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Can a bullet last forever?

This is an interesting question that many people may wonder about. When a bullet is fired from a gun, it travels at incredibly fast speeds before eventually coming to rest somewhere. But could a bullet theoretically keep traveling forever if shot into space? Let’s take a closer look at some of the factors involved.

What Happens When a Bullet Is Fired on Earth

When a bullet leaves the barrel of a gun here on Earth, it can travel anywhere from 700 miles per hour to up to around 5,000 miles per hour depending on the type of firearm and ammunition used. Many types of bullets travel faster than the speed of sound! But these high velocities don’t last for long.

The main forces that slow down a bullet are gravity and air resistance. Gravity constantly pulls the bullet down towards the ground. Air resistance, or drag, also slows the bullet as it pushes against the air particles in its path. These combined forces mean that a bullet fired from a gun on Earth will typically travel no more than 1-2 miles before gravity brings it back down to the ground.

Firing a Bullet in the Vacuum of Space

Things work much differently when you fire a bullet in space. With virtually no gravity or air resistance, a bullet could theoretically keep traveling almost indefinitely with little to slow it down. Once a bullet leaves the barrel of a gun, it requires no additional energy to keep its velocity. That initial “push” from the firing gun gives it a constant momentum that it will maintain until acted on by an outside force.

In the vacuum of space, that outside force could only really be if the bullet collided with something substantial like a planet, star, or large asteroid. Barring any major collisions like that, the bullet would keep moving in the same direction essentially forever. However, over extremely long time periods, minor gravitational forces from distant objects may slowly alter the bullet’s trajectory.

Challenges of Firing a Gun in Space

While firing a bullet in space sounds interesting in theory, actually accomplishing it would pose some significant challenges:

  • Recoil – With no air resistance, the recoil from firing a gun could send both the shooter and the gun flying uncontrollably in zero gravity.
  • Heat buildup – Most guns rely on convection to dissipate heat. In space, heat could quickly build up and melt the firearm.
  • Oxygen supply – Firing gunpowder requires oxygen. A supply would be needed for multiple shots.
  • Aim – With no reference points, accurately aiming would be extremely difficult.

Special space-rated firearms have been developed to try and address some of these limitations when firing in zero gravity environments.

Speed and Distance a Bullet Could Travel in Space

Let’s assume a bullet was fired perfectly horizontally from a floating space station with an initial velocity of 2,500 meters per second (about 5,600 mph). How far would it travel?

With no forces acting on it, the bullet would continue at a constant 2,500 m/s essentially indefinitely. In the table below, we can calculate how far it would travel over various time periods:

Time Distance Traveled
1 second 2,500 meters
1 minute 150,000 meters
1 hour 9,000,000 meters
1 day 216,000,000 meters
1 year 78,840,000,000 meters
1,000 years 78,840,000,000,000 meters

After 1 year, the bullet would have traveled about 49 million miles! After 1,000 years, that distance grows to a staggering 49 billion miles. For reference, Pluto orbits the Sun at a distance of about 3.7 billion miles. So our theoretical bullet could travel over 13 times the Earth-Pluto distance after millennium of uninterrupted motion.

Long-Term Effects on a Bullet in Space

While a bullet fired in interstellar space may theoretically travel dozens or hundreds of billions of miles given enough time, some other long-term factors could affect it:

  • Gravity – The cumulative gravitational pull from distant stars and galaxies would slowly tug on the bullet, changing its trajectory by tiny fractions of a degree.
  • Particle impacts – Interstellar dust and atomic particles would continually bombard the bullet, slowly eroding its surface.
  • Entropy – The bullet would very gradually decay at the atomic level due to entropy, limiting its lifespan.
  • Extreme time spans – After perhaps trillions or quadrillions of years, the bullet may finally collide with a stray particle or object.

So while a bullet fired into space could potentially travel vast distances over human timescales, geological timescales, or even stellar lifetimes, over many trillions of years other forces would gradually end its journey through the cosmos.


In summary, a bullet fired in the vacuum of space with no atmosphere or gravity could indeed keep traveling almost indefinitely with no major forces to stop it over short timespans. After thousands or millions of years though, gravitational tugs and erosion will slowly alter its course. And on timescales of trillions of quadrillions of years, entropy and eventual collisions will finally bring the epic journey of our eternal bullet to an end.