Measuring the Speed of Light | Wonders of the Universe w/ Brian Cox | BBC Studios

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In the last episode of Professor Brian Cox's epic journey across the universe, he travels from the fossils of the Burgess Shale to the sands of the oldest desert in the world to show how light holds the key to our understanding of the whole universe, including our own deepest origins. To understand how light holds the key to the story of the universe, you first have to understand its peculiar properties. The man who first grasped these properties was Danish astronomer Ole Rømer, who in 1676 made the first quantitative measurements of the speed of light.
Having explored the wonders of the solar system, Professor Brian Cox steps boldly on to an even bigger stage - the universe. Who are we? Where do we come from? For thousands of years humanity has turned to religion and myth for answers to these enduring questions. But in this series, Brian presents a different set of answers - answers provided by science.
This is a channel from BBC Studios who help fund new BBC programmes. Service information and feedback: www.bbcstudios.com/contact/co...

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14 окт 2013

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Комментарии : 109

@DrivenMind 9 лет назад

I wish this series and Wonders of the Solar System were on Netflix...

@varshinilolla3090 2 года назад

Collaboration of BBC and Brian Cox is beautiful. Love watching this series.

@phmwu7368 2 года назад

Basic stuff for astronomy classes 🤓

@xxBAMSTERxx 10 лет назад

you know shit is going down when Brian's in a desert

@CavllNorthNorth 6 лет назад

true haha 😂

@carcorr 3 года назад

😂

@gaiusbiju6067 2 года назад

Actually arts and literature are shit😂

@lesterjones7385 9 лет назад

does anyone love the feeling u get when u finnally realize something? you go OOOOHHHH NOW I GET IT

@NarendraTirunagari 10 лет назад

Finding the speed of light helped us in understanding the vastness of Universe. Thanks to the great people who worked to find the speed of Light.

@petelowson5481 3 года назад

The production of all of these Brian Cox BBC series is amazing. Makes it even more interesting.

@crunk1 5 лет назад

I like to imagine Brian Cox isolatedly roams around deserts and derelict Brazilian prisons, offering impromptu astrophysics lessons and analogies.

@27plays 7 лет назад

For those who are thinking this is wrong how could IO moon time period changes.... Ans. It won't change, listen to him carefully 👂, correct explanation is if in summer, we could see IO emerges at 5pm then later in winters we see at 5:10pm (values taken just for explaining ).. The known time period around the Jupiter is same but it took time for light to reach us.. Which results to the fact that light travel with some finite speed

@ludiusmaximus 5 лет назад

But regardless how long it takes light to travel, it does not change the time interval between two events. If I light a flashlight for exactly one second, you will see exactly one second of light regardless whether you are standing right in front of it or wether you are lightyears away. The only difference is that when you are lightyears away you will see this second of light only after some years. But there is no way for that second of light becoming longer or shorter, UNLESS flashlight and observer are moving toward each other (then the second becomes shorter) or they are moving away from each other (then it becomes longer). It is like the Doppler effect, just with light instead of sound. The explanation here by Brian Cox does not take this into account at all and is therefore very crude!

@ludiusmaximus 5 лет назад

This guy here explains it properly: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-gSb4NhoO0Fk.html

@solveigskadhauge1519 4 месяца назад

COX's explantion of Rømers method has so many errors. Look it up elsewhere

@bettyatack4333 9 лет назад

Wonderful

@stud000000079 10 лет назад

Nice work Cox

@muER76 4 года назад

Thank you Steve Tyler!

@TheJUNGLESURFER 4 года назад

yes same test tube both ftm

@Mehernoshuk Год назад

So beautiful nature

@sasha6858 10 лет назад

Cool!

@vdubs4life1964 10 лет назад

thanks :D

@hklausen 7 лет назад

Well, It's not as simple as Brian Cox imply. A discrepancy in IO's accumulated orbit time slowly (months) build up when the earth move toward Jupiter, compared with when earth move away from Jupiter.

