Name: It's Surprisingly Hard to Go to the Sun
Uploaded: 2018-08-24T03:26:20.000Z
Duration: 2 min 24 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

NASA's Parker Solar Probe will soon fly closer

to the Sun than any spacecraft before it-about 4 million

miles from the visible surface. But getting that close to the Sun

requires some fancy orbital mechanics. It takes 55 times

more energy to go to the Sun than it does to go to Mars.

Why is it so hard to get to the Sun? The answer is related to why

Earth doesn't just fall straight into the Sun, despite the strong gravitational

attraction. Earth, and everything on it, is traveling very

fast-about 67,000 miles per hour-in a direction that is

basically always sideways relative to the Sun. If you launch a

rocket from Earth, straight toward the Sun, it won't lose that sideways speed,

and so it will miss the Sun. The only way to get the rocket

to go right into the Sun is to cancel all that sideways motion. Leave

even a little bit and it will miss the Sun and enter a new orbit.

To cancel Earth's motion, you have to launch the spacecraft backward as fast as Earth

is hurtling forward. But 67,000 miles an hour is really

fast. Spacecraft have to go upward at only 25,000 miles

an hour to escape Earth. Getting to Mars only requires a bit

more speed: 29,000 miles an hour. New Horizons,

which NASA sent rushing out to Pluto, managed 36,000 miles

per hour, or a little more than half what it would have to hit the Sun

instead. Since Parker Solar Probe plans to fly past the Sun,

it doesn't need to cancel out all of Earth's sideways speed, but it does need to remove

53,000 miles per hour of it. That's why it's using one of the most

powerful rockets available and additional gravity assists from Venus

over a period of several years. In this case, rather than speeding up

the spacecraft as in a typical gravity assist, Venus slows down its

sideways motion, so the spacecraft can get close to the Sun.

When it finally does make its closest approach to the Sun, Parker Solar Probe

will have lost much of its sideways speed, but gained a great deal of overall

speed, thanks to the Sun's gravity. Parker Solar Probe will hurtle

the very first human-made object to get that close.