1. Pale Blue Dot
Here it is:
Certainly doesn't look like much at first glance. So why the lofty claim?
Here's the 'dot' in reference:
That dot is the planet Earth, photographed in 1990 by the spacecraft Voyager 1 from beyond the orbit of Pluto.
This picture exists largely thanks to the great Carl Sagan, who convinced NASA to command the spacecraft to turn its camera around and take one last photograph before ending its mission and leaving the solar system.
It's certainly the farthest anything has ever been photographed, a distance of 6 Billion kilometers between the camera and the subject. At that distance, Earth appears so tiny that it takes up less than 0.12 of a single pixel. The image has to be greatly magnified for the Earth to become just barely visible. The full image is below (click to enlarge):
Here, the image from above is the inset square on the left, showing a large magnification of the true image. Venus (pale yellow dot?) is also visible, within the magnified inset on the right. The bright circle on the on the far right is the Sun (though note that it appears a lot larger than scale due to it's brightness). The coloured streaks or lines within each inset that both planets appear within are the Sun's rays, appearing as bands due to magnification and refraction.
As to the significance of this picture, Carl Sagan said it as poignantly as I can imagine possible in his book also titled Pale Blue Dot:
"Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there--on a mote of dust suspended in a sunbeam.
The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.
The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known."
2. Hubble Deep Field
Becoming operational in 1990 (coincidentally the same year the Pale Blue Dot was photographed, a great year for astro-photography), the Hubble Space Telescope orbits the Earth at an altitude of 540 km.
It weighs 11,110 kgs and is around the size of a school bus:
Naturally, building and putting it into orbit was no small feat. It took nearly 12 years to construct and has cost some $11.3 Billion till date.
Yet when it became operational, the first images it returned were uselessly blurry. The problem was traced to a manufacturing defect in its mirror, which had a polishing error of just 0.002mm (much thinner than a human hair)..yet enough to render the entire telescope useless! Happily, the problem was corrected shortly thereafter by installing a replacement mirror, in space, manually by astronauts:
Thereafter, the astounding images that Hubble has captured might justifiably earn this venerable instrument the title of the greatest telescope + camera ever built...images such as:
Saturn, with it's moon Titan casting a shadow
The Sombrero galaxy
The 'Pillars of Creation', a massive gas cloud or nebula 100 Million times larger than the Sun
to picture just a paltry few from Hubble's prolific and mesmerising portfolio.
However even so, the most significant picture Hubble may yet have taken could easily be the Hubble Deep Field.
In 1996, Hubble's operators pointed it at a tiny, seemingly empty and jet black region of space a mere 2.6 arc minutes wide. Pictured below is how small this region was compared to the apparent size of the moon in the sky:
The telescope focused on the region for 10 days, and this was the result (click to enlarge):
In this image (other than 4-5 bright blobs which are foreground stars), every single other artefact, even the faintest point of light, is an entire galaxy! There are over 10,000 galaxies in this image, each containing an average 200 billion stars.
All this from a tiny pinprick in the sky.
Based in part on this observation, astronomers have extrapolated the total numbers of stars in the observable universe to be somewhere between 10^22 and 10^24. To put that into perspective, researchers at the University of Hawaii have calculated the total number of grains of sand from every beach on Earth to be around 7.5 x 10^18.
That means there are more stars in the universe than grains of sand on every beach on the entire Earth. How many more? 10,000 times more! As in, if we made 10,000 copies of the Earth, there would still be more stars in the observable universe than the numbers of individual grains of sand in every beach of all those Earths combined.
Think about that next time you go to the beach.
References:
https://en.wikipedia.org/wiki/Pale_Blue_Dot
https://en.wikipedia.org/wiki/Hubble_Deep_Field
https://en.wikipedia.org/wiki/Hubble_Ultra-Deep_Field
https://www.nature.com/articles/nature.2015.17345
https://waitbutwhy.com/2013/11/4-mind-blowing-things-about-stars.html
Becoming operational in 1990 (coincidentally the same year the Pale Blue Dot was photographed, a great year for astro-photography), the Hubble Space Telescope orbits the Earth at an altitude of 540 km.
It weighs 11,110 kgs and is around the size of a school bus:
Naturally, building and putting it into orbit was no small feat. It took nearly 20 years to construct and has cost some $11.3 Billion till date.
Yet when it became operational, the first images it returned were uselessly blurry. The problem was traced to a manufacturing error in the polishing of its mirror, which resulted in one lens being out of position by a just 1.3mm...yet enough to render the entire telescope useless! Happily, the problem was corrected shortly thereafter by installing a replacement mirror, in space, manually by astronauts:
Thereafter, the astounding images that Hubble has captured might justifiably earn this venerable instrument the title of the greatest telescope + camera ever built...images such as:
Saturn, with it's moon Titan casting a shadow
The Sombrero galaxy
The 'Pillars of Creation', a massive gas cloud or nebula 100 Million times larger than the Sun
to picture just a paltry few from Hubble's prolific and mesmerising portfolio.
However even so, the most significant picture Hubble may yet have taken could easily be the Hubble Deep Field.
In 1996, Hubble's operators pointed it at a tiny, seemingly empty and jet black region of space a mere 2.6 arc minutes wide. Pictured below is how small this region was compared to the apparent size of the moon in the sky:
The telescope focused on the region for 10 days, and this was the result (click to enlarge):
In this image (other than 4-5 bright blobs which are foreground stars), every single other artefact, even the faintest point of light, is an entire galaxy! There are over 10,000 galaxies in this image, each containing an average 200 billion stars.
All this from a tiny pinprick in the sky.
Based in part on this observation, astronomers have extrapolated the total numbers of stars in the observable universe to be somewhere between 10^22 and 10^24. To put that into perspective, researchers at the University of Hawaii have calculated the total number of grains of sand from every beach on Earth to be around 7.5 x 10^18.
That means there are more stars in the universe than grains of sand on every beach on the entire Earth. How many more? 10,000 times more! As in, if we made 10,000 copies of the Earth, there would still be more stars in the observable universe than the numbers of individual grains of sand in every beach of all those Earths combined.
Think about that next time you go to the beach.
References:
https://en.wikipedia.org/wiki/Pale_Blue_Dot
https://en.wikipedia.org/wiki/Hubble_Deep_Field
https://en.wikipedia.org/wiki/Hubble_Ultra-Deep_Field
https://www.nature.com/articles/nature.2015.17345
https://waitbutwhy.com/2013/11/4-mind-blowing-things-about-stars.html
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