Time Ran Slower in the Past, Physicists Find

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Physicists from the University of Queensland in Australia have found evidence that time ran slower in the past. In this video I explain how time-dilation is related to redshift, what that means for light from distant galaxies, and what happens to an observer who falls into a black hole.
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[@SabineHossenfelder]

This video comes with a quiz which you can take here: quizwithit.com/start_thequiz/1720198942312x471922504050805250

[@Thomas-gk42]

🤔🤥😇

[@jasonbender2459]

I disagree... Things were just more boring in the past. As a kid, I played with mud pies, kids today have Iphones....

[@zosarion]

sabine whats your views on the supernova caused by kendrick lamar

[@smlanka4u]

The speed of light (relative time) depends on density of the medium. Therefore, it is not a true time dilation.

[@klocugh12]

@@smlanka4u Due to expansion of the universe, you will observe cosmological redshift regardless of medium. If there are differences in medium densities between observer and observed object, it's just gonna get tricky to unwind properly, probably implying some form of integration over whole observed distance to get precise answer.

[@brianmucha2391]

I’m turning 61 and I can state with absolute certainty that time ran a lot slower 40 years ago than it does today

[@andrewallston3139]

I knew we weren’t crazy 😅

[@kevinvanhorn2193]

That's because there's not enough novelty in your life. Do new things you've never done before, have new experiences you've never had before.

[@zenortheartof]

"felt time' is inverse proportional to the total time you have experienced already.

[@zenortheartof]

Like a toilet roll.. the closer you get to the end the faster it goes.

[@philiphumphrey1548]

That's because you've slowed down, so everything else appears to be going faster.

[@ianstopher9111]

Anton Petrov described this result 6 days ago, but Sabine's video was red-shifted, hence the delay.

[@4363HASHMI]

Our Prophet spoke about this ~1400 years ago also

[@olddog-fv2ox]

I need another beer😅

[@matheusdardenne]

​@4363HASHMI the only thing your profit did was topping a 9 year old. Get out.

[@rabiariaz2112]

​@@4363HASHMI Exactly! The hadeeth narrated by al-Bukhaari (1036) from Abu Hurayrah who said: The Prophet (peace and blessings of Allaah be upon him) said: “The Hour will not begin until knowledge is taken away, earthquakes increase, time passes quickly, tribulations appear, and there is a lot of haraj, which is killing, killing, and until there will be a lot of wealth among you and it will become abundant.” And Ahmad narrated (10560) that Abu Hurayrah said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “The Hour will not begin until time passes quickly, so a year will be like a month, and a month will be like a week, and a week will be like a day, and a day will be like an hour, and an hour will be like the burning of a braid of palm leaves.”

[@Elijah_Dove]

@@4363HASHMIdid he really?

[@Leif-yv5ql]

Time ran more slowly when I was younger. When you are twelve years old, fifteen minutes are a larger fraction of your life. Today, fifteen minutes are a blink of my eye.

[@AdamReese-wl1fz]

...why do scientists make everything overly complicated? Time, for us humans, has always been dictated roughly by the natural cycles of the sun. Theoretically.. if you left earth and exited our galaxy, there would be no sun over you, to dictate time and day. So what is a day at that point? Answer: nothing. So what is time at that point? Answer: we may never know because of our finite human brains. Doesn't matter because earth is a closed system! The truth is coming out. There is no space travel lol😂 feel sorry for you guys. Who believe in Star Trek lol

[@AdamReese-wl1fz]

And I agree with you, the repetitive lives we live (sleep, work. Eat, repeat) causes our brains to basically ignore our day to day "normalcy" when as kids... The world was brand new to us and time was better cherished😢

[@SonOfKong33]

When you're younger, you experience more moments. Probably because of your metabolism or maybe because everything is new, and you're paying more attention, so you're experiencing more per unit of time....I don't know, just an idea.

[@laestrella9727]

My understanding is that this is caused by how your brain stores memories i.e. nothing to do with time.

[@NightOwlTheater]

The whole time running fast/slow thing just continues to blow my mind. I can't get over my complete astonishment that a mechanical clock, which was designed to move at a precise rate, mechanically, can be manipulated by things like velocity and gravity. I'm 57 years old and I doubt I'll ever cease to be amazed by it.

[@Spectre-wd9dl]

Or it can't and they need stuff like this so they can continue to be right. Take dark matter and energy. There's some stuff that compromises over 90% of the universe but we can't detect it. Or maybe they are wrong.

[@SBImNotWritingMyNameHere]

​@@Spectre-wd9dl Time dilation has been proved to be real decades ago experimentally (Put 1 cesium atomic clock on earth and send 1 to space on a satellite and compare) actually required to be calculated for GPS to function

[@DaemonJax]

From the clock's perspective, it still does track the passage of time precisely, no matter what. And both perspectives are equally valid.

[@williamyoungblood4221]

@@Spectre-wd9dl no, this effect, unlike dark energy and dark matter, is rigorously tested and observed. The GPS on your phone wouldn’t work if it wasn’t compensated for by the software.

[@Syncrotron9001]

Its entirely predictable. Areas of increased gravity experience time more slowly compared to areas of lesser gravity. The universe is expanding away from a state of being more dense (more gravity) in the past to less dense in the future. 2+2=4= Time is speeding up.

[@AulisVaara]

I'm missing something: if it's due to the redshift, how is it not just an effect for our modern observations? How does it actually prove time used to run slower if the redshift is only present here on present day earth?

[@crawkn]

I agree that wasn't adequately addressed.

[@simesaid]

I saw this on Anton's channel the other day and asked myself exactly the same thing! Couldn't answer myself, though.

[@kiriankador782]

The narrative in this particular video is flawed and the title is unfortunate, I guess Sabine is just having a bad day

[@sfcsaferfantasycrafting6782]

Your right. She actually states it in the video. The red shift is due to light losing energy to a gravitational field. The farther it travels the more energy lost. Its got feck all to with 'the doppler effect' and an 'expanding universe'. These grifters are full of it.

[@crawkn]

@@simesaid Well put, we are much better askers than we are answerers 😆

[@Krueger_vr]

Maybe the guy running our simulation has been incrementally upgrading his CPU over the Eons. Pretty soon he'll be able to play KSP2

[@rupertchappelle5303]

Scott Adams is into the simulation theory. It's another label for "god" A.K.A. waves.

