Gravitational Lensing

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Month ago

In 2015 astronomers successfully predicted the appearance of a supernova within a couple weeks. How did they do it? Win your Ultimate Tech Bundle by entering Fasthosts’ Techie Test here: (Competition now closed) This video was sponsored by Fasthosts.
Special thanks to Geraint Lewis for consulting on gravitational lensing. Check out his USshow channel: and books:
The supernova image in the thumbnail is from my documentary, Uranium: Twisting The Dragon's Tail. Check it out here:
P. L. Kelly et al.
Predicted properties of multiple images of the strongly lensed supernova SN Refsdal
Masamune Oguri. Monthly Notices of the Royal Astronomical Society: Letters, Volume 449, Issue 1, 01 May 2015, Pages L86-L89,
Multiple Images of a Highly Magnified Supernova Formed by an Early-Type Cluster Galaxy Lens
Patrick L. Kelly et al.
"Refsdal" meets Popper: comparing predictions of the re-appearance of the multiply imaged supernova behind MACSJ1149.5+2223. T. Treu et al.
Irwin I. Shapiro (1964). "Fourth Test of General Relativity". Physical Review Letters. 13 (26): 789-791. doi:10.1103/PhysRevLett.13.789
Irwin I. Shapiro; Gordon H. Pettengill; Michael E. Ash; Melvin L. Stone; et al. (1968). "Fourth Test of General Relativity: Preliminary Results". Physical Review Letters. 20 (22): 1265-1269. doi:10.1103/PhysRevLett.20.1265
Research & Writing by Stephanie Hamilton, Ralph Crewe, Petr Lebedev, Derek Muller, and Jonny Hyman
Animations & VFX by Jonny Hyman & Ivàn Tello
Thanks to Jaime Portsmouth for his gravitational lensing simulator and help enabling it to render simulations.
Supernova simulations courtesy of Adam Burrows
Numerous hubble images by Hubble Legacy Archive, NASA/ESA/STScI
Numerous images by ESO / NASA

DANG JOS 9 hours ago
Incredible video and fascinating! It's always surprising how good scientists are at figuring things out!
Czesław Władysław Wielgus Marynowski
Czesław Władysław Wielgus Marynowski 15 hours ago
Erwin Shapiro_:_Ben Shapiro?
Jock Graves
Jock Graves 19 hours ago
Greetings from Entropy
Taxpayer juliet
Taxpayer juliet Day ago
Which artist do you want to drop an album right now?
ஆகாஷ் - AKASH. SIVAH.
ஆகாஷ் - AKASH. SIVAH. Day ago
9:36, I understand he didn't cover thus due to maybe its complexity, but how do we know some of the stars absolute luminosity?
Kevin Merioles
Kevin Merioles Day ago
6:24 😏
mdu2112 Day ago
The reverb of the small recording room is made more obvious by the background outdoor scene.
Adam Wyatt
Adam Wyatt Day ago
Nice video. Unfortunately a slight error: you mentioned the a contribution to the time-delay comes from the fact that the wide-angled rays travelled further than the shallow-angled rays, but this is false. The reason why the rays "bend" is because the speed of propagation changes and thus causing the wavefront to curve, and as a result the optical path length (and hence delay) is the same regardless which path is taken. This of course neglects dispersion and time-dilation and assumes perfect imaging. As the time-dilation in our own solar system showed, I presume that is the dominant effect for the time-delay.
Bijan Izadi
Bijan Izadi Day ago
Megaparsec is so cool to say
Adwaith Reddy
Adwaith Reddy 2 days ago
Do one thing tell the person on Mars to send his time and blast Mars at the same time (Assuming it takes 20 mins for light to travel from earth to mars and instantaneous for light to travel from mars to earth ) Earth send message at 12 :10 Mars recieves at 12 :30 but the person thinks it is at 12 :20 and send a message that the time is 12:20 and instantaneously blast Mars Now if earth saw mars in real time earth will see Mars blast at 12 :30 and earth will also receive a message that it is 12: 20 and hence proved that the previous assumption was correct that it takes 20mins for the light to go to mars and instantaneously comes back to earth
邹捷 2 days ago
Gravitational lensing blows my mind. "Oh, those four galaxies you can see over there? Yeah, they're the same one..." Madness.
