Why String Theory Is Both A Dream And A Nightmare

“The problem, as many see it, is that string theory was a very good idea, and people have a hard time abandoning good ideas no matter how fruitless their pursuit has been. Even though it didn’t work out as a theory of the strong interactions, it provided the germ of what could become the holy grail of modern physics: a theory of quantum gravity that unifies General Relativity with the Standard Model.

So long as we don’t have evidence that demonstrates string theory must be wrong, people will continue to pursue it. But disproving it would require something like demonstrating that no superparticles exist all the way up to the Planck scale, something far beyond the reach of experimental physics today.

We can all agree that string theory is interesting for the possibilities it holds. Whether those possibilities are relevant or meaningful for our Universe, however, is something science has yet to affirm.”

We absolutely don’t have a quantum theory of gravity, and many lines of evidence suggest that we need one. Could string theory be that long sought-after theory? If so, it would unify the Standard Model and gravity into one single framework, which is amazing. But it also has a large number of other predictions, none of which have been borne out by experiment and observation, and many of which seem to run contrary to what we’ve already seen.

String theory may be the ultimate dream of many physicists, but its failures and lack-of-successes are the ultimate nightmare of many more.

Will Alien Life First Be Discovered On Europa, Exoplanets, Or From Extraterrestrials?

“If it exists on a world in our Solar System, like Mars or Europa, we’ll finally be sending space probes with the capability of finding those biosignatures. If life exists and has thrived for a long time on a nearby exoplanets, direct imaging or transit spectroscopy could reveal hints or even surefire evidence of that planetary transformation. And if intelligent aliens are trying to contact us, we’re better positioned to pick up those beacons than ever before.

For as long as humans have existed, we’ve wondered whether life on Earth is all there is and if we’re alone in the Universe, or if other life forms exist on worlds beyond our own planet. As the 2020s dawns, we have better prospects than ever for discovering life on all three possible fronts. With billions of potentially inhabited worlds in our galaxy alone, even if life is relatively rare, we’re still in great position to detect what scant life does exist. Arguably, the biggest question isn’t whether we’re alone or not, but rather how and where we’ll find our first evidence for life beyond Earth.”

It’s the start of the 2020s, and humanity still hasn’t determined whether we’re alone in the Universe or not. We’ve never found a single surefire signature of the existence of extraterrestrial life: not in our solar system, not on planets around other stars, not from intelligent, spacefaring aliens. But if there are alien life forms out there, inhabiting other planets and leaving their biological imprints on them, we have three entirely unique and complementary approaches to uncovering them.

So how will we get there first? Come explore the possibilities and see where the technology will take us this decade!

Should NASA Send New Horizons To A Nearby Star For Its Final Mission?

“Over the next million years, the Voyagers and Pioneers will approach numerous stars, but only at relatively large separations. The closest will be Pioneer 10, encountering HIP 1177795 in ~90,000 years from 0.75 light-years away. But New Horizons, unlike the others, still has significant fuel remaining. After encountering Pluto and Arrokoth, it may yet target another object in the outer Kuiper belt. Subsequently, it will eventually enter interstellar space, but can be boosted to approach future stellar targets.”

In the 1970s, four spacecraft were launched with speeds large enough that they would eventually escape the Solar System: Pioneer 10 and 11 and Voyager 1 and 2. In the 2000s, New Horizons became the fifth spacecraft that will leave the Solar System and enter interstellar space. But unlike the other four, it still has fuel remaining and could boost itself to alter its trajectory. In the aftermath of the ESA’s Gaia mission, we now can predict where more than a billion stars in the Milky Way will be located up to a million years in the future, raising the possibility that we could alter New Horizon’s trajectory to encounter another solar system in the distant future.

Should we do it? Of course we should! Come learn about this fascinating possibility today.

Ask Ethan: Does Dark Energy Gravitate?

“Does dark energy gravititate? In other words does the increase in dark energy as space expands also create more gravity?”

