The Universe is expanding, so that the furthest visible bits of the Universe are much further away than they were when the light from them set out towards us 13.8 billion years ago. They are now 46 billion light years away. If all these assumptions are correct, the Universe is a sphere 92.2 billion light years across. Although we can’t ‘see’ the outer edge of this sphere (because the light from it hasn’t reached us yet), this theoretical sphere is what is known as the ‘observable’ Universe.
The rate at which the Universe is expanding is known as the Hubble Constant, after Edwin Hubble, who discovered the phenomenon in the 1920s, and after whom the Hubble Telescope is also named. The Hubble Constant is expressed in miles per second per megaparsec (a megaparsec being 3.3 million light years). Although its value is constantly being refined, towards the end of his life Douglas Adams was delighted to hear that it was 42. The latest estimate is just under 45.
Because the Universe seems to be expanding at an increasing rate there will come a time when observers will not be able to see any other galaxies from Earth or any other spot in the Milky Way. Galaxies are moving away from one another, and the galaxies that are farther away look like they are moving more quickly than ones that are closer.
Eventually, everything will be so far away, we will no longer be able to see it.
Imagination is the real and eternal world of which this vegetable universe is but a faint shadow.
The Big Bang was silent.
Specifically, it’s a manhole cover at the intersection of Bank Street and Sixth Street in Wallace, Idaho. In 2004, the mayor, Ron Garitone, declared the spot was officially the Centre of the Universe, on the grounds that no scientists had ever unearthed ‘one scintilla of proof that Wallace is not the center of the Universe.’ As far as the phrase ‘observable Universe’ goes, this is, in fact, as good an answer as any other.
The current orthodoxy among cosmologists is that the Big Bang was not a normal kind of ‘explosion’ in the sense that we understand it, and that consequently the Universe ‘has no centre’. The ‘observable’ universe, however, does have a centre – the observer him or herself.
Edgar Allan Poe's poem 'Eureka', says the Universe exploded into being from a single 'primordial particle' in 'one instantaneous flash.'
A ‘light year’ is not a measure of time, but of distance: It’s how far light travels in a year. Light travels at 186,000 miles a second, so a ‘light second’ is 186,000 miles. A light year is a seriously long way: 5,865,696,000,000 miles (nearly six trillion miles or nine-and-a-half trillion kilometres). For us to ‘see’ anything, light from the object has to reach our eyes. The Sun is 93 million miles (eight ‘light minutes’) away: when you ‘see’ the Sun, you are not seeing it as it is now, but as it was eight minutes ago. The current estimate of the age of the Universe is 13.8 billion years, so nothing we can see can be further than 13.8 billion light years away - and we are not looking at it as it is now, but as it was 13.8 billion years ago.
In the beginning the Universe was created. This has made a lot of people very angry and has been widely regarded as a bad move.
We do not have to visit a madhouse to find disordered minds; our planet is the mental institution of the universe.