promotion image of download ymail app
Promoted

How can we see 46 billion light years in space if Earth is less than 6 billion years old? (please read whole question below)?

If Earth is under 6 billion years old, and we can see 46 billion light years in any direction in space, couldn't we see ourselves, or at least what Earth was before it was Earth?

How can we see 46 billion light years if we are only 5 billion years old? Doesn't that create a paradox?

If a car started at the base of a mountain, and drove forward for 3 light years and then looked back at the mountain, he would be viewing the mountain as it was 3 years ago, and would see his own car there at the base?

I understand that I must be missing something.

I just don't understand how we can see almost 10 times further than the age of our own planet. 46 billion years ago the Earth didn't even exist, and the universe looked very different. 

Updated 2 days ago:

What I'm really asking is if we were to look 5 billion light years in space, where is the Earth relative to what we are seeing?

24 Answers

Relevance
  • 20 hours ago

    We can't. We can detect objects up to about thirteen thousand million light years away, which is the approximate age of the Universe, but that's coincidental. The light which reaches us from them started out at a time when they were closer. It isn't necessary for the Earth to have existed at that time for this to be possible.

    • Commenter avatarLogin to reply the answers
  • nobody can see whats 1 year in earth space or whatever you want to call it.

    for instance, if something is measured in the time it takes to reach it, thats like me saying I am 20 years away from that little male baby that will need 20 years to grow up before it can sit down and talk about naked women and boobies with me.

    do you see what i mean ?

  • 1 day ago

    Because the light from those distant galaxies was already traveling through space long before Earth existed.

  • 1 day ago

    Do you mean that I cannot see the pyramids because I was born after they were completed?

    1. We cannot see 46 billion light-years in space. When calculating distances that we can see, we use "look-back" distance:  if the light took a million years to get here, then that object is a million light-years away. Astronomers calculate distances and positions based on what we see now.

    If a star blows up now, even if that start is a thousand light-years away, we call it "Supernova 2020" and not SN1020, even though we know it blew up a thousand years ago, and the light of the explosion took a thousand years to get here.

    The position of the star would be given as its position where we see it now. We do not try to guess where it would have been a thousand years after the explosion in 1020.

    In this scale of measurement, we can "see" as far as (roughly) 13,800,000,000 light-years (13.8 milliard in long scale unit names, 13.8 billion in short-scale unit names).

    And what we do see at that distance (the Cosmic Microwave Background radiation), we see it as it was 13.8 billion years ago... with the redshift each photon had to endure during its 13.8 billion years of travel from "there" to here.

    2. Cosmologists try to understand the universe, as a structure, the way it would appear to us IF (a big if) we were able to see all of it as it is NOW. This means that whatever we (astronomers) see at 5 billion light-years - where it was 5 billion years ago - they (cosmologists) place it where it would be NOW, considering all the expansion of space that has taken place during these 5 billion years.

    For them, this thing is NOW located at (let's say) 10 billion light-years. However, they do not SEE it at 10 billion light-years. Whatever light this object is emitting NOW will take 10 billion years to get here.

    The distance used by cosmologists is called the co-moving distance. It is the distance where things would be NOW, if we could see them where they are NOW (that is, if the speed of light was infinite).

    The CMB radiation appears to be 13.8 billion light-years away in look-back distance. Back then, it was just a general glow (orange in color) that was simply caused by the temperature of the (mostly) hydrogen gas taking up the volume of space. Around 3000 K.

    If you were to magically see what that looks like NOW, you would NOT see this hot gas. You would see whatever that region of space has become over 13.8 billion years: galaxies, stars, planet...

    And, because space everywhere has been expanding during all that time, these objects would NOW be a little over 40 billion light-years away from us (co-moving distance). But there is no way anyone sees any of these objects at 40 billion light-years. All we see is the "glow" of that region as it was 13.8 billion years ago, when its distance from us was 13.8 billion light-years.

    3. Roughly 8 to 10 billion years ago, within our already existing Galaxy, there were gimongous clouds of gas (mostly hydrogen, some helium) and "dust" (anything else blown out into space by exploding supernovas of earlier stars). Many of these clouds collapsed under their own gravity and caused mass to accumulate in pockets.

    One pocket in one cloud became crowded enough to have a very high pressure (caused by gravity) at its centre. The pressure and temperature were sufficient to trigger hydrogen fusion in the central object: our Sun. Around the Sun, the rest of the matter assembled itself, more or less at random, into planets. That is where our Earth was 4.5 billion years ago. 

