608. NEWTON’S SECOND LAW OF MOTION – Momentum or F=ma
Cosmic Evolution’s Claim:
The universe is accelerating in its expansion such that the velocity at which distant galaxies recede from an observer increases over time. NASA’s dark-matter website article claims that nine billion years after the universe began, its expansion started to speed up, driven by an unknown force that scientists have named dark energy.
US Department of Energy’s dark-energy article claims the universe is expanding, and it expands a little faster all the time. Scientists call the speeding up of this expansion cosmic acceleration.
Given:
All scientific laws and theories must be compatible. When two scientific theories that are incompatible, it means that one or both are incorrect.
This article compares these theories:
- The theory of cosmic evolution and
- The second law of conservation of motion – momentum or F=ma
- The universe is accelerating in its expansion. Click here to read Wikipedia’s article on Accelerating Expansion of the Universe.
Note that the theory of evolution is not just about biological evolution. It is about cosmic, chemical, stellar, organic, vertical (creation of a new spies), and horizontal (adaptation) evolution. For this discussion, we look at Newton’s second law of motion and cosmic evolution.
Definition:
The Law of Conservation of Momentum is Newton’s Second law and it states that a body of mass m subject to a net force F undergoes an acceleration a that has the same direction as the force and a magnitude that is directly proportional to the force and inversely proportional to the mass, i.e., F = ma.
Here are three general principles associated with this law:
- Pushing harder on an object gives it acceleration; like your gas pedal give your car acceleration.
- The object accelerates in the exact same direction as the force you apply; like throwing a ball in the direction you want.
- Heavier objects need more force to move at the same rate as lighter objects because mass resists change in motion; like pushing an appliance across the kitchen floor verses pushing a chair across the kitchen floor.
Another way to look at this law is that the total momentum (p=mv) of an object remains constant over time unless acted on by an outside force. Or momentum (mass times velocity) cannot be created or destroyed, only transferred between objects. An example of transfer of momentum is billiards.
Question: Is the expansion of the universe in conflict with Newton’s Second Law of Motion? There are two issues here. First, what force started the universe expansion moving it from zero speed of the state of nothingness into a high-speed expanding universe? Second, what force is presently accelerating the galaxies in the universe away from other galaxies? I want to address the first question of initial outward motion.
Click I have questions if you have questions and need answers.
Discussion:
There are two different forms of momentum: 1) angular (spinning) and 2) linear (straight ahead). I will be discussing linear momentum here. But note that both momentums are forms of the conservation of energy law as well.
Initial Outward Motion: Cosmologists claim that The Big Bang resulted in massive radial expansion (linear momentum), propelling visible matter directly outward from the point of singularity.
Ongoing Cosmic Acceleration: Saul Perlmutter discovered cosmic acceleration, that is expansion of the universe is speeding up, at the Lawrence Berkeley National Laboratory and received the 2011 Nobel Prize in Physics.
Dark energy: Two independent research teams discovered dark energy in 1998; the Supernova Cosmology Project, and the High-Z Supernova Search Team. They found that the expansion of the universe is accelerating by an unknown repulsive force. The term dark energy was coined by University of Chicago astrophysicist Michael Turner in 1998 and remains one of the great mysteries of physics. Cosmologists think that dark energy makes up about 70% of the universe today.
NASA claims on their dark energy website article that dark energy is the name that cosmologists gave to the mysterious “something” that is causing the universe to expand at an accelerated rate.
According to Newton’s second law of motion, acceleration requires a force to push the expanding universe past its initial velocity of zero or at rest into acceleration. Is dark energy capable or sufficient to perform this task?
Think of ongoing cosmic acceleration as if you were driving a car accelerating onto the interstate while in an acceleration lane. When you get to merging speed, you let off of the energy or gas pedal, you no longer accelerate. The car engine is the force that causes you to accelerate and letting off of the gas pedal removes the force causing acceleration. At that point momentum is fixed and your velocity will remain at the velocity or speed where you let off of the gas pedal. That is until other outside forces influence your momentum like wind friction, wheel bearing friction, engine friction, other mechanical friction, etc.
