0:00:10 > 0:00:11Hey, everyone.
0:00:11 > 0:00:14Martin here with the big stories this Wednesday.
0:00:14 > 0:00:17First, the world's longest and deepest train tunnel has
0:00:17 > 0:00:19officially opened in Switzerland.
0:00:19 > 0:00:22It's taken 17 years to build the Gotthard tunnel, which goes
0:00:22 > 0:00:25for 57 kilometres under the Alps.
0:00:25 > 0:00:29And today, fireworks greeted the first trains.
0:00:29 > 0:00:31The tunnel gives a high-speed rail link between Northern
0:00:31 > 0:00:32and Southern Europe.
0:00:32 > 0:00:38It's more than two kilometres under the mountains at its deepest point.
0:00:38 > 0:00:40Now to something else that's massive -
0:00:40 > 0:00:41the Square Kilometre Array project.
0:00:41 > 0:00:44When it's finished, the radio telescope will be the most powerful
0:00:44 > 0:00:47in the world and be able to search further into space than ever before.
0:00:47 > 0:00:49And there's one big question scientists hope it will
0:00:49 > 0:00:50help us answer.
0:00:50 > 0:00:55Here's Ayshah.
0:01:04 > 0:01:09Aliens.
0:01:09 > 0:01:13Are they really out there?
0:01:13 > 0:01:17And, if so, are we ever going to find them?
0:01:17 > 0:01:20The universe is vast.
0:01:20 > 0:01:24Our solar system is one of the solar systems around a sun,
0:01:24 > 0:01:28which is one of the millions of stars in our galaxy.
0:01:28 > 0:01:30Our galaxy is one among the millions of galaxies
0:01:30 > 0:01:31in the universe.
0:01:31 > 0:01:32So, why not?
0:01:32 > 0:01:34Maybe there is life somewhere in another solar
0:01:34 > 0:01:39system in another galaxy.
0:01:39 > 0:01:41That is what scientists are trying to find out
0:01:41 > 0:01:44with the help of these.
0:01:44 > 0:01:46This is the Square Kilometre Array project.
0:01:46 > 0:01:50When it is finished, it will be the world's most
0:01:50 > 0:01:52powerful radio telescope, so sensitive that it will be able
0:01:52 > 0:01:58to detect a signal from a planet that is tens of light years away.
0:01:58 > 0:02:01These telescopes are listening for intelligent life
0:02:01 > 0:02:05and that is why they have decided to build them here.
0:02:05 > 0:02:07What makes this place in South Africa perfect
0:02:07 > 0:02:10is that there is no radio waves around to mess up the signal.
0:02:10 > 0:02:15That's no microwaves, no mobile phones -
0:02:15 > 0:02:17I've had to turn mine off.
0:02:17 > 0:02:21Every day, these dishes are collecting massive amounts
0:02:21 > 0:02:23of data, which will eventually be processed by a supercomputer
0:02:23 > 0:02:30in the UK where experts will look for any signs of life.
0:02:30 > 0:02:33How do you go about looking for alien signals?
0:02:33 > 0:02:38Well, you have got big telescopes like that and they can go listen
0:02:38 > 0:02:42in the universe and listen for radio signals from other planets
0:02:42 > 0:02:45where we hope they also have radio signals and maybe we can detect
0:02:45 > 0:02:46some of these signals.
0:02:46 > 0:02:50How would we know that an alien has tried to contact us?
0:02:50 > 0:02:52We are looking for intelligent signals, signals that are not
0:02:52 > 0:02:59from nature but that are made by intelligent creatures.
0:02:59 > 0:03:01Will we ever be able to find an alien?
0:03:01 > 0:03:02I certainly hope so.
0:03:02 > 0:03:04I hope to find them once in my lifetime.
0:03:04 > 0:03:06It would be such a big discovery.
0:03:06 > 0:03:09But it could be very long and it could also take very long
0:03:09 > 0:03:11to communicate with them because the signals take maybe years
0:03:11 > 0:03:14to go to the civilisation and also take years to get back,
0:03:14 > 0:03:18so one simple question and answer could take, like, 40 years.
0:03:18 > 0:03:22Of course, there's no guarantee that other civilisations exist
0:03:22 > 0:03:24beyond our world, but, if they do, it might not be long before
0:03:24 > 0:03:30SKA finds them.
0:03:31 > 0:03:34From searching for aliens to searching for pop stars -
0:03:34 > 0:03:38X Factor bosses have just announced this year's "new" judging line-up,
0:03:38 > 0:03:41which they hope will help save the show from years
0:03:41 > 0:03:42of falling ratings.
0:03:42 > 0:03:44Ricky's got this.
0:03:44 > 0:03:46The all-new X Factor is actually...
0:03:46 > 0:03:53pretty old.
0:03:53 > 0:03:58Faces from the past are returning to search for a new star.
0:03:58 > 0:03:59Louis Walsh, Sharon Osbourne and Nicole Scherzinger
0:03:59 > 0:04:02rejoin Simon Cowell.
0:04:02 > 0:04:05Don't forget, Dermot's back, too.
0:04:05 > 0:04:11To be honest, it feels like we've gone back in time to the old school.
0:04:11 > 0:04:15That's because all these judges have featured on the show before.
0:04:15 > 0:04:18Sharon and Louis launched a series more than ten years ago and singer
0:04:18 > 0:04:24Nicole became a judge in 2012.
0:04:24 > 0:04:31Today, ITV released this pic to get us all excited about the new series.
0:04:31 > 0:04:33Yep, that's four chairs with the names on the back.
0:04:33 > 0:04:38I'm sure you can all hardly contain your excitement.
0:04:38 > 0:04:41So can these familiar faces bring back a bit of familiar sparkle
0:04:41 > 0:04:43to The X Factor?
0:04:43 > 0:04:46And you can tell us what you think about this year's line-up over
0:04:46 > 0:04:48at Newsround online.
0:04:48 > 0:04:49That's all from the TV team today.
0:04:49 > 0:04:51Ayshah's back tomorrow morning.
0:04:51 > 0:04:57See ya!