We put this question to Dr Graeme Hirst, from the STFC's Central Laser Facility...

Graeme -   These days they can, yes.  The very first laser that was produced worked in the near infrared.  It was really, really bright, so you could probably see it, but only just about.  Gradually, as time went on, more and more lasers were developed with a wider range of available colours – a wider range of available wavelengths.  And these days, the range is spectacular.  Just last year, a group of scientists in America demonstrated a really high power laser that’s actually working in the x-ray region.

We put this question to Dr Graeme Hirst, from the STFC's Central Laser Facility...

Graeme -   It is an interesting thought.  Yes, and in principle you can.  People have looked at it for a number of applications.  One is, can you use it to power that satellite?  Satellite power is a tough challenge, and yes, in principle, it can be made to work, but there are issues, obviously.  You'd have to decide how you're going to keep people you wanted out of the way, out of the way of the beam.  It’s kind of an unwritten rule that you never point a laser at anything you don't intend to do.  And so, you would have to ask how you make sure it wouldn't go wrong.  You've also got efficiency issues because even now, even with the very best lasers, they're not 100% efficient at converting electricity into light and then converting it back again.

We put this question to Dr Graeme Hirst, from the STFC's Central Laser Facility...

Graeme -   Well that’s a good question.  If you shone them directly into one another, then you're quite likely to break the lasers unfortunately. But if you imagine you're going to misalign them slightly so that the beams crossed, but they don't go down the throat of the opposing laser, then if you were to do that in a vacuum, if you just have one light beam crossing another then to all intents and purposes, nothing happens.  Once you get to extreme physics conditions where the laser intensity does become spectacular - and in some experiments we do, we’re getting there - you might imagine that you can perturb the vacuum.  You can change the vacuum with the intensity of light you need.  But mostly, this is interesting if you cross the two beams over in some kind of material, and if you do that, you can achieve all sorts of interesting effects in the material by combining two laser beams, through the properties of the material.

We posed this question to Graeme Hirst from the STFC Central Laser Facility...

Graeme: -  Yes it can.  They're already used in this application, certainly for cleaning expensive things.  The trick is to choose a laser so that the colour of the laser light matches the colour of the graffiti ink.  [that can then be used to heat the graffiti ink, and blow it off the wall without heating the wall up.]  So, yes, it’s a very neat solution for cleaning dirty stuff off expensive things.  Unfortunately, it’s not always cheap and you do have to make sure there’s no one around.

Ben: - Is it also true that you can use lasers to have a look through the paint and try, and find fraud in paintings?

Graeme: -   Yes, you can.  Again, you choose the right colour.  Now, what you're looking to do is to choose a colour which is not absorbed by the top layer of paint so it goes straight through.  It’ll be absorbed by something a bit lower down, it’ll bounce back off that and whether it’s there or not, you will get bounce-back or not and by mapping out the bounce-back, you can look at the layer below the paint layer.

We posed this question to Graham Hirst from the STFC Central Laser Facility...

Graeme -  Well some do.  It’s not just true of laser light.  In fact, you’ll know that if you got one of those really, really powerful torches, you're warned not to put your hand directly in front of it,  it will also be giving off a lot of heat.  That really reflects the fact that heat - in the form of thermal radiation - and light are just the same sort of stuff.  If you like, light goes blue, green, yellow, orange, red, infrared, heat.  You can get lasers that work in the heat part of the spectrum as well.  Some of them have very long wavelength indeed, cutting and welding lasers for instance will put out 10,000 watts of heat at the most powerful end.

We posed this question to Graeme Hirst from the STFC Central Laser Facility...

Graeme - You're trying to fight a thing called diffraction and that depends on how big you can make your laser beam down at the earth.  A back of the envelope calculation - laser light spreads out about one wavelength in 10 metres.  It’s 400,000 kilometres to the moon.  You’ll probably get something about 40 metres across [on the moon].  As a football metaphor, we’d be looking at something about twice the size of the 18 yard box.