Cosmic background radiation | Scale of the universe | Cosmology & Astronomy | Khan Academy
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- Опубликовано: 12 сен 2024
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Cosmic Background Radiation. Created by Sal Khan.
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Cosmology & Astronomy on Khan Academy: The Earth is huge, but it is tiny compared to the Sun (which is super huge). But the Sun is tiny compared to the solar system which is tiny compared to the distance to the next star. Oh, did we mention that there are over 100 billion stars in our galaxy (which is about 100,000 light years in diameter) which is one of hundreds of billions of galaxies in just the observable universe (which might be infinite for all we know). Don't feel small. We find it liberating. Your everyday human stresses are nothing compared to this enormity that we are a part of. Enjoy the fact that we get to be part of this vastness!
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@Melthornal The universe was relatively uniform then; gravity would have been pulling in all directions.
Finally! An explanation I could understand!!!! THANKS!!!
Just wonderful, I been tryin to find out about "what was earth like 1 billion years ago?" for a while now, and I think this has helped. Have you ever come across - Bannrial Bizarre Bulldozer - (do a google search ) ? It is an awesome exclusive product for discovering your spiritual animal and the clues it has to your future success minus the normal expense. Ive heard some extraordinary things about it and my friend got cool success with it.
Oh man! "Obviously I'm not drawing things to scale", I hope not, you're drawing the entire universe! Haha, cracked me up, I'm gonna watch the rest now.
Thank you so much for taking the efforts and time to explain this with good diagrams. I do have some understanding of it now. Well done.
The CMBR was one of the biggest discoveries in the history of science. Without its discovery, the Big Bang theory would still be considered a hypothesis.
MrMorphicus No marks awarded.
it is still a hypothesis that is difficult to sustain. search for electrical universe, Harild ARp, etc will be surprise!
MrMorphicus you are right
Sir thank u very much for explaining in such a simple way.
you’re an amazing teacher, thank you so much
This is a great video! Good job, as always Khan :)
Can you make a video on the horizon problem? I liked your explaining and illustrations
@khanacademy So is it still relatively uniform? How would it change from uniform to nonuniform? Or did this all happen before the epic matter v. antimatter duel, which could have destroyed the uniformity?
If the universe was so dense, why wouldn't a black hole type structure form and prohibit the matter from expanding with space?
Since the scientists also refer to black holes as singularities, Mr. Khan, so are these collapsed stars mini-universes regarding the mathematics, pray tell?
I love the way Sal explains this. I find the idea of space itself expanding unconvincing. I am happy with the idea that the distance between objects can get bigger. Like if you put a balloon full of air in the microwave all the molecules on average would get further apart and they would all start moving faster. I like the idea that light waves are slowed down by gravity (refracted). (Don't worry I am not contradicting Einstein. Since all physical processes are slowed down by gravity to the same extent, locally light would be measured at the same speed that it is always measured at. )The lower the frequency of light the more diffusely it should be spread about. I would be interested to know what a map of lightwaves of even lower frequencies looks like. I would love the present-day theories to be replaced by something a bit less far-fetched. As always in the end, reality will settle the debate whatever reality turns out to be.
How did energy become matter? If everything was expanding outward equally, how did (presumably) photons bump into eachother with enough force to create particles with mass? Shouldn't everything (energy?) have been moving outward at the same rate of speed?
Considering that Einstein's equations describe a dynamic universe i.e. one with a beginning, expanding, and predicts the existence of black holes, I strongly believe that an entire universe lies inside of a black hole. And perhaps our own universe lies within a black hole from a parent universe.
This is because as time goes on, net entropy for the universe increases, so at the beginning of the universe, everything was uniform, right?
The big bang, a weird and wonderful thing to ponder. What if time is energy or a 'force' that can move energy. Could the black holes compress matter so much that it goes back in time to the singularity, and therefore be a perpetual universe? Maybe that's what all this dark matter business is. Like some kind of transition force that moves energy back to the begining. I keep asking myself how did the big bang start? Plenty of explanations as to what happened after bb, but where did it come from?
@khanacademy Or perhaps, if gravity bends space time to make "wells," at this point there wasn't enough space to bend in order to create strong gravitational forces?
