The idea sounds like something from science fiction: point an extraordinarily powerful laser at the ground, burn through the Earth's crust, continue through the mantle and core, and emerge somewhere on the opposite side of the planet.
But could it actually work?
In principle, a sufficiently energetic beam can vaporise rock.
In practice, however, firing a laser through the Earth is an entirely different problem. The planet is not a giant block of material waiting to be drilled through. It is a colossal, hot, high-pressure body whose interior would absorb, scatter and transform the beam long before it reached the other side.
The deeper we go, the more extraordinary the problem becomes.
The Earth's Crust Is Only the Beginning
The Earth's crust is relatively thin compared with the planet itself. Oceanic crust is typically around 5–10 kilometres thick, while continental crust can be roughly 30–70 kilometres thick.
That might sound manageable when compared with the Earth's diameter of approximately 12,742 kilometres.
It isn't.
Even modern drilling technology has barely scratched the surface. The deepest artificial borehole ever drilled, the Kola Superdeep Borehole in Russia, reached about 12.3 kilometres.
That is only around 0.1 per cent of the distance to the Earth's centre.
And drilling becomes increasingly difficult with depth because temperature and pressure rise dramatically.
A laser might appear to offer an alternative because it does not require a physical drill bit. Instead, it could theoretically concentrate electromagnetic energy onto the rock, heating it until it melts or vaporises.
The problem is what happens next.
What Happens When a Laser Hits Rock?
A sufficiently powerful laser can heat material extremely rapidly.
At relatively low energies, the rock would simply become hot. Increase the energy density and it could melt. Increase it further and material could vaporise, producing an expanding plume of extremely hot gas and particles.
But this creates an immediate problem for the laser. The material being removed does not simply disappear.
A cloud of vapour, molten rock and debris would occupy the newly created hole. That material could absorb, scatter or defocus subsequent laser energy.
Instead of producing a perfectly clean tunnel, the laser would be trying to shoot through its own debris.
Engineering a system capable of continuously removing that material would be essential.
And Then Comes the Mantle
Below the crust lies the mantle, extending to a depth of roughly 2,900 kilometres.
It is often described as molten rock, but that is misleading. Most of the mantle is solid rock. It behaves as a solid over short timescales, although it can flow extremely slowly over geological periods.
Temperatures increase enormously with depth, while pressure reaches levels vastly beyond anything encountered at the surface.
A laser powerful enough to excavate a tunnel through the mantle would therefore face a completely different environment from the one encountered in a laboratory.
And the tunnel itself would have another problem. It would not stay open.
Under enormous pressure and extreme temperatures, surrounding rock would deform and flow into the cavity. Depending on the depth and conditions, the walls could collapse or creep inward.
The deeper the tunnel became, the more difficult maintaining an open passage would become.
The Core Makes Things Even Stranger
At a depth of approximately 2,900 kilometres, the laser would reach the Earth's outer core.
Unlike the mantle, the outer core is predominantly liquid. It is composed mainly of iron and nickel, with temperatures comparable to the surface of the Sun.
Beyond the outer core lies the solid inner core.
The pressure at the centre of the Earth is estimated to be millions of times atmospheric pressure.
A hypothetical laser tunnel would therefore have to pass through:
Crust → Mantle → Outer Core → Inner Core → Outer Core → Mantle → Crust
The beam would need to survive approximately 12,742 kilometres of increasingly hostile material.
That is where the concept effectively collapses.
Light Doesn't Simply Travel Through Rock
A laser beam travels through transparent materials remarkably well.
Rock is not one of them.
Ordinary rock strongly absorbs and scatters visible and infrared light. The deeper the beam penetrates, the more energy is deposited into the surrounding material.
This is fundamentally different from firing a laser through air.
You cannot simply increase the power indefinitely and expect the beam to keep travelling.
At sufficiently high intensities, the material in front of the beam can become plasma. That plasma can interact strongly with the incoming laser radiation, potentially absorbing or reflecting part of the energy.
The laser would therefore be fighting the material it is trying to destroy.
Could We Use an X-Ray Laser?
Perhaps a different wavelength could solve the problem.
Shorter wavelengths, such as X-rays, can penetrate some materials more effectively than visible light.
But this doesn't magically turn the Earth transparent.
The interaction between electromagnetic radiation and matter depends on wavelength, density and composition. Even highly penetrating radiation eventually interacts with enough material to be absorbed or scattered.
More importantly, producing and directing the enormous amount of energy required would present an extraordinary engineering challenge.
We are no longer talking about a giant version of an industrial laser. We would be talking about an energy system on a planetary scale.
How Much Energy Would Be Required?
There is no single meaningful number because it depends on how large the tunnel is, how quickly it is created and how efficiently the energy can be transferred into the material.
But even an extremely narrow tunnel would involve an enormous quantity of rock.
Imagine a tunnel only one metre in diameter running through the Earth's entire diameter.
Ignoring the complications of Earth's interior and simply treating the path as a cylinder, the volume would be roughly:
π × 0.5² × 12,742,000 metres
That is approximately 10 million cubic metres of material. Rock has a density of roughly 2,500–3,000 kilograms per cubic metre.
So even this tiny hypothetical tunnel would involve tens of billions of kilograms of rock. And that is before accounting for the vastly greater energy required to heat, melt or vaporise it.
A larger tunnel would increase the problem dramatically.
What About Drilling Instead?
