# Sightseeing near the speed of light – realistic simulation

Paraphrasing:

Just a note before you go,
A vision to be learned
Traveling near the speed of light
It’s easy to get …

Imagining how things would look when traveling near the speed of light is an interesting exercise. Using a freeware video game developed by MIT Game Lab (2012), this visualization (below) by The Action Lab is particularly interesting. An exploration of the various effects:

A Slower Speed of Light” hopefully corrects common misunderstandings – something that benefits contemporary physics classes.

OpenRelativity is a toolkit designed for use with the proprietary Unity game engine. It was developed by MIT Game Lab during the development of A Slower Speed of Light. The toolkit allows for the accurate simulation of a 3D environment when light is slowed down.

A Slower Speed of Light was developed in hopes of being used as an educational tool to explain special relativity in an easy-to-understand fashion. The game is meant to be used as an interactive learning tool for those interested in physics.[1]

I get confused by the perspective blend of inertial and quasi-accelerating frames of reference: walking at the same speed but the speed of light getting slower and slower. As noted [1], relativistic effects are indeed why the game becomes increasingly difficult, more challenging.

• YouTube > The Action Lab > “Slowing the Speed of Light Down to 2 m/s [walking speed] – What Special Relativity Feels Like” (August 13, 2020). “When we start walking, we start to see relativistic effects that include time dilation and length contraction, and also doppler shifting.”

Description: “In this video I show you what it would look like to slow the speed of light down to around walking speed. So with just walking around town you would experience relativistic effects. I talk about time dilation and length contraction and what it would look like to have it happen to you. Get the simulation created by MIT here.”

The Action Lab • Pinned by The Action Lab
The Action Lab (August 13, 2020)
Interesting note: Even Einstein was mistaken on length contraction. He had said that a sphere would look like an ellipsoid. However, Penrose later proved that a sphere would still be spherical, although rotated. Notice in the simulation how the spheres are the only objects that don’t look distorted when moving at near light speeds!

From transcript:

[Re doppler shift] So what that means is that normally light that we can’t see, like infrared light, as we walk towards it, it gets shifted more towards the red end of the spectrum instead of the infrared part of the spectrum; so, it moves up in frequency, and since it moves up in frequency, it becomes visible light to us.

… and also the effect is stronger – the brightness increases. that’s because as we’re walking towards it we’re actually hitting more photons along the way than we normally would, so basically it increases the intensity as we’re walking towards it.

Space and time are always connected. if you’re completely at rest – not moving, all of your movement is going through time and not through space. so you’re at rest but you’re still moving forward through time. but if you start to move forward through space, then that means your movement through time has to decrease. so the faster you move through space, the slower your movement through time is going to be.

Now of course this time dilation is only relative to somebody watching you do that movement. but you yourself always experience time at the same rate. but how it portrays itself to you as the first person view – as the person who’s walking at close to speed of light speeds – is that it seems like you’re going faster, so you can get more movement through space in a given time.

In this simulation, as i start to walk so as i approach the speed of light, things get stretched out. now the easiest way to see this is i’m going to turn off the doppler effect. collect my last orb, so now the speed of light is really close to my walking speed, so the relativistic effects are really strong here. so notice as i start to walk, now notice how far away the cliffs seem like they get, so the length gets stretched out. but i just told you that when you go closer to the speeds of light length actually contracts. now this is a really confusing point and a lot of people have gotten this wrong.

For the most part length contraction does not appear as something being squished, but it actually appears as something being stretched out and lengthened, and also rotated a little bit. even though length contraction is occurring, this is not what you would see. what you would see is completely different than what you would measure as length, and that’s because the photons in your line of sight in the direction of your travel are leaving the thing that you’re seeing at different points in the past.

So, for example, if you’re looking at something, you see it being stretched out because the [slower?] photons from the back of it take longer to get there than the front [faster photons?] of it, and so it actually appears as though the thing is being stretched out.

##### Notes

[1] Wiki:

In A Slower Speed of Light, the player controls the ghost of a young child who was killed in an unspecified accident. The child wants to “become one with light”, but the speed of light is too fast for the child. This is solved through the use of magic orbs which, as each are collected, slow down the speed of light, until by the end it is at walking speed. These orbs are spread throughout the level. At the beginning of the game, walking around and collecting these orbs is easy; however, as the game progresses, the effects of special relativity become apparent. This gradually increases the difficulty of the game.

As the game progresses and light becomes slower, the effects of special relativity start to become more apparent. These effects include the Doppler effect (red/blue-shifting of visible light and the shifting of ultraviolet and infrared into the visible spectrum), the searchlight effect (increased brightness in the direction of travel), time dilation (difference between the passage of time perceived by the player and the outside world), the Lorentz transformation (the perceived warping of the environment at near-light speeds), and the runtime effect (seeing objects in the past because of the speed of light). These effects combine as the game progresses to increase the difficulty and challenge the player.

Some commentary on the realism of this simulation – the optics of moving close to the speed of light:

• Stack Exchange > Physics > How realistic is the game “A slower speed of light”?

