Is the strength of gravity really CONSTANT? | Solving the crisis in cosmology

[@captainoates7236]

"Have you ever wondered if the constants of physics are actually constant?" Yes constantly.

[@vigilantcosmicpenguin8721]

I wonder about that at a possibly varying rate.

[@Nukepositive]

I'd love to see a video on the same idea of the speed of light being constant or variable. How do we know light doesn't "speed up" once it leaves the influence of a star system, or galaxy, only to slow down on reaching real and/or dark matter again?

[@roichir7699]

@@Nukepositive Very simple. Space police has speed traps and there are some very hefty fines on exceeding the speed limit.

[@AmbivalentInfluence]

It does vary, under the influence of gravity. Because time changes too, it appears to be constant.

[@AmbivalentInfluence]

@@Nukepositive I would argue that this is precisely what does happen. Therefore, all of the constants are actually ratios.

[@terpcj]

Back in the early '80s, when I was a snot-nosed undergrad, I got to spend a couple of hours discussing gravity with a professor (RIP) still a couple of decades away from his becoming "known". I was more on the gravity-isn't-immutable side of the discussion, and he was more on the gravity-is-a-constant side (though we flipped a couple of time if only for devil's advocacy). It was a fascinating discussion in which he of course prevailed if not only by sheer big-brain-ness but also by much better math. Still, his spending that amount of time with an undergrad just tossing mad ideas about is something I still think of fondly.

[@markfergerson2145]

I wasn't even an undergrad, just a random person who wrote Robert. L. Forward a letter about variable G years and years ago. He responded with prints of a few of his papers, some suggested reading, encouragement to keep asking big questions and his own speculation on the topic (he thought it barely possible but unlikely). My sole claim to a brush with greatness.

[@ehsnils]

Every time you get a question from someone not deeply immersed you get a new perspective and that would make you think about how to explain what's working/not working with that perspective. In rare cases this could lead to new discoveries.

[@jrkorman]

Wonderful - exactly what a scholar should be doing.

[@vigilantcosmicpenguin8721]

That's what learning is all about.

[@mastershooter64]

lol why even take sides? it's science!

[@Kae6502]

Back in the 90's, a friend and I observed that on certain days, we were more prone to drop things than normal. Rather than admit to our own clumsiness, we proposed a theory that Gravity was not constant, but a variable. "I'm having a High Gravity day!" we would often say to each other. We also thought it would be helpful if weather forecasts included the day's gravity index based on something I called The "Newton-Stein" scale, with advisories to not climb ladders or go skydiving on days with a High-G forecast. :D

[@AaronWhiffin]

Fridays and Saturdays when you were in the pub by any chance?

[@tomimantyla8236]

Sometimes it is hard to get up from bed or sofa. I blame increased gravity too. Or maybe gravity is simply stronger near sofas and beds?

[@steveegbert7429]

A few high gravity beers have a tendency to make you drop things as well.

[@billoddy5637]

Consumption of alcohol considerably increases the gravity index for the day, I’ve found.

[@erinhaury5773]

In my family, we always called it a 'gravity storm'. 😂

[@glennpearson9348]

Great video, Dr. B, like all of them. Your self-deprecating humor (particularly the out take bloopers) combined with your obvious love for astrophysics and all things sky make every episode a complete blast to watch. It's quite difficult to find education and entertainment in the same KZbin channel these days, but yours is a heavyweight contender. All the best and - stay curious!

[@ESF19791111]

MY THOUGHTS IN THOSE WORDS :) THANK YOU FROM ISRAEL :)

[@georgesheffield1580]

Proper British humor

[@MattCruikshank]

30 seconds in, you show "i.e. 0.000,000,000,066,743 x 10 ^ -11". I'm pretty sure you didn't mean that last "^ -11" in there. Love your content!

[@DrBecky]

Whoops!

[@renx81]

Was just about to comment on this, but I knew someone must have beat me to it. Well done sir!

[@ollysworkshop]

@@DrBecky maybe Becky's on to something and she's not released the paper yet......?

[@billbolton]

@@renx81 and I missed it completely.

[@Mark-wx8ne]

@@ollysworkshop I was thinking the exact same thing

[@iloveplasticbottles]

Your channel reinvigorates my love for astronomy

[@anushnandanrao2483]

You know like I'm just very happy that real people like you give your best and do your work right from the heart and all your want is just to spread knowledge of science to the general audience and this makes me really happy..... Many people spread many misinformation and use science as tool for it which makes me very sad to see those things..... As a science person I really appreciate your work and what you do for a living ❤

[@DrBecky]

Thanks Anush 🤗

[@waynedarronwalls6468]

@@DrBecky hi Dr Becky, think someone has spoofed your KZbin channel, as I have a message re WhatsApp from someone purporting to be you, however they have no tick against their name...just thought you should know, as the reply is not showing as being from you...

