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esiegel | June 4, 2016"Until the 1990s, there were few reliable observations about movement at the scale of the entire universe, which is the only scale dark energy effects. So dark energy could not be seen until we could measure things very, very far away." -Adam Riess
Just thirty years ago, scientists argued over the value of the Hubble expansion rate, and what it meant for the age, history and fate of the Universe. Was the Universe expanding slowly (~55 km/s/Mpc), was it very old, and would it coast to infinity? Or was it expanding rapidly (~100 km/s/Mpc), was it young, and would it eventually recollapse?…
esiegel | May 28, 2016“A long time ago people believed that the world is flat and the moon is made of green cheese. Some still do, to this day. The man on the moon is looking down and laughing.” -Vera Nazarian
When people make claims that are patently untrue -- like the Earth is flat -- perhaps your knee-jerk reaction is to ridicule them. If you dig a little deeper, however, you'll likely discover a truth about your own past: that you once held views that flew in the face of the scientific evidence, only you weren't aware of it at the time.
During the partial phases of a lunar eclipse, the shadow of Earth can be…
esiegel | May 21, 2016"When you get just a complete sense of blackness or void ahead of you, that somehow the future looks an impossible place to be, and the direction you are going seems to have no purpose, there is this word despair which is a very awful thing to feel." -Stephen Fry
Perhaps the most fundamental difference between day and night is the difference between light and dark that our eyes perceive. While everything is illuminated during the day, the night sky is completely dark, with the sole exception of the stars, galaxies and objects reflecting sunlight back at our world.
The full UV-visible-IR…
esiegel | May 14, 2016“The beauty of a living thing is not the atoms that go into it, but the way those atoms are put together.” -Carl Sagan
Inside a typical human body, beneath the organs, cells and even molecules that define us, there are atoms: some 7 × 10^27 of them in each of us. Mostly oxygen, carbon, hydrogen and nitrogen (with less than 1% of everything else combined), this tremendous number leads to an intriguing possibility: that at any given moment in your life, some of those atoms were once inside any historical living being you choose.
The elements in the human body. Image credit: Openstax college,…
esiegel | May 7, 2016“A single day is enough to make us a little larger or, another time, a little smaller.” -Paul Klee
When it comes to normal matter, dark matter is a bit of a puzzle. Other than through the gravitational force, there's no way we've yet figured out to make it interact. Try and collide it with matter and it passes right through; try and bombard it with energetic particles or radiation and it's completely transparent. But the story is quite different when it comes to dark matter and black holes.
A black hole feeding off of an accretion disk. Image credit: Mark Garlick (University of Warwick).…
esiegel | April 30, 2016"Trying to understand the way nature works involves a most terrible test of human reasoning ability. It involves subtle trickery, beautiful tightropes of logic on which one has to walk in order not to make a mistake in predicting what will happen." -Richard Feynman
If you were to send a space probe to a distant star system, gather information about it and send it back to Earth, you'd have to wait years for the information to arrive. But if you have an entangled quantum system -- say, two photons, one with spin +1 and one with spin -1 -- you could know the spin of the distant one instantly by…
esiegel | April 23, 2016"Yes, now there is this technological path. But it's just starting." -Mae Jemison
Earlier this month, Yuri Milner and Stephen Hawking teamed up to announce the Breakthrough Starshot, a $100 million investment in technology that would build a laser array to propel a thin, light "laser sail" spacecraft to approximately 20% the speed of light. If we can achieve these speeds and sufficiently aim these sails at the nearest star systems, we'll arrive at our destinations within a single human lifetime.
Illustration of an exoplanetary system. Image credit: NASA/David Hardy, via astroart.org.
But…
esiegel | April 16, 2016"If we cannot now end our differences, at least we can help make the world safe for diversity." -John F. Kennedy
No one likes being denied an opportunity -- or told they shouldn't do something they want to -- solely because of the way they are. That's especially true when it comes to something that's an intrinsic part of one's self, such as their race, gender, demeanor or personality. Which is why it surprised me to have my own legitimacy as a scientist questioned because of the way I choose to present myself to the world.
Image credit: J. Cummings, of Ethan Siegel in 2015.
I think it's…
esiegel | April 9, 2016"An asteroid or a supervolcano could certainly destroy us, but we also face risks the dinosaurs never saw: An engineered virus, nuclear war, inadvertent creation of a micro black hole, or some as-yet-unknown technology could spell the end of us." -Elon Musk
The possibility of getting hit by a wayward asteroid or comet is a scenario that could range from an expensive inconvenience to a mass extinction-level event, depending on the mass and speed of the potential impactor. While recent events like Chelyabinsk and Tunguska -- and more energetic ones like Barringer crater and the Cretaceous-…
esiegel | April 2, 2016"You've got to learn to let go." -Matt Kowalski, Gravity
Objects in motion remain in constant motion unless acted upon by an outside force. That's Newton's 1st law of motion, and that's why you'd expect an orbiting satellite and two astronauts orbiting with it to have absolutely no relative forces.
Image credit: Warner Bros. Pictures / Alfonso Cuarón, of the poster for the movie Gravity.
