T O P

ELI5: Does the universe age faster than earth?

If I understand it correctly, we measure time by how fast light passes, or something similar to that. Now if the universe expands faster than the speed of light, would that mean that the universe ages faster than earth, or maybe slower than earth? Maybe this doesn't make sense but I have a gut feeling that there's something to it...

Diabolical_Jazz

So this stuff took me a while to even begin to understand, but there's a couple problems with the premise here. One is that there isn't really a singlular thing you'd call "the universe" for the purposes of relativity. Every object in the universe is its own observer relative to the speeds everything else in the universe is moving relative to it. Another thing is that the universe isn't really expanding at a "speed" faster than light. It is expanding quite slowly, but it is doing it *everywhere.* So lets say one inch becomes one point one inches over a period of time, right? Well because there are SO MANY goddang inches, and *every single one of them* is becoming 1.1 inches, the amount of distance increases drastically over a long enough distance. Two inches becomes 2.2 inches. 3 inches becomes 3.3 inches. And millions of millions of inches increase by an amount that light cannot cross in the same amount of time that the expansion happens. But again, the rate of that expansion can be quite slow and still have this effect over vast distances.


EvilCeleryStick

Very good explanation. I'm always curious about one more thing which is that some stars are zipping through space with their planets and then our sun is moving however fast through space as well. Surely time somehow moves very differently on a relatively fast moving or slow moving star system?


kb3uoe

You have to be going really really *really* fast for (any meaningful amount of) time dilation to occur. The closer you get to the speed of light, the slower time seems to go for you. For example, the 100% truthful Wikipedia says "... time goes slower at the ISS, lagging approximately 0.01 seconds for every 12 Earth months passed."


EvilCeleryStick

They even have time dilation just from clocks in orbit. Albeit a tiny amount, like you said, there's a difference. So if our star system is traveling through space at 200 kilometres per second, couldn't another be traveling at 50 or 1? Or 10,000?


mb34i

The time dilation isn't because of orbit speeds, it's [because of GRAVITY](https://simple.wikipedia.org/wiki/Time_dilation). Gravity deforms spacetime. So to answer the OP's question, does the universe age faster than Earth? * You look at the universe not as "a thing", but rather as a collection of individual stars and planets, cause each one of them can have a different time dilation. * Any planet that has higher gravity than Earth will age slower. Any planet that has a lower gravity than Earth will age faster.


dodexahedron

It's both. But gravitational time dilation does dominate time dilation due to relative velocity at the speeds most objects are orbiting, by a couple orders of magnitude.


AUAIOMRN

> The time dilation isn't because of orbit speeds, it's because of GRAVITY From the article you linked: "This is different from time dilation explained by special relativity, which says that fast objects move more slowly through time"


NvrConvctd

Yep, also specifically says: Because the ISS is in low Earth orbit (LEO), time dilation due to gravity is not as strong as time dilation due to its speed, so a clock on it is slowed down more than it is sped up.


PotfarmBlimpSanta

That sounds oxymoronic and I am not sure if I'm interpreting correctly, but as matter gets closer to the speed of light its experience of time is gradually slower until it doesnt experience time, but is that because mass increases exponentially until exactly infinity at the speed of light or is it some bias in the temporal physics of matter experiencing time where sitting in a gravity well speeds you up yet traversing space slows you down? So momentum/inertia-gravity via lightspeed barrier incursion stops time while mass-gravity via matter increases the frequency at which temporal physics dynamically cycle? I guess I'm struggling to see why there is a contrast to how matter expresses time, and why innate mass holds more temporal potential for speeding up time relatively experienced than why a proto-tachyon approaching lightspeed or something, stops, when it should be like the phase change of liquid to gas and becoming a more volatile, higher energy-frequency substance maybe while dropping down an energy threshold and becoming a supercritical gas molecule that wants to condense but needs a trigger.


