The “space-time continuum” is one of the concepts that came out of relativity theory that most people have heard of, but do not fully understand, like the related formula E=mc2. Science articles maintain an awareness of both, but science fiction and resulting memes do more to keep each in people’s consciousness. Alas, spacetime is considerably harder to grasp than Einstein’s famous equation, but that doesn’t mean it has to be treated as incomprehensible to anyone without a physics degree.

In *Life, the Universe and Everything*

In one sense the idea is simple – instead of there being three dimensions of space, with time being something completely different, spacetime is a four-dimensional thing. Events are represented in spacetime by four coordinates: three based on where something occurs, relative to a defined point of origin, and the fourth being the time at which it happens.

Although Einstein made the concept of spacetime essential through relativity theory, physicists had been toying with the idea of a unified spacetime in which time was treated as a fourth dimension for some years before, including

The problem most people have with this is that we experience time so completely differently from length, width, and height that the whole thing seems ridiculous. If, for example, we realize we have come too far in a particular direction, we can usually turn around and go back. We wish the same were true for time. Ursula Le Guin

Physicists struggle to explain why

Under the conditions we experience in our everyday lives, treating space and time as separate isn’t a problem, which is why the idea of spacetime is so counterintuitive. However, if we were traveling at close to the speed of light relative to something important to us, the situation would be very different.

A key feature of Special Relativity is that time slows down when traveling close to the speed of light as compared to the experience of a stationary observer. Likewise, at near lightspeed, space becomes contracted in the direction of motion. This means that if someone traveling very fast were to measure two events and compare their results with someone moving slower, they’d get different separations in both space and time. However, using the speed of light to convert between units of space and time, both observers measure the same spacetime distance (assuming they’re measuring accurately).

Moreover, this space-time continuum can be distorted, for example by powerful gravitational forces that affect time as much as they ** **comparing clocks in orbit with those on the Earth.

Measurements of the movements of massive objects, such as pulsars, around each other confirm the predictions of General Relativity regarding the workings of spacetime with

Nevertheless, the existence of these competing theories is a reflection on the fact that, while we know the space-time continuum exists, there’s a lot we don’t understand about it. Physicists’ inability to reconcile General Relativity and quantum mechanics has been a sore point for decades. Many have suggested that