And the inherent limitations of OpenRelativity, as noted:

[2] A NASA cartoon about near-light-speed travel:

• YouTube > NASA Goddard > “NASA’s Guide to Near-light-speed Travel” (August 14, 2020)

[3] Media note re time dilation

• Stargate Atlantis > Season 2 > Episode 12 “Epiphany” (Jan 13, 2006) Colonel Sheppard gets trapped on a planet where time moves faster.

##### Related posts

• Biggest ideas in the universe – Sean Carroll chats concepts > The Biggest Ideas in the Universe | 6. Spacetime (Apr 28, 2020)

## 5 thoughts on “Sightseeing near the speed of light – realistic simulation”

1. John Healy says:

• Universe Today > “NASA’s New Video Shows You What it’s Like Traveling Close to the Speed of Light” by Matt Williams (August 20, 2020)

… near-light-speed travel comes with all sorts of challenges. … NASA addresses these in a recently-released animed video that covers all the basics of interstellar travel!

For the sake of this video, titled “NASA’s Guide to Near-light-speed Travel,” it is assumed that the interstellar traveler (who appears to be an alien creature) has built a spacecraft that is capable at traveling at 90% the speed of light (0.9 c).

Putting aside the question of how the spacecraft is able to reach this kind of speed, the video then moves directly to tackle the big issues that come with traveling around in a relativistic Universe. These include time dilation, the need for shielding in the interstellar medium, and how long it would take to travel to even the nearest destinations, …

2. John Healy says:

So, putting aside the question of how we might travel near the speed of light (let alone in a spacecraft able to reach 90% the speed of light), in this BackReAction blog post, physicist Sabine Hossenfelder discusses whether it is possible in principle to travel faster than light: Is there anything actually preventing us from ever developing a technology for faster than light travel?

• BackReAction > “Is faster-than-light travel possible?” (May 22, 2020).

there is nothing in Einstein’s theory that forbids a particle to move faster than light. You just don’t know how to accelerate anything to such a speed. So really Einstein did not rule out faster than light motion, he just said, no idea how to get there.

There are some gotchas: time reversal (symmetry), a consistent arrow of time, negative energy. But she concludes: “… there is no reason in principle why faster than light travel or faster than light communication is impossible. Maybe we just have not figured out how to do it.” [1]

… the conclusion depends on how seriously you take quantum theory. Personally I think quantum theory is not itself fundamental, but it is only an approximation to a better theory that has not yet been developed. The best evidence for this is the measurement problem which I talked about in an earlier video. So I think that this supposed problem with the vacuum instability comes from taking quantum mechanics too seriously.

Notes

[1] Lately, I find statements that “there is no reason in principle” to be cryptic, too unpacked, allusive mathematics. Perhaps Hossenfelder is evoking when we did not know how to travel faster than sound (and pondered all the risks) – there was nothing in principle which prevented us from doing so. But when she (and other physicists) talk about dough unmixing “in principle” and only a matter of likelihood, I ponder the line between reality and fantasy.

Our observation that forward in time is different than backward in time comes from entropy increase. It arises from the behavior of large numbers of particles together. If you have many particles together, you can still in principle reverse any particular process in time, but the reversed process will usually be extremely unlikely. Take the example of mixing dough. It’s very easy to get it mixed up and very difficult to unmix, though that is in principle possible.

Brian Greene does a lot of this “anything is possible given an infinte (unlimited) amount of time” in his latest book Until the End of Time. That is, in an essentially infinite space with infinte time, with some type of perpetually in motion granularity, that all possible combinations occur (or recur). And the fairy tale (“much ado about nothing”) of “possible spontaneous coming together of particles” into Boltzmann brains.

• YouTube > Sabine Hossenfelder > “Does nature have a minimal length?” (Feb 2, 2020) – “Is there a smallest scale beyond which nature just does not have any further structure? Does nature have a minimal length?”

(from transcript)

When physicists talk about a minimal length, they usually mean the Planck length, which is about ten to the minus thirty-five meters. The Planck length is named after Max Planck, who introduced it in 1899. … To give you an idea, think of the tunnel of the Large Hadron Collider. It’s a ring with a diameter of about 10 kilometers. The Planck length compares to the diameter of a proton as the radius of a proton to the diameter of the Large Hadron Collider. Currently, the smallest structures that we can study are about ten to the minus nineteen meters. That’s what we can do with the energies produced at the Large Hadron Collider and that is still sixteen orders of magnitude larger than the Planck length.

What’s so special about the Planck length? The Planck length seems to be setting a limit to how small a structure can be so that we can still measure it. That’s because to measure small structures, we need to compress more energy into small volumes of space. That’s basically what we do with particle accelerators. Higher energy allows us to find out what happens on shorter distances. But if you stuff too much energy into a small volume, you will make a black hole.

3. John Healy says:

In her latest YouTube channel video, Sabine Hossenfelder does an excellent job answering this question from a viewer:

I have read books on relativity by PhDs who said that we travel through time at the speed of light. … Can you let me know if this is right or if this is utter nonsense.

This video is one of her best, a polished focused example, exhibiting her tone and crisp language (and layered elucidation) and unabashed use of (some) equations to explain physics.

