Marcelo Gleiser

Who has no regrets about things done in the past? Wouldn't it be nice if, somehow, we could go back to tweak a couple of bad decisions?

This sounds (and as we will see, is, to a certain extent) like science fiction.

As the fox told the prince in Antoine de Saint-Exupéry's wonderful fable The Little Prince: "What is essential is invisible to the eye."

If the fox had not been talking about love, she could have been referring to the elementary particles of matter, the building blocks of everything that exists. The poetry here is in knowing that the world is made of tiny, invisible bits of stuff that carry, in them, the story of creation itself.

On Tuesday, Elon Musk's SpaceX successfully launched its most ambitious rocket to date, the Falcon Heavy.

This is a transformative spacecraft, a behemoth that essentially straps three Falcon 9 rocket cores together. At 224-feet tall, it's smaller than NASA's giant Saturn V (363 feet) — but it is the largest privately built spacecraft to date. The Falcon Heavy is capable of lifting 70 tons of payload to low-Earth orbit and almost 30 tons to a geostationary transfer orbit.

If Victorians were offended by Charles Darwin's claim that we descended from monkeys, imagine their surprise if they heard that our first ancestor was much more primitive than that, a mere single-celled creature, our microbial Eve.

I'm old enough to have grown up in a household with a single rotary telephone.

I imagine that most children would not know what to do with one today. Conversely, my grandparents, if I could bring them back to life, would have had no idea of what to do with a smartphone.

Technology changes the way we live — and it also changes us.

Last week, the PBS series Nova presented an episode on black holes, these most mysterious and mind-boggling physical objects.

In the 19th century, Ralph Waldo Emerson wrote in his essay Nature: "A man is a god in ruins."

Ever since people contemplated the existence of a divine dimension — and this belief must go back to the very early stages of Homo Sapiens or even earlier — with Neanderthals, a split occurred between the human condition and the eternal.

As humans, it is our curse and our blessing to be aware of our own mortality — and to suffer with the loss of our close ones — and, in a broader sense, with the predicament of others.

To close the door on 2017, the strangest year I can remember, there's nothing more appropriate than the revelation in December from the U.S. government that it, indeed, had an office dedicated to the investigation of UFO-related phenomena.

It's enough to make X-Files and conspiracy-theory fans rejoice.

Unless you do live in a galaxy far, far away, you know episode VIII of the Star Wars saga opened last week to much anticipation.

I took my family on Saturday afternoon, making sure I didn't talk to anyone that had seen it already.

[Spoiler Alert: If you haven't watched the movie you may want to wait to read this review until you do.]

Two years ago yesterday, Dec. 12, nearly 200 countries came to a consensus that greenhouse emissions — mostly caused by the burning of fossil fuels — had to be drastically cut if we were to halt the planetary-changing consequences of a choking atmosphere.

Trial and error, experimentation, the understanding that some questions have complex answers or no answers at all, the notion that failure teaches, the acceptance that mistakes can actually guide you in the right direction, persistence in the face of difficulty: These are some of the everyday components of scientific research, accumulated wisdom that can serve us well in many walks of life — from how to face challenges as individuals to running corporations.

Last week, my 13.7 co-blogger Tania Lombrozo reported on a study she developed with graduate student Sara Gottlieb on whether science can explain the human mind.

As Tania wrote, this was a survey-based study asking the participants "whether they thought it was possible for science to one day fully explain various aspects of the human mind, from depth perception and memory loss to spirituality and romantic love."

For this post-Thanksgiving week, I'd like to suggest a remarkable video produced over two decades by NASA scientists.

Satellites monitored populations of plant life on land and oceans, mapping variations of green regions of vegetation and snow cover on the North and South Poles. As seasons pass, we witness a rhythmic dance between white and green, as if the planet itself were breathing.

Since my last post was on Earth's hosting of life, it's natural to follow with a discussion of life elsewhere.

From the outset, we must state two essential facts: first, that we have no concrete evidence that intelligent aliens have ever visited our planet; and, second, that we have no evidence that there is life outside Earth, intelligent or not.

Let's look into the alien visitation question first — and leave the question of life elsewhere for another time.

Living in cities or suburbs, amid the race of everyday routine, we have little time to care about what goes on at the planetary level — or about the uniqueness of our planet.

As Europe was being torn apart in the early 17th century by conflicts between Catholics and Protestants — that would lead to the devastating Thirty Years War in 1618 — the German astronomer Johannes Kepler wrote:

"When the storm rages and the shipwreck of the state threatens, we can do nothing more worthy than to sink the anchor of our peaceful studies into the ground of eternity."