ImpactoDelSur Enterprise
ImpactoDelSur Enterprise 2 days ago
Is it possible that some of those celestial objects that we observed so far have gone through so many "layers" of gravitational lensing that what we are looking at might be in the direction of other side of the earth?
random email
random email 2 days ago
Mick 2 days ago
Dear chat and @Veritasium can black give rise to star or explode to create new stars. Is this possible. Plz help
Adobe Reviews
Adobe Reviews 2 days ago
Spacetime be like: But, will it bend?
Amedeo Filippi
Amedeo Filippi 2 days ago
I wonder how we can be sure all our cosmological conclusions and theories can be true if everything we can observe is based on the electromagnetic spectrum we get through our different kinds of detecting instruments and at same time we know that all these objects in the sky are no longer where we locate them and also that their emitted EM waves are all distorted and scattered during their so long journeys to reach us “ now “
ryuhjn yguh
ryuhjn yguh 3 days ago
I cant even visualise that when a supernova explodes, in less than a second tens of thousands of miles of matter and gas covers the surrounding space.
Pax Webb
Pax Webb 3 days ago
Mind blown… again
Shay Detert
Shay Detert 4 days ago
Theoretically let's say you could teleport anywhere instantaneously and no matter where you were you could survive for a set amount of time if you traveled somewhere off in the distance of space and looked at earth would that be considered time travel because you are looking at light that has been reflected off the earth in the past now traveling to the planet you are on
Aaron Gayod
Aaron Gayod 4 days ago
6:29 *:)*
Akash Gupta
Akash Gupta 4 days ago
Can you make a video on Super Symmetry please???
MrLaTEchno Reality,Stop Fake News.
MrLaTEchno Reality,Stop Fake News. 6 days ago part time-machine-like observation ..?... to see time like this makes you wonder. If time is this "easy "to watch how can we " put some tools to it" so we can use it in different way's. B.D.W is it : Hawkeye
Weiss Merlin
Weiss Merlin 6 days ago
I have long waited for a mind blow like this. thank you for granting me such a treasure
Astropj 6 days ago
"Hey there's a new supernova on that galaxy! Never mind, it's just the same galaxy's lensed pic delayed due to gravity".
Julian Harley
Julian Harley 7 days ago
The universal equivalent of a photo bomb
9B 34 Dominic
9B 34 Dominic 7 days ago
so well explained.
RIZE RenNerdClub
RIZE RenNerdClub 8 days ago
JustMoseyinAround 8 days ago
*BeetleJuice, BeetleJuice, BeetleJu-*
Taxpayer juliet
Taxpayer juliet Day ago
derek: einstien's concept my brain: salt and pepper
pokfen 8 days ago
About a year to late. On astronomy I had to write a paper about Gravitational lensing. Good thing your video about Black Hole and how it looks like helped. I even linked than video in that.
ronkirk50 8 days ago
I'm absolutely goob smacked!
Sutairn 8 days ago
WIth this information we should be able to create a concrete equation on how much our movement is effecting redshift, why do we not see this equation when calculating the Hobble Constant?
Jacob Sawyer
Jacob Sawyer 9 days ago
any day now ... *in the next 100,000 years*
Bo Reed
Bo Reed 9 days ago
I'm on this guys wavelength so frickn happy you made this rite on man
SKM GAMER 10 days ago
Do galaxies revolves around some things?🤔
h.s.mani deep
h.s.mani deep 10 days ago
Looks like the supernova came to bargain.
Big Dogo
Big Dogo 10 days ago
1:40 "In the next hundred THOUSAND years." :(
Big Dogo
Big Dogo 10 days ago
Gravitational lensing blows my mind. "Oh, those four galaxies you can see over there? Yeah, they're the same one..." Madness.
Sourav Dey
Sourav Dey 11 days ago
What I thought of this ?? Wowweee... please teach me how did they measure the trajectories and times so accurately.... what math is behind this?? If they published a paper??
Alberto Malvido
Alberto Malvido 11 days ago
One of my favorites video! Thank you so much
Gplayer 11 days ago
"In 2015 astronomers successfully predicted the appearance of a supernova within a couple weeks." Technically, that was not successfully predicted a supernova(the event happened at the end life circle of the star far far away), just predicted what image(what we would see from the Earth) the Hubble telescope would get according to the video, which were two different things. Am i right?😉😉😉😉
Wandering Dust
Wandering Dust 8 days ago
That's the actual image. Yes, it already happened and we are only seeing it now. Not exactly a prediction but it takes time for information to pass.