Dark energy is the name we give to whatever’s responsible for the accelerated expansion of the Universe. According to our best theory of gravity, General Relativity, dark energy does indeed have an energy density, which doesn’t appear to be changing over time. This is bizarre, because for everything else, like matter and radiation, the fact that the Universe is expanding means that the density of “stuff” dilutes as time goes on. But for dark energy, it’s a form of energy that appears to be inherent to space itself, meaning that as the Universe expands, its density never goes down. You might think that adding more and more energy in the Universe would just cause it to gravitate more and more severely, though, eventually leading to a recollapse. That’s not what’s going on at all, though.

Why doesn’t dark energy lead to a recollapse? Does this mean the expanding Universe violates the conservation of energy? And what does it mean for dark energy to gravitate? Come get the answers today.

These 4 Pieces Of Evidence Have Already Taken Us Beyond The Big Bang

“There are other predictions of cosmic inflation, too. Inflation predicts that the Universe should be almost perfectly flat, but not quite, with the degree of curvature falling somewhere within 0.0001% and 0.01%. The scalar spectral index, measured to depart slightly from scale invariance, should “roll” (or change during the final stages of inflation) by about 0.1%. And there should be a set of not just density fluctuations, but gravitational wave fluctuations that arise from inflation. So far, observations are consistent with all of these, but we have not reached the level of precision necessary to test them.

But four independent tests are more than enough to draw a conclusion. Despite the voices of a few detractors who refuse to accept this evidence, we can now confidently state that we’ve gone before the Big Bang, and cosmic inflation led to the birth of our Universe. The next question, of what happened prior to the end of inflation, is now at the frontier of 21st century cosmology.”

Did the Universe really begin with a Big Bang? Although there’s an overwhelming suite of evidence in support of our modern Universe arising from a very hot, dense, expanding state a finite amount of time ago, the Big Bang is not the origin of our Universe. For decades, now, we’ve had multiple lines of evidence that demonstrate that no, you cannot extrapolate the Big Bang all the way back to arbitrarily high energies and densities: to a singularity. But a series of puzzles led to a spectacular idea: cosmic inflation, which could have set up and preceded the Big Bang. While inflation’s detractors frequently make the news, the scientific data is overwhelmingly in favor of it. 

Inflation has made concrete predictions, and of the ones that have been tested, inflation is 4-for-4. Come learn what lies beyond the Big Bang today.

This Is Why Betelgeuse (Probably) Isn’t About To Explode

“Even though it’s unlikely that Betelgeuse is about to explode, we must keep in mind that this is both a possibility and an inevitability. When that finally does occur, it will become the most widely-viewed astronomical event in human history, visible to everyone on Earth over the course of a year or more at a time where more humans exist on Earth than ever before. It’s going to happen eventually, but probably not for somewhere around 100,000 years.

While you should absolutely go out and enjoy this unprecedentedly dim sight, as Betelgeuse is only ~36% as bright as it was a year ago, you must keep in mind that its current brightness variations are due to processes in its outermost layers alone, and have nothing to do with its core. Betelgeuse might go supernova at any time, but if it does, its correlation with this recent dimming event will be due to pure coincidence. What happens in the core doesn’t make it to the surface fast enough to give us any real, meaningful clues.”

Betelgeuse has gotten fainter and fainter over the past few months, moving from its position as one of the 10 brightest stars in the sky all the way down to the mid-20s, barely a third of its original brightness. At the same time, images of its shape have shown it changing unevenly over the course of merely a year. Betelgeuse has never appeared this faint to anyone alive today, and speculation is running rampant that it might go supernova at any point. But that’s not what we’d responsibly conclude based on astronomy at all. 

It’s extremely unlikely to go supernova, and this dimming event isn’t related to anything happening (or not happening) in Betelgeuse’s core at all. Here’s what’s really going on.

Drew a crappy thermometer to make a point about 0th law of thermodynamics. They all bust out laughing.

Student 1: sir what kind of thermometer is that?

Student 2: the kind YOUR MOM USES!

