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  • How much can we really know about the universe beyond our galaxy?

  • The Hubble Telescope has enabled us to see objects in space as far 13,000,000,000 light years away.

  • But this still doesn't give us the answers to all our questions,

  • questions like, "What is the universe made of?"

  • "Which elements are the most abundant?"

  • "Does space contain undiscovered forms of matter?"

  • "Could there be antimatter stars or galaxies?"

  • Some of these questions cannot be answered solely from visual images,

  • but what if we had messengers bringing us physical data from distant parts of the cosmos,

  • beyond the reach of explorers or satellites?

  • In a way, we do, and these "space messengers" are called cosmic rays.

  • Cosmic rays were first discovered in 1912 by Victor Hess

  • when he set out to explore variations in the atmosphere's level of radiation,

  • which had been thought to emanate from the Earth's crust.

  • By taking measurements on board a flying balloon during an eclipse,

  • Hess demonstrated both that the radiation actually increased at greater altitudes

  • and that the sun could not be its source.

  • The startling conclusion was that it wasn't coming from anywhere

  • within the Earth's atmosphere but from outer space.

  • Our universe is composed of many astronomical objects.

  • BIllions of stars of all sizes, black holes, active galactic nuclei,

  • asteroids, planets and more.

  • During violent disturbances, such as a large star exploding into a supernova,

  • billions of particles are emitted into space.

  • Although they are called rays,

  • cosmic rays consist of these high energy particles

  • rather than the photons that make up light rays.

  • While the light from an explosion travels in a straight line at its famous constant speed,

  • the particles are trapped in extraordinary loops

  • by magnetic shock waves generated by the explosion.

  • Crossing back and forth through these magnetic field lines accelerates them to almost the speed of light before they escape.

  • There are lots of cosmic rays in space, and some of these particles have traveled for billions of years before reaching Earth.

  • When they enter our atmosphere, they collide with the molecules there,

  • generating secondary cosmic rays,

  • lighter particles with less energy than the original.

  • Most of these are absorbed into the atmosphere,

  • but some are able to reach the ground, even passing through our bodies.

  • At sea level, this radiation is fairly low.

  • But people who spend a lot of time at higher altitudes,

  • such as airline crews, are exposed to much more.

  • What makes cosmic rays useful as messengers

  • is that they carry the traces of their origins.

  • By studying the frequency with which different particles occur,

  • scientists are able to determine the relative abundance of elements,

  • such as hydrogen and helium, within the universe.

  • But cosmic rays may provide even more fascinating information about the fabric of the universe itself.

  • An experiment called the Alpha Magnetic Spectrometer, A.M.S.,

  • has recently been installed on board the International Space Station,

  • containing several detectors that can separately measure a cosmic ray particle's velocity, trajectory, radiation, mass and energy,

  • as well as whether the particle is matter or antimatter.

  • While the two are normally indistinguishable,

  • their opposite charges enable them to be detected with the help of a magnet.

  • The Alpha Magnetic Spectrometer is currently measuring 50 million particles per day

  • with information about each particle being sent in real time from the space station to the A.M.S. control room at CERN.

  • Over the upcoming months and years,

  • it's expected to yield both amazing and useful information about antimatter,

  • the possible existence of dark matter,

  • and even possible ways to mitigate the effects of cosmic radiation on space travel.

  • As we stay tuned for new discoveries, look to the sky on a clear night,

  • and you may see the International Space Station,

  • where the Alpha Magnetic Spectrometer receives the tiny messengers that carry cosmic secrets.

How much can we really know about the universe beyond our galaxy?

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B2 US TED-Ed cosmic space magnetic radiation universe

【TED-Ed】How cosmic rays help us understand the universe - Veronica Bindi

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    稲葉白兎 posted on 2016/04/14
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