Placeholder Image

字幕表 動画を再生する

  • When we hear the word radiation,

  • it's tempting to picture huge explosions and frightening mutations,

  • but that's not the full story.

  • Radiation also applies to rainbows

  • and a doctor examining an x-ray.

  • So what is radiation really,

  • and how much should we worry about its effects?

  • The answer begins with understanding that the word radiation

  • describes two very different scientific phenomena:

  • electromagnetic radiation

  • and nuclear radiation.

  • Electromagnetic radiation is pure energy

  • consisting of interacting electrical and magnetic waves

  • oscillating through space.

  • As these waves oscillate faster,

  • they scale up in energy.

  • At the lower end of the spectrum, there's radio,

  • infrared,

  • and visible light.

  • At the higher end are ultraviolet,

  • X-ray,

  • and gamma rays.

  • Modern society is shaped by sending and detecting electromagnetic radiation.

  • We might download an email to our phone via radio waves

  • to open an image of an X-ray print,

  • which we can see because our screen emits visible light.

  • Nuclear radiation, on the other hand,

  • originates in the atomic nucleus,

  • where protons repel each other due to their mutually positive charges.

  • A phenomenon known as the strong nuclear force

  • struggles to overcome this repulsion

  • and keep the nucleus intact.

  • However, some combinations of protons and neutrons,

  • known as isotopes,

  • remain unstable,

  • or radioactive.

  • They will randomly eject matter and/or energy,

  • known as nuclear radiation,

  • to achieve greater stability.

  • Nuclear radiation comes from natural sources, like radon,

  • a gas which seeps up from the ground.

  • We also refine naturally occurring radioactive ores

  • to fuel nuclear power plants.

  • Even bananas contain trace amounts of a radioactive potassium isotope.

  • So if we live in a world of radiation,

  • how can we escape its dangerous effects?

  • To start, not all radiation is hazardous.

  • Radiation becomes risky when it rips atoms' electrons away upon impact,

  • a process that can damage DNA.

  • This is known as ionizing radiation

  • because an atom that has lost or gained electrons is called an ion.

  • All nuclear radiation is ionizing,

  • while only the highest energy electromagnetic radiation is.

  • That includes gamma rays,

  • X-rays,

  • and the high-energy end of ultraviolet.

  • That's why as an extra precaution during X-rays,

  • doctors shield body parts they don't need to examine,

  • and why beach-goers use sunscreen.

  • In comparison, cell phones and microwaves operate at the lower end of the spectrum,

  • so there is no risk of ionizing radiation from their use.

  • The biggest health risk occurs when lots of ionizing radiation

  • hits us in a short time period,

  • also known as an acute exposure.

  • Acute exposures overwhelm the body's natural ability to repair the damage.

  • This can trigger cancers,

  • cellular dysfunction,

  • and potentially even death.

  • Fortunately, acute exposures are rare,

  • but we are exposed daily to lower levels of ionizing radiation

  • from both natural and man-made sources.

  • Scientists have a harder time quantifying these risks.

  • Your body often repairs damage from small amounts ionizing radiation,

  • and if it can't,

  • the results of damage may not manifest for a decade or more.

  • One way scientists compare ionizing radiation exposure

  • is a unit called the sievert.

  • An acute exposure to one sievert will probably cause nausea within hours,

  • and four sieverts could be fatal.

  • However, our normal daily exposures are far lower.

  • The average person receives 6.2 millisieverts of radiation

  • from all sources annually,

  • around a third due to radon.

  • At only five microsieverts each,

  • you'd need to get more than 1200 dental X-rays

  • to rack up your annual dosage.

  • And remember that banana?

  • If you could absorb all the banana's radiation,

  • you'd need around 170 a day to hit your annual dosage.

  • We live in a world of radiation.

  • However, much of that radiation is non-ionizing.

  • For the remainder that is ionizing,

  • our exposures are usually low,

  • and choices like getting your home tested for radon

  • and wearing sunscreen

  • can help reduce the associated health risks.

  • Marie Curie, one of the early radiation pioneers,

  • summed up the challenge as follows:

  • "Nothing in life is to be feared, it is only to be understood.

  • Now is the time to understand more, so that we may fear less."

When we hear the word radiation,

字幕と単語

ワンタップで英和辞典検索 単語をクリックすると、意味が表示されます

B2 中上級

TED-ED】放射線は危険?- マット・アンティコール (【TED-Ed】Is radiation dangerous? - Matt Anticole)

  • 3277 220
    黃于珍 に公開 2021 年 01 月 14 日
動画の中の単語