[@Cm-22000]

Too bad KSP2’s publisher shut down

[@Antilli]

But can he run Crysis?

[@AlbertBergen]

@@Antilli Can he run anything BUT Crysis?

[@cinemaofsounds]

Love this lady...I don't know what she's saying half the time but I could listen to her all day

[@MOSMASTERING]

Sabine needs to do an AMSR whispering physics talk for us that need to sleep

[@CAPSLOCKPUNDIT]

Sadly, this video ended far too quickly. But, rather than adjusting the playback controls, I think I'll just wait a few billion years to watch it again.

[@Chez8922-kf6cy]

Hot for teacher.

[@TheXrythmicXtongue]

Literally was JUST listening to Terrence McKenna talk about how time is "accelerating" in an interview today, and then stumbled on this!

[@gabiausten8774]

I can attest to that, whenever I was in gym class, time slowed, especially when I had to move fast…

[@tonysheerness2427]

That was the red shift, getting hotter.

[@friedmule5403]

@@tonysheerness2427 I am not sure about that, when ever I saw someone hot, did the time go way too fast and the red skirts did not make it go slower.

[@tonysheerness2427]

@@friedmule5403 When I get hot and flustered time drags.

[@andersjjensen]

Planking, while stationary, for some reason experiences the largest time dilation. At least by a factor of 5 I would say.

[@razvanlex]

That is strange, for me the math class did that. When I was playing sport and having fun the time moved faster!

[@grkuntzmd]

I agree completely that in the past time ran slower. I remember in grade school that sometimes time came to a complete stop, especially on Friday afternoons.

[@philiphumphrey1548]

It reminds me of the old poem about time "When I was a boy, I laughed and wept, time crept... As I daily older grew, time flew, soon I shall find in passing on time gone..."

[@castletown999]

"Time is an illusion. Lunchtime doubly so" - Douglas Adams

[@kjanttigvu6887]

The interesting question that the guy falling into a black hole raises is this: "Assuming the guy falling into the black hole is facing the outside observer (us), what does the guy falling into the black hole see?

[@SabineHossenfelder]

the light will be blue-shifted. though what they see depends on how they fall (straight, spiral, accelerated etc)

[@keithgarrett4155]

Good. If I recall, subjectivity( see also the twin paradox, why are people/physicist picking on twins?) the falling observer would also see the outside world slow down and grind to a halt. As I do not have an inate hatred of twins nor a star ship, I can not test this. Yet. :)

[@bodeeangus9957]

Wouldn’t it be logical to assume that the person who falls into the blackhole would see the universe speed up more and more until the heat death of the universe?

[@Milan_Openfeint]

@@keithgarrett4155 They see each other slow down in flat space (just flying around in empty space). I can say with certainty that if you hover near a black hole, the outside is blue-shifted. I'm not sure what it looks like if you free fall, a quick thought experiment tells me there's a small red shift (equal to the amount of spaghettification) but not really sure on this.

[@michaelblacktree]

@@SabineHossenfelder - So you'll get a nasty sunburn? Bummer.

[@bab008]

"Would they have noticed time was slower in the past?" I don't know. Fifth Period back in my junior year seemed to go on forever. Like falling into a black hole.

[@stephenkalatucka6213]

Watching the wall clock click off the last 10 minutes of the school day, I swear it moved backwards!

[@markoszouganelis5755]

Thank you Sabine!

[@raon123]

My first thought was this made sense because of the expansion of the universe and "average mass" being higher when everything was closer together but clearly that can't be right

[@tonyelsom6382]

Oh, I can positively confirm this..Time went tediously slow in my preteens, still slow in my teens, a bit faster in my twenties, similar in my thirties..but when you hit your forties time goes into overdrive, in a heartbeat you find yourself well into your sixties..Ya, I know, I'll let myself out.😇

[@MNbenMN]

Oh geeze, slow down the clock! I'm not ready for a two decade fast forward!

[@tonyelsom6382]

@@MNbenMN I wish I could, I'll be a billionaire AND still have ample time to enjoy it!..

[@behnamkakavand]

The explanation of the time dilation in this video is one of the bests I’ve ever seen. Danke schön!

[@gergelyritter4412]

I mean, almost every single time I see something "new" being "discovered" it's just smth that fits into Einstein's theory. Anf it's just so insane. The impact that this one man had on physics is just astonishing. There are very few people that have had such a huge influnce on anything.

[@rupertchappelle5303]

yeah, it's called "religion." Everything fits into the theories of most religious figures and justifies their belief, but spacetime curvature has overtaken traditional religion. That includes Marxism, CRT, LGTBQIA+ and any other ruling class scam. Everything justifies those things too. It's how crazy works. There's a sucker born every second.

[@stuartl7761]

​@@rupertchappelle5303 It's called a smart idea cause it's supported by observable evidence even a hundred years after it was first thought of.

[@rupertchappelle5303]

@@stuartl7761 So you think Joe Biden is competent and has no cognitive issues.. These curvature quacks are saying that the fabric of spacetime is "water falling" into the earth. - WHERE DOES ALL THAT SPACETIME GO??? If spacetime curvature curves or bends the path of a falling object why doesn't it also curve or bend the object falling? Toss a yardstick into the air and see if it curves to follow its path through CURVED SPACETIME. This Einstein crap makes talking snakes seem plausible. BTW the Big Bang - what exploded??? Nothing was there. You know, TIME curvature explains it better than SPACE curvature. One is demonstrable and one is not.

[@FredPlanatia]

Compliments on this episode. I really liked how you broke down the science and explained the meaning of this research. I'm a little comfortable with the implication that time was slower in the past. The point is that time is relative. From our point of view these super nova seem slowed down, but if you were an observer in those galaxies where they happened, then they wouldn't be slowed down. They'd follow the same curve as we see for nearby supernovae.

[@stewiesaidthat]

FYI, when the planet was first formed the rotational speed was around 6 hours a day, then it went to 12 and its current 24 hours. However, its orbit around the sun was still the same for a solar year. As the planet's mass increases, asteroids, comets, solar radiation captured by the plants, its rotational speed slowed down. Now, how do you want to measure time? A solar year or a solar day?