@denbecr49 5 лет назад

Sure, but only the extremes are needed to understand and calculate it.

@moonlandingagain3228 3 года назад

It is!

@BlackPantherrStudios 10 лет назад

good video

@AtheismLeadsToIrrationality 5 лет назад

3:20 is awesome

@lancer525 5 лет назад

This guy is Britain's response to Carl Sagan. And every bit as good.

@Sardiniansoul324 6 лет назад

What a genius

@berndpfe 6 лет назад

Einstein's theory bases on these findings. interesting to know how early this has been found out but never got this grade of scientific importance until Einstein made it an universal constant. Which is valid everywhere in the positive space. Light actually travels slower through e.g. Water or Glass. Even when travelling through the atmosphere (air, gases), lightspeed (as well as for radiowaves) is a very small fraction slower than in open space.

@RickFlip123 10 лет назад

My min has been blown

@HipsterKaren 10 лет назад

That accent is beautiful.

@markorollo. 10 лет назад

All great minds come from Chadderton!!

@thelionsroar5142 4 года назад

If only we knew who we truly are...we are Light ourselves

@elmotociclista9296 6 лет назад

This is why it drives me nuts when someone takes much credit on today's youth, claiming they are so smart because they use phones, tablets and so on with such ease, sometimes even implying that men from previous centuries would not stand a chance along today's youth, regarding intelligence, Ole Römer was a genious, and many people back in the day had some really tricky questions to get solved, and they did it, without information at the palm of their hands.

@gbolt111 3 года назад

People dont realize that phones, tablets and what not are made this way. They are so easy to use that baby can do it (literally). People fool themselves thinking that using such user friendly devices makes them smart. Its actually can be the opposite.

@vdubs4life1964 10 лет назад

how much time difference in seasons are we talking about here?

@balf1111117373 7 лет назад

When they measure of the speed of light do they include the time the light takes to travel through your retina and your brain? To process the light that would add a couple of m/seconds to the distance.

@123kion 6 лет назад

ahaha good point

@denbecr49 5 лет назад

No. Your perception time is not a factor in the calculation. Study Michelson's apparatus. Your perception time does not influence the measurement. Only the rpm of the rotating mirror, the distance to the far mirror and the angular change of the final image are needed to make the calculation. The observer needs only to measure the change in the position of the spot of light on the screen from when the rotating mirror is stationary and when it's rotating at a known rpm. The observer is not functioning as a pulse detector/timer; only as a recorder of how far a spot of light has moved on a screen.

@CC-uq7cv 4 года назад

I am confused about the numbers he mentions. The number that I saw was 299,792.458 meters per second. He said, however, 299,792,458. I also don't understand why he said 10 million million kilometers. On NASA (starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html), it says that "one light year is equal to 9,500,000,000,000 kilometers."

@gruff5 10 лет назад

That's true. And massless particles go at the speed of light. To my mind, it does rather sound like a speed limit.

@AmitSingh-sf5qp 4 года назад

Nice cox.

@jjourz612 Год назад

How do you know that the speed of light is the same in all directions ?

@rafaelmoncadavelasco8616 10 лет назад

¡DE GÜEVOS!

@istvanklein 10 лет назад

The fact that the speed of light is finite means that we see nothing in real time. Everything you see happening has happened in the past, even if it's just a few metres away from you.

@pizdocivka 10 лет назад

The moon Io precedes or recedes about 21 minutes in six months.

@rkreike 3 года назад

Light has a constant speed in vacuum of space, and a different constant speed in water, etc. So a light coming from a car standing still is same speed as light from a car that is moving, because also in the atmosphere lightspeed is a constant . But, if an observer is standing still to a lightsource or in motion to a lightsource, speed of light is not the same, while lightspeed in the atmosphere is a constant?

@moonlandingagain3228 3 года назад

Yes!

