What does it mean to say that space has three dimensions? It means that space has directions that have three dimensions, that is, three degrees of freedom. The dimensions are the directions in the space. It’s not that there are some dimensions that are spatial and others are something else but that space is characterized […]
Speed can be zero, that is, the change in spatial position per unit of duration can be zero. Can the change in temporal position per unit of length be zero, too? Let’s see. First, the denominator cannot be zero. We cannot simply invert a zero speed because that would lead to a zero denominator, which
Marcus Aurelius wrote, “Time is like a river made up of the events which happen, and a violent stream; for as soon as a thing has been seen, it is carried away, and another comes in its place, and this will be carried away too.” Time flows, and keeps flowing day and night, whether anything
This post is a companion with the post “Is space one-dimensional?“. As we can compare the alleged one-dimensionality of time with how we think about space, so we can compare the three-dimensionality of space with how we think about time. In both cases the comparison is instructional. Space and time are parallel in both cases
While the answer is No, space is three-dimensional, it is instructional to compare space with time as people speak about it. The philosopher JME McTaggart made a well-known distinction between an A-series, which is “the series of positions [in time] running from the far past through the near past to the present, and then from the present to the
Consider a worldline in one dimension of space and one dimension of time that tracks the position of a point that moves from position 20 to 10 to 15. This could represent the movement of a point in the E-W dimension. Another worldline could track the movement of the same point in the N-S dimension. All would agree
If we drop a stone into a calm body of water, it sends out circular waves. As the waves move outward, the clock is ticking and we say the dropped stone caused the waves, which are an irreversible process in time. But we would also say the waves are moving in space, so why isn’t
This is a continuation of the series of posts on the duality of space and time. Consider an isolated system of particles over a period of time. The system covers a specific distance in space and a specific duration in time. Consider only one dimension of space and one dimension of time with an origin point. The second
As (spatial) velocity and acceleration are vectors, so are their temporal analogues. This perspective makes sense because of the multiple dimensions of time. There is an implicit recognition that time has directionality since time is commonly considered as any real number, and not a non-negative real number, which it would be if time were merely
The speed of an object is the ratio of distance (or length) traveled and the duration of travel. It is derived from the distance traveled during a given duration. It is expressed as the measured distance divided by the given duration, that is, distance relative to duration in units of distance over duration, e.g., m/s, km/hr, etc. For example,
