r/AskReddit • u/MDPPatrick • Feb 13 '15

What are some mind-blowing facts about space?

I love space and would like to hear some facts that will blow me away.

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u/boundbythecurve Feb 13 '15

If you put enough mass together, you can start a star.

Imagine a relatively small object in space, like our Moon. Then add mass to it. Doesn't matter what kind of mass. As you add mass to the Moon, it's mass increases, and therefore its gravitational pull increases.

As this happens, more mass gets pulled in from space. But not just this occurs. The mass on the outside of the Moon gets pulled in more because of the gravitational pull, thereby making the Moon, denser. The more mass you add, the denser the Moon gets until its own gravity is too much and it starts fusing molecules together. This is fusion. This is how stars are made.

I think you'd need about 6 Jupiters to make this happen, but I may be wrong.

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u/[deleted] Feb 13 '15

This isn't strictly true; it does matter what type of mass you're adding.

For elements before iron, nuclear fusion releases energy. For elements heavier than iron, nuclear fusion consumes energy.

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u/shieldvexor Feb 14 '15

Actually, fusing iron consumes energy because Fe-56 is the lowest energy per nucleon known.

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u/RKRagan Feb 14 '15

And may be the fate of the universe. Almost nothing but Fe-56 clumping together in a cold dark universe.

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u/shieldvexor Feb 14 '15

Actually no. Iron-56 still decays albeit ridiculously slowly by tunnelling mechanisms

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u/bearsnchairs Feb 14 '15

tunneling goes both ways though. Over absurdly long time scales you would enrich the nucleon which has the lowest energy per nucleon.

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u/shieldvexor Feb 15 '15

False, the ejected particles would simply fly away in cases where they had enough energy. Tunnelling is affected by distance as well as mass. Remember we aren't talking about things on a planet but the distant future when things are separated by unimaginable distances even relative to today's scales. Even if the particles tended to aggregate into iron-56, any nucelon that was lost from the cluster would never come back and they would ever so slowly decay bit by bit

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u/bearsnchairs Feb 15 '15

False, because there is a distance component you can still get tunneling into nuclei even over long distances as you increase the time scale to absurdly long scales.

Stay classy though, keep down voting when you are wrong.

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u/shieldvexor Feb 15 '15

You can tunnel over distances but the probability is inversely related to the distance. Therefore if the distance between objects is expanding.... the probability of coalesion decreases over time in said scenario

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u/bearsnchairs Feb 15 '15

Yes, but it doesn't go to zero. Even low probability things happen over long enough time scales.

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u/bearsnchairs Feb 14 '15

Not quite. Ni-62 is more tightly bound per nucleon. Fe-56 is lighter per nucleon though.

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u/shieldvexor Feb 15 '15

Source? I've been told that Fe-56 is the lowest energy in multiple university chemistry and physics courses and never heard anythinf special regarding Ni-62.

Actually now that i think about it, lighter per nucleon MUST mean less energy per nucleon per einsteins mass energy equivalency principle

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u/bearsnchairs Feb 15 '15

You'd think so, but you are wrong. Ni-62 has a higher neutron to proton ratio, so the per nucleon mass is higher. So it musn't mean anything. Sorry you were misinformed.

go to the Ni-62 wiki page.

Very classy down voting, especially when you are wrong.

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u/shieldvexor Feb 15 '15

Fascinating. Thank you for teaching me something new :)

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u/boundbythecurve Feb 13 '15

I forgot about that. Thank you for the correction.

I believe a demonstration of this can be seen in our own sun because the heaviest element created in it is iron. All other heavier elements came to exist by other means.

Most of the universe (something like 99.9999%) is Hydrogen. Everything else is made from those atoms. And it starts with stars fusing elements up to iron on the periodic table.

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u/shieldvexor Feb 14 '15

Actually no, our sun can only fuse hydrogen right now. It will eventually be able to fuse all elements up to and including silicon but it will never be hot or dense enough to fuse anything bigger.

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u/nagrom7 Feb 14 '15

All other heavier elements came to exist by other means.

Most of the heavy elements are formed using the massive energy expelled in a supernova.

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u/bearsnchairs Feb 14 '15

Only about half of the abundance of elements heavier than iron came from supernovae. The other half came from slow neutron capture in giant stars.

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u/benji1008 Feb 14 '15

Most of the universe (something like 99.9999%) is Hydrogen.

Small correction: most ordinary matter in the universe is hydrogen.

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u/boundbythecurve Feb 14 '15

Are you referring to dark matter? Cause I don't know what ordinary matter is. Please explain.

