Spring 2014 Editor: Harsh Joshi

What is Dark Energy?
Basic Definition - Dark Energy is a force that is opposite the force of gravity. Instead of pulling objects inwards it pushes objects outwards.

dark-energy-abell-cluster-100819-02.jpg

This galaxy cluster called Abell 1689 is famous for the way it bends light in a phenomenon called gravitational lensing. Study of the cluster has revealed secrets about how dark energy shapes the universe.
Credit: NASA, ESA, E. Jullo (JPL/LAM), P. Natarajan (Yale) and J-P. Kneib (LAM)

Space.com

URL: http://www.space.com/20929-dark-energy.html

AUTHOR: Nola Taylor Redd

OVERVIEW: This page gives a brief history of Dark Energy, how it was discovered, why its discovery is important and offers a couple theories on what exactly dark energy is and how it behaves. The first section of the page describes how Dark Energy was proposed to explain the acceleration of the universe. The first observations of an expanding & accelerating universe were made by Edwin Hubble in 1929 & were brought to attention again in 1990 when two groups of astrophysicists observed supernovae to calculate that the universe was not slowing down, it was speeding up. The website also has valuable information on the difference between dark energy and dark matter.

LAST UPDATED: 5/1/13

DATE REVIEWED: 5/2/14

REVIEWED BY: Harsh Joshi

ACCURACY: 10/10. Space.com is a highly credible website that always offers reliable news about various subjects in astronomy.

READABILITY AND CLARITY: 8/10 for the average reader. This website contains dense astronomy/physics vocabulary that the average reader may not be familiar with.

EASE OF NAVIGATION: 10/10 This website is filled with visuals and interactive tools to help the user navigate with ease.


"Dark Energy and Dark Matter"


NASA_logo_300dpi.jpg
nasa.com

Url: http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/

Author: NASA

Overview: This website offers a summary on how dark energy is expanding our universe & how much scientists have figured out so far. The page also offers various theories associated with dark energy and ultimately concludes that there isn't enough data to say any theory is incorrect. The best part of this page is that in the end it differeciates between dark energy and dark matter.

LAST UPDATED: November 30 2012

DATE REVIEWED: 5/5/14

REVIEWED BY: Harsh Joshi

ACCURACY:10/10. The National Aeronautics and Space Administration never offers false information.


READABILITY AND CLARITY: 8/10. It's easy to read but still hard to understand. Reading level is probably about college standard.

EASE OF NAVIGATION: 7/10. Although there are interactive navigational maps around the site, there is so much information packed into small sectors it is hard to navigate through.



Minute Physics YouTube Video on Dark Energy



youtube.com/minutephysics

URL: https://www.youtube.com/watch?v=v6o2bUPdxV0

Author: Sean Carroll/minutephysics

Overview:
This is a great & simple video narrated by famous physicist Sean Carroll about what dark energy is and how it affects our universe. What's even better is that everything the narrator says, the channel's artist draws and helps the viewer visualize.

Last Updated: Oct. 5 2011

Date Reviewed: 5/6/2011

Accuracy: 10/10. This youtube channel is almost always accurate. Plus Sean Carroll is a well known famous physicist!

Clarity: 8/10. Although the visuals help, the narrator speaks too fast, and there is a lot of dense vocabulary to keep up with.

Ease of navigation: 10/10.


Dark Energy (and gravity) visualized




youtube.com/apbiolghs

Url:
https://www.youtube.com/watch?v=MTY1Kje0yLg

Author: apbiolghs youtube channel.

Overview:
At the 7 minute mark, the instructor explains how dark energy affects the fabric of space. This video is exceptional because the instructor physically explains how dark energy functions and what it does.

Last Updated: March 10 2012

Date Reviewed: 5/6/14

Accuracy: 9/10. Looks like a lecture at a California highschool/college. The information is accurate.

Clarity: 10/10 the best part of this video is that it is clear to understand and the model extremeley helps visualize how dark energy works.

Ease of navigation: 10/10.

