The history of the Universe in the blink of an eye

When you look at something,
you’re looking into the past. See this bowl of petunias?
What you’re actually seeing is what the petunias looked like
a tiny fraction of a second ago. That’s because light has a finite speed. Take this star. Its light takes four years to reach Earth. So we can only ever see it as it was four years ago. The further you look out into space
the further back in time you see and astronomers can use this to explore
the history of the Universe. Space is full of electromagnetic radiation. Astronomers can detect signals from nearby stars… …from other galaxies… …from the gaps between galaxies… …and from nearly the beginning of time itself. All these signals are from different distances
and therefore different times. But they arrive all at once. It’s kind of a mess. Luckily, astronomers have ways to
separate everything back out. And one way is to look for a special signal
hidden in the noise: the 21cm line. This signal is produced by the most common
element in the Universe: hydrogen. Hydrogen atoms absorb and emit radiation at
a specific wavelength of 21cm. And because hydrogen’s pretty much everywhere,
the 21cm line should be too. But there’s more. Because the Universe is expanding, electromagnetic
waves stretch as they travel across it. The further away from us something is,
the more the waves stretch, including the 21cm line. So by looking for that faint signal, and working
out how much it’s been stretched, astronomers can start to put dates to the
waves they’re detecting. Each of these layers comes from a different
moment in the history of the Universe, from last Thursday… back to almost the
beginning of time. The radiation that has travelled the furthest,
the oldest visible layer, is the Cosmic Microwave Background. This is the remnants of the first light that was able to travel freely through
the universe after the Big Bang. It’s spent 13.8 billion years getting here and it’s like an opaque wall,
beyond which there’s nothing to see. Next came the dark ages, when hydrogen atoms
spread out through space not really doing much. That is until the first stars formed,
and then the first galaxies. As galaxies grew and merged, they started to affect the hydrogen atoms
in the space around them, ionizing the atoms and forming
bubble-like shapes which appear as dark gaps in
the usual 21cm glow. Astronomers are now building new telescopes
specifically to detect these faint ionized bubbles
from over a billion years ago. They hope that buried within these signals could be answers to some of the Universe’s
great mysteries, like the nature of dark matter. Thanks to the finite speed of light every time we look up we see the history of the Universe in the blink of an eye. And with the 21cm line, scientists are starting to find the secrets hidden within.

Comments 26

  • Such a creative & beautiful way to explain something so… well, creative & beautiful. I lose sleep by staying up & thinking about the universe & happy to do so. Also, I love my cat.

  • Wow, this video got me starstruck!

  • 1st dislike !!!😇

  • This narrator sounds like she was borrowed from a children's cartoon.

  • I like the way you explained that. 🙂

  • I like these videos but it feels like I’m too stupid to understand them.

  • Did you know everything is spiritual consciousness and energy including you some people call it cosmic consciousness are GOD

  • Well done and definitely keep it up!

  • Very well explained & everything about the video was perfect, thank you 🤗

  • How can we be sure that the wavelengths are expanding due to the expansion of the universe vs, which could be seen as more intuitive to someone outside the field, their decay in frequency over such a long time?

  • A positively wonderful video!

  • What a lovely little vid. Enchanting, very well done, thanks.

  • What a lovely little vid. Enchanting, very well done, thanks.

  • Here before 1 million views.

  • Excelent vídeo. Incredible.

  • How the ionized H bubbles could answer about dark matter?

  • Great work. Please keep producing more videos like this.

  • I know it's already bloody long, but still I wonder why the length of electromagnetic waves can't surpass 21 cm (if that's also the length of the cosmic microwave background radiation).

  • mkay. Many things just delivered as facts. Hydrogen radiation? Why? How? Why microwave radiation and not any other wavelength? not very scientific for nature… 🙁

  • Great video!

  • Nice presentation

  • Simplicity is the ultimate sophistication

  • Please create a collider destroying the elementary particle
    Such as quarks, electrons and gluons
    We want this new collider to be stronger than the CERN collider
    But the new collider must be hundreds of times smaller than that of the CERN
    The question is can you build a small collider at the same time stronger than the CERN collider
    Please send the question to physicists and engineers
    A smaller collider must be smaller than a CERN collider
    Hundreds of times smaller than CERN Collider but dozens of times stronger than CERN Collider!
    This invention in order to create a new collider in the fastest time
    We hope these engineers and physicists will find new plans
    In order to build a new collider at the same time, dozens of times stronger than the CERN collider
    We want to discover the components of quarks and gallons by destroying quarks and gallons
    This is in order to detect quantum gravitational particles
    So we can explain the initial events before the Big Bang that created this universe
    About 13 billion and 800 million years ago
    Please send these suggestions to experts and engineers


  • This is the most pleasuring and also exciting thing what i saw in months.

  • An amazing collection of unproved assumptions presented as facts. That's not science, that's a religion. And all presented by a sub-microscopic still evolving brain in an emense Universe, a brain with such an enormous ego that it pretends to underestand the Universe. Plus all the well trained sheep in the echo chamber pretending to understand — unbelievable.

  • i interpret the bowl of petunias as a Douglas Adams reference

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