We can see things moving faster than light 

I'm curious: why wasn't the Hubble Sphere called the Hubble Bubble? How much toil and trouble would it be to change the name?

I wanted to call this series "In here 🧠 Out there 🌿"

Damn I think I actually understood that. It's a bit like a car moving north at 60mph and you jump off south. Even though you jump south, you're still going north. Same thing with the light. It leaves the distant object still moving away from us, but eventually it works it's way to moving toward us at the speed of light

Thanks for the great explanation! Something which always bended my mind. I would love a follow-up, where you explain how during a Big Rip, one of the horizons gets closer until light from even say Andromeda wouldn't reach us anymore, while the observable universe still gets larger as time since the Big Bang increases. I'm still a bit confused about that, how that works.

6:05 *"The space between two objects can expand such that it moves those objects apart faster than the speed of light."* This is perfectly worded. It acknowledges that it _is_ a speed (distance over time) while still highlighting the difference from what we would normally consider a speed.

The concept of light traveling towards us while also moving away from us as space expands reminds me of trying to walk the opposite way on an escalator...although I'm sure it's quite a bit more complicated than that analogy, if I understood anything from this video

I’m a huge fan of all things science and Physics Girl. She’s a great science communicator and I look forward to watching her career unfold over the coming years. Live long and prosper.

I love everything space related and the way you put it for us not so smart folks is just great! Keep doing what you’re doing. Ps. How can I steal your editors job?! I would LOVE to learn on the job lol

Wait, so does that mean that, even if it were possible, we would never be able to see the “edge” of the universe because it’s moving away faster than the speed of light? Or am I misunderstanding?

During the ad, she says that I probably have a 3M product in arms reach. Since I'm physically at 3M Center (I work here) this is absolutely true.

you explaining top him and awnsering his questions made it way more easy to understand . great teaching technique .

Wow, You just made the LED light in my head go on! Thank you Physics Girl. You helped me understand the relationship between observed distance based on light speed travel time and the adjusted distance based on the expansion! Cool video! (Yes, 6 months late in responding but I just discovered you on RU-vid). Catching up. (I think I may understand that Cosmic Event Horizon now: The Hubble Sphere is like a faster “shock wave” overtaking the slower “shock wave” of the CEH yet never catching up with it, yielding the effect of light in the CEH appearing to move away initially but eventually appearing to move towards us? Is that a change in the red shift? Or am I way off the mark?

Just imagine the wonders and poetry of deep space . No limitations. As Stephen hawking once said " There should be no boundaries to human endeavor. We are all different. However bad life may seem, there is always something you can do, and succeed at. While there's life, there is hope."

Your editor sounds really smart

I always liked the example of walking on a travelator (flat escalator). You can only move along the travelator at the speed of light, but the fact that it itself is moving, means the sum total is moving faster away from the start point.

Does each planet in the universe have its own hubble sphere? In other words, if we were on a distant planet outside of Earth's Hubble sphere, would Earth appear to be the one that was moving away faster than the speed of light?

Just when you think you're beginning to understand the universe it humbles you and you've got to rethink everything. Love your videos. Thanks for sharing this knowledge.

Fun fact: If the universe was expanding at a constant rate instead of an accelerating rate, then there would be no event horizon; light from every object would eventually reach us. This is called the "ant on the rubber rope" puzzle

I'm just going to watch your videos again. I've always enjoyed learning from you. Rest as much as you need but please don't quit. I'm sending good vibes your way. ♥

For the first time in my RU-vid activity, I watched a sponsor time in its entirety! That new 3M tape is actually pretty awesome! About the video itself, amazing content as always! Mind-bending science always amazes me! Thank you!

Mr. Editor: you didn’t give her the slide transition! Awwwww.

I live in Argentina. My 10 year old daughter loved your video but she relied on my translation to understand it. You should make a channel with a Spanish translator in the audio. You would capture many children and adolescents in these latitudes. You have a great way to spread science. Keep it up.