Science Show YouTube Video on Dark Energy



youtube.com/scishow

Url: https://www.youtube.com/watch?v=ATwVApurIQ4

Author: SciShow

Overview:
This is another great simple video explaining and defining dark energy. It goes through the definition, how it was discovered & how the force is affecting our universe. It also goes through the history of dark energy and Einsteins cosmological constant; along with other various theories.

Last Updated: November 22 2012

Date reviewed: 5/5/14

Accuracy: 10/10. This video has about the same information you'll find on any other video/page about Dark Energy. There is a limited amount of information on the topic yet it is so hard to actually understand

Clarity: 10/10. The narrator & the YouTube channel are dedicated to providing clear and easy to understand information to the average person. You don't need to be a rocket scientist to understand but there still is some vocabulary that may be unfamiliar.

Ease of navigation: 10/10.


"Something From Nothing"




darkenergy_what_is_piechart.jpg
source:
http://hubblesite.org/hubble_discoveries/dark_energy/graphics/darkenergy_what_is_piechart.jpg

URL: http://hubblesite.org/hubble_discoveries/dark_energy/de-what_is_dark_energy.php

AUTHOR: Hubble Site Organization

OVERVIEW:
This webpage tries to define what dark energy is and how much scientists know. Because this topic is so new and cutting edge, there is not a lot of information but the page offers predictions, theories, and dilemmas associated with dark energy that are controversial & fascinatingly disturbing.

LAST UPDATED: N/a

DATE REVIEWED: 5/5/14

REVIEWED BY: Harsh Joshi

ACCURACY: 10/10. This website is highly credible.

READABILITY AND CLARITY: 6.5/10. This page is very hard to understand for the average reader. Lots of dense vocab, even some rhetoric. What's even worse is the small font that isn't that clear to read.

EASE OF NAVIGATION: 6/10. Small font & confusing interactive navigational maps/tools make it hard to navigate the site.



Spring 2012 editor, Giovanni Billeci

Dark Energy

Edited by: Giovanni Billeci

Dark Energy is a force of energy that acts as the opposite of gravity, instead of pulling together it pushes away. Dark energy is used to explain why the universe expands at a faster rate as it moves away. Dark energy is the most accepted hypothesis used to explain observations that have arisen since the 1990s, indicating that the universe is expanding at an accelerating rate. Dark energy accounts for 73% of the total mass-energy of the universe.


Image: Expansion of the universe
Image: Expansion of the universe




History

The first evidence of an unusually speeding up universe was inadvertently discovered by Einstein, in his model introducing the Cosmological Constant. What had happened was that his models of the universe showed acceleration, Einstein did not what caused the acceleration but for his model he called it the Cosmological Constant.

During the 1900s many other observations of acceleration were reported & different theories were proposed.
Find detailed history of dark energy here

- Source(s):

wikipedia.org/wiki/Dark_energy
http://home.fnal.gov/~skent/early.html




Evidence

First sign from observed data


"The first suggestion for dark energy was in a paper written by astronomer György Paál in 1992. In 1990, Broadhurst et al. had published the "pencil beam survey" regarding the irregularities in galaxy distribution.
Using this data, Paál et al. found that in some cosmological models, the irregularities became more regular.
In these models the cosmological constant, dark energy, was needed."

- Source(s):

http://en.wikipedia.org/wiki/Dark_energy


Supernovae


Cosmologist use measurements of supernovae to prove the existence of Dark energy. One model, called the
The deceleration parameter was created to show the acceleration of the universe.
Credit:
Jones, Mark H.; Lambourne, Robert J. (2004). An Introduction to Galaxies and Cosmology. Cambridge University Press. p. 244. ISBN 978-0-521-83738-5



The Fate of the Universe


Many cosmologists believe the acceleration began 5 billion years ago, after it had finished decelerating.

One theory states that eventually the acceleration will spread the galaxies apart so far apart that no light would be visible.

Find more detailed information on the fate of the universe with dark energy here


Expansion
Expansion


http://jdem.lbl.gov/DarkEnergy.html
This article explains a lot about the beginning of the universe starting with the Big Bang. Then leading into how the universe is being pushed from each other using dark energy as the explanation of this phenomenon. This article also describes three leading theories about dark energy.
  1. dark energy is some sort of energy pervading space that doesn't change with time (usually called the cosmological constant),
  2. it is an energy field that changes in space and time (sometimes called quintessence), or
  3. it's some property of gravity we don't as yet understand; an extension of Einstein's theories, such as quantum gravity.

