What is meant by “the observable universe”?

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  • 1 month ago

    The observable universe is a spherical region of the universe comprising all matter that can be observed from Earth or its space-based telescopes and exploratory probes at the present time, because electromagnetic radiation from these objects has had time to reach the Solar System and Earth since the beginning of the cosmological expansion.

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  • Fred
    Lv 5
    1 month ago

    That would be defined by 1993 corrected Hubble Space Telescope.

    That range could be expanded in the future.

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  • 1 month ago

    Imagine yourself on a ship, in the middle of some large ocean. At best, you can climb the 100-foot mast and see up to the horizon at 11 nautical miles in all directions (roughly 20 km). That is the "observable ocean".

    You try to understand the area around you. You analyze the behavior of waves, for example. Building instruments (like binoculars) you explore the horizon and you see that waves are coming from beyond. You notice the difference between swell (from past winds) and waves (from present winds).  In the end, you determine that the full ocean is more than the 20 km that you can observe.

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    Space is expanding. The expansion is taking place everywhere, including withing atoms and photons.  The rate of expansion is linear.   At the local scale, it is quite small (for example, over the height of an average human, over a period of 70 years, it amounts to the size of one atom).

    Over long distances, it adds up.

    Over a megaparsec (a million parsecs = 3.26 million light-years) it amount to roughly 70 km/s per second). Every second, there is 70 km more space over a distance of one million parsecs.

    Over a distance of 13.8 billion ligth-years, the amount of new space being added every second is 300,000 km. 

    This is the speed of light (300,000 km/s). Any space that is beyond that distance will never be visible for us (the amount of space between us an "it" is growing at more than the speed of light).

    Therefore, 13.8 billion light-years is the extent of the "observable universe".

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    Back to the ship:  you see that waves coming over the horizon must have come from a part of the ocean that you cannot see. Even though the ocean you see (the observable ocean) is only 20 km in radius, you KNOW that the real ocean must be more than that.

    In a similar way, astronomers have determined that the "real universe" is greater than the Observable Universe.  We do not know how large the real universe is, but we have determined that it must be AT LEAST 3 times the size of the observable universe.

    That is our dilemma. We see that what is going on in our universe can only be explained IF (this is a big "if") our universe is at least three times bigger than what we can see.

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  • Zirp
    Lv 7
    1 month ago

    That part of the universe from which light and other electromagnetic radiation has had enough time to reach us

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  • The Big Bang is probably something like a trillion times larger in radius (and a trillion trillion trillion times larger in volume) than the "observable Universe".  Looking further and further out in distance, once you're looking out 13.7 billion lightyears you can see all the material whose light has had a chance to reach us in the age of the Universe.  That's the observable Universe.  But there's way way more stuff than that, due to the epoch of "early inflation" in the first fraction of a second of the Big Bang.

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  • 1 month ago

    It means as distant as we can detect something

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    • Ronald 7
      Lv 7
      1 month agoReport

      Exactly as it says on the Tin

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  • 1 month ago

    It is the part of the universe from which light has had time to reach us. Light that was emitted near the beginning of the universe has had 13 billion years to travel to us. But space has been expanding the whole time. So the objects that emitted that light are now 46 billion light years away. That is the observable universe. 

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  • 1 month ago

    This means ,there are still many non observable things in the universe remain ,outside the imagination and knowledge of mankind to fathom. For instance, those lives forms whom being created from the radiant and heat energy that are performing their missions without man knowing it, since mankind  being created from the clay of earth who posses many limitations.

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  • Clive
    Lv 7
    1 month ago

    What it SAYS.....

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  • Dze
    Lv 7
    1 month ago

    we can only see so far .. and what we do see 'way out' is really just looking back in time the way it was when the light left its source ...

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