## Hubble’s law | Scale of the universe | Cosmology & Astronomy | Khan Academy

Hubble's Law. 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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Hubble’s Law. Created by Sal Khan.

Watch the next lesson: https://www.khanacademy.org/science/cosmology-and-astronomy/universe-scale-topic/big-bang-expansion-topic/v/a-universe-smaller-than-the-observable?utm_source=YT&utm_medium=Desc&utm_campaign=cosmologystronomy

Missed the previous lesson? https://www.khanacademy.org/science/cosmology-and-astronomy/universe-scale-topic/big-bang-expansion-topic/v/cosmic-background-radiation-2?utm_source=YT&utm_medium=Desc&utm_campaign=cosmologystronomy

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!

About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. We tackle math, science, computer programming, history, art history, economics, and more. Our math missions guide learners from kindergarten to calculus using state-of-the-art, adaptive technology that identifies strengths and learning gaps. We’ve also partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content.

For free. For everyone. Forever. #YouCanLearnAnything

Subscribe to Khan Academy’s Cosmology & Astronomy channel: https://www.youtube.com/channel/UChNPnEkW8LYZ5Rwi8_A2-DA?sub_confirmation=1

Subscribe to Khan Academy: https://www.youtube.com/subscription_center?add_user=khanacademy

*Related*

What program is he using?

doesn't he mean 7 milliion lightyears at 9:06 ?

really helpful! thanks a lot

great video, thanks

Thanks man! Very helpful!

i thought it as draw to scale alllll along :p

typo at 8 mins

m = milli = 0.001

M = Mega = 1 000 000

Still very clearly explained.

Hubble's quantum law states that a photon's frequency decreases with each new wave oscillation by a quantum amount equal to the Hubble constant, which is being observed as a redshift. To determine by how much the frequency of the photon has decreased, the Hubble constant must be multiplied by the number of the committed oscillations that is completely consistent with the results obtained by the modern method of the "standard candles".

A report in MSU: ht_tp: //alemanow.narod.ru /hubbles.htm

this would make for some nice homework excuses.. 'sir, all the letters on my essay just started drifting away from each other :|'

Hi Mr. Khan. Your videos have inspired me to make my own. Not quite up to your level of quality yet, but they're getting better over time. Here's what I made about Hubble's Law a couple of months ago: watch?v=9ZpaBqiMwi8

in any local area of space anything can be happening. these laws/rules are valid at the large. For e.g. if a comet moves towards earth, it is not violating the idea that everything (in general and in the large) is moving away from everything else (in general and in the large).

If the galaxies aren't moving in space, but rather moving away from eachother because of the expansion of the universe. Then why do scientiest say that the milkyway and the andromeda galaxy will collide in 2-3 billion years? Shouldn't they be moving away from eachother?

also the expansion of the universe is tought to be an expansion of space/time itself so the speed of the exspansion distance/time does not change as it is the distance and the time that expand together so 1/2 light year becomes 2/4 light years, the same. Dark matter is thought to be nothing but matter that does not emmit el;ectromagnetic radeation, literaly dark matter. Some has actualy reacently been found by calculating galactic orbits. A good write up is on Discover Magaziens web page!

No no mater can move faster than light, and no mater with any mass can move as fast as light. this boils down to Einstines famous prof E=mc^2 for light or

E^2=(m0^2*c^4)+p^2*c^2)

where E is energy m0 is the mass at rest c is speed of light(vacume) pis momentum

from this pathagorean equation you can tell that nothing can reach the speed of light because the hypotenuse of the triangle is always longer than the longer leg.

im gonna go and assume it's Dr. Khan…