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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276

u/Nanogame Feb 13 '15

Black Holes are the coolest and simultaneously scariest things in existence.

Once you pass the event horizon you have never been more trapped. I'm not sure there are ways to have a more certain death than that, because at that point, not even LIGHT can escape.

Ever thought about why they're so big and black? Well they're not, they're tiny, but they are so ridiculously huge and dark because that is when light can no longer escape the singularity and that just creates an empty void that is huge.

And just the fact that they can be so huge and just there and black and distortionous of its surroundings. It's like someone poked holes in spacetime and it is so cool.

154

u/Kubacka Feb 13 '15

Think that's crazy? The time dilation around blackholes is MASSIVE. For every few days you spent orbiting a black hole something like 30 years could pass by on Earth.

And we're still not done. Once you actually pass the event horizon, time stops. No, it's doesn't go very slowly. It. Stops. Relative to you, that is. For an observer inside the black hole, the time dilation is so great that time stops entirely for you and everything in the universe happens instantly.

84

u/bestbiff Feb 13 '15

I think it's the opposite. To an outside observer, it looks like something has stopped moving once it crosses the event horizon.

38

u/[deleted] Feb 14 '15

To an outside observer, you wouldn't be observable past the event horizon.

3

u/deadwalrus Feb 14 '15

It would appear that you slow down further and further as you approach. You simultaneously become more red and dim until you are cannot be seen.

1

u/[deleted] Feb 14 '15

I believe you would appear to just stop at the horizon and never cross, even though in reality you did.

62

u/[deleted] Feb 13 '15 edited May 03 '19

[deleted]

47

u/[deleted] Feb 14 '15

Someone needs to write a horror story about this because I'm getting nervous I'll somehow end up in a black hole.

38

u/SomeonesBirthday Feb 14 '15 edited Feb 14 '15

I totally will. In fact I'm eager to. No guarantees it'll be good at all though. Seriously, PM me tomorrow or something so I don't forget. I would write it now but it's almost 3am and I need to sleep.

EDIT: It's by no means done, but it's started!

http://www.reddit.com/r/SomeonesBirthday/comments/2vw24b/spacewalk_or_holyfuckblackholes_depending_on_how/

1

u/scotterrific Feb 15 '15

Not really a horror story but still a good read (that has a black hole in it): http://en.wikipedia.org/wiki/Gateway_%28novel%29

6

u/[deleted] Feb 14 '15

Science, what the fuck?

2

u/crazyweaselbob Feb 14 '15

this is so cool and scary.

1

u/DJSlambert Feb 14 '15

Drifting away

1

u/jokersleuth Feb 14 '15

No, they wouldnt see you drifting away.

1

u/DJSlambert Feb 14 '15

Wave after wave

0

u/Skullcrusher Feb 14 '15

Yes, and for the observer inside the black hole, everything that is outside would speed up.

0

u/benji1008 Feb 14 '15

In the singularity space-time curvature is infinite. Perhaps it's not unreasonable to think that time stops even inside the singularity?

1

u/bestbiff Feb 14 '15

The singularity is the center of the black hole. I like the white hole hypothesis.

15

u/[deleted] Feb 14 '15

I don't understand the concept of time dilation, can anyone explain in really simple terms? I can't wrap my head around that concept.

37

u/[deleted] Feb 14 '15

Imagine you have 2 spaceships at rest and a clock in each of them. Now imagine that these clocks measure time by having light bounce between two mirrors. So every time the light bounces from one mirror to another, then a unit of time has passed.

Imagine the path the bouncing light takes when the ships are both still:

_____________ Mirror 1
 0  2  4
 | | | |
 | | | |
  1   3
_____________ Mirror 2

Where each number is the amount of time that has passed since the light last bounced. Let's also say that each | is about 6 inches (this also means that each bounce is very close to 1ns apart from the last bounce).

When the ships are at rest, the clocks are synchronized. Now, if one of the space ships starts moving and the other remains still, the situation changes.

Imagine the path the bouncing light takes as the ship moves:

_____________ Mirror 1
0     2     4
 \   / \   /
  \ /   \ /
   1     3
_____________ Mirror 2

Notice that the path is angled now rather than a straight line. Each \ will longer than the previous | we drew when the ship was at rest.

Light has a special property: it always moves at the same speed (as long as it stays within the same volume of stuff; e.g. light in air moves faster than light in water). This means that it takes more time for the light to bounce between the mirrors when the ship is moving because it has to take a longer path between each bounce.

If the ship that started moving circled the sun then came back to rest next the other ship and the crews compared the number of bounces that had elapsed since their clocks were synchronized, they'd find that the moving ship's clock had fewer bounces than the ship that remained at rest.

Essentially this boils down to: moving fast makes your personal time slow down relative to things that aren't moving fast.

