Universe

http://Cosmology.com Dark Matter Dark Energy & the Unknown Universe, by Rhawn Joseph, Ph.D.

Duration : 0:5:6

Read the rest of this entry »

The Mystery of Dark Matter (1/4): Stars Are Moving Too Fast.

A mystery exists! Galaxies do not seem to have enough mass for stars to orbit at their observed speeds. Galaxies should be flying apart, but they don’t. Why not? Explore the surreal world of dark matter – one of the universe’s greatest mysteries.

—
Please subscribe to Science & Reason:
• http://www.youtube.com/Best0fScience
• http://www.youtube.com/ScienceMagazine
• http://www.youtube.com/FFreeThinker
—

Shedding Light on Dark Matter

Over the last few decades, physicists have discovered that around ninety percent of every galaxy in the universe is made of an unseen substance called dark matter. Damian Pope, PIs Senior Manager of Scientific Outreach, comments, Its currently one of the hottest topics in physics. The module provides teachers with tools to show how dark matter was discovered, to explain why it remains a mystery, and to share the passion of scientists who are trying to discover what its made of.

This presentation is available to educators on DVD and comes complete with specially-crafted teacher notes.

• http://www.perimeterinstitute.ca

The Mystery of Dark Matter Video Game
• http://perimeterinstitute.ca/dark_matter_game/index.html

—

In astronomy and cosmology, dark matter is a form of matter that is undetectable by its emitted electromagnetic radiation, but whose presence can be inferred from gravitational effects on visible matter and background radiation. According to present observations of structures larger than galaxies, as well as Big Bang cosmology, dark matter accounts for the vast majority of the mass in the observable universe.

Dark matter was postulated by Fritz Zwicky in 1934, to account for evidence of “missing mass” in the orbital velocities of galaxies in clusters. Subsequent to then, other observations have indicated the presence of dark matter in the universe, including the rotational speeds of galaxies, gravitational lensing of background objects by galaxy clusters such as the Bullet Cluster, and the temperature distribution of hot gas in galaxies and clusters of galaxies.

Dark matter plays a central role in state-of-the-art modeling of structure formation and galaxy evolution, and has measurable effects on the anisotropies observed in the cosmic microwave background. All these lines of evidence suggest that galaxies, clusters of galaxies, and the universe as a whole contain far more matter than that which interacts with electromagnetic radiation: the remainder is frequently called the “dark matter component,” even though there is a small amount of baryonic dark matter. The largest part of dark matter, which does not interact with electromagnetic radiation, is not only “dark” but also, by definition, utterly transparent.

The vast majority of the dark matter in the universe is believed to be nonbaryonic, which means that it contains no atoms and that it does not interact with ordinary matter via electromagnetic forces. The nonbaryonic dark matter includes neutrinos, and possibly hypothetical entities such as axions, or supersymmetric particles. Unlike baryonic dark matter, nonbaryonic dark matter does not contribute to the formation of the elements in the early universe (“big bang nucleosynthesis”) and so its presence is revealed only via its gravitational attraction. In addition, if the particles of which it is composed are supersymmetric, they can undergo annihilation interactions with themselves resulting in observable by-products such as photons and neutrinos (“indirect detection”).

Nonbaryonic dark matter is classified in terms of the mass of the particle(s) that is assumed to make it up, and/or the typical velocity dispersion of those particles (since more massive particles move more slowly). There are three prominent hypotheses on nonbaryonic dark matter, called Hot Dark Matter (HDM), Warm Dark Matter (WDM), and Cold Dark Matter (CDM); some combination of these is also possible. The most widely discussed models for nonbaryonic dark matter are based on the Cold Dark Matter hypothesis, and the corresponding particle is most commonly assumed to be a neutralino. Hot dark matter might consist of (massive) neutrinos. Cold dark matter would lead to a “bottom-up” formation of structure in the universe while hot dark matter would result in a “top-down” formation scenario.