[@karlakirkpatrick2214]

I happen to agree with that.

[@klaxoncow]

I would hope that Dr.Becky is using her brain to do her work, rather than initiating it from her blood pump. Live long and prosper.

[@kevinm7734]

@@DrBecky can it be said that in similar manner other constants other than G could also change across the galaxy.

[@phillyphakename1255]

That magnet demonstration was incredibly impactful for showing the difference in magnitude between gravity and electromagnetism.

[@keerthanarbn]

I appreciate that you are constantly updating us with this information. You’ve been a great help for me, especially with my studies. Thank you ❤️

[@silverXnoise]

The Smethurtilogical Constant: a measure of the immense flow of information from Dr. Becky Smethurst and a community of wonks on KZbin.

[@DrBecky]

Amazing! You’re very welcome

[@zoidberg444]

Having become aware of this crisis in cosmology and though self educated and not an academic the first thing my mind went to was the force of gravity not being constant. Its a relief to know that experts in the field have also considered this idea.

[@juzztime]

The Gravitational constant that I know is that it constantly hurts when hitting the Earth 🌏 after falling from a great height 🤕 Love your work Dr Becky 🥰

[@Huntracony]

I always love it when science looks at every single assumption of the reigning theory and just asks "what if that wasn't true, would things make more sense?" Usually the answer is 'no', but sometimes...

[@JJ-rl5ef]

I agree. My background is Physical Therapy, but I have been following astronomy the past few years, as a hobby. It's good to know the mainstream ideas, but advancements can come from the questions.

[@leapdrive]

The hard part is when these scientist spend billions of dollars of our taxes to find answers, they find more questions instead. I think we can slow down a bit in research to give us tax rebates instead? Besides, haft of those expenditures are questionable expenses anyway.

[@g33xzi11a]

@@leapdrive Nope that's the great part. We live in an age of such plenty that we can luxuriate in new discovery without worrying if we're going to all die of famine because these people aren't toiling in the grain fields instead of advancing knowledge in centers of learning. Take joy in the time and place of your existence instead of being a small-minded person who falls for anti-intellectualist ploys based on nonsense deficit hawking. What a miserable world it would be if all the answers were already known or we gave into mental laziness of not looking at all or substituting reality for bronze age propaganda.

[@KaiHenningsen]

@@leapdrive If you want the government to spend less money, take a hard look at military spending. It's one of the most wasteful areas of spending. Also, make sure your taxes are progressive (that is, the rate goes up when the income goes up).

[@leapdrive]

@@KaiHenningsen , we have to start somewhere.

[@fromagefrizzbizz9377]

The chart you used to show the different measurements of gravity looks like an article I've seen. Towards the end of the article, it suggested that we may know a lot more about G varying with time fairly shortly. They were referring to the Apollo Lunar Laser Ranging project running at Apache Point. Up until now, their best distance measurements had a resolution of about a centimetre. Apollo has been going through a number of upgrades that are hoped to improve the resolution down to millimetres - one part in 350x10^9. The suggestion is that these upgrades *may* demonstrate that the moon is retreating a bit faster than the other factors can account for, and possibly imply G is getting smaller.

[@PsRohrbaugh]

I feel like there must be some equivalent to red shift and blue shift with all the fundamental forces, not just em. It may appear across a different dimension (IE time vs space) or density or something. A third-party observer sees two black holes heading directly towards each other, each traveling at 60% the speed of light towards the other. What is the gravitational nature of this situation?

[@simonklein4687]

Great topic, perfectly dealt with. With you, I can actually grasp these big questions, although I am not nearly smart enough. You just walk me through, thank you.

[@scialomy]

I can't put my finger on it, but there was something in the way you presented this video that made me enjoy it way more than usual. It was flowing with ease. It was clear. It kept my intereset each second from start to finish. Thank you :)

[@bobaldo2339]

Her personality!

[@hyfy-tr2jy]

Dr Becky.... I know of one unchanging constant! That is the consistent and uncompromising quality of your content!

[@dr4d1s]

Oh, you! Lol

[@jamesengland7461]

and bloopers :)

[@chillpillology]

🤮🤮🤮

[@jamesengland7461]

A compliment, unappreciated. Valid nonetheless.

[@wayneyadams]

Thank you for providing the links to the papers you reference in your video; it saves so much time searching for them then trying to find sites where they are free.

[@rubiks6]

This discussion touches directly the veracity of the cosmological principle. The cosmological principle is a principle, not a fact. The cosmological principle is an assumption that _may not_ be true. It is important to know your assumptions. This was a great discussion, Dr. Becky. Thanks.

