View Full Version : How far to the other side of the Universe?

2003-Sep-17, 08:08 PM
HI fraiser If the big bang is true ,we could launch a craft set a course how long would it take for the other side of the universe to reach us if we stay in the same place.

2003-Sep-17, 11:00 PM
No one can really answer that because for 1) we don't know how fast the universe is expanding, and 2) we don't know how big the universe is, let alone from a given point, we can only made very crude guesses as to how big it is enirely. (we don't even know where in the universe earth is)

2003-Sep-18, 12:44 AM
The problem with sending a rocket or something out to the other side of the universe is ... there is no other side of the universe.

The universe can't be thought of as a something expanding into a something else. Pretty hard to get your head around but them's the breaks. The only thing the universe is expanding into is itself. There are quite a few other threads here that have spoken to this point. I'll do a bit of a quick search and try and find one of them for you.

2003-Sep-18, 01:08 AM
here is one such topic ...
http://www.universetoday.com/forum/index.p...p?showtopic=389 (http://www.universetoday.com/forum/index.php?showtopic=389)

2003-Sep-18, 09:29 PM
He said keeping the rocket still, how long would it take for the other side of the universe to expand to you or something like that.....maybe I read it wrong...

2003-Sep-18, 11:54 PM
Please lets not do the what was the origanal sentence.. It was if we launched a ship how long would it take to reach the other side,it cant ,because it is expanding away not toward but if our universe moves do we stay in one place or do we move with it.

2003-Sep-19, 01:30 AM
Did you ask a trick question on purpose? I feel like hitting myself hmmm... wasn't thinking.

Keith Chandler
2003-Sep-19, 01:39 AM
[SIZE=1] It doesn't take any time at all. All you need, according to Doug Adams, is a space vehicle equipped with an Infinite Improbability Drive, "a wonderful method of crossing vast interstellar distances in a mere nothing of a second, without all that tedious mucking about in hperspace."

It's not difficult to construct an Infinite Improbability Drive. To quote Adams, "The principle of generating small amounts of finite improbability by simply hooking the logic circuits of a Bambleweeny 57 Sub-Meson Brain to an atomic vector plotter suspended in a strong Brownian Motion producer (say a nice hot cup of tea)" has long been known. The actual procedure was discovered by a lab student reasoning as follows while he was sweeping up the lab at night:

"If, he thought to himself, such a machine is a virtual impossibility, then it must logically be a finite improbability. So all I have to do in order to make one is to work out exactly how improbable it is, feed that figure into the finite improbability generator, give it a fresh cup of hot tea . . . and turn it on!

"He did this, and was rather started to discover that he had manged to create the long-sought-after golden Infinite Improbaility generator out of thin air." Try it and join me for a drink at the Restaurant at the End of the Universe.

2003-Sep-19, 01:54 AM
Are you feeling ok?

2003-Sep-19, 08:11 AM
i hate to rain down on ur parade nelson but if we are a part of the universe ( and last time i checked: we were) we r expanding with it...
and also if we r inside the universe...then expanding means driving away from the center...which would mean away from us....so the other side is moving - wait for it- away from us!!

but i think everything i just sed everyone has realised by now =p

P.S. keith i been the that resuarant..i like the steak and chips they have their ; )

2003-Sep-19, 02:53 PM
Hi Nelson,

Here in Scotland where I live we like to think our legal system is better than the English or most others, as an accused can be found ‘Guilty’, ‘Not Guilty’ – or the case can be found ‘Not Proven’. It might be advantageous if scientists would take this notion on board, as while there are indeed great piles of evidence that our Universe is expanding – almost everything seems to be flying away from everything else – the case, so far as I can see at any rate, is really ‘Not Proven’. Andromeda, for example, is flying towards the Milky Way, not away.

