Digging a tunnel directly through the Earth to the other side is a thought experiment that raises two fundamental questions: where exactly would you emerge, and how would the physics of the planet affect the trip? Answering this requires locating the precise geographical opposite, known as the antipode, and understanding the immense geological obstacles and gravitational dynamics of the Earth’s interior.
Finding Your Antipode: Where Exactly Is the Other Side?
The antipode of any location is the point on the Earth’s surface that is diametrically opposite, connected by a straight line passing through the planet’s center. Less than 15% of the Earth’s land surface has another landmass as its antipode. The vast majority of land points, including the entire mainland of the United States, have their antipodes located in the ocean, such as the Indian Ocean.
Only about 4.4% of the Earth’s surface features land-to-land antipodes. The largest areas include the Malay Archipelago, which is opposite the Amazon basin and the Andes mountains. Christchurch, New Zealand, is almost perfectly opposite A Coruña, Spain. The Australian mainland is the largest landmass whose opposite point is entirely ocean, while the island of Borneo is the largest landmass whose opposite point is entirely land (opposite a section of the Amazon rainforest).
The Reality Check: Why We Cannot Dig Through the Earth
The hypothetical tunnel must contend with the reality of Earth’s internal structure, making the project functionally impossible with current technology. The planet’s crust, the hard outer layer, ranges from about 3 to 25 miles deep, yet no human-made drill has ever fully penetrated it. The deepest vertical hole drilled, the Kola Superdeep Borehole in Russia, reached 7.6 miles (12.2 kilometers) before being abandoned.
The primary barriers to deeper drilling are the exponential increases in temperature and pressure. At the Kola Superdeep Borehole, temperatures reached 356°F (180°C), causing equipment failure and making the rock behave plastically. Deeper still, the temperature climbs towards the mantle, reaching over 1,600°F, and eventually peaking at temperatures comparable to the surface of the sun at the core.
The next major layer is the mantle, a viscous, semi-solid rock that flows slowly over geological time and extends for nearly 1,800 miles. The enormous pressure and heat at this depth would cause any conventional tunnel to immediately collapse. Beyond the mantle lies the outer core, a superheated liquid metal, and finally the solid inner core, where pressures are millions of times greater than at the surface. No known material could withstand these forces to maintain an open, stable tunnel.
The Physics of the Perfect Tunnel: A Trip Through the Center
Assuming a perfectly stable, vacuum-sealed tunnel running straight through the Earth’s center, the journey becomes a problem of gravitational physics. Upon dropping into the hole, a traveler would immediately begin to accelerate, pulled by the planet’s gravity. As the person descends, the gravitational force does not remain constant because the mass of the Earth pulling them down decreases as more mass is left above them.
The force of gravity would continue to pull the person toward the center, reaching maximum velocity at the midpoint. At this center point, the gravitational pull would momentarily drop to zero because the traveler would be surrounded by an equal amount of mass in every direction. Due to the momentum gained, the person would shoot past the center and begin to decelerate as the gravitational pull from the opposite side slowed them down.
In this ideal, frictionless environment, the traveler would slow to a stop exactly as they reached the surface on the opposite side, having enough momentum to complete the journey without needing propulsion. The entire process of falling from one surface to the other would take approximately 42 minutes, a time calculated by treating the motion as a form of simple harmonic oscillation. Without stopping themselves, the traveler would then begin to fall back toward the original starting point, oscillating back and forth through the tunnel until air resistance or tidal forces eventually caused them to settle at the center.