I came across this intriguing video of a banana being levitated in the air. This isn't the first time I've discussed this strange new technology of quantum levitation, but it's been a while. The last time I brought it up was back in November 2011, when talk show host and comedian Stephen Colbert levitated his ice cream flavor on his show.
These are hardly the most serious examples of how this technology could be used, but they are very cool ... reminding us that scientific discoveries are often leveraged in unexpected (and entertaining) ways. But if you look under the banana (so to speak), you'll find some very deep understanding of the science matter and electromagnetism:
Image Source: Tel Aviv University
Physicists like it when things crash together. Okay, not so much when they do so unexpectedly. Just like anyone else, physicists prefer to keep their cars out of the body shop.
But collisions of objects do provide excellent opportunities to use the tools of physics to pull out some of the oldest, most trusted tools in the physics toolbox.
The key to any sort of collision is that it follows the law of conservation of momentum. In most collisions, however, there is a loss of kinetic energy. These collisions are called inelastic collisions, and in the real world this represents most of the types of collisions that we run into. In some collisions, in fact, the objects collide and stick together, losing the maximum amount of kinetic energy possible. These are called perfectly inelastic collisions.
Some collisions, on the other hand, do not lose kinetic energy during the collision ... or, at least, they lose so little kinetic energy that we can treat them as if they didn't lose any. (Recall that in physics we often try to approximate systems with an idealized model if at all possible.) These types of collisions are called elastic collisions, and they are decent first-order approximations for Newton's cradles (as depicted above), billiard balls banging into each other, or bumper cars.
If a collision generates a lot of heat and sound, chances are that it is an inelastic collision, since the original kinetic energy is getting transformed into the vibrating molecules that make up the heat and sound. If you could measure each and every vibration caused by the collision and calculate the total energy, it would of course equal the total energy before the collision. But this is impractical and, fortunately, unnecessary, since conservation of momentum typically gives us a sufficient set of tools to understand what happens in the collision.
When you're dealing with a homework problem that has to do with two objects colliding, a good question to ask oneself is: What type of collision is this? That'll help set you on the road to figuring out which equations you can apply to the situation and how to solve the problem.
Image Source: Tyler Boley/Getty Images
One of the deepest questions in physics is the attempt to provide an answer to the seemingly simple questions: Does time really exist?
Though we all experience time moving in one direction (the "arrow of time" as it is called), the curious thing about the laws of physics don't actually require this. If you tried to apply the equations with time moving the opposite direction, they would actually still make sense. Why, then, do we experience such an unrelenting forward motion in time?
The standard explanation revolves around the concept of entropy. As well explained in Sean Carroll's 2010 book From Eternity to Here: The Quest for the Ultimate Theory of Time, the solution that is most commonly accepted these days is that the arrow of time is an artifact of the initial conditions of the universe. Because the early universe was highly ordered, time moves in the direction of increasing entropy.
This answer doesn't cut it for controversial theoretical physicist Lee Smolin. In the new book Time Reborn: From the Crisis in Physics to the Future of the Universe, Smolin confronts the idea that time is "unreal" and argues instead for treating time as a fundamentally real quantity. His conclusion is that our entire approach to theoretical physics may need to be rethought. Instead of looking for eternal and timeless laws of physics, Smolin believes that we should instead look for laws of physics that themselves evolve throughout time.
It's an intriguing proposal and, if adopted, would certainly revolutionize the approach to physics. This is nothing new to Smolin, who is nothing if not an unconventional thinker. I go into some of the reasoning behind Smolin's approach in the review of the book.
What do you think? Is time real? Does physics adequately address questions about the nature of time?
If you've been paying any attention at all to astrophysics or cosmology over the last couple of decades, you'll be aware that one of the major mysteries science has been exploring is the composition of matter in the universe.
NASA's WMAP program had given us a great vision of the universe, indicating that only about 5% of our universe is made up of stuff that we actually observe and mostly understand (called "visible matter" ... since we see it all around us and also in space). Another 23% is what's called dark matter, a type of matter that we cannot see and do not fully understand, but which appears to be out there if we're to explain the behavior of many stars and galaxy movements. And then there's the last 72%, which is an amazing substance which we only barely understand called dark energy, which actually seems to be pushing space itself apart, causing an increase in the expansion rate of the universe ... first observed in 1998 and the discovery of which earned the 2011 Nobel Prize in Physics.
For a while, I had been reporting nearly-monthly on various discoveries and reports on this front ... but this is such a cutting edge of research that science writers had a tendency to jump on every single inkling with overblown headlines about the importance of new discoveries. One thing that I really try to avoid on here is to indulge in this sort of unjustified hyperbole, staying focused on reporting science that's well established. It's not that I oppose speculation in science, but I just want to try to be very clear on when the speculation is happening, and a monthly report that was mostly speculation -- and often speculation that didn't pan out -- became stale to me.
That having been said, it's been long enough since I focused on them that there have been a few discoveries (or potential discoveries), mostly from Europe's Planck observatory, and I feel they're worth commenting on ... so here's a new update on the dark stuff that we think makes up our universe.
Updated Numbers for Dark Matter and Energy
The basis for dark matter is the fact that some galaxies and other astronomical objects are moving in a way that indicates there's probably more matter in those galaxies than we can see. The simplest resolution for this is the explanation that there's a type of matter we aren't able to see ... and this is dark matter.
As I mentioned above, the WMAP estimated that about 23% of the universe was composed of dark matter, but the new data from the Planck observatory has pushed that estimate up to about 27% of the universe! The numbers for dark energy is about 68.3%, with ordinary visible matter still coming in a touch under 5%.
Dark Matter Search Continues
The search for dark matter particles is still going strong, and there's even been a hint of evidence - in the form of some extra anti-matter - showing up in the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. Additional research is still looking for evidence of dark matter here on Earth, such as the research taking place at Minnesota's Cryogenic Dark Matter Search (CDMS) lab, looking for Weakly Interacting Massive Particles (WIMPs), which may also explain the AMS detector results.
Alternative Gravity Theories
As I mentioned above, dark matter is predicted because more matter is needed to make the equations of gravity match the motion we observe in the universe. Another explanation is that perhaps our methods of calculating the gravitational influence of matter is somehow flawed. One alternative gravity proposal designed around this idea is Modified Newtonian Dynamics (MOND), and it's recently gotten a bit of press as well, since MOND-based predictions have had some success in areas where dark matter proposals just can't make predictions. The physicist behind this research, Stacy McGaugh, explains it:
The predictive power of MOND in these systems stands in stark contrast to the dark matter paradigm, which makes no comparably clear prediction.[...] At the very least, this unexpected situation is a reminder that there is still plenty we don't understand about the vast cosmos in which we reside.
New Dark Flow Losing Steam?
In addition to dark energy and dark matter, in 2008 research came out that seemed to indicate something that became known as "dark flow" ... a region of space that was accelerating and moving in a way that not consistent with the surrounding regions of space. This bizarre behavior was discussed in some detail in Paul Halpern's recent book The Edge of the Universe.
Unfortunately for those of us who are always looking for new mysteries of the universe, some newer research, based on data taken from the Planck satellite, is making scientists think that dark flow is probably not real. However, there is some suggestion that the researchers who published the paper overestimated the uncertainty in their measurements, which would mean that there's very real data which is being ignored because it looks like statistical noise. The original researchers are doing their own analysis of the data and will no doubt announce as soon as they can whether or not they feel the Planck data is consistent with their earlier observations.
Image source: NASA/WMAP Team