Ever seen a UFO?
However implausible they may be,
the idea holds a powerful grip on our collective imagination.
And UFOs raise fascinating questions,
not just about what particular sightings might be but also
about the nature of space travel and communication across the universe.
Answering those questions involves some incredible science.
And so this month, we ask, "What have UFOs ever done for us?"
Since I was a little girl, I always hoped that one day
I would wake up to find visitors from another world.
Sadly, I'm still waiting.
I wish we could bring you the first interview with aliens
but instead, we are back here at the Jodrell Bank Observatory,
a place long associated with the search for extraterrestrial
intelligence and somewhere which is famous for studying objects
so strange that they were labelled as little green men.
But this month is also a poignant reminder of how difficult
space travel is.
11 years after it disappeared,
the Beagle 2 spacecraft has been found on the surface of Mars.
We celebrate a mission that came tantalisingly close to triumph.
Coming up, Dallas Campbell opens the MOD's UFO files
and asks what it would take for aliens to visit us.
There are some basic questions we have to ask
and one of those questions is, "Is interstellar travel possible?"
Pete reveals what really lies behind
some of the most common UFO sightings.
Plus, the unexpected radio signal that for a brief moment
looked like it might just be communications from little green men.
It was pulsing, which is not what a radio astronomer
expects from the sky.
The three little letters, U-F-O,
conjures up all sorts of images in our minds
and have led to countless controversies.
Of course, when we talk about UFOs,
we are talking about the idea of visitors from outer space.
Although science doesn't preclude the existence of life
elsewhere in the universe,
scientists are extremely dubious about UFOs visiting us here on Earth.
Despite this, sightings keep coming in thick and fast.
We have asked Dallas Campbell to investigate
what people are seeing and to find out why the probability of aliens
visiting our planet is so unlikely.
The modern UFO phenomenon began in 1947.
An American pilot, Kenneth Arnold,
was flying above the Cascade Mountains in Washington state
where he describes seeing nine saucerlike objects
flying as if they were being skimmed across the water.
Since then, thousands of UFO sightings have been reported -
bright lights, mysterious dark shapes and even the odd abduction.
At the National Archives in south London,
a wealth of these documented sightings are safely stored away.
These are really exciting.
These are the official X files documents, if you like.
These are the MoD collated reports of unidentified flying objects.
There was a great story of a whole load of schoolchildren
who had seen an unidentified flying object and had
written into the Ministry of Defence and all the letters are still here.
Some of the children had actually drawn pictures of what
they had seen.
There is letter here from the MoD dated 1967 telling the children
there were, in fact, low-flying aircraft in the area at the time.
Sounds pretty plausible to me.
This flying saucer report actually made the papers. This is from 1966.
This amazing picture of a flying saucer filmed from an aircraft
by a woman "will set the world talking" and it certainly did.
But, luckily, good old Tomorrow's World solved the mystery.
'Our cameraman sat in the same seat as Mrs Oldfield had.
'Through the window,
'notice how the glass is slightly convex where it meets the frame.
'Here it comes. Tomorrow's World very own UFO.
'What we are seeing now is a direct view of the tailplane
'of the aircraft seen at an acute angle to the window glass.'
Whether these UFO reports are unexplainable or not,
it's worth thinking about the UFO question from a different angle.
If a civilisation was visiting the Earth from a faraway
solar system, there are some basic questions we have to ask
and one of those questions is, "Is interstellar travel possible?"
We live in a world governed by the laws of physics.
And to the best of our knowledge, they apply throughout the universe.
It's these laws that make interstellar travel
so incredibly improbable.
Of course, the problem with travelling around space is
that space is big, really big,
and the distance between stars is absolutely vast.
It's so vast that even light, which is the fastest thing we know,
takes years to travel between them.
Even our fastest spacecraft like Voyager 1
would take at least 70,000 years just to reach our nearest star.
So, how could we or any other spacefarers cross such
unimaginable distances? Well, you could try going really, really fast.
But going faster is incredibly difficult and not
just for the obvious reason that it takes a great deal of effort.
Over a century ago, Einstein worked out that the faster you travel,
the heavier you get.
If I were to accelerate up to the speed of light,
my mass would become infinite
and the amount of energy I would need to move would also be infinite,
which might get a bit tiring.