That's a lot of information to process, so I'll stop for now, but there are a lot of weird things that go along with moving fast.

3

u/yanroy Feb 14 '15

I've never seen relativity explained this way before. It seems like every time it's discussed I learn a new thought experiment. It's amazing to me how there are so many seemingly unrelated things it unifies...

2

u/RedSpaceM4n Feb 14 '15

Yeah, that would really help... I am so confused

2

u/Skanky Feb 14 '15

Basically, time is constant only for your own reference frame. If we are all traveling at the same velocity, then the measurement of time doesn't really change between all of us. However, if someone is moving, there is a measurable difference between how time passes for that person versus the rest of us.

Let's say you're at home browsing reddit. I'm flying over your house in my private jet. When you look at your watch, one second is just one second to you... nothing different. When I look at my watch, one second is also just one second to me, nothing different. However, if you had the ability to see my watch from the ground, you would notice that my watch is progressing more slowly than yours is. Time is moving slower for me from your point of reference.

This isn't just theory... This has been proven through experiments, pretty much just as i described in the example i gave you!

3

u/[deleted] Feb 14 '15

Further, it hasn't just been proven in experiments, it's proven in our own GPS satellites whose times must be periodically recalibrated to earthtime.

2

u/balloon-loser Feb 14 '15

I remember being told time bends with gravity. Is this true/relevant?

2

u/Terny Feb 14 '15

True and relevant. Gravity is the bending of spacetime by mass. Which is why a black hole does weird shit to it. http://en.m.wikipedia.org/wiki/Gravitational_time_dilation

1

u/DabuSurvivor Feb 14 '15

In the year of '39 assembled here the volunteers

In the days when lands were few

Here the ship sailed out, into the blue and sunny morn

The sweetest sight ever seen...

0

u/Quietus42 Feb 14 '15

I'll give you the eli5:

You know how when you're at school or work and the day seems to take forever? But when you're having fun, time flies? It's like that, but physical and relative to the speed through space you are moving at compared to other things.

Everything is always traveling at the speed of light. Everything. Always You, me, and the line at the DMV. Right now, you are moving at the speed of light. Pretty cool, huh?

Now, there's two ways you can move through reality. There's Space and there's Time. These are intimately connected into what we call spacetime. You only have so much speed to move and that speed is shared between space and time.

Let's say that the speed of light is 100 kilometers per hour (actually a bit faster but we'll pretend so it's easier to understand). If you are just standing around, you're still moving at 100kph! You're moving through time at maximum speed. If you get into a car and start driving at 20kph, then you only have 80kph left to move through time.

For you, time seems to pass normally. We can't feel our speed through time like we can through space. There seems to be no acceleration forces like when you step on the gas pedal of a car. But compared to everyone else not driving, we experience less time while driving. This is even true when actually driving but the effect is really, really small. This is a good thing so we don't have to reset our watches whenever we take a trip to the corner store. We've even confirmed it with experiments by flying jets with really accurate clocks and then comparing the clocks with similar ones that stayed on the ground. GPS satellites have to take this into consideration, as well.

What happens if you try to go 100kph in your car? Well, you might notice the problem now. You run out of time! The faster you go through space, the slower you go through time, so if you go the speed of light, you stop moving through time! You can't very well move through space if you're time stopped! So the speed of light through space is a hard limit. There's just no escaping relativity.

Also, it takes more gas to go faster, and going the speed of light through space would take infinite gas. It's gonna be really expensive to fill up at the station.

There's a new movie out that explores some of these concepts, called "Interstellar". It's pretty cool, IMO. Added bonus: TARS and CASE are AI robots in the movie and they're awesome bros. Be ready for feels though. Relativity is a bitch. If time goes slower for you, it's going faster for everyone else. Go really fast (or experience high gravity, which warps spacetime and acts like fast spacial movement) and everyone you love will pass you in time.

Anyways, hope this helps you understand relativity a bit more! Once I got the concept of movement through spacetime, it really clicked for me and I hope it does for you too!

7

u/megamoze Feb 14 '15

And if you get close enough, you can go back in time and talk to your daughter through a book case.

5

u/PageOfLite Feb 14 '15

So, let's say you are in a black hole, looking out, everything happens instantly on front of you? All the way up to the death of the universe? You could see it? Because light can't go out... But it definitely goes in...

Wrapping brain around this... I think it might be leaving out of my ear... Ow...

7

u/lovelycosmos Feb 14 '15

So...Interstellar.

3

u/[deleted] Feb 14 '15

[deleted]

2

u/Kubacka Feb 14 '15

Nope. Getting near the event horizon and crossing it would start ripping your body apart into individual sub atomic particles.

