Of Particular Significance

Category: General Relativity

Innovations in Data Collection at the LHC

Geneva, Switzerland, is not known for its sunny weather, and seeing the comet here was almost impossible, though I caught some glimpses. I hope many of you have seen it clearly by now. It’s dim enough now that dark skies and binoculars are increasingly essential.

I came here (rather than the clear skies of, say, Morocco, where a comet would be an easier target) to give a talk at the CERN laboratory — the lab that hosts the Large Hadron Collider [LHC], where the particle known as the Higgs boson was discovered twelve years ago. This past week, members of the CMS experiment, one of the two general purpose experiments at the LHC, ran a small, intensive workshop with a lofty goal: to record vastly more information from the LHC’s collisions than anyone would have thought possible when the LHC first turned on fifteen years ago.

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POSTED BY Matt Strassler

ON October 21, 2024

The Sun Sets on Old Rules at CERN

It’s been quite a week… Spectacular northern lights for hours on Thursday night. A great comet in the evening skies (though so far I’ve have only caught glimpses, thanks to atrocious viewing conditions.) And now, I’m at CERN (the pan-European particle physics laboratory) for the first time since the pandemic began. I’ll be giving a talk at a conference of CMS experimenters. (CMS and ATLAS are the two general purpose experiments at the Large Hadron Collider [LHC].)

The topic of the workshop is a novel technique called “Level-1 Scouting” — though it isn’t really about “scouting” for anything. It has to do with evading the strait-jacket of the trigger, an essential feature of data gathering at each of the LHC experiments. With tens of millions of collisions per second, the data flood at CMS is too great, and only a tiny fraction of these collisions can be stored. The trigger decides real-time which ones to keep and which ones to discard forever. That’s been the basic rule since the LHC began running.

But this rule no longer applies, thanks to new technology and human ingenuity. CMS now uses level-1 scouting to record sketchy information about every single collision that happens in their detector. LHCb, with a smaller detector, was the first to try something along these lines. ATLAS is on a parallel track. These developments have the potential, looking ahead, to substantially enhance the capability of these detectors. More about this after I’ve given my talk.

Auroras after sunset. (These were as bright to the naked eye)

Comet A3 after sunset. (Brighter than to the naked eye.)

Post-sunset light over CERN. (As to the naked eye.)

POSTED BY Matt Strassler

ON October 14, 2024

Auroras, Yes!! Comet, No.

I hope many of you saw auroras (northern lights) last night! I briefly saw the strongest steady red glow I myself have ever observed, visible even amid street lights and my neighbors’ house lights.

*The skies, shown only slightly brighter than to the naked eye, as seen at 8pm Boston time. Credit: Matt Strassler*

Then, after a break as some clouds rolled in, we were graced with a few hours of mostly diffuse green glow with patches of dim but distinct red that would come and go. All these colors were visible with the naked eye, albeit much less bright than shown in photos. It was quite a storm, not as violently active as the one earlier this year, but very persistent.

*The storm lasted all night, though the auroras varied greatly in brightness. Data from https://www.swpc.noaa.gov/*

I also tried to find Comet A3 just after sunset, but failed, even with the help of binoculars. Apparently the brief spike in its brightness, due to “forward scattering” as it passed between us and the Sun, may have died off too quickly, leaving it impossible to see in early twilight. It will become dimmer day by day, but it will also be visible later each evening, and at some point should become easy to see in dark skies. Let me know when you first observe it!

POSTED BY Matt Strassler

ON October 11, 2024

Auroras? Comet? Maybe Both Tonight

It could be quite a night!

A powerful solar flare (an explosion on the Sun) about 36 hours ago created a large and fast coronal mass ejection (a cloud of subatomic particles heading away from the Sun) that is due to arrive at Earth in the next few hours (it will show up less than an hour before it arrives as chaos in this data.) UPDATE: IT HAS ARRIVED; IF IT’S DARK WHERE YOU ARE, GO LOOK. That could mean problems for the electrical grid. It could also mean strong auroras (northern and southern lights) far from the poles. The timing, if correctly predicted, is such that Asia and Europe may have the best chances, but the auroras could potentially last until it is dark in the Americas too.

