An Einsteinian thought experiment about transport

Let’s remember how useful it can be to ask new questions, remembering how Albert Einstein asked himself questions that led to his discovery of the special and general theories of relativity.[1]
Are there not many questions we need to be asking about how to organise our transport — our systems and modes of transport? Our current system — globally — is massively destructive, killing millions every year, [2, 3] maiming tens of millions, [2, 3] and is a leading cause of catastrophic global warming. [4] That is just the start of the list: it also destroys space and natural life, kills tens of millions of animals every year, [5] pollutes air, water and land, requires gigantic money costs, etc. We ought to change our transport system. How?
Well, how can we think about transport? For example, what goals do we want to solve with transport? Simply put: where do we want transport to take us? Maybe there is an interesting physical relation to consider, and this brings us to a kind of Einsteinian thought experiment.
An Einsteinian thought experiment. Imagine, for example, a transport, like a jet-pack, that enables people to move in all directions at infinite speed. Then no one can move or even stand safely anywhere! One person on a jet pack — moving at infinite speed in any direction, prevents any other person from being safe wherever they may be.
That is to say, some people travelling fast and freely (e.g. by car) means that others are limited, in their ability to move or even stand anywhere! The Einsteinian thought-experiment leads to the idea that: One body moving more means other bodies must move less. I.e. when one body moves extremely fast in a range of directions, other bodies must limit their freedom of movement (speed / direction). There is a safety limit in terms of vector/speed.
This form or equation of the physical relation can describe the problems of cars, that combine (with roads) many vectors and high speed, and therefore, limit the speed/vector for other persons or bodies.
Let me try to apply this general relation to ordinary examples: A child playing in the street, is at danger when other objects/persons travel in that space at injurious speeds. The child’s range of movement (speed and vector), e.g. just bouncing a ball around, or painting on the pavement, is limited by these other moving bodies, to the extent that the child simply cannot play in the street safely. This is amazing: even extremely modest/limited movement by a child in the street is obviated (made impossible) by much more expansive (high speed/large vector range) movement by other objects. We see this historically in our societies, as children’s freedoms of movement have become extremely limited, by the spread of the car, for example, but really it is any high-speed/high-vector moving object (even a bicycle, I’m sad to have to say).
Gravity is an invisible force; and maybe what we’re working with in understanding the physical relationships of transport is also invisible, to some extent.
– The effective sphere for the imaginary jet pack I described is gigantic; as a result, the effective sphere for all other bodies (that are vulnerable to that jet-pack) shrinks to near-zero, or even zero (there is no safe place at all!).
– The effective sphere for a car-user is large — the car-user can move at high speeds along many vectors. As a result, the effective sphere for bodies that are vulnerable to the car, shrinks.
How can we use this physical relation understanding?
Movement is relative! One fast moving body means that other bodies must move slower or not at all — if they share space!
Vectors are important! If bodies don’t move in the same space (i.e. along the same vectors), then the relation is not so large. A mundane example: segregating bicycle traffic from pedestrians enables higher speed for bicyclists, and more speed/vector range for pedestrians.
We need to consider all movement in our world: it’s not just human beings who need to move around! Animals, birds, i.e. non-human life also needs to move around. And non-animate nature needs to move around too: water, for example, as considering the hydrological cycle confirms. Consider a situation where a human transport system destroyed the hydrological cycle (the movement/cycling of water through various stages and phases): it wouldn’t last long!
Walking is amazing! Perhaps the relational idea about movement helps us understand yet again (from a new standpoint) why walking is so amazingly good, and beneficial! Well, at the slower speeds of walking, one can preserve more vectors of movement. Walking down a city street, one can do a million things (and one preserves others’ freedoms also). Driving fast down that street, one cannot do much; and one limits others too. A city street only for walking (as transport) enables millions of activities — is “convivial”, lively, etc. A city street designed for moving at high speed, disables.
At a global level, we can see that new questions arise: what forms of movement (human, non-human, non-animate), are important, necessary, sacred?
Car-free is better:
(1) Given a certain amount of space, like a town of 10 km diameter, the freedom of movement is far greater without the car than with the car. The space is usable in more ways.
(2) When distances expand, and people wish to accomplish those distances rapidly, then the range of transport vectors should be limited. High-speed rail is an example of an extremely limited vector range (only the track), and so it can travel at high speeds, over large distances, without much impact on other people’s freedoms of movement. (Japan’s elevated high-speed rail tracks take it to another level!)
(3) In a sense, the car is our world’s real version of the imaginary jet-pack that I described above. It’s a technology for a person to “enjoy” transport at high speeds on a wide range of vectors. The results are there for everybody to see: the range (or freedom) of movement for others shrinks.
Cars have other wasteful/destructive qualities: among them, they have a very low density of passengers, relative to other forms of transport, like walking, cycling, buses and trains. One could have a car-free city of 50 km diameter, with high-speed motorised transport (bus, train), and be fairly safe, if the motorised transport forms were extremely segregated from other bodies.
[1] A nice summary of these processes of asking interesting questions by Albert Einstein is provided by the book from White and Gribbin, Albert Einstein, A life in science. (preview available here)
[2]  WHO (World Health Organization), Global status report on road safety, 2009,
[3] WHO (World Health Organization), The global burden of disease: 2004 update,
[4] “In 2004, transport was responsible for 23% of world energy-related GHG emissions with about three quarters coming from road vehicles. Over the past decade, transport’s GHG emissions have increased at a faster rate than any other energy using sector (high agreement, much evidence).” a quote from p. 325, of IPCC, 2007, “Transport and its infrastructure”, chapter 5 of the Fourth Assessment Report, Climate Change 2007: Mitigation of Climate Change.
[5] One million animals killed every week globally was the figure cited in Natural Capitalism, the 1994 book by Paul Hawken, Amory Lovins and L. Hunter Lovins. The book is available free here:

This article was originally published on the blog of Aaron Thomas:
thank you for allowing us to publish this interesting post.

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