[@markfergerson2145]

Yep. I only believe in two things; the laws of thermodynamics and the cosmological principle, because so far they're basically untestable on very large scales and times. Everything else is pretty much testable and don't need belief. ;>)

[@rubiks6]

@@markfergerson2145 - The universe becomes much more interesting when you let go of these unwarranted assumptions.

[@RideAcrossTheRiver]

@@rubiks6 You were bored by the universe at an earlier time for you--?

[@rubiks6]

@@RideAcrossTheRiver - I have always been fascinated by the universe. I was so fascinated I wanted to figure out who made it and I did. Now I know that the universe did not come from nothing like in the Big Bang story but that it has a Creator who has the wisdom and power and desire to create this universe and put us in it and He has a purpose for the universe and for us. No, I don't think I've ever been bored by the universe but I disagree with the cosmological principle. I believe the person who has the power and wisdom to create this universe and invent the laws of physics that we are discovering also has the ability to change those laws in various times and places to suit his purposes. Therefore I cannot agree that the universe is homogeneous and isotropic in space and time. Even you, if you believe in the Big Bang, cannot accept the cosmological principle because in the Big Bang narrative there was a "time" (I have no better term) and "place" (again, I have no better term) where space/time and the very laws of physics themselves did not exist. That right there breaks the cosmological principle. Our universe needs a sufficient cause to exist and that cause does exist and has made Himself discoverable. The Big Bang is woefully insufficient to be the cause of our universe. Time and chance are also woefully insufficient to be the cause. Someone with the wisdom and power and desire to create this universe is the cause of this universe's existence. That Someone is exquisitely fascinating.

[@RideAcrossTheRiver]

​@@rubiks6 "The Big Bang is woefully insufficient to be the cause of our universe" It's the explanation, however, that fits all evidence and data; whereas your long-winded need for a father figure does not explain anything. Also, you have the 'Big Bang' theory all wrong. Your mistake: the theory does not in any way state or even hint at a 'before'. The theory explains only the origin of all that we observe today. "I cannot agree that the universe is homogeneous and isotropic in space and time" It wasn't. Your second mistake. "That Someone is exquisitely fascinating." That someone exists in your imagination. Show us a sample of it.

[@davidkeller6334]

Dr. Becks you are one of my favorite smart people. Thanks for being a smarty pants on youtube, always a good watch

[@rob-v1y]

Now this is some great stuff! Been watching you since way back at 60 Symbols and this is maybe the best ...other than the Brian May material. Also so good to see someone so happy, enthusiastic and immersed in their chosen field in these...times. Can't wait for your takes on JW when it comes on line.

[@一妄一語]

사랑합니다. 당신의 그 열정을 사랑합니다. 영어 한마디 못하는 저에게까지 전해질 정도의 열정! "과학이 얼마나 재밌는데?!" 라고 말하는 그 열정! 3년 안에 당신의 채널을 유튜브영어자막의 도움을 받아 알아들을 수 있는 게 제 목표입니다. 그 때가 얼른 와서 영어로 감사댓글을 남길 수 있으면 좋겠네요.

[@BigZebraCom]

@04:07 I was going to answer all three of these questions...but then things got really busy at work.

[@datchentai3047]

Thank you so much for your excellent and accessible translations/interpretations/explanations of complex but extremely interesting astronomy studies. I am careful about where I am getting my information on the internet and you as a trustworthy source are a rock star in this regard! I hope you will always continue your KZbin program.

[@DataSmithy]

The question I've always to asked myself is, does the gravitational constant change with the expansion of the universe? How would we know if the gravitational constant changed over long time periods?

[@Blesna]

Space is expanding. Not a things in this space expanding, not mass of those objects are increasing. Things in space make gravity. Thing that have mass is producing gravity. If you expand space, mass of objects inside of space will not change. Volume of thing may change, but not the mass.

[@stargazer7644]

Because when you look far away in space, you're looking long ago in time. If G was changing over time, distant objects long ago would behave differently than nearby ones recently.

[@georgejacob6378]

Dr. B....thanks for doing this...explaining complex concept s with reference to the actual theories behind them without dumping down is really engaging ....and your obvious enthusiasm and excitement in matters astrophysics is infectious

[@TechCOG]

Great video, you did a great job explaining the current status on the value of G

[@rosellabill]

My brain is SORE. But I would never have thought of different types of gravity if I did not watch this. I appreciate all of your videos.

[@MaryAnnNytowl]

I'm glad you aren't afraid to dive into these issues, and that you are so good at explaining the possibilities to us, too! Thank you for what you do, Dr. Becky!