[@WeirdWizardDave]

Of course it did. The computers running the simulation must have been upgraded several times since it started...

[@sinousty]

Thank You Sabine and greetings from Poland ....... 🕓

[@Stan_144]

We love Sabine ..

[@professorxgaming2070]

Thank you for making these advanced concepts understandable

[@rognvalduringthorsson7727]

A question I've asked many physicists who didn't have an answer (nor able to tell why the question is wrong-footed, which is a likely option): If light is affected by gravity, why must the effect of redshift be due to expansion of the universe rather than of a "drag" effect of the collective gravity of the universe?

[@ix12]

wouldn't a "drag" make the light come later, not shifted?

[@rognvalduringthorsson7727]

@@ix12 I don't know, would it? If one could compare the light coming through a gravitational lens (bending around a galaxy) compared to it not bending around a galaxy, would it be more redshifted?

[@oaksnice]

Unfortunately a bot stole your comment and got a lot more answers than you did (because it has a sexy avatar). Anyway, I think the effect from gravity is so miniscule that it's drowned out by the effect from the expansion. And gravity on large scales should more or less cancel out since the universe is more or less uniform.

[@BaobobMiller]

@@oaksnice Oh I see... so it's a fake science channel with the purpose of keeping people chasing falsehoods to prevent the masses from making any progress.

[@BaobobMiller]

​@@ix12 It does both, and you likely already know why. the length of the wave itself is fixed. Think of the peek to peek distance of the wave function that she points out as being the nose and tail of a kayak with the body of the kayak being the dip between them. Now lets make this a self propelled kayak that does 7 knots at all times. The color we perceive the boat to be is the result of how long it takes for the peeks to go past the end of our dock. If the river is moving at three knots, we THINK that the boat has a color value of 10 when it is moving DOWN river past our dock and a color value of 4 when moving up river when in reality it has an unchanged value of 7 the whole time. All that has changed is the length of time it takes for the thing to pass making it SEEM like longer or shorter boat than it really is.

[@mbrochh82]

Fully agree. I can feel time speeding up as I grow older every single year...

[@BBirke1337]

I thought cosmological redshift is only due to expansion of the universe, meaning time 5 or 10 billion years ago was no faster or slower than now. A supernova at such a distance is redshifted due to Doppler effect, in fact, not by moving away, but by space being inserted between. So the light from a late stage of the supernova has to travel additional distance, therefore takes longer, making the supernova look longer lasting now. BTW, I hate internet questionnaires, which, in the end, ask me to register or submit personal data!

[@dodatroda]

Maybe there is no expansion.

Good question. I can imagine two sources to the redshift. One is simply the speed that the distant object travels away from us, and the other is the expanding universe elongates the waves. Are these two different things?

[@dodatroda]

No, same thing. And there are different explanations to the perceived redshift than actual expansion (which no one knows how it works anyway).

[@BBirke1337]

@@dodatroda No, it's very different. Expansion of space means, the other galaxy moves slowly, or not at all, taking lightspeed as reference. If it was moving away, it would be at a considerable part of lightspeed, so that relativistic time dilation became significant (like near the event horizon of a black hole).

[@TheBinaryUniverse]

The cosmic expansion is a RESULT of time slowing down. So you always get both together. Space and time are intertwined, you cannot separate them. Some say they are the same thing but I don't quite agree. When you start the clock, then it will take some time to cross a distance. Speed up the clock and distances, (and therefore space), gets "bigger", relative to before the time rate increased. This is what general relativity states, although most, if not all physicists don't see it that way. Special relativity also agrees with this view. Slow down time, (inertial time dilation), and lengths get shorter, they contract, (Inertial length contraction). You can never separate the two, time and space, because time "creates" space. With no time there IS no space. With the fastest time rate possible, you get a whole universe.

[@CkW38]

Let's say there are two devices, A and B. They are placed one light year apart. Device A continuously streamed the data to device B for 1 year, then stopped. If we are in a universe with no expansion, after device A sends 1 year worth of data, it would have to travel for 1 light year. Device B will have to wait for one year and keep reading the data for another year to read all the data that has been sent by A. If we are in a universe that expands by x2 every year, after device A sends 1 year worth of data, it would have to travel more than 1 light years. Device B will have to wait for 1

[@tsbrownie]

I'm getting older and I can tell you that 60 years ago, time ran very slowly, and now that I am approaching 70, years pass like minutes. So I am a witness for this phenom.

[@waseemaqrab8872]

Interesting description,the prophet peace be upon him closely described it the same way you did: Ahmad narrated (10560) that Abu Hurayrah said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “The Hour will not begin until time passes quickly, so a year will be like a month, and a month will be like a week, and a week will be like a day, and a day will be like an hour, and an hour will be like the burning of a braid of palm leaves.” Ibn Katheer said: Its isnaad is (saheeh) (authentic) according to the conditions of Muslim. And it was classed as saheeh (authentic) by al-Albaani in Saheeh al-Jaami’, 7422.

[@tsbrownie]

@@fadate7292 It's old hip slang.

[@Popashistory]

Quiz wit hit, sounds like a deflating place to go. LOL. Thanks for the video

[@SnydeX9]

When I was a kid, especially during history class, it ran very slowly. Now that I'm getting older, it seems to whizz by...

[@metalcake2288]

I think you need to retire from school now

[@pullupterraine199]

A few weeks ago, I asked here the same question: how an observer would see someone falling into the black hole. Now you answered it. Danke.

[@GrahamChristie-jg8sw]

Thanks!

[@SabineHossenfelder]

Thanks from the entire team!

[@duncanmcneill7088]

Just because the “T axis” of Spacetime is currently pretty linear doesn’t necessarily mean it is/was linear as we approach T=0. Or does it?

[@justanamerican9024]

So, it's not just me getting older that time seems to be flying?

[@Daniel-oj7bx]

nope as one gets older novel situations are decreasing therefore less conscious attention involvement is needed therefore less experience happens that would serve as a marker of time which makes one percieve time speeding up

[@JZsBFF]

Time's going faster but only slowly. It's entropy that's going at a hell of a rate.