You are so good at this. Your delivery is so absorbing. Well done

Physics Girl, you are awesome! Thank you for making complex physics understandable. One question, if we are at the center of the observable universe then where is the actual center of the universe and is there anything there if everything is expanding away from that point? Sincerely, Dr. B.

I am currently attending school at south Albany highschool in Oregon, I was told by my physics 2 teacher mrs.Jones that this girl went to the same highschool and was taught by the same instructor. It’s great to know I have such an amazing physics teacher who can mold minds as great as the one we see in this video!

5:30 There once was a girl who was bright She could travel much faster than light She set off one day, in a relative way And returned the previous night. Perhaps the bright girl was Physics Girl.

Seriously LOVE the way you explain these things! It makes sense that galaxies are moving through space but I have never understood the concept of ‘space itself is expanding’. How does that work? And how can I ever have a sealed container if the space within it is what is supposed to be expanding? I wish I could have lunch with you to pick your brain! When you are looking into space and see reflections and distortions caused by gravitational lensing, how do you know what is real and what is a reflection? Some of the images from Hubble that show gravitational lensing seem to have near symmetry, but lensing makes it difficult to know, when just looking at the images. Could/does gravitational lensing cause us to misunderstand what we are seeing so much so that we conclude that everything is moving away at an increasing rate and almost everything is morning ‘away’ so even the fabric of space must be expanding? Or is there possibly a large ‘lens’ (maybe due to the sun, galactic center, dark matter, etc.) see is reflection of reality? Just like when a car drives by a distorted window and the image gets stretched out and quickly wraps around the arc of the distortion in the glass…Hypothetically, if some of the galaxies we see are reflections like I mention above, how does that change our perception of doppler shift? Ok ok maybeeee 12 lunches =]

0:54 , my take: The 'universe' is a giant explosion; everything is in constant fluctuation, nothing is stagnant. the light that started moving towards us X billion years ago, carrying an image of what it had bounced off of (which is crazy, if you think about it.) might be reaching us now; but whatever it is showing us, has moved, since then (relatively - since the universe is in expansion. - it may have stayed 'in orbit' during that time. ) - and has been doing so for the same number of years the light we see has been travelling. (An aside thought; if the space between two objects expands, is that any different from them carrying a velocity that moved them 'apart'? - and if it was, could you tell? ... Curious.)

This has just become my "go-to" method for persuading people that I'm smart. Great video; clearly explained; with good use of props and diagrams to illustrate potentially confusing concepts. 5 STARS! Sorry, I couldn't help myself. Granting stars on an astrophysics or cosmology video is empowering.

She's so giddy when she talks about things she loves 😍 That's so cool and inspiring!

This is a very informative episode. It caused me to question the calculations of time and space. The missing ingredient as it relates light and time is an equation called "The Inverse Square law of Light". Which is explained as: Light intensity decreases with distance from source to receiving surface (sink), and the rate of decrease is in proportion to the square of the distance between emitter and receiver. This is called the Inverse Square Law. How do you think this has an effect on the entire question?

Very clear and truly astonishing! thanks so much for helping us understand more.

She’s so passionate about what she is explaining; I love it.

It's great to see your excitement when talking about cosmology , I see it in you and I know how you feel, I am 57 years old and have been into Science, cosmology and space since I was very young after seeing the Moon landings that was the spark for me. It is a lonely subject to be into because in all my years I have had very few deep conversations about cosmology and when you meet someone who wants to listen I just feel like I can't get it all out with the excitement. I still think and watch about cosmology, Science and space every day and am still as excited like you about it all.

I remember as a young teen when there was still a lot of auguring on whats happening that it came out that space was both shrinking and expanding, depending on the areas, but lately all the videos I'v watched all say its only expanding yet I'v never seen anything about it being wrong either. There was a few different pronounced channels that talked about both side being right, just that its doing both and not one or the other.

Thank you for helping me finally get my head around this really tricky topic!

