How Many Galaxies Are Moving Away From Us Faster Than Light?

[@eamonnsiocain6454]

Yes, do some more videos in this format in addition to your other videos.

[@mauritz3912]

As a Norwegian who uses "the long scale", it can be confusing when you use the term billion... Just be careful not to mislead anyone :)

[@domainofscience]

Good point! What does a billion mean on the long scale? Is it a million million?

[@mauritz3912]

​@@domainofscienceA billion is a million million 10^12. We call a billion a milliARD. You can imagine the confusion when journalist translate English news into Norwegian.

[@domainofscience]

@@mauritz3912 Ha yes I can imagine. Okay cool I can keep to the scientific notation then it is simpler.

[@tednorton5150]

One more nightmare for the ignorant masses I think I just made an in joke 😂

[@reservetruls]

Numberphile made a video about the two systems, kzbin.info/www/bejne/eV6YY3R_lNSdr7M

[@cosmicwakes6443]

I had the correct answer and my method was the same as yours except the last step where I used the ratio of the light emitted from the farthest observed galaxy and the 13.9 billion and then multiplying the answer by a hundred to get the percentage. Great video and please do more of these challenges and make it more challenging.

[@Laly7]

I really liked this format. 👍

[@cs836]

Awesome video, more videos like this would be great

[@violetdelilah3705]

I just subscribed! I love your videos I can’t believe how fascinating everything is. 😁

[@myguy5416]

Love the puzzles and especially: the really clear, step by step, well worked out solutions. Fantastic. Loved it.

[@Rady610]

Neat! Thank you! I think this type of video is interesting and engaging. If you know Veritassium, you would agree that having your audience think and solve problems is a good way to go. Cheers!

[@AdrianSheard]

The rate of expansion increases making r smaler (so the volume we can interact with decreases) The increase in R is really interesting since it's a rework of the 'ant on a rubber rope' paradox!

[@jellybabiesarecool4657]

Please make more videos like this. I love applying maths to solve problems in physics.

[@GilbertoPOA]

I could finally understand how people know the visible universe is just a fraction of the total Universe.

[@herp_derpingson]

We are assuming uniform density of galaxies. Is that a valid assumption to make? Also, as we go further out, the density should decrease (by r^3 ?). So, we have 97% of the space by volume expanding FTL. Not galaxies.

[@hansisbrucker813]

I was thinking the same 🤔

[@straight-outta-jutta]

Galaxies and galaxy clusters are actually really uniform from a large scale, and the density doesn't decrease further from us. It's just "our" observable universe, elsewhere it's different. Doesn't matter where you are, the universe is everywhere, therefore the density of galaxies does not drop according to distance from us

[@herp_derpingson]

Then the universe not really an eucleadean sphere anymore. What does the radius of this geometry mean?

[@straight-outta-jutta]

@@herp_derpingson the radius just defines the border of what is observable to us. The actual universe is much much bigger than our observable universe, the light just didn't have enough time since the big bang to reach us yet.

[@herp_derpingson]

@@straight-outta-jutta What is the shape of the real universe? Sphere? If not, how are we getting the ratio?

[@_M27_]

Is there a reason why you're not being precise here? Like c = 300,000,000 m/s instead of 299,792,458 m/s and rounding of in between calculations? Just curious...

[@domainofscience]

Yes because there is inherent uncertainty in some of these key numbers like the rate of cosmic expansion. Results from observations put it in the range of 67 to 74 (km/s)/Mpc so we can only ever hope for approximate answers here. Good point though, I could have explained that here. Thanks!

[@Real_Reels_Now]

I’m not even gonna lie, I attempted to create a equation just like this a month ago when thinking of if there is a possibility of a center of the universe and had to take account multiple things such as collisions and new stars and such

[@TheTastyPancake]

Really clear explanation!

[@haggismcbaggis9485]

I was somewhat skeptical of this as it seems counterintuitive that a 14 radius within a 46 radius (which is 30%) would only equal less than 3% volume. Yet, I calculated it with different steps and was pleasantly surprised to come to the same answer. I think the diagram is not to scale and that might of threw me a bit.

[@smokey04200420]

I see where the confusion is. When you look at the edge, the observable universe edge doesn’t look like it is 46B Ly away, it looks 13.8B Ly away. I don’t know how they got 46B Ly, but that’s not correct. It’s actually an infinite amount of space within the 13.8B Ly. But we can’t see exactly 13.8B Ly out, we can see only out to when recombination occurred 13.5B Ly away. So not quite an infinite amount of space lies within the observable 13.8B Ly, but an infinite amount to space does lie within 13.8B Ly, we just can see that far back.

