Spacetime Manipulation

We live in a four-dimensional universe - three dimensions for space and one dimension for time. Combined they form what is called "spacetime". An amazing property of spacetime is that it works like a fabric - it can be bent and torn (although it is no easy task). Also, waves traveling through the fabric can travel at speeds greater than the speed of light. Now when it comes to propulsion, traveling through space by ejecting hot gas from the back of a spaceship is somewhat of a brute-force approach. Manipulating the actual fabric of spacetime around your spaceship is by far a more elegant method. Throughout my life, I never paid too much attention to this concept as it sounds like pure science fiction.

However, about a decade ago I first heard of LIGO (Laser Interferometer Gravitational-Wave Observatory). In essence, LIGO uses fancy lasers to measure (very precisely) the distance between two far away mirrors. The idea is that once a ripple in the fabric of spacetime (otherwise known as a gravitational wave) passes through LIGO it will slightly alter the distance between these two mirrors and scientists will be able to directly measure this change. In 2015, LIGO has for the first time successfully detected a change in the distance right after a merger of two black holes released a large gravitational wave. This change was incredibly small (1/10,000th the width of a proton!) but it was solid proof that a gravitational wave has been detected and that the fabric of space around us can in fact be squeezed and stretched. This really changed everything for me in terms of how I see the universe. Even though we still have no idea how to bend spacetime, we can measure how gravitational waves do it - and that is a good step in the right direction. Just think about atomic energy, we first learned how to observe it before learning how to harness it - it's how science goes.

In general, spacetime manipulation for the purpose of long-distance travel can be divided into two main methods: stretch the fabric or rip it apart.

The stretching method involves the compression and expansion of the fabric so that it remains consistent. Imagine for a second that we want to get from point A to point B as fast possible. One way is to build an ordinary spaceship and compress the space in front of it while expanding the space behind it. Basically, you would generate a gravitational wave around the ship and the ship will be surfing this wave all the way to the destination - this is also known as the "Alcubierre Drive". The amount of compression and expansion can be controlled much like a throttle. Generate a small wave and it will simply act like a booster to the existing engines onboard the spacecraft. A larger wave can boost the ship to a velocity that is orders of magnitude beyond the speed of light without violating any laws of Physics. This is possible because locally, on the wave, the spacecraft travels slower than light, but the wave itself can travel much faster. This method is akin to the "warp-drive" as depicted in many works of science fiction. Another way of linear manipulation does not involve a spacecraft, but rather two space stations, one at point A and one at point B. The space between the stations is compressed for a fraction of a second so that a person can step over to the other side. Once at the destination, the space is re-expanded to the original dimension. This method is similar to something like a teleporter.

The second method of manipulating spacetime is far more advanced. Instead of bending space, we are actually going to rip it. Ripping the fabric is great as it allows us to cover significantly more distance without all the compression and expansion work. Modern physics postulates this type of rip occurs in the center of black holes where the density is infinite, and time comes to a standstill. A sufficiency large black hole has gravity distributed in such a way that, in theory, a spaceship could make it to the center without too much trouble. We don't know if this point connects to anything else, possibly a "white hole" where a spaceship could emerge, on the far end of the universe. Another type of rip is also known as a wormhole. Unlike the black hole, the wormhole has both an entrance and an exit. Some scientists believe that wormholes permeate the universe, like tiny rips engraved in the fabric of spacetime. If we learn how to find them, expand them, and keep them open for sufficiently long, there could be some very interesting applications for travel - but again, this is a process that we yet to understand.

At the end of the day, although spacetime manipulation is by far the most theoretical method of space travel, it is rooted in solid physics and has wonderous implications. I can't wait to see all the new observations coming from LIGO and how these will impact our understanding of spacetime. Who knows, maybe there is another trick to bending spacetime that does not require the collision of two massive stellar objects? I certainly hope so! Who's up for the challenge?

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