[@keithgarrett4155]

Time flies when you are having fun( or so I have told), therefore you must be having lots of fun! ;)

[@Dyslexic-Artist-Theory-on-Time]

The process must be universal!

[@-danR]

This explains Sabine's previous dilemma of Germans getting less done nowadays. They used to have more time.

[@AdamZMouchnic]

Would you please elaborate more on observing an object falling into a black hole vs black hole evaporating? If Alice, jumping into the black hole, sends signal in regular intervals to Bob, a very patient distant observer, what does Bob see when the black hole finally evaporates?

[@tonywells6990]

It would appear random. Any signal will be lost in the chaos of the exploding black hole and is technically unretrievable.

[@janak132]

This fits well with the comment I made on "Bad news for dark matter: This data doesn't fit at all." Matter packed more tightly slows time. This should mean that time runs faster in the "voids" between galactic clusters due to lack of matter which would mean that the universe will expand faster and faster because time runs faster and faster in the empty voids the larger the empty voids get. "Dark Energy" would then actually be time running faster in the steadily growing voids and the larger the voids get the faster time will pass towards the "lack of mass influence" centers of such voids. Technically the expansion speed per time unit can be fixed, or even slowing slightly from clusters pulling on each other, but the rate of time in the fairly empty space of the voids would be moving steadily faster, meaning there simply are more units of time, thus more units of expansion. It can be likened to how the rotational speed of a vinyl record is higher the furtherer you are from its center, only that the rotation is the passage of time and the record represents a gravitational well; more time passes the further you are from mass. Voila, Dark Energy potentially solved. As a side note.. you could then get weak gravitational lensing in empty space if a void is very unevenly shaped, which I know has been observed and been declared as proof of Dark Matter. However.. if you have two or more centers of low-mass-influence-space would technically be less affected by lack of mass between these centers. If that area is large enough it would effectively form an oddly shaped apparent weak gravitational lense; an area of space where time moves slower than it does all around and since we are talking curving spacetime it would act like a lense.

[@tonywells6990]

There would be a difference of relative time passing in a void versus inside a massive galaxy but that difference is only a tiny fraction, probably amounting to only a few years over the 13.8 billion years or so of the age of the universe if I remember correctly. Does not solve dark energy.

[@janak132]

@@tonywells6990,Of course it isn't in line with our current mathematics for calculating time in relation to gravitational wells. What I'm suggesting is that instead of MOND they should be looking at a modified formula for Time. I'm suggesting that there's a threshold for gravitational interaction with time and that just like time dilation kicks in hard deep in extreme gravitational wells (or time dilations have a very low value until an object's velocity passes beyond 2/3 of locally measured c) the inverse might be happening when the gravitational effect becomes low enough. My suggestion is that the closest marginally measurable effect would be where our solar system ends. It would be much more measurable at the edge of a galaxy as you start coming out of the galaxy's gravitational well and go into fulle effect in the depths of an inter-cluster void. I'm suggesting that there must be new math, so proof of existing math doesn't counter that. It is my deep sorrow that I do not posses the skill to try to evolve this math.

[@tonywells6990]

@@janak132 Dead end, just like MOND.

[@nigelmartin9116]

Hi Sabine.If you had been my science teacher when I was at school, I would never had gone home.I love your accent and your humour.Your videos are fantastic.Keep up the good work.

[@arctic_haze]

This effect has been previously shown with the quasars (the Lewis and Brewer 2023 Nature paper).

[@Thomas-gk42]

Exactly, Sabine reported about that a year ago in the "weekly science news": "Time Ran Slower In Early Universe, New Study Finds".

[@SabineHossenfelder]

Yes, that's right. I talked about this back then. I thought it'd be worth revisiting both because a lot of people might have missed it, and also, because I missed the opportunity back then to point out the relation to the slow-down of time near black holes, which tends to confuse a lot of people.

[@MoreLifePlease]

How, if at all, does this affect our use of the Type 1A(?) supernova as a "standard candle" for measuring speeds and distances? I hope I got those terms right. I'm working from memory which sometimes has dubious outcomes....

[@arctic_haze]

@@MoreLifePlease A good question. I wondered about that myself but only for a moment (I am a physicist). Obviously time dilation must mean less energy emitted towards us every (our) second. But the redshift itself takes care of that. Red-shifted photons carry less energy. PS. Correction. The angular distribution of emitted energy looks different in different inertial frames. The energy per angular degree gets "boosted" forwards and "deboosted" (not my terminology) backward, that is towards us. So time dilation decreases the luminosity by 1/(1+z) while deboosting by another 1/(1+z) making the supernova luminosity as a function of z (redshift) proportional to (1+z)^-2 (to the power of -2).

[@MoreLifePlease]

@@arctic_haze Exactly! 🤪😁

[@blockmasterscott]

That is just amazing that someone was able to determine that time ran slower in the past. I’m serious, that’s incredible!

[@Desertphile]

Everyone my age has noted that time ran slower in the past. The years flash by in the blink of an eye when one is over 55 anons old.

[@ClemensKatzer]

Ah. So I have still 2 years ... months ... days ... minutes .. damn, got there too.

[@SnakeEngine]

Then don't blink to make it last longer.

[@creeperkinght1144]

In a story writing analogy, this is like having a character that is near perfect in personality, has overpowered abilities, and not enough people (if any) knows his weaknesses, and essentially say "good luck finding my crux." and he is stubborn and takes a lot for him to mature.

[@keithwalmsley1830]

We all know that time passes quicker when you're on your break or lunchtime at work than when you're bored at your desk! Everyone I know says time goes faster now than it used to, not just old gits like myself but even my 22 year old daughter thinks so too, I personally think time is just a construct of consciousness like the rest of the Universe IMO.

[@dalehill6127]

Personally I think it's an illusory sensation caused by a general shortening of many people's attention spans.