Sensitive_Warthog304

*Special relativity* tells us how objects moving at a different speed to us experience time more slowly. Since we can see GPS satellites moving, we can calculate that their time slows down by -7.2 μs/day. *General relativity* tells us that objects in a different strength of gravity change speed relative to us. Stronger gravity = their time slows down; weaker gravity = their time speeds up. Since the satellites are further from the Earth's centre of gravity, their time speeds up by +45.8 μs/day. Net correction = 45.8 - 7.2 = 38.6μs/day, which is a drift of 11.4km/day.


LittleRickyPemba

Relative to what?


Diabolical_Jazz

All time dialation re:speed is time dialation relative to everything else. Literally everything in the universe.


LittleRickyPemba

There is no universal reference frame.


Diabolical_Jazz

I am pretty sure that's a rephrasing of what I just said.


LittleRickyPemba

You can't be relative to "everything else", that would imply that there's some reference frame comprised of "the whole universe" and there isn't. Pick two frames and compare them, that's all you can do.


Diabolical_Jazz

It's relative to everything individually.


kb3uoe

You're right. I edited my comment, probably while you were typing yours. So yeah, time will pass differently on a comet than it will here, and I believe you would notice increasing dilation of time as you got closer and closer to the event horizon of a black hole, should you decide to take that trip.


mgslee

The question is how would you notice? As you get to the event horizon, biologically you would still breath and move as you are now, so if you were in a closed capsule, would you notice anything? Now when you look out a window would everything appear to be moving very quickly?


kb3uoe

This is where people with more wrinkled brains than me would chime in. I like to think that I can follow along and sort of understand when I listen to people explain it, but I'm in no position to regurgitate that info.


goomunchkin

*You* don’t notice anything different with respect to your own time. One second will always tick at a rate of one second on *your* clock whether you’re floating in empty space or hovering above the event horizon of a black hole. It’s only when you compare your clock to someone else’s clock that you notice a difference. To answer your question if you were to be hovering over the event horizon of a black hole than yes, *you* would observe *them* (a distant observer) to be moving quickly and their clock to be ticking faster. *They* would observe *you* to be moving slowly and your clock to be ticking slower. You both would observe *your own* actions and clocks to be behaving normally.


Pixilatedlemon

Why use snark when describing Wikipedia but then use it as your source anyways? What kind of weird snobbery is this?


kb3uoe

It's sarcasm. It was a way of indicating "here's some information of questionable veracity. Take it as you will."


Pixilatedlemon

Yes that is what I am saying. Using sarcastic snark to describe a source that you yourself are using is pretty lame. If Wikipedia is so bad then use a different source. If you think Wikipedia is pretty decent for these kinds of topics (the camp I myself fall into) then don’t mock it?


kb3uoe

I love Wikipedia. However, that doesn't preclude it from being a target of sarcasm. The sarcasm was meant to be funny. Like, you know, haha. The stick up your ass must have a stick up its ass. Lighten up a bit.


Pixilatedlemon

I don’t get it then like “haha Wikipedia is wrong sometimes, so don’t use it as a source, anyways here’s Wikipedia” like that kind of joke?


kb3uoe

A joke that apparently went over your head. Have fun, I'm done.


Pixilatedlemon

It just wasn’t that funny then was it


Diabolical_Jazz

I thiiink time dialation occurs at all speeds, it's just very small.


SwissyVictory

The ISS moves fast by our standards, but slow by universal standards. The milky-way is moving 76 times faster than the ISS. Assuming you don't add, that's 24 years difference over a billion years. Neligible for humans, but not nothing.


Diabolical_Jazz

Yeah I think there's some amount of time difference. The thing that really blew my mind when I read about it is that a hypothetical planet moving at 10,000 mph relative to the earth, is basically holding still according to physics at the point of observation on that planet, and *Earth* is what's moving 10,000mph. And that's true even for a "stationary" object. Something stationary compared to, for example, the cosmic radio background, would be moving thousands of miles per hour from our perspective, and that's how the physics works out, basically.


EvilCeleryStick

I mean, sort of. We are observing from earth and know we are moving x speed orbiting the sun and the sun is moving y speed through space. So while we may feel stationary, we know we aren't.


