{"id":353,"date":"2018-01-26T16:29:18","date_gmt":"2018-01-26T16:29:18","guid":{"rendered":"https:\/\/vedantaandscience.com\/?p=353"},"modified":"2018-01-29T14:35:28","modified_gmt":"2018-01-29T14:35:28","slug":"hubble-constant-and-expansion-of-the-universe","status":"publish","type":"post","link":"https:\/\/vedantaandscience.com\/?p=353","title":{"rendered":"Expansion of the Universe"},"content":{"rendered":"

Does the universe expand? Science tells us the universe is expanding. Why is the universe expanding? How fast the universe is expanding? Science is not very sure about these questions. Using powerful telescopes, they have watched the movement of different planets and galaxies and noticed the expansion is uneven. Some places the expansion is faster and other places the expansion is slower. There is no explanation about this uneven expansion. Looking at some far away planets and looking at their rate of expansion, they have come up with a Hubble constant. The Hubble constant states that the rate of expansion <\/span>is about 71 kilometers per second per megaparsec. A megaparsec is a million parsecs, or about 3.3 million light-years. It means objects 3.3 million light years away are expanding at 71 kilometers per second. This is based on observation only. If you understand the fundamentals of the universe expansion, it is possible to calculate and prove the Hubble Constant. We will be doing this in this article.\u00a0<\/span><\/span><\/p>\n

So, what are the fundamentals of this expansion? Understanding the spacetime fabric is the key to understand this expansion. We have discussed the spacetime fabric in other arrticles. We have seen that the individual person or the observer location is the start point for the spacetime fabric. We can call this the t = 0 for the spacetime fabric. We have seen that the spacetime fabric is a time-based fabric in which different objects are placed depending upon the time light takes to reach the observer from these objects.\u00a0 <\/span><\/span><\/p>\n

What is the maximum size of the spacetime fabric?\u00a0 Science tells us that the age of the universe is 13.7 billion years old. This is the big bang moment. Light reaching us from the big bang moment would be the outer edge of the spacetime fabric. Light will take 13.7 billion light years to reach us from this big bang moment. This is the outer edge because there was no universe before the big bang. So, the size of the universe: 13.7 billion light years or 12.9 x 1025<\/span><\/sup> meters. One light year is the amount of distance light travels in one year, which is = 9.46 \u00d7 1015<\/span><\/sup> meters<\/span><\/p>\n

Is this spacetime fabric expanding? Definitely, yes. How much? Let us try and understand this. If you assume the universe is 13.7 billion years old \u2018right now\u2019. After one second, the age of the universe will be 13.7 billion years + 1 sec. Light must now must travel an additional 186,000 miles to reach us, which means the size of the universe has grown by 186,000 miles. After 10 seconds, the size of the universe would increase by 186,000 x 10 = 1,860,000 miles. After one year from now, the size of the universe will increase by 1 light year. 1 light year is the distance light travels in one year. <\/span><\/p>\n

From the above, we can conclude that the rate of expansion of the Universe = 1 light year per year. <\/span><\/p>\n

If you can imagine the spacetime fabric as an elastic rubber sheet, starting from the start point t=0 (which means you) to the edge of the universe. The end at the observer\u2019s side is fixed it is always the t = 0; the other end which is the outer edge of the universe is being pulled outwards. This elastic space time fabric is expanding by 186,000 miles every second. It is expanding at the speed of light every second, which is one light year every year. As time flows, the expansion of the spacetime fabric will continue at the speed of light. <\/span><\/p>\n

It must be understood that only the edge of the universe is expanding at the speed of light, anything in between will not expand at the same speed, it will be proportional to the distance from the observer. Using the rubber sheet example, if you pull the outer edge by a certain distance, the inner parts will not be stretched by the same amount. The stretching will be more at the outer edges and it will be much less as you move inwards to the other side. This means that the rate of outward expansion of galaxies, stars etc., would really depend upon how far these galaxies are far away from the observer. The observer is t=0. Stars close by will expand more slowly, as compared to stars which are further away. This is because the space time fabric for the stars nearby will stretch less as compared to the stars which are further away.\u00a0 <\/span><\/span><\/p>\n

Based on our understanding of the stretching of the space time fabric, let us try and calculate the Hubble Constant<\/span><\/p>\n