As important as dark matter is believed to be in the universe, direct evidence of its existence and a concrete understanding of its nature have remained elusive. Though the theory of dark matter remains the most widely accepted theory to explain the anomalies in observed galactic rotation, some alternative theories such as modified Newtonian dynamics and tensor-vector-scalar gravity have been proposed. None of these alternatives, however, has garnered equally widespread support in the scientific community.

• http://en.wikipedia.org/wiki/Dark_matter
.

Duration : 0:6:10

Read the rest of this entry »

***READ THIS BEFORE ASKING ANYTHING***

This is the ultimate size comparison video that you can find on the internet in HD.
Starts with the tinyest dwarf planets of our solar system, then continues with large planets, dwarf stars, stars giant/supergiant/hypergiant stars, nebulae, globular clusters and galaxies.
There is the famous VY Canis Majoris rated as the biggest star known, but very few know that that the incredible IC 1101 is the largest known object in the entire universe. Only galaxy clusters are bigger than it.
Hope you enjoy this one.

FAQ:
-Sizes are not 100% accurate as there is no way to directly measure them.
-Star sizes may change in the future, and new stars may eventually appear into this biggest stars list
-Song: Celtic Panpipes – Ride on

Duration : 0:4:0

Read the rest of this entry »

Science@ESA Vodcast (Episode 2): Planck – Looking Back To The Dawn Of Time (Part 1): Big Bang Cosmology.

—
Subscribe to Science & Reason:
• http://www.youtube.com/Best0fScience
• http://www.youtube.com/SagansCosmos
• http://www.youtube.com/FFreeThinker
—

In the Science@ESA series Rebecca Barnes will take you on a journey of discovery into the rapidly evolving field of space astronomy and planetary exploration.

In this second episode Rebecca takes a close look at Planck – a European Space Agency mission built to detect radiation from the microwave portion of the electromagnetic spectrum. This mission will help find answers to some of the most important questions in modern science.

• http://astronomy2009.esa.int
• http://www.youtube.com/esa

—

The Big Bang is the cosmological model of the initial conditions and subsequent development of the Universe that is supported by the most comprehensive and accurate explanations from current scientific evidence and observation.

As used by cosmologists, the term Big Bang generally refers to the idea that the Universe has expanded from a primordial hot and dense initial condition at some finite time in the past (currently estimated to have been approximately 13.7 billion years ago), and continues to expand to this day.

• http://en.wikipedia.org/wiki/Big_Bang

—

Planck was selected as the third Medium-Sized Mission (M3) of ESA’s Horizon 2000 Scientific Programme, and is today part of its Cosmic Vision Programme. It is designed to image the anisotropies of the Cosmic Background Radiation Field over the whole sky, with unprecedented sensitivity and angular resolution.

Planck will provide a major source of information relevant to several cosmological and astrophysical issues, such as testing theories of the early universe and the origin of cosmic structure.

Planck was launched on 14 May 2009 together with the Herschel satellite. After launch, Planck and Herschel separated and are now proceeding to different orbits around the second Lagrangian point of the Earth-Sun System.

• http://www.esa.int/SPECIALS/Planck/index.html
.

Duration : 0:6:4

Read the rest of this entry »

An international team of astronomers using the NASA/ESA Hubble Space Telescope has discovered a ghostly ring of dark matter formed long ago during a colossal collision between two galaxy clusters. This is the first time that dark matter has been found with a distribution that differs substantially from the distribution of ordinary matter. Read more at: http://www.spacetelescope.org/news/html/heic0709.html

Duration : 0:4:55

Read the rest of this entry »

COSMOS Video News Release
For the first time ever, astronomers have been creating a three—dimensional map of how the dark matter is distributed across the Universe. An international team of scientists, among them groups from Marseille, the Max-Planck Institutes and Paris have been using data from the NASA/ESA Hubble Space Telescope. The results are published in nature online of 8 January 2007, and at the meeting of the American Astronomical Society in Seattle. This Video News Release discussed this discovery. More on: http://www.spacetelescope.org/news/html/heic0701.html

Duration : 0:3:11

Read the rest of this entry »