[@edmcbroom7836]

Thanks for the very interesting video. My question: your first topic especially depends on light being constant. If G changes, isn’t it also possible that the speed of light might vary as well or not be the same in all directions? Thanks for all the work you do on your channel.

[@g33xzi11a]

I think the m in E = MC^2 is the inertial mass not the gravitational mass. It so happens that in General relativity these two values are the same, but that needn't necessarily be the case.

[@trevorhallewell]

I’m not sure if you’ve seen it, but Veritasium has a really interesting KZbin video about that very question. He even quotes Einstein when he came up with the theory of Relativity roughly saying that he took some liberties to assume the speed of light was the same in both directions but that it wasn’t actually possible to prove. Honestly most of it went over my head but it was very interesting nonetheless. You should check it out if you haven’t yet. It’s called, “why no one has measured the speed of light yet”. He talks about what the implications of this could be to the future of physics. Let me know what you think!

[@PatrickPoet]

This is my favorite sort of post from you where you talk about the problems and conflicts between current theory and observations. Either observations are wrong or theory or both. That puts us in the fun zone as thinkers:)

[@oscresson]

We're fortunate to have people like you investing your lives in topics like this so you can summarize it for us! More power to you!!

[@robertroy1878]

Always pleasant to spend time with Dr. Becky. It's been a long day, this was a nice way to relax.

[@crazyspace6792]

Fast becoming my favorite Physics channel. I feel like you bring up really important and interesting questions in all of your videos. You also explain the topic well for both those without any physics background and those with a physics background.

[@MAGA_Extremist]

You deserve millions of subscribers.

[@luudest]

Btw.: Are gravitational waves also red shifted?

[@Feefa99]

They should be, I think some measurements could point out to better expansion of the universe

[@andreja5521]

if they are loosing their energy ? yes, they do, they are loosing energy to expansion of the universe, to matter (galaxies and stuff like that) and to other gravitational waves

[@francb1276]

A fantasic channel which is a pleasure and an education to watch. Thanks Becky for your efforts and obvious enthusiasm! Just to nitpick, I take issue with the equation at 0:28, which I feel has one too many "10^-11"s in the last line... 😉

[@radekc5325]

I have this question: If gravity is mediated by hypothetical graviton, shouldn't expanding universe cause the gravitons to be, um, "red-shifted" between galaxies, as the space is stretching them on the "journey" (just like CMB photons)? Which then should make the gravity (but not G constant) weaker on the large scale?

[@Rosyna]

General relativity disallows a force carrier, such as gravitons and graviolis, from existing.

[@hamjudo]

Gravity gets weaker with distance. The "redshift" was in Newton's law of gravity from the very beginning.

[@WhiteTeeTurnip]

So gravity isn't actually a force its a curve in space time. Time dialation is the reason an apple "falls" to earth.

[@WhiteTeeTurnip]

@@hamjudo the further away it is the greater the time dialation and the smaller the curce in space time.

[@RideAcrossTheRiver]

@@WhiteTeeTurnip Space curve.

[@DarkskiesSiren]

Such an amazing video on G. Your content is always very engaging mentally and in every other way, your voice and your face are absolutely beautiful. Definitely subbed for life!

[@Age_of_Apocalypse]

For the Star Trek fans, we knew about changing the gravitational constant because Q said to Geordi Laforge in an episode: 'Simple. Change the gravitational constant of the universe.' The Q are able to do it! Ok, ok, it's in a sci-fi episode, but ... 🤔😉

[@DrBecky]

🖖

[@marcusdirk]

I was going to quote this, and ask for an "Astrophysicist Reacts" to the episode, Star Trek: The Next Generation _Deja_ _Q_ .

[@peterkelley6344]

And to think the Star Trek Franchise came on this first. Will they get the credit?

[@adamhaze8477]

@Portal Opener An entree sized bowl of Word and Link soup - yum!

[@friedhelmmunker7284]

QAnton... I buy me an Aluminium foil. 😉🖖😂

[@Drewdo1128]

OMG. This was the best explanation I've seen on dark matter and energy! Also I loved your"blooper reel" it was so cute!

[@merendell]

You know it would be intresting seeing a similar video on some of the other constants. For example what would brake and how in our models if C wasn't as constant as we believe? Particularly if C varried over larger stretches of time could that explain some of the dark energy?

[@johnstonewall917]

My thoughts also.

[@Michael75579]

There are limits on how much c can vary as well. For example, at Oklo in Gabon, uranium-bearing rocks formed a natural nuclear reactor around 1.7 billion years ago. The equations describing the reactions and results include c, so we know c hasn't measurably changed over the last 1.7 billion years; at least not locally.

