Profiles

Interviewer: Nukki
Technical illustrator. Makes technical illustrations and illustrations for instruction manuals.
Also a proficient writer of articles that utilize her own illustration skills for websites such as Daily Portal Z.

*Interview was conducted remotely.

Table of Contents

・How Does a Time Machine Work?
・Negative Mass - The Ticket to Going Beyond the Speed of Light and Back in Time
・Parallel Worlds and Time Paradoxes
・Does Goku's Instant Transmission Function like a Time Machine?
・Time Machines, Coming Soon...?!

How Does a Time Machine Work?

——In Dragon Ball, Bulma made a time machine by herself in the future. Is creating a time machine in the real world theoretically possible?

Prof. Futamase: We don't know yet. However, in physics we are yet to prove that creating a time machine is not possible. For now, let's just assume that creating a time machine is possible, shall we?

——So time machines are still in the R&D stage!

Prof. Futamase: At this time, we've confirmed that speeding up and slowing down the flow of time is possible. We can't manipulate it to a great extent yet, but we're able to speed it up and slow it down by a tiny fraction, which involves both the speed of light and gravity.

——If you watch movies about time travel, they often say that the closer to the speed of light you get, the slower time moves... but this is the first I've heard of gravity being involved.

Prof. Futamase: We'll be here all day if I go into the fine details, so I'll try to keep it brief. In General Relativity, the stronger a gravitational field is, the more warped space-time becomes around it, and the slower time moves in that area. For example, gravity on the Sun is stronger than it is on Earth, so it's believed that 1 second on the Sun is actually longer than 1 second on Earth.

——Oh, so the stronger gravity is, the slower time moves!

Prof. Futamase: In the same way, gravity around a black hole is much greater than it is on Earth, so 1 second spent in the vicinity of a black hole is equivalent to 10~20 years on Earth. So in that way, the flow of time isn't constant—it varies based on your location or the planet you're on.

——I feel like our conversation is veering closer to time machines. You already said that we don't yet know if creating a time machine is possible or not, but is it feasible for humans to travel to and from the past and future?

Prof. Futamase: Travelling to the future is theoretically not that difficult. Remember what we just said about the effects of spending time in a place with stronger gravity. Ignoring the impracticalities for now, imagine that you travelled from Earth to a black hole. You then spend just 10 seconds near said black hole and return home. Now, when you return to Earth, far more than 10 seconds have passed, and from your perspective, you've travelled forward in time.

Negative Mass - The Ticket to Going Beyond the Speed of Light and Back in Time

——The time machine in Dragon Ball is a kind of egg-shaped craft with stilt-like legs attached, but what sort of shape do you imagine a time machine that humans could use would be?

Prof. Futamase: It could either be a craft that's capable of surpassing the speed of light, or a physical space that bends space-time and creates a 'shortcut' through it.

——A craft that's faster than light... But hang on, I thought light was the fastest thing in the universe?

Prof. Futamase: In physics today, yes, it's believed that nothing can travel faster than the speed of light. Light moves as quickly as it does because it has zero mass. If you accelerate an object with a non-zero mass, its mass increases exponentially as you get closer to the speed of light, essentially prohibiting it from ever reaching the speed of light. However, if the mass is zero, then you can circumvent that issue and reach the speed of light.

——So does that mean that in order to surpass the speed of light, at the very least you need reduce your own mass below zero?

Prof. Futamase: With our current understanding, that's not believed to be possible, but that may change since it hasn't yet been proved impossible.

——I see. The "physical space" option sounds a bit like the Room of Spirit & Time.

Prof. Futamase: In the real world, it's theorized that we could create a sort of tunnel to the past. There are currently people researching what type of energy would be necessary for that to be possible.

——On a related note, what type of fuel do you think would be required to power a time machine?

Prof. Futamase: Our understanding today is built on the assumption that you would have positive mass. However, research has already shown that matter with negative mass also exists. So you could cancel out your positive mass with this "negative matter" to reduce your overall mass to zero, then potentially even pass through solid walls moving at the speed of light.

——So the fuel would have "negative mass". That's a little hard to wrap your head around...

Prof. Futamase: It's actually not that far-fetched a concept—there are already numerous discussions being had about its existence. It's thought that around 70% of the universe is made up of negative matter, which permeates it in its entirety and is the driving force behind the universe expanding at a speed greater than the speed of light, which is something that astronomers and physicists acknowledge as fact.

If we learn how to manipulate negative matter, it'll surely have a huge impact on all our lives and may be exactly what we need to unlock the ability to travel to and from the past and future.

——But how do we get to that point?