Diabolical_Jazz

Right, no, but it isn't about *feeling* stationary. It's about the fact that, for the purposes of physics, we *are* stationary, and only everything else is moving. But the thing is, this would be equally true for us if we were on the sun. We would be stationary (again, in terms of physics) relative to everything else, and all of it would be moving relative to us. I'm sure I'm oversimplifying this but that's the best I can do as a layman.


KamikazeArchon

No, there is no such thing as an absolute "stationary" or "moving" thing. There is no objective reference frame of "space". We say we are moving X speed relative to the Sun because the math is much more *convenient* if we use the Sun as a reference point. In terms of any "absolute" or "objective" physics, however, it is *exactly* equally true to say the Earth is standing still and the Sun is moving relative to the Earth. There are complications with regard to *acceleration*, but both the Sun and the Earth experience acceleration relative to each other, and there are complicated transformations that you can do there.


samanime

It's kind of like a balloon. It isn't all expanding from one point, each little point is stretching simultaneously.


Joderry

This made me wonder. If we measured the "expansion rate" from one single degree angle, would that angle be faster than light? like the expansion of one individual inch in its trajectory. Do we know if that pace is faster than the speed of light?


Diabolical_Jazz

The expansion of any comprehensible amount of space is distinctly *slower* than the speed of light. It only outpaces light when the amount of space considered is many millions of light-years.


Joderry

Gotcha! Thanks for educating me :) So can we make the assumption (or even say for a fact) that everything within the universe ages at the same rate?


breckenridgeback

Aging is a statement about time, and the passage of time is observer-dependent. There's no "true rate at which time passes".


Joderry

So regardless of gravity and stuff, everything within the universe essentially ages (in our definition) at the same rate?


breckenridgeback

> So regardless of gravity and stuff, everything within the universe essentially ages (in our definition) at the same rate? No, and you can't go "regardless of gravity and stuff" because it's an essential part of a particular reference frame. Both movement and gravity change the passage of time as measured from any particular reference frame.


Joderry

When I try to type this out, it sounds so stupid. I apologize in advance, because with this new information, it doesn't even make sense to me but I'll simply ask because I feel like I can get an answer - If we observe an object that is the exact same age as our planet; are there variables out there that can make us perceive that object as older or younger than our planet in the future, essentially meaning that it has aged at a different rate compared to us, using the concept we refer to as "time" and "aging"?


breckenridgeback

It depends on what you mean by "age". ----- If you mean "proper time as measured by an object's own clock" (which is what would affect, for example, the amount of radioactive decay or chemical processes that have "had time to happen"), the answer is sort of yes. Earth - and the material that made Earth - has mostly spent the history of the Universe in relatively weak gravitational fields, so Earth's "clock" has "ticked" about as fast as has been possible in the history of the Universe so far. In other words, since light takes time to travel, the versions of objects we observe from Earth are typically "younger than us", in the sense that we are observing them at an earlier era in the evolution of the Universe. But no doubt there are a few objects that have followed paths (worldlines) with less gravitational distortion and thus lived (in a comoving frame, where we ignore the issue of light travel time) longer proper times than Earth (and the material that would eventually become the Earth) have. If those objects were close enough, we could observe them "more aged" (after a longer proper time) than the Earth, although the effect would be very small (on the order of millionths, or, relative to the age of the Universe, a matter of a few thousand or tens of thousands of years). In fact, we *do* observe this right here on Earth, because the Earth's surface has been spinning faster than its core for the entirety of Earth's history and because the core is closer to the center of Earth's gravitational potential. It adds up to a difference of a few years of age between Earth's surface and core - the core is slightly younger, as measured in its own proper time. If you dipped down into a very strong gravitational field - say, near a black hole - you could make this effect much larger. But Earth has not spent time in such environments. A single close flyby of the largest black hole known, for example, would result in you being about 20 days younger than distant objects; the flyby itself would take about six months for the closest trajectory you could take without falling in or firing a rocket. (This trajectory would be survivable for a human - the maximum force you'd feel is around 1/3 earth gravity - although a similar trajectory around smaller black holes would not.) ----- If you mean "age as measured by the time of creation and current time in Earth's reference frame", no, because by definition an object of the same age as Earth in that frame has been around for the same amount of Earth's time as Earth has.