@jaudry123 10 лет назад

It looks to me that the given explanation is wrong the different period of revolution of Io around Jupiter is when Earth is approaching Jupiter and when Earth is increasing its distance from Jupiter i.e. in the so called quadratures and a frequency change explained by the Doppler effect or

@Decodeish1 10 лет назад

There's no "speed limit", it is just that it takes an infinite amount of power to go as fast as light speed if you weight anything at all? Right?

@TheAcad3mic 3 года назад

In what way is that not the ultimate speed limit? The speed of light is not achievable by anything with even a single Hydrogen sized amount of mass because unlimited energy isn't a thing. If anything the speed of light is the only true, ultimate speed limit.

@lohancindy5442 5 лет назад

So did he replace the other guy cause he hasn’t been accused yet from the pound me too movement

@RickFlip123 10 лет назад

Mind*

@user-bm5kb4cx3l 5 месяцев назад

Yes, that's right, coal etc. are compressed biomass and the fire is decompressed. The same thing happens in our Earth's core only with the cosmos. So there is no gravity or gravitation. So you have a compremirundg in decompression. Are barometers and my common sense Vitali Maier. 29.09. 1982 Eliste Russia After Brian Cox visits the world's biggest vacuum cam the insperatio to my Understanding.

@InArneSlotWeTrust97 4 месяца назад

You If we could travel the speed of light, how long would it take to reach edge of visible universe Copilot Speed of light Explore The edge of the observable universe is estimated to be about 46.5 billion light-years away. If we could travel at the speed of light, which is approximately 299,792,458 meters per second, it would still take us 46.5 billion years to reach the edge of the observable universe. This is because a light-year is the distance that light travels in one year. Please note that this is a theoretical scenario. According to our current understanding of physics, it’s not possible for anything with mass to travel at the speed of light. Also, the universe is expanding, so the actual distance to the edge of the observable universe is increasing all the time.

@bobbyharper8710 7 лет назад

They still can't explain where the moon stuff goes between full moons.

@chrissosa3723 6 лет назад

Bobby Harper oh Bobby you silly goose, we all know that moon is made of cheese, so in between full moons, we gather the cheese and stock new cheese on it (full moon)

@brandonkrebbs 8 лет назад

I'm skeptical..... What about the angle of the planet and how it could hide the Moon for a longer period of time....

@AlexV1980 7 лет назад

it doesn't hide the moon for a longer period of time mate, the light just takes longer to reach earth since earth is further away, the time of orbit for jupiter's moon is still the same.

@Conorp77 7 лет назад

even with that variable, this was still evidence that light traveled at a finite speed, I don't see how you think one cancels out the other

@denbecr49 5 лет назад

His calculation was twentysomething percent off. Seems to me your factor might count for a relatively small bit of error if the deviation from Io's orbit schedule was measured at a different angle when near than far, but that was likely obvious and adjusted for in his calculations . You don't presume Romer's obvious genius in coming up with the correct explanation for a small cyclic deviation from an average time of orbit for Io would have a factor he missed, but you caught, do you? You can always look deeper into the analysis done then (and since) to find out if you are brighter than Romer. If you come back bragging, I'll look it up myself.

@jackdolah2031 5 лет назад

Space is faster than light

@maxgunn555 10 лет назад

If the speed in which jupiters moon moves around jupiter is definitely known to be constant always like our moon then this proves the speed of light unless there's some kind of strange material we haven't detected that the light is travelling through at that particular time. I hate how they say things as if it's matter of fact absolutely... if they were honest... more people would make theories and the more theories the better the theory will be.

@terrancegayapersad2145 Год назад

And our distance to these planets are proven to begin with? Or sizes measured? No calculated, big difference and lots of assumptions

@redred7683 6 лет назад

Can someone explain what 10 million million is in English term not American.

@CC-uq7cv 4 года назад

Americans don't say 10 million million...

@AsratMengesha 9 лет назад

Speed of light is not equal to 'speed of light (C)' Does mirror (reflector) transmit signal (energy) to detectors when energized by incident beam of light? When we use reflection method to measure light speed does the reflector transmit its own signal to the detector, when energized by incident light or just reflect the light? Do detectors detect signals moving at more than 'light speed (C)? No, because Clearly speed of light is much much higher than 'light speed (c)', and we know that by the fact that we observe the farthest object just in a moment.. Right? Thanks.

