Let there be light
August 11, 2021 12:50 AM Subscribe
Physicists Detect Strongest Evidence Yet of Matter Generated by Collisions of Light.
If you smash some photons together with enough energy you get matter!!!!
Go figure.
Don't make light of the matter! This discovery really matters!!!
But besides bad turn of phrase - this is amazing!
posted by AnTilgangs at 1:15 AM on August 11, 2021 [3 favorites]
But besides bad turn of phrase - this is amazing!
posted by AnTilgangs at 1:15 AM on August 11, 2021 [3 favorites]
Important technology for teleportation fans there. (Gamma ray lasers may be taking a step closer to becoming a reality too, apparently)
posted by rongorongo at 2:56 AM on August 11, 2021 [1 favorite]
posted by rongorongo at 2:56 AM on August 11, 2021 [1 favorite]
What I found interesting was the virtual photons:
Time to break out the textbooks and the paper to see if that can shed some light on these virtual photons.
posted by sudogeek at 4:02 AM on August 11, 2021 [5 favorites]
That's because the photons produced by the electromagnetic interaction are virtual photons, popping briefly in and out of existence, and without the same mass as their 'real' counterparts. To be a true Breit-Wheeler process, two real photons need to collide - not two virtual photons, nor a virtual and a real photon.So there are random ‘real’ photons about, traveling here and there at c as is their wont, while there are also virtual photons created during the passage of the gold nucleus which have less mass (I presume that’s shorthand for momentum), because they are effectively traveling at less than c? Or their ‘mass’ (i.e., momentum) is less because of some sort of time averaging and approaches that of a real photon as they approach c? Yet, they are real enough to collide and produce electron-positron pairs but at a reduced energy.
At the ions' relativistic speeds, the virtual particles can behave like real photons. Thankfully, there's a way physicists can tell which electron-positron pairs are generated by the Breit-Wheeler process: the angles between the electron and the positron in the pair generated by the collision.
Time to break out the textbooks and the paper to see if that can shed some light on these virtual photons.
posted by sudogeek at 4:02 AM on August 11, 2021 [5 favorites]
So there are random ‘real’ photons about, traveling here and there at c as is their wont, while there are also virtual photons created during the passage of the gold nucleus which have less mass
Other way around: Real photons are massless, virtual photons can appear to have mass.
An incorrect hand-wavy explanation: Virtual photons don't quite obey the energy-momentum equations as you would expect, because of uncertainty principle weirdness. They conserve energy and momentum, but end up with an apparent mass (known as being "off mass shell"). The experiment in the article is using the differences in properties between real/long-lived photons and virtual/short-lived photons to distinguish the two.
posted by Eleven at 4:28 AM on August 11, 2021 [6 favorites]
Other way around: Real photons are massless, virtual photons can appear to have mass.
An incorrect hand-wavy explanation: Virtual photons don't quite obey the energy-momentum equations as you would expect, because of uncertainty principle weirdness. They conserve energy and momentum, but end up with an apparent mass (known as being "off mass shell"). The experiment in the article is using the differences in properties between real/long-lived photons and virtual/short-lived photons to distinguish the two.
posted by Eleven at 4:28 AM on August 11, 2021 [6 favorites]
What I found interesting was the virtual photons:
Me too! If you go to the article on the webpage of Brookhaven (linked in OP's post, but you have to hunt a little) they do a better job of distinguishing the virtual photons (created, if I understand correctly, by interactions between charged particles such as those in the the ion beams) from the 'real' photons, created by the interactions of the particle accelerator's magnetic field, and the magnetic field induced by the particle beam itself. Those two magnetic fields have to be the same strength and orthogonal to each other, which (and this is the bit missing in the sciencealert article) 'that arrangement of perpendicular electric and magnetic fields of equal strength is exactly what a photon is—a quantized “particle” of light.'
posted by Omission at 4:35 AM on August 11, 2021 [5 favorites]
Me too! If you go to the article on the webpage of Brookhaven (linked in OP's post, but you have to hunt a little) they do a better job of distinguishing the virtual photons (created, if I understand correctly, by interactions between charged particles such as those in the the ion beams) from the 'real' photons, created by the interactions of the particle accelerator's magnetic field, and the magnetic field induced by the particle beam itself. Those two magnetic fields have to be the same strength and orthogonal to each other, which (and this is the bit missing in the sciencealert article) 'that arrangement of perpendicular electric and magnetic fields of equal strength is exactly what a photon is—a quantized “particle” of light.'
posted by Omission at 4:35 AM on August 11, 2021 [5 favorites]
Matter and antimatter. If they were producing more of one than the other that would be extra interesting, because we still don't know why the universe has more matter than antimatter. Maybe further experimentation of this sort will give us a hint.
posted by swr at 7:10 AM on August 11, 2021 [2 favorites]
posted by swr at 7:10 AM on August 11, 2021 [2 favorites]
A particle of light is an arrangement of perpendicular electric and magnetic fields of equal strength. Hunh. Trying to wrap my head around that. Physics is amazing.
posted by Don.Kinsayder at 8:05 AM on August 11, 2021 [3 favorites]
posted by Don.Kinsayder at 8:05 AM on August 11, 2021 [3 favorites]
So, do we think that this is the process by which matter was created during the big bang?
The process involves, as the collider's name suggests, accelerating ions - atomic nuclei stripped of their electrons.