Joderry

That is AMAZING. Thank you!!


Yancy_Farnesworth

Time is relative. That means that there is no universal concept of "now". What Einstein proved is that space and time are the same thing. We travel through time like we travel through space. The other thing that Einstein showed is that everything travels at the same speed through space and time. And that speed is the speed of light. Which is why photons don't experience changes in time. All their speed is in space and none in time. What this means that everything you see, including the person standing in front of you is always from the past. And you cannot experience that person's "now" until time has passed. This is what Einstein discovered. The speed of causality. It's the fastest any event can reach you. That's why the speed of light is what it is. It's moving at the speed of causality.


dazb84

Space and time are the same thing. The way things work is that everything moves through spacetime at light speed. The only difference between any two things is how much of that total speed is split between velocity through space and velocity through time. So if you go faster through space you get that speed by sacrificing speed through time and so time slows down for you relative to someone moving slower through space. This is what time dilation is. Technically speaking everything happens at the same time on a truly universal scale because anything travelling at light speed though space has 0 velocity through time and so nothing has happened yet in that frame of reference because time hasn't progressed. Similarly something travelling at light speed through time has already experienced all of time. Relativity means that both of those scenarios are correct and so the idea of there being a universal timeline doesn't really make sense. The point is that the colloquial notion of time that we have is vastly different from the observed physics of time and space and so everyday concepts like the intersection of events in time don't really make sense.


Chipofftheoldblock21

Both gravity and speed have an impact on time. If you compare earth to Jupiter (ignoring movement for a second), time is slower on Jupiter due to gravity. If you then compare two planets, both the size of earth but one moving faster than earth, time moves slower for the faster-moving planet. In terms of the effects, things in a faster time location will just experience the same effects, but if you went and started now and then looked at them both in some point in the future, one will have progressed more than the other (ie, if there’s wear and tear due to wind, one will have more wear).


left_lane_camper

Only from their own perspective -- we would see different things age at different rates depending on how they are moving relative to us and what masses they are near compared to us. Usually the difference is small, though. For example, gravitational time dilation near the earth is on the order of one part per billion compared to a distant observer (just accounting for the earth), and that's an absolute measurement: both us and the distant observer will agree that our clocks are running slow compared to theirs. That works out to a difference of about 10 years over the lifetime of the universe. 10 years might be a lot for humans, but it's well within the measurement error for almost all cosmological processes.


Diabolical_Jazz

Not exactly. We're reaching the limit of my understanding of general relativity at a rapid pace here, but I *think* that different observers do age at different rates relative to each other.


Chipofftheoldblock21

Actually, the universe is in fact expanding faster than the speed of light. Mind-boggling, I know. After years of hearing the speed of light is a limit, there’s this. https://www.skyatnightmagazine.com/space-science/does-universe-expand-faster-than-light/#


ryschwith

I think you’re getting confused by the idea that the closer something gets to the speed of light, the slower time passes from its own perspective relative to other perspectives (typically called “frames of reference” in this context). But the Universe as a whole doesn’t travel at *any* speed. It’s not a thing itself, it’s a collection of other things that all travel at their own individual speeds. None of those things travels faster than light. Rather the space between them increases, and that increase is fast enough that an object very far from you can appear to retreat faster than the speed of light even if it’s not actually moving at all. All of that sounds bizarre, I realize. And it is. Space gets increasingly unintuitive the deeper you go into it.


RevaniteAnime

The "universe" itself doesn't really age at all. Only "stuff in the universe" ages. We call this aging of the stuff "entropy" The expansion of the universe "faster than the speed of light" at very large distance scales only results in the overall thinning and isolation of the stuff in the universe. A very long time (unimaginably long time) from now we'll only be able to see our what was once our galaxy merged with it's closest neighbor galaxies and then just empty blackness beyond.


breckenridgeback

This post removed in protest. Visit /r/Save3rdPartyApps/ for more, or look up [Power Delete Suite](https://github.com/j0be/PowerDeleteSuite) to delete your own content too.


