If quantum physics states matter doesn't exist when it's not being noticed, then, without life, would the universe cease to exist? originally appeared on Quora: the place to gain and share knowledge, empowering people to learn from others and better understand the world.

Answer by Viktor T. Toth, IT pro, part-time physicist, on Quora:

If quantum physics states matter doesn't exist when it's not being noticed, then, without life, would the universe cease to exist?

This question demonstrates the dangers of trying to comprehend modern physics from popularizations.

It is absolutely not true that states of matter do not exist when they are not noticed. If someone tells you this, he is talking nonsense.

The correct statement is that a quantum system usually exists in a state that is not at all like the states of the classical world. Simply put, it cannot be described by ordinary numbers.

This is in contrast with classical objects, which can be described with ordinary numbers. That is to say, their position, their velocity, and other physical properties can be described using simple numerical values.

Now it is true that there is no such thing as a truly classical object: that even people, cats, cannonballs or planets are made of a large number of quantum particles. However, in these systems, all the quantum behavior is averaged out, so to speak, so their behavior is indistinguishable from that of classical systems.

Every once in a while, some properties of a quantum system may be describable by ordinary numbers. When a quantum system is (briefly) in such a classical state, it is said to be in an eigenstate (“eigen” means “own” in German); the value of the property would be the corresponding “eigenvalue”.

This is precisely what happens when a quantum system interacts with a classical system; i.e., when we “measure” something. During the interaction, the quantum system is confined to an eigenstate.

Let me explain this through a common thought experiment: the infamous two-slit experiment. The experiment involves an electron gun that emits electrons which can go through one of two slits before impacting a screen. We find that an interference pattern emerges on the screen; this is true even when we fire the electrons one at a time. You may have heard that this means that every single electron goes through both slits. True, but there is a better way to understand this. When the electron finally arrives at the screen, the screen (a classical object) measures the electron’s position: the electron is now in a “position eigenstate”. En route, however, the electron is not in a position eigenstate. It does not have a position in the classical sense at all. So yes, it goes through both slits and does many other things that classical objects just cannot do (and it is wrong even to try to visualize the electron when it is in this quantum state). But it does not mean the electron’s existence is conditional. It exists all along… its position is just not describable by ordinary numbers. Nor is there any need for consciousness to be involved. The fluorescent screen has no consciousness at all, but it does confine the electron to an eigenstate because it itself is a classical object (or so close to being classical as to be indistinguishable from it).

So no, the existence of the universe does not depend on the presence of life. And many things in this universe are in eigenstates every once in a while simply because of the way they interact with other things which are, for all practical intents and purposes, classical.

This question originally appeared on Quora - the place to gain and share knowledge, empowering people to learn from others and better understand the world.

For over 11 decades we have known that matter and energy are interchangeable. The development of nuclear power has shown us that matter can be converted into energy, but converting energy into matter has so far proven a lot more difficult.

The battlefield for such an achievement is at the end of the most powerful lasers ever envisioned. Currently being planned and built in a number of different countries. Three projects top the “one to watch list” of the laser world, prepared by the journal Science. They are China’s Station of Extreme Light (SEL), Russia’s Exawatt Center for Extreme Light Studies (XCELS), and the Department of Energy’s Optical Parametric Amplifier Line (OPAL).

These three lasers are planned to completely annihilate the current record for laser power, which is 5.3 million billion watts or 5.3 petawatts (PW) and obtained by Ruxin Li and colleagues at the Shanghai Superintense Ultrafast Laser Facility (SULF). Li is also behind SEL and hopes that by 2023 his team could reach the goal of a 100-PW laser.

The Russian instrument is still in the design phase of development but is more daring in its target. The researchers hope it will achieve 180 PW. Both SEL and XCELS are expected to work on the same principle. They shoot a series of pulses (four 30-PW pulses for SEL and a dozen 15-PW pulses for XCELS) and combine them into a single extra-powerful one.

Science Magreports that this approach requires extreme precision and even the smallest vibration or temperature variation can compromise the achievements of such a powerful laser pulse. For this reason, OPAL is going a different way. It is envisioned to reach 75 PW with a single pulse.

There are other facilities working on “more modest” equipment that will aim to deliver 30-PW machines and SULF itself hopes to break the 10-PW record this year. High-energy is required but it is not the only necessity to “break the vacuum” and turn photons into electrons and positrons, their antimatter counterparts.

The way that SEL is expected to do this is very interesting. The laser will hit a helium target and liberate electrons. Some of the photons from the beam will ricochet off the electrons and then collide with other photons, creating particle-antiparticle pairs.

If SEL can truly break the vacuum, it could change the way we approach particle physics. Traditional particle accelerators might be swapped for faster and cheaper laser-powered ones.

[H/T: Science Mag]

For over 11 decades we have known that matter and energy are interchangeable. The development of nuclear power has shown us that matter can be converted into energy, but converting energy into matter has so far proven a lot more difficult. The battlefield for such an achievement is at the end of the most powerful lasers ever envisioned, currently being planned and built in a number of different countries.

Three projects top the “one to watch list” of the laser world, prepared by the journal Science. They are China’s Station of Extreme Light (SEL), Russia’s Exawatt Center for Extreme Light Studies (XCELS), and the Department of Energy’s Optical Parametric Amplifier Line (OPAL).

These three lasers are planned to completely annihilate the current record for laser power, which is 5.3 million billion watts or 5.3 petawatts (PW) and obtained by Ruxin Li and colleagues at the Shanghai Superintense Ultrafast Laser Facility (SULF). Li is also behind SEL and hopes that by 2023 his team could reach the goal of a 100-PW laser.

