9 Billion-Year-Old "Dark Energy" Reported 118
loid_void writes to mention a New York Times article about the discovery that dark energy, or antigravity, was present at the formation of the universe. A team of 'dark energy prospectors' at the Space Telescope Science Institute theorizes that this may have directed the evolution of the cosmos. By observing supernova activity almost 8 billion years in the past, the team was able to study whether or not dark energy has changed over the millennia. From the article: "The data suggest that, in fact, dark energy has changed little, if at all, over the course of cosmic history. Though hardly conclusive, that finding lends more support to what has become the conventional theory, that the source of cosmic antigravity is the cosmological constant, a sort of fudge factor that Einstein inserted into his cosmological equations in 1917 to represent a cosmic repulsion embedded in space. Although Einstein later abandoned the cosmological constant, calling it a blunder, it would not go away. It is the one theorized form of dark energy that does not change with time. Sean Carroll, a cosmologist at the California Institute of Technology who was not on the team, said: 'Had they found the evolution was not constant, that would have been an incredibly earthshaking discovery. They looked where no one had been able to look before.'"
More from Sean Carroll (Score:5, Informative)
He provides a great explanation for the reader without familiarity with advanced physics, but at a level which is still interesting to the technical reader.
Re:Does this really mean anything... (Score:2, Informative)
Wikipedia [wikipedia.org] can.
Antigravity? I for one ... (Score:0, Informative)
Re:This history is getting twisted (Score:4, Informative)
Nonetheless, Einstein's cosmological constant is not just a fudge factor he introduced. The equations of general relativity are the most general equations you can write down consistent with certain principles (the equivalence of gravitational and inertial mass, among others). The main terms relate the curvature of space to the local matter/energy distribution, but there is one more term which is consistent with the principles and should be included - the cosmological constant. The constant may be zero, of course, but a priori it's something you need to understand. Einstein chose a particular value of the constant to produce a static universe - a blunder, since he could have realized that almost any value of the constant gives an expanding or contracting universe.
Re:Anyone here care to try to poke holes in this? (Score:3, Informative)
It does.
Actually, I think I just agreed with you except if that were the case then that would mean the universe isn't actually expanding, but rather the observations we are getting from other galaxies is itself changing because of increased gravity we get the shift in the spectrum by getting less and less of that energy from other galaxy.
This is a sensible suggestion - it is called the 'tired light' idea. The reason we know it isn't the case is that light is not red shifting down the spectrum, but signals are getting stretched in length as well - space really is expanding.
Of course I am a complete layman when it comes to these things, but I think that gravity has to be affecting our observations of other galaxies in someway.
It certainly does. This is why we get gravitational lensing.
Still... Why doesn't the universe collapse then? Or maybe it is and we can't really observe it? So I don't know if that works either.
Because there may be more forces that just gravity.