In 2003 NASA pointed the Hubble Telescope at a region of seemingly empty sky and left it there. Over the course of two months, imperceptible drips of light collected in the basin of its 8 foot wide mirror. When they finally combined the 800 exposures of nearly perfectly black sky, a total of 11 days worth of light, they revealed an image speckled with 10,000 galaxies. The oldest of the photons that ended their life in the electronics of the Hubble had traveled from their birth star across the universe for 13.2 billion years. These photons had already completed half of their journey when the earth coalesced.
10,000 galaxies. Our own galaxy, not exceptional in any way, contains around 100 billion stars. In the patch that the Hubble photographed, the size of a millimeter held a meter away, there are on the order of a quadrillion stars. And yet it would take 12 million of such patches to tile the sphere of the sky.
How can we understand the scale of this? A quadrillion is a ridiculous number. It’s the kind of number that young boys make up at recess to say how much stupider their friends are, combining syllables at random, not even sure if it’s real.
Consider the leaves of a forest.
A mature tree has somewhere around 50,000 leaves.
The state of Pennsylvania has 16 billion trees.
There are as many stars in the Hubble Ultra Deep Field as there are leaves on all the trees in the state of Pennsylvania.
Consider grass in a meadow.
There are around 50 blades of grass in a square inch of meadow.
The Willamette Valley is 5700 square miles.
If the Willamette valley were all grassland, it would contain as many blades of grass as there are stars in the Hubble Ultra Deep Field.
Consider the rain in a thunderstorm.
A raindrop in a large storm weighs around a tenth of a gram.
A convective storm system can drop 100 million tons of rain.
There are as many raindrops in a large storm system as there are stars in the Hubble Ultra Deep Field.
Consider sand on a beach.
There are about 1 billion grains of sand in a cubic foot.
Ocean beach in San Francisco has around 4,500,000 square feet of sand above water.
The top 3 inches of sand of the whole surface of Ocean Beach contain as many grains of sand as there are stars in the Hubble Ultra Deep Field.
Consider the ocean.
A milliliter of ocean water can contain a million plankton.
An olympic swimming pool contains 2.5 million liters of water.
A pool filled with sea water can contain as many plankton as there are stars in the Hubble Ultra Deep Field.
One quadrillion stars, in a tiny slice of the sky. If we photographed the entire sky this way, we would have to multiply all of these numbers by twelve million. This is our universe as far as we can see, twelve million Pennsylvania’s leaves, twelve million Willamette Valley’s blades of grass, twelve million storm systems of rain, twelve million Ocean Beaches of sand, twelve million swimming pools of plankton.
The Hubble Ultra Deep Field
The James Webb Space Telescope is currently on its way to its destination far from the earth where it will look into the early universe without the glare of the sun and the earth to interfere. On March 16th, it produced an image of a star that it was using to calibrate its mirrors. A distant star is a point source of light, and so by making fine adjustments to the mirrors to resolve that point more clearly, it can tune them to make clear images. In the process, it captured an image full of distant galaxies by accident.
The James Webb Telescope is expected to begin taking its first real images in June. Just imagine the scale of what we’ll see.
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