My astronomy professor got to the “expansion of the universe” unit and went over how we figured out the age of the Universe using Hobble’s Constant, which is a measurement of the expansion of the space-time fabric that the universe is made up of. Hubble’s Constant came about from the observation that the more distant the galaxy is away from Earth, the faster it travels away from us. Then our professor told us something that is contradictory to the idea that space and time are connected. He told us that the universe is likely infinite in size. Infinity is defined as endless, without boundaries. Keeping this in mind, how far does space go? When we look out at the distant stars and galaxies, could that space be infinite?
Before I go into why the universe must have a boundary, lets talk about the super cool parts of what it would mean for the universe to be without a boundary. If the universe really were infinite in size, then whatever fictional world of characters you could imagine, as long as it abided by the laws of the universe (laws of physics), it would be in existence as we speak. True infinity is to say there is someone out there exactly like you doing exactly as you are doing right at this very moment. So continue reading this along with your new clone. Too bad your clone doesn’t actually exist. The universe is not infinite and this is because the universe had a beginning.
Now let’s slow down and let it all sink in.
- If the universe were infinite in size, it’s “beginning” would have happened at an infinite time in the past.
- An infinite amount of time has not passed.
- The universe began roughly 13.7 billion years ago as predicted by Hubble’s Constant. That means space has only had 13.7 billions years to expand to the size it is today. If the universe had infinite time to expand, the universe would have died a heat death. For those that don’t know what heat death is, essentially it is the certain fate that all of the stars and sources of light in the universe will burn out and the space between the stars will expand so far from each other, the universe will reach a temperature of 0 kelvin – absolute zero, the temperature at which atoms stop motion [zero energy]. However it is not the case that the universe has died a heat death because we are still here.
- Since space and time are connected as one, there cannot be infinite space and finite time, because there is finite time, there is finite space.
Here is the trip, and why my astronomy professor holds strong to the idea that space is infinite, despite how contradictory it is – when we look out into space and examine the distant galaxies all around us, we observe that there is an equal amount of matter in all directions. That is to say that we see no evidence of an edge to the universe. That leads to a couple possible conclusions: One, the universe is much, much bigger than we imagined, making our local ecosystem appear as a smooth drop in an even bigger sea. Or two, the universe began everywhere. When you ask astronomers where the universe began to expand, they are going to tell you that it began everywhere because at the very beginning, all points in space were at a single point, the same point. So what happens when I present my professor with this idea that space has a limit? He tells me that I misunderstand because there is an infinite quantity of points in space.
Well I am stuck. Are there infinite points even though not infinite time has passed on our clock? Maybe my understanding of space-time is wrong, or maybe our understanding as a scientific community is wrong. Logically it seems space can only be finite in size. There must be something missing: Relativity.
What philosophers and astronomers can both agree on is that space, at the very least, has a relative boundary. Any light beyond 13.7 billion light years away would have to be traveling faster than light to reach us – which also implies we would have to be traveling faster than light to escape the ‘edge of the universe’. I like to compare the relative edge to our universe as an ‘event horizon’ in a black hole. For those of you that do not know, a black hole is called a black hole, not because it is black, but because it does not emit light (meaning it is transparent and invisible). This is due to the fact that its gravity is stronger than the required velocity for light to escape it. The point at which the escape velocity exceeds the speed of light is called the ‘event horizon’. Am I sneakily pointing out that our universe exists within a black hole? Maybe.
What are we to make of all this? Are space and time really connected as one or are they separate and the universe is infinite in size but not infinite in time? Let those with integrity examine what is being said and decide for themselves the implications of infinity.