The Russian instrument is still in the design phase of development but is more daring in its target. The researchers hope it will achieve 180 PW. Both SEL and XCELS are expected to work on the same principle. They shoot a series of pulses (four 30-PW pulses for SEL and a dozen 15-PW pulses for XCELS) and combine them into a single extra-powerful one.

Science Mag reports that this approach requires extreme precision and even the smallest vibration or temperature variation can compromise the achievements of such a powerful laser pulse. For this reason, OPAL is going a different way. It is envisioned to reach 75 PW with a single pulse.

There are other facilities working on “more modest” equipment that will aim to deliver 30-PW machines and SULF itself hopes to break the 10-PW record this year. High-energy is required but it is not the only necessity to “break the vacuum” and turn photons into electrons and positrons, their antimatter counterparts.

The way that SEL is expected to do this is very interesting. The laser will hit a helium target and liberate electrons. Some of the photons from the beam will ricochet off the electrons and then collide with other photons, creating particle-antiparticle pairs.

If SEL can truly break the vacuum, it could change the way we approach particle physics. Traditional particle accelerators might be swapped for faster and cheaper laser-powered ones.

Black holes don't just sit there munching away constantly on the space around them. Eventually they run out of nearby matter and go quiet, laying in wait until a stray bit of gas passes by.

Then a black hole devours again, belching out a giant jet of particles. And now scientists have captured one doing so not once, but twice - the first time this has been observed.

The two burps, occurring within the span of 100,000 years, confirm that supermassive black holes go through cycles of hibernation and activity.

It's actually not as animalistic as all that, since black holes aren't living or sentient, but it's a decent-enough metaphor for the way black holes devour material, drawing it in with their tremendous gravity.

But even though we're used to think how nothing ever comes back out of a black hole, the curious thing is that they don't retain everything they capture.

When they consume matter such as gas or stars, they also generate a powerful outflow of high-energy particles from close to the event horizon, but not beyond the point of no return.

"Black holes are voracious eaters, but it also turns out they don't have very good table manners," said lead researcher Julie Comerford, an astronomer at the University of Colorado Boulder.

"We know a lot of examples of black holes with single burps emanating out, but we discovered a galaxy with a supermassive black hole that has not one but two burps."

The black hole in question is the supermassive beast at the centre of a galaxy called SDSS J1354+1327 or just J1354 for short. It's about 800 light-years from Earth, and it showed up in Chandra data as a very bright point of X-ray emission - bright enough to be millions or even billions of times more massive than our Sun.

The team of researchers compared X-ray data from the Chandra X-ray observatory to visible-light images from the Hubble Space Telescope, and found that the black hole is surrounded by a thick cloud of dust and gas.

"We are seeing this object feast, burp, and nap, and then feast and burp once again, which theory had predicted," Comerford said. "Fortunately, we happened to observe this galaxy at a time when we could clearly see evidence for both events."

That evidence consists of two bubbles in the gas - one above and one below the black hole, expulsions particles following a meal. And they were able to gauge that the two bubbles had occurred at different times.

The southern bubble had expanded 30,000 light-years from the galactic center, while the northern bubble had expanded just 3,000 light-years from the galactic center. These are known as Fermi bubbles, and they are usually seen after a black hole feeding event.

From the movement speed of these bubbles, the team was able to work out they occurred roughly 100,000 years apart.

So what's the black hole eating that's giving it such epic indigestion?

Another galaxy. A companion galaxy is connected to J1354 by streams of stars and gas, due to a collision between the two. It is clumps of material from this second galaxy that swirled towards the black hole and got eaten up.

"This galaxy really caught us off guard," said doctoral student Rebecca Nevin.

"We were able to show that the gas from the northern part of the galaxy was consistent with an advancing edge of a shock wave, and the gas from the south was consistent with an older outflow from the black hole."

The Milky Way also has Fermi bubbles following a feeding event by Sagittarius A*, the black hole in its center. And, just as J1354's black hole fed, slept, then fed again, astronomers believe Sagittarius A* will wake to feed again too.

The research was presented at the 231st meeting of the American Astronomical Society, and has also been published in The Astrophysical Journal.



This article was originally posted on ScienceAlert. Click here to read it.

A group of researchers has discovered proof for a strange particle that, strangely, is also its own antiparticle. It was first proposed 80 years ago but now existence of it might be a reality.

The results, published in the journal Science, were led by researchers from Stanford University in California and the University of California.

The notion of a particle having its own antiparticle was first introduced in 1937 when Italian physicist Ettore Majorana (who strangelydisappeared in 1938) first suggested the theory.

He said that inside the class of fermions, which comprise protons, electrons, and neutrons, some particles must have their own antiparticles, which became known as Majorana particles.

An antiparticle is a particle that has the same mass as the normal particle, but a reverse electric or magnetic property. For instance, the electron’s antiparticle is the positron. If the two come across each other, they annihilate each other.

In this study, the group of physicists stacked thin films of two quantum materials together and directed an electrical current through them in a chilled vacuum chamber. The top film was a superconductor, and the bottom one was a magnetic topological insulator.

By sweeping a magnet over the stack, the team was then able to adjust the speed of electrons. At certain points, this triggered what seemed to be Majorana quasiparticles to appear in pairs alongside with electrons. One was always bounced away so that the flow of the individual quasiparticles could be measured.

The particular kind of Majorana quasiparticle they think they’ve found is called a “chiral” fermion, which moves along a one-dimensional path in one direction.

So the scientists are denoting to this as “smoking gun” indication of Majorana particles. It was already believed that neutrinos might be their own antiparticles, though separate research is ongoing to find out if that’s the case.

Stanford professor Shoucheng Zhan, a senior author on the paper, said:

“Our team predicted exactly where to find the Majorana fermion and what to look for as it's ‘smoking gun’ experimental signature. This discovery concludes one of the most intensive searches in fundamental physics, which spanned exactly 80 years.”