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Variable

Acceleration of the Universe

9 posts in this topic

I have been recently researching the topic of the expansion of the Universe. Specifically, the 1998 discovery by Saul Perlmutter that claims the Universe is expanding at an accelerated pace. The premise of this discovery was that the observed redshift of a Supernova 7 Billion Light years away was perceived to be receding at a slower rate than that of the redshift observed of a Supernova 1 Billion Light Years away. The conclusion was that the Universe was expanding at a slower rate 7 Billion years ago than it was 1 Billion years ago, thus an acceleration of expansion.

 

I am curious as to what everyone's thoughts are on the conclusion of this data. Specifically, do you agree with the findings of Saul and his team?  Do you have other theories as to why the accelerations of the two Supernovae were perceived to be receding at different rates?  What else could cause our perception to show the varying expansion rates? 

 

Would the differing space environments at the time of the stars' destruction have an effect? E.g. The Universe was more dense at the time of the Supernova 7 Billion years ago than that at the time of the Supernova 1 Billion years ago. That being the case, 7 Billion years ago, when the Universe was expanding, the density of the Universe could have impeded the acceleration of expansion more so than the less dense Universe that the Supernova 1 Billion years ago was experiencing. This leads me to believe that the acceleration would be naturally increasing as the density continues to decrease over time.

 

Another question I have been pondering is the point of reference for the two differing Supernovae, which is Earth. Our Galaxy is also caught in the expansion of the Universe, so the rate at which we are moving would also have to be factored in. As well as the locations and directions of all three points of reference, Earth, Supernova 1, and Supernova 2. If Our Galaxy is expanding in a similar direction through space as that of Supernova 1 (7 Billion Years ago) and an opposite direction than that of Supernova 2 (1 Billion Years ago), then the obvious outcome would be that Supernova 2 would appear to be receding at a more accelerated rate than Supernova 1 due to the variance of our location in space in comparison to that of the observed points.

 

From my understanding, which is very minuscule, redshift does not allow the observer to determine the direction of expansion, just the speed and distance. I suppose given the variables, one can calculate the direction of expansion if given enough time to observe the Supernovae, but seeing as the observer only has approximately 18 days before a type 1a Supernovas light fades, that does not seem likely to me.

 

Any feedback is appreciated. Even if it is to tell me I am wrong. I enjoy hearing all perspectives.

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Personally never been convinced of the acceleration aspect. As you say it is based on one observation or aspect.

I did ask at a talk on similar at a university and got a sort of blank look. What I asked was simple: Besides this accelerated expansion what other theories were there to explain it?

I recall that for the Higgs Boson at the initial stage there were something like 40 different theories put forward and these were dismissed or proven not applicable over time, ultimately we were left with Higgs theory that had managed to survive through the many years of investigation. In the case of accelerated expansion and so "Dark Energy" it was jumped on so fast that it seems a bit bizarre.

Are there alternatives: Well there was what was termed "Tired Light" but that was discarded. I can think of another that seems to hang in. The thougtht of that came from another talk on the early stages of the universe. Half mentioned it but it was almost as if minds had been made up and there was to be no discussion. Which to me implied a sorry state for the university. It seemed they were simply following the herd.

You say:

Would the differing space environments at the time of the stars' destruction have an effect? E.g. The Universe was more dense at the time of the Supernova 7 Billion years ago than that at the time of the Supernova 1 Billion years ago. That being the case, 7 Billion years ago, when the Universe was expanding, the density of the Universe could have impeded the acceleration of expansion more so than the less dense Universe that the Supernova 1 Billion years ago was experiencing. This leads me to believe that the acceleration would be naturally increasing as the density continues to decrease over time.

Consider this bit "denser" universe, but consider the propogation of a wave through a medium. In general the denser the medium then the faster the wave travels. Would light therefore have been faster at the early stages of the universe. Light is a wave propogating through space-time and space-time was in effect denser. If so then I think you will find that light will have an longer wavelength. So "earlier" light could therefore be more red shifted then the normal now as it was created. Therefore the further back (distance) you observe then a greater red shift is also observed - it started out a bit redder, or more accurately with a bit longer wavelength. That would give a greater "red shift" for the more distant objects.

In one respect that would give a simpler explanation for the additional red shift of distant galaxies, would appear to be consistent with wave propogation in a material.

Concernign your "point of reference" - yes we are in an expanding universe and we will be moving but it will be apparent from some other point of the universe. So we are in effect "not moving just everything else is. And generally it is moving away from us, with M31 being the main exception.

Not sure of the US universities but I am finding that the people here tend to have "tunnel vision". They consider theirs and only their research. Have attended talks at the RAS, BAA and two or three universities,  one was on early planet formation, there is a problem getting from the quite small to the quite big in formiing planets. The other talk was on Dust in space, that talk dropped in one almost irrelevant comment that could bridge the gap, especially with the properties of the material concerned (water). The catch was that the person giving the Dust talk had no interest in planet formation, and the planet formation people had no interest in Dust. No one attends the others talks and so no cross fertilisation. Maybe a PhD is awarded for the wrong reason.

 

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Nowadays we have much more powerful spectrometers - we don't need a supernova to measure redshift. Space telescopes can get clear redshift readings for millions of galaxies in the observable universe, and plotting them on a graph with distance along the other axis shows clear correlation.

6 hours ago, Variable said:

This leads me to believe that the acceleration would be naturally increasing as the density continues to decrease over time.

Although newton's laws are a bit outdated now, the basic principles behind them are still true. If a=f/m, we need an outward force to cause outward acceleration, not simply a reduction in inward force. A lot of scientists believe dark matter and dark energy are to blame - when acceleration takes place, kinetic energy increases, which has to have come from a different energy store.

I think an acceleration of the expansion of the universe is very widely accepted - it's what caused this acceleration that we aren't sure about.

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On 3/12/2017 at 08:53, JoeP said:

Nowadays we have much more powerful spectrometers - we don't need a supernova to measure redshift. Space telescopes can get clear redshift readings for millions of galaxies in the observable universe, and plotting them on a graph with distance along the other axis shows clear correlation.

Just measuring the redshift of a galaxy is not sufficient to determine the rate of expansion. Measuring the redshift of distant galaxies spectroscopically is not the problem. It is knowing the distance. In order to determine this you need for example to measure the apparent brightness of objects with known luminosity (ie "Standard Candles" like  type 1a supernovae for example) 

Robin

Edited by robin_astro
clarity
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ok well I will take them odds anyday well better than the odds of a lottery win

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no on serious note them plank images are not the present time they from the being off the universe maybe in a few billon years they will show spiral patterns

Edited by sonic190178

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