[@LuisBruno]

Loved the video, indeed. I can't help but notice the similarity between that "about 14 Bly" and the age of the universe; a mere coinkydink?

[@icebox5177]

Luis Bruno what he meant to say wasn’t the actual size of the universe, which for all we know is infinite. What the problem asks about is the observable universe. This means all the light that came from the Big Bang. Since the Big Bang happened 14 billion years ago, it would have taken the light 14 billion years to reach us, and therefore the observable universe is 14 billion light years in radius.

[@smokey04200420]

It’s no coincidence. The one thing Einstein said about relativity (how to add relativistic speeds) he failed to do. Had he added the velocities correctly, he would find that NOTHING not even space itself TRAVELS FASTER THAN LIGHT! There is no such thing as sphere of influence.

[@timetravel_0101]

I feel so little right now!

[@spicyy812]

i think you could've just used 21.7km/s per million l.y. to begin with so you didn't have to convert back and forth from parsec :)

[@KaiHenningsen]

Or you could, you know, just convert all the various different things into metric at the start. Though that makes me wonder. This assumes that the densities of galaxies in the small and big volumes are the same. How sound is that assumption? Not only is there a vast difference of age (which should, then, mean more galaxy mergers), there's also the somewhat paradoxical point that the edge we *see* looks geometrically vast, but is actually from a time where the universe was much *smaller* than today. I have no idea what cumulative effect to expect from that, but it seems unlikely that there is none. Which would have an effect on the answer.

[@awesomeedits8086]

Yes yes yes do some more videos like this oneeeeeeee

[@awc9811]

First I thought as how much galaxies are in the observable universe, but it is not like that

[@dpie4859]

Question: can you do a video where you show by which mechanisms energy is transferred from the singularity in a black hole to the event horizon where Hawking radiation is emitting energy out from the black hole. What I find puzzling is how a quant mechanical process far away from the singularity can extract energy from the singularity. Within a black hole all particles and time moves towards the singularity and nothing can move outwards/upwards. In super massive black holes the distance between the event horizon and the singularity can be as large as our solar system.

[@raderator]

And it's shrinking. Eventually we'll be back to the one galaxy of pre Hubble.

[@kinghacker9577]

Can you tell us where do this equation come from?

[@ericdelacruz7621]

I’ve been stuck on the same question for a week now. I felt you may know the answer since your intelligent enough to measure galaxies. I don’t want to skip the question because it’s bothering me. If you can help thanks. Appreciate it.

[@dpie4859]

Must quite literally been the largest volumes ever calculated.

[@timduncankobebryant]

Fermi problem type. I love this stuff!

[@erebosd2592]

What's the name of the background music?

[@domainofscience]

It's my own music I made. I do all my own music :)

[@shaitoledano5867]

@@domainofscience It's really good!

[@robertomontanino7620]

Could you do a map of philosophy?

[@mohammedettayby]

Nice bro 👍 where us the map of geology

[@koungmeng]

I think your solution to this question based on an assumption that all galaxies in the observable universe are evenly spread out. In my opinion, the question should be "Calculate the proportion of SPACE in the observable universe that are moving away from us faster than speed of light". Correct me if I'm wrong. Apologize for bad English. Stay safe and have a nice day♡.

[@Healitnow]

It sounds like this is the practical replacement for dark energy and matter. 97% is a lot of mass. If this is in itself not enough would the extra attraction of electromagnetism make up the difference to keep the universe in place?

[@joblessreaper964]

My guess is the 2.8% if we use numbers that are not rounded will be very close to equal 'e'

[@sander_bouwhuis]

Not sure if you are just making a joke, but this 2.8% is a constantly changing number. So, in the past it was exactly π and exactly 12.3456789% and exactly everything between 2.8% and 100%.

[@physicstheoryofmetinaridasir]

I have predıcted with my theory and my formula 6.3 tımes greater than the speed of light, which is measured as if apparently inside of M87 black hole. I SUGGEST HAVING A LOOK AT THE FIRST PART OF MY THEORY AND MY FIRST FORMULA WHICH DETERMINES A LINEAR VELOCITY OF...6.3 TIMES GREATER THAN THE SPEED OF LIGHT, ETC. AND I TOLD WHERE OUR MEASURED CONSTANTS ARE ROOTED IN. We need to change the concept of matter that makes us imprisoned by all kinds of impressions and especially by accepting the vacuum illusion which it has been sitting comfortably in it

[@blaze-pn6fk]

That's crazy and sad at the same time

[@will2see]

Instead of those primitive calculations, you should explain what is the difference between the Hubble horizon, cosmic horizon, and particle horizon. You should explain why the "observable" Universe is 46*10^9 ly in radius when its age is "only" 13.8 billion years. You should explain what is the difference between light travel distance, proper distance and comoving distance. You should explain why isn't the space-time expanding but just space. See, that's what I really would like to know...