Flaremageddon: How Satellite Mega-Constellations Could Create A New Natural Disaster

“If we fail to prepare, a “Flaremageddon” natural disaster scenario becomes easy to envision. Imagine that it’s 2025, and we have over 10,000 new mega-constellation satellites up there, with a series of sunspots appearing around the Sun’s equator. A magnetic reconnection event occurs, launching an X-class solar flare with a coronal mass ejection right at Earth. The magnetic field is oriented so that a geomagnetic storm occurs, knocking out some major electrical grids in the process.

But in space, a large fraction of satellites get bombarded by these energetic particles from the Sun, causing them to become non-responsive. 8 days later, the first collision occurs. While humanity scrambles to respond appropriately, the second collision occurs, and the chain reaction begins. By 2027, the International Space Station is abandoned, and the Hubble Space Telescope is destroyed. It’s an entirely avoidable disaster, but unless we get ready for it now, it may be too late when the critical moment arrives.”

When two satellites collide in orbit around Earth, it puts all the others at risk. The debris created can be catastrophic to anything it encounters, with the ultimate ‘nightmare scenario’ occurring if a single collision leads to a chain reaction. With mega-constellations of satellites presently being planned and launched, the number of satellites will increase by orders of magnitude, raising the risk of this event occurring. But unless plans are made now, an inevitable natural disaster may soon occur: a space weather event that knocks out the ability of artificial intelligence (or any manual operator) to control the satellites and avoid collisions.

A new natural disaster may be on the horizon in the very near future. Unless we take precautions now, it could be the end of humanity’s access to space for generations.

What Really Kept American Women From Going To Space For So Long?

“Indeed, the only astronaut qualification that Cobb lacked was that of a jet test pilot, which was an avenue closed to women at the time. Despite the fact that exceptions were made for male astronauts who lacked necessary qualifications, such as Deke Slayton and John Glenn, no women were given the opportunity to become astronauts until NASA Astronaut Group 8 was selected in 1978.

Cobb repeatedly sought opportunities throughout her later life to travel to space, including in 1998, where she mounted a failed campaign to convince NASA to send up not just John Glenn to study the effects of spaceflight on senior citizens, but a woman — herself — as well. Depending on who you are, your conclusion about who’s a hero, who’s a villain, and who was right or wrong will vary. But no matter what, Teitel’s Fighting For Space is a great read about the first attempt to put women in space, and the women who almost made it happen 20 years before it actually did.”

In the early days of the space race, it wasn’t just the original Mercury 7 who were considered as potential astronauts, but also a group of women pilots whose biological traits offered many advantages over the men. Yet a number of factors prevented them from getting the chance to compete and prove themselves; ultimately the first American woman wouldn’t go to space until 1983, and the first American woman wouldn’t pilot a spacecraft until 1995. However, there is a tremendous amount to be learned from the initial attempt, even if unsuccessful, to put American women in space.

I just read Amy Shira Teitel’s new book, Fighting For Space, and you should read it, too. Here are my thoughts, and why I think you’ll find it interesting, too.

These 22 Pictures Are The Perfect Farewell To NASA’s Spitzer Space Telescope

“On January 30, 2020, NASA’s Spitzer Space Telescope was retired after a 17 year mission. Along with Hubble, Compton, and Chandra, Spitzer was the final of NASA’s Great Observatories. Owing to its location above Earth’s atmosphere, its measurement capabilities were unique. Until James Webb launches, Spitzer remains humanity’s greatest mid-infrared observatory. These 22 images highlight its greatest achievements.”

What can you see, from space, with infrared eyes that you cannot see with optical, Hubble-like wavelengths? For the past 17 years, NASA’s Spitzer has answered those questions, revealing spectacular details about star-forming regions, nearby and distant galaxies, supernova remnants and planetary nebulae, and a whole host of other fascinating astrophysical phenomena.

From the deepest, darkest dust lanes in our galaxy to comets in our own Solar System to the ultra-distant Universe, Spitzer truly has been one of the “great” observatories in NASA’s entire history. Come take one last tour today.