But, funnily enough, going fast is only part of the problem.
Once you get to where you're going, how do you then stop?
The faster you've been travelling,
the harder it is to lose all that momentum you've built up.
So, in order to stop in space, you would need another engine
with the same force pushing you back the other way.
And this is a problem we struggle with in our own solar system
when we send probes to other planets.
Stopping a spacecraft, once it has reached its destination,
is one of the hardest things in space exploration.
There may be a way round this, though.
Instead of trying to go faster,
could we not make the distance itself shorter?
Crazy as that sounds, there may be a way to do just that.
There's a theoretical solution to this interstellar dilemma -
something known as a wormhole.
These are tunnels through space time,
connecting two distant places.
Cosmic shortcuts like this
could hold the key to visiting other worlds.
I'm meeting theoretical astrophysicist Roberto Trotta
to find out how likely these sci-fi staples really are.
Theoretically, is it something we can even consider,
even think about, even talk about?
Conceivable, yes, absolutely
and theoretically, you can find solutions
to Einstein's general relativity equation that describe
such a shortcut, a wormhole, in fact.
But you want to be able to go through it and possibly come back.
In theory, a wormhole could be formed by two black holes connecting
to create a bridge but there's a problem.
This possibility wouldn't be traversable. You couldn't take a shortcut through a black hole
because, first of all, practically, you would be dead.
It would hurt. It would hurt. Spaghettification terribly hurts.
What do you call it? Spaghettification.
When you get spaghettified by the tidal forces of gravity.
That is something you don't want to do.
So, in terms of...
If you want to engineer the wormhole of a kind
that would allow you safe travel,
you might possibly be able to use one that is already there
but even that is not guaranteed
because the wormhole would need to have
a large amount of negative energy,
which is something we don't really know if it exists.
But let me get this, we don't know if there are any wormholes,
we haven't made one, this is all... All speculative.
It's all equations on a board, effectively,
people speculating about what kind of reality
those equations could possibly describe. Got it.
No-one said, "Ooh, look, what's that funny thing?" "A wormhole."
No. We're not even... No, we don't even know how to look for one.
So, let's assume a wormhole had happened.
Presumably, we're going to run into all kinds of practical problems, still.
It's not just, "We built a wormhole, we can all go on holiday."
There is the strength of the forces, the time it would take,
not to you as a traveller,
but the time that would pass for people back home.
Time would flow differently for you than for people back home
and so you don't want to go on holiday and come back
and everybody has died 10,000 years ago. That would be silly.
And the other problem is that even just theoretically,
um, if such wormholes were to exist,
you could use them to travel back in time,
which seems to be something that is fundamentally forbidden
and that might be an argument why they might not exist.
South of France is nice this time of year.
I think I might just plump for that instead. Yes.
Even though the probability of finding aliens that have
zipped across the universe to visit us is very small,
there is still a possibility that they are out there.
As a result, we have combed the cosmos,
searching for signs of their existence.
Chris is speaking to pioneering astrophysicist Jocelyn Bell Burnell
who discovered a signal that looked like the one we'd been waiting for.
It had long been assumed that if an alien civilisation tried to make
contact with us, the signal they send would have some key characteristics.
It would be in the radio part of the spectrum, as radio waves travel
easily across the vastness of interstellar space.
It would be persistent, not a one-off,
and it would have a rapidly repeating pattern.
This is exactly what was found in 1967.
Jocelyn, we have to start by talking about this remarkable discovery
that you made in Cambridge in the late 1960s.
So, what were radio telescopes like then? What were you using?
Radio astronomy,
at that stage, we quite often
built our own radio telescopes -
four and a half acres, lots and lots of wooden posts,
looks a bit like a hop field, wires trailing along the top of the posts,
120 miles of wire and cable in that radio telescope.
But it worked.
And the output was primitive, too?
Yes, everything came out as hard copy. Moving pen over chart paper.
Wiggle, wiggle, wiggle, wiggle -
um, 100 feet of chart paper every day.
And in inspecting that vast amount of paper, you spotted something unusual.
What flagged this particular signal as an interesting discovery?
Well, it didn't look exactly like the quasars which I was meant to be looking at.
It didn't look exactly like interference.