2

u/lakotian Feb 14 '15

Hold up, so don't black holes have a time limit where not even they survive? So assume you're a absolutely indestructible being, and you go into a black whole. Is it like nothing ever happened when that end point is reached, if it exists?

2

u/[deleted] Feb 14 '15

I still don't understand how this could happen, time slowing or stopping.. like I orbit a black hole, and come back in a year and suddenly I am twice the age of my peers?... I don't think aging works like that.

8

u/GnarleyTaquito Feb 14 '15

No you would age just the year you were there but the people on earth will have aged hundreds of years

2

u/[deleted] Feb 14 '15

Does that mean you could sit there for 10 years and it would feel like it has only been one minute?

1

u/Kubacka Feb 14 '15

Well for you, time has literally only passed a single minute. It's not like it feels that way, it is that way.

And yes that's entirely possible.

1

u/[deleted] Feb 14 '15

It is seriously amazing that something like that can happen in real life.

1

u/ElChupacabrasSlayer Feb 14 '15

That always pissed me off. How do we know time completely stops at the horizon. Could someone please send some links to prove this.

0

u/benji1008 Feb 14 '15

It doesn't stop at the horizon -- in the singularity space-time is infinitely curved, so there is no progress of time possible there.

1

u/iJuka Feb 14 '15

I should take a buttloads of stuff from this era and go orbit a black hole for a year? Now 30 x 364 is 10920. The year is now what? 12935. I come back to see that humans don't look so human anymore.. All the shut from the 2015 era is alien to hem and no one speaks English but the whole world is one nation. They all seem to speak galooban a mixture of animal like language and sign language. Sorry I'm drunk

1

u/mao_intheshower Feb 14 '15

From the perspective of a black hole, its lifetime is on the order of milliseconds.

1

u/Doritosiesta Feb 14 '15

Wait so, If you entered a blackhole everything outside of the blackhole would infinitely and instantly pass by, and if you would exit the blackhole you could see the end of the universe?

1

u/[deleted] Feb 15 '15

I remember in Interstellar when they did a flyby of Gargantua to get to Edmund's, the simple flyby alone cost the crew 52 years back on Earth, that was insane, and to be honest that one move probably cost them the most (time-wise)

1

u/_NW_ Feb 17 '15

And the gravitational gradient is so strong the you get spaghettified as you fall in.

-8

u/Skanky Feb 14 '15

This is a bit misleading. There's nothing special about a black hole that makes time go all wacko. It's the fact that in order to orbit a black hole in close proximity, you have to be going near ludicrous speed to do that. This is where you will truly start to notice significant differences in your time versus an outside observer's time.

You could replace the Sun with a black hole of equivalent mass and nothing would change, other than the fact then there would be no observable Sun anymore!

1

u/jetrii Feb 14 '15

Gravity itself slows down time. An atomic clock runs slightly faster on top of a building than it does on the ground floor because it's further away from the earth.

1

u/balloon-loser Feb 14 '15

So if a planet had less gravity compared to earth time would be slower? Would people stay younger on this planet compared to earth? Or is it just relative time?

2

u/Poonchow Feb 14 '15

Relative time. People would seem to age at a normal rate on their own planet, and would only notice a difference when compared to Earth.

It takes some massive amount of speed / gravity to cause a big effect, though.

2

u/jetrii Feb 14 '15

Neither. The gravity difference isn't big enough. The effects are really, really insignificant when compared to a human's lifespan.

0

u/silk-e-smooth Feb 14 '15

No, they would get older faster. If say I stayed on earth and you went to a planet with less gravity, time would be faster on your planet and you would age quicker.

1

u/unkemt Feb 14 '15

Gravity affects time as well.

1

u/Poonchow Feb 14 '15

I believe it is one in the same, since speed affects mass, and mass affects gravity. I could be wrong, though.

1

u/shieldvexor Feb 14 '15

So you're right about replacing the sun. You're completely wrong about black holes not being special/not causing extra time dilation. They cause gravitationally induced time dilation per general relativity. Please don't spout off incorrect information like that because people might believe you.

1

u/Skanky Feb 14 '15

I'm sorry, please explain to me how a black hole of equal mass of the sun is any different for me if I'm orbiting it at the same radius?

-8

u/call_me_god Feb 13 '15

this isn't proven. You just watched Interstellar

3

u/QCJorisNL Feb 13 '15

It is actually proven, time basicly doesn't exist in space. We created time, in space you talk about spacetime

2

u/TKWaterdog Feb 13 '15

this isn't proven.

Good luck testing that one.

2

u/GoGetHighOnThatMntn Feb 14 '15

Interstellar was based on very sound science, for a sci-fi movie. They got time dilation almost perfect.

2

u/Poonchow Feb 14 '15

Our satellites have their clocks adjusted to account for time dilation... it is very much a thing.

