Black holes form a natural time machine that allows for travel to both the past and the future, but this does not mean we can go back to the Jurassic period.
Currently, humanity has yet to develop any spacecraft capable of taking us close to a black hole. If we overlook this detail, time travel could potentially be achieved through black holes.
What is a Black Hole?
A black hole is an extremely dense object typically formed when a star is nearing its end or collapses. Like planets and stars, black holes have a gravitational field surrounding them. This gravitational field is what keeps us grounded on Earth and ensures that Earth orbits the Sun.
According to natural laws, the heavier an object is, the stronger its gravitational field.
The gravitational field of Earth makes space travel incredibly difficult. This is why we construct rockets that must move very fast to escape Earth’s gravitational pull.
Black holes form a natural time machine that allows for travel to both the past and the future. (Image: Getty Images)
The gravitational pull of a black hole is so strong that even light cannot escape it. This is impressive, as light is the fastest thing known to science.
This is also why black holes appear black. We cannot reflect light from a black hole in the same way we can reflect a flashlight beam off a tree in the dark.
Space-Time Distortion
Albert Einstein’s theory of general relativity tells us that matter and energy have a strange effect on the universe. Matter and energy warp and stretch space. The heavier an object, the more space is warped and stretched around it.
A massive object creates a type of “valley” or pit in space. When objects come close, they fall into the “valley.”
This is why when you get close enough to any massive object, including a black hole, you will fall towards it. This is also the reason why light cannot escape a black hole, or in other words, the edges of the pit are so steep that light cannot move fast enough to break free.
The valley created by a black hole becomes steeper as you approach it from a distance. The point at which it becomes so steep that light cannot escape is called the “event horizon.”
The “event horizon” is not only interesting for those wishing to be time travelers, but it is also of interest to philosophers, as it has implications for how we understand the nature of time.
If you want to travel to Earth’s future, simply fly close to a black hole and then return to Earth. (Image: Getty Images)
As space gets stretched, time does too. A clock near a massive object will run slower than a clock near a significantly smaller object.
A clock close to a black hole will tick slower compared to a clock on Earth. One year near a black hole could equate to 80 years on Earth, as illustrated in the film “Interstellar” (2014).
In this way, black holes could be used to travel to the future. If you wish to reach Earth’s future, just fly close to a black hole and then return to Earth.
If you get close enough to the center of the black hole, your clock will run slower, but you can still escape as long as you do not cross the “event horizon.”
The Time Loop
But what about the past? This is where things get really interesting. A black hole warps time dramatically. Imagine taking a piece of paper and connecting its ends to form a loop. That is what a black hole can do to time.
This creates a natural time machine. If somehow you could enter the loop, which scientists call a closed time-like curve, you would find yourself on a trajectory through space that starts in the future and ends in the past.
Inside the loop, you would also find that cause and effect become very tangled. Events that happen in the past shape the future, and this in turn causes events that occur in the past.
The gravity of a black hole is immense, which bends the regions of space and time near the event horizon. (Image: ESO)
You’ve found a black hole and you want to use a reliable spaceship to go back and visit the dinosaurs?
First, you can only travel to the past of the black hole. This means that if the black hole was formed after the extinction of the dinosaurs, you would not be able to go back to a time that is too far in the past.
Second, you may have to cross the “event horizon” to enter the loop. This means that to escape the loop at a specific moment in the past, you would need to break free from the “event horizon.” You would have to move faster than light, which is currently thought to be impossible.
Third and perhaps the worst part, you and your ship would experience the “spaghettification” effect. When you cross the “event horizon,” you would be stretched out like a piece of spaghetti. In fact, you could be elongated to the point of being just a twisted strand of atoms in space.
So, while it is fascinating to think about the time-bending properties of black holes, in the near future, a visit to the dinosaurs or traveling to the future remains purely theoretical.