@TheJUNGLESURFER 4 года назад

except jupiter is not far

@doc-holliday- 6 лет назад

why not say trillion instead of million million?

@georgericher3996 5 лет назад

Doc Holliday million millions sounds better

@lovelynature3568 5 лет назад

Searvh the RU-vid and search miracles of Quran . Speed if light in Quran.

@corbid5093 4 года назад

this is great and all and i watched it in physics class but why is this hooligan in the desert??? go home dude this can be replicated with marbles on a kitchen counter lol

@AsratMengesha 9 лет назад

Which light speed are you talking about? When you observe the reflected light from mars that means you saw mars. Right? But, do you see the light as a wave? or do you see mars as a wave?are you able to measure that wave with your device (detector)? I mean when we say light speed we may need to answer the related question: which light? which light speed? Right?

@AsratMengesha 4 года назад

Hi Brian. Don't you know that you cannot measure the speed of light, because light speed is infinite? Evidence: you think the sun light reaches you from the sun after making more than 8 minutes travel your belief that you have measured light speed. Though experiment: let us say the sun is 93 million miles away. And let us think you have created a rocket that can move 93 million miles a second. Now launch your ticket to the sun. You must be able to see the rovjet hiring the sun after one second travel time. That means, the rocket is there hitting the sun and the sun is there receiving ticket hit, right now, after one second of the rocket to the sun. So, you are the sun as exactly it is now. Lightvspeed is infinite. Right?Thanks.

@joepierson3859 3 года назад

@qy72hund 9 лет назад

can't u just measure it with that radar gun that cops use to see how fast cars are moving?

@2devilbat 9 лет назад

In theory, yes. But you'd have to do it for a while. The gun uses the same technology as the one he's describing, sending a beam of light, and seeing how long it takes for it to get back, except romer didn't have that tech and he had to do all the calculations and observations by hand LOL

@fretingtopolice 9 лет назад

Hubble measured red shift and basically invented the theory to make the radar gun so the answer to your question is No ,It is all to do with Parallax shift and a radar gun is a very primitive version of a device to measure that effect

@qy72hund 9 лет назад

those radar guns measure car speeds... their not built to accurately measure the speed of much faster things. i intended this to be a joke lol didn't think anyone would take me seriously.

@2devilbat 9 лет назад

you technically could, it would just be impractical

@SilentPixel 7 лет назад

When I saw the radar gun part, I automatically though of the death star. Lol, planning to destroy Jupiter with it.

@lovelynature3568 5 лет назад

Speed of light is mentioned in the Quran.

@pilgrimoutdoors-uk6177 3 года назад

Flat earth followers are still claiming CGI ...

@sizzla123 10 лет назад

meh

@twinboost 9 лет назад

Is this the only evidence that light has speed , pretty flimsy really. Why is Doppler not considered , Eg; The 2 planets moving away - moving toward each other in respective orbits. Jupiter's moon Io the frequency 'cycle' , just as the beat "cycle" of music playing in a fast car heading toward the observer the beat is at a faster tempo than when the car is travelling away from the observer.

@Graymenn 8 лет назад

Holy derp if it was already established that jupiters moon appeared to do a full orbit in PRECISELY 42.5 hours the how the hell did they re establish that it now appears to slow down or speed up sometimes.... There is a logical fallacy here.

@yosefkap 8 лет назад

I kinda get the impression, especially as it said in the video, that it became consistently established "at a certain time of year". Then, as life went on, and the time of year was 'different' enough, the distance between earth and Jupiter was now further away.. Maybe six months later? Just thinking out loud..

