This distance works out to be about 30 billion light years. But we are just guessing that UDFy-38135539 still exists more likely it has merged with other young galaxies perhaps – – becoming part of a huge spiral galaxy similar to our own Milky Way, which itself contains stars that may be over 13 billion years old. The observable, or inferred, universe with a diameter of 93 billion years. Even this may just be a small component of the whole ball game. At this scale, our vast galactic neighborhood, the Virgo Supercluster, is too small to be seen. Credit: Azcolvin429. It is generally said that the comoving distance to the particles that emitted the cosmic microwave background is about 45.7 billion light years away even though the photons those – particles emitted have only been traveling for nearly 13.7 billion years. Similarly, by inference, the absolute edge of the observable universe is 46.6 billion light years away. However, you can’t conclude that this is the actual size of the universe nor should you – conclude that the cosmic microwave background has a distant origin. Your coffee cup may contain particles that originally emitted the cosmic microwave background and the photons – they emitted may be 45.7 billion years away now perhaps just now being collected by – alien astronomers who will hence have their own 46.6 billion light year radius universe to infer most of which they can’t directly observe either. – All universal residents have to infer the scale of the universe from the age of the photons that come to us and the other information that they carry. And this will always be historical information. From Earth we can’t expect to ever come to know about anything that is happening right now in objects that are more distant than a comoving distance of around 16 billion light years, this being the cosmic event horizon (equivalent to a redshift of around z = 1.8). This is because objects are right now receding from us at faster than the speed of light. We may still continue receiving updated historical data about them for many billions of years to come until they become so redshifted as to appear to wink out of existence. But really, – they are already lost to us. Further reading: Davis and Lineweaver. Assumptions April 17, 2011
This distance works out to be about 30 billion light years. But we are just guessing that UDFy-38135539 still exists – more likely it has merged with other young galaxies – perhaps becoming part of a huge spiral galaxy similar to our own Milky Way, which itself contains stars that may be over 13 billion years old. The observable, or inferred, universe with a diameter of 93 billion years. Even this may just be a small component of the whole ball game. At this scale, our vast galactic neighborhood, the Virgo Supercluster, is too small to be seen. Credit: Azcolvin429. It is generally said that the comoving distance to the particles that emitted the cosmic microwave background is about 45.7 billion light years away – even though the photons those particles emitted have only been traveling for nearly 13.7 billion years. Similarly, by inference, the absolute edge of the observable universe is 46.6 billion light years away. However, you can’t conclude that this is the actual size of the universe – nor should you conclude that the cosmic microwave background has a distant origin. Your coffee cup may contain particles that originally emitted the cosmic microwave background – and the photons they emitted may be 45.7 billion years away now – perhaps just now being collected by alien astronomers who will hence have their own 46.6 billion light year radius universe to infer – most of which they can’t directly observe either. All universal residents have to infer the scale of the universe from the age of the photons that come to us and the other information that they carry. And this will always be historical information. From Earth we can’t expect to ever come to know about anything that is happening right now in objects that are more distant than a comoving distance of around 16 billion light years, this being the cosmic event horizon (equivalent to a redshift of around z = 1.8). This is because objects are right now receding from us at faster than the speed of light. We may still continue receiving updated historical data about them for many billions of years to come – until they become so redshifted as to appear to wink out of existence. But really, they are already lost to us. Further reading: Davis and Lineweaver. Assumptions April 17, 2011
AWAT_TheBook_v2.docx