Physics news

[lswot]

For what? A free lube and oil ?

[Henry J]

And some new sprockets. Don't forget the sprockets!

[lswot]

Oh, yeah......the best part!

[Henry J]

Solar eclipse Sunday afternoon!

[lswot]

made any plans?

[Henry J]

The Shadow knows!

[lswot]

Very good!

[brian]

In this series of slow motion clips, you can see that if you hold a Slinky by one end and drop it, the bottom end doesn't actually move until the top end catches up with it.


http://www.youtube.com/watch?v=uiyMuHuCFo4

I've watched this like six times and it drops my jaw every time...the bottom of the Slinky JUST. DOES. NOT. MOVE. Here's the scientific explanation:

The explanation that "it takes time for the bottom of the slinky to feel the change" might work ok, but it isn't the best.

Then why doesn't the bottom of the slinky fall as the top is let go? I think the best thing is to think of the slinky as a system. When it is let get, the center of mass certainly accelerates downward (like any falling object). However, at the same time, the slinky (spring) is compressing to its relaxed length. This means that top and bottom are accelerating towards the center of mass of the slinky at the same time the center of mass is accelerating downward.

[Henry J]

IOW, the bottom of the spring has competing forces acting on it - tension vs. gravity. While they happen to balance each other out, it doesn't move.

[lswot]

Uhhh, what came first the chicken or the egg?

[Henry J]

Which came first - sunrise, or sunset?

Summer, or winter?

Low tide, or high tide?

Abbott, or Costello?



Henry

[lswot]

Exactly!

[Henry J]

Thought so!

[lswot]

[brian]

Is The Hunt For The 'God Particle' Finally Over?

Before we get to the fireworks on the Fourth of July, we might see some pyrotechnics from a giant physics experiment near Geneva, Switzerland.

Scientists there are planning to gather that morning to hear the latest about the decades-long search for a sub-atomic particle that could help explain why objects in our universe actually weigh anything.

The buzz is that they're closing in on the elusive Higgs particle. That would be a major milestone in our quest to understand the most basic nature of our universe.

King Arthur had his quest for the Holy Grail. Physicists hope they are hot on the trail of the Higgs particle. You might call it the final puzzle piece, needed to complete our picture of how all the fundamental particles make up the universe.

Joe Lykken at the Fermi National Accelerator Laboratory in Illinois has been part of this quest since the early 1980s.

"Our former director, Leon Lederman, called the Higgs particle the God Particle," Lykken says. "It was not meant to be a religious comment, it was meant to express our understanding of how the universe works. We think without a Higgs boson you can't have a universe in the first place."

At the very least, the universe would be incredibly boring. That's because the Higgs particle, or Higgs boson, is supposed to explain why the atoms in the galaxies, the stars, the earth at our feet, and in our bodies, have mass. If they didn't have mass, we wouldn't exist as physical beings.

"We think the Higgs boson is a manifestation of the fact that the universe is filled with a force that we haven't been able to detect yet, that gives other particles mass," Lykken says.

It's weird to think that particles only become massive by interacting with some invisible field. After all, we think of mass as the inherent property of an object. But that's what the so-called standard model of our universe predicts.

We may never be able to detect that mass field directly. But as you may recall from high school science, fields also come with matching particles. Electromagnetic fields, including visible light, are also manifest as abundant photon particles.

We don't see the Higgs particle because it's incredibly unstable, "so it exists for a billionth of a billionth of a billionth of a second, or something like that, and then falls apart into other particles," Lykken says.

This brings us, at last, to that physics experiment on the Swiss-French border. The Large Hadron Collider has been banging together atomic particles at super-high energies in an attempt to produce a few Higgs particles. And scientists have been sifting through the resulting debris to see if they can find signs that Higgs particles appeared and then quickly broke apart.

Last December, the scientists there said they were seeing tantalizing hints. Now, they have a new pile of data. They are hoping to be able to say something more definitive.

"This is really the most exciting year in my career," says Matt Strassler, a theorist at Rutgers University. "And the reason it's so exciting is this is one of those very, very rare circumstances that first of all, we know there's something to look for and we know, whatever the answer is whether it is there or not it's going to be very interesting and exciting."

Thousands of physicists are waiting for the "aha!" moment, whenever that might be. Drew Baden at the University of Maryland says, on one level, the discovery is expected, since it has been predicted for so long. But he says the physics world is like Christopher Columbus, who sailed off to the west, confident that he would eventually find the ocean's opposite shore.

"It's all theory, right? Because no-one's done it," Baden says. "And then [Columbus and his men] get in their ships, and they actually make it. This is really deep."

Columbus took an abstract and unproven idea and proved it was true. Baden says that's exactly where the experiments in Switzerland are heading. They are turning squiggly formulas into actual physical things.

It's still a bit premature to declare success, "but it really looks good, people are starting to be convinced that maybe this is the new world that we're seeing," Baden says.

Finding the Higgs particle isn't like finding a speck of dirt. Nobody will ever see it directly. Scientists need to plow through huge amounts of data to be sure that the anomaly they are seeing represents an actual particle, not just fluky coincidences.

But the way things look now, sometime this year physicists will probably see enough evidence in that spray of sub-atomic particles to declare that they've finally found the Higgs boson.


This image, from a sensor at the particle accelerator at
CERN, is an example of the data signature a Higgs particle
might generate.