Yeah its the GREATEST pbs series on youtube. You should absolutely go check it out!

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Seriously though let me give an ELI5 response. Space and time are so interconnected that we refer to them as Spacetime. What we've actually observed and tested is that the more you move through one, the less you move through another.

Let's imagine an extremely simplified "spacial dimension" where you can only move in one direction. Let's also imagine time as a spatial dimension as well, for simplicities sake.

Imagine that whenever you move "North" you are moving 100% through space and 0% through time. Now imagine you turn 90 degrees to the right and go East, you are moving 100% through time and 0% through space.

Whenever you want to move, you have to move some combination between "Space" and "Time". The faster you move (through space) the less you move through time. The closer you are to a heavy object the less you move through time as well (this is for a MUCH more complicated reason, but again related to "spacetime"), but whenever a massive object warps space, it also warps time.

We know this to be true, because our satellites orbiting the Earth must be INCREDIBLY accurate and precise. So much so that our programming has to account for the time dilation that occurs (us on Earth experiencing time differently than the Satellites in space do).

Essentially the two things are so connected, that we believe they are a single thing.

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Its a pretty dense topic but here are videos on spacetime, from spacetime!

How Does Gravity Warp the Flow of Time?

Does Time Cause Gravity?

When Time Breaks Down

Spacetime is a concept on which space and time are connected as an intrinsic property. Especially when considering that you have an absolute constant, which is the speed of light, you can always convert one to the other. We measure distances in light years for that reason. But it goes deeper.

You can bend space, weird huh… not in the same manner that one might consider bending of a rod, but the general analogy which, though not perfect, works for many people, is putting a ball in the middle of a taught sheet of cloth. The sheet will sag in a certain way towards it, bending it. The thing is if you bend space you also bend time, in extremes, such as the proximity of black holes, time dilates, and to an outside observer looking at you it looks like you’re in slow motion.

I think about it this way as a layman: You cannot move through space without an element of time. It is impossible to move from point a to point b without time elapsing. So space and time are inextricably intertwined.

Maybe oversimplified and please correct me if I'm wrong. But that's how my brain understands it.

The best I can explain is to describe a black hole, because of the objects density it warps space, but space is not just empty nothingness, it has fundamental properties of the 3 dimensions we're familiar with but in addition to this black holes also warp time around them causing time to pass by slower the closer one gets to the event horizon. An outside observer would not experience this time dilation so years would pass for them whereas if you journeyed around a black hole potentially only hours would pass for you and this is because time is inseparable from space itself. Matter tells spacetime how to bend and spacetime tells matter how to move.

As I understand it: Think of spacetime as a fabric that covers the entire universe. When the fabric is warped by objects with mass, time is warped as well. Like if you put a bowling ball on a bedsheet and it made a divot — that’s sort of analogous to how gravity works, but the key point is that warping ALSO affects time. Where gravity is stronger (eg closer to the center of the bowling ball) means time is slowed further, and infinite density at a point (a singularity in a black hole) causes a “rip” in the fabric that makes time infinite (as perceived by an outside observer) for someone who crosses the event horizon of a black hole. Nobody knows what would happen inside.

If you’re interested in this and want a book that explains it clearly, try The Order of Time by Carlo Rovelli.

In the theory of relativity, spacetime is a mathematical concept that combines space and time into a single framework for understanding the physical universe. According to this theory, the three dimensions of space and the one dimension of time are not separate and distinct, but are instead closely intertwined and cannot be understood independently of one another. In other words, spacetime is a four-dimensional structure that describes the way that objects move and interact in the universe. One way to think about spacetime is to imagine it as a fabric that is stretched out in all directions. The positions and movements of objects in the universe can be thought of as points or lines on this fabric. The fabric itself is not made up of matter, but rather it is a framework that provides the structure for the matter and energy that exist within it.

Consider that to pass or travel through space, it takes you time. Space and time are intertwined in that way. The only way around that would require manipulating space-time, which is everything around us.