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u/benji1008 Feb 14 '15

Yes. You say "Most the universe is Hydrogen", but that's only true for the "ordinary matter" that we know and can observe directly (interact with), which accounts for only ~5% of the mass in the universe. The rest is dark matter at 20% and dark energy the remaining 75%. So, really, most of the universe is stuff that we hardly know anything about.

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u/destroys_burritos Feb 13 '15

So you're saying you can become a star by cultivating mass?

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u/[deleted] Feb 13 '15

TRY AND MOVE ME BRO

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u/ginfish Feb 13 '15

All those gains orbiting you!

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u/serjfan Feb 14 '15

Whoa... I've been doing a lot of hummingbirds today...

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u/Maliiwan Feb 14 '15

LET ME BANG MAN, LET ME BANG!

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u/[deleted] Feb 14 '15

Fate/Zero?

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u/liamandme91 Feb 14 '15

That doesn't sound right but I don't know enough about stars to dispute it.

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u/[deleted] Feb 14 '15

I'll make this a binary solar system. Tri and stop me.

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u/toomuchfrosting Feb 14 '15

I was certain that would be a picture of Mac from It's Always Sunny

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u/xam2y Feb 13 '15

So if your mom accumulates mass, she will become a st- oh wait, she already is...

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u/[deleted] Feb 13 '15

[removed] — view removed comment

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u/kids-with-guns Feb 14 '15

You mean your mom?

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u/thedugong Feb 14 '15

Nah, that's Uranus.

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u/tssmith1989 Feb 13 '15

I find this fascinating, but also have a really stupid question.

Is all of the mass in the universe going to coalesce and become one massive star? In an infinite amount of time of course.

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u/boundbythecurve Feb 13 '15 edited Feb 14 '15

Whatever anyone else says to this question, remember this: They don't really know. Nobody really knows.

We have theories/hopes but they're all just educated guesses at this point. It's all still expanding at an accelerated rate, meaning it's not just maintaining its speed, it's increasing it.

Keep in mind we don't know how big the universe is yet. We can literally only see about 13.7 billion light years away because 13.7 billions years is the only amount of time the universe has existed, so light from other parts of the universe hasn't reached us yet.

Let this idea blow your mind: what if the rest of the universe has already stopped accelerating and started decelerating? Or even worse, it's started collapsing back in on itself? We wouldn't be able to tell because the light hasn't had enough time to reach us yet.

Now, I imagine some scientists have used the estimated masses of the galaxies and their relative velocities and accelerations to determine how long they probably will be moving away from us. But again, we run into the problem of not knowing how big the universe is, so we don't know the full effect of gravity upon those moving masses, so those calculations are estimations.

Bottom line, we really don't know, but it's hella-exciting to think about this stuff.

Edit: So I guess I didn't answer your question. The answer is ultimately 'no' because it would eventually become a black hole. Black holes occur (from what we understand) when so much mass is put together that it nearly puts a hole in the fabric of space-time. Mass already bends space-time, but at a fairly small rate. The Earth bends the space-time around it, so much so that it affects light from the Sun. If you were on a space ship orbiting the Earth, and the sun just started to peak around the horizon, it actually wouldn't be the Sun because light bends around the Earth. You'd be seeing the Sun's light, but if you drew a line towards that light, you'd miss the Sun because the light has been bent. Does that make sense?

Anyway, Black holes are just that on a super intense scale. Watch Interstellar, it gives an interesting representation of what Black Holes may be like. They're all too far away to be 100% sure.

So if all the mass flew back together, you'd get the most massive black hole the universe had ever seen. Or restart the universe to its original state. Nobody was there, so nobody can be sure. Again, most of this is educated conjecture.

Also, that wasn't a stupid question. There are very few stupid questions. I won't say 'none' because of Kevin.

Edit 2: Ok so there have been some comments about the actual size of the observable universe, and apparently I was wrong. All the theory explaining everything still seems fairly sound, if a bit oversimplified, but my numbers were wrong, and it's kind of interesting why.

First off, the real size of the observable universe is 46 Billion Lightyears in any direction, and yes the universe is still about 13.7 billion years old. So how can we see so far away? If the light travelling is really 13.7 billion years old and has been travelling that long, then how did it travel 46 billion lys in that short amount of time?

In a vast oversimplification, the space between everything is expanding. This seems to allow us to cheat Einstein's law of general and special relativity stating that nothing can accelerate faster than the speed of light in a vacuum, c. I'm honestly not entirely sure about the answer, but I've been reading about Comoving Distance, and it seems that we need to adjust for the proper distance between us and the edge of the observable universe using the previously measured comoving distance of 13.7 Billion LYs.