[@myhalong]

It's a trivial kinematic effect, the super nova seems to last longer because the last photons it emitted took more time than the first to reach us because during the duration of the supernova the universe expanded. Then this delay increases further because the last photons still propagate in a larger universe

[@victorkrawchuk9141]

If this is true, shouldn't it effect the way we measure Cepheid variable brightnesses in distant galaxies? I would think that the increasing time dilation with distance would make their periods appear longer the further away they are, making them seem brighter than they really are, in turn making us overestimate the distances to them. Or, is the Cepheid variable method unreliable for the distances we are dealing with? An excellent and informative video as always....

[@Thomas-gk42]

I think the cepheid measurement works only some hundred million lightyears away, so the effect is smaller like 1A supernovae, that are much brighter and therefore visable in longer distances.

[@SabineHossenfelder]

In principle, yes, in practice, the effect is too small to measure because they are much closer than the supernovae.

[@victorkrawchuk9141]

@@SabineHossenfelder Thank you for explaining this, I appreciate that you took the time to respond.

[@danpatterson8009]

My humanities and social studies courses were in the past, and they certainly made time go slow.

[@JK_Vermont]

I’m confused by the title, as it doesn’t seem that “time ran slower in the past” is a particularly good interpretation of what is going on here. It’s not like, say, stars, where we might say “stars had lower metallicity in the past”. We can deduce this by looking at spectra and (after correcting for redshift) make an apples to apples comparison. In this case, we have no means of comparing proper time in the past with proper time today. It’s not like we can put a cesium-133 atom from 12B years ago next to one from today and see if it has fewer hyperfine transition cycles in a second. So all we are really seeing is that “clocks in the past as measured in the present appear to run slower than clocks in the present” which has nothing to do with how fast time ran “back then”. In fact, wouldn’t “time ran slower (or faster) back then” be shown by a *mismatch* with theory in which redshift alone did not adequately predict the brightness curves of Type 1a supernovae?

[@SabineHossenfelder]

I see what you mean, I think, but it's as correct -- or not correct -- as saying that time runs slower near a black hole. And yes, indeed you can read the paper to say that redshift alone does not adequately predict the brightness curve. That said, it's a small effect and if you only look at the spectrum shift, it doesn't matter. Indeed you can see in the figures that I show in the video that by eye the difference is basically not visible.

[@JK_Vermont]

@@SabineHossenfelderOk I see what you mean about the black hole comparison. I guess comes down to the fact that we can never directly compare proper times in non-comoving frames, we only have observations across the frames.

[@beauwilliamson3628]

@@SabineHossenfelder As presented, it really does seem that saying 'time ran slower back then' is the same as saying the light emitted was 'redder back then'. "The redshift alone does not adequately predict the brightness curve" would be the key finding here. I'll keep trying to wrap my head around this.

[@HughSheehy]

@@SabineHossenfelder Still, a black hole and its local effect is a bit different than suggesting that time in the whole universe ran slower. From the explanation and a quick (mostly incomprehending) scan of the actual paper, the result seems to be that we see events taking longer because they're at the other end of an expanding universe rather than any idea that time ran slower at the time the events happened.

[@isonlynameleft]

This is just a consequence of relativity. I'm not sure I like the phrase "time slowed down" though. I think it's better to just say time is relative because time never slows down in your own frame of reference. Hence, it's relative!

[@EgonSorensen]

I remember when I was a kid and it was December 1'st - it took nearly FOREVER to get to the 24'th. Now, I see it's December 1'st again - and before I blink, it's the 24'th .. again

[@EgonSorensen]

@ButConsiderThis I'm (still) doing unique and memorable things quite often. I suspect it being due to the resources of the Internet, being exposed to so many different interesting things, that I now feel time is flying by so fast. 'Back then' the Internet wasn't available, I had read all interesting books at the library and it was either too cold or dark to be playing outside for long in December (I'm living in Denmark, north of Germany).

[@TheInfectous]

@@EgonSorensen "I'm (still) doing unique and memorable things quite often." Relatively? No, you can't be. As a kid when you first play any new sport, you're experiencing new ways to move your body. As an adult, even if you've never played a particular sport, you've likely had experience moving your body in similar ways and understand the win conditions as relative to another. e.g. basketball scoring a hoop is just like shooting a ball in a new in soccer but for a kid that's a new concept entirely. Even the idea of a game is unique, that we make up imaginary rules and compete against eachother, you can never get the experience of learning about a game for the first time and every subsequent learning will be less new. As a kid when play a video game everything in that game is new. As an adult you can recognize how similar the patterns in that new game is to all the past games, same with books, movies, tv and every other form of media. As a kid when you go to a new country, the culture, architecture, political systems, climate etc. are all new. As an adult you've at least heard of most of these things, have watched things with those things presents and understand the functions of different types of systems. Even for education there's only so much you can tap into life, math-programming-logic-philosophy all have massive overlap in how functionally those things play out in your mind. Art, design, music, poetry, writing all have overlap. etc etc. Don't get me wrong, you can experience new things, enjoy them and experience a euphoria that can be just as rich and enjoyable as that of a kid... but there's nothing that will compare to the novelty of your first endeavours into new sensations, experiences and learning. I'm strictly talking about the underlying processes of how your mind works, functionally, your brain won't experience novelty as often because you can relate any new experience to so many other experiences and draw on that knowledge.

[@EgonSorensen]

@@TheInfectous - '"I'm (still) doing unique and memorable things quite often." Relatively? No, you can't be.' I was an exchange student a loong time ago, and at 'welcome/integration' camp we were asked to draw a tree. Roots, Stem, Branches, etc, etc. Some did a rudimentary job - others went all-in. The purpose of the lesson was to learn that life is like a tree, it branches - it leaves, and once left - right, more to go. In other words, we were told (taught) that there's always more to do, experience, learn, teach, etc - and the only one responsible for ones doing is oneself. You take the easy path, you get a lousy looking tree. You go all-in, you're never bored unless you want to do and experience that ;ø) It took me a while to see the full picture, but the roots of that understanding were planted back then. A healthy tree needs nourishment, time, love and room to grow. I heard peoples brains are always changing, and in my experience my experiences change. Playing games, sure I recognize patterns and know how my body usually responds - doing Yoga, I experience how my body strengthens (and weakens) when I'm mindful about my every-day experience. In a way, back when I was a kid, I had lots of new things to do and experience - I do now too as an adult. Talking to my parents, they're also quite active, and I'm sure that when I say they're NOT experiencing time as they used to either - neither their bodies, which also aren't as they used to be (I haven't asked directly, but I have observed it through their behavior) Btw, Eg is Oak in Danish, and I'm still growing and going. Egon

[@Leto2ndAtreides]

Feels like it could be linked to the accelerating expansion of the universe. I also half think, that if the universe is computational at its core, then you could have more difficulty of processing, if there are more complex interactions to simulate (even if the processing itself is using countless decentralized nodes) More matter density could be increasing local complexity.