If the Big Bang is true, you did say, then those who say it would take forever or would never happen are correct, obviously if we stay in the same place – which you also stipulated, but at this stage it is not only true that the Big Bang itself is ‘Not Proven’, but we don’t really know the shape of our Universe. Should String or ‘M’ Theories turn out to be so, we don’t yet even know for definite how many dimensions it has. Perhaps the space-time element of our Universe is shaped like a Klein bottle or a Moebius strip and the matter part is altogether only taking up a small part of it and expanding away round and round. Maybe sooner or later the matter part will come up against an edge of space and stop expanding. We just don’t really know.

O.K., I was going to say at this point that I do agree the chances are the astrophysicists are right – but they’ve never ever been right before, so why should they be correct today? Every generation in human history seems to have lived through a different main cosmological belief. It has recently been shown that the speed of light may vary, perhaps according to the frequency of the photons concerned. Indeed, this has already been used to explain some cosmological phenomena. In 1994 Miguel Alcubierre came up with his ‘warp’ drive, a la Star Trek, and attempts to disprove his hypothesis have themselves been disproved.

The day may come when it does become possible to visit that restaurant at the end of the Universe. Science is always moving on. Tomorrow’s theories will differ from today’s, so let’s keep optimistic!

How did you travel when you visited the restaurant, Decimal?

Best wishes,

Andy Nimmo.

2003-Sep-19, 09:40 PM
When I was but a youth, I remember a BBC TV show called Cosmos, hosted by Carl Sagan (Bless His Heart!). In one episode, he announced a theory that by looking out into the universe, we are looking back in time. Perhaps he was saying that we ARE at the end of the universe. There is no "other" end. If so and we get in a space ship and head toward the center of the universe, the best we can hope for may be to travel our fastest in order to stop time for ourselves in the ship. Maybe only then could we look where the rest of the stars have been travelling and see an "end" to the universe.

2003-Sep-20, 01:56 AM
To answer Guests post ...

While common vernacular means that scientists say that they are certain of one thing or another this is not really the case. All science is based on being able to disprove something not prove it. According to science - which is based on hypothesis and premises - nothing can be proven, only disproven. When you can test for something to be disproved, then that is science. This is the notion of falsification (see the work of Karl Popper) which came out of the following formal logic argument:
"If the theory is true, then the prediction is true.
The prediction is not true.
Therefore, the theory is not true."
We can see this working when we look at the work of Einstein and Newton. For hundreds of years Newton was correct in every way. His work and ideas had been "proven" over and over. Then came along Einstein and showed that once you got to very fast speeds (approaching light speed) and very big distances, then Newton's theories fell apart. So something that was essentially "true" and proven became untrue. Only through setting up a test or experiment that can falsify something can you study science. If something can't be given such a test - like psychoanalysis, dream interpretation or theology - then it isn't science.
So, all science is "Not Proven". Things only become accepted as true if the theories they are based on hold over and over when put to the test.

2003-Sep-20, 03:57 PM
The only thing that seems to be expanding is general ignorance(and poor spelling) :(

2003-Sep-22, 03:56 PM
Maybe you are asking about the size of the universe. One way of looking at it would be: IF the universe could not expand at a rate faster than the speed of light, THEN it could not be larger than its age in light years. The last figure I remember is about 13.7 billion years for the age of the universe so this would mean that the radius of the universe would not be larger that 13.7 light years. As for getting there in a rocket that we could build, that would not be possible.

2003-Sep-24, 01:23 AM
Your question is wide open for interpretation. Regardless of what you are asking, however, no one could answer that. (As many intelligent folk before me have posted)
Not only do we not know what rate the universe is expanding at........We don't know IF the universe is actually expanding, contracting, or pulsating!!!!

If, for arguments sake, we assume that the big bang theory is fact and the universe is expanding like an explosion....Who's to say that when the momentous occassion occured the universe (the makings of the big bang anyway) wasn't actually moving already? (like a firecracker that has been thrown before exploding mid air)


2003-Sep-24, 10:42 PM
Fascinating stuff.


The universe is four-(at least)-dimensionally bound together, what we call space-time.

When we look out in space, we look back in time - towards the Big Bang. The farthest observed galaxies are the closest to the Big Bang in space-time.

