Understanding the accelerating expansion of the universe based on redshift

In summary, the universe is expanding. This is confirmed by observations of supernovae, galaxies, and the cosmic microwave background.
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Laconic99
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Understanding the accelerating/decelerating expansion of universe based on redshift..

I am trying to understand how the expansion of the universe is accelerating, if indeed it is. It's confusing, as some people say that the expansion is accelerating, whereas I have a video lecture where the professor says that the expansion is decelerating. My question is how do you conclude that expansion is accelerating/decelerating based on these numbers, given that the more distant galaxy is seen as it was much longer ago than the closer one?

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Circinus Galaxy.

Distance from earth: 1.23x10^20 km (13 million ly)

speed: 426 km/sIOK-1 galaxy.

Distance from earth: 1.23x10^23 km (13 billion ly)

speed: 290 477 km/s

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Space news on Phys.org
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The Perlmutter supernova legacy study confirmed expansion.
 
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In the early universe, the expansion was decelerating. It's only within the last few billion years that it's been accelerating. So I guess it depends upon what epoch you're looking at.

But in any case today we have hundreds of supernovae, as well as large galaxy surveys and cosmic microwave background observations that all confirm the same story. Two individual galaxy observations aren't going to overturn this (or even add much to it, because two single galaxies are just two small data points among thousands).
 
  • #4
Tests of Big Bang: Expansion from NASA by Official: Dr. Gary F. Hinshaw,
Updated: Friday, 04-16-2010
http://map.gsfc.nasa.gov/universe/bb_tests_exp.html

Universe is Expanding - "Red Shift" is Proof of Einstein's General Theory from "Cosmic Times is a product of the Imagine the Universe! website. Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan P. Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center. . .
Last Updated: Tuesday, 05-Jan-2010 16:34:49 EST"
Best to review the contents online from the link (url) below:
http://cosmictimes.gsfc.nasa.gov/online_edition/1929Cosmic/expanding.html
 
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As a scientist, it is important to approach this question with an open mind and critically examine the evidence. The key factor in understanding the expansion of the universe is redshift, which is a phenomenon where light from distant galaxies appears to be shifted towards the red end of the electromagnetic spectrum. This redshift is a result of the stretching of space as the universe expands.

Based on the information provided, it is clear that the IOK-1 galaxy is much more distant from Earth than the Circinus Galaxy, as indicated by the larger distance and the fact that the light from IOK-1 has taken much longer to reach us. This means that we are seeing the IOK-1 galaxy as it was 13 billion years ago, while the Circinus Galaxy is only seen as it was 13 million years ago.

Now, let's focus on the speeds of these galaxies. The IOK-1 galaxy has a speed of 290477 km/s, which is significantly higher than the speed of the Circinus Galaxy at 426 km/s. This high speed suggests that the IOK-1 galaxy is moving away from us at a much faster rate than the Circinus Galaxy. This is consistent with the idea that the expansion of the universe is accelerating, as the further away a galaxy is from us, the faster it appears to be moving away due to the stretching of space.

On the other hand, it is also possible that the expansion of the universe is decelerating, as suggested by your professor. This could be due to the influence of dark matter or dark energy, which are mysterious components that make up a large portion of the universe and have a significant effect on its expansion. Further research and observations are needed to fully understand the nature of these components and their impact on the expansion of the universe.

Overall, the key takeaway is that the observed redshift of distant galaxies, along with their speeds, provide evidence for the accelerating expansion of the universe. However, it is important to continue studying and analyzing this phenomenon in order to gain a deeper understanding of the forces at play in our vast and ever-expanding universe.
 

FAQ: Understanding the accelerating expansion of the universe based on redshift

What is redshift and how does it relate to the accelerating expansion of the universe?

Redshift is a phenomenon in which light from distant objects appears to have longer wavelengths, shifting towards the red end of the spectrum. This is due to the expansion of the universe, which causes the space between galaxies to stretch, causing the wavelengths of light to also stretch. The amount of redshift is directly proportional to the distance of the object, and observations of redshift have shown that the universe is expanding at an accelerating rate.

What evidence supports the theory of accelerating expansion based on redshift?

The most significant evidence for accelerating expansion based on redshift comes from observations of type Ia supernovae. These are explosions of white dwarf stars that have a known luminosity. By measuring the redshift of these supernovae, scientists have found that they appear dimmer than expected, indicating that they are moving away from us at an accelerating rate. This is consistent with the theory of accelerating expansion.

How does dark energy play a role in the accelerating expansion of the universe?

Dark energy is a hypothetical form of energy that is thought to be responsible for the accelerating expansion of the universe. It is believed to make up about 68% of the total energy density of the universe. While its exact nature is still unknown, it is thought to be a repulsive force that counteracts the effects of gravity and causes the expansion of the universe to accelerate.

Is there any other evidence besides redshift that supports the theory of accelerating expansion?

Yes, there is other evidence that supports the theory of accelerating expansion. One piece of evidence is the cosmic microwave background radiation, which is a remnant of the early universe. The patterns and fluctuations in this radiation can provide information about the expansion rate of the universe and have been found to be consistent with the theory of accelerating expansion. Additionally, observations of the large-scale structure of the universe, such as galaxy clusters and filaments, also support the idea of accelerating expansion.

What are the implications of the accelerating expansion of the universe for the future of the universe?

The accelerating expansion of the universe suggests that the expansion will continue to accelerate in the future. This means that the distance between galaxies will continue to increase, and eventually, the expansion may become so fast that galaxies will no longer be able to maintain their structures. This could ultimately lead to the "heat death" of the universe, in which all matter is spread out and too far apart to interact with each other. However, the exact fate of the universe is still uncertain and heavily debated among scientists.

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