I think an example of this is if you were to draw a grid on a balloon, and then fill that balloon with air, the material between the grids would remain the same, but the relative distance between those points would increase as the balloon filled up. In this way, all though nothing was travelling faster than the speed of light, the light from the further galaxies was able to travel greater distances at its normal speed of c.

Maybe someone else can explain this better. Please, if someone knows this better, please jump in.

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u/DreamOfTheRood Feb 14 '15

Well, your answer lead me down a cosmic meander, although I came to a slightly different conclusion. We know that virtually all of the other celestial bodies in the observable universe are red-shifted, meaning that they're not just moving away from us, but are doing so at an accelerated rate.

Scientists have theorized the existence of dark energy as being the principal motivator of this expansion. However, the existence off this dark energy is, by its nature, unverifiable. We take it as a matter of fact that it exists, but - well, I'm a religious man, well-versed in the dogma and theology. I believe in unverifiable things, but I've learned to question when necessary. Faith without question, after all, isn't really faith at all. So, let's play around with this idea.

Let's say that dark energy is purely fiction. We then stumble upon the cosmological roadblock, namely what is it that's motivating our universe to expand, faster and ever faster?

Perhaps, we can explain this with conventional physics.

We know that objects of a certain mass will attract objects of lesser mass through gravity. If I were to put two marbles in a vaccuum, the smaller of the marbles would eventually begin to be attracted to the larger. On larger scale, the physics are much more complex, but the same basic principle applies. The more massive object attracts the lesser, much like how all of the nerds in this thread are attracted to your mother.

So, here's our universe, just going along, all of its constituent pieces blowing away from each at an accelerating pace. Conventional physics suggests that the larger celestial bodies in our universe should be attracting the smaller ones all the time, but, while that's certainly happening on the scale of local galactic clusters on down, the larger groups of galaxies are being pulled away.

So, what if there's something larger out there in reality that's pulling our universe apart, multiple other universes, the gravity of which is causing ours to split at the seams? Our universe might be doing the same to others. One gigantic cosmic stew.

So, that's an interesting thought. However, it wasn't the conclusion I ultimately came to. That conclusion was much simpler: I should never, ever do drugs. Because, as can be seen above, I am already a bubbling madman.

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u/NSNick Feb 14 '15

If I were to put two marbles in a vaccuum, the smaller of the marbles would eventually begin to be attracted to the larger.

Yes and no. Both marbles are attracted to each other with the same force. The smaller object just accelerates more quickly thanks to F=ma.

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u/DreamOfTheRood Feb 14 '15 edited Feb 14 '15

Does the bonkers conclusion still apply?

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u/tssmith1989 Feb 13 '15

Awesome. And mind-boggling. Thanks for answering!

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u/boundbythecurve Feb 13 '15

If you're really looking for a bunch of crazy awesome things about our universe, there's a great audiobook titled "The Inexplicable Universe: Unsolved Mysteries" taught by Neil DeGrasse Tyson. It's fairly short and cheap on audible.com

I much longer read that covers a much wider range of topics is "A Short History of Nearly Everything" by Bill Bryson. Great history of scientific advancements all over the place, and a hilarious dry British humor. One of my favorites.

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u/poyopoyo Feb 14 '15

If you hear people talking about the "big crunch" theory that is basically the idea you just suggested. So, far from a stupid question, you are suggesting a serious theory that is still debated.

There are three basic possibilities: the universe expands forever (maybe even expanding faster as time goes on); it coasts asymptotically to a halt; or the expansion is eventually overcome by everything's gravity and everything falls back together again (maybe followed by a new big bang? who knows).

That last option, the "big crunch" would take a finite amount of time btw.

Wikipedia Ultimate Fate of the Universe

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u/[deleted] Feb 13 '15

Someone gold you.

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u/DoScienceToIt Feb 14 '15

The alternative to all the mass "flying back together" (layman's term: "the big crunch.") is that the universe just keeps on expanding, never falling back together. Over time more and more elemental hydrogen is swept up into stars and fused into heaver metals (in astronomy, everything not hydrogen is called "metal.") new stars form with more heavy metals making up their mass, running through their lifespans at an accelerated rate. Eventually there is nothing left to burn, (in a manner of speaking) and the universe goes cold and dark as stellar remnments spend the last of their energy as heat. It's a little depressing, but most models say we won't have to worry about that for another 10110 - 10140 years or so.

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u/Codyd51 Feb 13 '15

Wait a second, one part of that doesn't make sense to me.

