Physics
Experiment Shows Fundamental Nature of Extremely Small Things Isn’t Determined Until Measured, Confirming Quantum Mechanics Weirdness
Physicists at The Australian National University (ANU) have conducted an updated version of John Wheeler’s famous 1978 delayed-choice thought experiment, involving a particle which has the choice of acting like either a particle or a wave. The result is extremely weird by everyday standards, but it’s routine for people studying quantum mechanics.
Experiments done in the past couple of centuries have shown that, at really tiny scales, things behave as both waves and particles. Whether a photon or an electron behaves like a particle or a wave depends on whether it is observed or not, which is quite a puzzling fact. Over the past century, scientists have come up with a series of thought experiments, as well as real tests, in order to study and explain this peculiarity of quantum mechanics. One of the latest, which once again confirms this weird theory, was conducted at the ANU Research School of Physics and Engineering by a team lead by Associate Professor Andrew Truscott.
For the experiment, the researchers trapped a group of helium atoms into a weird, extremely cool state known as a Bose-Einstein condensate, and then ejected the atoms one by one until there was a single particle left. This was then dropped through a pair of laser beams forming a grating pattern which “splits” the particle, just like a prism or a solid grating splits a beam of light. After the atom passed through the first grating, a quantum random number generator would decide whether or not to turn on another grating which would recombine the paths.
Here’s where things get interesting. If the atom acted like a single particle, the first grating would simply make it choose one path or another, and it would subsequently be detected (as a single particle) on the other side of the setup. And that’s exactly what happens, if only the first grating is activated. However, researchers noticed that whenever the second grating was added, they detected an interference pattern as if the atom went down both paths and was now acting like a wave.
This is extremely weird, because, as I’ve mentioned, the second grating was only activated after the atom had gone through the first crossroads, at which point it should have already made the decision of whether it will act as a particle or as a wave. But, in fact, the researchers found that the atom still hasn’t made its decision until it reaches the second crossroads and is thus measured a second time. This flies in the face of what we know about cause and effect but tells us something important about the quantum world: measurement is everything! Before being observed, the atom really is both a particle and a wave at the same time, and only we measure it does it decide what we see it as. According to professor Truscott, “the atoms did not travel from A to B. It was only when they were measured at the end of the journey that their wave-like or particle-like behavior was brought into existence.” (Below is a great explanation by Looking Glass Universe of the delayed-choice quantum eraser experiment, a version of which was proposed in 1978 by John Wheeler. The ANU team was aiming to recreate this experiment, only using single atoms instead of photons.)
https://www.youtube.com/watch?v=MW-AemjSVGY
Now, of course, it’s tempting to think that since measurement plays such an important role in determining how things behave at the microscopic level, observers have a sort of privileged position in the grand scheme of things. This doesn’t mean, however, that there’s no such thing as objective reality. For one thing, the extremely bizarre phenomena we see at a quantum level don’t scale up – no object we can see acts as a wave (except, well, waves) and we are usually very good at predicting the behavior of things if we know the basic laws of physics. Experiments like this don’t show that the Universe is a single consciousness or that humans have the power to control reality – they just show that the quantum world is really weird. Nevertheless, we owe things like lasers, LEDs, and transistors to the fact that it works and, at least at some level, we understand it. Which is why this research, and its correct interpretation, is so important.
Physics
An interest They stepped on a rock and found something on Mars that had never been seen before
NASA’s curiosity has been looking into an interesting part of Mount Sharp for the past 10 months. It shows signs of a violent watery past, and chemical tests have shown that it contains many minerals, such as sulfates. The rover also broke open a rock by accident as it moved around. And inside it were crystals of pure sulfur.
On Mars, people had never seen pure sulfur before. Even though sulfates contain sulfur, there isn’t a clear link between how those molecules form and how the pure crystals form. Crystals of elemental sulfur can only form in a few different situations. And none of those were thought to happen in this area.
To find a field of stones made of pure sulfur is like finding an oasis in the middle of the desert, said Ashwin Vasavada, the project scientist for Curiosity at NASA’s Jet Propulsion Laboratory. “That thing shouldn’t be there, so we need to explain it.” It’s so exciting to find strange and unexpected things when exploring other planets.
The Gediz Vallis channel is the name of the area that Curiosity is exploring. A groove across Mount Sharp has been interesting for a long time, even before the rover started climbing it in 2014. From space, scientists could see that there were big piles of debris. But it wasn’t clear what caused them. Was it landslides or floodwaters from a long time ago that moved the stuff along the channel?
