How can the universe be 15 billion years old and 150 billion light-years wide?

Question

How could the distance across the universe in light-years be greater than its age in years?

I mean, I thought the farthest distance between two points could only be 2*15bil = 30 billion light-years.

Light could only have traveled 15 billion light years in any direction, so the max distance between two points can only be 30 bil LY, right?

Answer 1

I think your problem is that you're thinking that space only expands in one direction. If the Universe did expand in one direction, then the two figures would be the same. But the Universe is spreading in all directions. This makes the Universe"s dimensions exponentially larger than its age.

Answer 2

By your use of the phrase 'distance across the universe' it seems that you're assuming that the universe has an edge or border which also implies a center to the universe. For those concepts to work requires that there is some "thing" or "place" other than our universe, and there's not one shred of evidence that such is the case. In other words, the Big Bang happened every "where" at once -- it has no center or borders. Think about the surface (and ONLY the surface) of a perfect sphere; it has no border, no center, no edge.

Astronomers tell us that the universe is some 13.7-billion years old, which could be taken to mean that its 'edge' is 13.7-billion light years away. However, what astronomers are talking about is simply how long ago they believe the Big Bang event happened.

Answer 3

Where do these people get their "facts?" The positions and movements of nearby stellar objects can be used to infer that the "Big Bang" occurred about 45 billion years ago. There is no indication that the Big Bang was the "beginning" of the universe.

The terms "beginning," "end," "width," and other dimensional limits imply a human understanding of time and space, as if the universe was a house whose construction date can be known.

There is no indication that the universe has "edges," or a "width," as if it was a sheet of plywood. It is necessary for us to understand that the reality in which we are immersed occurs on a scale that we cannot imagine.

In terms of astronomical measurements, it is clear that the distance to the farthest stellar oblect has not yet been determined. It may not be possible to find that.

By the way, the Milky Way galaxy is about 200,000 light years across, and about 16,000 light years thick at the center bulge. All of these figures are readily available.

Answer 4

No one knows how long the Universe has been around. You might be thinking about our galaxy. It's about 150 billion light years wide. That's how you measure length over great distances. Light will take 150 billion years to go from one end of the galaxy to the other.

Answer 5

Indeed, some of the big brains above hit the answer on the head. The universe is expanding faster than the speed of light. Note, not moving faster, but expanding faster.

I would like to point out that someone above said that space itself was "expanding into the void that is the universe." Actually, no one is sure what is outside the universe or if it is expanding into anything at all. The universe encompasses all space just as it encompasses all time. There is no "outside" the universe just as there is no "before" the big bang. At least not that we can talk about intelligently.


- Cai

Answer 6

What is it about this that you find difficult to believe? It seems perfectly reasonable to me. The Big Bang occurred 15 billion years ago, and expanded into a void that is the universe, which may or may not be 150 billion light years wide. As I understand it, it , the universe infinite when pondered from our idiosyncratic three dimensional perspective, and the best way to envision it is as a moebus jar expanded into three dimensions.

Answer 7

A light-year is a measurment of distance (how far light travels in a year) and has nothing to do with the age of the universe. Just because you assume that light from that part of space hasn't arrived yet, doesn't mean that it doesn't exist.

Answer 8

light only goes so fast in static space, the theory of an expanding universe inplies anisotropic space, which is space that moves (expanding), so to answer your question, a 150 billion light year wide universe only means that the rate of universe expansion is faster than the speed of light.

Answer 9

because the universe has been experiencing "inflation" since its beginning. Below is from a recent article to help you visualize.

Need a visual? Imagine the universe just a million years after it was born, Cornish suggests. A batch of light travels for a year, covering one light-year (which is the equivalent of about 5.9 trillion miles or 9.5 trillion kilometers). "At that time, the universe was about 1,000 times smaller than it is today," he said. "Thus, that one light-year has now stretched to become 1,000 light-years."

Answer 10

Spatial distance between two points can increase faster than light speed.


Consider this:

If two photons (light particles) are released in space in directly opposite directions at the same instant, what is the spatial distance between those photons after one second, according to an observer located at their point of origin?

Both photons are travelling at light speed (299,792.458 km/s = 186,282.497 mi/s) in directly opposite directions, which does not violate any known physical laws, but the distance or space between them is still increasing at double the speed of light.

Now, if you consider the large-scale expansion of space-time integrated over billions of years in conjunction with this concept, the universe can indeed, as a whole, expand at considerably faster than light speed without violating anything we currently understand about physics. Thus, the universe can seem to be much wider than it should be at first glance when one considers the speed of light without both expansion concepts taken into account.

No physical masses are exceeding light speed, in full accordance with relativity, but nevertheless, the distance between points with or without mass can still increase faster than light speed.

See the nature of the apparent paradox?

The photons created shortly after the theoretical 'big bang' can therefore be much farther from its epicentre than can be accounted for by the speed of light alone, making the universe seem much too big with respect to the time passed since that moment.

The 'speed' of space itself is independent of the relativistic limit of light speed, which only applies to things with an electromagnetic component. Can you name a single particle ever discovered that is NOT composed of or directly connected to electromagnetic energy and its motive limitations?

What we call space has no 'substance' under the dominion of the electromagnetic laws of motion and is therefore independent of those motive laws. Consequently, even though nothing can supposedly travel faster than light speed, the space between two points can still increase faster than light speed for the combined reasons stated above.

This in no way violates a single known fact of physics but instead, provides new insights into the mysterious way the natural universe works that escaped our attention before.

This is one reason why the findings were such a surprise to many of those scientists of the old school of thought. Now they will be forced to reevaluate and modify several previous theories to accommodate the new observations.

In fact, I'm not sure how many physics students are aware of it yet, but the 'edge' of the observable universe is accelerating as it expands over time, rather than slowing down as older theories postulated.

Hubble's law of universal expansion is going to need some serious revision because of this discovery, assuming the observations are correct.