Yet if you watched the movie Gravity, you saw that the two astronauts, Stone and Kowalski, definitely experienced forces relative to the International Space Station when they were hanging onto it by a…
esiegel | March 26, 2016"When a person starts to talk about their dreams, it's as if something bubbles up from within. Their eyes brighten, their face glows, and you can feel the excitement in their words." -John C. Maxwell
One of the most remarkable features of a great number of giant, active galaxies are the presence of jets of hyper-accelerated matter, spanning thousands of light years. Correlated with feeding, supermassive black holes are these huge structures of light-emitting matter, identifiable from many millions of light years away.
The giant elliptical galaxy, M87, and its 5,000+ light year-long jet,…
esiegel | March 18, 2016"Quintessence is a dynamic, time-evolving, and spatially dependent form of energy with negative pressure sufficient to drive the accelerating expansion [...] Whereas the cosmological constant is a very specific form of energy." -Robert Caldwell, inventor of the Big Rip scenario
Our Universe began with a period of cosmic inflation: where energy intrinsic to space itself caused an extremely rapid, exponential expansion. This stretched the Universe flat, gave it the same properties, temperature and spectrum of fluctuations everywhere, and then gave rise to the hot Big Bang. And our Universe is…
esiegel | March 12, 2016"It is in the theory of perception that we have established our bond, or the lie I should say, for which we kill. We are nothing without our image. Without our projection. Without the spiritual hologram of who we perceive ourselves to be or rather to become, in the future. When you are lonely, I will be lonely too. And this is the fame." -Lady Gaga
One of the more remarkable discoveries in human technology is the hologram. Instead of mapping a snapshot of our three-dimensional world from a single perspective onto a two-dimensional surface, we can create a light map of the entire three-…
esiegel | March 5, 2016
“Youth always tries to fill the void, an old man learns to live with it.” -Mark Z. Danielewski
There are plenty of scientific myths that go around, including many that were generated recently by so-called science communicators that actively harm public knowledge. One of them was a now-famous image of a dark nebula silhouetted against a star field, claiming that this was a hole in the Universe a billion light years across with no matter in it.
Image credit: ESO, of the same object in a composite of visible, near-IR and farther-IR light.
Not only is the image itself a completely…
esiegel | February 27, 2016"The bedrock nature of space and time and the unification of cosmos and quantum are surely among science's great 'open frontiers.' These are parts of the intellectual map where we're still groping for the truth - where, in the fashion of ancient cartographers, we must still inscribe 'here be dragons.'" -Martin Rees
We know the Earth is an almost-perfect sphere, yet maps of it always stretch it down to a two-dimensional surface. Outer space, too, when we look at it, offers views that extend deep into the cosmos in all directions, also on a sphere. But if you want to make a map of the Universe…
esiegel | February 20, 2016“You asked me how to get out of the finite dimensions when I feel like it. I certainly don't use logic when I do it. Logic's the first thing you have to get rid of.” -J.D. Salinger
Now that gravitational waves have been verified to exist, and the first black hole-black hole merger has been definitively detected by LIGO, it's time to start thinking of the next steps in gravitational wave astronomy. The biggest one we can dream of, perhaps the holy grail of this field of study, is to go beyond General Relativity itself, and to find evidence that gravitation is a truly quantum theory at its core…
esiegel | February 13, 2016"I cannot help fearing that men may reach a point where they look on every new theory as a danger, every innovation as a toilsome trouble, every social advance as a first step toward revolution, and that they may absolutely refuse to move at all." -Alexis de Tocqueville
You don’t need to be right to be a scientist, and your theory doesn’t need to be correct to be a scientific theory. While there is a big difference between the way we colloquially use the word theory (to mean “idea”) and the way scientists use it (to mean “testable idea”), there are actually three different stages that…
esiegel | February 6, 2016"Biological diversity is messy. It walks, it crawls, it swims, it swoops, it buzzes. But extinction is silent, and it has no voice other than our own." -Paul Hawken
Looking at the history of life on Earth, the fossil record shows something incontrovertible: in order for new forms of life to rise to dominance, it requires something to knock the prior forms from dominating their ecological niche. This can come about in any number of ways, but the most striking changes come from catastrophic events that wipe a large percentage of species off the Earth at once: a mass extinction event.
Image…
esiegel | January 23, 2016"Do not look at stars as bright spots only. Try to take in the vastness of the universe." -Maria Mitchell
The analogies between small-scale, living things and large-scale, cosmic entities are abundant: between a neuron and the Universe's large-scale structure; between an atom and a solar system; between the stars in a galaxy and the atoms in a cell; between the cells in a living being and the galaxies in the Universe. It makes you wonder if, on a cosmic scale, some portion (or the whole) of the Universe could actually be alive and self-aware?
Image credit: Greyloch / Universal Design of…
esiegel | January 16, 2016"Einstein's gravitational theory, which is said to be the greatest single achievement of theoretical physics, resulted in beautiful relations connecting gravitational phenomena with the geometry of space; this was an exciting idea." -Richard P. Feynman
When Einstein's theory was first proposed as an alternative to Newtonian gravity, there were a number of subtle but important theoretical differences noted between the two. Einstein's theory predicted gravitational redshift, time delays, bending of light and more. But what was perhaps most remarkable is that unlike Newton's gravity, Einstein's…