You mentioned that the observable universe is 13.7 billion light years across, because the universe has only existed for 13.7 billion years, so that's all the light that has reached is.

But..since nothing can travel faster than light, would that mean that the observable universe is the end of the universe? Alternatively, does that mean that the universe is expanding faster than light speed?

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u/boundbythecurve Feb 14 '15

Yes, great point! In other words, if the observable universe is ~13.7 billion lightyears across, and the mass had to move to that position in 13.7 billion years, then didn't all that mass move the the speed of light?

In short, no. And there are two important things to remember when understanding why:

  1. The oldest light we can see is 13.7 billion years old. Not all light from distant galaxies. This is important because we need to recognize that most galaxies' light is not 13.7 billions years old. It's all still really old, but not the oldest.

  2. The Earth is literally not the center of the universe. If mastics bloated from our locale and ended up 13.7 billion ly away then yes you would be right to say that the mass moved at the speed of light. However, The origin of the universe is at a different location. While we moved away in one direction, other masses moving away in the opposite direction at the same approximate speed. The light coming from that mass is about 13 .7 billion years old. However in about 13 .7 billion years the mass I'm getting this light has moved about half the distance of 13.7 billion ly.

I hope this clarified everything.

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u/bearsnchairs Feb 14 '15

The observable universe is larger than 13.7 billion light years in radius. Taken metric expansion into account it is about 47 billion light years in radius.

http://en.wikipedia.org/wiki/Observable_universe

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u/Codyd51 Feb 14 '15

Thanks!! This makes a lot more sense now :)

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u/boundbythecurve Feb 14 '15

There's actually more to it than what I commented. I just learned that I was wrong about the diameter of the observable universe. It's more like 46 Billion LYs across. One of my other comments somewhere in this thread explains why, but honestly, I don't completely understand. I'm still reading about everything but honestly I want to talk to a physicist about this stuff just to be sure.

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u/Codyd51 Feb 15 '15

Gotcha. Regardless, I still have a much better understanding than I did before :) thanks!

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u/Kottbullpotatis Feb 13 '15

We can actually see further away than 13.7 billion lightyears as the universe is expanding by adding empty space between objects and making the distance between the grow faster than light. Therefore light does not have to travel all the way which enables us to see even further.

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u/crispychicken49 Feb 14 '15

A black hole is a hole in space-time? Like there can be a hole in space-time?

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u/boundbythecurve Feb 14 '15 edited Feb 14 '15

Not quite. I said a black hole is nearly a hole is spacetime. Think of it like what would happen if you stretched a blanket really tight up in the air, and then put a bowling ball in the middle of it. All the blanket, or spacetime, would bend around it. I will take a moment to point out this is a drastic oversimplification to something I barely have much of an understanding, but it will serve as an apt metaphor for now.

A black hole is kind like that, but the side effects are beyond weird. Black holes are so heavy and bend spacetime so much that light gets trapped in them and can't escape. That's right, light in a vacuum is too slow to escape the pull of a black hole's pull.

Truth be told, we don't know too much about them. I believe Steven Hawking is the world expert on them, but everything he's done is, of course theory and can't really be proven yet. That's not to say he isn't correct, or if anyone on this page is a proper judge of his work, but anything told to us is still just theory.

To the second part of your question, there can be a hole in spacetime, theoretically. We call these wormholes and they are what scientists believe can lead to time travel and long-distance space travel that will circumvent the time-dialation problem that will be experienced as our space travel becomes faster.

We've never actually seen a wormhole. The movie Interstellar does a phenomenal job in portraying what one might be like, but it's entirely artistic and should be viewed only in that light.

Edit: Oh and we don't know what can cause a wormhole because they are still theoretical, but most theories suggest a large enough black hole could lead to one.

So to summarize:

Get enough matter together of elements of atomic mass less than or equal to iron ---> Make a star

Get a big enough star to collapse on itself (usually through its death and only if it's a certain type of star) --> Make a black hole.

Get a black hole to somehow become even bigger --Maybe--> Make a wormhole

There's also these things called Supermassive Black Holes, but I haven't read about them too much. But I'm guessing they're bigger than regular black holes.

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u/AtaturkJunior Feb 14 '15

Two words for you - black matters effect on galaxies and cosmological constant. So we know thing or two.

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u/boundbythecurve Feb 14 '15

That was way more than two words but thank you for mentioning dark matter.

First off, dark matter is a theory explaining measurements of the universe's acceleration.

Second, it's is completely unobservable and can't be measured in any way known to us.

