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[Music]

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light we all know it travels it well the

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speed of light or does it when it comes

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to the structure of space and time could

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light be the key to unlocking the final

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secrets of the universe answers may lie

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in the journey of two photons across

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seven billion light-years of space

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recorded by the Fermi gamma-ray Space

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Telescope and these two tiny particles

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have just opened up a whole new chapter

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an understanding of light gravity and

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the universe around us we're really

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excited because we've captured rare

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experimental evidence probing the

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fundamental structure of space and time

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meet NASA's gamma-ray detectives led by

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project scientist Julie McEnery they're

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searching for clues about the

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high-energy mysteries of our universe

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but they'll need more than a magnifying

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glass for this the team is one-of-a-kind

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tool the Fermi satellite

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family looks at gamma rays the highest

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energy form of life and it just

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surprised everyone with the discovery

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so you might be thinking to tiny

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particles of light why is that important

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well you need to take the very large and

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the very small

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together to understand the universe as a

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whole so far

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Einstein's theory of relativity which

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describes space and time as a smooth

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fabric that's distorted or bent by

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massive objects has been a spectacularly

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successful explanation of gravity and

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the large scale behavior of the universe

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whereas quantum mechanics another

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spectacularly successful model describes

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the workings of atoms subatomic

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particles and some of the fundamental

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forces of nature but scientists have

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never been able to reconcile the two

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both relativity and quantum mechanics

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are equally fundamental in their own

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regimes so scientists want to find a

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theory of everything just that describes

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the universe as a whole and the

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observations that we've made of these

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two photons with firming takes us one

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step closer to achieving the goal of

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having a theory of everything that

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combines the most successful aspects of

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quantum mechanics and relativity into

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to add to this puzzle other telescopes

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have observed gamma rays with different

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wavelengths arriving at Earth at

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different times according to Einstein's

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special theory of relativity all forms

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of electromagnetic radiation from radio

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and infrared to visible light to x-rays

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and even gamma rays moves at the same

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speed so what would explain these

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differences in arrival times one simple

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idea is that maybe the photons were just

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emitted at different times more

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interestingly though maybe there was

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something in the very fabric of space

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that was causing the higher energy

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particle to slow down if this is true

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could Einstein have been wrong could a

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higher energy particle move slower than

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the speed of light several ideas which

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attempt to reconcile relativity in

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quantum mechanics suggests that space

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and time are not actually smooth and

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uniform but are instead a seething froth

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when seen at the smallest scale like

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bubble wrap viewed from far away at

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human scales this texture would be

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invisible a low-energy long wavelength

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photon is unaffected by the lumpiness of

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space but a high-energy short wavelength

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photon is hindered by the Frog this

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makes it move more slowly than lower

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energy radiation so it breaks Einstein's

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law that all light particles must travel

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at the same speed however this

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explanation had little experimental

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proof either way until Fermi arrived

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[Music]

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we observed a gamma-ray burst a

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gamma-ray burst is a huge explosion that

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gamma ray bursts produced a large number

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of photons one of which had enormous

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energy very short wavelengths those

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photons traveled 7 billion years to

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reach us and yet the highest energy the

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shortest wavelength photon arrived

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within 900 milliseconds of the lower

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energy photons and that's a little bit

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like racing to speedboats one through

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water and the other to molasses and

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having them arrive at the same time it

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just doesn't happen because Fermi saw no

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delay in the arrival time of the two

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photons it confirms that space and time

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is smooth and continuous as Einstein had

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predicted and it shuts the door on

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several theories of everything that had

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predicted that space and time might be

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so if space-time really isn't just

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invisible bubble wrap what is it

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Fermi has eliminated some ideas from the

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mix and that means we're one step closer

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to potentially unifying relativity and

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quantum mechanics after all science is a

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process of elimination and unless we

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keep eliminating we may never know if

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this theory of everything actually

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exists

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hidden in the math of our universe but

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for now we'll have to keep searching for

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clues beyond our small planet because