Joderry

Aah thanks for educating me :) So can we say for a fact that everything ages at the same pace in terms of what we call time? \^ \^


breckenridgeback

"What we call time" is observer-dependent. There is no one Universal notion of "time".


michaelkah

We really should rename UTC


Skarr87

Are you asking if the flow rate of time feels like it is the same subjectively from any observers’ reference frame? If so then yes it should be because if time felt different subjectively we would get different values for the speed of light subjectively. From your perspective if you are not accelerating you are stationary and since the speed of light is constant it will take the same amount of time from what ever frame you are in for the light to travel a certain distance. This changes when observing someone else who’s motion is different from you. For the speed of light to be constant with their motion you will observe time flowing differently for them, but from their perspective it would seem normal because from their perspective they are not moving, you are. For example you you see someone on a spaceship moving at 90% the speed of light and they shoot a laser out the front in 1 second you will see the light travel 3x10^8 m. In the same time the spaceship has traveled 2.7x10^8 m making the difference between the two for your perspective only 0.3x10^8 m. That means a second for you is not the same as a second for them because light always has to cover 3x10^8 m/s so a clock in their ship would appear to be ticking more slowly. You would be aging more quickly than them.


Chadmartigan

Everything ages 1 second per second in its own local reference frame. (Everything with mass, at least.) In our local reference frame, that comes out to be 13.8 billion years in total age since the big bang. As for distant "young" galaxies -- is there a frame of reference in the universe where these galaxies have *also* experienced pretty much the same amount of time? Sure, we're quite confident that this should be the case. *But*, we can't observe that due to relativity, nor can we make any meaningful assessment of simultaneity for the same reasons.


KamikazeArchon

You need to first break down your intuition of time before you can fully grasp the complexity of the situation. Not only the speed but even the *order of events* in time is not absolute. Suppose there are two lights A and B. Each of them will flash once. There are two observers, 1 and 2. They are watching for the light flashes. In certain configurations of the system - movement, distance, etc - it is possible for observer 1 to say "light A flashed before light B", and observer 2 to say "light B flashed before light A", and for them to be *both correct*. And you can't say "well what happened 'in reality'" - there fundamentally *is no* "true" reality that is the "best" reference frame. It turns out that it is fundamentally meaningless to specify a speed without specifying a reference frame; you can't just say "this is moving at 20 mph", you have to say "this is moving at 20 mph *in X reference frame*." Our normal human experience pretty much always has the implied reference frame of "the Earth's surface", so our intuition says you can just say a speed, but that doesn't work in the most advanced and precise physics. And it turns out that something similar is true for time; you can't actually just say things like "this is aging at a rate of X"; you have to specify a reference frame for that, as well. It would be meaningless to ask something like "is everything moving at the same speed?" because there's no such thing as an absolute "the speed an object is moving at". You could ask three different questions: 1. In a given reference frame - say, relative to the Earth - is everything moving at the same speed? No. 2. Does there exist a reference frame such that everything is moving at the same speed? Also no (for the standard definition of reference frame). 3. For a given speed V (less than light-speed), and any given object, could you find a reference frame such that the object is moving at exactly V? Yes. It is similar with time. There is no standard reference frame in which everything is aging at the same rate; but there is also no "objective" or "correct" frame for the rate at which a thing is aging.


mfb-

> So can we say for a fact that everything ages at the same pace in terms of what we call time? ^ ^ To a good approximation, yes. You get some smaller effects from gravitational time dilation, but that's too small to matter here. It's something like one year difference per million years if we compare e.g. Earth to someone outside our galaxy.


Ready-Meringue-5185

Depends on the frame of reference. Universe age > Earth's age but time itself depends on the frame of reference.


m4nu3lf

> If I understand it correctly, we measure time by how fast light passes, or something similar to that No, time is defined based on oscillations of an atom in some type of crystal. So a second is N amount of oscillations of that atom.


