Symmetry Explains in 60 Seconds:
The Big Bang
by Mark Trodden, University of Pennsylvania for
Symmetry Magazine
The big bang refers to the start of the rapid expansion of our universe. Edwin Hubble discovered this expansion in the 1920s through observations of faraway galaxies, showing that the distances between them are growing as time rolls on. This stunning discovery is beautifully explained by general relativity—Einstein's theory of gravity—augmented by two new concepts, dark matter and dark energy.
If the universe is expanding today, of course, it must have been smaller in the past; and the matter and energy it contains must have been denser and hotter. General relativity specifies exactly how this happened, and in doing so makes some dramatic predictions. In particular, the universe should be filled with a bath of leftover heat from the initial cosmic fireball. This remnant of the big bang was first observed in the 1960s and is known as the cosmic microwave radiation.
Just minutes after the big bang, the early universe was hot enough to synthesize the light elements of the periodic table, such as hydrogen and helium, from the raw material of the cosmos, in observationally measured amounts that precisely agree with the predictions of cosmology. And tiny irregularities in the initial distribution of the hot, dense matter grew into the stars and galaxies we observe today.
These observations, and many others, make the big bang a remarkable and
unshakable fact of modern science.
Reminder:
Director's Work Group Meetings This Week
by Persis Drell
I will be holding work group meetings December 6-8 in the Kavli Auditorium. These sessions will provide you the opportunity to speak face-to-face with me about anything on your mind. There will be six meetings organized by
directorate using the below schedule, with an 8 a.m. combined Owl Shift and
Accelerator Directorate meeting on Tuesday, and an overflow/open meeting Wednesday for anyone unable to attend their dedicated
directorate session. The Operations Directorate has asked me to address them on December 9 at another venue, so the six sessions listed below do not include Operations.
Schedule by directorate:
- PPA: Monday, Dec. 6, 2–3 p.m.
- AD with last names A–M and Owl Shift: Tuesday, Dec. 7, 8–9 a.m.
- SSRL: Tuesday, Dec. 7, 9:15-10:15 a.m.
- LCLS and Photon Science: Tuesday, Dec. 7, 2:30–3:30 p.m.
- AD with last names N–Z: Wednesday, Dec. 8, 2:45–3:45 p.m.
- Overflow/Open: Wednesday, Dec. 8, 4–5 p.m.
Colloquium Today: Dark Matter
Today at 4:15 p.m. in Panofsky Auditorium, astrophysicists Simona Murgia,
Louie Strigari and Risa Wechsler of the Kavli Institute for
Particle Astrophysics and Cosmology will present a special SLAC colloquium
celebrating the international event Dark Matter Awareness Week.
Dark Matter Awareness Week, December 1–8, 2010, is a worldwide event with the aim of disseminating important knowledge in the scientific community on one of the most challenging and mysterious aspects of the
universe: the presence of an unseen mass component in galaxies. 150 institutes
from all over the world will participate.
SLAC is in the forefront of institutions
using a number of varied approaches to seek answers to the mystery of dark
matter, the elusive substance that is thought to make up more than 20 percent of
the universe. In Monday's colloquium, each speaker will present a 15-minute talk
covering a different aspect of research into dark matter.
The colloquium is free and open to all.
Next Monday, Bill Schlotter, instrument scientist with the Linac
Coherent Light Source Soft X-ray Instrument, will present the final
colloquium of the quarter: "Studying Materials with the LCLS: The First Year of SXR."
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