In a very active thread here in this board, a couple of astronomy/astrophysics/cosmology topics have come up which many regular readers may not have heard of.
First, expansion of the universe. Yeah, the results are pretty clear: if General Relativity (GR), then the universe seems to be expanding. Expansion which is accelerating.
But it's all very indirect ... wouldn't it be cool to measure the line-of-sight speed of a galaxy, and next year repeat the measurement to see if that speed has increased?
A completely hopeless task you might say, the expected change in speed is utterly miniscule, how could you possibly measure it?
This Is How Astronomers Will Finally Measure The Universe's Expansion Directly, by Ethan Siegel explains how (maybe). Hat tip to Reality Check.
In short, a humongous telescope plus astonishing technical feats, and examining the spectra of a lot of distant quasars, over two+ decades might give a robust answer! :thumbsup: :)
For more detail, check out this 2008 paper (link to arXiv abstract) by Liske et al. Cosmic dynamics in the era of Extremely Large Telescopes. The key technology is "laser frequency combs" check out this 2007 paper (link to arXiv abstract) by Murphy et al. for details: High-precision wavelength calibration of astronomical spectrographs with laser frequency combs.
Next: the cosmic web and filaments.
First, expansion of the universe. Yeah, the results are pretty clear: if General Relativity (GR), then the universe seems to be expanding. Expansion which is accelerating.
But it's all very indirect ... wouldn't it be cool to measure the line-of-sight speed of a galaxy, and next year repeat the measurement to see if that speed has increased?
A completely hopeless task you might say, the expected change in speed is utterly miniscule, how could you possibly measure it?
This Is How Astronomers Will Finally Measure The Universe's Expansion Directly, by Ethan Siegel explains how (maybe). Hat tip to Reality Check.
In short, a humongous telescope plus astonishing technical feats, and examining the spectra of a lot of distant quasars, over two+ decades might give a robust answer! :thumbsup: :)
For more detail, check out this 2008 paper (link to arXiv abstract) by Liske et al. Cosmic dynamics in the era of Extremely Large Telescopes. The key technology is "laser frequency combs" check out this 2007 paper (link to arXiv abstract) by Murphy et al. for details: High-precision wavelength calibration of astronomical spectrographs with laser frequency combs.
Next: the cosmic web and filaments.
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