This article is clear explains Big Bang along with Dark energy. Easy to navigate page is plain. Last updated (April 30, 2009).
Author: Unknown (Berkley Labs).

Picture below from the article above showing the effect dark energy has on the universe.
different models of the expansion of the Universe
different models of the expansion of the Universe



http://whatis.techtarget.com/definition/0,,sid9_gci917929,00.html
This encyclopedia is a short and simple explanation of the theory of dark energy and how it works




http://scienceandreason.blogspot.com/2005/09/dark-energy-quintessence.html



File:DarkMatterPie.jpg
File:DarkMatterPie.jpg


Edited by: Erik Menjivar

http://imagine.gsfc.nasa.gov/docs/science/mysteries_l1/dark_energy.html
Here is a that website gives you a detailed description of what astronomers think Dark Energy is, where it comes from, where it lies in the universe, what its effects are on the entire universe, and describing the affect dark energy has on the slowing and speeding up effects of the expansion of the universe. This site is not the easiest to navigate through and is intended for people with a fair knowledge of astronomy. This site was updated Thursday, 29-Oct-2009 Erik Menjivar


http://www.space.com/scienceastronomy/090427-mm-dark-energy.html
On this webpage, the user can access a few links intended to give you more background information on Dark Energy such as the history, the method of finding Dark Energy, where Dark energy is more likely to be found and things of that nature. This site is easy to navigate through with links boldly highlighted and links to other things mentioned in the article that seem interesting. The article is fairly easy to read and understand, even for people with little knowledge regarding Dark Energy. This article was posted April 27 2009. Erik Menjivar

http://www.allaboutscience.org/dark-energy.htm
The All about Science Organization gives you a good overview of what Dark Energy is, the difference between Dark Matter and Dark Energy. (Dark Matter being the thing holding galaxies together, while Dark Energy is trying to push them apart). Also this article describes how much Dark Energy is consists in our universe. This page is a few paragraphs long, easy to read and understand, even for people with little understanding of astronomy just looking for a good explanation, but is not the easiest to navigate through and the page seems pretty bland. Erik Menjivar

http://news.bbc.co.uk/2/hi/science/nature/6156110.stm
This article hosted by BBC is designed to give you a brief description of what Dark Energy is, Einsteins hypothesis of what is repelling the universe from imploding and how that was proved. This article is put into words so that people with no understanding of Dark Energy can get a simple explanation of what it is and what it is doing. This Site is fairly easy to navigate through but only has a few links to other Dark Energy articles. this article was last updated 11-2006 Erik Menjivar

http://en.wikipedia.org/wiki/Dark_energy
Wikipedia is a potential source to get the most information about a topic and provides plenty of information about Dark energy such as the evidence of dark energy, the nature of dark energy, the implications of the fate of the universe, and its history, made to read very easily and understandable by people with little or no understanding and for those with a fair understanding as well. Although Wikipedia is criticized for being unreliable, the references at the end of every page are VERY useful; So even though the information on the Wiki page be wrong & unhelpful- the references at the bottom of the page can help tremendously. Erik Menjivar


Edited by Michael Aubin

This section is dedicated to dark energy. Dark energy is one of the more recent discoveries to be confirmed in astronomy. Not much is known about this mysterious force even though it makes up nearly 75% of the universe. The links below are meant to be resources for anyone seeking insight on the topic.

Hubblesite
http://hubblesite.org/hubble_discoveries/dark_energy/
Date Read: 12/7/08
This site is very good for learning about the history behind the discovery of dark energy. Basically, it starts with a slide show, with each side summing up a particular moment of how dark energy was discovered. Most of the slides are accompanied with videos and animations to give a visual representation of what is being explained in words. This makes the material easier to understand. At the end, there are links to others parts of the website that further explain what dark energy is and what effects it will likely have on the universe. The site was very straightforward, easy to understand and navigate. Although, you probably will need a high speed internet connection if you want to watch the videos. I believe it would be appropriate for anyone learning about astronomy and probably the best place to start if you want to learn about dark energy.