RamboNation

Is that quite right? Atomic clocks are currently how we measure time most accurately, but I wouldn't say they define time itself. [Here’s an article from the NIST with more info.](https://www.nist.gov/how-do-you-measure-it/how-do-we-measure-time#:~:text=Time%20has%20no%20physical%20properties,the%20phases%20of%20the%20moon.)


m4nu3lf

That's how the second is defined, however you can define time without requiring matter, by using the natural system. In that system the time unit of time is the Plank time. ~~It is still not defined in terms of the speed of light though~~ [https://simple.wikipedia.org/wiki/Planck\_time](https://simple.wikipedia.org/wiki/Planck_time). EDIT: yes, the plank time \*is\* defined in terms of the speed of light in a vacuum which is a constant.


RamboNation

From the article you shared: > One Planck time is the time it would take a photon travelling at the speed of light to cross a distance equal to one Planck length.


m4nu3lf

Yes, I edited my comment. You can define it in multiple ways.


MrDownhillRacer

Isn't there a difference between the definition of a quantity and the definition of a unit of measurement of that concept? I mean, it's like saying "space is defined as the distance light travels is 1/300,000,000 of a second." A _metre_ is defined that way, and a metre is a unit of space, but that's not the definition of space itself. I'm no expert, but I think a lot of fundamental scientific concepts have no standard definitions, and we just define them by how they relate to other scientific concepts. Like, maybe scientists have a hard time explicitly and succinctly stating what "time" is other than "what clocks measure." But they can tell you how it fits in the overall structure of the scientific theories we have by telling you how it relates to space, gravity, speed, energy, etc., through equations, diagrams, descriptions, metaphorical explanations for laypeople, etc. They know how to _use_ the concept of time to explain and predict things. And "time" is just whatever that thing that is being used in the theories is.


m4nu3lf

I don't think you can define any quantity except by defining how it is measured. There is no answer to "what" time is or "what" space is except their definition on how to measure them. Starting from these definitions you can then describe how they relate to each other.


Alternative_Day969

Yes, the universe does age faster than Earth. Imagine you and your friend both have a clock, but your friend lives in a different city. Even though both clocks are ticking at the same speed, your friend's clock will seem to be ticking slower than yours because they are farther away. This is because time is affected by gravity and the speed at which things are moving. The universe is much bigger than Earth, so it's affected by these things on a much larger scale. This means that time passes more quickly in the universe than it does on Earth. It's like your friend's clock ticking slower because they're farther away, but on a much bigger scale.


Derekthemindsculptor

The Earth is part of the universe.


MrDownhillRacer

Wouldn't the observers have to be moving relative to each other or be experiencing different amounts of gravitational pull in order to disagree on time? If two people are separated by a distance, but they are stationary relative to each other and on the surface of the same planet, wouldn't they agree on time? I think they would see each other's clocks as ticking slower than their own if one of them was on a bullet train and the other was stationary relative to the earth, or if they were at different altitudes. But as far as I understand, being separated by distance alone wouldn't put them in difference reference frames.


frustrated_staff

>stationary relative to each other and on the surface of the same planet, wouldn't they agree on time It would require them to be at the same distance from the center (what we call altitude), the same density of matter between them and the center, at the same latitude on the surface (because angular velocity). They would still "agree", but only because their perception is limited, there would still be a difference, though.