@Geelar 7 лет назад

Well Roma only discovered the time difference in observation after months and years have passed not hours or days

@doc-holliday- 6 лет назад

We're talking about a time difference due to the speed of light of 12 total minutes from closest orbit to furthest. So they took measurements that would change depending on the time and date, but would always be the exact same if taken on the same date and time as a previous measurement. Thus Ole Rømer worked out that the orbit was constant but the distance changed so the light must take time to travel from the moon to their instruments.

@thekaiser4333 9 лет назад

He didn't measure it.

@thekaiser4333 9 лет назад

Aaron Ritter How did they measure the distance to the sun and to Jupiter? I'd say without a starting point it is rather impossible to triangulate.

@sweiland75 6 лет назад

Just say billion instead of million million.

@livintolearn7053 6 лет назад

sweiland75 Dude, a billion is 1000 millions...

@upaste 6 лет назад

a billion is not a million million, it is 1,000 million.

@fromnorway643 5 лет назад

Depends on where you are in the world! In Norway one billion means one million million, while we use the word _milliard_ for 1000 million. The same system ( _the long scale_ ) is used in many European languages, like Spanish, French, Dutch, German and the other Scandinavian languages.

@greathey1234 10 лет назад

I respect professor cocks but honestly the speed of light is still a buzzler. If einstien says it's constant regardless of the speed of the emitting object then certain lights would have different speeds. I am confusef

@DerringerHK 10 лет назад

I think it means that to the observer the speed of light is always constant. This probably makes more sense when we think about the fact that it takes a certain amount of time for our eyes to perceive objects.

@greathey1234 10 лет назад

you seem like a knowledgeable guy. If an object moves so fast, time changes pace according to mr einstien. How does that work since it moves towards a point and away from another? Does that mean light constant speed changes time at both directions effectively making time flow slower towards destination and faster from where it left?

@AlexKarantza 9 лет назад

greathey1234 In a sense; if only time stretched, then you'd be right, things would be inconsistent. But relativity shows that space also stretches to compensate. Someone traveling from point A to point B not only sees their trip taking less time, but also as they're traveling, they'd observe the distance from A to B to be less as well! And equally, a stationary observer would see the traveller squished in the direction of motion, and traveling slower. When you do out all the math, with these two stretches, everyone once again agrees.

@joels2923 9 лет назад

ya know the change in pitch you hear when a firetruck or police car passes you? That's exactly what happens with light. Neither the fundamental speed of light or the speed of sound changes, but the frequency at which it is measured does. So, to answer your question, objects emitting light, and moving towards us, appear slightly blue (higher frequency).

@isaiahphillip4112 9 лет назад

Time yields to accommodate the fact that the speed of light never changes, this is a demonstrable fact.

@virenk1234 7 лет назад

The explanation is completely baseless. I saw this video and was totally confused how is it possible that two events that happened at fixed time intervals (emergence of Io), say T minutes apart will be seen differently from Earth irrespective of its distance from Jupiter. The i had to go through many videos over internet to find the right explanation. Wiki offered the accurate explanation. The two packets of light travelling from Io, when they start at point of emergence will always remain T minutes apart. What Ole observed was actually the doppler effect. When Earth was moving away from Jupiter, the two packets will arrive at some gap (because Earth is continuously moving away with velocty v). When Earth was moving towards Jupiter, Ole was actually observing the time interval between immersion. Since Earth is now moving towards Jupiter, as per doppler effect, the gap will seem lesser.

@denbecr49 5 лет назад

"completely baseless"? You have not found a "better" explanation on Wiki merely because it's the one you more readily understand. The fact that Io's orbit appears behind schedule (average observed time per orbit) at Jupiter's furthest distance and ahead when it's closest was accurately understood and calculated by Romer by ascribing a finite and specific speed to light. Wiki's mention of the Doppler explanation is only an unusual way to invoke Doppler to describe the frequency of an observation of a moon's orbit as an analog to the actual vs apparent frequency of a sound wave or a light wave, but it's no more or less logical. Doppler came along long after Romer and merely distilled and summarized an effect that could have been deduced and generalized from Romer's data. That's why referencing Doppler is considered an "anachronistic" (but not wrong or better) explanation.