I love how passionate and excited you are about all of this stuff, it is absolutely infectious and your videos are always a joy to watch.

4:38 The Scotchlite is vastly used in motion capture because MotionCap camera takes profit of this specific property to reflect the light in the opposite direction. that's why they have multiple infrared LED around the camera.

3M also known as Minnesota Mining and Manufacturing Company. Their products are amazing and as a jewelry artist I use some of them to make my pieces. Love you 3M! Keep doing what you do best.

Here’s a question for you. Is there a fixed amount of matter in universe? If matter is expanding at a speed of x, then aren’t we also moving at a speed of x? Or, if there was a big bang, a point from which everything started moving away from one another then how is anything moving faster than light? Isn’t it just somethings, relative to earth, are moving directly away from us, somethings move with us and some things move at an angle from us. But everything should either be moving at the same “bang” rate- of-speed or something has to account for why some matter moves faster or lower than other matter and why matter expanding further and further apart is either doing so at a constant, slower or faster rate? Is something pulling it or restricting it or in an empty vacuum does it move effortlessly at a constant rate forever?

9:20 I've been doing some pondering and thinking of it as velocity rather than displacement makes a lot more sense. The Hubble sphere is moving away faster than the light is moving away. Once the hubble sphere overtakes the photon, then the displacement starts decreasing.

I love that sometimes it feels like I'm learning things at the same time as you and that you get as excited about it as I do.

Such as a flashlight reaching out to the expanse of space the further it goes the light frequency gets stretched out. The further in the light travels the frequency gets stretched out you would actually have to take in consideration of the stretch out and have that into the equation to when the light frequency is originally starts to where it gets to its distance

I love the stuff you talk about u would be fun to figure out things you really get heavy.i have not met to many people who be heavy about a subject keep up the good work 👍❤❤

Discovered your channel recently and can't stop watching all your videos! Your passion and enthusiasm is palpable. And your presentation style is a perfectly unique blend of informative, quirky, and fun. Keep up the great work!

11:02 I find it especially touching that Diana appears to value the camera more than physics demonstrations and, possibly, her editor...

This is the first time I've come across one of your videos and I'm loving your enthusiasm here

I now have a pretty good grasp on the concept that everything in space is expanding/accelerating away from everything else in space, but what I don't understand then, is how some galaxies are still merging with other galaxies? i.e.: Isn't The Andromeda Galaxy supposed to be combining with us (The Milky Way Galaxy) in something like three and a half billion years or so? Why isn't Andromeda accelerating away from us like everything else in space is? I can't be the first person to ask this question, but I have never heard an explanation of this seeming 'exception to the expanding universe rule.' I would love for you to do a video explaining these kinds of apparent anomalies as our understanding of our universe continues to grow and mature.

For the light that moves away from us and then back toward us, I'm imagining photons running at a constant speed on a treadmill that slows down over time.

This is the first time ever I hear a physicist saying that engineers are the best scientists. THANKS 3M!

A simple concept for the expansion is from shooting at a moving target. Learning to lead your target and estimate the distance involved is a local example of the same process as galactic motion.

I'm not a physist so . But I listen to all the big names in this field and this mind blower is new to me. My humble point is I didn't know this and thanks for bringing it to my attention. Awsome,, Alex kowaliuk from America 🇺🇸 👌

Thank you!! I've been trying to comprehend this Astronomical stuff for decades...you just explained it in a way I can grasp! I'll watch again several times because I'm getting older & my brain doesn't retain knowledge like it used to...😎

My brain had a hard time understanding the vastness of our universe. I love how you genuinely get excited talking about this topic!

"Relative to us" is a critical phrase here. A person could easily fall into the misconception that all these spheres and bubbles and incoming and outgoing arrows of light around us in the center indicates an Earth-centered universe. It's mind-blowing to remember that everything you're saying about the positions and relationships of all parts of the universe, seen and unseen, and how things are moving slower or faster relative to "us," is true starting from any point in the universe--again, seen or unseen by us.

