I like simple experiments and champagne. So, I've combined two of my favourite things to see if time travel from the future to the past is possible. I'm throwing a party, a welcome reception for future time travellers.
This was a famous experiment conducted by Stephen Hawking in 2009 to test backward time travel.
Unfortunately, it concluded with the following statement:
What a shame! I was hoping a future Miss Universe was going to step through the door.
Back then, I was a kid and it broke my heart—after all, travelling back in time was the greatest adventure. Hawking didn't outright deny the possibility of backward time travel, but he was not optimistic. I won't be taking you back in time, but I hope to rekindle the optimism (or maybe not).
First, let's take a look at our time machine: Imagine a device that takes a human (humans were harmed in this experiment) at location x₁, y₁, z₁, at time t₁ and moves them through space-time to a new location x, y, z at time t. In our case t < t₁. When we talk about time travel, we're only talking about time—"space" is given no space. So, let's talk about space.
Let's take a look at Hawking's invitation: Picture an elegant card with fancy typography, yet minimalistic. All in all, a solid 8/10. It describes the time and location of the event using coordinates. But these coordinates are not absolute—they're dependent on the earth's center. And since we know that earth is moving through space, the position of these coordinates is constantly changing relative to everything not under the control of the earth's gravity.
I hope you see where I'm going with this. Looking back at our time machine concept, I described the post-travel coordinates as x, y, z, because they are not the same as x₁, y₁, z₁. So, if anyone tried to travel back in time only, they would probably be left hanging in the void. This is a point which sounds so obvious, but I don't see it mentioned anywhere. I can't blame them—it only occurred to me recently.
To solve this problem, we need a way to calculate the displacement of earth's coordinates over time.
Let's consider the movement of the earth through space:
All this results in a beautiful, spiraling path through space—imagine a cosmic dance of our planet, tracing elegant patterns as it moves through the universe. The earth doesn't simply circle the sun; it follows the sun's own journey through the galaxy, creating a helical trajectory that's both complex and mesmerizing.
Credit for these fascinating speed statistics goes to the amazing Vsauce!
All this doesn't cover everything, but still, in theory, we can put all this into our machine and calculate our new coordinates, right?
Well, maybe not, as in our calculations, we are taking our reference point as 'The Great Attractor'. So we are assuming that 'The Great Attractor' itself isn't moving, which may or may not be true. Even a small movement by the Great Attractor will cause havoc to our plans. Also, all these speeds are just averages—even earth is not moving around the sun at the same speed all the time.
On top of that, earth and other celestial objects haven't always traveled at the same speed. Small changes during interactions of large objects, due to collision or gravity, affect these speeds, and these events are random. And if you stretch the timeline long enough, these small changes add up. You only need to be off by about 100 km to miss the earth completely. And when we're talking on such massive scales, 100 km is pretty insignificant.
So, now the real question is, after knowing all this, if you were from the distant future when time travel is invented, would you have attempted to arrive at Hawking's Party?
Also, feel free to challenge and poke holes into this theory. The universe is vast, and my understanding is still evolving.