Some 130 million years ago, when dinosaurs roamed Earth, two dead stars in a far-away galaxy collided violently, after spiraling around each other for millions of years.

The dead stars were neutron stars, exotic objects the size of Mount Everest and with the mass of the sun. Being this small and dense, the gravitational force is fierce. Someone once compared the pull of gravity near the surface of a neutron star to having all the population of Paris tied to your feet.

As a Brazilian-born scientist, it pains me to witness the devastating cuts — and proposal of future additional reductions — to the country's science funding.

The cut of 44 percent in March brought the 2017 budget for Brazil's Ministry of Science, Technology, Innovation and Communications the lowest level in 12 years. Additional cuts of about 16 percent have been proposed for the 2018 budget.

In 1915, Albert Einstein concluded his General Theory of Relativity, a theory that would revise our understanding of gravity in radical ways.

Before Einstein, the dominant description of gravitational phenomena was based on Isaac Newton's theory, proposed in 1687. According to Newton, every two objects with mass attract one another with a force proportional to their masses and inversely proportional to the square of their distance: double the distance, the attraction falls by a factor of four.

If it's true that a picture is worth a thousand words, what NASA's Cassini mission has left for us is indeed a treasure.

Launched in 1997, the mission terminated dramatically last week with the probe's final plunge into Saturn's upper atmosphere.

The Sign, a documentary directed, shot and produced by Josh Turnbow and Robert Dvoran and set to air Thursday, addresses whether the end of days is coming this month, as some biblical literalists predict.

The "sign" in the title refers to an alignment in the sky peaking on Sept. 23, whereby Mercury, Venus, Mars, and Jupiter will be around the constellations of Virgo and Leo, together with the sun and moon. Sept. 23 is when Jupiter leaves Virgo after being there for a while.

America seems to be a magnet for devastating hurricanes these days.

This year, Harvey came out strong with its horrific toll on parts of Texas and Louisiana. Now Irma, downgraded slightly Friday morning to a Category 4 storm from its most recent days as a Category 5, has left destruction in its wake as it plows through the Caribbean and Cuba — and is on path to hit Florida Sunday morning.

Hurricane Harvey is a devastating reminder of how helpless we are when facing nature's human-dwarfing powers.

We dig holes and barricades, build dams and create ingenious systems of canals and levees. We try to pull the brakes on natural forces, or at least tame them. These measures protect us, and we surely would be worse off without them. We have come a long way since our cave dwellings.

This has been quite a space week for Americans.

After Monday's stunning solar eclipse, Wednesday night PBS will air its two-hour documentary film about the two Voyager missions, launched 40 years ago. The Farthest: Voyager In Space, celebrates a technological and intellectual achievement rarely matched in history. Two small, nuclear-powered spacecraft have traveled farther than any other man-made machine and have forever changed our views of the solar system — and our place in it.

"Nature loves to hide."

This is how, more than 25 centuries back, the pre-Socratic Greek philosopher Heraclitus of Ephesus expressed the sense of mystery we all feel when we start pondering how the world works.

There seem to be hidden mechanisms, secret pacts between the things that make the world the world, from the smallest building blocks of matter to the neurons in our brains to the way the whole universe is stretching out in its inexorable expansion.

I entered the packed cafeteria with tray in hand, searching for the right food to eat.

Around me, hundreds of people of all ages spoke excitedly in dozens of different languages, commenting on each other's ideas, asking questions, and thinking of the next steps in their research programs.

Lunchtime at the United Nations?

There is comfort in distance, especially when the distance is in time.

Things that will happen far in the future seem not to bother us much, given that we will, most likely, be out of the picture.

On Aug. 21, a narrow, 70-mile wide swath of the United States from Oregon to South Carolina will be the stage for one of the most (if not the most) spectacular celestial events, a total eclipse of the sun.

Space.com has put together a nice informational guide, including a video and a map explaining where to go, what to expect, and how to watch it safely. This is the first total solar eclipse in America in almost 40 years. The next one in the U.S. will be on April 8, 2024.

In the current issue of the New York Review of Books, David Kaiser and Lee Wasserman, the president and the director of the Rockefeller Family Fund (RFF), respectively, explain why the organization decided to divest its holdings on fossil fuel companies.

Although the divesting decision is broad-ranging, they single out ExxonMobil for its "morally reprehensible conduct."

Even with all the drama — and now the prolonged silence, possibly permanent — the European Space Agency's (ESA) mission to land a fridge-sized probe on a comet zipping at about 80,000 miles per hour, some 300 million miles from Earth, was a resounding success. This first ever comet landing has captivated the world as very few events in the history — certainly the recent history — of space exploration have.

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