> They’re aiming for 50 million galaxies once the survey is complete... Sure, the DESI survey is less than 1% of all the galaxies in the observable volume of the cosmos
That just broke my brain. Had to look it up. 2+ trillion galaxies in the observable universe? That puts things in perspective all right
Each galaxy having a few thousand to millions of stars (for a dwarf galaxy), to 100-400 billion stars for a spiral galaxy like ours, to about a trillion stars for large ellipticals like Andromeda.
My dark energy/expansion of the universe thought experiment is still this: when you throw a ball up in an expanding universe, how fast does it come back down? This is (clearly) not my field but this basic question just seems to lead fun places. No matter how I think about this question I always come back to the idea that matter seems special in an expanding universe since it seems to extract energy from nothing if the universe is expanding uniformly. As we learn more I hope to get a good explanation for this question one day.
> They’re aiming for 50 million galaxies once the survey is complete... Sure, the DESI survey is less than 1% of all the galaxies in the observable volume of the cosmos
That just broke my brain. Had to look it up. 2+ trillion galaxies in the observable universe? That puts things in perspective all right
Each one thousands to hundreds of thousands of light years across, and with millions of light years between them.
Each galaxy having a few thousand to millions of stars (for a dwarf galaxy), to 100-400 billion stars for a spiral galaxy like ours, to about a trillion stars for large ellipticals like Andromeda.
Kind of a lot.
My dark energy/expansion of the universe thought experiment is still this: when you throw a ball up in an expanding universe, how fast does it come back down? This is (clearly) not my field but this basic question just seems to lead fun places. No matter how I think about this question I always come back to the idea that matter seems special in an expanding universe since it seems to extract energy from nothing if the universe is expanding uniformly. As we learn more I hope to get a good explanation for this question one day.
Is the cliffhanger question at the end of this post a question that has no current scientific answer or a question that tees up the next post?
I wish there was a prediction market for dark energy: real or fudge factor.