## Subtitles section Play video

• Nuclear waste. We've got a lot of it, it'll stay dangerous for tens of thousands of years,

• and we don't really know what to do with it. So why don't we just send it into space and

• crash it into the sun?

• Well, first, it's really dangerous to put nuclear waste on a rocket, since rockets have

• a tendency to occasionally explode while launching, making any nuclear-waste-filled exploding

• rocket into a really big dirty bomb.

• But the bigger reason is that it's actually really really hard to *get* to the sun. It

• might seem like it should be easy, since the sun's gravity is always pulling us towards

• it. But we're also orbiting really fast sideways around the sun, so that as we fall towards

• it, we miss it.

• In order to crash _into_ the sun, you have to slow down so that you're _not_ going sideways

• really fast. The earth - and everything on it - is moving around the sun at around 30

• kilometers per second, so you'd have to accelerate to a speed of 30kilometers per second backwards

• away from the earth in order to stop moving around the sun and do a sun dive. And you

• have to slow down all the waywith even a little bit of sideways speed, you'll miss

• the sun and whip around, not crashing.

• Ok, so a speed of 30 kilometers per second is really fast, but just how fast? Well, from

• earths's orbit, you only need to be going _11_ kilometers per second faster than the

• earth in order to escape from the entire solar system. Which means that it's much, much harder

• to crash into the sun than to escape it altogether. Let me say that again: it takes less acceleration

• to get to _other_ stars than it does to get to our own sun. Crazy.

• But it gets weirder: because the gravity from an object is stronger the closer you are to

• it, the smaller your orbit is, the faster your orbital speed. For example, Mercury goes

• around the sun at a speed one and a half times faster than earth, while Pluto goes only a

• sixth as fast. And that means it's actually way harder to crash into the sun from Mercury

• than from the earth, even though you're closer, because you'd have to accelerate to a speed

• of 48 kilometers per second backwards instead of 30. And it's way _easier_ to crash into

• the sun from Pluto, since you only have to accelerate to a speed of five kilometers per

• second backwards.

• In fact, if you're trying to crash into the sun just using rockets, it's far more efficient

• to first go to the outer solar system where your speed is much lower, then do a second

• burn to counteract that slow orbital speed and allow you to fall directly into the sun.

• And that's precisely why early mission trajectories for NASA's spacecraft to study the sun proposed

• going out to Jupiter firstto make it easier to slow down and get to the sun. Ultimately

• they decided instead to use repeated flyby's of Venus to slow down the probe and save on

• rocket fuel getting to the sun.

• But how gravity assists work is a topic for another day. Speaking of whichhow long

• would a day be on the sun?

Nuclear waste. We've got a lot of it, it'll stay dangerous for tens of thousands of years,

Subtitles and vocabulary

Click the word to look it up Click the word to find further inforamtion about it

# Hitting the Sun is HARD

• 3 0
Summer posted on 2021/10/14
Video vocabulary