This kind of sounds like a classic folk-tale, a man tracks down and locates a god, strips him of his attendants, and forces him to race, and when he races he barfs up a nugget of iron, but the iron is cursed....
posted by bleep at 10:50 AM on August 11, 2021 [3 favorites]
The process involves, as the collider's name suggests, accelerating ions - atomic nuclei stripped of their electrons.
This kind of sounds like a classic folk-tale, a man tracks down and locates a god, strips him of his attendants, and forces him to race, and when he races he barfs up a nugget of iron, but the iron is cursed....
posted by bleep at 10:50 AM on August 11, 2021 [3 favorites]
Digging deeper into the Brookhaven article answered my big question, which was how they manage to actually measure the different angles of the collisions, and it's actually another "find" from these experiments. turns out that the super-strong magnetic fields are able to polarize the photons which means that some of them pass through and some of them are absorbed, similar to light waves through polarized sunglasses.
"This is the first Earth-based experimental observation that polarization affects the interactions of light with the magnetic field in the vacuum—the vacuum birefringence predicted in 1936. "
Pretty cool.
posted by OHenryPacey at 11:09 AM on August 11, 2021 [1 favorite]
"This is the first Earth-based experimental observation that polarization affects the interactions of light with the magnetic field in the vacuum—the vacuum birefringence predicted in 1936. "
Pretty cool.
posted by OHenryPacey at 11:09 AM on August 11, 2021 [1 favorite]
Iʻm buying the next icebox incorporating "birefringence"; e.g., the Birefringerator.
posted by Droll Lord at 1:41 PM on August 11, 2021 [2 favorites]
posted by Droll Lord at 1:41 PM on August 11, 2021 [2 favorites]
Or maybe the next vacuum.
posted by Droll Lord at 1:42 PM on August 11, 2021
posted by Droll Lord at 1:42 PM on August 11, 2021
Iʻm buying the next icebox incorporating "birefringence"; e.g., the Birefringerator.
Make sure it's Bi(re)frost free, or you'll have random Asgardians jumping into your kitchen at all hours.
posted by OHenryPacey at 2:21 PM on August 11, 2021 [2 favorites]
Make sure it's Bi(re)frost free, or you'll have random Asgardians jumping into your kitchen at all hours.
posted by OHenryPacey at 2:21 PM on August 11, 2021 [2 favorites]
All right, questions. If a photon is a quantum of electromagnetic energy (by definition, the smallest unit), and photons travel at the speed of light (and not any faster), then why does the article say "the photons need to be extremely energetic." How can one quantum of electro-magnetic energy always traveling at the speed of light be more energetic than another one? Is it that when they collide, the kinetic energy of the collision contributes to the collective energy of the particle? I guess that would make sense special relativity-wise.
Also, photons and electrons and positrons are fundemental elementary particles. So it's weird that you can add two high-energy photons and produce an electron and positron, or conversely add an electron and a positron to produce a photon, which then becomes a quark and an antiquark, which itself spits out a gluon. I mean, it seems like fundamental particles are not so fundamental, right?
posted by jabah at 8:12 PM on August 11, 2021
Also, photons and electrons and positrons are fundemental elementary particles. So it's weird that you can add two high-energy photons and produce an electron and positron, or conversely add an electron and a positron to produce a photon, which then becomes a quark and an antiquark, which itself spits out a gluon. I mean, it seems like fundamental particles are not so fundamental, right?
posted by jabah at 8:12 PM on August 11, 2021
Huh.... What if it's just like, all little ripples that got knotted up in different ways....
posted by rebent at 8:21 PM on August 11, 2021 [2 favorites]
posted by rebent at 8:21 PM on August 11, 2021 [2 favorites]
How can one quantum of electro-magnetic energy always traveling at the speed of light be more energetic than another one?
It is the quantum at a given frequency - higher frequency photons have more energy.
posted by save alive nothing that breatheth at 8:23 PM on August 11, 2021 [2 favorites]
It is the quantum at a given frequency - higher frequency photons have more energy.
posted by save alive nothing that breatheth at 8:23 PM on August 11, 2021 [2 favorites]
I mean, it seems like fundamental particles are not so fundamental, right?
It’s turtles all the way down, man.
posted by Big Al 8000 at 9:54 PM on August 11, 2021
It’s turtles all the way down, man.
posted by Big Al 8000 at 9:54 PM on August 11, 2021
It’s turtles all the way down, man.
Eventually you get to the level of terrapinions and testudions. The math for calculating the orbital shells is pretty complicated.
posted by notoriety public at 4:53 AM on August 12, 2021 [6 favorites]
Eventually you get to the level of terrapinions and testudions. The math for calculating the orbital shells is pretty complicated.
posted by notoriety public at 4:53 AM on August 12, 2021 [6 favorites]
Okay, now I understand how one photon can be more energetic than another. If the photon is thought of as a wave that travels at the speed of light, and the speed of light = frequency x wavelength, then the higher the frequency (and energy), the lower the wavelength. So I guess the frequency (i.e., energy) of the photon is determined here by the strength of the interacting magnetic and electric fields inside the collider?
posted by jabah at 7:09 AM on August 12, 2021
posted by jabah at 7:09 AM on August 12, 2021
« Older A[BillionBillionBillion]undant Prochlorococcus | Scooter theft success story Newer »
This thread has been archived and is closed to new comments
posted by fairmettle at 1:05 AM on August 11, 2021 [2 favorites]