There's an interesting article in Sciencenews about the cosmic background radiation. Roger Penrose and Vahe Gurzadyan claim they found circular patterns where the average temperature of the radiation is lower.
They claim that this cannot be explained by our current model of the big bang theory, but they propose these circles are like footprints from previous bigbangs that left a mark on our current universe, which would be a pretty cool discovery if it were true. :)
@Melthornal Besides, the laws of physics break down in the singularity.
Sir, I am an accountant but your lecture gave me a good insight of CMBR. But I do not understand a thing ; big bang has happened just at a point of our existing universe and all those radiation should come from that certain point. Then, why CMBR is coming from every direction to our earth ? Would highly appreciate if you kindly spare me.
The microwaves that reach us are light waves whose frequency has changed over time.
When "singularity" is the only thing that exists in the universe, there is no "outside gravity" pulling in any direction and therefore the original question still stands: Why wouldn't the first black hole prohibit the matter from expanding with space?
knowing that we're not the center of the universe, how can we uniformly observe the microwave background of the universe at the same instant and in all direction?
1-MinuteCosmology It’s the same logic as light, which is also a wave. Not all of it has reached the Earth yet because it takes time to travel.
We certainly are the center of our “observable” universe. So is every other point in the universe the center of its “observable” universe. That is why we perceive a uniform distribution of CMBR.
very informative. thanks!
Thanks for this, I learn alot from you.
ratio
i always wonder, does space stretch on forever. if not, something has to be outide of it, but if it is, can something just stretch endlessely
If we could observe the quantity of time as similar as quantity of space, I believe we would see Universe from the Big Bang to Contraction as a super large Spark.
amazing,thanks a lot!!!!❤❤❤
''Cosmic microwave'' :O
''Background radiation'' :D
same thought here
2 people had their minds blown.
There currently could be a earth like planet with intelligent life 25 billion light years from us. They would detect the CMB from all directions 13.7 billion years in the past also.
How big was the source of the CMB 13.7 billion years in the past?
if i were to take a picture of the sun while i was on it (i know its not possible, and i send it to earth, doesn't it travel instantely, so isnt it technically faster then light?
We cannot observe the light from 13.7 billion years ago as you have depicted it (traveling directly from the origin) because it would have gone through the space earth now occupies a long time ago. However, if the theory is true, we might be able to see light that old if it were reflected or curved back to us. But we would have to know the path it took to "catch" it, identifying how old light is seems impossible, and gaining information from it seems equally impossible.
Is it called cosmic background MICROWAVE radiation because the original source was microwaves but now it has been shifted to radio waves?
+Ryan Couture Im also confused about this. I thought redshift caused us to perceive microwaves rather than radio waves
3 years late, I think he may have just telling how vast it may become because with the red-shifting the smaller more denser radiations become more stretched out and expand. This would mean in the future there would be radio raves because they would be getting so shifted and expanded.
It was gamma radiation. It has been red-shifted (the wavelength has been elongated) to microwave radiation.
the universe is flat, not a sphere. I thought that this has been argued successfully in a universe from nothing. I guess I have to open my mind even further. How fast does the universe expand?
thanks
space itself is stretching so sure we can observe the cmb. we now think the universe is flat so no we cant see the light reflecting back on us.
Forgive me for being seemingly obtuse. If you are correct then your position is: 1) the universe expanded faster than the speed of a microwave. If it didnt, then how are we seeing the the background radiation from 13.7 Million years. 2) At some point, in about 300k years our anscesters will begin to see photons from the ffrom the formation of atoms? I can't really rap my head around us seeing what happened 13.7 years ago, when our space was within that universe that was indeed created.
Very good video, I was having problems to understand this, now I get it!
Nice very nice 11/10
i love how do you're videos. can you look at this guys videos that says red shift is wrong, and other stuff. i would like if you can comment on them. SUEDESLOUNGE is the name of the guy on youtube.
great video! :P
here is what is bugging - how big was the universe than the emitting of this radiation took place? it was much much smaller than billions of light years, right?