Prof. Futamase: That's exactly what we're trying to get to the bottom of now. It's like how in the past, we weren't able to extract oil from the ground, but as our civilization advanced, we became able to do so, and were also able to burn that oil and harness its energy. So I don't think it's unrealistic to think we'll be able to take the same leaps with negative matter.

——Woah! Now you've got me excited for the future!

Parallel Worlds and Time Paradoxes

Now that we've all hopefully got at least a vague understanding of how time machines could work, I decided to ask about parallel worlds and time paradoxes. Time paradoxes occur when some kind of contradiction or loop is created due to your travels to and from the past and future, and in order to enable time travel, we'd have to find a way to resolve them.
Even within Dragon Ball, Trunks altered his universe's history slightly by going back to the past to discover the Androids' weakness. It's this process that gives rise to multiple futures, i.e., parallel worlds.

——Could you tell me a bit about the latest parallel-world research?

Prof. Futamase: The concept of parallel worlds originates from the study of quantum mechanics. It says that at this moment, there are infinite universes that exist, and each one of them contains one 'you'. So if there were, say, 10 universes, then you'd simultaneously exist in all of them.

Simply by cognizing, "I'm here", the universe around you manifests. This is what's known as the many-worlds interpretation.

——So you're saying that there are multiple universes and that the universe in which you assert, "I'm here!", becomes fixed as 'your universe'...?!

Prof. Futamase: We're living in a reality built on the multitude of universes that are constantly being spawned with every decision we make. Assuming you travelled to the past, you wouldn't be in the past of this universe, which is the result of the accumulation of decisions made by its inhabitants, but a completely different one—in other words, a parallel universe. That reasoning allows us to resolve the paradoxes that accompany time machines.

——So in Dragon Ball, the future where the Androids run rampant and the one where they're defeated are actually completely separate universes?

Prof. Futamase: That's right. If you successfully travelled to the past then attempted to return back to the point in time you started from, the universe you arrive to would not be your original one, but a parallel world where you had travelled to the past. You'd essentially be in a new universe with a different history.

——So just to clarify, even if you never step foot in a time machine, the decisions you make from moment-to-moment spawn new universes...?!

Prof. Futamase: Precisely.

Does Goku's Instant Transmission Function like a Time Machine?

——Listening to everything you've spoken about so far, I thought of something else I'd like to ask you about. After his battle with Frieza, Goku travels to Planet Yardrat, where he learns how to use Instant Transmission. I have a feeling that Instant Transmission works in a similar way to a time machine, but what do you think?

Prof. Futamase: It's exactly the same. If you interpret Instant Transmission as movement faster than the speed of light, then Planet Yardrat must've found a way to overcome the gravitational restraints.

——So Yardrat's civilization must be far more advanced than Earth's!

Prof. Futamase: There's a strong chance that they're successfully using negative matter. That's exactly the sort of planet that scientists like myself are hoping we'll be able to make contact with.
It's currently estimated that of the approximately 200,000,000,000 planets in the Milky Way, around half of them have water and an atmosphere similar to Earth's.

——There are that many...!

Prof. Futamase: However, it takes around three billion years for intelligent life to evolve. On Earth, for example, it took close to four billion years for human life to emerge. So if a given planet is younger than that, then we can't get our hopes up.
It's also worth noting that even the lowest estimates predict that there are one billion Earth-like planets in each galaxy. It seems inevitable that civilizations make advancements, and so it wouldn't be strange in the slightest for highly advanced ones to exist.

——It sure would be nice of beings from those advanced civilizations or from the future to pay us a visit.

Prof. Futamase: Even assuming there were one hundred million of such civilizations... if those one hundred million were spread across the galaxy, then the distance between each of them would be roughly 100~1000 light years. I suppose we can only conclude that a civilization capable of using Instant Transmission over that sort of distance hasn't yet emerged.

——So it's possible that they're making their way towards Earth at this very moment!

Prof. Futamase: Don't forget there's no guarantee that they're organic lifeforms like us. Instead, they could potentially exist as data-based lifeforms.

——So perhaps signals from aliens or beings from the future are all around us, it's just that we don't have the technology to detect them... It's hard not to get swept up in all the possibilities!

Time Machines, Coming Soon...?!

I asked Professor Futamase about time machines, parallel worlds, and time paradoxes, and our conversation just kept expanding from there.

Research into time machines is still ongoing, but so long as they're not proved impossible, there's still hope that one day we'll succeed in building one!

With research being conducted as we speak and the ever-present chance that we'll make contact with more advanced civilizations, who knows what surprises the future—and the past—hold!