Go Back   Science Forums Biology Forum Molecular Biology Forum Physics Chemistry Forum > General Science Forums > Physics Forum
Register Search Today's Posts Mark Forums Read

Physics Forum Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.

New light on dark energy

New light on dark energy - Physics Forum

New light on dark energy - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.

LinkBack Thread Tools Display Modes
Old 06-24-2004, 03:11 PM
Bubba Do Wah Ditty
Posts: n/a
Default New light on dark energy

[Only registered users see links. ]

New light on dark energy
24 June 2004

Cosmologists in the US have made the most accurate measurements ever of how
dark energy varies with time -- and found that it remains perfectly
constant. Max Tegmark at the University of Pennsylvania and Yun Wang at the
University of Oklahoma performed numerical simulations on observational data
from supernovae, the cosmic microwave background and galaxy clusters. The
results, which agree with Einstein's predictions for a non-varying
cosmological constant, lend further support to the existence of dark energy
(Phys. Rev. Lett. 92 241302).

The acceleration of the universe is driven by a force that has repulsive
rather than attractive gravitational interactions. But although this
so-called "dark energy" is thought to account for around two-thirds of the
universe, no one knows what it is made of. Possible explanations for dark
energy include a "cosmological constant" -- which remains unchanged with
time -- that was first predicted by Einstein in 1917.

But there are also more exotic explanations for dark energy -- such as
quintessence, modified gravitational theories that include extra dimensions,
or string physics -- that suggest that dark energy could change with time.
If dark energy became progressively weaker, the universe would eventually
tear apart in a "big rip". If it became stronger, on the other hand, the
universe would collapse in on itself in a "big crunch".

Tegmark and Wang used a novel model-independent approach to measuring the
dark-energy density. They analysed data from type 1a supernovae, recorded
with the Hubble Space Telescope; the cosmic microwave background (CMB) taken
with the Wilkinson Microwave Anistropy Probe (WMAP) and the Sloan Digital
Sky Survey (SDSS); and from large-scale galaxy cluster observations.

The results agree with previous data on supernovae observations that
suggested that dark energy remains constant with time and fit well with
Einstein's cosmological constant. Moreover, the physicists calculated that
if the dark energy density were to change with time, a big crunch or big rip
could not occur for at least 50 billion years for models that allow such
events. These findings could lead to these theories being widely reassessed.

"I'm struck by the fact that the dark energy seems so 'vanilla'," Tegmark
told PhysicsWeb. "Theorists have invented scores of elegant models where it
increases or decreases its density over time, yet even with this new
improved measurement, it remains perfectly consistent with Einstein's Lambda
model where its density is a mere constant."

Belle Dumé is Science Writer at PhysicsWeb

Bubba Do Wah Ditty,

"One of the great things about books is sometimes there are some fantastic

Bushisms, 2000

Reply With Quote

dark , energy , light

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
What is Gravity? sdr@sdrodrian.com Physics Forum 1 01-27-2008 02:53 PM
the absolutely final complete collection of ideas blochee Physics Forum 2 06-15-2007 06:31 AM
the absolutely final complete collection of ideas blochee Physics Forum 0 06-14-2007 10:30 PM
Seeing Holographically cinquirer Physics Forum 24 11-19-2003 12:09 PM

All times are GMT. The time now is 10:13 PM.

Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Copyright 2005 - 2012 Molecular Station | All Rights Reserved
Page generated in 0.17039 seconds with 16 queries