“Even if I stumble on to the absolute truth of any aspect of the universe, I will not realise my luck and instead will spend my life trying to find flaws in this understanding – such is the role of a scientist.” -Brian Schmidt
The discovery of the accelerated expansion of the Universe — and of dark energy behind it — in 1998 was one of the biggest physics revolutions of our lifetime. By measuring these distant galaxies and how their distances and redshifts scale in the Universe, we were able to determine that despite everything we knew about matter and radiation, there was an additional force at play, and it caused distant galaxies to accelerate away from us.
How matter (top), radiation (middle), and a cosmological constant (bottom) all evolve with time in an expanding Universe. Image credit: E. Siegel, from his book, Beyond the Galaxy.
The data is now good enough to determine that dark energy is extremely close, if not identical, to the predictions of a cosmological constant. But there are still other theoretical possibilities that are admissible, even if they aren’t favored. Perhaps in the coming decades, we’ll find out that the ‘Big Freeze’ isn’t necessarily ...