Alex Filippenko on ‘dark matter’ and ‘dark energy’:
“The scientific method: trying stuff out, seeing if it works, changing it when it doesn’t — is one of the great accomplishments of humanity. … People wrap themselves in their beliefs, and they do it so tightly that you can’t set them free; not even the truth will set them free. And listen, everyone’s entitled to their opinion — they’re even entitled to their opinion about progress, but do you know what you’re not entitled to? — you’re not entitled to your own facts; sorry, you’re not.”
When viewing the following narrated slide presentation video,
Unlike the Solar System rotation curve for the orbital velocities of the planets, which decays exponentially with orbital radius, extended spiral galaxy disks exhibit flat or even accelerating rotation curves (i.e., increasing orbital velocity with increasing distance from the galaxy core). Assuming only the gravitational influence of the host galaxy’s observed radiating matter, which is concentrated near the galaxy core, this empirical phenomenon seems to defy Newton’s law of universal gravitation. Consequently, it has been assumed that a vast halo of completely invisible gravitating matter (i.e., ‘dark matter’) must exist around the galaxy. However, despite several decades of effort, no independent evidence for the existence of ‘dark matter’ has been found, other than its apparent gravitational effect.
Current textbooks and university lectures on the subject of ‘dark matter’ typically compare the dynamical behavior of a spiral galaxy disk to the Solar System, stating that the two systems are expected to exhibit similar rotation curves, according to the modeled gravitational effect of manifest radiating matter. This is a scientifically naïve statement because spiral galaxy disks are subject to significant externally-sourced gravitational tidal forces (from other galaxies in the host cluster), while no such significant gravitational tidal forces exist within the Solar System. Because the respective gravitational environments of a spiral galaxy disk and the Solar System are entirely different, these are two completely distinct classes of gravitational dynamical systems.
Distinct planetary systems do not perturb one another due to the immense distance of neighboring stars relative to the size of these systems; thus, the Solar System planets exhibit dynamical behavior consistent with a single, highly-dominant central mass. The Galactic center (Sagittarius A*) is about 60 million times Neptune’s heliocentric range. In contrast, the estimated range to the nearest major galaxy (M31) is less than 100 times the Sun’s Galactocentric range. Individual stars in a spiral-galaxy disk are perturbed in a precise, mathematically-defined way by the collective mass of a neighboring, co-orbiting galaxy or group of galaxies.
How does the gravitational gradient of the host cluster affect the internal dynamics of spiral galaxy disks according to Newton’s law of universal gravitation? The GravitySim software provides a realistic, virtual “toy model,” that addresses this question. It proves to be the case that there is no need to invoke a ‘dark-matter halo’ to account for spiral galaxy rotation curves; they are explained by canonical Newtonian physics when one abandons the arbitrary, incorrect assumption that the mass responsible for an observed rotation curve is collocated with the target galaxy. Typically, the mass perturbing disk orbits (i.e., producing a ‘flat’ or accelerating rotation curve) is far beyond the telescope’s frame of view, which makes it “invisible.” To make it visible, one simply needs to zoom out the perspective of the telescope, but this is not practically possible.
The GravitySim Circular orbit simulation clearly shows that the long-term dynamical result of typical galactic gravitational interaction, as predicted by Newton’s law of universal gravitation, cannot be other than what is observed (i.e., a rotation curve shape for spiral galaxy disks that is distinctly different from the characteristic, monotonically-decreasing curve for gravitationally-isolated planetary systems). It also provides a compelling solution to the winding problem with profound cosmological implications.
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Given a casual inspection of the user interface, which is seen on the homepage, the GravitySim software may at first appear dauntingly complex; rest assured that, like a smartphone, the software is designed for ease of use, even by non-technical people. Accordingly, there is no tedious instruction manual, which need not exist. When you run a simulation for the first time, the software will automatically lead you through the process with brief instructions and information, configure all the controls for you, and give you a meaningful result that is easy to interpret. Afterwards, you will find that changing control settings and experimenting on your own is easier than using a smartphone.
