to detect the WIMP particle over the last decade or so have been unsuccessful, including considerable effort by Stanford University, University of Minnesota, and Fermilab. Where does this leave us? The evidence is telling us the WIMP particle might not exist. We have spent about ten years, 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.

In my book, Unraveling the Universe’s Mysteries, I suggested an approach to test the hypothesis that dark matter may be a new form of energy. Because of the length of discussion necessary to describe my suggested approach, I will not go into it in this post. My main point in this post is to suggest we widen our investigation into the nature of dark matter to include the hypothesis that it may be a new form of energy. As a scientist, I think we have to broaden our search. I acknowledge it is possible that dark matter may be a WIMP particle, but we have no conclusive evidence after over ten years of research. Therefore, we should widen our search to include the hypothesis that it is a new form of energy.

A deep space image showing numerous galaxies and stars scattered across the dark universe.

Dark Matter, Dark Energy, and the Accelerating Universe – Part 4/4 (Conclusion)

Categories, Physics, Universe Mysteries, , ,

In the last post (part 3), I put forward a hypothesis why the space between galaxies expands. In summary, the galaxies drain energy from the vacuums of space to sustain their (i.e., the galaxies) existence. As energy is removed from the vacuums of space, so is mass (based on Einstein’s mass energy equivalence formula E = mc^2). With less energy/mass in the vacuums, the gravitational force defining the vacuum is diminished, which in turn causes the vacuum to expand.

The above hypothesis would explain the expansion of space between galaxies, but does not explicitly address the question: Why do the galaxies furthest from us appear to be moving away from us the fastest, even to the point of exceeding the speed of light?

To address the above question, let us assume we are located in the Milky Way galaxy, which is true, and we measuring the speed that another galaxy is moving away from us. Let us call our galaxy #1 (Milky Way) and the galaxy we are observing #2. From our point of reference, galaxy #2 is moving away from us, galaxy #1. However, what is really happening? Both galaxies, #1 and #2, are moving away from each other due to the expansion of space between them. Because we are considering our position in galaxy #1 fixed, it appears only galaxy #2 is moving away. For the sake of this example, let assume the velocity we measure for  galaxy #2 as it appears to be moving away from us is V1.

Next, let’s consider another galaxy, galaxy #3, that is more distant from us than galaxy #2. If we were on galaxy #2, we could measure the apparent velocity of galaxy #3 moving away from galaxy #2. Again, for the sake of this example, let us assume we measure it and its value is V2. However, from our position on galaxy #1, galaxy #2 is moving away from us at a velocity of V1 and galaxy #3 is moving away from us at the combine velocity of V1 +V2. Let assume the sum of V1 + V2 = V3. The observation of the velocity of galaxies moving away from us  will appear greater for galaxies further away from us. However, this is actually not true. If we were on galaxy #2,  we would measure galaxy #1 (Milky Way) moving away from us at the rate of V1 and galaxy #3 at the rate of V2. However, since we consider galaxy #1 (Milky Way) our fixed point of reference, we measure galaxy #2 moving away from us at a velocity of V1 and galaxy #3 moving away at a velocity of V3 (V1 + V2).  Using this simple example, we can argue that as the space between galaxies expands, from any fixed measuring point on any galaxy, the speed of galaxies moving away from our fixed measuring point will increase the further a galaxy is from our fixed measuring point.

If we consider the vastness of space and the billions (essentially uncountable) galaxies, from our fixed measuring point within the Milky Way galaxy, all galaxies will appear to be moving away from us (as the space between our galaxies expands) and the more distance a galaxy is from us, the faster it will appear to be moving away from us. The important word is the last sentence is “appear.” In reality all galaxies are moving away from each other at a velocity proportional to the expansion of space between the galaxies. However, from a fixed measuring point, the furthest galaxy from our measuring point would appear to be moving at sum of all galaxies we measure between us and the galaxy we measure  moving “away” from us. If there are billions of galaxies between us and the furthest galaxy, the sum of velocities could appear to exceed the speed of light, which would violate Einstein’s theory of special relativity.

Einstein’s theory of relativity is considered the “gold standard” among theories. It has stood scientific scrutiny for over one hundred years. According to Einstein’s theory of special relativity, no mass (for example a galaxy) can move faster than the speed of light. To get around this, current cosmology theories argue that it is the space between these distance galaxies that is expanding faster than the speed of light. However, they offer no reason why we should accept this hypothesis. In fact, it is illogical to argue that as we look at more distant galaxies, the space of those galaxies is expanding faster in proportion to the distance from our measuring point. My explanation above, removes this illogical premise and provides a relatively simple way to understand the phenomena.

As far as I know, this series of posts (parts 1-4), is the only body of work that explains and ties together the role of dark matter, the nature of dark energy and the accelerating universe. It is completely consistent with all observed phenomena and does not violate any known physical laws.