Tag Archives: cosmology

Black Hole Lifetimes

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Black holes are not totally black! They will evaporate by Hawking radiation. This is required by Thermodynamics and Quantum Mechanics. All properties of a Schwarzschild Black are determined by its mass, so if you know the mass the lifetime and other properties follow automatcally. Or you can start with the lifetime and determine the initial mass. Or the Schwarzschild radius, or the temperature, or the entropy, etc. For black holes comparable in mass to “normal” astronomical objects this lifetime is much longer than the current age of the universe. Viktor Toth’s Hawking radiation calculator is a convenient tool for such calculations. Here are some results:

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The mass of Dark Matter particles

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An email from Cosmoquest led me to find Physicists Narrow Range of Potential Masses for Dark Matter Candidate articles. Technical details at Theoretical bounds on dark matter masses and on the Arxiv. The mass range is 10−3eV≲mφ≲107eV. Thus we have a range from neutrino masses (still very uncertain, but nonzero) up to about 1/10 the mass of a muon. This appears to exclude WIMPs, which were already in trouble. This also suggests that finding dark matter is not a justification for building a more powerful particle accelerator than the LHC; 107eV is well within the range of the LHC and other current devices.

We still do not have a complete theory of quantum gravity, but apparently enough is understood to make such calculations possible. I am looking forward to seeing what other theoretical physicists say about this.

Supernovae

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I went (via Zoom) to a great lecture last night. Serafina Nance spoke to the The Calgary Centre of the Royal Astronomical Society of Canada on Tracing the Lives, Deaths, and Explosions of Massive Stars.

Supernovae are cosmic events of gigantic power. Their explosions can shine as bright as a galaxy, a pinprick of extraordinarily bright light in the night sky. What is less well-understood, however, is which stars reach the point of explosion and how they evolve to their deaths. Interestingly, their explosions provide astronomers with key tools to uncover fundamental aspects of our Universe. While we know that the Universe is expanding at an accelerated rate due to dark energy, the rate of the expansion of the Universe is not well-constrained. Supernovae provide us with independent ways to measure this expansion and work to resolve one of the most pivotal questions in astronomy: How fast is the Universe really expanding?
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Nobel Vintage

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Fundamental Physics Prize Co-Winner Sells No Wine Before Its Time

Brian Schmidt is the world’s only vintner with a Nobel Prize in physics, specializing in pinot noir because the climate and soil (or terroir) is especially well suited for that varietal. He and is wife own a four-star winery called Maipenrai (Thai for “It’s all right”) in Sutton, New South Wales, near Canberra.