Ockham’s razor is the idea that, in trying to understand something, getting unnecessary information out of the way is the fastest way to the truth or to the best explanation.

For example Einstein’s General Theory of Relativity is based on the relative simple concept of a curvature in a space-time metric.  Granted the math required to determine the gravitational forces on an object can be very complicated and not easy for many to understand however understanding or visualizing how a curvature in space-time can cause objects to accelerate is relative easy to do.  This is because one can form a relatively simple physical image of it based on how objects such as a ball is accelerated on a curved two dimensional surface on the earth and them extrapolating that to a curvature in a space-time metric. 

However, even though in 1917, he added a cosmological constant to his equations which some fell would provide one of simplest mathematical explanations for Dark energy it is difficult for many to conceptually integrate it with the physical imagery that is provided by his theory. 

Yet, this may be due to the fact that Einstein chose to define gravity in terms of time or a space-time dimension while the accelerative forces of Dark Energy are related to the spatial properties of an expanding universe.

In other words, as Ockham pointed out the best way to understand it would be to eliminate time or the space-time dimension from his general theory of gravity and replace it with spatial one because as was just mentioned our universe is not expanding through time dimension therefore it is not necessary to our understanding of its spatial expansion.

Einstein gave us the ability to do this he derived the physical properties of a gravity in a space-time environment in terms mass and energy and the constant velocity of light because that  provided a method of converting a unit of time in a space-time environment with unit of space in four *spatial* dimensions.   Additionally because the velocity of light is constant he also defined a one to one quantitative correspondence between his space-time universe and one made up of four *spatial* dimensions.

A Discussion on General Relativity by Students of John Wheeler and Bob Dicke

This fact that one can use Einstein’s theories to qualitatively and quantitatively derive the spatial properties of energy in a space-time universe in terms of four *spatial* dimensions is one the bases of assuming as was done in the article “Defining energy” Nov 27, 2007 that all forms of energy can be derived in terms of a spatial displacement in a "surface" of a three-dimensional space manifold with respect to a fourth *spatial* dimension.

In other words one can not only use Einstein’s equations to quantitatively and qualitatively derive how energy interacts with time in a space-time dimension but also how it would interact with its spatial equivalent in four spatial dimensions.

We know from the study of thermodynamics that energy flows from areas of high to ones with low density very similar to how water flows form an elevated or "high density" point to a lower one.

For example if the walls of an above ground pool filled with water collapse the elevated two-dimensional surface of the water will flow or expand and accelerate outward towards the three-dimensional environment sounding it.

Yet we know from observations of the cosmic background radiation that presently our three-dimensional universe has an average energy component equal to about 3.7 degrees Kelvin. 

However this means that according to concepts developed in the article “Defining energy" (mentioned earlier) the three-dimensional "surface" of our universe which has an average energy component of 3.7 degree Kelvin would be elevated with respect to a fourth *spatial* dimension.

Similarly if the "surface" of a three-dimensional manifold was elevated with respect to a fourth *spatial* dimension as Einstein tell us as it would be if one redefined his space-time  universe in terms of four spatial dimension then it would be accelerated outward for the same reason as how the water in a pool whose sides had collapsed.

In other words one qualitatively understand the casually of the accelerated expansion of our universe in term of the physical image of water accelerating out of collapsed pool.

Some may feel that this is an over simplification of what appears on the surface to be a rather complex phenomena such as Dark Energy but is no more simplistic that the one use to help us understand how gravity works in a space-time environment.  Granted the math behind this concept may be complex and difficult to understand as it is with the gravitational curvature in space-time however that does not mean that we cannot use it to understand its causality.

It should be remember that Einstein’s genius and the symmetry of his mathematics allows us to choose whether to define the forces associated with gravity and dark energy in either four *spatial* dimensions or four dimensional space-time.

Later Jeff

Copyright 2016 Jeffrey O’Callaghan

 

     

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In the 1920 American astronomer Edwin P. Hubble discovered that our universe isn’t static but was expanding. 

Ever since then, scientists have been trying to refine there measurement of size and rate of the universe’s expansion rate. However it is a hard thing to measurement.

Presently their three primary the methods used to determine its rate of expansion: parallax, standard candles and type Ia supernova.

