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berkeman's latest activity
berkeman
reacted to
Gleb1964's post
in the thread
B
Questions about the Paraxial equation for a single spherical surface
with
Like
.
In your first message you was asked about paraxial equation, but your picture was about exact real ray tracing in meridional plane, not...
Today, 1:22 PM
berkeman
reacted to
somegrue's post
in the thread
COVID
Is it usual for vaccine injection site to hurt again during infection?
with
Like
.
As I said, none of the risk factors they mention apply, so I can't imagine it having been that cut and dry in my case. What I can easily...
Today, 12:06 PM
berkeman
reacted to
Ibix's post
in the thread
Stargazing
Dark matter and its effect on the orbit of stars
with
Informative
.
Black holes have been considered, yes. You need more than thousands of them - you need more mass in them than there is in the visible...
Today, 12:01 PM
berkeman
reacted to
bhobba's post
in the thread
B
Excellent Free Course On Einsten, Relativity, His Views Etc from Harvard
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Like
.
Hi All I just finished the following course on Einstein and Relativity...
Today, 11:39 AM
berkeman
replied to the thread
A
Relation between nuclear shape and it spin number
.
Welcome to PF, Renato. :smile: Paging @Dale
Today, 11:26 AM
berkeman
reacted to
somegrue's post
in the thread
COVID
Is it usual for vaccine injection site to hurt again during infection?
with
Informative
.
I tried googling before posting, but failed to come up with search terms that distinguished this from descriptions of the initial...
Today, 11:01 AM
berkeman
replied to the thread
COVID
Is it usual for vaccine injection site to hurt again during infection?
.
Nice find! At least that makes some sense from a biological point of view. Any chance your last vaccination may have ended up Sub-Q...
Today, 11:01 AM
berkeman
replied to the thread
Have your mind blown by a motorcycle travel blog
.
I wonder what that thing is...
Today, 10:58 AM
berkeman
reacted to
docnet's post
in the thread
Have your mind blown by a motorcycle travel blog
with
Like
.
Here's a travel blog by a couple from Estonia, who ride their BMW motorcycle 200,000km and to 85 countries around the world. Proper...
Today, 10:57 AM
berkeman
reacted to
f95toli's post
in the thread
A
Flash memory and electron tunneling
with
Informative
.
No, that is not correct. An atom is of the order of 0.1nm (=1 Angstrom) "wide". The typical thickness for the oxide layers used in...
Today, 10:53 AM
berkeman
reacted to
Baluncore's post
in the thread
What is global warming due to?
with
Like
.
The debate is over. We have had many ice-ages since the dinosaurs. The continents have drifted to, and from the poles, along well known...
Today, 10:52 AM
berkeman
reacted to
painter's post
in the thread
B
Generating Energy from Molecular Motion
with
Like
.
I got it !! Thank you veeeeery much😃😃😃🤩
Today, 9:58 AM
berkeman
reacted to
Rive's post
in the thread
Silly question about series batteries
with
Like
.
The maximal current will depend on the lone series battery, which will get the worst load/usage and will die first. I would prefer...
Today, 9:49 AM
berkeman
replied to the thread
COVID
Is it usual for vaccine injection site to hurt again during infection?
.
How long ago did you get the COVID vaccination? Was it in your right or left deltoid? Have you had multiple COVID vaccinations? If...
Today, 9:03 AM
berkeman
reacted to
Ibix's post
in the thread
Format for Mathematical Expressions
with
Informative
.
Note that some forums use \[ and \] to delimit LaTeX (I think that's the MathJax default setting, in fact), so if you are often seeing...
Today, 8:53 AM
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