PeterDonis's latest activity
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PeterDonis replied to the thread High School Gravitons/Gravity passing through objects.This paper by Deser summarizes how the full nonlinear massless spin-2 QFT is derived, with classical GR as its classical limit... -
PeterDonis replied to the thread High School Gravitons/Gravity passing through objects.This was thought to be the case when Feynman's book was published, but it turns out it's not. See below. If you're referring to the...
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PeterDonis reacted to Paul Colby's post in the thread High School Gravitons/Gravity passing through objects with
Like.
The graviton (at least initially) is an idea that stems from applying local quantum field theory techniques to linearized GR. The... -
PeterDonis reacted to Klystron's post in the thread Artemis 2 launch - humans return to the Moon after 54 years with
Haha.
Well I met Buzz Aldrin a few times when I worked at NASA Ames. He definitely appeared human. Not as sure about Neil Armstrong <joke>... -
PeterDonis replied to the thread Undergrad Black hole questions.To be clear, we don't actually have evidence of an event horizon. We only have evidence of apparent horizons--very heuristically...
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PeterDonis replied to the thread Undergrad Black hole questions.In the sense that we don't expect stress-energy to just disappear, that's true. However, it's also true that we do expect a black hole...
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PeterDonis replied to the thread Artemis 2 launch - humans return to the Moon after 54 years.I suspect the enhancement algorithm made use of outside knowledge about what Earth looks like from space--for example, what clouds look...
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In "realistic" models of collapsing stars in GR, the matter reaches the singularity and leaves our model. Its gravitational effect...
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PeterDonis replied to the thread Undergrad Black hole questions.And your clarifications showed that your usage was not correct, in the way I pointed out. In that spacetime diagram, an object "at...
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PeterDonis replied to the thread Artemis 2 launch - humans return to the Moon after 54 years.Yes. That's because that version of the photo was put through an enhancement algorithm to brighten the night side. Here's what it...
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PeterDonis replied to the thread Undergrad Black hole questions.No. It's not even part of the spacetime. It's not. No, that's not correct. Look at a Kruskal diagram, as seen, for example, in this...
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PeterDonis reacted to Klystron's post in the thread Artemis 2 launch - humans return to the Moon after 54 years with Like.
Among many Artemis II websites this simple NASA program called Arow is my favorite for tracking mission progress...
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PeterDonis replied to the thread Artemis 2 launch - humans return to the Moon after 54 years.Similar to the goal of Apollo 8, as compared to Apollo 11. (And to date myself, I watched Apollo 11 on TV as a preschooler--a small...
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PeterDonis replied to the thread Artemis 2 launch - humans return to the Moon after 54 years.@mfb summarized this in the OP of the thread.
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PeterDonis replied to the thread Undergrad Relativistic Uniform Circular Motion.Yes, it does.