Makaveli Thedon
Makaveli Thedon 12 days ago
He said stars in nearby universe by mistake. Lol 9:31
Diego Ferreyra
Diego Ferreyra 12 days ago
Where’s the universe expanding FROM?
a b
a b 12 days ago
We are so lucky to have Einsten
Unknown Prodigy
Unknown Prodigy 12 days ago
This is incredible. I don't know what else to say.
Reuben Stern
Reuben Stern 12 days ago
Makes you realize space is mind blowingly massive.
Reuben Stern
Reuben Stern 12 days ago
A long time ago In a galaxy far far away?... Proof of Darth sidius and his death star.
arnav sood
arnav sood 12 days ago
Einstein cross Jesus Christ!
Yuda Dwi
Yuda Dwi 12 days ago
Soo... Does it mean that if we have a telescope sharp enough to see individual planet on galaxies far far away, and strong enough to catch light reflected from earth, we can technically see our past?
James Blackstar
James Blackstar 13 days ago
Good hosting, not everyday i see.
JebClang 13 days ago
A lens made of "graveity". Yeah right, what sorcery is this? Gravity doesn't even existt
Denzyl Casuela
Denzyl Casuela 13 days ago
We can predict a supernova but not corona?
Maciej Cholewa
Maciej Cholewa 13 days ago
Maybe because universe changes but very slowly compared to it's size, when viruses mutate fast, thus we can't predict all mutations.
Harish Dubey
Harish Dubey 13 days ago
I wish i was not in a city so i could see this rare phenomenon
klaas victor
klaas victor 13 days ago
This is the most surprising video I have seen in my life! It got me Goosebumps! Humans are incredible to have discovered this!
Bhaskar Bhardwaj
Bhaskar Bhardwaj 14 days ago
The previous video title was more juicy, at least I feel
Willian 14 days ago
Panarbore 14 days ago
absolutely adoreable to be able to work on such topics!
Rama Bandyopadhyay
Rama Bandyopadhyay 15 days ago
So...The flat earthers are not wrong! They are right in another perspective
Mohd Sameer
Mohd Sameer 15 days ago
Your videos are lit 👍🏻
Andrey Sergeev
Andrey Sergeev 15 days ago
Thank you! Ah...I thought it will be about building a lens for a gravity laser. But this is very interesting too.
Phantomrocks #phani
Phantomrocks #phani 15 days ago
Meanwhile supernovas image giving us a creepy smile at 6:25
yogesh jangid
yogesh jangid 15 days ago
Can anyone tell me how light is traveling in a curved path..I have learned that light travels in straight line.
Andrey Sergeev
Andrey Sergeev 15 days ago
I don't know what does really moving straight means but let's say it is moving while being not affected (accelerated) by any force. That means nothing is changing the momentum of a photon I guess. I would naively say that light indeed travels in a straight line through space but if you bend space itself then that line is no longer straight. Photons have no mass - gravity does not pull them as regular objects with mass. The gravity is bending space and time therefore anything in that space is bent too. You can draw a straight line on a paper sheet then crumple that paper - so the line will be straight relative to the paper but not to the world around it. That way path of light is curved. That means that the direction of a photon is changed - so its momentum. So I will guess you need to spend some gravitational energy on that. But what is the least possible degree of that curvature? That I don't know. If you look at curved lines on a display they are made from pixels - so any circle is in fact a sum of small straight segments. If that is the case for space curving then there are always some parts of space where light indeed travels in a straight line - because it can't be affected by any force. If not then you can arrange a bending of any degree at any place so it's not necessary to have any straight segments at all.
John Berry
John Berry 15 days ago
Wait til' the UK viewers find out that the 5000 pound Techie Bundle actually weighs 5000 pounds (
Mahmoud Mostafa
Mahmoud Mostafa 15 days ago
it was Isaac Newton.
DevN 16 days ago
when my boss catches me in a foto somewhere else..can i explain that its perhaps gravitational lensing...both time and place r incorrect..i was actually working at home ;)
DevN 16 days ago
and millions of people r convinced they know it all from 1 holy book.
Trying1 /
Trying1 / 16 days ago
It sucks
Ryan Johnstone
Ryan Johnstone 16 days ago
amazing !!!!