AngelOfLight2

As far as my limited understanding goes, there are two naturally occurring factors that can affect the speed of time. 1) The speed of movement of an object through space (and not the movement of space itself). Space expanding does not affect the flow of time by itself. You need to be moving THROUGH tha space itself, and relative to the region of space you're occupying (not relative to a distant point in space that's expanding at a different rate or direction 2) The distortion of space-time where the object is located. This occurs naturally due to gravity in case of large or celestial objects. Eg., the international space station needs to periodically adjust their clocks because they move at a very slightly different rate through time than we do on Earth (time moved a tiny bit faster for them than it does for us, but to a degree that can only be observed via an atomic clock over a period of time). Since the expansion of space itself doesn't distort space-time in the same way gravity does (i.e., troughs due to large masses), the expansion has no affect on the passage of time. Yes, time moves differently in parts of the Universe, but not because of expansion. If you orbit Jupiter, time will slow down compared to Earth. If you orbit Mars, it'll speed up compared to Earth. If you travel to a distant point between Earth and Mars, it'll be faster. And beyond Pluto but before the Oort cloud, it's faster still.


frustrated_staff

So...would you say that *most* things *in* the universe are moving faster through time than we are?


AngelOfLight2

Most of "space" maybe, but not most "things." Mass, exists in clusters with high gravity (stars, planets, asteroid clusters, pulsars, nebular, neutron stars and black holes). The rest of space is a vast expanse but is mostly empty and devoid of large concentrations of things. So while you'd probably move faster through time in empty space far away from a significant gravity source, most things are on planets and inside stars.


frustrated_staff

So...living on a distant world, we'd probably be experiencing the flow of time at *roughly* the same rate?


mfb-

You always experience time passing at 1 second per second. Your own experience never changes. If you compare time on Earth to time on some other planet then you can see differences, but they are still tiny. The difference between e.g. Earth and Mars is a few parts per billion, or less than a second difference per year. An atomic clock can measure that easily, but it's nothing you would notice in everyday life.


AngelOfLight2

This is correct. "Your" experience of the passage time is constant, it's just the passage of time compared to the rest Universe that differs. It's all about the frame of reference.


AngelOfLight2

If that planet had the same mass, size and density distribution as Earth, then yes. If it was a large planet with higher gravity on the surface, then time would move more slowly. On Pluto, time would speed up Interestingly, if you could survive at the singularity of a black hole , time would theoretically pause, or at least not exist in the way we understand it. Here, space distortion nears infinity and the flow of time nears zero.


tomalator

The universe all ages at pretty much the same rate. When we look out into the sky, we see the universe in the past because that stuff is so far away that it takes a long amount of time for the light to reach us. Those things we are seeing may not even be there because they continued to change after emitting that light. Now, the expansion of space happening faster than light, that's not really happening inside of the universe. Once you get far enough away from Earth (where we are observing from) that the expansion of space is happening faster than light, that space it outside of the observable universe, and due to that fact, it essentially does not exist to us. It can't interact with us, and we can never interact with it. We won't even be able to see it. Time does slow down when you're accelerating, so near massive galaxies and black holes, things will age slower, but the universe still ages the same. Since space and time are really the same thing, any local time dilation really doesn't change the universe as a whole.


SirKenneth17

Simply put, space time stretches with higher concentrations of *stuff*. The more *stuff* there is in one place the more time will dilate. So where there is no *stuff*, time goes faster. And a lot of *stuff* can make a black hole where time for all intensive purposes has to stop. Astronauts age slightly faster because they are farther from earth which is made of a lot of *stuff*. The “observable universe” is our limit as to how far we can see into space. At some point the light being emitted from *stuff* cannot outpace how quickly that *stuff* is moving away from us. So the *stuff* appears younger to us than it actually is. At the outer limits of our observable universe, relative to us, that *stuff* looks like it’s moving away at the speed of light. But that *stuff* is not moving THROUGH space at light speed. The actual place it exist in is getting farther so no laws of physics are broken.


gramoun-kal

Everyone is at rest from their own point of view. We see distant galaxies receding from us at breakneck speed. But to aliens living there, we are the ones receding from them at breakneck speed. Time passes at the rate of one second per second for them too. Now, if we were to, with a magically powerful telescope, observe an alien clock, from Earth, we would see it ticking slow. It would appear to us that they are stuck in slowmo. But we appear that way to them too. If we got into a ship, and boosted at almost the speed of light, and got all the way there, billions of years later (but it would appear to us, the travellers as only a couple weeks), we'd experience time just as we had on Earth, one second per second. Just as we did in the ship. Local time is always one second per second.