The answer has been found through curiosity. Some column A and some column B. Water-moved rocks are smoother and rounder. Sharp and angular are those that dry avalanches moved. There are both kinds of rocks in the mounds.
“This was not a quiet time on Mars,” said Becky Williams, a scientist from Tucson, Arizona, who works for the Planetary Science Institute and is the deputy principal investigator of Mastcam on Curiosity. “There was a lot of exciting stuff going on here.” We expect a number of different flows to happen down the channel, such as strong floods and flows with lots of rocks.
Curiosity is still looking into the Gediz Valley. When the ball rolls around and shows off its unique features, we can get very excited about the science being done here.
To figure out if there is life in other parts of the universe, we start with Earth, where there is life now. Finding another Earth is a good way to find aliens. We have found more than 5,000 exoplanets, but we haven’t found Earth’s twin yet. This could change soon, though. Here comes the PLATO mission from the European Space Agency (ESA).
What does PLATO stand for? It stands for PLAnetary Transits and Oscillations of stars. Its goal is very clear. It will look for nearby stars like the Sun that might have habitable worlds like Earth.
“One of the main goals is to find a way to compare Earth and the Sun.” The size of Earth is in the habitable zone of a star like the Sun. “We want to find it around a star that’s bright enough that we can really figure out how heavy it is and how big it is,” Dr. David Brown from the University of Warwick told IFLScience. “If you like, that’s our main goal.”
The telescope is not only an observatory for looking for planets, but it is also an observatory for collecting data on a huge number of stars. The mission team thinks that the fact that it can do both is a key part of why this telescope will be so important.
“You have two parts of the mission.” One is exoplanets, and the other is the stars. “From a scientific point of view, I think it’s pretty cool that these two parts are working together to make the best science we can,” Dr. Brown said.
One of the secondary goals is to make a list of all the planets that are Earth-like and all the star systems that are out there. One more goal is to find other solar systems that are like ours. Even though we don’t know for sure if our little part of the universe is truly unique, it does seem to be different from everything else.
Dr. Brown told IFLScience, “We have a bunch of other scientific goals.” “Really, how well do we know how planetary systems change and grow over time?” Planetary systems are something we’re trying to understand as a whole, not just one planet at a time.
PLATO is different in more ways than just the goals. It is not just one telescope. In fact, it’s made up of 26 different ones. Two of the cameras are fast, and the other 24 are normal cameras set up in groups of six with a small gap between them. This makes the telescope work better, has a wider field of view, and lets you quickly rule out false positives.
It can be hard to tell which of the things you find when you transit exoplanets are real and which ones are not. With the help of several telescopes, we were able to block out some of the mimics that we would have seen otherwise. “Plus, it looks pretty cool,” Dr. Brown said with excitement. “This big square with all of these telescopes pointing at you looks really cool!”
This week, Dr. Brown gave an update on PLATO at the National Astronomy Meeting at the University of Hull. The telescope is being put together and has recently passed important tests. There are no changes to the planned launch date for December 2026. An Ariane 6 rocket, the same kind that made its first launch last week, will take off from French Guiana.
Einstein’s theory of special relativity says that it is impossible to move faster than light in a vacuum.
Things that don’t have mass have to move at the speed of light. But things that do have mass can’t get close to 299,792,458 meters per second (983,571,056 feet per second) without using up all of their energy. Physicists and sci-fi authors have tried to get around this by using concepts like the warp drive. But it’s likely that these will be illegal because of those pesky physics laws. Traveling faster than light can cause paradoxes that break the rules of the universe.
You are not in a dark room, though, because there is something in this room right now that can slow down or stop light. It is possible for shadows to go faster than light, and they can even smash through it.
You might ask things like, “What the hell are you talking about?” Imagine that you have a flashlight that is strong enough to light up some of the moon. If you quickly move your finger across the front of the flashlight, the shadow it casts can move across the moon’s surface at speeds much faster than light.
If you wave a laser across the night sky, you can get the same kind of effect. Think of a huge dome that is, say, 100 light-years across and surrounds you. When this laser hits that dome 100 years from now, the points will fly across it at speeds much faster than light.
But these two examples are just tricks.
Astrophysicist Michio Kaku told Big Think, “There is no message, no net information, and no physical object that actually moves along this image. There is only the image of the beam as it races across the night sky.”
No, the laser point isn’t really moving. What you’re seeing are photons hitting the dome and then different photons hitting a different part of the dome 100 years later after you moved your laser.
The universe and physics stayed the same because nothing really moved faster than light, and no information was sent.
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