Spacetime

online resources:

PBS NOVA

The NOVA Space Archive discusses popular scientific topics such as gamma-ray bursts, E=mc², and string theory.

Distant elements

The alignment of a quasar and a distant galaxy has enabled astronomers to unravel the origin and evolution of chemical elements. The furthest galaxies are generally too faint to reveal their chemical composition in detail with high-resolution spectroscopy. However, Distant elements of surprise (July 2003) describes an uncommon galaxy quasar alignment that allows previously unattainable observations. The distant galaxy is surprisingly advanced along the path of chemical evolution. Many of these elements had never been seen before outside the Milky Way, and therefore provide an unprecedented opportunity to study the complex pattern of element abundances in a galaxy that is in a very different place and time in the universe.

Chandra X-ray Observatory

Chandra is an orbiting observatory that allows astronomers to observe X-rays from the universe. The Chandra website includes news, images, and an acronym guide & glossary.

HubbleSite News Center

The HubbleSite has an extensive image gallery that includes the Hubble Deep Field (HDF), Hubble Ultra Deep Field (HUDF), and galaxy clusters so massive they bend light, such as Abell 2218.

The Bohr Atom

In the early 20th century, the absorption and emission of atomic radiation remained undescribed. Max Planck had offered the solution of discrete, finite quanta of energy for the problem of black-body radiation. Einstein later explained the photoelectric effect as a manifestation of the quanta concept. The Bohr Atom describes emission and absorption lines found within electromagnetic spectrums. When these lines are found shifted towards longer wavelengths, it is known as a redshift. The analysis in general is known as spectroscopy.

Infinite Redshift

The Pound-Rebka experiment tested gravitational redshift. Black holes can be defined as a massive compact objects surrounded by an area where the gravitational redshift, as observed from a large distance, is infinitely large. This explains why radiation from black holes is not detectable.

Time & Position

Knowing where you are means knowing what time it is. The Global Positioning System (GPS) provides latitude and longitude within a few feet anywhere on Earth. However, the gravitational time dilation that occurs in the presence of a large mass (such as a large planet) or accelerated reference frame (such as a fast moving satellite) is significant enough that the atomic clocks onboard the orbiting GPS satellites are routinely corrected.

Inflationary Universe

Andrei Linde is one of the authors of inflationary cosmology. The Self-Reproducing Inflationary Universe published in Scientific American (Vol. 271, No. 5, pages 48-55, November 1994) outlines several fundamental problems with Big Bang cosmology while at the same time proposing an Inflationary Universe fix — However, accurate weather models prove to be a bit more difficult.

Introduction to Astronomy (Physics)

MIT OpenCourseWare provides open access to course materials. Estimated temperatures from actual observations of massive radiation emissions such as gamma-ray flares (RHESSI satellite), GRBs, black hole x-ray jets, and/or particle accelerator speeds and energies are all just a few minutes shy of a temperature labeled t=0 in the partial lecture notes, thermal history of the universe. Hydrogen and helium are elements formed within three minutes of that temperature as it cools. Hydrogen and helium recombination emissions within this set of supernova spectra are an example of observing such element formation.

Young galaxy is nearby

Certain cosmology expected young galaxies to be very distant. However, scientists using the Hubble Telescope observed I Zwicky 18, a nearby galaxy that formed only 500 million years ago. In contrast, the visible universe is currently about 13.7 billion years old. Space.com has a related article about the youngest galaxy.