It turned out to be a thing that was pulsing
once every one-and-a-third seconds,
which is not what a radio astronomer expects from the sky.
It's regular, and it's rapid.
Stars can't turn on a sixpence, this thing was.
What on earth is it?
It has all the hallmarks of artificial, man-made interference,
but it's coming from the same spot amongst the stars.
So, it got this nickname, LGM-1 for "little green men."
Was that a serious consideration, at the time?
I named it, and I have to say I now regret it.
It wasn't serious, it was very much tongue-in-cheek.
And we did check out whether it might be little green men,
extraterrestrial civilisations,
arguing that if it is, those little green men live on a planet
that goes round their sun.
And as the planet goes around their sun, some of the time, it's
coming towards you, the observer, and the pulses pile up closer.
And sometimes it is moving away from you and the pulses spread out.
So I did a lot of careful monitoring of pulse arrival times
and we found one of these Doppler shifts, as it's called,
but it was due to the motion of the Earth around the sun
because Doppler shift works
for the Earth moving, as well as the source of the radio waves moving.
You've successfully discovered that the Earth goes around the sun? We proved it, yes. Yep.
So, you had one of these things. Yeah. Erm...what happened next?
It was about a month after we'd found the first one,
we had a meeting to discuss how to publish this.
It was a real problem when you've got one example of a crazy result.
And I remember that meeting because that night, looking at
some chart recordings from a totally different bit of sky,
saw a quarter inch of suspicious looking signal,
pulse, pulse, pulse, pulse,
this time one-and-a-quarter seconds apart.
But, clearly, the same kind of thing, same family,
totally different bit of the sky.
And that... that was the eureka moment.
The first one was just too darn worrying.
These things turned out to be what we now call pulsars. Yep.
So what do we know about pulsars? What are they?
They're formed in supernova explosions. Part of that explosion
is that collapse of the core.
And a pulsar is a collapsed core,
weighing about the same as the sun
but it's all squashed into a ball about ten miles across,
so really dense.
My analogy for the density of a pulsar is you take a sewing thimble,
you take the population of the globe,
you jam the seven billion people, one by one... Carefully. Hard!
..into this thimble.
And when you've got it fool of seven billion people, squashed,
it weighs the same as if it were made of pulsar material.
So, it's really dense stuff.
And the whole thing spins incredibly fast.
Some of these things are spinning 700 times a second. Really fast.
Scarily fast. We see these as these very rapid pulsations. Yes.
And, incredibly regularly.
Because when you get 1,000 million million million million tonnes of stuff spinning,
it's very hard to make it change its spin.
So, it's a clock. And indeed, we make use of that these days.
These things are clocks out in the galaxy and we use them
to check out Einstein's relativity.
We should talk about another mystery,
something that has been bothering radios astronomers recently.
These things called fast radio bursts. What do we know about that?
Not a lot.
They've been picked up by the pulsar people
because they are short, sharp pulses, and pretty strong.
And I think the first thought was,
"Oh, this is freakishly large pulse from a pulsar."
But, actually, nothing ever comes from that bit of space again.
For one of them, they had another eight telescopes
quickly slewed to the position, X-ray telescopes,
optical telescopes and more radio telescopes.
There's nothing to be seen after the bust has happened.
So, there's a whfft! And that is it.
It's fun we're still finding these things. Isn't it?
And I think there will be more,
as we do more of this short time duration transient astronomy
which astronomers really are only getting into now.
It is just beginning.
To find out more about fast radio bursts
and how astronomers are trying to find them,
check out our website at bbc.co.uk/skyatnight.
In a few moments, we'll turn from aliens travelling to visit us
to the problems we humans have exploring our own solar system,
as we look at Britain's attempt to visit Mars with Beagle 2.
But first, Pete Lawrence is here to show us
how easy it is to find UFOs.
There are all sorts of things up in the sky
which try and trick us into thinking that
aliens visiting from other worlds.
And I want to show you what some of these things are.
Ours skies are populated with objects that, at first glance,
look like they're straight out of a science fiction film.
One of the most common are clouds.
Some clouds look really otherworldly.
Just look at this amazing image back here.
Now, these are what are known as lenticular clouds
and this particular photograph was taken from Halifax in the UK.
