Today we know the age of the Universe to a much higher precision than before Hubble: around Hubble has made enormous progress possible within cosmology. We have seen a dramatic change from misery to glory! Gustav A.

## Scale of the large (video) | Khan Academy

Tammann Astronomer, University of Basel. One of Hubble's initial 'core' purposes was to determine the rate of expansion of the Universe, known to astronomers as the "Hubble Constant". Hubble's sharp vision means that it can see exploding stars, supernovae that are billions of light years away and difficult for other telescopes to study. A supernova image from the ground usually blends in with the image of its host galaxy. Hubble can distinguish the light from the two sources and thus measure the supernova directly.

For many years cosmologists have discussed whether the expansion of the Universe would stop in some distant future or continue ever more slowly. From the new supernova results it seems clear that the expansion is nowhere near slowing down. In fact, due to some mysterious property of space itself, called dark energy, the expansion is accelerating and will continue forever.

Now, if you multiply that by 10, you get to the size of a large city. And this right here is a satellite photograph of San Francisco. This is the actual Golden Gate Bridge here. And when I copy and pasted this picture, I tried to make it roughly 10 miles by 10 miles just so you appreciate the scale. And what's interesting here-- and this picture's interesting. Because this is the first time we can relate to cities. But when you look at a city on this scale, it's starting to get larger than what we're used to processing on a daily basis.

A bridge-- we've been on a bridge. We know what a bridge looks like. We know that a bridge is huge. But it doesn't feel like something that we can't comprehend. Already, a city is something that we can't comprehend all at once.

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We can drive across a city. We can look at satellite imagery.

## Observable universe

But if I were to show a human on this, it would be unbelievably, unbelievably small. You wouldn't actually be able to see it. It would be less than a pixel on this image. A house is less than a pixel on this image. But let's keep multiplying by If you multiply by 10 again, you get to something roughly the size of the San Francisco Bay Area. This whole square over here is roughly that square right over there.

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Let's multiply by 10 again. So this square is about miles by miles.

So this one would be about 1, miles by 1, miles. And now you're including a big part of the Western United States. You have California here. You Nevada here.

## Measuring the age and size of the Universe

You have Arizona and New Mexico-- so a big chunk of a big continent we're already including. And frankly, this is beyond the scale that we're used to operating. We've seen maps, so maybe we're a little used to it. But if you ever had to walk across this type of distance, it would take you a while. To some degree, the fact that planes goes so fast-- almost unimaginably fast for us-- that it's made it feel like things like continents aren't as big. Because you can fly across them in five or six hours.

But these are already huge, huge, huge distances. But once again, you take this square that's about 1, miles by 1, miles, and you multiply that by And you get pretty close-- a little bit over-- the diameter of the Earth-- a little bit over the diameter of the Earth.

But once again, we're on the Earth. We kind of relate to the Earth.

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If you look carefully at the horizon, you might see a little bit of a curvature, especially if you were to get into the plane. So even though this is, frankly, larger than my brain can really grasp, we can kind of relate to the Earth. Now you multiply the diameter of Earth times And you get to the diameter of Jupiter. And so if you were to sit Earth right next to Jupiter-- obviously, they're nowhere near that close. That would destroy both of the planets. Actually, it would definitely destroy Earth. It would probably just be merged into Jupiter. So if you put Earth next to Jupiter, it would look something like that right over there.

So I would say that Jupiter is definitely-- on this diagram that I'm drawing here-- is definitely the first thing that I have I can't comprehend. The Earth, itself, is so vastly huge. Jupiter is-- it's 10 times bigger in diameter. It's much larger in terms of mass, and volume, and all the rest. But just in terms of diameter, it is 10 times bigger. But let's keep going. This is times So if this is the Sun-- and if I were to draw Jupiter, it would look something like-- I'll do Jupiter in pink-- Jupiter would be around that big. And then the Earth would be around that big if you were to put them all next to each other.

So the Sun, once again, is huge. Even though we see it almost every day, it is unimaginably huge. Even the Earth is unimaginably huge. And the Sun is times more unimaginably bigger. Now we're going to start getting really, really, really wacky. You multiply the diameter of the Sun, which is already times the diameter of the Earth-- you multiply that times And that is the distance from the Earth to the Sun. So I've drawn the Sun here as a little pixel. And I didn't even draw the Earth as a pixel. Because a pixel would be way too large. It would have to be a hundredth of a pixel in order to draw the Earth properly.

So this is a unbelievable distance between the Earth and the Sun. It's times the distance of the diameter of the Sun itself. So it's massive, massive.