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.
Ask Ethan: Could Gravitational Waves Ever Cause Damage On Earth?
“The gravitational waves detected on Earth by LIGO traveled great distances and were quite weak per unit volume of space by the time they arrived. If they originated much closer to Earth, they would be more energetic from our perspective. What would the effect of energetic gravitational waves created locally be on nearby objects. I’m thinking of binary ~30 solar mass black holes merging. Would the gravitational waves be noticeable? Could they cause damage?”
The first black hole-black hole merger we ever observed occurred some 1.3 billion light-years from Earth. It compressed the entire planet, at maximum amplitude, by about the width of a dozen protons, imparting just a tiny amount of energy (about 0.7 seconds worth of sunlight shining on Manhattan island) to the entire Earth in the process. But we were able to leverage that tiny effect to great effect with gravitational wave detectors such as LIGO, where we now have approximately 50 candidate detections under our collective belts. If these black holes were just 1 light-year away instead of 1.3 billion, they’d strike Earth with more energy than the Sun produces over about 3 minutes.
And yet, the damage would be absolutely negligible, unless two black holes were to merge somewhere within our own Solar System. Here’s the full story.
The Future Of NASA Astrophysics Depends On Undoing Trump’s FY2021 Budget Request
“NASA has always spent more than half of its budget on developing large missions; 2019 was the first time the Astrophysics Division’s numbers dropped below that figure. When a flagship mission overruns, it never eats the rest of the science program; it only can delay the next flagship. And flagships aren’t expensive because of mismanagement; they’re expensive because they’re ambitious, first-of-its-kind science.
Before any servicing missions at all, Hubble cost about $3 billion in late-1980s dollars. If it had started in 2007, the same time Webb started, it would have cost $8.3 billion in inflated dollars. Meanwhile, WFIRST is not having any of the problems that plagued Webb, and is coming in on-schedule and on-budget, with 100 times the field-of-view of Hubble and up to 1500 times faster for large surveys at the same depth. The future of scientific exploration is right at our fingertips, if only we’re bold enough to continuously invest in it.”
Earlier this week, the President’s office released their budget request for the 2021 fiscal year. Just as in every year prior, the administration has proposed terminating the flagship program at NASA Astrophysics by ending the federal funding for it. Flagship missions are arguably the most scientifically fruitful endeavor that NASA undertakes, and without it, we would never have had the Hubble Space Telescope or many other legendary observatories that have forever changed our view of the Universe.
We can have a bright scientific future, but even one year without this essential funding could bring generations of efforts all crashing down. Here’s what we need to do.
Don’t Believe These 5 Myths About The Big Bang
“1.) The Big Bang is the explosion that began our Universe. Every time we look out at a distant galaxy in the Universe and try to measure what its light is doing, we see the same pattern emerge: the farther away the galaxy is, the more significantly its light is systematically shifted to longer and longer wavelengths. This redshift that we observe for these objects follows a predictable pattern, with double the distance meaning that the light is shifted by twice as much.
Distant objects, therefore, appear to be receding away from us. Just as a police car speeding away from you will sound lower-pitched the faster it moves away from you, the greater we measure an object’s distance to be from us, the greater the measured redshift of its light will be. It makes a lot of sense, then, to think that the more distant objects are moving away from us at faster speeds, and that we could trace every galaxy we see today back to a single point in the past: an enormous explosion.”
The Big Bang is not an explosion, it doesn’t have a center point that we can trace the expansion back to, it never reached an infinitely hot-and-dense state, it doesn’t imply that the Universe began from a singularity, and it doesn’t take you back to a moment where space, time, and the laws of physics all spontaneously emerged. Do you believe any of these statements? Do you know why they’re not true?
Here’s the real physics behind what we know about our Universe’s origin, with the scientific evidence to back it all up!
Will Humanity Achieve Interstellar Travel And Find Alien Life?
“All of this, together, points to a picture where a spacecraft or even a crewed journey to the stars is technologically within our reach, and where the discovery of our first world beyond the solar system with possible life on it could occur in a decade or two. What was once solely in the realm of science-fiction is quickly becoming possible due to both technical and scientific advances and the thousands of scientists and engineers who work to apply these new technologies in practical ways.
On February 5 at 7 PM ET (4 PM PT), Dr. Bryan Gaensler, director of the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto, will be delivering a public lecture at Perimeter Institute on exactly this topic. Titled Warp Drive and Aliens: The Scientific Perspective, it’s available to watch from anywhere on Earth, and I’ll be following along with a live-blog in real time…”
For as long as we’ve been looking up at the stars, we’ve wondered whether it will ever be possible to travel to one of them, and to perhaps discover another planet where life has taken hold. What’s been a mere sci-fi dream for humanity for most of our history at last, with 21st century technology, has the possibility of becoming a reality.
Later today, Dr. Bryan Gaensler will be delivering a public lecture at Perimeter Institute that will be webcast in real-time all over the world, and you can follow along with my live-blog of his talk in real-time, too!
Ask Ethan: How Can We See 46.1 Billion Light-Years Away In A 13.8 Billion Year Old Universe?