[@mcdoj2763]

I'm almost brought to tears hearing you needing to emphasize the importance of science. The limitless spread of any and all information is collapsing our global mind.

[@juliavixen176]

I think you meant to say: "misinformation"

[@ariajames4677]

If you are not in the financial market space right now, you are making a huge mistake. I understand that it could be due to ignorance, but if you want to make your money work for you... prevent inflation

[@Brianna_Hend]

Thanks for continuing updates I'd rather trade the crypto market as it's more profitable. I make a good amount of money per week even though I barely trade myself.

[@ariajames4677]

A lot of people still make massive profit from the crypto market, all you really need is a relevant information and some ‹professional advice. ‹it's totally inappropriate for investors to hang on while suffering from dip during significant

[@Brianna_Hend]

You trade also?, I

[@ariajames4677]

No I don't trade on my own anymore, I always required help and assistance

[@ariajames4677]

From my personal financial advisor ..

[@slo3337]

I've been pondering this for a long time. Could it be that the "big bang" took much longer due to extreme gravity

[@Audio_noodle]

Maybe mentioning, that the time running slower was due to the universe being denser directly, instead of through comparisons with black holes could have clarified the concept a bit, but otherwise pretty well executed. Also seeing how much slower due to density delta could have been interesting. At least from an intuitive perspective i would expect the redshift to be more dramatic very close to the beginning and then stabilize as matter drifts further appart.

[@liamroche1473]

@Audio_noodle, I don't believe that is a correct description - the red-shift is because of relative motion rather than a gravitational well: the Universe was even flatter then than now on a large scale. According to present understanding, individual remote objects have very slowly growing redshifts now because of dark energy (which increases relative speed). You can think of redshift as kind of like a measurement of relative speed - it has an identical effect on energy per particle (photon) to that on a massive particle that is moving very close to the speed of light (whose energy changes with relative speed in a different way to in a Newtonian universe). Likewise gravitational redshift is like when a similar massive particle at near the speed of light loses some speed and thus energy after it leaves the gravitational field. The point is that what we see is the former rather than the latter.

[@Audio_noodle]

@@liamroche1473 didn't dark energy start to have an effect only much later on? According to nasa only at around 9 billion years from big bang

[@liamroche1473]

@@Audio_noodle Yes. This is still not fully understood.

[@tonywells6990]

Time dilation due to matter, eg. in the early universe or within a galaxy, is a tiny fraction compared to cosmological expansion.

[@liamroche1473]

Simple fact is that the time dilation is not gravitational, it's essentially special relativistic, mainly about relative velocity. The relative velocities have changed a bit, but not very much, so the redshift has been there all the time. To put it another way, if you imagine a 13 billion year movie of a very remote region of the universe, it starts very red-shifted (due to relative velocity) and it continues to be very red-shifted to the present day. There is a correction to older cosmologies that would have had the red-shift being constant, but it is not a huge correction.

[@casnimot]

Feels almost like a 'follow-up' in some ways, confirming that, indeed, more distant objects are moving faster relative to us and so should be dilated relative to us. The trickier part, I imagine, is going to be teasing out any patterns of acceleration/deceleration as we look back at higher redshifts.

[@EmilyGrace200]

Hallelujah!!! I’m blessed and favored with $60,000 every week! Now I can afford anything and support the work of God and the church. For Your glory, LORD! HALLELUJAH!

[@AmandaNicole__0]

Oh really? Tell me more! Always interested in hearing stories of successes.

[@EmilyGrace200]

This is what Ana Graciela Blackwelder does, she has changed my life.

[@EmilyGrace200]

After raising up to 60k trading with her, I bought a new house and car here in the US and also paid for my son’s (Oscar) surgery. Glory to God.shalom.

[@JessicaMarieXrp]

I know Ana Graciela Blackwelder, and I have also had success...

[@JessicaMarieXrp]

Absolutely! I have heard stories of people who started with little or no knowledge but managed to emerge victorious thanks to Ana Graciela Blackwelder.

[@MemphiStig]

I'm currently doing research to determine if time does indeed run slower when you're bored and faster when you're sleeping. In late November, after Thanksgiving, I'll be attempting to calculate exactly how slow Christmas is.

[@xlerb_again_to_music7908]

Sabine: Request for clarification: Does this paper say "Time was slower in the past" OR "We observe things from the past happening slowly"??... again, potentially a problem of observation - it's the observation which looks slow vs. the actual speed of the event...?

[@philochristos]

Now that you mention it, it does seem like time is going by quicker the older I get, which means it was moving slower when I was younger.

[@omsingharjit]

I knew this long before than physicist . And it can solve galaxy rotation curve problem by applying time dilation.

[@raphaelrossi6339]

Could you explain, when light gets redshifted by various means, where does the energy go? That is if an electron in a hydrogen atom emitted a photon and by a lot of luck, traversed halfway around the visible universe and came back to the same electron in the same atom, but greatly redshifted, where did the “lost” energy go?

[@stuartl7761]

That's a brilliant question with a not at all trivial answer. Basically, the classical idea that energy is conserved doesn't hold when you've got a curved spacetime. There are equivalent energy conservation equations in general relativity, and they kinda shift energy from material particles into the fabric of spacetime itself. Though those equations are rather abstract and hard to interpret. A more conceptual understanding is that if you picture a particle getting shot out at 100 km/s from a galaxy travelling 50 km/s away from us, it would reach us and appear to be travelling at 50 km/s. Even in classical mechanics this particle is seen by us to have less energy than it's host galaxy would say it had because energy isn't conserved between different velocity reference frames. One way to look at an expanding universe is to say each galaxy has a different reference frame that's a bit faster than the previous one. So the further you fly, the faster the galaxies you come across, and the slower the galaxy says they see you flying. Light doesn't change velocity cause relativity, but it does change momentum, and thus energy, in the same way as the particle above. Travelling around and back to your home galaxy while the universe expands around you effectively means that your home galaxy accelerates into a new reference frame with respect to you, in which they would see you as having less energy upon your return.