The GravitySim Internet-based browser applet (“Standard Version”) is designed for displays having at least 1600 × 900 pixel resolution; it is not well-suited for smaller laptop screens. If your screen has a lower resolution, download the application; its zoom feature will allow you to fit the interface to your display. Ideally, run the HD version on a high-resolution desktop display. For Mac OS X, run Software Update… (apple menu) to ensure that your operating system software is current. Safari is the recommended browser on Mac. Determine the graphics performance of your browser by running the Fishbowl Test; in a window of moderate size, you should see 60 fps (frames per second) with at least 100 fish (set Fish to 100). If the water is red and the fish swim slowly, a problem exists; first try switching browsers.
For Macs running OS X 10.8.x (Mountain Lion), special directions apply for enabling Java applets. If the applet seems broken, this is because of an easily-remedied permissions or configuration problem, or because there is insufficient available memory. Before launching the applet on older machines, you may want to quit other running applications to free up memory.
The history of science is replete with examples in which popular, prevailing explanations for empirical phenomena were not just wrong, but completely misleading (e.g., luminiferous aether). The promise of science, and physics in particular, is that we can always eventually correct our mistakes and come to understand how the physical Universe actually works. Both directly and indirectly, the advantage of accurately knowing how and why things work, so we may act effectively, can prove critical to our individual and collective survival.
In the early 1970s, a young American astronomer named Vera Rubin discovered what has become known as the “galaxy rotation problem.” In short, as the galactic radial coordinate of stars, gas and dust in spiral galaxy disks increases, their observed orbital velocities are considerably greater than expected. These velocities cannot exist without an applied gravitational force, which is exclusively produced by mass. The mass of these galaxies, in the form of naturally-radiating stars, gas and dust, is far less than necessary to account for the observed velocities according to Newton’s Law of Gravity. Einstein’s relativity is not a factor. A graph of orbital velocity versus the galactic radial coordinate is called a “rotation curve.” Given a typical, measured spiral galaxy rotation curve, it is certain that additional mass, complementing the observed ‘normal’ mass of the galaxy, is required to account for the accelerating forces that produce the observable.
Over time, the prevailing explanation for the unexpected shape of spiral galaxy rotation curves was that a large amount of mysteriously-invisible gravitating matter exists in a ‘dark halo’ in and around these spiral galaxies. In physics, “invisible” means producing no electromagnetic radiation whatsoever, which for many physicists is considered “unphysical,” meaning contrary to the laws of physics and therefore impossible. Consistent with this perspective, no compelling explanation for ‘dark matter’ has been put forward after nearly four decades of worldwide effort.
In June 2012, one of the fathers of the Standard Model of Particle Physics, Martinus Veltman, who is also a 1999 Nobel Laureate in Physics, stated, “I think it [dark matter] doesn’t exist.”† At the time, this was a bold statement challenging the beliefs of most people in the astrophysics community. However, it proves that Veltman is correct, certainly as concerns the purported ‘dark halo’ around spiral galaxies. This is something you will discover for yourself using GravitySim. Of course, this conclusion leads to additional revolutionary conclusions in physics and cosmology, which will become widely known in due time.
Also see WHY A “TOY MODEL”? & WHAT IS IT? in Docs.
Which is more hazardous, ignorance or a false belief? — An Alaskan bush pilot who is unsure if the plane has sufficient fuel to fly from Nome to Kotzebue would never initiate the flight plan. However, if the pilot initiates this flight plan believing that there is enough fuel, but in reality there is not, this would inevitably lead to a catastrophe, unless the error is discovered soon enough to be corrected safely. At best case, time and fuel will have been wasted and future arrival at Kotzebue further delayed. In science, accepting ignorance, and making prudent decisions accordingly, is similarly preferable to acting on a false belief. Moreover, as soon as a false belief is discovered, it is vital that it be rapidly communicated and immediately corrected.
Science is a social activity, which means that your personal participation is important. The more people who understand what is true and what is not true (i.e., who knows what they are talking about, and who needs to change their current way of thinking) serves the best interest of everyone. “Organized science” involves a hierarchy of controversial, abstract ideas that play a vital role in many people’s lives, which means that these ideas, which should always be objective, can become highly politicized. It is a fallacy to believe that individual scientists and groups of scientists are immune to “science denial” when a necessary change in ideas implies some perceived personal loss. A key role of the collective scientific community, and also groups of informed citizens, is to ensure that rational, scientific objectivity overrules confirmation bias and personal political agendas. Guided by Occam’s razor and standards of professional ethics, members of the astrophysical community must subordinate subjective personal interests to the objective requirements of the scientific method.