Why humanity is a cosmic tale of despair and hope | by Ethan Siegel | Starts With A Bang! | Jul, 2024

MarylandDigitalNews.comSCIENCE

posted on Jul. 15, 2024 at 2:15 pm

In 1977, NASA’s Voyager 1 and 2 spacecraft began their pioneering journey across the Solar System to visit the giant outer planets. Now, the Voyagers are hurtling through unexplored territory on their road trip beyond our Solar System. Along the way, they are measuring the interstellar medium, the mysterious environment between stars that is filled with the debris from long-dead stars. Voyager 1 became the most distant spacecraft from Earth in 1998, and no other spacecraft launched, to date, has a chance of catching it. (Credit: NASA, ESA, and G. Bacon)

On a cosmic scale, our existence seems insignificant and inconsequential. But from another perspective, humans are completely remarkable.

On the scale of the Universe, humanity isn’t even a speck.

This vertically oriented logarithmic map of the Universe spans nearly 20 orders of magnitude, taking us from planet Earth to the edge of the visible Universe. Each large “mark” on the right side’s scale bar corresponds to an increase in distance scales by a factor of 10. (Credit: Pablo Carlos Budassi)

We’re each just a tiny, minuscule fraction of our own planet: Earth.

Apollo 8 astronauts were the first humans to reach great enough distances from our planet to be able to view the entire Earth at once. Here, the closest (left) and farthest (right) images of the Earth are shown as acquired with the same Hasselblad camera. Except for the three humans on board at the moment, all of humanity is confined to the pale, blue dot on the right. (Credit: NASA/Apollo 8/Johnson Space Center)

It would take nearly an Avogadro’s number of humans to equal Earth’s mass.

Under ideal dark sky conditions, the unaided human eye can see up to 6000 stars at once, and up to 9000 stars total if they could see the full sky at once, unblocked by the Earth itself. Compared to the Earth, at ~6 septillion kilograms, all 8+ billion humans, combined, are barely a drop in the bucket of planet Earth’s total mass. (Credit: callisto / Adobe Stock)

Earth is just one modest planet orbiting our Sun: one of ~400 billion stars within the Milky Way.

This color-coded map shows the heavy element abundances of more than 6 million stars within the Milky Way. Stars in red, orange, and yellow are all rich enough in heavy elements that they should have planets; green and cyan-coded stars should only rarely have planets, and stars coded blue or violet should have absolutely no planets at all around them. Note that the central plane of the galactic disk, extending all the way into the galactic core, has the potential for habitable, rocky planets. This map shows fewer than 0.01% of the stars within our galaxy. (Credit: ESA/Gaia/DPAC; CC BY-SA 3.0 IGO)

MarylandDigitalNews.comJuly 15, 2024

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