Posts tagged ‘Relativity Theory’

March 18th, 2013

Q&A 15: What, Exactly, IS Gravity?

by Max Andrews

Question:

Hello Max,

My name is Chad Gross and I am the director of Truthbomb Apologetics.  Brian Auten of Apologetics315 recommended that I email you with a question that I have.

My question deals with gravity and whether or not it is immaterial.  It seems to me that gravity is not composed of matter and/or energy; therefore, it is immaterial.  However, when interacting with an unbeliever on the topic on this post and he said the following:

“Without mass there would be no gravity, right? It’s true that gravity itself isn’t made of atoms, but you must admit that the material world is more than just particles. Einstein showed that matter and energy are equivalent and can transform into each other. When I talk about something being material, therefore, I’m thinking of both matter and energy.

It’s true again that gravity might not be a form of energy, since it’s just a force. Maybe gravity arises due to the nature of space and time. But without matter, there would be no space and time. So I think it’s uncontroversial to consider the physical forces to be “material.”

When I think of things that are not material, I’m thinking of spirit, or soul. God isn’t made of matter or energy, and God would still exist even without any matter or energy, right?” 

Now, I realize gravity is not immaterial in the same way that moral judgments, mathematics, logic, etc.  Here is my reply to him:

August 6th, 2012

Nothing is in Time

by Max Andrews

J.M.E. McTaggart provides an objection to the A series of time but suggesting that it may be true that past, present, and future are mere illusions of the mind.[1]  McTaggart dismisses the argument’s subjectivity of time by simply defining it out of existence.

McTaggart’s Argument:

1. Anything existent can either possess the characteristic of being in time or the characteristic of not being in time.

2. Anything existent does not possess the characteristic of being in time [due to subjective references, a lack of indexing events from moment to moment or changing, etc.]

3.  Therefore, anything existent does not possess the characteristic of being in time (time is illusory).

The objection to the A series by the subjectivity of the individual mind is not so easy to dismiss as McTaggart seems to do.  With advances in relativity theory this objection may have phenomenological credibility.  Though McTaggart’s rejection of the argument is correct, there are better reasons for opposing the argument of the mind’s subjective relationship to time.[2]

July 26th, 2012

“It’s Just a Theory” — What’s a Scientific Theory?

by Max Andrews

A theory is distinct from a mere scientific explanation.  Scientific explanation requires a causal explanation, which requires a law-governed explanation.  Natural law describes but does not explain natural phenomena.  Newton’s law of universal gravitation described, but did not explain, what caused gravitational attraction.  Theories unify empirical regularities and describe the underlying process that accounts for these phenomena.  Within theories are axioms, a small set of postulates, which are not proved in the axiom system but assumed to be true.[1]

A theory goes beyond natural laws and scientific explanations in explaining the scientific explanations. A theory refers to a body of explanatory hypotheses for which there is strong support.[2]  Theories are a conjunction of axioms (of the laws of nature) and correspondence of rules specified in a formalized ideal language.  This ideal language is composed of three parts: logical terms, observational terms, and theoretical terms.  The logical terms were initially treated as analytic claims (particularly under the hypothetico-deductive model).  Observational claims were to be unproblematic, understood as referring to incorrigible sense-data and later to publicly available physical objects.  Correspondence rules were used to connect theoretical language to observational claims.[3]

May 30th, 2012

The Lorentz Transformations

by Max Andrews

The fundamental question raised by these postulates of special relativity is how different coordinate systems (reference frames) are related, i.e., how one transforms between them. (x, y, z, t) denotes the coordinates of some event in frame S, what are the coordinates (x’, y’, z’, t’) in the frame S’ moving at the velocity v relative to S? But first, a clarification on proper time and coordinate time:

Proper time is time measured between events by use of a single clock, where these events occur at the same place as the clock.  It depends not only on the events but also on the motion of the clock between the events.  An accelerated clock will measure a shorter proper  time between two events than a non-accelerated (inertial) clock between the same events.