    Since the formation of Earth, our Solar system has gone around the Galaxy approximately 20 times, orbiting at approximately 230 km/s relative to the Galactic centre.

    To make things even omore complicated, our Galaxy itself is moving, relative to the Virgo Supercluster (itself moving...).  Relative to the CMB radiation, our Galaxy is moving at close to 400 km/s

  • How do you think about the answers? You can sign in to vote the answer.
  • Clive
    Lv 7
    2 days ago

    Why do you assume the Earth was created right at the beginning of the universe?  It wasn't.  Of course we can see things that are older than the Earth.  Just like you can see antiques that were made before you were born.

    • Commenter avatarLogin to reply the answers
  • 2 days ago

    the light we are and have been receiving is  12-13,000,000,000 years old,the distance limitations owe to gas and innumerable clumps  huuuge clumps of galaxies, glare from massive and old suns out there,floating bodies, until we launch rockets with vastly more powerful light gathering lenses,launching them far enough out where the beyond is much less crowded with gas clouds,we are at a roadblock  in seeing the edge or beyond the edge of creation

    • Commenter avatarLogin to reply the answers
  • 2 days ago

    The Universe is older than the Earth.

    Duh.

    • Commenter avatarLogin to reply the answers
  • 2 days ago

    Light

    And it travels at 186, 000 Miles per Second

    A light year is the distance Light has travelled in a year

    An object One Light Year away, we can see as it was one year ago

    46 Billion Light Years away is also the time ago that the light left it

    We are here on Earth, Base if you like and we can see as far in every direction as long as the Object is Bright enough

    For what is not Bright enough, could it be Dark Matter ?

    Something I would like to add

    HD140283 is pretty standard apparent Magnetude 7. 205

    A Metal Poor and Oxygen rich Subgiant star with a Rapid real movement of 800, 000 mph or how about 1.3 Million Km/ hr

    In respect to earth though that is the width of the moon In 1, 500 years

     It has been studied for 100 years now

    A Type 2 Star where our Sun is a Type 3

    Type One Stars were the first to ignite from the Cosmic Soup

     Its given age  is 14 Billion years

    Nicknamed Methusila it has a Highly Eliptical Orbit

    from the outside edge of the Milky Way to across the Galactic Arms

    180 Light Years away from 200 light years in less than one year

    Say there was an Earth like Planet orbiting in its Goldilocks Zone, and why not

    How much of an Evolution could it have by now and it is coming this way

    Attachment image
    • ...Show all comments
    • Ronald 7
      Lv 7
      1 day agoReport

      And just how far has it expanded and what into. It is about time you folks got a big taste of reality.... Watch out for that Asteroid !!!!

    • Commenter avatarLogin to reply the answers
  • 2 days ago

    We're not looking back in time, we're looking at light emitted from sources that are 46 billion light years away. This means that the light was EMITTED 46 billion years ago, 40+ billion years prior to our planet forming. We're not looking at our own planet as it was billions of years ago, we're seeing light from a source that most likely no longer exists. It took that light 46 billion years to cross the 46 billion light year distance. Understand?

    So you're asking where the Earth was, 5 billion years ago relative to an object 5 billion light years distant?? Assuming that was after the earth formed, the Earth was right here in orbit around our sun. 

    • Commenter avatarLogin to reply the answers
  • 2 days ago

    Under your feet, the Earth is still there, not out in space.

    You are confusing the starlight coming from the great distances beyond our galaxy, billions of lightyears, with the age of Earth, measured in years.

    The word "years" is used in both, but have nothing to do with each other.

    Lightyears is a distance measurement.  One lightyear is almost 6 trillion miles long.  4.3 of them is distance from Sun to Proxima Centauri, closest planet outside the solar system.  Years by itself is a time measurement.  One year is how much time passed in months, weeks, days, hours, minutes, seconds to travel once around our sun.

    If there was a giant mirror in space, covering a huge area, and was 2.5 billion lightyears away, you could look at the bounced image of Earth just being formed.

    The round trip of light from earth from 5 billion years ago would be reaching you just now.

    Light from farther away than 5 billion lightyears is reaching you just now.  That light left the source, stars in other galaxies, way before Earth formed.

    • Commenter avatarLogin to reply the answers
Still have questions? Get your answers by asking now.