[@vornamenachname2625]

C is actual not a natural constant. The arbitrary definition of meter and second given C its value. If you "vary" C you would directly vary the spacetime itself. If you slow down C you see an expansion of space, if you speed up C you see a contraction of space.

[@Mark_Bridges]

@@vornamenachname2625 You can say the same for G, however it seems there is a chance it might vary based on this video. Your response doesn't explain why c can't vary too.

[@johncaldwell695]

@@vornamenachname2625 c, the velocity of light in vacuo, is described by the permitivity and permeability of free space according to the Maxwell-Heavyside equations, so one might say that c is not a natural constant. Changes in c imply that either the permitivity and/or the permeability of free space are different from what is measured on earth at the present. Or, of course, if the Maxwell-Heavyside equations are not quite correct, as some people suggest, in the same way that the equations of relativity are known to be not quite completely correct. Some of these people are capable of either proving this suggestion or confirming that the Maxwell-Heavyside equations are actually correct in all circumstances. Note that the Maxwell-Heavyside equations do a pretty good job here on earth, as do Newton's laws.

[@richardgreen7225]

Are the ratios between gravity-charge "mass", inertial "mass", and nuclear (E = m c^2) mass constant? Solving Kepler's observations, Newton assumed that 'm' in F = m a ... was the same as 'm' in F = G M m / r^2. There is also an implicit assumption that 'm' in E = m c^2 ... which is really only tested for nuclear mass ... will sum up to the macro 'm' we see in macro equations such as F = G M m / r^2.

[@johnsykes9795]

From a layman writer's point of view, I've sometimes wondered whether the force of gravity could become geometrically stronger to a very small degree in the presence of many gravitational fields. rather than arithmetically. So the G of a galaxy cluster would be more than the sum of its parts -- or individual fields -- to a greater extent than a galaxy. Could the cumulative gravity of the Solar system be very slightly higher than the arithmetical value of the sum of the gravitational fields of the sun, planets, and sub-planet bodies on each other. I guess what I'm asking is do gravitational fields possibly boost or suppress the gravitational effects on another body. How could you test that? Er... asking for a friend. Not me. I wouldnt want to use that idea in a sci-fi story. I dont even write sci-fi. In fact I don't even write. Perish the thought. Er... I'm not even here. It wasn't me?

[@jerelull9629]

Your enthusiasm is infectious.

[@jmacd8817]

Hey, cool vid! But, I have a question… If G is different across space or time, and we are looking at astrophysical phenomena, such as accepted values for luminosity, color and energy output for certain stellar types, wouldn’t a different value of G also cause those “currently accepted values” to be different? For example, a lower value of G would, in turn reduce th gravitational forces inside a white dwarf before a type 1-a supernova occurs, which would, in turn change the amount of mass needed before the explosion, which would make a physically larger star, changing the luminosity/brightness ratio, and throwing the standard candle value out the window? Or was this taken into account, and the proper calculations done? To;dr - it seems like these “direct measurements “ taken to determine G, are directly impacted by any potential change in G being investigated.

[@markfergerson2145]

There's also spectral redshift due to light from an object having to climb out of the object's gravity well. If G changes the redshift changes. We'd have noticed.

[@bebop.]

This is correct. These effects are also taken into account in studies (usually).

[@frankvanderpool9001]

I tried to be funny with my last comment yesterday. It was confusing but I meant only good things. Dr. Becky, you're awesome and very enlightening. I mean it when I say thank you for increasing our understanding through your own work and from clarifying other papers on scientific and astronomical matters.

[@Dan-56]

I’m still trying to wrap my head around the fact that your refrigerator magnet is stronger than the force that is keeping me from floating off the surface of the earth 😳……

[@Reyajh]

Pound for pound there, is the key 😜

[@hamjudo]

If I pet my cat on a dry day, I will end up with a static charge stronger than gravity. It is so mind bending that my hair sticks out like I am in a cartoon.

[@shanent5793]

It's not true. Try lifting 65 kg with a fridge magnet.

[@Mark_Bridges]

@@shanent5793 Your example of a 65 kg weight doesn't make the original comment not true. The point is gravity is much weaker than magnetism, which is unquestionably true. To go back to your example, you can pick up 65 kg of steel with a magnet weighing no more than a few hundred kg, against gravity from the earth that weighs a whole lot more than the magnet. No matter what your steel weight is, the magnet that can pick it up weighs much less than the earth or whatever makes the gravity.

[@shanent5793]

@@Mark_Bridges Distance matters. Compare the distance at which the magnet starts to attract against the distance to the Earth's centre of mass. In what common units would you compare the respective strengths?