[@tonywells6990]

And to add to stuart's answer, if the universe does collapse again (although unlikely) then all of that lost energy will be gained again which will reheat the universe.

[@raphaelrossi6339]

@@stuartl7761 Thank you and Tony for your reply. I do appreciate the classical two references frames example, and somehow the "lost" energy (at least in my mind) gets interwoven into space (time?). Yet I am still grappling with this. Maybe, probably won't come to full terms with it, and that is ok. Very good point. So if you sent light from a moving train, it gets red (or blue shifted depending on the direction) in an outside reference, and if it were redirected after leaving the train (the reference frame) back to the train carriage, it would get further red shifted. As it is true similarly with an expanding (or contracting as Tony points out). But this is not the case if the light always stayed in the reference frame, the train carriage or earth moving through space, and was bent back to the source. It is a can of worms for me. Because I can understand how mass, even light moves through space, the physical mass of the train and the light inside of the carriage whipping through space, yet what about the space inside of the carriage? Is the space inside the carriage, the space in which the light travels, the emptiness of space, the fabric of space, the higgs field, ... also moving with the reference frame? If the space is not moving, then I have trouble understanding the discrepancy between the red shifting of the light when leaving or staying entirely inside the reference frame. Yet if the space is moving, something that is hard for me to imagine, I can visualize the difference. If you sent a photon from a train carriage and bent it back to its origin, it would not be red shifted. Energy conserved. Yet if you sent a photon from a train carriage, and it exited the carriage for even the tiniest amount of space and time, and bent it back to the origin, then it will be red shifted. Maybe I am missing something? Obviously I am missing something. It is all pretty amazing though. Thanks you two. Sorry if I didn't articulate my inability to grasp this that well.

[@stuartl7761]

​@raphaelrossi6339 I think an idea that might help is that reflection is relative. A stationary mirror will reflect the light with the same colour back to where it came, but a moving mirror with shift it's colour. If someone on the train shines light backwards and a mirror on the train reflects it back, then the light will be unchanged. What someone outside the train would see is the light shone backwards will be redshifted, but then it gets boosted by a moving mirror and becomes blueshifted the same amount as if the passenger had shone their light forward. In terms of galaxies this is equivilant to the light bouncing off a high velocity star or being energised in some other artificial manner. If the train passenger shone a light at a receding mirror on the ground then they would see the light return to them doubly redshifted.

[@raphaelrossi6339]

@@stuartl7761 Thank you Stuart. That helped. I guess this is exactly the strangeness of special and general relativity and the whole point about the reference frames, and the collapsing or compressed space.

[@spinninglink]

I've always thought about this and even made several comments about it before. My idea was since a lot of mass and matter were a lot closer together back then, and we know objects close to nearby massive objects experience time slower, then time was slower in the past. And would be why we "think" the expansion of the universe is accelerating. It's not actually accelerating, it just appears so, because time was moving slower in the past compared to now!

[@tonywells6990]

When you do the calculations you find the slowdown of time is by a very very tiny fraction and can be ignored. It only becomes large in the first fractions of a second after the big bang.

[@pokeman747]

I've been observing this my entire life nice to know it's actually happening

[@absolutmauser]

"its like watching paint dry... In space." 😂 Got me with that one.

[@markh.harris9271]

This is intuitive from the standpoint that since 1905, we know about time-space, and that since Edwin H we know that time-space is expanding... this means there are some obvious intuitive things to say about time, as well as space. Time must have passed (whatever I mean by that) slower in the past; has to be. Yeah, that guy again... marcus

[@Harvey_Pekar]

It's about time you guys caught up.

[@WayOfAges]

Given that everything in our neck of the Penrose universe started out at or below the event horizon of a primordial mass - at or near infinite time dilation - then yes, we should expect a sharp ramp-down after the Big Bang followed by an asymptotic approach to the physical limit of time progression we experience today.

[@krokeman]

That's why we can't "see" past big bang. It's like a horizon, the distant objects get smaller and smaller thus they appear densly packed, then disappear behind it. If we could move back in the time we would still see "big bang" 13.8 billion years ago. I wonder if we could calculate curvature of our time bubble.

[@thabokomane6105]

😂😂😂 I like Sabine's humour! "finding a dial-up modem in the attic" 😂

[@janetf23]

For me, the speed of time passage is relative to how much I'm enjoying myself⏳

[@roddneyfett444]

I still have a problem with speeding up expansion. The further out we look, the further in the past it is. If the red shift is larger for more distance objects, doesn't that mean the expansion was greater in the past and less so now? Doesn't that mean that the present expansion being slower demonstrate an expansion rate that is slowing down from the past?

[@stuartl7761]

The further back we look, the further away we see. And for any expansion history, more distant objects will be travelling away faster, so redshift would increase with distance as long as the universe is generally expanding to even a slight deceleration. You'd be correct if that's what we saw, but what we do see is that distant galaxies are travelling slower away from us than expected if we extrapolate from nearby galaxies.

[@Hydrogenblonde]

I totally agree with other commenters that time years back definitely moved slower and you could notice it. Time now is going so fast it's like there are rocket engines pushing it.

[@everTriumph]

Explains why I always struggle to keep up with the modern world.

[@dpilcher]

I’m no physicist, but I’ve always thought that if the universe were much denser than time would have been much slower so the further back we look we are looking at static images of past galactic formations as their light radiates from the edge of the event horizon, which would make the CMB more like ghost images of what has recently finished crossing

[@joemendyk9994]

Your confusing time with light. Light is affected by distance and time. Time is not affected by light or distance.

[@Unmannedair]

I thought this was already established? If the light that we see passing between stars is passing through the region with the least gravity, then over time as the stars drift apart the minimum gravity will get less... This is exactly identical to looking down a gravitational well... Time moves slower at the bottom of a gravitational well.