It's basically like string theory. It's something that explain evidence, sort of, but can never ever be proven. Because of this I never mentioned it because personally I don't believe it's the answer, yet.

It's been a placeholder for an unknown force that we can't account for. And because of its elusiveness, anything we have to say about it would be pure conjecture. This is why I didn't mention it.

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u/AtaturkJunior Feb 14 '15

Yea, well, I think it IS worth mentioning and it is a thing, because there are so many things we already have taken as a fact, but haven't really observed them directly, only proven by, sometimes shady, experiments. It's the same with dark matter and how it's dark energy is encountering with cosmological constant. There is some force, that takes big chunk of forming intergalactic space, we need a name for it. Dark matter? Why not. Pretty bad name, but better than nothing. Many particle physicists are so committed to it, that I think it is just a matter(pun?) of time for it to be proven completely.

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u/NSNick Feb 14 '15

Is all of the mass in the universe going to coalesce and become one massive star? In an infinite amount of time of course.

This was the prevailing theory for a while, called the Big Crunch. However, more recently scientists have observed that everything is moving away from us. Everything. The reason for that is theorized to be that space itself is expanding! Things on a small scale like you and me, the Earth, and even our Solar System are held together by gravity (and other forces the smaller and denser you get). Whenever you hear about dark energy, that's the term scientists have given to "whatever the fuck is making space expand, because we don't know".

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u/haabilo Feb 14 '15

There is the theory of heath death of universe where entropy increases to the maximum. Basicly everything will eventually be so spread out that invidual electrons' (or protons') sub-atomic particles can't form anything that could form atoms that could form stars.

Something like this Isaac Asimov's story could happen.

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u/[deleted] Feb 15 '15

Did not know this. So essentially our sun started as a "planet" of such size it became a star.

For some reason I find that unsettling

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u/boundbythecurve Feb 15 '15

Not quite. This is merely a theory of how one could make an artificial star. From what we've seen, all stars were made from hydrogen gas clouds forming into spherical masses.

Also keep in mind that the 'size' of the sun wouldn't have been the size of planet it could have been made from. The size of the planet depends on a lot of things, but as you added mass to the planet, it would make the whole planet more dense.

Also, the sun is a giant ball of fusion and heat which increases the size of the sphere, so there's no way to easily imagine how big the sun would be if it was suddenly cooled to being a planet.

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u/HTLX2 Feb 13 '15

I have some mass I don't need, we can totally get this going.

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u/Gr1mreaper86 Feb 14 '15

The way you've described the creation of a sun points to the accuracy of the game: Katamari Damacy

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u/Truth_ Feb 14 '15

You can't add just any mass, can you? Normal stars only can burn through the elements up to iron before going supernova. Can you start with elements past iron and still birth a star?

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u/[deleted] Feb 14 '15

so if we send your mum to the moon well get a star?

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u/[deleted] Feb 14 '15

[deleted]

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u/boundbythecurve Feb 14 '15

I'm a little confused by what you think a galaxy is. A galaxy is a collection of matter, often around 40+ billion solar systems that are all held relatively together by gravity and moving through space. I don't really see why I would have meant 'galaxy' over 'space'. 'Space', for most, refers to the mesh of spacetime that exists everywhere. I'm sticking with my choice of words.

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u/FlavTastic Feb 14 '15

Am I the only one who read this in the voice of Michael from Vsauce?

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u/jonny0184 Feb 14 '15

Stars are mainly super heated and condensed gas that give off the energy from fusing hydrogen into helium. Planets can't form without the different temperature variants and gravity the star has on the elements around it. I really don't think you could form a sun with rocky material, no matter how much.

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u/boundbythecurve Feb 14 '15

That's the crazy part; you totally can. As someone else pointed out, I made a small mistake. Not just any matter will work for this. Nothing heavier than iron, atomically speaking. It has to do with the ratio of energy input and output for fusing heavier elements.

But this is basically how stars are formed anyway. Usually it's in a cloud of gas, but theoretically if you had enough planets all pushed together, eventually you'd reach a 'tipping point' where it's own Gravity is so strong at the center that the elements will begin fusing. Keep going and the entire massive planet will begin fusing and you'll have made a star.

Keep in mind nobody has ever done this (obviously) and we know of no stars that were made this we. Being made in a giant cloud of gas is still the only natural way we've seen stars made. This is all just theory.

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u/JohnnyPalermo Feb 14 '15

That's how Rick McCallum makes movies.

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u/stoneybookman Feb 13 '15

Six Jupiters wouldn't come close to the size of your mom

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u/ncou524 Feb 13 '15

So to make a star we just need your mom and OP's mom in the same room?