We are all objects existing in spacetime. Objects with mass interact with space time, and these interactions are observed as gravity. More mass = more interaction with space time = more observed gravitational force

Space IS time. It's a headf**k but it's true. If you're a lightyear away from something, you are a year away from it in time.

A great visual analogy that I once saw, was to place a light beam between two mirrors, perfectly balanced. Now start to move the mirrors. The beam of light has to travel further and further in order to reach the mirror above or below it. You can see that as the mirrors approach the speed of light the beam would seem to be suspended.

>Can someone explain what spacetime is?

Honestly? No. No one can. We can model it very accurately, but we don't really know what it is.

>Also does "one dimension of time" imply that there are multiple dimensions of time?

An easy explanation is, imagine I ask you "Meet me in the conference room on the 3rd floor of the building at 1st street and Main Street."

That room has three coordinates in space, X Y and Z, that you must traverse from your current position to arrive at. However, if we want to meet there, you also need a time coordinate. We also traverse from our current time to subsequent times, or at least, that's what we experience. Thus, we'd arrange our meeting with four coordinates, X Y Z and t.

Time is just how we measure changes in the spacial dimensions we observe. No time? No change. Hence, Spacetime. Without time, space would never have changed state to begin with, and everything would still be at a singular infinitely small point without space, as we theorize a pre-big bang universe would be. At that point all I can imagine is quantum indeterminacy spontaneously manifesting a universe from nothing.

In my opinion (assuming the variables eventually add up) the net total energy of our universe is zero. What that really means is the cosmos and all the spacetime therein, is zero energy. From the outside looking in (if there were such a thing) there's absolutely nothing here. There isn't even a here at all. It's something the photons emitted at the beginning of our universe that will get absorbed at the end of our universe experience. Time doesn't pass for a photon, so from its perspective, nothing is here, nothing has happened, is happening, or ever will happen. The beginning and the end are the same instant.

Maybe I went a bit too existential with this question, but the honest answer is we have not the faintest idea what spacetime actually is. Functionally, it's just the name we've given the model we use. I'm good with that. It's a solid model, that only breaks down under such extreme mass conditions, you'd need to observe the inside of a super massive black hole to figure out a better model.

Time is relative, and passing through space at different velocities warps time. Peering deeper into space is also peering further into time. Every physics equation and observation must account for all four dimensions. Since they are so intricately tied together, and dependent upon each other, astro-physicists speak of Space-Time.

All we know, all we can ever know, the entire universe is contained within Space-Time. Anything speculatively beyond that is outside of our existence.

movement through space and time are inversely connected, the faster you move through one the slower you move through the other. at 99% c you experience time very slow, but to experience time at full speed you have to be moving very slowly. This is all relative between objects because there is no mathematical 0,0,0 point we can anchor ourselves to in a universe where everything is moving. not experienced with this at all so definitely tell me if i'm wrong

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Think of Space as a stage on which all things take place now adding time as dimension means we can see what happens to this in different instances of time like say the present as the base line the future and the past in opposite directions now what Einestien discovered is that when things go through this space time they experience the world differently so someone can have 3 years pass for them and others 6 years or someone can run 3 metres from one perspective but only 1 and a half from thier own. Additionaly the space time stage can be molded or changed depending on how many things are in it making a further difference in how different perspectives see the world. There is no limit to how many dimensions of time you take humans can only observe one in which the past and future exist but there can be more just not ones we know anything of.

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You can swap time and space. So if you go a long distance and your friend stays still, they will experience the time and you will experience the distance. That means, for them it will have been 100 years and no space, and for you it will have been 100 billion miles of space and 1 year.

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Einstein's General Theory of Relativity shows that time is a physical thing. It is part of space-tme. Space-time manifests itself as a gravitational field created by the mass of objects. The presence of mass will warp, or deform, space-time. As a consequence, time passes more slowly near to a massive object such as a planet. This has been demonstrated to be true by comparing super-accurate clocks in orbit to clocks on the surface of the Earth. The clocks on the surface run just a little bit slower. (This is a paraphrase from other people's explanations)

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Im no scientitian, but think of it like if you're standing somewhere. You are at a certain point of space at certain point of time.