Thank you! This is a decent explanation why the Hubble sphere is NOT a horizon, although you could have used a slightly more accurate figure of 14.5Gly (z=1.48). However, @11:12 Gravity does NOT overcome the expansion of space. There is not tug-of-war between gravity and expansion. Space simply does NOT expand where it is curved (described by a metric other than the FLRW). The cosmological constant (expansion) is contained only in the FLRW metric which describes flat spacetime.

I ABSOLUTELY LOVE YOU YOUR CONTENT!!!! and so does my granddaughter!!! She’s 5 and we love doing your experiments at home. YOU ROCK!!!

Fantastic video, thanks! I think a more complex graphic would have been really helpful in describing the travel of light from beyond the Hubble sphere - my mind is still trying to put it together!

I hark back to my physics class - 50 years ago. My physics instructor asked us - move relative to what? At 3:46 it says that 97% of the objects are moving away from us. Does that make us the center of the universe? What would the Catholic Church and Copernicus say about that? My physics class was long ago, but Copernicus was NOT a personal acquaintance. As we look all the way back to the beginning (big bang), shouldn’t we be able to look any other direction and see the “other side” of it? Which would be exactly the same thing? I guess I’m saying that any direction we look all the way to the “edge of the universe = the Big Bang,” wouldn’t it all look the same? I saw Destin’s visit. May God bless you on your path to recovery.

The way I understand this concept based on your explanation is that every point in space is the center of its own Hubble sphere, & some galaxies outside of our Hubble sphere have a Hubble sphere that overlaps ours. So although a galaxy itself may be moving away from us at the speed of light, its own light can reach our Hubble sphere, since the perimeter of our sphere is within its sphere; at which point we have the possibility of receiving that light.

Zooms like the one at 0:28 never fail to give me goose bumps. It is astonishing that by simply looking into the depths of the sky we can reconstruct the history of the earth and the whole (expanding) universe. Truly awe-inspiring.

I really like that you speak to the camera man. It's like you are speaking to me directly and most of the time, the camera man is answering what I would say 🙂keep up the good work !

Tanks for explaining such a difficult concept. Thats as I understood it. Best wishes and waiting for your next video.

Ran across this video from a couple years ago. Please recover quickly! Looking forward to your full recovery.

Even though I’m in nursing school right now pursuing my BSN, I love science and more specifically astronomy. The size of the observable universe is truly beyond amazing 🤩

And in another mind blowing concept, every object in the universe has it's own "Hubble sphere". All those photons reaching every other galaxy/star system/planet/molecule that make their way into every other "Hubble sphere" will eventually reach those objects. The light wave doesn't change, just the perception of it and its travel time/distance from every view point it seems. Don't know if that all makes sense.

Dianna, my 10 yr old son and I love your channel. I was always told that objects could not travel faster than the speed of light. I often argued this point with my physics prof (MANY years ago). I said, if the universe is expanding at the speed of light, doesn’t that mean that objects on the opposite side of the universe center are then expanding away from each other at twice this speed of light? Would you consider doing a video discussing the topic of the speed of light and how objects can travel faster than it, and what it means to the objects in our universe? Thanks!!

These explanations are amazing..how can you not fall in love with the science..

I do like the video and your presentation. It's truly down to earth. I remember when I was young of hearing that 60 miles an hour was the limit to the speed man to travel. If someone could travel faster than 60 MPH they wouldn't be able to breathe the air. It seems that man has been breaking barriers as long as we've been conscious. Thank You for giving me more to think about than I had before. Imagination is the key to all things.

I appreciate this video a lot. When I think of the light of stars and galaxies taking so long to reach us, so long that they may no longer be here, it sometimes feels like looking at the ghosts of the universe.