Chris Methot
Chris Methot 16 days ago
This just reinforces a question I have had for over 10 years. Using the discipline of the null hypothesis prove to me that every galaxy you see in the cosmos isn't the same galaxy seen from a different angle at a different time? The cosmos as a hall of mirrors.
Chris Methot
Chris Methot 14 days ago
The first answer might be how could we see galaxies merging if there were only one.
Kinnari Bhalerao
Kinnari Bhalerao 16 days ago
Gravitational lensing is one of my favourite concepts!! And this is amazing!!! Loved the way the video is made. Seemed like we are in space!!!🌌
Muhammad Hamza Tahir
Muhammad Hamza Tahir 16 days ago
Space has always been an inspiration for me. Hubble is fascinating my heart day by day.
Gabriel Ferrão
Gabriel Ferrão 16 days ago
Star: Betelgeuse Me: Be tel gese Veritasium: Bettle Juice
FezRez 17 days ago
Its incredible how much info scientists can extract from these tiny little smears of light
Wu Chenglin
Wu Chenglin 17 days ago
1:32 beetlejuice
Prince Fel Ezekiel R. Licardo
Prince Fel Ezekiel R. Licardo 17 days ago
It's fascinating that how much information astronomers can get from pictures, from a normal person, not so much.
Dennis D
Dennis D 17 days ago
And here I struggle getting a decent pic of my dog.
Nae Dolor
Nae Dolor 17 days ago
Is this one of the first generation stars in the universe ?
David M. Johnston
David M. Johnston 17 days ago
Great video Derek, thank you for teaching me so many interesting things! By the way, I'm just thinking... I've been following you since 2013. Most of my closest friends I've known for less time than that. And your videos continue to amaze me! Take care Derek, and keep up the excellent work! (no pressure :-)
Learning Unity
Learning Unity 17 days ago
did you break the space time continuum? no worries, just seal it with FLEX TAPE! *slaps tape on spacetime*
穆罕默德·扎恩 17 days ago
Only Legends Know the Title of This Video Has Been Changed
Mr. Thomas A. Anderson
Mr. Thomas A. Anderson 17 days ago
I love your videos! You make them entertaining and you have a catchy voice.
Soumen Bhattacharya
Soumen Bhattacharya 17 days ago
Varitasium and 3brown1 blue are best ones also PBS videos too
Fredrik Attila Farkas
Fredrik Attila Farkas 18 days ago
Does this mean that light can «move» an object aswell? Like airflow over a wing creating lift?
Lünkel 6 days ago
You can push stuff with light. There's the idea of "light sails", large reflective structures that can be put on a probe or satellite of some kind and allow it to use the solar wind. And last year or the year before that the nobel prize in physics got awarded to a team who created a kind of "tweezers" with light.
Mohammed Shaik
Mohammed Shaik 18 days ago
3:48 Damn that looks creepy lmao
Balubish Tech
Balubish Tech 18 days ago
This is mindblowing sorta. Also makes me feel incredicle dumb compared to actual smart people. I knew math was important and read electronics in high school so did alot of math. But counting math that bends light by gravity and mass vs distance and time to the object and beeing able to count that far back including by my guess a ton of gravity bends/warps between stars, galaxies of the fabric of space, with an end result of different years and times to the day, which you can view the same exact thing happening. 🤯 Now thats some hardcore math right there.🧠 Also how isnt Einstein an Emoji by now. 😎✌
seachangeau 18 days ago
Oh its such crap.
Jimmy Johns
Jimmy Johns 18 days ago
Wow, this really opens your mind! It’s like taking drugs OMG. Loved it!
Mohd Shariq
Mohd Shariq 18 days ago
6:29 Seems deep space is smiling on us!..with a cigarette in its mouth! 😵
Lar Wor Tsomv
Lar Wor Tsomv 18 days ago
What if, as the universe expands, the general speed of light increases? Meaning, if we had a window into the future we would observe everything moving faster. This does not affect the Doppler shift, which only cares about the 'stretching out' of light as it moves, since all 'parts' of light will be speeding up at the same time so there will be no differential that would be evidenced in the color shift. However it may 'speed up' other observable cosmic activity, meaning light reaches us faster than expected if it were moving at a 'constant' speed. Therefore the calculated expansion rate of some methods gives a lower result.
