The simple quick answer is 3,958.8 miles – the mean radius of the Earth in miles. In other words, if you dug a tunnel straight down, you'd reach the center of the Earth after going 3,958.8 miles, and then you'd need to go another 3,958.8 miles to reach the opposite side of the planet.
The average distance to the centre of the Earth is 6,371 km or 3,959 miles. In other words, if you could dig a hole 6,371 km, you'd reach the center of the Earth. At this point you'd be in the Earth's liquid metal core.
The time it takes to drill through the important half of the inner core would take 1,140 years. Add up all those numbers and you get – drumroll please – a grand total of 10,260 years to drill into the true center of the Earth using conventional drilling technology.
Realistically, we will never get anywhere near the Earth's core. The levels of heat, pressure and radioactivity (one of the main sources of internal heating) are so high that even if we could bore through over 6,000km of rock and metal, a probe would be unable to survive.
Not only has no one ever drilled to the centre of the Earth, no one has ever even managed to drill through the Earth's crust. In fact, we know more about outer space than we do about what's under the Earth's surface! We know that Earth has layers. The Earth is made up of a crust, mantle, and core.
Earth's core consists of a solid iron-nickel ball rotating within a layer of liquid metal. But that ball may not be as simple as it seems: new research suggests the inner core contains its own inner core. If so, this so-called innermost inner core may record an early phase in Earth's evolution.
From there, they can extrapolate what the temperature of the iron based on the pressure at the center of the Earth. That led to the conclusion that the temperature of the center of the Earth is about 6000 degrees Celsius – a temperature about 9% higher than what exists on the surface of the Sun.
To begin with, it would take a tremendous amount of energy to penetrate the Earth, even more than it takes to hurl a rocket into space. The first step sounds impossible already! To this day, the deepest humankind has ever gone is just 7.6 miles below our feet — which is just 0.2% of the distance to the Earth's core.
We cannot go to the center of the earth, since the temperature and pressure increase enormously as we go deeper inside the earth. Also, no technology has been invented yet to travel deep into the earth.
Temperature in the inner core is about 5,200° Celsius (9,392° Fahrenheit). The pressure is nearly 3.6 million atmosphere (atm). The temperature of the inner core is far above the melting point of iron. However, unlike the outer core, the inner core is not liquid or even molten.
The pressure in the Earth's core is more than 3,000 times the pressure at the bottom of our deepest ocean. The temperature is more than 5,000°C. Your poor little tunnelling machine would be crushed to a pea and then cooked to a bubble of gas long before it could get anywhere near Earth's core.
Supernovas are the hottest thing in the Universe as they reach a million degrees Celsius. These explosive events occur when a star between 8 and 40 times more massive than our Sun reaches the end of its stellar lifecycle and explodes when its core collapses.
Earth has a very hot molten iron core. If it cooled down, the planet would grow cold and dead. Cooling also could cost us the magnetic shield around the planet created by heat from the core. This shield protects Earth from cosmic radiation.
In the core, the process of nuclear fusion creates temperatures of approximately 27,000,000° F. A temperature of 27 million degrees Fahrenheit is more than 12,000 times hotter than the hottest lava on Earth! If the core is the hottest part of the sun, what's the coolest part?
Surface-dwellers know that Earth spins on its axis once about every 24 hours. But the inner core is a roughly moon-size ball of iron floating within an ocean of molten metal, which means it is free to turn independently from our planet's large-scale spin, a phenomenon known as super-rotation.
There are three main sources of heat in the deep earth: (1) heat from when the planet formed and accreted, which has not yet been lost; (2) frictional heating, caused by denser core material sinking to the center of the planet; and (3) heat from the decay of radioactive elements.
If Earth were to stop spinning but continue to orbit the sun, a "day" would last half a year, and so would the night. It could warm up much more during the day and cool down much more during the night. This would affect the climate on Earth.
Greenhouse gas concentrations and global temperatures will not increase indefinitely — today's carbon dioxide buildup and warming trend must eventually top out and then reverse as the atmosphere gradually recovers.
The planet's core has been cooling for billions of years but perhaps "more rapidly than expected," which could expedite the end of life on Earth — though not for quite a while.
The heaviest of them all are black holes and neutron stars. In fact, they weigh so much that it's nearly impossible to wrap your head around numbers that far off the scale.
Black holes are freezing cold on the inside, but incredibly hot just outside. The internal temperature of a black hole with the mass of our Sun is around one-millionth of a degree above absolute zero.
It's more honest to say that the fastest 'physical' thing in the Universe is light itself (or in fact the entire electromagnetic spectrum). Of course, the Universe has a self-imposed speed limit – the speed of light, which is 299,792.458km/s. Nothing moves faster than this.
How deep into the Earth have humans been able to drill?
Humans have drilled over 12 kilometers (7.67 miles) in the Sakhalin-I. In terms of depth below the surface, the Kola Superdeep Borehole SG-3 retains the world record at 12,262 metres (40,230 ft) in 1989 and still is the deepest artificial point on Earth.
Perhaps the most well-known effort to pierce the Earth is Project Mohole (began in 1961), which was an attempt to drill through the Earth's crust in the Pacific Ocean off the coast of Mexico where the crust is shallow.