[@larsblakrasmussen5820]

WOW, finally! "Dark-" things gets an understandable explanation, I LOVE it :-D

[@jannikheidemann3805]

Understanding that we don't understand is a step closer to truth.

[@sharvanimohare51]

Dr becky you're amazing!!! Completely irrelevant but.... I've recently started reading about quantum mechanics and am currently reading about quantum entanglement and the EPR paradox! Although we have evidence that says extra information about particles cannot exist more than we already know like einstine thought and assumed it was predetermined I still somehow would love to believe his theory coz it sounds very interesting. But yeah I'm loving quantum mechanics. I would love to hear what you think! Thanks

[@stewie9735]

Hi Dr. Becky I love your videos so much, because you make very difficult concepts and ideas more understandable. I was wondering if you could make a video about your reasearch and/or writing process for either these videos, or scienctic papers you have published?

[@VideoNOLA]

Regardless of the answer, one must ask, "How do all the parts of our Universe 'know' how to behave?" Who phoned ahead to inform every object of the various physical constants? 😀

[@web4639]

The rules were set and "communicated" to all the parts of space before everything flew apart shortly after the big bang (vvv shortly after)

[@vigilantcosmicpenguin8721]

The quality assurance department of the physical laws team is hard at work.

[@Pershoreify]

how do you separate question 1 and question 2, given that when you look out in distance you are also looking back in time?

[@jursamaj]

I wished she'd have spent a little more time explaining how measurement of G in distant galaxies/times doesn't rely on the assumption that G is constant. Otherwise, it's a circular argument.

[@rogerclarke7407]

I was thinking along the similar line. If mass is determined by its interaction with gravity then how would we determine mass independent of gravity?

[@IamGrimalkin]

Well, it'll depend on which measurement of G you are tlakkng about, there are many different measurements with different methods in this video.

[@jonka1]

Roger Clark Possibly by looking at its inertia

[@jursamaj]

​@@IamGrimalkin Point is, none of what was shown actually made it clear how each method wasn't circular. It would have been nice to get that for *any* of them.

[@RideAcrossTheRiver]

@@rogerclarke7407 Mass is determined by matter. WEIGHT is determined by gravity and mass

[@lulugurl6547]

Thank you Dr. Becky. I love your enthusiasm. The topics you cover are always interesting! Much love from Michigan USA 🥰

[@iamo0]

I might sound stupid but after this video I can't stop thinking about the fact that we doesn't know speed of light, we only measured it making a roundtrip and we don't know whether it's always c or c/2 in one direction and infinity in other so measuring something using speed of light (e.g. gravitational effects on distant objects) we should take it into consideration, because in case it's infinity on there way back, we're looking at distant galaxies as they are now, so we won't see any difference in gravity but it doesn't say anything about those effects in the past.

[@irishlad6444]

How would the plank length factor into the expansion rate of the universe. Would it not have to expand at a plank lengths increment as a function of time?

[@DesertRat332]

I don't understand why we assume that time (i.e. the size of a second) has stayed constant throughout the age of the Universe. Isn't time part of the space-time continuum? If space is expanding shouldn't time be expanding also? Maybe things formed quicker in the earlier universe because of a smaller unit of time?

[@andreja5521]

time=light, E=mc^2 you just saying the speed of light vary, and that's a possibility

[@agawarrior]

Really enjoy your content and attention to research updates. You have become my place to go when seeking the latest astrophysics journeys. Thank you Dr. Becky

[@diniaadil6154]

I love this channel because it makes me feel smarter than I really am

[@kylekataryn3454]

you are smarter than you know. many people lack the time, opportunity to investigate. how fortunate are we to live in a time when knowledge is so ubuiquitously accessable?

[@TheNewPhysics]

At 15:47, Dr. Becky says that the fitting fits well with varying G because "it is General Relativity"; in other words, if you don't change the observations that are model-dependent (e.g., SN1a distances using the Stellar Candles Hypothesis - this is a constant-G model since SN1a detonates when they reach the Chandrasekhar Mass Limit and that has a G^{-3/2} dependence). So, if you don't change the SN1a data, you will not change the Cosmic Distance Ladders. OBVIOUSLY, G will only be allowed to change a little since it is constrained by data that was collected using constant G. So, it is the pinnacle of Confirmation Bias that is hitting Dr. Becky at 15:47...:) That explains the smile...:) It is Pure, uncut, fishscale Confirmation Bias... I corrected that by deriving the SN1a G-Dependence, something that, somehow, people couldn't do because they are a member of a cult.

[@aedwardsss]

You have fast become one of my top three favorite science lecturers

[@davemmar]

Just a simple demonstration of the weakness of gravity using a magnet and a bobby pin allows for your whole discussion. The numbers using many decimal places can be pictured with more relevancy once the effect of gravity is observed. Your breakdown of the different camps investigating this science is spot on. But then your understanding of this subject and your ability to convey it is very much appreciated.