“If the limit of what we could see in a 13.8 billion year old Universe were truly 13.8 billion light-years, it would be extraordinary evidence that both General Relativity was wrong and that objects could not move from one location to a more distant location in the Universe over time. The observational evidence overwhelming indicates that objects do move, that General Relativity is correct, and that the Universe is expanding and dominated by a mix of dark matter and dark energy.
When you take the full suite of what’s known into account, we discover a Universe that began with a hot Big Bang some 13.8 billion years ago, has been expanding ever since, and whose most distant light can come to us from an object presently located 46.1 billion light-years away. The space between ourselves and the distant, unbound objects we observe continues to expand at a rate of 6.5 light-years per year at the most distant cosmic frontier. As time goes on, the distant reaches of the Universe will further recede from our grasp.”
The fabric of space is expanding, and this is perhaps the most counterintuitive thing of all. Back in the earliest stages of the Big Bang, a point in space no farther away from us than the length of a city block could have emitted a photon, and it would take that photon a remarkable 13.8 billion years just to reach us. Moreover, that photon would journey for a total of 13.8 billion light-years before arriving at our eyes, and an object located at the exact same point in space where it was initially emitted from would now be 46.1 billion light-years away from us.
Why is this? Because that’s what the laws of General Relativity, coupled with our knowledge of what’s present in the Universe, demand of space and time. Come get the full story today!
How Far Is It To The Edge Of The Universe?
“If you define the edge of the Universe as the farthest object we could ever reach if we began our journey immediately, then our present limit is a mere distance of 18 billion light-years, encompassing just 6% of the volume of our observable Universe. If you define it as the limit of what we can observe a signal from — who we can see and who can see us — then the edge goes out to 46.1 billion light-years. But if you define it as the limits of the unobservable Universe, the only limit we have is that it’s at least 1,150 billion light-years in size, and it could be even larger.
This doesn’t necessarily mean that the Universe is infinite, though. It could be flat and still curve back on itself, with a donut-like shape known mathematically as a torus. As large and expansive as the observable Universe is, it’s still finite, with a finite amount of information to teach us. Beyond that, the ultimate cosmic truths still remain unknown to us.”
How far is it to the edge of the Universe? If you were to leave in a rocket ship today at the speed of light, what is the most distant object you’d be able to visit, and is that truly an edge? If you looked out at the most distant thing you could possibly observe, and the most distant location that could possibly observe us, how far would that be, and is that truly an edge? Or, would you consider the Universe beyond its observable limits, and wonder on the largest scales whose data exists only in our mind’s eye, whether there’s an edge at all?
Regardless of how you think about it, physics has answers, constraints, and limits for how far it truly is to the Universe’s edge. Find out how far it is today!
This Is How Galaxy Cluster Collisions Prove The Existence Of Dark Matter
“When two galaxy clusters collide — a cosmically rare but important event — its internal components behave differently. The intergalactic gas must collide, slow, and heat up, creating shocks and emitting X-rays. If there were no dark matter, this gas, comprising the majority of normal matter, should be the primary source of gravitational lensing. Instead, gravitational lensing maps indicate that most of the mass is displaced from the normal matter.”
Are you disappointed at how readily astronomers seem to accept the idea of dark matter? Does the notion that around 85% of the mass in our Universe isn’t in the form of matter we’re familiar with — stuff like protons, neutrons, and electrons — but instead is some new, undiscovered form of mass that doesn’t collide or interact with light or normal matter in any way? Astronomers only accept it because of the overwhelming observational evidence, and what it does (and doesn’t) indicate. In particular, colliding galaxy clusters tested dark matter against modified gravity directly, and there was a clear winner from the very first one we saw, confirmed over and over again with each new observation.
Come learn about the first empirical proof of dark matter, and why it should absolutely be considered the nail-in-the-coffin of modified gravity theories without dark matter.
This Is How We’d All Die Instantly If The Sun Suddenly Went Supernova
“It’s horrifying to think that an event as fascinating and destructive as a supernova, despite all the spectacular effects it produces, would kill anything nearby before a single perceptible signal arrived, but that’s absolutely the case with neutrinos. Produced in the core of a supernova and carrying away 99% of its energy, all life on an Earth-like would receive a lethal dose of neutrinos within 1/20th of a second as every other location on the planet. No amount of shielding, even from being on the opposite side of the planet from the supernova, would help at all.
Whenever any star goes supernova, neutrinos are the first signal that can be detected from them, but by the time they arrive, it’s already too late. Even with how rarely they interact, they’d sterilize their entire solar system before the light or matter from the blast ever arrived. At the moment of a supernova’s ignition, the fate of death is sealed by the stealthiest killer of all: the elusive neutrino.”
In reality, our Sun is in no danger of going supernova, particularly from core-collapse, as it doesn’t have enough mass to ever come close. But for stars that are massive enough, no matter where any living thing is in its vicinity, it’s doomed as soon as that detonation inside the core occurs. It won’t be the blast wave from the explosion that kills you, nor will it be the tremendous radiation that emerges. Instead, the silent-but-deadly killer that will cause your demise is the elusive neutrino, which behaves, to a supernova’s solar system, as a great cosmic sterilizer.
It’s counterintuitive that the least interactive particle in all the Universe would kill all life in a solar system before anything else even arrived, but it’s true. Come find out how we’d all go, in an instant, if the Sun suddenly went supernova.