Time is perhaps the most out-of-reach aspect of our everyday reality. The reason is simple: unlike most obvious aspects of our shared reality, this one hides in plain sight. The traditional view looks at it this way: for any object to move or change its position relative to something, it requires two things, space and time; without either, movement is not possible. However as mentioned previously, space is taken for granted and we will not be discussing “spacetime” as being one and the same as it can be misleading.
Mass and Time Dilation
For any object to have time dilation and persist within space, it needs mass, and it needs lots of it. There are two concepts within physics known as T = 0, and the other known as Tmax; however, when looked at closely, they are actually the same thing. The key difference from how physics frames it is this: an object with mass carries its own time dilation with it—it is intrinsic to the object, not something spacetime imposes on it. The universe simply provides a baseline and does not interfere. Time dilation itself becomes a differential based on mass.
For our thought experiment, let us step outside of our Milky Way galaxy and find ourselves a patch of empty space—not true vacuum, just a patch of space. Now in here T = 0 will be the baseline. Physics assumes it will be Tmax here, which is a fancy way of saying everything will be sped up. But let us keep going with the thought experiment: let us say a rogue planet like Jupiter comes along into this patch of empty space. Now T = 0 is like a sea that refuses no river. That rogue planet that is coming along has its own mass and time dilation effects with it. This patch of space will let the rogue planet pass without any resistance whatsoever. Now that the rogue planet has gone away, let us place a pea here. Now as you know, a small pea will not have that much mass. In this space, only its entropy rate will shoot up to extreme, and it will disintegrate, and the space will return to baseline of T = 0.
Stars and Time Dilation
The more mass a star has, the more time dilation there will be; here it will imply slight slowness of time, the more mass the object has. Stars like our Sun are called G-type main-sequence stars, where active phases can last up to 10 billion years;1 after this phase, the remnant white dwarf star would persist for much longer. Let us look at another star: Betelgeuse, in the constellation of Orion, is much larger than our Sun and has a mass of about 15–20 Suns.2 Stars like Betelgeuse have an active phase that can last somewhere between 8 to 10 million years or more, which is less than our own Sun. But their second phase can last much longer, be it a white dwarf or a neutron star. So, say if Betelgeuse has a hypothetical habitable planet nearby, the time recorded there will be a teensy bit slower than Earth.
Larger stars, which can leave behind stellar mass of more than 3 solar masses,3 are candidates for becoming a “black hole”—however, I prefer the word “black shell”, a shell which pulls at c because this shell is significantly smaller than either the original star or its remnant. And you know what will happen to any baryonic matter that is pulled at c? It will simply freeze, until stripped of energy completely. So, the time being experienced here? It is T = 0 because of the immense gravity—no solids allowed.
The rules of the game near an object like a black hole are simple:
Slower, slower you are the closer you are, the closer you are
Halt, halt, if you have hit the vault (shell pulling at c)
So it seems that time becomes a differential between T = 0 of space, which serves as baseline for everything that comes its way, and on the other end we also have T = 0, but no entry is allowed there.
Experience of Time vs Time Dilation
Experience or passage of time is for sentient beings, like humans and other beautiful animals, insects, and perhaps even trees. It is because living beings and their movements are goal-oriented, so time becomes an important factor for living, unlike stars or galaxies—they are only here for a blink of an eye when, say, you look at the phases of a star. But even still, perhaps it is the most precious thing in the universe. This experience of time will not differ much whether you are here on Earth, near Betelgeuse, or even at a safe distance from a black hole. The experience of time is a subjective experience: when we are bored, it feels as if time has slowed down, while on the other hand, when you are deeply engaged with something, it becomes really fast, and some also get to experience T = 0, where individuals lose all sense of time in a state of mind called “flow”, which can happen in deeply engaging activities like knitting.4,5
On the other hand, inanimate objects like stones, stars, planets, and asteroids do not have experience of time, but they certainly do have time dilation. For such objects, an instant and an eternity are one and the same, because there is no passage of time. However, when we observers look at such objects, we can certainly marvel at their extremely long periods in which they sustain their structure and become a source of life.
Lastly, there is the peculiar case of light: does a photon experience time? Or, if a photon is travelling at c and T = 0, how is it really able to travel? Physics does not have a straightforward answer for this. My own assumption is that a photon does not travel through space; instead, it is a quantum particle which exists in a probability of two states—as a photon and as a wave, also known as wave-particle duality,6 and these states dictate its quantum position from voxel to voxel in space, and our primitive eyes and perception see it “travel”, while perhaps it is not really travelling but simply being in an excited state of +1/−1. It is a dance of parallels, a cosmic ballet to the eternity of ever-changing quantum states.