In standard special relativity, we often want to express results in terms of a spacetime coordinate system relative to an implied observer.  In this case, an event is specified by one time coordinate and three spatial coordinates.  The time measured by the time coordinate is referred to as coordinate time, to distinguish it from proper time.

May 29th, 2012

The Postulates of Special Relativity

by Max Andrews

Albert Einstein felt the strong need to affirm Galilean relativity, which applied only to mechanical laws, that he decided to extend it to include electromagnetic and optical laws.  He adopted the principle that no physical experiment (mechanical, optical, electromagnetic, or any physical law whatsoever) can distinguish between a state of absolute rest and a state of constant velocity.  With the help of the German mathematician Herman Minkowski (who taught us to think in terms of spacetime rather than space and time individually.  Einstein introduced a new principle of relativity and revolutionized mechanics.

There are two postulates of special relativity but the consequences are profound.

  1. Postulate 1 (Principle of Relativity): The laws of nature are the same in all inertial frames.
  2. Postulate 2 (Constancy of the Velocity of Light): The speed of light in empty space is an absolute constant of nature and is independent of the motion of the emitting body.
    read more »

May 15th, 2012

How Einstein got to E=mc^2

by Max Andrews

In 1865 James Clerk Maxwell had unified electricity and magnetism by developing his equations of electromagnetism. It was soon realized that these equations supported wave-like solutions in a region free of electrical charges or currents, otherwise known as vacuums.  Later experiments identified light as having electromagnetic properties and Maxwell’s equations predicted that light waves should propagate at a finite speed c (about 300,000 km/s).  With his Newtonian ideas of absolute space and time firmly entrenched, most physicists thought that this speed was correct only in one special frame, absolute rest, and it was thought that electromagnetic waves were supported by an unseen medium called the ether, which is at rest in this frame.

Let an object in a rest frame simultaneously emit two light waves with the same energy E/2 in opposite directions (now having equal but opposite momenta), the object remains at rest, but its energy decreases by E.  By the Doppler effect, in another frame, which is moving at the velocity v in one of those directions, the object will appear to lose energy equal to

May 3rd, 2012

Galilean Relativity Theory

by Max Andrews

Galieleo’s relativity stated that an observer who moves uniformly with constant speed in a straight line, that is, who moves with constant velocity, is called an inertial observer.  The Galilean principle of relativity can be stated as follows: The mechanical laws of physics are the same for every inertial observer.  In other words, by observing the outcome of mechanical experiements, one cannot distinguish a state of rest apart from a state of constant velocity.

By Galileo’s definition, two inertial observers can disagree on whether or not two separate events occurred at the same position in space. Since no mechanical experiment can distinguish a state of rest from one of uniform velocity, Galileo effectively abolished the universality of the notion of an ‘observer at rest.’

March 7th, 2012

Conceptualizing God’s Relationship to Time

by Max Andrews

Absolute Eternality (Timelessness):  This view is the traditional (Augustinian) view that God is absolutely timeless.  His timelessness is not affected by the temporality of the universe nor his interactions with it.  In the metaphysics of absolute eternality, God experiences all of his life and being in one eternal now.

Relative Eternality (Timelessness):  The relative eternality position acknowledges that God transcends time, which is a created thing and dependent upon God, but denies that he is absolutely atemporal because it sees God as actively sustaining a changing world in existence.  The relative eternalist therefore maintains that God is timeless relative to physical time but temporal relative to an uncreated metaphysical time that transcends the universe and is a pure duration that flows without change.  God’s being is ontologically prior to this temporal aspect of his life and serves as the ground of it.

March 7th, 2012

The Planck Scale Physics

by Max Andrews

In the system of Planck units, the Planck base unit of length is known simply as the Planck length, the base unit of time is the Planck time, and so on.  These units are derived from the five dimensional universal physical constants in such a manner that these constants are eliminated from fundamental equations of physical law when physical quantities are expressed in terms of Planck units.

Planck Length: 1.616252(81) 10-35 m