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

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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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Green Llama says:

What program is he using?

Joshy says:

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

Nicole Li says:

really helpful! thanks a lot

MrWillybillly says:

great video, thanks

antonio casagrande says:

Thanks man! Very helpful!

my name is my name says:

i thought it as draw to scale alllll along :p

xxxxxrandom says:

typo at 8 mins
m = milli = 0.001
M = Mega = 1 000 000
Still very clearly explained.

Сергей says:

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: // /hubbles.htm

therealjordiano says:

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

Jonathan Doolin says:

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

shankyxyz says:

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).

Anon says:

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?

Thorloar says:

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!

Thorloar says:

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
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.

Nate Jones says:

im gonna go and assume it's Dr. Khan…

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