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8 Apr, 5 tweets, 1 min read
I want to expand on this a little... it's an issue that makes the POSSIBLE NEW PHYSICS announcement today a bit more complicated/caveat-y...
Both the measurement and the theory prediction for this experiment require INCREDIBLE precision. And the calculations are HARD. You have to account for how every particle known to science might interact with a muon, hypothetically, and exactly how that would affect its motion. 😳
One way to do this calculation is called the "data-driven" approach, which relies on generalizing from other precise measurements. The other is a new approach using supercomputers doing "lattice QCD" -- solving lots of very difficult equations on a very tight grid.
The new experimental result strongly disagrees with the Standard Model prediction when you calculate that with the standard "data-driven" approach, but does NOT disagree with the lattice QCD calculation (by a group calling themselves BMW). Which is intriguing in a couple of ways!
If the standard theory calculation is correct, we might have just found NEW PHYSICS with the experiment: hugely exciting! But if the lattice QCD one is correct, we have a THEORY mystery in why the calcs don't agree, which could ALSO turn out to be really interesting. Win-win! :)

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Katie Mack Profile picture
7 Apr
I've been tweeting a bunch of articles and threads about the #gminus2 result -- a possible indication of ✨ NEW PHYSICS ✨ coming from @Fermilab! Check my timeline for details, but I'll give a very brief and simplified summary here...
An experiment at @Fermilab is measuring a property of muons -- subatomic particles similar to electrons, but heavier -- to try to determine if our current understanding of particle physics is correct or not. The experiment hinges on the fact that muons are a tiny bit magnetic 🧲
The "Muon g-2" experiment measures how muons spin around and how that spin wobbles when they're sent around a circular track in the presence of strong magnetic and electric fields. That depends on how the muon spins and its "g-factor", related to its magnetism.
Read 11 tweets
Katie Mack Profile picture
8 Mar
New guidelines from the CDC for what might be okay for fully vaccinated people: cdc.gov/coronavirus/20…

Note: Dr. @RWalensky emphasized during the White House press conference that this is the best guidance RIGHT NOW but may change as conditions change and the science develops.
New CDC guidance:

"Fully vaccinated" (FV) = at least 2 weeks after final vaccine dose

* FV people can hang out in small groups with each other without masks

* FV people can hang out in small groups with LOW RISK unvaccinated people

* Non-essential travel still discouraged
The reason they're not saying fully vaccinated people can "just go out and do whatever" is partly because vaccines aren't 100% effective and partly because being vaccinated might not always prevent you from carrying the disease to others. (This is still being studied.)
Read 4 tweets
Katie Mack Profile picture
5 Mar
This is an amazing optical illusion — caused by atmospheric conditions over the water bending light rays to make it look like the ship is above it. This video has a nice explanation (especially the bit starting around 1:20) . #FataMorgana
The proper term for this is “superior mirage” or “superior looming mirage” but I have seen the term “fata morgana” used for a similar phenomenon also caused by weird kinds of light bending over the ocean.
More on superior mirages from @iansample. theguardian.com/science/2021/m…

Rather than "optical illusion" it might be better to call this an "optics illusion." Your brain is processing visual information correctly, it's just that the light deflection makes that information unreliable!
Read 5 tweets
Katie Mack Profile picture
4 Mar
Here’s a long-ish excerpt from my book where I talk about THE BIG RIP, one possibility for the end of the universe. (More likely is a Heat Death, caused by endless accelerated expansion, which *doesn’t* rip things apart. But a Big Rip would be fun too.) americanscientist.org/article/tearin…
I just saw a clip of Neil deGrasse Tyson on the Late Show saying that the Big Rip is likely coming and that it’s the necessary result of endless accelerated expansion, neither of which is true! So, see above for clarification.
If you’re interested in reading about what cosmologists are discovering now about how the universe might end, check out my book, “The End of Everything (Astrophysically Speaking)”! It’s accessible and comprehensive and has lots of funny footnotes astrokatie.com/book
Read 4 tweets
Katie Mack Profile picture
19 Feb
A thing a lot of people don't seem to be aware of is that the proportion of astronomers who believe there is alien life of some sort in the universe is almost 100%. It's just the proportion who think they've *dropped by* that's almost 0.
I had a radio interview recently where the host started out all challenging saying "It's UNTHINKABLE there isn't other life out there in the cosmos!" and I was like, "yeah, pretty much" and I think he was not really prepared for that
What we know is that we find life in just about every environment we look for it on Earth, wherever there's some amount of liquid water -- sometimes even just ice. And we know there is water on other worlds. And there are a LOT of other worlds. So: life seems likely to be common!
Read 4 tweets
Katie Mack Profile picture
7 Feb
Watching the snow fall outside and thinking about terminal velocity, and how much less peaceful this whole scene would look without air resistance. ❄️💥
Terminal velocity is the final speed something reaches when falling through a fluid (like air). The force of gravity accelerates the thing, and air resistance slows it down (in proportion to the square of the speed), so at some point those things balance and it stops speeding up.
Terminal velocity for a raindrop is around 9 meters/second. For a snowflake it’s generally closer to 2 meters/second, depending on the size and fluffiness of the flake. (Some formulae here hyperphysics.phy-astr.gsu.edu/hbase/airfri2.…)
Read 4 tweets

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