In which direction in the sky did the big bang take place 13.8 billion years ago?
Luce Gilmore
Cambridge, UK
Advertisement
The big bang was the origin of space and time (as well as matter and energy), hence it happened everywhere.
Mike Follows
Sutton Coldfield, West Midlands, UK
The universe doesn鈥檛 have a centre we can point towards. This is because the big bang wasn鈥檛 a conventional explosion. If it were, you would be able to track the debris back to its origin and to a point in the sky. Instead, the big bang was the instant that both time and space were created. The space between galaxies is increasing with time.
The universe is isotropic and homogeneous, which means that it looks pretty much the same in all directions and reasonably sized samples appear identical. From our perspective, it appears as if the universe is expanding away from us. Aliens in other galaxies would also have the same perception: that the universe is expanding away from them in all directions, as if they are at the centre.
Of course, we can鈥檛 both be correct. Instead, we are all probably wrong and the universe probably doesn鈥檛 have a centre.
Stan Williams
Sevenoaks, Kent, UK
The abstract ideas that cosmology raises are often very difficult to intuit.
The question of where the big bang took place is inherent in the cosmological principle, which states that the cosmos, at least on intergalactic scales, is uniform in all directions. This implies that there is no special place in the cosmos. Everything is relative to where you are, which, of course, is the starting point for Albert Einstein鈥檚 great theories.
Many years ago, I discovered a lovely way to think about this inscribed on a wall inside a church in the Dee valley in Aberdeenshire, UK. The message said: 鈥淭he Universe is a Circle whose Circumference is Nowhere and whose Centre is Everywhere鈥�.
So the answer to the question is that the big bang happened in whichever direction you care to look. And you will never find its boundary.
Herman D鈥橦ondt
Sydney, Australia
The big bang took place everywhere in the universe 鈥� it was the universe. Hence, regardless of where you point, you always point in the direction of the big bang. The cosmic microwave background radiation, released when the universe was 380,000 years old, looks the same in every direction.
Imagine you are an ant living on the surface of a huge balloon. For the ant, the surface is its entire universe. The inside or outside of the balloon can鈥檛 be observed. Now, imagine the balloon expanding. For the ant, there is no direction from which the expansion started, it is happening everywhere, in all directions. It is a bit like standing at the South Pole and trying to point in the direction of north. At the South Pole, all directions are north.
To answer this question 鈥� or ask a new one 鈥� email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.
91色情片 retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.
听