Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: xersanozgen on 07/07/2017 08:31:06
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I want to know What are the evidences of accelerating of the Universe?
I want to read the scientific articles about this subject for the evidences especially.
I looked for this on the "search section" of the forum. But I could not find a topic. If it is presented I'll remove this message.
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I assume you're asking about the rate of expansion of space.
The short answer is that no one knows for sure. We can tell that it is, and it has measurable effects. The most prevalent theory is that the presence of dark energy is responsible for the acceleration of the expansion of space.
If you google "Accelerating expansion of the universe", a few articles can be found on the subject.
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Gravity, as far as we know, is an attractive only force. This should slow the expansion. Redshift and other evidence suggests an accelerating expansion. Since gravity is inverse square in nature the velocities of galaxies should be approaching a constant inertial value. Therefore a force must be present. This requires energy. It can't come from the vacuum. Therefore the proposal of dark energy.
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Thanks for answers.
But I am curious why the scientists get the opinion of accelerating universe. Formerly we learned that expanding speed is decreasing. Which evidence or interpretation causes this new/opposite opinion?
For example an academician may say that: we had measured Virgo's radial speed, when we repeat standardized measurement operation now, we see that the value of radial speed is provided bigger value than past.
Another example may be that: we calibrated the redshift values of nearby and distant cluster and we transform them simultaneous data and we saw that the distant/past object's radial speed was bigger than present/nearby object.
Similar examples and explainings will be significant and convincing.
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This thread on red shift (https://www.thenakedscientists.com/forum/index.php?topic=67644.0) might shed some light for you
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Gravity, as far as we know, is an attractive only force. This should slow the expansion. Redshift and other evidence suggests an accelerating expansion. Since gravity is inverse square in nature the velocities of galaxies should be approaching a constant inertial value. Therefore a force must be present. This requires energy. It can't come from the vacuum. Therefore the proposal of dark energy.
General relativity allows for gravitational repulsion in two ways. One is by a positive cosmological constant and the other is by a large negative pressure. The source of this repulsion is called dark energy. Its nature is unknown.
There's more about it here: https://en.wikipedia.org/wiki/Einstein_field_equations#The_cosmological_constant
There is an article that you might want to read
Repulsive gravitation and inflationary universe models by Øyvind Grøn Am. J. Phys., 54(1), Jan. (1986)
http://booksc.org/dl/15347628/1a540d
The abstract is here: http://aapt.scitation.org/doi/10.1119/1.14769
Abstract
The phenomenon of gravitational repulsion is described within the context of the general theory of relativity. The theory implies that if a vacuum has a nonvanishing energy, then its gravitational mass density will be negative. In particular, this implies that the universe will expand exponentially during the vacuum dominated inflationary era. It is suggested that the observed expansion of the universe may be explained as a result of repulsive gravitation.
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Well I read some text and understood the origin of evidence.
They claims that: The Type Ia supernovaes which the redshifts ( Z) values are for example 0.1 and 0.5 represent the persent [1/ (1 + Z)] of universe's age.
So a supernova with a measured redshift z = 0.5 implies the universe was 1 / (1+0.5) = 2/3 of its present size when the supernova exploded. In an accelerating universe, the universe was expanding more slowly in the past than it is today, which means it took a longer time to expand from two thirds its present size to its present size compared to a non-accelerating universe.
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One conceptual problem is, space-time is a mathematical construct that helps us model the universe. Space-Time is a math tool and not a tangible aspect of reality. Yet, when it comes to many things, space-time is treated like it is a tangible thing. An accelerated expansion is a mathematical construct or tool, doing a tangible thing.
It is like saying we saw Pi dancing in the moonlight. Pi is the ratio of a circumference to diameter of a circle. In spite of that being Pi's only important job, we nevertheless saw Pi dancing in the moonlight. Both cannot be true, since they are mutually exclusive.
If we treat space-time as a math construct, we need to modify the construct, into an acceleration to be able to explain what we appear to see. This does not mean this is reality. Rather it means we modified our approximation method; construct, so we can maintain its use, and still explain the newest data. Having Pi dance in the moonlight so we can explain pulsing circles, does not make PI dance in reality. The model has to do this to keep working and not need an overhaul.
The difference is between pure and applied science. Pure science tells us about reality as it is. Applied science gets to use liberties with reality. If a liberty allows cost savings in the manufacturing process of artificial things, it is allowable since the bottom line is most important.
With applied it does not have to be real to be useful. What is real may not make it easy for mass production. For example, we live in a quantum universe which means only certain allowable states. This precludes a random universe assumption since that allows anything to happen. Random is useful for man made things like factories, pollution, gambling but is being extrapolated into the natural quantum universe to create an artificial reality for applied science needs.
If you assume the speed of light is the ground state of the universe, then all things inertial are at higher potential. Energy shows both inertial aspects; wavelength is reference dependent, and speed of light aspects; same in all references. The red shift is the inertial aspect of energy heading toward the ground state; universal red shift.
Gravity is the path that matter takes to head to the ground state. As matter accumulates, spacetime contracts toward the point instant of the speed of light reference to use the construct. The pressure causes matter to undergo energy conversions; fusion, which is then red shifted. All roads lead to Rome or C-reference.
