VOA标准英语2011--NASA's GRAIL to Map the Moon

NASA's GRAIL to Map the Moon The U.S. space agency NASA is preparing to launch a new, nearly half-billion dollar lunar mission that will enable scientists to better understand the moon's gravitational field and the lunar interior, from crust to core.

英语听力：自然百科 地球力场 Earth's Force Field—2

Radiation causes damage at the most fundamental level. It mutates the blueprint of life, DNA. Earth's magnetosphere is our crucial defense. It's so fundamental to our evolution and continued existence that the race is on to understand why it's changi

英语听力：自然百科 地球力场 Earth's Force Field—18

Earth's magnetic field has reversed thousands of times since its formation 4.5 billion years ago. And scientists now believe that the next reversal is imminent. The race is on to predicting exactly when it will occur. In 2010, the European Space Agen

英语听力：自然百科 地球力场 Earth's Force Field—16

During its magnetic cycle, the Sun undergoes periodic changes in activity. Every 11 years, it enters solar maximum. This 11 years cycle of solar activity has peaks where theres lots of solar storms. And right now where the sun is taking a little napp

英语听力：自然百科 地球力场 Earth's Force Field—12

Six years later, they come to believe these light flashes are the results of high energy, heavy cosmic rays penetrating the spacecraft and the crew members' eyes. These/ protons or electrons, just very, very high energy, ripped / part of atoms, sprin

英语听力：自然百科 地球力场 Earth's Force Field—13

Glatsmire's model shows that the magnetic poles swap places spontaneously due to / complex processes within the core. We were used to the idea that a compass points somewhere near the North Pole and hence we can use it for navigation, but there are p

英语听力：自然百科 地球力场 Earth's Force Field—15

By analyzing thousands of lava samples, geophysicists discover/ that the Earth's magnetic field has reversed over 18,000 times in the last 20 million years. On either side of these reversals is a long period of dramatically reduced field strength. Du

英语听力：自然百科 地球力场 Earth's Force Field—17

We drive them about 20 miles away to the North, and release them, and we track them as they try to fly back home. We drive them about 20 miles away to the North, and release them, and we track them as they try to fly back home. Hes up, OK. Holland wa

英语听力：自然百科 地球力场 Earth's Force Field—14

By analyzing different samples of lava, Herrero / Bervera has built up a picture of how the filed has changed since long before humans were around. They are actually the recorders of the Earth's magnetic field in hundreds of years, thousands of years

英语听力：自然百科 地球力场 Earth's Force Field—5

If we could flip a switch and just turn off the Earth's magnetic field, it will take about 15,000 years to disappear, based on the rate of decay of the field that we've seen over the last 150 years. It's currently decaying at a rate that would see an

英语听力：自然百科 地球力场 Earth's Force Field—3

In polar regions where the magnetic field is / weakest, auroras glow in the sky. These dazzling displays of colored lights form when solar particles slam into gases in our atmosphere causing them to glow. The stronger the solar wind, the more dramati

英语听力：自然百科 地球力场 Earth's Force Field—4

Scientists believe that the South Atlantic Anomaly, is a sign of a global decline in the magnetic field. Evidence of this comes from a surprising source. Dr. Mimi Hill uses pottery to uncover the secrets of earth's magnetic past. Ancient pots tell us

英语听力：自然百科 地球力场 Earth's Force Field—7

The loss of the magnetic field has a catastrophic impact on the planet's evolution. Mars becomes the red planet we see today. If earths magnetic protection continues to fade, would it suffer the same fate? If it vanishes completely, the planet might

英语听力：自然百科 地球力场 Earth's Force Field—8

Easily confused by this idea, there has a big thawed iron inner core, so that I think it's just the bar magnet, just permanent magnet frozen in nad, and that's where causes all the magnetic field. But it's too hot inside the Earth, that can't happen

英语听力：自然百科 地球力场 Earth's Force Field—9

As the vast sphere reaches / maximum speed, something incredible happens. Huge lines of magnetism arc in and out of the model core. Well, we can't see the magnetic field coming out of the experiment, we can measure them, we can put many different mag

英语听力：自然百科 地球力场 Earth's Force Field—10

Larry Newitt from the Geological Survey of Canada charts the movement of the magnetic North Pole as it wanders the icy reaches of northern Canada. To determine where the magnetic pole / is, we can't rely on one single observation. What I try to do is

英语听力：自然百科 地球力场 Earth's Force Field—11

Blockson's computer model reveals that at the South Atlantic Anomaly, the magnetic field isn't just weaker than anywhere else on the planet. It's actually reversed polarity. There is a patch on the core in the South Atlantic where things are not poin

英语听力：2013-09-22 地平线：黑洞吞噬—2

High above your head, in the centre of our Milky Way Galaxy, a violent drama is about to unfold. Our super-massive black hole is getting ready to have dinner. As a gas cloud three times the size of the Earth, its caught in its gravitational hold. Acr

万物简史 第77期:事物的测定(25)

When assembled, Michell's apparatus looked like nothing so much as an eighteenth-century version of a Nautilus weight-training machine. It incorporated weights, counterweights, pendulums, shafts, and torsion wires. 装配完毕以后，米歇尔的仪器

留美老师带你每日说英文 第906期:大气压力和高度的关系

As altitude increases, atmospheric pressure decreases. This is due to Earth's gravitational pull on the air molecules in the atmosphere. The closer to the Earth's surface the stronger the force exerted on these molecules. 随着高度上升，大气压