Dark Energy Changes the Universe
http://www.nasa.gov/missions/deepspace/f_dark-energy.html
Date Read: 12/7/08
This is a page on NASA’s official website explaining the effects dark energy will have on the universe. There is a link at the bottom of the page that elaborates a bit more on the subject and the Joint Dark Energy Mission, which intends to measure how the universe’s rate of expansion has changed over time. However, that link no longer seems to work, but here’s the page supposed to go to: http://universe.nasa.gov/science/darkenergy.html. The page and links are probably fine for high school students and above. However, some prior knowledge about Einstein would be helpful with comprehension of the material. The site is slightly more difficult to navigate than others just because you may have to backtrack through parts of the site or find what you are looking for through a generic keyword search. However, the information itself that the website presented was pretty clear and useful.


WHAT IS DARK ENERGY? (WHAT IS, AND IS NOT, DARK MASSFREE ENERGY)
http://www.aetherometry.com/Electronic_Publications/Science/dark_energy.php
Date Read: 12/7/08
This article is pretty lengthy, so make sure you have some time set aside before you try to read it. The writer basically doubts the existence of dark energy. However, I would encourage people to be wary when reading the page, because much it his argument seems to be fallacious and at times even downright illogical. The author ellaborates on why dark energy is not necessary for an explanation of the universe and how the research and subsequent reasoning dark energy is based on could have been flawed. That aside, I think a person who has a significant background in astronomy and physics should really be the only one to seriously read and critically analyze the article just because the material is so dense that a typical person like me who is just starting to learn about the topic would not get most of the information. Furthermore, I also recommend it for more experienced people because they would be best at distinguishing what the author may have right or wrong. However, it is still and interesting read and good for seeing what other people think about the topic.

Dark Energy
http://www.stsci.edu/~ariess/darkEnergy.htm
Date Read: 12/7/08
This page is written by Dr. Adam Riess, who is a researcher that helped to discover dark energy in 1998. The page is clear and very informative. However, there are some more advanced terms and ideas Riess uses, so I would say page is geared towards college students. It is an excellent resource because not only does he explain dark energy well but he addresses counterarguments to the research dark energy is based on. I especially liked the page because it explained some of the terms that are thrown around but never really explained on other pages. For example, until reading this I did not know what a Type 1a Supernova was even through it was mentioned on many other resources for dark energy. Another cool feature of the page is the images tab at the top. If you go to this you can see actual pictures of Supernovae used for research. The only bad thing I could see on the site was that the text is a bit small.

ScienceDaily
http://www.sciencedaily.com/search/?type=news&keyword=dark+energy§ion=all&period=365
Date Read : 12/7/08
Not too much is known about dark energy. So while researching the topic, it is hard to find webpages that not do not just repeat each other. ScienceDaily is appealing because it presents new ideas to the topic. This particular link is the result of a keyword search of “dark energy” on the ScienceDaily website. This is a good resource because it provides up to date articles on the topic of dark energy, such as current research and speculation about the properties of dark energy. The articles are written mostly by reputable sources like astronomers from universities and organizations like NASA. Each individual article is pretty brief so you do not have to dedicate too much time to any particular one. One thing I do not like about the site is there is no reasonable means available to sort through and filter articles so at times it can be difficult to navigate and find specific articles. However, if you want up to date information on what is new with dark energy ScienceDaily is a very good place to visit.

Also: This is a great link to include on any astronomical website because it's inspiring and motivational for upcoming researchers. Grants provide the opportunity to expand our knowledge of the universe, and contribute to the growing astronomy field worldwide. A $2.1 million dollar grant was given to University of California Berkeley on December 5, 2012, by the Gordon and Betty Moore Foundation. The money is to be used for dark energy research. This is a well informed, accurate, and easy to read page. It's well organized and I would advise anyone interested in the astronomy field to read this news on the progression of dark energy research.