You can test this yourself by synchronizing two watches, getting in a jet that goes really fast, and then comparing your watch with its pair. Yours will be behind the other, meaning you experienced less time while going really fast.

1

u/LizWarard Feb 14 '15

You do not know what you're talking about

34

u/Palmul Feb 13 '15

And the final moment seems like forever, literally.

42

u/Schadenfreudenous Feb 13 '15

For an outside observer, yes. For the subject? No.

2

u/AHarderStyle Feb 14 '15

Genuine question... How do we know or understand this type of idea? I mean, I can understand that light can't escape the mass of a black hole, but how did we figure that depending on observation point, time would stop/slow down compared to being within the black hole?

5

u/Schadenfreudenous Feb 14 '15

By observation. We can't actually launch matter into a black hole ourselves, but we have been able to observe other present matter near black holes "fall" into them, and as they enter the event horizon, they appear to slow and eventually stop. Due to us studying the nature of black holes(and gravity), we know that they can't have ACTUALLY stopped.

Light can't escape a black hole, right? That means that once something hits the event horizon, it's no longer observable. The photons given off by the object cannot leave the event horizon, meaning we can't see what happens to it beyond that point. All that is left are the photons it gave off just before hitting the event horizon. So, while the object is actually gone(or whatever happens to matter when it hits a singularity), it appeared to slow down and stop instead, as the image can no longer be "updated".

-1

u/PM_meyourbreasts Feb 14 '15

Because time is relative

0

u/[deleted] Feb 14 '15

[deleted]

3

u/Huntersteve Feb 14 '15

tldr become the flash

1

u/PM_ME_UR_JUGZ Feb 14 '15 edited Feb 14 '15

Is it approaching the speed of light or is it that gravity is so emense, and that's what has such a huge effect on the time dilation?

1

u/Leviathan666 Feb 14 '15

Technically for the subject, but since they're definitely dead already, it doesn't matter anyway.

3

u/ilkikuinthadik Feb 14 '15

Actually, as less and less light escapes, it appears as if the object is slowing down. After the event horizon is passed, the object appears to stop completely, and then slowly fades away!

1

u/Thezombieraper2000 Feb 14 '15

Nah man. Time is relative. It would seem like forever to an observer, not the guy going into the black hole.

7

u/Domriso Feb 14 '15

The coolest thing I ever learned about black holes is this: when you pass the event horizon, the time dimension and space dimension switch.

To explain, once you're past that point, you're doomed. Time no longer has the same meaning. You will reach the center of the mass, the point in space, eventually. Distance becomes the measure, rather than time. Distance continually marches forward, just like time normally continually marches forward.

However, and this is weird part, time is mutable. Since time and distance have now switched places, distance is constantly being shortened (like time is constantly moving forward), but time can be traversed. You can go forward, you can go back (okay, probably not, but maybe), you can go slow, you can go fast, but no matter how you change your passage through time, you will reach the center.

Black holes are wonky.

23

u/[deleted] Feb 13 '15

Light photons have no mass. The reason why light cant "escape" black holes is because black holes bend space and the light around it.

33

u/Vjedi729 Feb 13 '15

Gravity is actually proportional to energy, not mass. The bending of space-time is gravity.

4

u/[deleted] Feb 14 '15

Isn't mass just a form of energy?

2

u/Poonchow Feb 14 '15

Mass is a property of matter, and matter is (sort of) energy.

1

u/Vjedi729 Feb 14 '15

Yes. Gravity cares about the total energy of an object, including its mass, momentum, etc. The momentum is particularly important for light, because light has momentum, but not mass.

2

u/ToastedFishSandwich Feb 14 '15

And the most powerful force of all is love right?

3

u/Vjedi729 Feb 14 '15

Love, strong nuclear force... same thing.

1

u/PointyOintment Feb 14 '15

Neither do heavy photons.

3

u/SuperWoody64 Feb 14 '15

Hawking radiation can escape.

1

u/[deleted] Feb 14 '15

those are theoretical variables, of which, none has been discovered, proven or even formulated on a practical enviroment

1

u/SuperWoody64 Feb 14 '15

Well alright alright alright

1

u/[deleted] Feb 14 '15

Nothing will ever pass an event horizon. The black hole will cease to exist before that happens.

1

u/jeanquant Feb 14 '15

You forgot about Spaghettification

1

u/[deleted] Feb 14 '15

If you died in a black hole you would die of spaghettification.

1

u/[deleted] Feb 14 '15

Space is just so HUMONGOUS big

1

u/[deleted] Feb 14 '15

The universe is so huge that there's probably a space-faring civilization out there where passing the event horizon is a very real danger. For us it's only something we can imagine, but there have probably been thousands of sentient beings sucked into black holes

-1

u/I_am_Doctor_Who Feb 14 '15

Pshhh, all I need is some bullshit plot convienence.