But, typically, lenticular clouds form over mountainous regions
where the weather is warm, moist and stable.
But there are even stranger clouds than this.
This bizarre gap in the cloud is called a "fall streak hole"
or "hole punch cloud" and it occurs when something happens
to cause ice crystals to form right in the centre.
They fall out of the sky, leaving behind this amazing hole.
Of course, some UFO sightings are actually space-based.
Many people mistake satellites for either planes or shooting stars.
But sometimes, when the conditions are just right,
they can look really spectacular.
This is what's known as an iridium flare.
What you're seeing is sunlight reflected off flat
surfaces on the satellite's body.
It's so UFO-like because the light appears from nowhere
and then just vanishes away.
Most are predictable, and if you go onto our website
there's a link there to help you find out how to see a flare for yourself.
But there are stranger appearances still.
From time to time, rockets carrying spacecraft into orbit
dump fuel, and this can create a bizarre and mysterious
glowing shape, which is visible in the night sky.
And then there's this.
This image was taken from northern Norway in 2009,
and it's not a manipulated image.
This is actually what was seen in the sky.
Hard to believe as it may be,
this was the result of a Russian missile test.
The rocket malfunctioned, leaking a trail of fuel as it spun.
But the other factor was the time of day.
For the photographer, the sun was below the horizon,
but up in the upper atmosphere, the sunlight was able to
illuminate the released fuel, creating this spooky effect.
Finally, the celestial object that's mostly like to be confused
with a UFO has to be the planet Venus.
Though it might sound strange to think
you could mistake a planet for a flying object,
but Venus certainly seems to be able to pull off this trick.
And there are apocryphal tales of pilots seeing Venus
and thinking it's an oncoming aircraft.
And now, to the news from Mars.
Beagle 2, the UK's first and only attempt at a Mars lander
has been missing, presumed destroyed, for over 11 years.
But now, a team using images from NASA's remarkable
Mars Reconnaissance Orbiter
think they've seen signs of Beagle safe on the surface.
We'll be finding out what this means for the mission
in just a few moments.
But first, lets remind ourselves of the Beagle story
and what happened over Christmas in 2003.
Beagle 2 was designed to sample the surface of Mars.
The lander was the brainchild of Colin Pillinger
who believed passionately that Beagle could
answer the big question -
whether there was life on the red planet.
There is every chance
that there could be a niche on Mars
where there is some kind of life.
That's what Beagle intends to do, analyse the atmosphere,
see if there is a trace of methane in the atmosphere,
because if there is, it shouldn't be there
unless there's biology constantly producing it.
Beagle 2 was carried to Mars on board ESA's Mars Express.
But strict weight restrictions and a firm deadline
meant the tiny probe had to rely on a novel, and untested, landing system.
It involved using a series of parachutes to slow
the spacecraft in Mars's thin atmosphere,
and then hoping the air bags could cushion its impact.
The mission captured the public imagination.
Cultural icons Blur recorded a call sign to be played when Beagle
woke up and Damien Hirst got involved,
designing the colour calibration card.
In late December 2003, Beagle 2 began its treacherous decent,
with touchdown scheduled for early on Christmas Day.
Colin and his team waited for the landing signal to come back,
but none was received.
On this mission, our faith has been unshakable that the mission
would go ahead, and we've crossed lots of bridges to get this far.
So, we'll keep the unshakable faith until the point comes
when we have to say it's no longer worth thinking about.
Despite weeks of trying, contact was never established
with the little spacecraft.
The mission was branded a failure.
ESA concluded that the landing system probably didn't work
and that Beagle 2 crashed into the surface.
But Pillinger, the eternal optimist, didn't agree.
I never, ever believed that we'd crashed,
and I certainly, probably, don't now.
Sadly, Colin never lived to discover what happened
to his spacecraft.
He died in May last year.
But now, we know.
The latest images from Mars suggest that Beagle
came closer to success than almost anyone had thought.
And Maggie's talking to Jim Clemmet who worked on the Beagle team.
It's 11 years since Beagle 2 disappeared.
How come we've found it now?
A high resolution camera
on Mars Reconnaissance Orbiter has,
over the years,
been taking images of Mars,
including about 11 or 12,
overlapped across the landing ellipse of Beagle 2.