[@bjornfeuerbacher5514]

2:12: First, the equation on the left hand side does not describe magnetism, but the electrostatic force. Second, if you divide k by G, you don't simply get a dimensionless number, but a number with the unit kg²/C². So you can't use this number to compare the relative strenghts of electromagnetism and gravity!

[@wadeedden4552]

Thank you, as I was asking myself that question recently. I’m embarrassed if I saw your post last year and didn’t remember your video.

[@dragonssmile]

Also perhaps Question 4. Does the strength of gravity vary with velocity through spacetime. Kind of like time friction since velocity and time are tied together. The "stretched sheet" image does look some what like the flow lines around a airfoil.

[@danielpeters9110]

I've heard that only dimensionless constants can be considered to vary. Since G has dimensions can it actually vary, or is it something dimensionless like the relative strength gravity vs the other forces that would actually vary?

[@acleedsunited]

Brilliant science communication Dr Becky. Explaining Astrophysics in a way people understand without being patronising and still remaining humble. Your videos are very educational and entertaining. It's tragically sad, that some people actually make Flat Earth videos by contrast.

[@WayneBorean]

Love the magnet explanation, I’d never thought of it that way before. Thanks once again for expanding my mind.

[@dinkoz1]

Problem whit long range measurement by observing distant objects as opposed to "local" is that the conditions of occurrence of observed events are different from our observational position, let's call it "time frame", ie space-time conditions are different due to the difference of gravitational field and object real velocities of the observed object, differences in relative speed between the observed distant object and the place of observation. Because the speed of light is constant, gravitational conditions are different in terms of space curvature which means that events of remote observed body and measurement position differ in terms of time ie hapoening in different "time frame". Since the estimation of the mass of measuring objects is estimated on the basis of assumptions and predictions known to us now, it is difficult to obtain a relevant accurate result without a major error in measurement.

[@anthonyrobertson2011]

Not too shabby on the singing abilities there.

[@leighcoulson2148]

I have thought of this quite a bit ...nice to see a video looking at it.

[@ArtisticImpressionsbyBobRouth]

Dr. Becky, Your the best! Does the effect of gravity vary with the rotation of the objects being affected?

[@griffinsmith3760]

Im a fan of Dr Becky I watch all her videos, but I have not a clue what she talks about but it’s so interesting !

[@curtisblake261]

We can make any universal constant 1 and adjust the units accordingly. We commonly see c=1 to simplify calculations. I keep meaning to try setting each constant to 1, and comparing the resulting units in terms of other constants. Will get around to it one of these days. A round tuit even.

[@Iearnwithme]

amazing video, best physics video I have watched in a while!

[@alexanderhilary]

Dr Becky thank you for your efforts! I learned.

[@galgone365]

This was really interesting and fun to watch, thanks for this video.

[@revel8r413]

Thank you @DrBecky! A couple months ago, I had asked you if the laws of physics were mutable over space and time. This helps answer part of it - the gravity part anyway. Thanks again!

[@alnilam2151]

As a northern hemisphere resident and your topic on the southern aspect of our galaxy with a view? Indeed our galaxy is something to behold: let me just get my head round that proportionally galactic arc! Appreciated DrBecky

[@peNdantry]

Fascinating, Dr Becky! Thank you so much for this; I'm particularly interested because it all has a bearing on a novel I was trying to write (a long, long time ago, now). I gave up on it because I couldn't get my head around one of the central ideas - I called it 'slanted light' - which posited that gravity in between stars was very much lower than near a large mass. If this were true, then it would, I think, completely alter our perception of the scale of the universe. Light would struggle (relatively speaking, pardon the pun) to get beyond its originating star's gravity well, but once in interstellar space, it would just sort of -zip- through space to the next star (... I think?); and because we assume that gravity is constant everywhere, the result is that we are led to believe that other stars are incredibly far away... but perhaps, just perhaps, they're very much closer. The Voyager probes, now beyond the heliosphere, have, I understand, provided some indications of strangeness out there... but I'm no astrophysicist (and because I love this pet theory I naturally grasp at any straws that might hint that there's actually something to it!) Your 'question #2' has a direct bearing on all of this, but your description here of the research in that area focuses on the strength of gravity *near other stars* far away... which is of course not the same thing as the question of whether gravity *between* stars is different. I'm really sorry if that's all utter nonsense! :)

[@1kreature]

What worries me is we use red shift and absorption lines in spectrums to gauge distances with tools like standard candles, but when/if G starts to change won't that throw a wrench into the math? If we can't distinguish between G changing or space stretching vs "the measuring stick" then how can we unravel this? (This worry is so hard to put into words...) Maybe it would be a good topic for a video? How can we know what we are measuring when we are trying to test if our measuring stick is changing?