"Turns out the universe was bigger than we thought" That's my quote for today. You blow my mind everytime I listen to you. All I need to know about the universe is that I am the center of it all 😋

You explain things very digestively easy to fall keep it looking great work thank you

Sometimes I wanna cry feeling how little I know. We feel lucky to get such a mentor like you @Physics Girl.

I've wondered this, thanks for explaining in greater detail than my thought!

Physics Girl, your video made me ponder, not only my lack of knowledge about science but also this topic about objects far away moving even further away from us at the speed of light. A question occurred to me. We say that the universe is expanding. Yet, clearly, not EVERYTHING in space, the things that are somewhat close to us, is expanding away from us. For example, if Alpha Centauri was flying away from our solar system at the speed of light, I’m sure I would have heard about it. So, why isn't it? That begs the question: does that means that there’s some sort of demarcation line, a precise distance away where all matter beyond it is travelling away from us? But if you moved a foot closer to us from this line, matter would stay where it is and our relative positions would be stable? This stuff makes my head ache. Thanks, Scott Gahanna, Ohio

The way you explain the expansion of our universe reminds me of a herd of cattle going through a tight spot, the way they disperse after the squeeze or when a bike race starts on a single lane road! Starts slow and congested, continually speeding up and spreading apart, the rider behind using the energy of the ones ahead sot of moving energy backwards while travelling forward! If that makes any sense!

Love your work. It's rare that someone like yourself is charismatic and devoted towards higher learning. Very cool.

I really enjoy your videos and the fresh look at physics they provide. You're like the 'Taryn Southern' of the physics world.

A thought experiment under the assumption the universe is expanding into something considered infinite: Imagine a universe that is expanding into something that is infinite.Then imagine a point where this parricular expanding universe (like raisins in the bread) just finally bursts to become like a residue buildup (ring in a sink) only reaching a certain distance or like an 'edge.' And following this are other series of universes behind this universe that are also in expansion that reach this limit whereby adding to this buildup (edge) until a point where this edge buildup becomes implosive toward the directions where the series of expanding universes are coming from back into their direction with increasing speed, like a big crunch. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-I6PtHagsJMc.html

Ok. That was a really good ad insertion. In fact, it was just about perfect. It told me stuff I had no idea about. It changed my understanding of 3M in a positive way. Because I trust and respect Physics Girl, the person, due to watching all these videos, that trust and respect has passed on to 3M the company. Now, whenever I need stuff, if I see the 3M brand on it, I will be inclined to buy it. I just hope I don't find out later today that 3M is a subsidiary of Nestle. Or vice versa.

Really well presented in an accessible and understandable way, even if my poor brain was hanging onto comprehension by its fingernails! 🤯Thank you for a great video

I've seen so many videos on this topic. And it still melts my mind

Just discovered you. I will follow you from now🥰 Amazing video

When people talk about space itself expanding, I feel there's always something missing from the explanation and I'm left with further questions. Let's start with the basic point: is space, as in the vacuum itself, regarded as made up of something? Of units of something? Is it imagined there is some sort of a "vacuum particle"? And in case that is the case, then what is suggested to occur during its expansion? Are the units of space multiplying or just getting further away from one another? Because if it's the second option, why would that even be perceptual to us or to our instruments, considering that only points of actual space should be able to occupy matter and energy, and thus points of "space between the space"-a no-space of sorts-should have no effect on the incoming light that doesn't actually interact with them - because there's nothing to interact with? Unless there's a third option, the belief that two points of space getting further away from each other indeed _won't_ allow light to actually occupy any new point in-between them, but that an increasing (or decreasing for that matter) distance _does_ change the (*relative) time it takes a photon to proceed from one "space particle" to another? _*Relative_ of course referring to the fact that if such phenomenon does actually exist, its effect should only be perceptible when looking at light coming through mediums of space-densities different to ours, as space within a locality being scaled up or down possibly scales all local physics in a way that keeps perception parallel.

I love it when you blow my mind. Going to have to watch this again but it’s filled with fascinating concepts.