The fourth dimension allows for change to occur in the three former spatial dimensions. This is spacetime.

Remember Isaac Newton? Newton is responsible for large portions of the the physics that is really useful in our day-to-day lives. For example, Newton's laws of motion offer a foundation upon which we can understand inertia, the relationship between force and acceleration, and how two objects will interact with each other if one hits the other.

The formulas that Newton (and others) developed are still used today in many fields, and all of this math treats space and time separately. We call this classical physics. So why do we need space-time at all if these formulas work for so many day-to-day applications?

As velocity increases, the formulas used in classical physics start to become inaccurate. This happens because our physical world is not absolute, but relative. Without considering these relativistic effects, the calculations made using Newtonian physics result in errors.

The new formulas developed as part of relativistic physics lead to the coupling of space & time as a way to make the calculations for accurate measurements and predictions easier.

If you have a few minutes, there are two short videos available from TED-Ed that explain space-time using simple animations. Their explanation is very accessible, and is broken down into 5 minute segments.

Part 1: https://www.youtube.com/watch?v=ScdLqAA_64E

Part 2: https://www.youtube.com/watch?v=aeCsS6PjhK8

Part 3: https://www.youtube.com/watch?v=NAXHHBUY9_E

Let’s say I have a frictionless ball, I drop the ball and it bounces back to my hand exactly into its original position (because it is frictionless). However me and the ball are on Earth, which is rotating and which orbits the Sun, so me and the ball have actually moved significantly from where we were when I dropped the ball. You can go even further than this and think about how the Solar system moves through the Milky Way, which itself is also moving etc. So did the ball bounce back to its original position? You might say no, but that’s only because you have other objects as a reference point, if you could not see them you would have no idea.

The point is there is no absolute space. You can’t describe a point in space without also describing a point in time (or another object, but then it has the same issue of needing its own time coordinate or another relative object, then the issue repeats). The same goes for describing a point in time without describing a point in space, although this is harder to grasp.

We actually already think like this in our day to day lives, in fact humans are very unique for thinking this way. For example, do you show up at work simply at a specific place? Or do you show up for work at a specific place, and at a specific time?

Space and Time: Let us meet in Time Square (New York City, USA) at 1200UTC.

It is the simplest set of spacetime continuum coordinates. Omitting space or time, you miss a date ;)

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Here's the simplist, most practical way to visualize the theory. You're in a conversation with a close, but very dense relative. Notice the way time slows to a standstill? That's relativity.

There’s a really good explanation of the twelve dimensions of reality on YouTube, trying to make sense of the relativity and reality. I can’t find it right now due to bandwidth issues but you can search around and find it.

Hello u/Dusthip, your submission "Can someone explain what spacetime is?" has been removed from r/space because:

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You really hate to see “spacetime” reduced to a coordinate system like that. Imagine if you will a taut bed-sheet suspended in air by its four corners. You can think of each point of each fiber of that sheet as you classic xyz coordinate plane and the whole sheet stitched together as xyz-t incorporating time. The real revolutionary thing about this is that spacetime as the fabric of space interacts with matter creating the effect of gravity. Balls of mass sitting on the sheet locally deform the entire sheet causing anything sitting on that sheet to “fall” toward it. The bigger the mass the bigger the effect. It also shows how the effect can be universal (all mass is attracted to other mass) but the magnitude of this attraction is a function of the magnitude of the deformation and another mass’s distance to the deformation. It is one of the non purely math only explanations of what a “force” is.

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When you look at the night sky, you see a spacetime mosaic. All of the photons (light) reaching your eye come from different time periods. If that star is 40ly away then the light you see took 40 years to arrive st your eye. The star right next to it is 400ly distant and those photons have been traveling 400 years. A representation of spacetime.

You’re going to want to read a book. If you ever want to understand this or anything else.

For this, maybe two books and a lot of math.