Hubble's Deep Field examinations imply that galaxies at 10+ billion years are in all directions.

The Big Bang "centre" therefore appears to be an outside sphere all around us. An analogy of us being on the inside of an inside-out black hole or singularity is perhaps appropriate, with the sought after "centre" being the outside "event horizon". Our problem is that it is difficult to get our heads around the consequences of the mathematics, and beyond our familiar 3D world view.


If our universe came into existence at the Big Bang, then that is when everything we can know all began: space-time, energy and matter (equivalent to energy).

The Big Bang explosion, as said elsewhere in this thread, was in explosion OF space, not IN space. And the centre is back along the time axis of space-time.

Further, the actual question of what there was before the Big Bang, is nonsensical, totally meaningless. Time itself started at the Big Bang. The question only comes up because we humans have such a strong sense that time is an eternal constant. We feel we move inexorably forward at a constant rate. It may well be infinite in the future, but the Big Bang defines its beginning in the past. And along the way, Einstein showed that it was a variable in its progression.

What there was before the Big Bang, and any God or gods as creator are subjects that are inherently unknowable, outside the natural world - supernatural if you will. They are perfect subjects for discussion under the headings of Philosophy and Religion, where enlightenment may well be sought. Here, in this forum, Ockhams razor should be wielded deftly.

How far to the other side of the Universe is still a good question. It takes us to the edge of our understanding. And starts to push us past it. That is good stuff.

2009-Mar-29, 07:10 AM
How far the opposite side of the Universe is away depends on its topology, the matter density and its rate of expansion. The simplest topology is a hypersphere and it has some interesting properties. For example if the hyper-radius is larger than the current Hubble radius then we won't know if it's a hypersphere or something else - it's too big to have seen much of its overall shape since the Big Bang, especially if there was a lot of inflation.

Let's look at a simpler case. If the Universe is closed - that is, it will one day recollapse - then the distances are a lot easier to work out. A common yard-stick is what's called the Hubble Length, which is the speed of light divided by the rate of expansion (typically that's in km/s per megaparsec.) If the Hubble constant - the present day rate of expansion - is 70 km/s per megaparsec, then the Hubble length is (300,000 km/s / 70 km/s) megaparsecs - 4285 megaparsecs in fact. Since a megaparsec is 3,261,564 lightyears, then that's almost 14 billion light-years. The density of matter in the Universe determines just how big the hypersphere is compared to the Hubble Length. If the density is twice the critical density and the Universe is only filled with matter, then the hyper-radius is exactly the Hubble Length and the opposite side of the hypersphere, the Antipodes, is just (pi) times the Hubble Length, in this case 44 billion light years away.

However we know the density is actually very close to being at the critical density. If it wasn't for Dark Energy then the hyper-radius would be 1/sqrt(Omega-o - 1) times the Hubble Length, Omega-o being the ratio of the density to the critical density. Say Omega is 1.01, then the hyper-radius is 1/sqrt(0.01) or 10 times the Hubble Length. But that's only in the very simplest case of a matter-only hyperspherical Universe.

With Dark Energy the expansion gets complicated and the topology - the Universe's hyper-shape - is harder to pin down. One possibility is that the hyper-shape is a Poincare Dodecahedral Universe, which looks much larger than it actually is. Its true size is a bit smaller than the Hubble horizon.

2009-Mar-29, 09:21 AM
HI fraiser If the big bang is true ,we could launch a craft set a course how long would it take for the other side of the universe to reach us if we stay in the same place.

I will make some assumptions; memo, Did you mean the expanding universe will catch you up ? or is your question cryptic ?

2009-Mar-29, 11:28 AM
Continuing the theme of replying to a 6 year old question...

Please lets not do the what was the origanal sentence.. It was if we launched a ship how long would it take to reach the other side,it cant ,because it is expanding away not toward but if our universe moves do we stay in one place or do we move with it.

We move with it, so we stay in one place, relative to it.

Nowhere Man
2009-Mar-29, 12:10 PM
Astromark, don't expect an answer from memo. His last post was over 5 years ago.