字幕列表 影片播放 列印英文字幕 [Sun] Flares to full! [Earth] SHIELDS UP!... HA! [Sun] FIRE EVERYTHING! [Earth] There's a crack in the shields!! WHAT DO WE DO?! Hey sunny dispositions, Trace with Julian for DNews. The Sun and the Earth are in a constant battle, thanks to the Sun's tendency to be an unfathomably large mass of incandescent gas... Yes, absolutely, it's a gigantic nuclear furnace where hydrogen is built into helium... At temperatures of millions of degrees! But as a result… the sun is constantly releasing highly energized particles blasted away from these nuclear reactions. Mostly these particles are protons and electrons with some alpha particles (the nuclei of helium), and heavier charged particles thrown in like the nuclei of magnesium, sulfur, iron, neon, carbon, and titanium among others. Sometimes, the sun gets excited and releases a mass of superheated, charged plasma -- called a coronal mass ejection or CME. We've talked about them before. They're crazy. And that's when the Earth's magnetosphere is really challenged. These CMEs can be strong enough to damage satellites, force airplanes to change course to avoid them, disrupt electronics on the ground, and force astronauts to stay in the shelter of the International Space Station. The main thing stopping those pungently radioactive, highly charged particles from hitting you and me on top of the head, is the Earth's trusty magnetic field… generated by the movement of iron through our mantle. The magnetosphere works like a shield, protecting us from harmful CMEs and other charged particles, but our shield system has a crack in it! That's right, new research from the GRAPES-3 muon telescope reads like a battle report from Star Trek. Trace's Log, Stardate: June 22, 2015. A plasma ejection from the sun struck the planet at 2.5 million kilometers per hour. The energetic collision caused a compression of the magnetosphere between 2 and 5.5 times the width of Earth itself… causing magnetic storms and radio blackouts all over the planet. We suspect the Romulans are involved. No we don't. Trace out. Okay, lemme 'splain. A muon telescope is a cosmic ray detector. It's designed to keep an eye on cosmic rays breaching the magnetosphere -- it's looking for cracks. And it found one. The magnetosphere is powerful, but not perfect. According to the data, published in Physical Review Letters, the GRAPES-3 spotted a 20 giga electron volt collision with the magnetosphere and then some leakage! A CRACK IN THE FIELD!!! REVERSE THE POLARIZATION! Sorry. For perspective, the Large Hadron Collider, the world's most powerful particle accelerator can hit a top energy of about 26 GeV when accelerating only few protons at a time. This solar assault lasted for 2 hours at 20 GeV and coronal mass ejections are filled with plasma stretching half the distance from Earth to the sun. Luckily for us down here under the shield, it deflected the burst of solar plasma… But CMEs aren't the only thing attacking Earth at any given moment -- there are also cosmic rays. To keep up the Star Trek references, the Sun is like… the Romulan Fleet, but cosmic rays are more like a few shuttlecraft or escape pods. They're from other galaxies, black holes and the like, and while they're few, they are also constantly trying to leak down to us… This is where the "crack" comes in. When the CME assaulted the magnetosphere at such high energy, our field deflected it. But while it did that, some low-energy cosmic radiation leaked through! At that point, the energy was likely absorbed by molecules in our atmosphere before it hit you or me. In fact, the muon detector doesn't directly detect cosmic rays or coronal mass ejections at all. Instead, it detects muons -- subatomic particles -- that are created when cosmic rays hit the molecules of air in our atmosphere! So GRAPES-3 detected this burst of activity (the crack) that normalized after the CME ended; shield integrity is nominal. Even though we're okay down here, astronauts on orbit are less so. People in space are bombarded with cosmic rays! Unlike some larger energetic particles of a CME, cosmic rays can penetrate the walls of the ISS (and the astronauts inside). There's even a name for when one flies through an astronaut's eyeball... It's called Cosmic Ray Visual Phenomena -- and the ray basically causes the rods and cones to activate, creating a sparkle or spot. Astronaut Don Pettit describes it like "dancing faeries." Of course, long term exposure to cosmic rays, like on a trip to Mars, could cause permanent damage to brain cells. Not good. Luckily for us, the mantle keeps turning under our feet, generating our magnetosphere shield, and keeping us safe from both CMEs and cosmic rays… and from brain damage. Mostly. Mostly. Worried about radiation messing with your brain? Find out how exactly this invisible thing affects your DNA here. What's your favorite Star Trek episode? Tell us in the comments and please make sure to subscribe for more DNews.