The accelerating Universe: Nobel Laureate Brian Schmidt

Stellar parallax uses the apparent shift of position of any nearby star against the background of distant objects created by the different orbital positions of Earth.  Measurements are taken at six month intervals when the Earth arrives at exactly opposite sides of the Sun which give a baseline distance of about two astronomical units between observations. The parallax itself is considered to be half of this maximum, about equivalent to the observational shift that would occur due to the different positions of Earth and the Sun, a baseline of one astronomical unit (AU).

Once a star’s parallax is known, its distance from Earth can be computed trigonometrically. But the more distant an object is, the smaller its parallax. Even with 21st-century techniques in astrometry, the limits of accurate measurement make distances farther away than about 100 parsecs (roughly 326 light years) too approximate to be useful when obtained by this technique. Relatively close on a galactic scale, the applicability of stellar parallax leaves most astronomical distance measurements to be calculated by spectral red-shift or other methods.

The second method uses Standard candles called Cepheid variable stars, to measure distances throughout the Milky Way.  A variable star are ones who’s luminosity can be determined by how it brightness varies over time and comparing that to its apparent magnitude (how bright it looks to us) gives astronomers, by using the inverse square law they can infer the source’s distance simply by measuring the peak light output before comparing the number to its absolute magnitude. Using this mention they can accurately measure stellar distances up to around 1,000 MPC (parsecs),

Now, to measure extremely long distances, astronomers use type Ia supernova blasts as standard candles. They typically formed when two white-dwarf stars in a binary system collide, or one of them siphons enough material from its partner to temporarily reignite before ultimately exploding and becoming incinerated.  Astronomers have collected a lot of evidence that suggests the peak light output from one of these supernova blasts should always have an absolute magnitude of -19.6 which allows them to measure distances out to around 1000 Mpc, which is a significant fraction of the radius of the known Universe.

However measure distances using this technique is not as strait forward as it seems because their are many things in space that can absorb some of light’s energy thereby reducing a stars apparent brightness which would affect the distance measurements.

For example when the results of the Sloan Digital Sky Survey were analyzed it was found the colors of distant quasars that intergalactic space appears to be filled with a haze of tiny, smoke-like “dust” particles that dim the light from distant objects and subtly change their colors.

It goes on to say that this dust could also affect planned cosmological experiments that use supernovae to investigate the nature of “dark energy" which is causing the expansion of the universe to accelerate.  Scientists can use supernovae as a standard candle because it is an object that has some characteristic that allows us to determine its intrinsic luminosity.  Since the apparent luminosity or light which we receive has to do with the distance to the object, they can be used to figure out how far away an object is. For example if you know that a 60 watt light bulb gives off a certain amount of light or energy, and then measure the amount received from a one across the room from you, you could calculate the distance to it.

As mentioned earlier Astronomers can take advantage of standard candles to determine the distance to objects like galaxies. Using a type of supernova called a type Ia supernova, astronomers determined both the distance of the galaxy and the red shift of the galaxy. "Red shift" basically told them how much the Universe had expanded since the light left the supernova. The astronomers could then compare distance to expansion, and create a kind of ‘expansion history’ of the Universe.

However dust grains block blue light more effectively than red light. We find similar reddening of quasars from intergalactic dust, and this reddening extends up to ten times beyond the apparent edges of the galaxies themselves.  By analyzing the colors of large number or quasars located behind galaxies allows one to measure an effect that that dust has on the apparent brightness of interstellar objects. 

However there is another substance that might affect our understanding of the expansion rate of the universe.

For example we know that Dark Matter exists because of the gravitational effects it has on starts and galaxies. 

We also know that it is distributed throughout intergalactic space and that the force it projects like that of ordinary matter effects the energy of a photon because observations such as gravitational leasing tells us it does even though we may not know what it is made up of.

Therefore we should not assume that the mass associated with dark matter does interact with light casing it to loss energy or be red shifted similar to the way dust does.

However it would be much harder to detect because it would be more evenly distributed throughout space making the averaging technique used to determine the effect of dust on the apparent brightness of stars mentioned above even more difficult.

Yet if it does it could have a profound effect on our understanding of the universes expansion because even though its concentrations may very low relative to regions containing dust its distribution is more pervasive and therefore could have as large or even larger effect on the distance calculations based on the apparent brightness of quasars or type Ia supernova.

Later Jeff

Copyright Jeffrey O’Callaghan 2016

   

 

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