- i assume light speed was already established and this radiation travelled at it
- i assume the stretching of space at that stage was much less than the at the speed of light
combining all these - this radiation of each `emitting point`, travelling at a straight line (no matter the direction), would have left, what we call now, the visible universe, long long lllooonnngg ago
what do i miss here?
thanx
anton
Nice
If energy can't be created or destroyed, where did all the mass and energy in the universe come from? Saying it came from a singularity smaller than a dot on a piece of paper sounds like the most ridiculous thing ever.
Sal - bravo - but every time i attempt to view your cosmology videos within seconds i get the waiting circle, on every computer in my house and have great internet access - very frustrating
never happens with your other teaching videos
you cant see radio waves right?
Check "Lawrence Krauss - A Universe from Nothing" watch?v=EjaGktVQdNg
What was before the big bang, we don't know.
how soon can scientist detect an asteroid moving towards earth ?
I love you Khan :D
Can someone help me, a professor at my school told me that because of CBR the big bang is NOT plausible anymore.
brandy nicole I honestly think we could be the only advanced civilization in the universe or this galaxy at least. The universe has been around for a very long time and if an alien race has had RADAR and radio technology for millions or billions of years longer than we have, we should of picked it up by now. Light is omnidirectional. There a good chance that if their is an advanced society they could be far more primitive than we are i.e could be pre industrial level. It's possible that life on other planets may have existed but couldn't of advanced because they weren't lucky enough to be living in a stable solar system around a stable star like we have.
brandy nicole Do you think, the so called gods of our history were alien beings so advanced that their technology looked like magic. I wouldn't be supplied, if we were to go back in time to the very early civilizations that had barely invented the wheel with a gun and shot an animal we would appear like Gods. Shooting an animal dead would be incomprehensible to them.
Nope.....fallen angels and demons is the proper terms
+WaveForceful - Then God is fake, too, by the same logic.
How did you come to that idea ?
Gods fake ????? No.....he is most certainly not
question: is cosmic background radiation everywhere? even in a room?
Hywel 4 Pretty much, get a Geiger counter out and it will detect low rads.
+Hywel 4 Turn on the television, plug the cable out, you see those white and black dots dancing?? Some part of that noise is CBR.
+WaveForceful That's not CBR.
+WaveForceful You can't detect CBR with Geiger counter, it doesn't detect electromagnetic radiation.
oh, so what's back ground radiation then?.
I don't get what you're saying. If it was uniform then it wasn't dense then.
KOOGHPANYE Imagine pure mercury that’s stagnant.
It is uniform, and it is dense (denser than water at least)
why not?
Where did the singularity come from? Was the singularity intelligent did it have consciousness? Why did it start expanding?
it is a MODEL NOT THEORY
it is 0^0=1
That is not a real number. It's a mathematical error.
i find it difficult to follow your voice...it belies too much "water behind the dam" or too much caffeine...) i.e. you need to calm down, slow down...intelligent people forget they talk too fast...& it is infinitely easier & more satisfying to listen ( & thus, Learn!) from a calm, slow voice...Do you ever meditate, My Friend? Nevertheless i am grateful for your project...Thanks*
This is a contridiction. From "Nothing" ....Nothing comes.....more
what was before the big bang....????
nope .. ITS SOUND FROM THE FEEDBACK LOOP ...
still being made now .. thats why its not changing .. and will never go away ...NOT FROM the BIG Bang .. all Booms and Bangs , Fade .. This is Not Fading , if anything gaining ...
Its all a Loop from Quantum to the largest ... The (Fibonacci JNHM Matrix) Helps to under stand the Math .. Quantum is not random , just in a different space time ..
J-N-H-M That’s a lot of “..” and “...”.
0:46 WHAT DO YOU MEAN YOU DON'T KNOW????? im un subscribing :-)
Lol.
Look at our beautiful Universe expanding! The oval ball of gas must be the great Goddess birthing her children! My only question is if as above so shall it be below! How come women are catching hell from Authorities!? Why is ACS and Dyfus social service only providing services (enforcement via textualism/ promulgation) and not a service?
Can you star with a picture or something?? Why am I looking at a black screen for 30 seconds
hahahahhahaha learn how to do tube videos or get lost !!
I assume that you must be a jew. I am a Freemason. We value truth, you value bullshit. Do you understand our conflict?