Anonymous
Anonymous asked in Science & MathematicsAstronomy & Space · 3 weeks ago

# Is there an end to space?

I'm saying like if you went in the same direction would you either go in a loop where you pretty much come back like Earth. Or would you actually just continue on? And realistically this isn't possible now but I really want to understand what would happen?

Update:

Basically what I'm saying is if there's an end then it loops back. If there isn't an end you keep going straight.

Relevance
• Anonymous
3 weeks ago

only if you stop eating potatoes and begin eating tomatoes

• Alexis
Lv 7
3 weeks ago

"I'm saying like if you went in the same direction would you either go in a loop where you pretty much come back like Earth."

Yes.

Tom's answer is basically correct.  The universe is a three-dimensional surface volume embedded in a four-dimensional hyperspatial manifold.  If you were to travel at an arbitrarily high velocity, you would eventually circumnavigate the universe and arrive at your starting point from the opposite direction.

The universe is estimated to be approximately 90 billion light-years in circumference, so, assuming this figure to be accurate, 45 billion light-years is the furthest two points in the universe can be from each other.  At that distance, they are for all practical matters on exact opposite sides of the universe, meaning if Points A and B are on opposite ends of the universe, no matter which direction you travel from either point, your distance to the other point decreases (cosmic inflation is being ignored here [although there is a tangential issue where the universe is often described as expanding "faster than the speed of light", a matter that is sorta interesting solely as a result of the fact that the description doesn't actually mean anything, but I'll save this for another discussion]).

The universe was once much smaller, originating at its temporal origin point with a spatial size of zero, which immediately expanded at a rapid pace during a period called Inflation, followed by a period of slowed (in terms of logarithmic growth) but still extremely rapid expansion.

It wasn't until approximately 370,000 years after Time Zero that the universe's volume reached a size where dilution of the cosmic plasma medium (basically a sea of protons and electrons, with a fair number of alpha particles [free helium nuclei, about 8% compared to 92% hydrogen nuclei {i.e.: protons}]) reduced the average temperature to the point where stable atoms could form for the first time (there was also about .01% deuterium, and trace amounts of two isotopes each of lithium and beryllium [by "trace", I'm referring to amounts on the order of 10^-40th {redshifts and the CMBR are often brought up as amongst the best evidence for the Big Bang Theory, but these amounts of lithium and beryllium resulting from primordial nucleosynthesis is actually the most compelling evidence <coming from a purely statistical standpoint> for the Big Bang Theory; a theory making predictions, only later to be borne out, on elemental abundances occurring over forty orders of magnitude, is about as close to "proof" as you get in science}]).

This resulted in the universe becoming transparent for the first time, and the universe-wide flash of brilliant light (the same phenomenon that, believe it or not, causes the bright flash of light from a bolt of lightning) is what we today refer to as the Cosmic Microwave Background Radiation (the initial visible light has been stretched by cosmic expansion into the microwave range).  It's also the fact that the universe began as an infinitesimal region (commonly referred to as being smaller than a proton [by "began", I'm referring here specifically not to T=0, but to some point T>0 but nevertheless T<not *all* that many Planck Seconds]), and remained fairly small (on the order of parsecs) in its very early life that allows us to say with confidence that the universe, despite its massive volume today, is a finite, unbounded region of three-dimensional surface volume wrapped around a hyperspatial axis.

For all intensive porpoises, infinities do not exist in the real world.  You can get infinities when you're dealing with nonquantized media like space and time, but thanks to limitations placed on the fundamental nature of observation by the finite speed of light, we can only really deal with these sorts of limitless divisions down to the range of Planck Inches and Planck Seconds, which deal with lengths and durations far larger than 10^-50th.  You'll also run into all sorts of physical *analogues* for infinity; the speed of light, for example, while an obviously finite 186,282.397 miles/second to *us*, is the universe's physical analogue for "infinite" speed.  This is why only massless particles travel at c (multiplying "infinite" speed by zero mass is the only way to get valid, positive finite values for momentum [which photons do indeed possess]), and why particles with positive, finite mass can only possess finite values for momentum by traveling at "finite" speeds.  It's also impossible for particles with positive, finite values for mass to reach absolute zero for not-identical-but-strangely-similar reasons (which aren't all that strange when you think about it, really), but, remember, we're still only dealing with the universe's physical *analogues* for "infinite* values.  Any time you come across any *actual* infinities in physics, it means something is broken, and a further refinement of physical laws is called for.

• Tom
Lv 7
3 weeks ago

Is there an end to the surface of a sphere?  if all reality were a 3D sphere's 2D surface, you could only eventually circle around and get back to where you started.  Traveling OFF the sphere into the 3D world would not be possible as it it not in "Reality".

The above imagines space as  2D reality in a 3D sphere.  In reality, SPACE is 3 D reality in a 4D HYPERSPHERE.-----So like a sphere, travel far enough on it and you end up where you started.

How do we know it is a hypersphere?   Just like in the first example---two bodies traveling on the 3 d sphere in the same direction will get closer and closer together until they meet.-------In our Hypersphere 2 bodies traveling side by side will "Attract" each other---we call it GRAVITY---but Gravity is an effect of the curvature of the hyperspherical space.

• 3 weeks ago

The fact is -- your guess is as good as anyone else's

As you indicate , the two main options are an infinite universe or a "bounded universe -- and both are equally possible ..

• 3 weeks ago

We don't know if space is finite or infinite. If infinite, you would go on forever. If it is finite, you would return to your starting point. Space could be the 3 dimensional hypersurface of a 4 dimensional hypersphere. But it is too big for us to see all the way around the universe.

• 3 weeks ago

You would be heading in the direction of the place you started but would never reach it because space expands faster than light.

• 3 weeks ago

Well there is a way to look at it at the end of the day

Everybody has to end up somewhere

Especially when you travel at the Speed of Thought

• John
Lv 7
3 weeks ago

We will never know what is beyond what we can see with our instruments. I believe it is uncomplicated. That planets cluster around stars, stars cluster into galaxies and it seems that galaxies cluster into what we call a "universe" in a modern sense. "A" universe, not "THE" universe. And in keeping with that model it is reasonable to think that there are other universes beyond, and likely more clusters. I see no reason to apply voodoo mathematics where visible space is actually quite straightforward.

• 3 weeks ago

It's thought that no matter how far "straight" you go, you'll eventually end up back where you started from... The way I've seen it described, there'd be no end to space.

• Jim
Lv 7
3 weeks ago

If space is 'curved' then yes.

If not curved then no.

If string theory is correct, then yes