But I digress because I want to know what the force was to begin the initial outward motion.
Cosmologists attribute dark energy as the force or influencer of cosmic acceleration. Given that claim, I have to ask why does dark energy cause the universe to expand when gravity from visible matter and dark matter has a tendency to draw matter together. Granted, gravity is not a strong force to begin with. It loses its influence at a rate proportional to the square of the distance between masses.
Cosmologists tell us that dark energy’s density is very low: 7×10−30 g/cm3 (6×10−10 J/m3 in mass-energy), much lower than the density of visible matter or dark matter within galaxies. Furthermore, it dominates the universe’s mass–energy content because it is uniform across space. So, if this is true, how does a low-density gravity influence the universe if it is everwhere pulling in all directions?
To explain cosmic acceleration, cosmologists state that dark energy has “negative pressure.” We think of pressure in familiar terms like an inflated tire pushing out on the rubber membrane and steel belt enclosing it. But cosmologists explain that negative pressure is like tension; more like a rubber band pulling in. So, they say dark energy has negative pressure that makes the universe accelerate.
I am confused because there seems to be a conflict. If negative pressure corresponds to a pull, then how does dark energy account for pushing galaxies apart?
Other cosmologists think that the direct action of dark energy’s negative pressure is ineffective, because it’s equal in all directions and cancels out. To believe any of this one has to believe, assume, or take it on faith that dark energy has negative pressure.
In another view, cosmologists say that dark matter is more like a new kind of material that has its own gravitational field that pushes things apart rather than pulling them together.
Some cosmologists have figured out that negative pressure is accelerating the universe outwardly, Monthly Notices of the Royal Astronomical Society has a different story. They report that lead researcher Professor Young-Wook Lee, of Yonsei University in South Korea, claims that his study of the universe cast doubt that dark energy is driving the acceleration of distant galaxies away from each other. Furthermore, the universe has entered a phase of decelerating expansion.
What do we really know? Not much. I mean no disrespect since cosmologists are in the discovery phase of the universe. We have to give them credit since they recognize the law of momentum as evidence that they attribute a force to cosmic acceleration.
In summary, with all of this discussion about dark energy and cosmic acceleration, what remains is that cosmologists still need some type of force or energy to begin the initial outward motion; i.e. accelerate the universe from its initial state of zero speed up to some cosmic speed.
Conflict:
Scientists have not found any violation of Newton’s second law of m motion as it relates to dark energy and cosmic acceleration.
There doesn’t seem to be a conflict between cosmic acceleration and Newton’s second law of motion because cosmologists have attributed the force influencing cosmic acceleration to dark energy.
But cosmologists have ignored the fundamental question of initial outward motion. What force initiated the inflating of the universe?
Conclusion:
Cosmologists think the Big Bang itself is the starting condition of expanding space and inflation and dark energy is the mechanism proposed to explain the universe’s earliest, fastest phase of that expansion. While this sounds reasonable, is dark energy the force that accomplished this spectacular feat of overcoming the gravity of the point of singularity to inflate the universe into existence? Cosmologists have it right; there has to be a force. But is dark energy a capable force that changed the universe’s momentum from a point of singularity starting condition into what we see in our sky today? And how did dark energy ignite itself to begin universal inflation overcoming the gravity of a black hole? Science knows that things don’t just happen. There has to be a force that overcome the zero momentum of singularity and blows the universe apart into high speed expansion.
Harry’s Engineering Logic Check:
Think of the trillions of stars in our universe. Think about the universe’s visible mass. Now add even more dark matter that we cannot see. Ask yourself how did all of our nearly unimaginable number of energized stars and immeasurable mass of the universe start moving outwardly. Ask yourself what force could change the momentum of all of the mass in the universe from zero to expansion such as we see today.