I read the article but didn't watch the videos yet, but I'm curious as to what would be needed to make this a 3D map. That is, I'm assuming this 2D map records the position of all of these objects in the sky, but not the distance from Earth. But I thought that calculating the distance of objects is relatively straightforward, e.g. you hear all the time "Galaxy X is 2 billion lightyears away" or whatever. Would it just be really computationally expensive to calculate the distance to all of the 4 billion objects identified in the map?
They do this mostly with spectroscopy, breaking out the light by frequency. The longer the light has been travelling, the more frequency shifts into redder frequencies, because the universe is continually expanding.
But those distances are all built on top of the cosmic distance ladder (Terence Tao explaining on 3blue1brown)
There are a lot of unknowns and processes that must be undone, which often require an unknown basis. Red shift, moving bodies, gravitational lensing and other processes distort light along its journey. Sometimes we don't know the exact magnitude of a star, etc. Spectroscopy helps a lot but is limited by the fidelity of our datasets.
I will add that it is said the universe is flat, but that does not mean 2d flat. Flat is a mathematical construct, which means parallel lines stay parallel and triangle angles sum to 180 degrees. So it is 3d flat at least as far as we can observe.
But the universe is not flat. Galaxies are all over the place.
So, I was mistaken.
But, just to be clear: I am not a flat earther! Flat is relative here. The thickness of our galaxy is not measured in kilometers ofc. It is just that within the same units , solar systems and galaxies are flat relative to their length.
Comments
I read the article but didn't watch the videos yet, but I'm curious as to what would be needed to make this a 3D map. That is, I'm assuming this 2D map records the position of all of these objects in the sky, but not the distance from Earth. But I thought that calculating the distance of objects is relatively straightforward, e.g. you hear all the time "Galaxy X is 2 billion lightyears away" or whatever. Would it just be really computationally expensive to calculate the distance to all of the 4 billion objects identified in the map?
They do this mostly with spectroscopy, breaking out the light by frequency. The longer the light has been travelling, the more frequency shifts into redder frequencies, because the universe is continually expanding.
But those distances are all built on top of the cosmic distance ladder (Terence Tao explaining on 3blue1brown)
https://youtu.be/YdOXS_9_P4U?is=jbkFbwWKgbn3yOjq
Maps like DESI add the 3d distances.
https://www.desi.lbl.gov/education-outreach/interactive-visu...
There are a lot of unknowns and processes that must be undone, which often require an unknown basis. Red shift, moving bodies, gravitational lensing and other processes distort light along its journey. Sometimes we don't know the exact magnitude of a star, etc. Spectroscopy helps a lot but is limited by the fidelity of our datasets.
Celestia might be what you're looking for.
I think it is 2D because the universe is not that thick?
I will add that it is said the universe is flat, but that does not mean 2d flat. Flat is a mathematical construct, which means parallel lines stay parallel and triangle angles sum to 180 degrees. So it is 3d flat at least as far as we can observe.
I was mistaken.
Our solar system is flat.
Galaxies are mostly flat.
But the universe is not flat. Galaxies are all over the place.
So, I was mistaken.
But, just to be clear: I am not a flat earther! Flat is relative here. The thickness of our galaxy is not measured in kilometers ofc. It is just that within the same units , solar systems and galaxies are flat relative to their length.