And a number of those images are showing
an artefact on the surface of Mars.
The images appear to show a number of objects that scientists
believe were the rear cover, parachute and the lander itself.
Even though it's just a few pixels wide,
closer views appear to reveal the telltale shape of Beagle 2,
and suggest that the spacecraft had begun to deploy its solar panels.
So, this is the first panel to come out,
and this is covered, about 80%, with solar cells, which are glass.
So, very reflective. Very reflective.
And then the next panel would be this one.
And we think we're looking at something like that.
'And if this the case,
'it radically changes our view of the mission's success.'
Well, it means that the entering descent and landing system worked.
That the lander survived impact onto the surface.
That all the electronics absorbed that shock.
'So, Beagle 2 was not lost after all.
'Not only did it successfully touchdown on Mars,
'it also began to operate.
'So, why have we heard nothing for over a decade?'
If we open these up now, you will see.
So, underneath here is the antenna. A-ha. Yes.
OK, so, if all the panels had opened up, as we see now,
then the antenna would have been free to communicate
and then the mission would have been able to proceed.
And so, whilst we know where Beagle is now,
there's no means of trying to restart it.
So, there's no way of communicating with it. Yes.
'Even so, Beagle 2 still has a hold on us.'
There are other parts of the Beagle mission that were also a success.
For example, encouraging young people into science,
technology, engineering.
And I know there are people out there now who are engineers or
scientists because of Beagle.
'Perhaps the late Colin Pillinger summed it up best.'
It was not a failure.
Deferred success.
Triumph, not disaster.
Now, back to all things UFO.
And if we're serious about finding aliens,
we don't have to wait for them to come to us.
We can look for them.
Here at Jodrell Bank, they're working on a system
that will allow them to use their radio telescopes,
not to look for flying saucers,
but to search for signals from alien civilisations out in space.
The question is, what would that signal look like?
A regular pulse would be a good clue that the signal was artificial,
but we now know that's how pulsars appear.
And so the team at Jodrell are taking a different approach.
They want to hunt for radio emission that's confined
to such a narrow frequency range,
that they have to be artificial.
This is the live data coming in now off one of the telescopes.
So, what you're seeing, basically,
is this is frequency in the radio spectrum.
Like tuning your radio at home?
You could tune to different
frequencies along here.
So, there are signals there? Yeah.
So, that's it - aliens? We're done.
You know, people are communicating with us.
If it was easy as that, that would be great!
So, what you've got to do is tell the difference between
things that are natural sources of radio emission
and artificial sources.
So, we'd assume the aliens are producing some
sort of artificial radio emission. Sure.
Natural sources of radio emission, like stars or planets,
should emit across a broad range of frequencies.
And that's what the Jodrell radio telescopes are used to picking up.
But within this broad spectrum, there might just be a hidden signal.
And so, whilst the radio telescopes are scanning the sky
looking for everyday phenomena,
Tim is going to use the supercomputer here at Jodrell
to scan data that's normally thrown away,
hoping to find that telltale signal.
What you'd be looking for is a sort of spike
rising and falling in strength,
and that would be like an on-off message, if you like.
Or perhaps it drifts in frequency, because of...
If it's coming from a planet, that planet could be orbiting a star
and that would give this regular Doppler shift.
'But it's like looking for the proverbial needle in a haystack.'
If we go back to the earliest days of SETI,
there was this paper produced by two guys,
Cocconi and Morrison. There was a good line in there
that really summarises the whole thing for SETI
which is that, "The probability of success
"is difficult to estimate, but if we never search,
"the chance of success is zero."
Well, call us if the new programme finds something.
We will do, yeah. Good stuff. Good luck.
That's it for this programme
and next month we take a break.
Instead, standing in this very spot,
will be Brain Cox and Dara O Briain
with the return of Stargazing Live.
They've got a packed series of programmes.
I'll be there hunting supernovae,
but the true highlight will be the solar eclipse
that sweeps across the UK on the morning of March 20th.
For most of us, it will be a partial eclipse.
But the Stargazing Live team are heading north to the Faroe Islands,
so that we can all witness the majesty of a total eclipse.
We return after Easter, on 12th April,
celebrating 25 years of the Hubble Space telescope.
So, in the meantime, get outside
and get looking up. Goodnight.