If the universe is only 13-7 billion years old, how can we see objects that are 30 billion light years away?

Answer 1

This seemingly simple question has a surprisingly complicated answer. You might expect that if the earth and one of these distant galaxies had been very near one another at the creation of the universe and had both been moving away from one another at almost the speed of light, that after 15 billion years each would have moved almost 15 billion light years in opposite directions and would thus be separated by almost 30 billion light years. That's not the case. That simple view ignores the important effects of special relativity on rapidly moving objects.

To understand these effects, suppose that there was an observer who was stationary at the creation and watched the earth and galaxy head off in opposite directions at almost the speed of light. From that observer's perspective, the two objects are heading away from one another at almost twice the speed of light. After 15 billion years, this observer sees the galaxy as almost 30 billion light years away from the earth.

Now suppose that there was another observer who was on the earth at the creation. From this person's perspective, the galaxy recedes from the earth at almost the speed of light, but no more. Nothing can move faster than speed of light! After 15 billion years, this observer sees galaxy as almost 15 billion light years away from the earth.

These two observations don't seem to agree. The problem lies in how the two observers perceive time and space. According to special relativity, observers who are moving relative to one another don't perceive time and space in the same way. Their perceptions will be so different that they will not even agree about just when 15 billion years has passed.

With this long introduction, here is the answer to your question: no distant galaxy in the observable universe can ever be farther from us than the distance light has traveled since the creation of the universe. Since that creation was about 15 billion years ago, the most distant possible galaxy is almost 15 billion light years away.

Answer 2

We can't - short answer.
Long answer is, the furthest known extraplanatery object known to man currently is Abell 1835 IR1916, 13.2 Billion light years away. We can neither see a galaxy that is 30 billion light years away, nor is there any evidence that such a object exists.

Now, if we hypothesize that the galaxy was moving away from us at an awesome velocity of .5c (150,000 km/s) we could then "claim" that the object we where looking at was actually 19.8 Billion light years away, currently as we are looking at a picture from 13.2 billion light years in the past.

Answer 3

The furthest objects we can see were 13.7 billion light years away from the Earth's current location--13.7 billion years ago! During those 13.7 billion years, those distant objects have been moving rapidly away from us. In addition, because of the nature of the Universe, it may be possible for the Universe itself to expand at greater than the speed of light, putting those objects at such great distances from us as 30 billion light years.

Answer 4

You're looking this backwards. Our age isn't important, what matters is the other planets age. The light didn't start travelling towards us only when earth was created, it started travelling when they were created. So, if they are less than 30 billion years old the light wouldn't yet have reached us.

Answer 5

We can't. It's all speculation as to what is actually out there. They usually don't use visual telescopes to view the most distant bodies. They are spectroscopes and the like that take data bounced around the galaxy, recieved, and compiled into visual data.

Answer 6

years and light years are "apples and oranges". hard to understand but 13-7 billion years, is a reflection of time, or in this case, age (of the earth) that's the easy part.

Now, Light years is a measure of distance. loosely defined as: travelling at the speed of light (186,000 miles per second), it would take you 30 biillion years to get to this place... unless you have to stop to peee... you gotta factor that in :-)

Answer 7

Because those objects were once closer to us, they are moving away from us thanks to the big bang theory. The light you see is from years ago. Some of that light is coming from some stars or explosions that have already fizzled out. deep, huh?

Answer 8

I would dispute the probability of viewing objects 30 billiion lys away. It is an impossible situation.

Answer 9

Good question. The answer must be that they are travelling away from us. Therefore stretching the time in which we see them.

Answer 10

maybe the universe is expanding faster than the speed of light

either that, or:

the person looking through the telescope is a retard.