Name: 无线电波如何帮助您清除通往太空的道路（How Radio Waves Could Help Clear the Way to Space）
Uploaded: 2021-04-18T13:14:31.000Z
Duration: 5 min 28 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

Space travel is likely going to be a big part of our future.

But as we send more instruments and people into Earth's orbit and beyond,

there's one problem we really need to deal with:

There is an invisible shell of radiation surrounding our planet that can wipe out satellites and

And we don't have a great solution for it.

But scientists are working on combating this radiation, with good old-fashioned radio waves.

We've known about this shell of radiation since 1958,

when NASA was sending  its very first spacecraft into orbit.

On the way up, cosmic ray detectors picked up a huge amount of radiation

In fact, it was so extreme, scientists initially thought they'd detected a Soviet nuclear test.

But soon they figured out that it was a natural phenomenon,

and that Earth was surrounded by two massive rings of radiation

between 650 and 60,000 kilometers above Earth's surface.

They're now called the Van Allen Belts, after the physicist James Van Allen, who discovered them.

And these donut-shaped rings are full of highly energetic charged particles that come from the Sun,

which is constantly releasing a stream of them in what's called the solar wind.

Most of these get deflected by our planet's magnetic field,

but some of them leak through and get trapped within it.

In particular, many of them get trapped in a region centered around Earth's magnetic equator,

where magnetic field lines are parallel to the surface,

so the particles bounce north and south,  but they can't escape.

Fortunately, we're pretty safe from all that here on Earth's surface,

but this radiation can pose serious problems  for our space tech.

Our satellites often have to pass through these belts,

and some, like GPS satellites, even orbit within them,

in the middle of a bunch of electrons traveling close to the speed of light.

If satellites were unprotected, these electrons would build up inside their components until they discharged,

a lot like a lightning strike, which could fry their electronics.

For now, engineers typically use metal casings to shield the sensitive components of satellites,

but that's extremely expensive, and it's still not foolproof, they could still get zapped in a solar storm.

Or, in a military context, something like a nuclear blast in the atmosphere

could make the radiation even stronger and knock out important satellites.

Which is another reason scientists  are studying all of this.

But it's not all about electronics, either.

This radiation makes sending people to space complicated, too.

It's not much of a problem right now, because our astronauts don't go up that high,

but back in the Apollo days, missions had to go through the thinnest parts of the belts

to try to limit astronauts' exposure to radiation.

And assuming human missions become more common in the future, this radiation will be a major concern.

So, to protect us, our future explorers, and our precious space tech,

scientists are actively looking for ways to clear these energetic electrons out of the Van Allen Belts,

in a process known as  radiation belt remediation.

And one of the most promising techniques yet uses a fairly low-tech approach: radio waves.

Back in 2015, a pair of spacecraft known as the Van Allen Probes

showed that human activity has actually helped protect us from the radiation in these belts.

See, ever since the 1950s, humans have been producing very low-frequency, or VLF, radio waves,

mostly for communication with submarines,

since these are the only frequencies  that can pass through water.

But there's something else that's special about these frequencies:

They resonate with the natural vibration of electrons trapped in the belts.

So when VLF waves come in contact with them,

they can give those electrons a little boost of energy and actually scatter them back into space!

That happens primarily during solar storms,

when the edge of the inner radiation belt  blows closer to Earth's surface.

During those times, measurements from the probes revealed that our VLF emissions on Earth

create a sort of protective bubble around the planet!

So that got scientists wondering if we could deliberately produce VLF waves

as a way to reduce the radiation even more.

There have even been some early experiments.

Like in 2008, a satellite measuring electrons in the inner radiation belt revealed that

one powerful radio antenna in Australia produced a measurable change in the belt.

But a similar antenna in Hawai'i had no effect.

Scientists think that's because the results depend on the local atmosphere and magnetic field,

which suggests that a better bet might be to put something in space.

So, as a test, a mission called the Demonstration and Science Experiment launched in June 2019.

Surprisingly boring name, but It has a massive, 80-meter-wide antenna to generate radio waves,

as well as six sensors to measure changes in the radiation field around it, which is not boring.

Right now, the spacecraft is in orbit more than 6,000 kilometers above Earth's surface,

and is practicing emitting its VLF waves.

Scientists are expecting the first results by the end of 2020.

And other researchers are looking into a more compact solution,

like an electron accelerator that would emit VLF waves and attempt to disperse electrons

It is a brand-new technology, since electron accelerators aren't something we normally throw up into space.

But scientists plan to launch this experiment in 2021.

So, it's likely we'll have to wait a little while longer to find out if these experiments are successful,

but either way, the results will help us learn more about the radiation around our planet

and how we can protect ourselves from it.

Thanks for watching this episode of SciShow Space!

And if you liked it, you might like our podcast, called SciShow Tangents!

We even have an episode all about the Apollo program, which is the one time in history

we've sent humans through these deadly belts of radiation.

We also have dozens of other episodes made by some of the same people who make SciShow,

and they're full of niche science, fun insights, and some friendly competition.

If you want to check it out, you can click on the link below,

or search for SciShow Tangents  wherever you listen to podcasts.

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无线电波如何帮助您清除通往太空的道路（How Radio Waves Could Help Clear the Way to Space）

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