Edited by Sean Calverley

$2.1M Grant to Berkeley Advances Dark Energy Research

This is a great link to include on any astronomical website because it's inspiring and motivational for upcoming researchers. Grants provide the opportunity to expand our knowledge of the universe, and contribute to the growing astronomy field . A $2.1 million dollar grant was given to University of California Berkeley on December 5, 2012, by the Gordon and Betty Moore Foundation. The money is to be used for dark energy research, more specifically a project known as BigBOSS. BigBOSS is located at the Department of Energy's Lawrence Berkeley National Laboratory. This is a well informed, accurate, and easy to read page. It's well organized and I would advise anyone interested in the astronomy field to read this news on the progression of dark energy research.

Laboratory Equipment


bigboss.jpg

http://www.laboratoryequipment.com/news/2012/12/21-m-grant-berkeley-advances-dark-energy-research

Author : Lawrence Berkeley National Laboratory
Last Updated : Dec 5, 2012
Date Revised : Dec 5, 2012

Is the universe expanding faster than the speed of light?

This article is effective in addressing a few misconceptions regarding dark energy and phenomenon associated with it. Specifically, it explains the claim that "the universe is expanding faster than the speed of light". Initially, one might be extremely confused by this statement and be skeptical about its validity. However, the author describes clearly different ways this claim can be interpreted and verified. This is a good link to add because the author seems to be a true "scientist", admitting where he does and does not know a whole lot about a topic. In addition, his writing is clear, and easy for the average college student to comprehend.

Curious About Astronomy

expanding-universe.jpg

http://curious.astro.cornell.edu/question.php?number=575
Author : Dave Rothstein
Last Updated : Oct. 16, 2007
Date Reviewed : Dec 5, 2012

Hubble Rules Out One Alternative to Dark Energy

This is a great site that explains some of the hypothesizes dark energy and its nature. Specifically, this article addressed on hypothesis, stating that our universe is surrounded by a bubble of relatively empty space, 8 billion light years across. Some astronomers believed this to be the cause of the expansion of our galaxy. However, this site goes on to explain a new method of calculating the rate at which our universe is expanding, which has proven the "bubble" hypothesis false. Essentially, astronomers have found a more accurate way of tracking cepheid variables (pulsating stars) moving away from us. It is a very interesting topic, written in an organized, easy to read manner. Although the subject matter is quite complicated, the author does a fine job at simplifying things. I would suggest this site for anyone at a high school reading level or above. The information from this site is also very reliable (being hubblesite.org).

HubbleSite

hubble.JPG


http://hubblesite.org/newscenter/archive/releases/2011/2011/08/results/100/
Author : L. Macri
Last Updated : 08, 2011
Date Reviewed : Dec 5, 2012

Why is the universe speeding up?

This is a great site that captures the attention of audiences. The page isn't extremely long, but it is effective in conveying its message, which is letting the world know about some current research surrounding dark energy and its origin. DES or "Dark Energy Survey", is a mission to accurately measure the cosmic expansion throughout our past, up to 14 million years ago. Astronomers believe that calculating the expansion of our universe in the past will not only give us information regarding its cause, but also give us a glimpse into our future, and the role dark energy will play in our lives. This site is short and sweet, giving a nice blend of the history of the project, and the current research objectives. This page is easy to read, and its short and informative writing makes navigation a breeze.

The Dark Energy Survey

collab.jpg


http://www.darkenergysurvey.org/
Author : DES collaboration
Last Updated : Oct. 2012
Date Reviewed : Dec 5, 2012

Does Dark Energy Really Exist?

This is a very basic page, that is a preview of an article inside the magazine "Scientific American". I included this page because it gives good background information regarding the reasons behind dark energy research. The site refers to astronomers such as Copernicus, and gives audiences a solid foundation to build their knowledge upon. This is an interesting link to include in any astronomy based web site because magazines are a great way to be updated with the latest news. This would be a great find for anyone interested in learning more and more about simple to complex astronomical phenomenon and current research. The article is written in an organized and clear manner, as any advertisement should be. It suits the reading levels of a large audience while maintaining sophisticated topics. This link makes you want to learn more about dark matter and its research field.

does-dark-energy-exist_1.jpg

http://www.scientificamerican.com/article.cfm?id=does-dark-energy-exis
Author : Timothy Cliffton
Last Updated : March 23, 2009
Date Reviewed : Dec 5, 2012