Due to the constraints of measurement in regards to light and time, we are always looking into the past because, everything you see when you see it, is not where it was when it emitted or reflected the light that allows its visible presence to be detected.

I followed till expanding universe and hubble sphere/expansion, but when she explains light initially moving away from us and then entering back hubble sphere broke my head lol, well she assured us it doesn't make sense ha ha, so that's there. Love her videos, I hope she sees a speedy recovery. We need more content creators like this.

Obviously this was posted a long time ago, but if anyone knows lmk So the whole idea of the light from things that are moving faster than the speed of light away from us works likes this, the object emits light because it isn’t moving through space faster than light therefore light can interact with it that light then travels towards us and at first it is traveling “away” from us because the momentum of the object it was emitted from + the speed of the expansion of the universe exceeds the speed of light then over time the light itself reduces the velocity by going in the opposite direction until the over all momentum of the light itself is now faster than the expansion of the universe in the direction of earth it then travels through space faster than space expands allowing us to see the object, but for things outside the observable universe the Hubble sphere or things we can reach will all disappear and cool down before that light could theoretically reach us. Also disregard the word momentum since light is mass less it can’t have momentum but I feel like the idea is similar tl;dr light has to over come the extra speed of the actual movement of the object before it can start to overcome the expansion of space on its journey to get to us since movement of object + the speed of the expansion of space is faster than light if not please explain cuz I don’t fully get it

This format is really great, you should do more of it!

Signed my kids up for STEM classes and we had so much fun making chemical clocks and elephant toothpaste last weekend. Can't wait for the next one. I love seeing the excitement in my kid's eyes when they get their kits in the mail.

Get well soon You’re very loved Thank you for all of the awesome videos

I am an old person ... the fact that you are in love is so great that makes all your information greater ... go girl!

Perfect. This mean we can radio out insults to planets between the hubble and the event horizon, and if there is intelligent life, they will never be able to retaliate nor send insults back that we can recieve. Earth: 1 - Aliens: 0 Unless they already did the same to us.

You state that the Hubble sphere increases in size and that means we see more. However, I understand that while the Hubble sphere increases, more and more of the galaxies are actually outside of it and that means we see less. (We might have more space to observe, but it has less in it). In the distance past I believe that the Hubble sphere, the comic event horizon and the limit of the observable universe were all the same. All that stuff between the observable universe and the cosmic event horizon were once emitting light we could observe, but now they don't because they are moving too fast. Therefore there is less we can see.

I’m watching this again after a year and my head still hurts trying to grasp Get better!! I miss your videos

Thanks for your video!! Great explanation!! Great work!!!

This was an extremely beginner-friendly take on a very unintuitive topic. This kind of stuff has always fascinated me, but trying to explain it to all my friends is hard. Thank you for creating a better presentation of it than I have managed to do! :)

Wait, how can light be travelling away from us to start, then travel toward us as the universe expands? If the universe is expanding, shouldn't the space that the light occupies be moving away from us? So shouldn't the light be moving away from us even quicker than before?

The point of observation is a bit important. At the equator we’re going almost 1,000mph. 93m miles per second (roughly) is our perceived speed of light as I understand it. If we moved faster than the speed of light, what would one see? Well we’d see a bright white spot because our eyes and brain couldn’t process anything at that speed. It would look like a flashlight shining in our eyes.

As I continue learning about our universe, I keep feeling that there is so much we have no clue about...and I get the sensation that we never will...I now think that the section we can observe is just a small portion, miniscule really, and that other areas of our universe are not expanding, but instead are contracting...very like high and low pressure systems on our tiny planet (which is huuuuge to us, I mean, try walking around it some time!) and the "expansive" section we observe is merely expanding due to the "contracting" pressure of the surroundings, and this will cycle on ad infinitum throughout our infinite cosmos...the "big bang" was merely a small burp, and happens all the time in the infinitude, as too much matter gets too concentrated and has to release its pressure...sadly, I don't think we as a species will ever get evolved enough to grasp any of this.