Also, just after sunset tonight, we may with difficulty be able to see Comet A3 (short for Comet C/2023 A3 Tsuchinshan-ATLAS ). The comet is bright — some reports give it a brightness comparable to the planet Venus, although more diffuse — but so is twilight. UPDATE: I HAVE BEEN WARNED THAT THE RAPID BRIGHTNING PERIOD, DUE TO A LIGHT SCATTERING EFFECT, MAY ALREADY BE OVER. IF SO, THE STATEMENTS HERE MAY BE TOO OPTIMISTIC. The comet is roughly ten Sun-widths above and slightly to the right of the Sun, and should be visible 15-30 minutes after sunset if you have a low and mostly cloudless horizon. Best bet is to bring binoculars and scan the sky; you’ll notice it much more easily, even if it is visible to the naked eye.

Each day following, the comet will be higher in the sky at sunset, making it more visible in late twilight, but it will also become intrinsically dimmer. Experts seem to disagree about when it will be at its best, but this weekend should be good, if not before.

Added 5pm NYC time : Here’s what the data looked like showing the arrival of the coronal mass ejection, a few hours ago, at the ACE satellite, which gives us about an hour’s warning here on Earth:

Added 5pm NYC time: Here’s what the data looks like showing an ongoing geomagnetic storm and likely auroras; warning, the data is delayed 3 hours, so it’s not showing you what’s happening right now. “UTC” is 5 hours ahead of New York (i.e. Eastern) time, one hour behind Central European time.

POSTED BY Matt Strassler

ON October 10, 2024

This is it! The Best Week for Comet A3!

A busy news week: a Nobel prize, another chance of auroras, and… a comet. It’s probably not the comet of the century, but comets like this one show up only about once every ten years. This one has already been visible in early morning skies. This week it enters our evening skies, and will likely be a lovely sight after dark for the rest of October.

Thursday, Friday and Saturday this week, immediately after sunset and just to the right and above the Sun, comet A3 MAY be at its most spectacular. BE READY! You will need a low and rather flat horizon, and you have less than an hour to see it before it sets, too.

*Day by day, the comet will move up and to the left, beginning at the Sun’s right. Look there once the Sun is significantly below the true horizon and the sky has darkened a bit.*

Later in the month it will be visible longer into the evening, but much less bright.

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POSTED BY Matt Strassler

ON October 8, 2024

Two Blasts From The Sun May Herald Weekend Auroras

[Second update: Sunday 9pm New York time: Auroras are being seen tonight. A bit fleeting for those of us in central New England, but they have been seen as far south as the Boston area, and are currently being seen further north.]

[Update: one coronal mass ejection arrived very early Sunday morning. But the impact seems to have been weak, with no auroras resulting. Aurora forecasting is still not very accurate… these solar flares were very big, but nevertheless, didn’t do much for us yet, and it’s getting late…]

Quick note: two powerful solar flares occurred in the last 72 hours, creating high spikes in the rate of X-rays from the Sun.

Each flare created a coronal mass ejection that could arrive in a couple of days at Earth, potentially creating a geomagnetic storm. Consequently there’s a good probability this weekend, especially Saturday night into Sunday morning (in Europe and the US), of seeing northern and southern lights (auroras). [See this post for some advice as to how to infer whether the storms have started and/or are ongoing.]

POSTED BY Matt Strassler

ON October 4, 2024

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Category: General Relativity

Innovations in Data Collection at the LHC

POSTED BY Matt Strassler

The Sun Sets on Old Rules at CERN

POSTED BY Matt Strassler

Auroras, Yes!! Comet, No.

POSTED BY Matt Strassler

Auroras? Comet? Maybe Both Tonight

POSTED BY Matt Strassler

This is it! The Best Week for Comet A3!

POSTED BY Matt Strassler

Two Blasts From The Sun May Herald Weekend Auroras

POSTED BY Matt Strassler

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