Riess used Hubble to find nature’s own “weapons of mass destruction” — very distant supernovae that exploded when the universe was less than half its current age. The apparent brightness of a certain type of supernova gives cosmologists a way to measure the expansion rate of the universe at different times in the past.
Riess and his team joined efforts with the Great Observatories Origins Deep Survey (GOODS) program, the largest deep galaxy survey attempted by Hubble to date, to turn the Space Telescope into a supernova search engine on an unprecedented scale. In the process, they discovered 42 new supernovae in the GOODS area, including 6 of the 7 most distant known.
Cosmologists understand almost nothing about dark energy even though it appears to comprise about 70 percent of the universe. They are desperately seeking to uncover its two most fundamental properties: its strength and its permanence.
In a paper to be published in the Astrophysical Journal, Riess and his collaborators have made the first meaningful measurement of the second property, its permanence.
Currently, there are two leading interpretations for the dark energy as well as many more exotic possibilities. It could be an energy percolating from empty space as Einstein’s theorized “cosmological constant,” an interpretation which predicts that dark energy is unchanging and of a prescribed strength.
An alternative possibility is that dark energy is associated with a changing energy field dubbed “quintessence.”
This field would be causing the current acceleration — a milder version of the inflationary episode from which the early universe emerged.
When astronomers first realized the universe was accelerating, the conventional wisdom was that it would expand forever. However, until we better understand the nature of dark energy–its properties–other scenarios for the fate of the universe are possible.
If the repulsion from dark energy is or becomes stronger than Einstein’s prediction, the universe may be torn apart by a future “Big Rip,” during which the universe expands so violently that first the galaxies, then the stars, then planets, and finally atoms come unglued in a catastrophic end of time. Currently this idea is very speculative, but being pursued by theorists.
At the other extreme, a variable dark energy might fade away and then flip in force such that it pulls the universe together rather then pushing it apart.
This would lead to a “big crunch” where the universe ultimately implodes. “This looks like the least likely scenario at present,” says Riess.
Understanding dark energy and determining the universe’s ultimate fate will require further observations. Hubble and future space telescopes capable of looking more than halfway across the universe will be needed to achieve the necessary precision. The determination of the properties of dark energy has become the key goal of astronomy and physics today.
So say we fast forward 10^30 years. Assuming that the universe is flat, and that the expansion rate (e. g. energy from the big bang) is able to just overpower gravity, as it now seems.
That universe will be an amazingly bleak place. Every star in the sky will have run out of fusion material long, long ago. Every galaxy will have been consumed by its super-massive black hole center. Any intelligent life will have presumably been sucked in too, if it made it that far. Maybe there will be some stray x-ray radiation from black hole accretion disks, but probalby not.
I don’t know which is bleaker — the big crunch, where the universe basically resets itself and tries again, or the big freeze, where the universe ‘lives’ in an un-dead state forever.
But this is all just philosophical masturbation — I should be much more concerned with my own demise ~ 10^(1.70) years from now. :-)
It’s a pity about closing down the Hubble, but there is a new satellite observatory on the drawing board, specifically to measure early/distant supernovas and thus changes in the expansion rate. The project is called the SuperNova Acceleration Probe.
Home site here.
Plenty of information in PDF form on the site. Quite interesting to see how advanced and tricky is the technology involved.
I’ve been thinking of my own mental musings prompted by Sciscoop articles as “brain massage.”
Somehow, “philosophical masturbation” has a nice ring to it. Thanks for the phrase, TK.