[@WensleydaleBrown-wo5rg]

Make the most of each and everyday, one thing we never get more of is time. ❤

[@shawn0fitz]

There's two different causes of the redshift, the expansion of space and curvature. But how much is due to which and what curvature are we talking about, the exploding star or something else?

[@tonywells6990]

Curvature, within galaxies, is a tiny fraction so the majority is due to cosmological expansion.

[@ПётрБ-с2ц]

Paint drying comparison blew my sides off.

[@picksalot1]

How much slower did time run compared to today for something 100 light-years from us? Units of Time, or a relative Percentage would be interesting to know.

[@stuartl7761]

The equations that describe the expansion history of the universe assume a homogenous distribution of matter, which is only really true once you start dealing with scales over 100 million lightyears. So the gravitational influence of the milky way would remove any possible effect from observing an object 100 lightyears away. But if the equations were valid then an object 100 lightyears away would have a redshift of 7*10^(-9), or equivalently time would travel at 0.999999993 times the rate of time here.

[@picksalot1]

@@stuartl7761 Thanks for taking the time for working through the equation. 👍

[@daemonmarchant6179]

I have intuitively thought for years that the rate of passage of time of the universe changes due the the size and expansion of the universe (or at least what we perceive as the universe). If the rate of passage of time was slower previously - then how slow was it during the very early universe - and what are the implications for the "inflation" period, and how early stars, galaxies, and black holes were formed, in that period of time.

[@tonywells6990]

The rate of passage of time over the history of the universe has not changed. This is an observer effect, what we perceive is events seem to have run slower in the past but it is only due to expansion of the universe red shifting light from the event. If we study a distant supernova it appears to last for a longer time than it should (maybe 6 weeks instead of 3 weeks at a redshift of z=1) due to cosmological time dilation, effectively appearing in slow motion and this is good because it can help astronomers study distant events and also prove that universal expansion is real. In reality the supernova lasted for the usual 3 weeks or so in its local spacetime.

[@daemonmarchant6179]

@@tonywells6990 Ty for the explanation.

[@ZXLMaster]

It would be intriguing to observe Sabine's attempt to present the planetary configuration exclusively through logical and replicable methodologies, which can be understood by all individuals. This would serve as a demonstration of the scientific method. ❤

[@JaguarBST]

1:30 yes that guy again!

[@maciekwar]

everyone who is older will tell you time in the past run slower, now it runs super fast :) that way we say "time flies" :P Sabine you have to be in your 20ties if you have not notice it yet :P

[@Milan_Openfeint]

Now I'm confused. Did the time run as slower as expected from the redshift, or slower than that? A bit more discussion of the graph @~ 3:40 would be nice. What do the blue dots mean and why are they above the mean?

[@zegermanscientist2667]

Fun fact: as the astronaut falls into the black hole, they seem to slow down for us, but to them, the universe is speeding up. When they pass the event horizon, they will have seen the remaining time of the universe. All of it.

[@einsteinalb75]

I've been saying this way before they did. How can we measure the age of the universe accurately when time was newborn and running differently in the beginning?

[@blackasthesky]

Ich hab so viele Ideen zu einem SIII-Klon, ich hab auch schon ein paar mal angefangen zu prototypen. Es sieht so aus als wäre "The First Explorers" genau das Spiel, das ich immer machen wollte.

[@Andiness.]

It's kind of funny to hear you talk about something in a video about a university that I used to hang around that, that would be Queensland Uni. I never went there, I just visited all my friends who went there back when I was living in Brisbane, or BrisVegas as I believe they call it now 😅

[@AisleEpe-oz8kf]

motion in, time out. thanks doc.

[@kylelochlann5053]

So... gravity grabs onto the closer end of wavelength and forcefully yanks it downward with a force greater than gravity grabs onto the leading edge of the wave, and pulls it into a longer length? Is that the explanation for the gravitational redshift here?

[@matheusdardenne]

I had the impression that this was known already. Time dilates in gravity wells. The universe was denser in the past, and extremely dense during its initial stages, so time was extremely dilated then. I can't bother myself to do the math on it, but I also think this higher density in the past explains the apparent acceleration of the expansion of the universe. The more distant we look, the older that light is, which means it was emited when the density of the universe was bigger, which means the gravity well of the universe was deeper, and we know light redshifts when escaping gravity wells.

[@techsinc]

I knew it! I find time to flow faster now I am older than before!

[@hanneskarlbom6644]

Whenever I hear about time dilation it sounds more like computer lag than time itself slowing down. Like how time moves at a regular rate ¨outside¨ the computer, whilst the time inside of the software seems to slow down but from the world inside it, it would appear normal. Or: Time is the same, but the clock is just physically moving slower and so is the observer so they won't notice a difference.

[@SplendidFellow]

Here's something I never quite understood. Redshift is observed when light is seen that is from an object moving away from the observer, yes? Sort of a light equivalent of the Doppler effect? But if the universe were increasing in the rate of its expansion, would we not see the opposite of what we now see? The furthest objects away from us have the most perceived redshift, yes? But if the universe is expanding faster now than it was in the past, would we not see *more* redshift on closer cosmological objects, due to the expansion of everything away from everything else being faster now than it was during the time of the distant things we see in the cosmos?

[@thomasAnders2765]

Great talk again 👍🙏🏻🍀 I am happy to get these insights There is no need for any words nobody understand. In consequence it means because galaxies are drives away and space is increased time is increasing too.

[@iannoble8626]

As I understand it, the redshift-related changes Sabine describes are from the spatial expansion of the universe in its earlier periods. But ever since Minkowski and Einstein, we've being thinking in terms of spacetime rather than just space with a separate dimension of time. It seems obvious that, if the universe's spatial dimensions have stretched, its time dimension should have as well (from a "period" of no time, to the one we find ourselves in today). It would be somewhat singular to find that it hadn't, and that "immediately" after the big bang time was already ticking at its current rate.

[@justicewillprevail1106]

Wow... I've always felt the time feels like it's moving faster as I age. Thought it was in my head.. but I guess it's true.

[@billsmart2532]

Yes I agree, back when I was in school, hours seemed like days…

[@NGC3982]

With redshift alone, either time is constant but space is expanding or space is fixed but time is slower in the past or both. No?