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Time to take it back to GCSE physics.

Force = mass × acceleration.

That is the conundrum at the centre of this fight.

The match is being fought at a catchweight of 155lbs. 

Khan fought at 146.5 in his last fight - a win over Chris Algeri a year ago.

He has jumped up to 155lbs for tonight, but it is a weight that suits Alvarez far better. Some in the Mexican's camp have put it about that their man will be around 170 lbs as he climbs into the ring later.

Instead Khan will be relying on the other half of that equation - his blurring hand speed - to inflict defeat by a thousand blows.

BBC Radio 5 Live

Mike Costello's commentary is an essential part of evening's like this.

BBC Radio 5 live's man will call the shots with former world champion Paulie Malignaggi - who lost to Khan back in 2010 - alongside him.

You will be able to listen to their wise words on this very page from just before 04:00 GMT. 

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As Saul Alvarez faces King/Citizen Khan we are also after your fighter/entertainment mash-ups.

Let's get creative with this one...

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Load up on espressos, turn up the music, do 50 star jumps. 

Whatever it takes...

We are expecting the fighters in the ring shortly after 04:00 GMT. 

So in the meantime let us know your tactics for going the distance to the first bell via #bbcboxing, external and BBC Sport Facebook., external

The anticipation is half the enjoyment anyway. And there is plenty of fat to chew before we get to the prime cuts of the actual fight...

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Amir Khan's date with destiny is here.

After the best part of two years pining in vain for a shot at Floyd Mayweather, the Briton has jumped up two weight divisions to meet the formidable Saul 'Canelo' Alvarez.

If he wins, he is catapulted instantly to legend status.

If he loses, his hopes of being part of the superfights, competing at the very stratosphere of the sport, might be gone for good.

In Las Vegas tonight, no-one is playing for as high stakes as the lad from Bolton. 

From Olympic medallist...

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...via shock defeats...

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...via sensational gung-ho victories...

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... it all leads to this.

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Which brings us to the main event.

Britain's Amir Khan taking on the fight of his life as he steps up in weight and class to face Saul 'Canelo' Alvarez in Las Vegas.

It is an absolute monster of a fight and we will have round-by-round updates as well as full 5 live audio commentary back here from 02:30 GMT ahead of ring walks at an expected 04:00 GMT.

See you here.

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This golden age for British boxing - with Anthony Crolla one of 11 world champions from these Isles - continues.

Some massive nights ahead.

And some even bigger very early mornings.

Not everyone was impressed...

Don: Don't rate him at all he's not top class but fair play he won tonight I'll let him have that one.

The brave tactics paid off. 

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WBA lightweight champion Anthony Crolla tells Sky Sports: "I knew I could beat him. I told Eddie Hearn that I'd beat him. It got my back up that people thought I'd avoid this fight. This is my house and nobody comes into my house and takes what I've got.

"Barroso thought he would get me out of there after three rounds - and he did hit hard - but Joe Gallagher got his tactics spot on. There was no way this title was leaving Manchester tonight. This might have just topped the night I won the world title for the first time."

Lots of praise for Crolla on Twitter from footballers and his fellow boxers.

Where next for Anthony Crolla?

There has been talk of a battle of Manchester against undefeated Mancunian Terry Flanagan.

Promoter Eddie Hearn plays it coy when asked about possible next opponents.

"Don't worry about other people," he tells Sky Sports. 

"This boy came into the most dangerous fight in the division. This lad has gone from nice bloke, to good story, to world champion to the best lightweight in the world.

"He is called 'Million Dollar' Crolla now let's go and get some."

The WBA lightweight strap is plastered across Anthony 'Million Dollar' Crolla's chest.

This win might make that nickname a reality. His skills alone are enough to make him a prospect for big nights Stateside.

Throw in the following that he would bring over from Manchester and the backstory behind him and you have pure box office.  

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Hashim Vali: Crolla got his tactics perfectly right and has won.

The final punch that left Ismael Barroso crouched on the canvas was barely a brush on the ribs, but the Venezuelan had gutted himself in the early rounds.

He didn't get close to making the count. 

Anthony Crolla roars to the Manchester Arena rafters.

And Manchester Arena replies with roars of their own.

A win for brains over brawn.

Crolla soaked up the storm and when Barosso turned from action man to sitting duck the Manchester man marched him down.

Superb.

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