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    17 Facts About Space Travel That Will Make You Go "Huh"

    Robots have basically taken over the solar system, and it's great.

    1. Satellites aren't floating in space. They're falling, forever.

    Lookang / CC / Via

    Gravity is almost as strong in low Earth orbit (LEO) – where the International Space Station and lots of other satellites are – as it is on Earth's surface. But the satellites are moving so fast that they fall along the curve of the Earth. If they were travelling a bit slower, they'd spiral in and crash; if they were travelling faster, they'd spiral out and head into space.

    2. Almost all of the weight of a rocket on the launchpad is just fuel.

    NASA / Via

    There are some really stark equations involved in getting to space. If you want to take stuff into orbit, you need to get it travelling at about 8 kilometres a second – faster, if you want to leave orbit. To do that, you need a lot of fuel. But to carry that fuel up with you, you'll need more fuel. And to carry that fuel… The numbers get very large very quickly. About 85% of the 2,900-tonne mass of the Saturn V rockets used in the Moon launches were just rocket fuel.

    3. When a spacecraft uses a planet to speed itself up, the planet slows down a bit.

    ESA / Via

    Spacecraft often boost their speed by flying close to a planet, falling towards it, and stealing a bit of its speed – it's a little like bouncing a ball off the front of a car as it moves towards you. But it steals a little bit of the planet's energy as it does so. When the Voyager 1 probe flew past Jupiter, it sped up by about 16,000 metres per second (m/s), while Jupiter slowed down by about 0.00000000000000000001m/s.

    4. If the Earth was the size of a football, then no humans would have gone more than about 2cm from its surface since we last went to the moon, 44 years ago.

    Pumbaa80 / mattbuck / BuzzFeed / CC / Via

    Almost every manned space flight has been in low Earth orbit, aka LEO, which means no more than about 1,000km above the ground. The only humans who have ever left LEO were the 24 men on the Apollo lunar missions, which ended in 1972.

    5. By the way, if Earth were the size of a football, the sun would be about 25 metres across. The sun is quite big.

    lmspascale / CC / BuzzFeed / Via

    It would also be about 2,500 metres away. The nearest star, Proxima Centauri, would be more than 70,000km away, about a third of the distance to the (real-life) moon. Space is quite big.

    6. But we're in a golden age for space robots. There are two rovers crawling around on the surface of Mars right now.

    NASA / JPL / Via

    This is a selfie taken by Curiosity, the most recent robot to have landed on Mars. It's found extraordinary things, including evidence of flowing water. The other active one is Opportunity, which has been trundling around for 12 years.

    7. And there have been a few others that have fallen in service on the red planet.

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    8. There's a space probe that has been orbiting Saturn for the last 12 years as well.

    NASA / Cassini / Via

    Check out the ridiculous pictures it's been sending back. Next year it's going to crash into the planet, because its mission is over.

    9. And there's another one which has entered the orbit of Jupiter just last week.

    After 5 years traveling to #Jupiter, @NASAJuno arrives today! This video shows a peek of its final approach:

    There was also the probe we landed on a comet, and the one that's flying around Mercury, and one around Venus, and – look, there are quite a lot of robots whizzing around the solar system, basically.

    10. New Horizons, which flew past Pluto last year, is so far away that it takes 4 hours, 25 minutes for its radio messages to reach Earth.

    NASA / Via

    It's transmitting photos at a data rate of about 2kb/s – roughly equivalent to a dial-up modem in the mid-1980s. It'll take it until the end of this year to send all the images from the Pluto flyby back to mission control.

    11. Then there are the Voyagers. Voyager 1 is travelling at 17,000m/s, or 38,000 miles per hour. That means it would travel from New York to London in five minutes.

    NASA / JPL / Via

    The Voyager missions launched in 1979, heading towards the outer solar system.

    12. Getting Voyager 1 to reach Neptune accurately was the equivalent of sinking a 3,630km (2,260 mile) golf putt.

    YouTube / Lookit / Via

    That is "assuming that the golfer can make a few illegal fine adjustments while the ball is rolling across this incredibly long green", says NASA.

    13. Even though it's going so fast, for part of the year, Voyager is actually getting closer to Earth.

    Tau'olunga / CC / Via

    That's because the Earth itself is moving even faster – about 30,000km/s, or 67,000 miles per hour. Feel the wind in your hair! (You can't, obviously, because the Earth's atmosphere is moving at the same speed. If it wasn't it would kill you pretty much immediately.)

    14. And after 37 years, Voyager 1 has still only just made it out of the solar system.

    NASA / Via

    It's more than 20 billion kilometres, about 12 billion miles, from Earth, but it's only just reaching interstellar space. If you're wondering how the boundary between "the solar system" and "interstellar space" is defined, there's more info here.

    15. And that's just the start. It would take Voyager 73,000 years to reach the nearest star. If it was going in the right direction.

    NASA / Penn State University / Via

    It's not.

    16. But it's OK. We're not going to get to the other stars very soon, but our robots can take incredible images of them…

    Hubble / NASA / Via

    Like this wonderful image of the spiral galaxy M81, taken by the Hubble space telescope.

    17. …and learn more about them by the day.

    NASA / Via

    Twenty years ago, we didn't know there were any planets outside our own solar system. Now we know about more than 3,000, most of which were discovered by the space telescope Kepler – which once announced 715 new planets on a single day in 2014.

    Go humans! And also robots.

    Tumblr / NASA / Via


    If the Earth was the size of a football, the sun would be about 2,700 metres away; the mass of the Saturn V is 2,900 tonnes; and the velocity needed to reach orbit is a little less than 8km/s. An earlier version of this piece misstated these numbers.

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