[@ericdelacruz7621]

Can you prove the formula 1/3 equation is true in volume of a triangle pyramid.

[@amitsamel9943]

Just curious, isn't 97% the volume of universe not visible to us. How does that equate to 97% of galaxies not visible to us. Are galaxies equally distributed in the volume of the universe?

[@sander_bouwhuis]

The universe on very large scales is homogeneous. This means that it doesn't matter in which direction you look if you look at things on a large scale. Think of it as standing somewhere in a forest. Wherever you look around you, you'll see about the same amount of trees in your view.

[@henrikdahlgaard1824]

Only true if the desity if galaxies is the same all over.

[@ShadowFormFG]

It seems that the spatial distribution of matter in the observable universe is homogeneous and isotropic.

[@shaitoledano5867]

So I'm confused. If they are riding expansion faster than light, than aren't they by definition outside of the observable universe? The light from such an object would never reach our eyes, and thus cannot be observed?

[@oegunal]

He covered this last video. Basically, the light we are seeing now are the photons emitted in a much younger universe when the source galaxy was both much closer and not yet moving faster than light w.r.t. us.

[@shaitoledano5867]

@@oegunal No, I understand that. What I. saying is that those objects (stars, galaxies, etc) are no longer actually within the circumference the observable universe, just the photons that they emmited before they were moving away from us f.t.l.

[@oegunal]

@@shaitoledano5867 oh, I see what you mean. I guess what we consider to be "observable" are the photons and the past state of the universe those photons now represent (further past, the farthest we can see). I suppose it's just a matter of definition.

[@theliamofella]

Why is it that the farther away from earth galaxies are the faster they are moving? It’s driving me crazy trying to understand this

[@silasr20]

I believe it’s because of space itself is expanding at an incredible rate.

[@TheKivifreak]

Don't some galaxies outside this radius move towards us while the expansion is happening. Similarly to the ant-on-a-rubber paradox, these should be reachable.

[@doriannamjesnik3007]

What radius, inner or outer?

[@edwinmuchiri480]

Absolutetly

[@naqithegoat5504]

isnt this just showing in what % of space galaxies are moving faster than light for us, not wat % of galaxies

[@wizardz7938]

I hate i wasnt gifted the power of math😭

[@noreaction1]

I don’t understand, isn’t something traveling away from us faster than the speed of light not able to emit photons in our direction fast enough to reach us? If so then how can we observe something which doesn’t reach us? This doesn’t make sense, unless you are talking about things which at one point were moving slower than the speed of light away from us, and who’s photons we can observe from that point in time?

[@Vivi2372]

Keep in mind that the expansion of the universe is accelerating. When the light we see now was emitted from those galaxies they weren't moving away from us faster than light, but they are moving away faster than light right now. So the light emitted by those galaxies today will never reach us. One day much of what's observable at the moment will, from our perspective, slowly fade away never to be seen again.

[@taketime0626]

I had the same question....thanks for asking it 👍

[@dlbattle100]

r=14 billion light years Is it just a coincidence that this is close to the age of the universe?

[@sander_bouwhuis]

This is just a coincidence. The numbers rely on the speed of light and the expansion rate of the universe. Neither are directly dependent on the age of the universe. Unless the expansion rate grows linearly with the age of the universe, it is coincidental.

[@thuynguyenthidieu2074]

Damn, I just don't remember whether it should be 4/3 or 3/4 =))

[@Tharkon]

Lucky for you, it doesn't matter in this case because it always cancels out.

[@smokey04200420]

Facepalm if after solving this, you still don’t know why you are wrong, then I don’t know how you’ll ever realize that your theory has a major flaw in it. Hint: 14B ly is no coincidence. It has to do with the age of the universe.

[@Dineshkumar-gd1fp]

Super

[@maurokoller3910]

this is sad :(

[@galaxyvita2045]

I understand your calculations but aren't you calculating what percentage of the universe we can see, that is not necessarily the same as the percentage of galaxies we are able to see. If we assume that galaxies are and always will be uniformly disturbed that this is a valid reasoning. But i'm not sure why this would be a valid assumption.

[@SolyomSzava]

Take a look at the cosmic microwave background radiation, and you'll see that the universe is rather uniform in its distribution (which in itself is an interesting puzzle in astrophysics, as to why it is as it is).

[@galaxyvita2045]

@@SolyomSzava thx for the clarification

[@Dineshkumar-gd1fp]

இன்னும் நிறைய தோழரே!