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  • Understanding the vast scale of the Universe is no mean feat

  • but Hubble has helped us to understand the skies around us.

  • It has peered far away to the very edges of the visible Universe

  • and taken snapshots of space as it appeared deep in the cosmic past, billions of years ago.

  • Episode 68: The Hubble time machine

  • Presented by Dr. J, aka Dr Joe Liske

  • The Universe is a very big and very old place

  • The distances and timescales involved in astronomy are sometimes difficult to wrap your head around

  • For example, we usually think of the Solar System as being a pretty big place

  • after all, it would take nearly 600 years to travel out to Neptune at the speed of an average passenger jet.

  • But on a cosmic scale, the entire Solar System is just a tiny, tiny speck.

  • As we can't travel to other galaxies or star systems and view them for ourselves

  • we rely on telescopes like Hubble.

  • One of the main scientific justifications for building Hubble

  • was to measure the size and age of the Universe.

  • This task has produced some of the telescope's most iconic images,

  • taken as Hubble peered into the faraway Universe to see what galaxies looked like in the past.

  • So how is it possible that Hubble can look into the past?

  • Well, that's because, just like a spacecraft, light also travels at a finite speed.

  • At 300,000 kilometres per second, this speed is very high, but it is still finite.

  • That means that, in principle, everything we see is a thing of the past.

  • Now normally, in our everyday lives, it doesn't matter, because the distances are just too small.

  • But when we look at the Moon, we see it as it was about one second ago.

  • The Sun we see as it was about eight minutes ago.

  • For the nearest star it's about four years,

  • and the edge of our galaxy we see as it was about 100,000 years ago.

  • As we look further, these thousands of years turn into millions, and even billions,

  • right back to when the Universe was very young.

  • We see these galaxies as they were in the very distant past

  • Galaxies near to us are fully-formed, seen as sleek spirals and smooth ellipticals

  • As we travel further back we see toddlers that are rough around the edges, still in the middle of evolving into fully-grown galaxies.

  • Nowhere is these seen better than in the Hubble Deep Field images.

  • To create these images, Hubble gazed at the same patches of sky for very long periods of time

  • gathering enough light to see extremely faint and very far away objects.

  • These images show some of the most distant galaxies that have ever been observed,

  • going back an incredible 13.2 billion years to a time when the Universe was only about half a billion years old.

  • This far back in time, our Milky Way may have just formed

  • However, the Earth only made an appearance just under 8.5 billion years later

  • The entire history of the Earth has taken place over just a third of the Universe's lifetime

  • from the Earth's formation, to the emergence of dinosaurs,

  • early life, and humans,

  • to the present day, where astronomers use Hubble to view some of the Universe's earliest inhabitants and explore our origins.

  • So how do we know what these very distant galaxies look like today?

  • Well, we can't know for sure.

  • We do know, however, that the Universe on very large scales pretty much looks the same everywhere.

  • That means that, today, these very distant galaxies will look very similar to the galaxies we observe in our local patch of the Universe around us.

  • Vice versa, by looking at these distant galaxies we are also, in a way, observing our own past.

  • Hubble is still searching the distant Universe for clues about how the Universe formed, and how it has evolved.

  • Several of Hubble’s surveys, for example CANDELS, CLASH, and GOODS, are scanning for distant supernova explosions,

  • objects that are good celestial distance markers.

  • Observations of distant supernovae led to the discovery that the expansion of the Universe is accelerating,

  • which earned three astronomers a Nobel Prize in Physics in 2011.

  • Using Hubble, we can observe the Universe as it once wasgoing back to a time before the Sun, and perhaps even the Milky Way, had even formed.

  • Hubble’s successor, the James Webb Space Telescope, due to be launched in 2018, will push this frontier even further,

  • and will perhaps even allow us to observe the very first generation of galaxies to have formed in the Universe.

  • This is Dr J, signing off for the Hubblecast. Once again, nature has surprised us beyond our wildest imagination.

  • The Hubblecast is produced by ESA/Hubble at the European Southern Observatory in Germany.

  • The Hubble mission is a project of international cooperation between NASA and the European Space Agency.


  • Transcribed by ESA/Hubble. Translation --

Understanding the vast scale of the Universe is no mean feat

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Hubblecast 68: The Hubble time machine

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    richardwang posted on 2015/11/19
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