{"id":2688,"date":"2021-09-06T06:00:00","date_gmt":"2021-09-06T06:00:00","guid":{"rendered":"https:\/\/modernsciences.org\/staging\/4414\/?p=2688"},"modified":"2021-09-09T02:27:19","modified_gmt":"2021-09-09T02:27:19","slug":"physicists-may-have-demonstrated-einsteins-most-famous-equation-using-virtual-photons","status":"publish","type":"post","link":"https:\/\/modernsciences.org\/staging\/4414\/physicists-may-have-demonstrated-einsteins-most-famous-equation-using-virtual-photons\/","title":{"rendered":"Physicists May Have Demonstrated Einstein\u2019s Most Famous Equation Using \u201cVirtual\u201d Photons"},"content":{"rendered":"\n

E = mc2<\/sup><\/h2>\n\n\n\n

You most likely already know what is perhaps Einstein\u2019s most famous equation. You might not know what it stands for, but you remember how it goes. You might not have even cemented Pythagoras\u2019 famous theorem into your head yet\u2014probably not for a year or two\u2014and you might have already known how it\u2019s written out: E = mc<\/em>2<\/sup><\/em>.<\/p>\n\n\n\n

The famous equation, known formally as the mass-energy equivalence<\/em>, describes how mass and energy are essentially the same physical entity, and can thus be converted from one to the other. Detailed in Albert Einstein\u2019s theory of special relativity, the energy of a body at rest, described as E<\/em>, is equivalent to its mass at rest m<\/em> multiplied with the square of the speed of light in a vacuum c<\/em> (299,792,458 m\/s, ~671 million miles per hour). It\u2019s the very equation that describes why a molecule of water (H2<\/sub>O) weighs less than two atoms of free hydrogen (H) and one atom of free oxygen (O); the difference in mass between the two is equivalent to the energy needed to \u201cbreak apart\u201d the water molecule into its three constituent atoms.<\/p>\n\n\n\n

The Breit-Wheeler Process<\/h2>\n\n\n\n

In principle, there are various special considerations and conditions that must be taken into account when playing around with this equation. However, demonstrations and examples, much like the water molecule example above, are out there; one of which is the Breit-Wheeler process<\/em>, described by physicists Gregory Breit and John A. Wheeler back in 1934. In it, they describe that two photons colliding into each other will create a pair of particles: an electron<\/em> and its antimatter equivalent, known as an antielectron<\/em> or positron<\/em>. The process conforms with Einstein\u2019s famous equation, thus making it the simplest way of transforming pure light into matter.<\/p>\n\n\n\n

The two physicists, however, did note that observing the process would be one of the most difficult to do in physics. For starters, the photons headed for a mutual crash must be high-energy gamma ray photons (the most energetic type of photon; you usually see this stuff during radioactive decay, or around quasars and black holes); scientists didn\u2019t have gamma ray lasers then, and they still don\u2019t have them now. This, among other hindrances, makes it difficult to demonstrate Einstein\u2019s equation at the simplest level; if you ask the physicists over at Brookhaven National Laboratory over in New York, however, they might have a workaround for it.<\/p>\n\n\n\n

The Experiment<\/h2>\n\n\n\n

Detailed in a paper published in the journal Physical Review Letters<\/em>, Brookhaven physicists set about to perform a workaround prescribed by Breit and Wheeler themselves all those years ago: instead of impacting two gamma ray photons, they instead impacted ions<\/em> accelerated at 99.995% the speed of light.<\/p>\n\n\n\n

Ions are atoms whose number of protons are unequal to the number of electrons, disrupting their usual neutral charge. Atoms, in essence, are electrically neutral\u2014that is, the number of positively-charged protons in their nucleus exactly matches the number of <\/em>negatively-charged electrons around them. Should it have one of its electrons taken away, the atom will find itself with more protons than electrons. As a result, the entire atom gains a net positive<\/em> charge\u2014a cation<\/em>. Should it get one more electron instead, there will be more electrons than protons, and the atom gains a net negative<\/em> charge\u2014an anion<\/em>.<\/p>\n\n\n\n

This time around, the physicists used gold cations, and proceeded to mash them together at the facility\u2019s Relativistic Heavy Ion Collider<\/em> (RHIC). As the positively-charged gold cations are accelerated, they produce their own magnetic field; this interacts with the RHIC\u2019s own electrical field, creating electromagnetic particles: photons. As Brookhaven physicist Zhangbu Xu put it: \u201c[…]When the ions are moving close to the speed of light, there are a bunch of photons surrounding the gold nucleus, traveling with it like a cloud.”<\/em><\/p>\n\n\n\n

<\/em>Thing is, the two gold cations don\u2019t necessarily hit<\/em> each other; they really just barely<\/em> miss each other, leaving their photon \u201cclouds\u201d to hit each other instead. These photon \u201ccloud\u201d collisions can be an obstacle; that\u2019s because instead of the usual photons, they instead produce \u201dvirtual\u201d photons\u2014photons that, simply put, just pop in and out of existence. Accelerating the gold cations to 99.995% the speed of light was a way to get around this; at relativistic<\/em> speeds (speeds close to the speed of light), these \u201cvirtual\u201d photons behave like their real counterparts.<\/p>\n\n\n\n

\"\"
An illustration of the phenomena taking place during the photon \u201ccloud\u201d collision of two gold cations traveling close to the speed of light. (Brookhaven National Laboratory, 2021) <\/figcaption><\/figure><\/div>\n\n\n\n

Now, the results from the Breit-Wheeler process differ when considering real-to-real, real-to-virtual, and virtual-to-virtual photon collisions. Physicists can identify which is happening from the angles <\/em>between the electron-positron pair generated by the collision. In the case of Brookhaven\u2019s recent study, the angles produced by their gold cation experiments remained consistent with those from real-to-real collisions. Brookhaven physicist Daniel Bradenburg also mentioned that they measured \u201call the energy, mass distributions, and quantum numbers of the systems,\u201d saying that \u201c[t]hey are consistent with theory calculations for what would happen with real photons.\u201d Said Bradenburg: “Our results provide clear evidence of direct, one-step creation of matter-antimatter pairs from collisions of light as originally predicted by Breit and Wheeler.”<\/em><\/p>\n\n\n\n

As it stands, scientists have yet to devise a way to directly detect real-to-real Breit-Wheeler process collisions; the scientists at Brookhaven National Laboratory, however, have made considerable progress in the pursuit, and show that science is, at the very least, going down the right path towards this ideal.<\/p>\n\n\n\n

Bibliography<\/h2>\n\n\n\n