If we assume C is the ground state, the big boom occurs at t+ and not t=0, since this event represent deviation away from the original ground state. It is easier to go further back this way and even create the universe from nothing, which could be measured in inertial reference, since inertial starts out a higher potential.
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What are the evidences of accelerating expansion of the Universe?
Well I read some text and understood the origin of evidence.
They claims that: The Type Ia supernovaes which the redshifts ( Z) values are for example 0.1 and 0.5 represent the persent [1/ (1 + Z)] of universe's age.
So a supernova with a measured redshift z = 0.5 implies the universe was 1 / (1+0.5) = 2/3 of its present size when the supernova exploded. In an accelerating universe, the universe was expanding more slowly in the past than it is today, which means it took a longer time to expand from two thirds its present size to its present size compared to a non-accelerating universe.
I did not find direct/effective evidence in the texts for accelerating. Indirect evidences are mentioned. It is a well hypothesis/ intuition / an option to note and follow. It requires more evidences/arguments to be determination.
They claims that: The Type Ia supernovaes which the redshifts ( Z) values are for example 0.1 and 0.5 represent the persent [1/ (1 + Z)] of universe's age. Scientist provided two different age of universe by using this relation. Also they intepreted the curving up of the relation redshifts-distance.
whereas it is possible that an alternative explanation for the curving up of the redshift-distance graphic.
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whereas it is possible that an alternative explanation for the curving up of the redshift-distance graphic.
There is also this: https://www.wired.com/2007/12/scientists-time/ (https://www.wired.com/2007/12/scientists-time/)
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Which evidence does the accelerating of the Universe indicate?
Well I read some text and understood the origin of evidence.
They claims that: The Type Ia supernovaes which the redshifts ( Z) values are for example 0.1 and 0.5 represent the persent [1/ (1 + Z)] of universe's age.
So a supernova with a measured redshift z = 0.5 implies the universe was 1 / (1+0.5) = 2/3 of its present size when the supernova exploded. In an accelerating universe, the universe was expanding more slowly in the past than it is today, which means it took a longer time to expand from two thirds its present size to its present size compared to a non-accelerating universe.
I did not find direct/effective evidence in the texts for accelerating. Indirect evidences are mentioned. It is a well hypothesis/ intuition / an option to note and follow. It requires more evidences/arguments to be determination.
They claims that: The Type Ia supernovaes which the redshifts ( Z) values are for example 0.1 and 0.5 represent the persent [1/ (1 + Z)] of universe's age. Scientist provided two different age of universe by using this relation. Also they intepreted the curving up of the relation redshifts-distance.
whereas it is possible that an alternative explanation for the curving up of the redshift-distance graphic.
You keep changing the title of the thread to something that doesn't actually make sense. "Which evidence does the accelerating of the Universe indicate?" doesn't actually mean anything.
I suspect that English is not your first language. Please allow me to help you by making the thread title make sense, and you leave it in a state that makes sense, and then people will understand what it is that you are asking. How about that?
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Thanks for the warning.
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I'm taking a guess of the accelerating expansion.
Imagine a line of galaxys, I know there not in lines but anyway.
Imagine a Force unit of 1. Well call it an EF(Expansion Force).
1 EF
1 + the 1 = 2 EF's
1 + the 1 + the 2 = 4 EF's
1 + the 1 + the 2 + the 4 = 8 EF's
1 + the 1 + the 2 + the 4 + the 8 = 16 EF's
Notice the result is growing exponentially. Thus an exponentially increasing outwards expansion. 8)
1 EF may not be that much but due to a large universe at some distance it's apparently expanding beyond the speed of light.
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Since the Hubble relationship tends toward a linear function the expansion cannot be exponential.
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Since the Hubble relationship tends toward a linear function the expansion cannot be exponential.
Yes, I agree. Already we cannot see the cosmic object at current position and age because of the limited/finite velocity of light. Therefore we cannot get simultaneous data.
If we consider the big-bang theory the absolute form (by God's eye) of the universe must be a spherical surface in 4D geometrical scale. But an observer (on a point of this spherical surface) can see the deformed shape because of limited velocity of light.
What/How is this deformed shape?
I had studied for this deformed shape; the result: an asymetric ellipsoidal surface like an egg or water drop. Therefore the redshifts-distance graphic curves up on diagram (attached figure).
Hubble constant: Ho = Radial velocity / distance and it must be a fixed value, but the values are measured at the interval of 80-50 km/s/mpc.
The distance is not current value because the object has a position of a past time, therefore the value of distance is not a simultaneous parameter.
Radial velocity is a resultant value of the observer's speed component (projection of current expanding speed according to observation line) and observing's speed component (projection of ancient expanding speed). Besides, radial velocities are provided with redshifts and distorted (*) by Einstein's formula (for the limit of light's velocity).
So, distances are measured smaller value than current/real value, and naturally the graphic curves up.
If the velocity of light can be infinite value, we can get simultaneous data and the graphic would be inclined linear. Also observational Hubble constant would be represented a single value; like wise, absolute Hubble constant would be determined by the formula:
Ha = Current expanding speed / current radius of universe
The points G' and L' (on the figure) have interesting and significant qualities.
(*) I did not say "transformed" because the limit of the radial velocities is the value 2c.
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