Interestingly, conventional drilling faces some of the same fundamental obstacles. We have developed extraordinarily sophisticated drilling technology, particularly for oil, gas and scientific research.
But the deepest holes remain tiny compared with the Earth's dimensions.
Temperature, pressure, equipment limitations, geological instability and the difficulty of removing material all become increasingly severe with depth.
A laser would remove the need for a mechanical drill bit, but it would not remove the underlying physics.
The rock still has to absorb the energy. The material still has to go somewhere. And the enormous pressure and temperature still exist.
What If We Fired the Laser From Space?
This sounds even more spectacular. A laser mounted on a satellite could theoretically be aimed at the Earth's surface.
But the atmosphere would introduce another problem.
Air absorbs and scatters some wavelengths of electromagnetic radiation, while turbulence can distort a beam. A sufficiently powerful laser would also interact with the atmosphere in complicated ways.
Even if we somehow delivered the beam perfectly to the ground, however, the fundamental problem would remain.
The laser would encounter kilometres of rock almost immediately. Space does not provide a shortcut through the planet.
Could a Laser Tunnel Ever Reach the Other Side?
Under the laws of physics, there is no simple rule saying that a sufficiently energetic laser cannot destroy a path through matter.
With an effectively unlimited energy source and technology far beyond anything humanity possesses, one could imagine systems capable of removing extraordinary quantities of material.
But that is very different from saying that we could build such a device.
The Earth is simply too large, too massive and too hostile. A conventional laser beam would not remain an intact beam through thousands of kilometres of rock. Its energy would be absorbed and transformed into heat, plasma and radiation long before reaching the opposite surface.
Even if we somehow created the tunnel, maintaining it would be another enormous challenge.
And There Is One Final Problem
Suppose, against all expectations, that a perfectly straight tunnel somehow existed from one side of Earth to the other.
What would happen if we dropped something into it?
Ignoring air resistance and the rotation of the Earth, the object would accelerate towards the centre, pass through it and continue towards the opposite side.
It would slow as it climbed out of the gravitational field, eventually reaching the surface with theoretically zero velocity.
Then gravity would pull it back again.
The object would oscillate through the planet.
In reality, friction, air resistance, Earth's rotation and the physical properties of the tunnel would radically alter this behaviour.
But the thought experiment illustrates something remarkable.
The Earth's interior isn't merely an obstacle to be drilled through. It is an enormous gravitational, thermal and geological system.
Could lasers go deeper than Kola?
Yes — lasers could potentially remove rock at depths beyond the Kola Superdeep Borehole, but there’s an important distinction between laser-assisted drilling and simply firing a laser down a hole.
The Kola borehole reached about 12.26 km. At that depth, temperatures were around 180°C, far hotter than expected, and conventional drilling became increasingly difficult.
Could a laser beat it?
In principle, yes. Lasers can heat, melt and vaporise rock without physically contacting it. A future drilling system could potentially use a high-powered laser to:
- melt or vaporise rock at the bottom of a borehole
- fracture rock through rapid heating
- weaken rock ahead of a conventional drill
- potentially create a vitrified or glass-like lining around the borehole
- reduce mechanical wear on drilling equipment
But there is a major catch: the laser still has to get its energy to the bottom.
A laser travelling through air is one thing. A laser travelling through kilometres of rock is another. The practical approach would therefore probably involve a laser delivered through a fibre-optic system or another waveguide, rather than shining a beam through solid Earth.
And depth creates another problem
The deeper you go, the hotter and more pressurised the environment becomes.
At 20–30 km, conditions are already extreme. At 50 km, you're approaching or penetrating the crust depending on location. At hundreds of kilometres, you're entering the mantle.
A laser could remove material, but it doesn't eliminate the need to:
remove the material → control the heat → maintain the borehole → transport equipment and energy → prevent the hole from collapsing.
That's why a laser doesn't automatically turn a 12-km drilling record into a 1,000-km one.
But there's a fascinating possibility
Lasers might actually be more interesting as a hybrid drilling technology.
Imagine a drill that mechanically breaks the rock while a powerful laser simultaneously heats and weakens the material ahead of it. The laser does some of the destructive work, while the mechanical system removes the resulting material.
That could potentially allow drilling into rocks that are extremely difficult for conventional equipment.
And there is research into laser-assisted and other energy-assisted drilling technologies, although nothing remotely approaches drilling thousands of kilometres into the Earth.
So the intriguing question isn't really:
"Can a laser drill through the Earth?"
It's:
"Could lasers eventually let us drill substantially deeper than Kola?"
That's a much more scientifically plausible — and genuinely interesting — question.
The Verdict
Could a laser burn through rock?
Yes.
Could an extraordinarily powerful laser excavate material?
In principle, yes.
Could a laser simply be fired into the Earth and emerge on the other side?
No—not with anything resembling technology available today, and certainly not by simply increasing the power of an existing laser.
The real obstacle isn't merely the thickness of the crust.
It is the 12,742-kilometre journey through an intensely hot, high-pressure planet, combined with the absorption of electromagnetic energy, the behaviour of plasma and molten material, the removal of billions of tonnes of excavated matter and the tendency of the resulting passage to collapse.
The idea belongs comfortably in science fiction.
But it raises a fascinating question about our planet: despite everything humanity has achieved technologically, we have barely penetrated the Earth's surface at all.
The deepest hole humans have ever made is little more than a scratch on the skin of the planet.
And beneath that scratch lies an entire world we have never directly visited.
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