[@adandap]

A question: if you are setting out to test variations in parameters like G, how do you use data from supernovae "that always explode with the same brightness" when other coupling constants (strong interaction, electroweak couplings, Planck's constant and c) are also involved in the process?

[@passerby4507]

10:34 What _does_ make you be able to shout from the rooftop though?

[@gregspecht3706]

I love the passion you present with. one thought that came to mind is that as light waves travel through space and are stretched they appear to us as lower frequency light. when gravity travels through space wouldn't it be stretched as well so what effect would it have on gravity? or maybe that doesn't make sense.

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

Another logical question you could ask is does the strength of gravity vary with the phase changes of matter. We could have gravity relative to the structure of plasma at large scales forming the characteristics of dark energy.

[@EyesOfByes]

2:02 What about the centrifugal/centripetal force?

[@richardl6751]

At 1:15 - 1:25 Why did the device reverse direction?

[@TheDMFW62]

I really enjoyed this one. A nice clear logical exposition on a fascinating topic I've kind of idly wondered about before, and just when I was thinking "but what if it varied with x?", the question got addressed, which is always nice! Now, I suppose the same question might be asked of the other force constants (perhaps not so much with distance and scale but certainly with time). If nuclear physics was different in the early universe due to differences in the electroweak or strong force, that would surely influence stellar physics in the early universe. I wonder if that would be detectable?

[@EdTube444]

Glad to hear a credible scientist say this. I've been saying this for decades since the AOL Chatroom days. For all we know at the decimal place we haven't measured yet, we will call it Xth decimal place of G and C and maybe even Fine Structure Constant is "evaporating" slowly. Until in say 1x 10⁴⁰⁰ years everything just dissolves.

[@raghu45]

Dr Becky!?? U've confused me! 🤔 At 0:25 shouldn't the 2nd value of G (under i.e.) have just 10 to the minus 1 & not minus 11?

[@Sad_King_Billy]

This might be my new favorite Dr Becky video

[@infidelcastro5129]

What a wonderfully informative video. Thanks Dr Becky 😊

[@JuriRadov]

I dont understand 6:43 . Assuming gravity changes with the upper bound of 0.1 parts in 1 billion per year over 9 billion years would mean a change of 0.9 in total (just multiplied them together). If I calculate it with exponential growth/decay I get 2.45 / 0.4. Can somebody help me?

[@gpcexplorer]

Thaks so much for this video :D Becky. I always wandered if a change in the value of gravity could explain all the issues with the missing matter of galaxies. Now I have a clearer picture.

[@michaelgian2649]

@ 1:13 Maybe time, also, doesn't have a constant rate (in specific media) throughout the space-time continuum.

[@touisbetterthanpi]

Great video! Wish you had talked a bit more about gravity varying with scale, with relatively tiny object, and questions about if gravity is quantized or not

[@das_it_mane]

This is an incredible video. Such a fascinating topic

[@susanlemmey4012]

After binge watching your vids my general understanding of the base concepts has been vastly improved. So thank you for your amazing content and hope you continue to provide quality science 'for the masses' into the future. A question has occurred to me that I am not sure anyone has the answer to yet. Is the Universe expanding faster as it gets older 'because' the spaces and voids between galaxies and galaxy clusters is larger the older the Universe is? AKA a feed back loop. a void is big enough to overpower gravity so it expends and the larger it expends to the faster it expands. A possible way to test this would to study if a smaller void at the same distance is expanding at the same rate as a super void at the same relative distance from our perspective. Another concept that is spawned from thinking about this is: If gravity and the dark energy are interacting fields where the mass of 'objects' in the Universe cause gravity to put 'friction' on the dark energy field slowing or even overpowering its effect. Furthermore could this 'battle' between Dark energy and gravity be the reason (or at least in part) for why gravity is so much weaker than the known fundamental forces? Edit: Still thinking about it and since energy can not be created nor destroyed, then could the darky energy 'energy budget' become spent? Could there be a point at which Dark energy can no longer stretch out or expand an 'empty' section of Universe?

[@tonynicholls]

Excellent content as usual - really love your work. One question that arises from this is "Do we know whether the Higgs field is constant?" My superficial understanding of the Higgs field is that is the interaction of the Higgs that gives particles mass. If the Higgs field is not constant would the same particles have different masses? Again over the same three questions as your variance of G: time, position and scale?

[@flatisland]

just wondering. have they checked for variations of gravity with the other SI base units like temperature und luminosity?