raedtrab 19 days ago
Am I still on time to answer the question? Which is actually wrong it was Sir Isaac Newton who answered to RICHARD BENTLEY (theologian and philologist) “That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it. Gravity must be caused by an agent acting constantly according to certain laws; but whether this agent be material or immaterial, I have left open to the consideration of my readers” this was in answer to And what Richard Bentley wrote that generated Sir Isaac Newton’s answer was And as for gravitation, tis impossible that that should either be coeternal and essential to matter, or ever acquired by it. Not essential and coeternal to matter; for then even our system would have been eternal (if gravity could form it) against our atheist's supposition and what we have proved in our last. For let them assign any given time, that matter convened from a chaos into our system, they must affirm that before the given time matter gravitated eternally without convening, which is absurd. {Sir, I make account, that your courteous suggestion by your last, that a chaos is inconsistent with the hypothesis of innate gravity, is included in this paragraph of mine.} and again, tis unconceivable, that inanimate brute matter should (without a divine impression) operate upon and affect other matter without mutual contact: as it must, if gravitation be essential and inherent in it.
Kumar Digvijay Mishra
Kumar Digvijay Mishra 19 days ago
Gravitational lens smears images from Hubble telescope. What is the cure for distortion? Apart from making intelligent assumptions/guesses, there seems to be no other method to give a clearer image.
sokin jon
sokin jon 19 days ago
The Real Question: How do scientists notice a tiny dot of a star in the middle of so many blurs and other stars?!
ryuhjn yguh
ryuhjn yguh 3 days ago
“You will be able to see beetle juice’s supernova” Me: “Hmm”
Michael Polakowski
Michael Polakowski 6 days ago
Generally, you can find the difference between two consecutive images by subtracting one from the other. Everything that's the same cancels, and only the changes remain. Also, in the case of the supernova in the video, they were expecting it to appear in a specific location.
A G 10 days ago
They don't. No, but with the power of modern technology, devoted people, and some of the smartest people on the globe many things are possible.
Aadil Peer
Aadil Peer 10 days ago
Unstoppable curiosity does it all...I am more surprised to know that there is actually stuff like time dilation.5 years out from physics and I thought it is all theoretical.Guess that's why flat earthers still exit.Might be of my kind:)
Sourav Dey
Sourav Dey 11 days ago
It’s their passion... they love to do that.. isn’t that amazing??
ilkercan Kaya
ilkercan Kaya 19 days ago
I want to live hundreds of years to observe and study all the knowledge in universe. Sadly humans life span isn't long enough for such thing. I want to discover new planets, understand what is behind this universe. I don't wanna die without knowing why I was here.
Amadley Gaming
Amadley Gaming 19 days ago
Veritasium pumping out superlative quality content is one of the rare positive things about 2020 - How do they do it? That's the real mystery
Ruben Anthony Martinez
Ruben Anthony Martinez 19 days ago
Gravitational lensing maybe a misinterpretation, this lensing could also be produced by cosmic space, becaused *space is not completely empty-it is a hard vacuum containing a low density of particles, predominantly a plasma of hydrogen and helium.* It is the space medium itself that causes this light refraction phenomena. Then it becomes understandable that galaxies tend to form a higher density of this space medium ( Halo) , which produces the lensing effect, and has nothing to do with gravitational fields.
sokin jon
sokin jon 19 days ago
So here is a neat trick folks! This will help you understand the universe and that Big Bang everyone keeps babbling on about. Take a stone, throw it in the pool, watch the rippl
Gagandeep Singh
Gagandeep Singh 19 days ago
30 October 2020 - I started to study stars and supernova. 14 November 2020 (today) I am watching this video. 11 December 2020 is my birthday. Now skip to 2:30
CyberBeast66 19 days ago
I don't know why I just thought of this question weeks after the video, but if gravitational lensing can allow us to see the same light source appear at multiple points and over different time periods, how can we know a lot of what we see in the sky isn't lensed from somewhere or someWHEN else? We would be counting some of the pinpoints of light in the sky multiple times, skewing our data right?
Ry V.
Ry V. 19 days ago
Space time would seem to not be homogenous in the universe thus various gravitational lensing effects.
Ayoub Berrada
Ayoub Berrada 20 days ago
6:30 creepy smiley face
Charles Rogers
Charles Rogers 20 days ago
My brain hurts now
MH Promit
MH Promit 20 days ago
He is cool🤯
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