• YouTube > Sabine Hossenfelder > “Do we travel through time at the speed of light?” (Aug 29, 2020) – In this video I explain why it is correct to say that we all travel through time at the speed of light and just what this means.

The comments are interesting, especially regarding what being stationary entails.

4. John Healy says:

Generalizing conservation per no preferred reference frame to other physical (universal) constants besides the speed of light, in this case (below) the Planck constant.

• Science X > “Einstein’s missed opportunity to rid us of ‘spooky actions at a distance’” by W.M. Stuckey (October 12, 2020)

Length contraction and time dilation … follow as a result of this [Einstein’s] “light postulate,” i.e., the relativity principle applied to c.

One-hundred fifteen years later, we are still using his theory of special relativity without any corresponding causal mechanisms (“constructive efforts”) to account for its “universal formal principle,” i.e., the relativity principle.

That special relativity is a “principle theory” rather than a “constructive theory” is something not widely appreciated.

My take is that a constructive theory is a conceptual model – versus a mathematical formalism – which explains empirical phenomenon.

The article describes the operation of a Mermin device [which is actually based on entangled spin measurements] for which “instruction sets constitute a ‘constructive effort’ to account for the correlated … outcomes.” But such sets incorrectly predict the actual statistical correlation.

… we are in a similar position today with quantum entanglement that physicists were confronting at the turn of the 20th century with time dilation and length contraction. What we showed in our paper in Science Reports is that the relativity principle is again responsible for the mystery.

As Steven Weinberg points out, measuring spin angular momentum with Stern-Gerlach (SG) magnets constitutes the measurement of (plus or minus) “a universal constant of nature, Planck’s constant h” (Figure 2). Therefore, the relativity principle requires that no matter how you orient the SG magnets to measure the spin angular momentum of the particles, you always obtain an up or down result, never a fraction of that amount.

The red and green outcomes in the Mermin device represent these two possible outcomes. Just as one would expect to measure c + 20 miles per hour for the speed of the light pulses coming from the golf cart, one would expect (according to classical theory) to measure fractions of h at different SG magnet orientations (Figure 2).

What we showed in our paper is that the mystery of quantum entanglement represented by the one-quarter case (b) agreement in the Mermin device results necessarily from the fact that neither Alice nor Bob can measure anything other than Planck’s constant h, regardless of their SG magnet orientations relative to the source. In other words, in order to obtain the intuitive (“non-mysterious”) conservation in case (b), Alice or Bob would have to measure something “between” red and green. But, that would mean the person who measured red or green was in a “preferred reference frame” having measured the “true” value of h.

Instead, what happens in case (b) trials is that Bob’s outcomes corresponding to Alice’s outcomes for a particular setting correctly average to what one would expect for conservation of spin angular momentum (Figure 4). Of course, the situation is symmetric so that Bob can say it’s Alice’s outcomes that correctly average to what one would expect given his outcomes. Since no one can measure fractional outcomes, this “average-only” conservation is as complete a conservation of spin angular momentum as is possible.

the mystery of quantum entanglement follows from the relativity principle applied to the measurement of Planck’s constant h. … we have one and the same principle explanation of these mysteries with no corresponding constructive accounts. Thus, we now know that quantum mechanics is as complete as special relativity given its adherence to the relativity principle.

Notes

Mermin device > Nathaniel David Mermin

Nathaniel David Mermin is a solid-state physicist at Cornell University best known for the eponymous Mermin–Wagner theorem, his application of the term “boojum” to superfluidity, his textbook with Neil Ashcroft on solid-state physics, and for contributions to the foundations of quantum mechanics and quantum information science.

Mermin was the first to note how the three-particle GHZ state demonstrates that no local hidden variable theory can explain quantum correlations, and together with Asher Peres, he introduced the “magic square” proof, another demonstration that attempting to “complete” quantum mechanics with hidden variables does not work.

Constructive quantum field theory

In mathematical physics, constructive quantum field theory is the field devoted to showing that quantum theory is mathematically compatible with special relativity. This demonstration requires new mathematics, in a sense analogous to Newton developing calculus in order to understand planetary motion and classical gravity. Weak, strong, and electromagnetic forces of nature are believed to have their natural description in terms of quantum fields.

5. John Healy says:

The sci-fi book series “Three-Body Problem” is not the only (or first) drama to incorporate changes in the speed of light (in at least some parts of the universe). Cf. George Gamow’s 1939 book “Mr. Tompkins in Wonderland.”

Here’s an update on the MIT Game Lab’s 2012 “A Slower Speed of Light” video game.

There’s some explanation of length contraction complicated by the runtime effect.

• Space.com > “What would happen if the speed of light was much lower?” by Ashley P. Taylor (November 1, 2021)

(quote) In reality, the speed of light would not slow down the way it does in the game. The speed of light in a vacuum never changes and is constant for every observer. However, the speed of light does change depending on the materials it’s passing through, but that doesn’t change the effects of special relativity, or how we perceive them, Kortemeyer said.

If we could witness special relativity, however, we would notice changes in colors, time, distance and brightness, and the team incorporated those effects into the game.