Here’s the deal — the universe is expanding. Not only that, but it’s expanding faster and faster due to the presence of a mysterious substance scientists have named “dark energy.”
But before we get to dark energy, let’s first talk a bit about the expanding cosmos. It started with the big bang — when the universe started expanding from a hot, dense state about 13.8 billion years ago. Our universe has been getting bigger and bigger ever since. Nearly every galaxy we look at is zipping away from us, caught up in that expansion!
The expansion, though, is even weirder than you might imagine. Things aren’t actually moving away from each other. Instead, the space between them is getting larger.
Imagine that you and a friend were standing next to each other. Just standing there, but the floor between you was growing. You two aren’t technically moving, but you see each other moving away. That’s what’s happening with the galaxies (and everything else) in our cosmos … in ALL directions!
Astronomers expected the expansion to slow down over time. Why? In a word: gravity. Anything that has mass or energy has gravity, and gravity tries to pull stuff together. Plus, it works over the longest distances. Even you, reading this, exert a gravitational tug on the farthest galaxy in the universe! It’s a tiny tug, but a tug nonetheless.
As the space between galaxies grows, gravity is trying to tug the galaxies back together — which should slow down the expansion. So, if we measure the distance of faraway galaxies over time, we should be able to detect if the universe’s growth rate slows down.
But in 1998, a group of astronomers measured the distance and velocity of a number of galaxies using bright, exploding stars as their “yardstick.” They found out that the expansion was getting faster.
Not slowing down.
Speeding up.
⬆️ This graphic illustrates the history of our expanding universe. We do see some slowing down of the expansion (the uphill part of the graph, where the roller coaster is slowing down). However, at some point, dark energy overtakes gravity and the expansion speeds up (the downhill on the graph). It’s like our universe is on a giant roller coaster ride, but we’re not sure how steep the hill is!
Other researchers also started looking for signs of accelerated expansion. And they found it — everywhere. They saw it when they looked at individual stars. They saw it in large scale structures of the universe, like galaxies, galaxy groups and clusters. They even saw it when they looked at the cosmic microwave background (that’s what’s in this image), a “baby picture” of the universe from just a few hundred thousand years after the big bang.
If you thought the roller coaster was wild, hold on because things are about to get really weird.
Clearly, we were missing something. Gravity wasn’t the biggest influence on matter and energy across the largest scales of the universe. Something else was. The name we’ve given to that “something else” is dark energy.
We don’t know exactly what dark energy is, and we’ve never detected it directly. But we do know there is a lot of it. A lot. If you summed up all the “stuff” in the universe — normal matter (the stuff we can touch or observe directly), dark matter, and dark energy — dark energy would make up more than two-thirds of what is out there.
That’s a lot of our universe to have escaped detection!
Researchers have come up with a few dark energy possibilities. Einstein discarded an idea from his theory of general relativity about an intrinsic property of space itself. It could be that this bit of theory got dark energy right after all. Perhaps instead there is some strange kind of energy-fluid that fills space. It could even be that we need to tweak Einstein’s theory of gravity to work at the largest scales.
We’ll have to stay tuned as researchers work this out.
Our Wide Field Infrared Survey Telescope (WFIRST) — planned to launch in the mid-2020s — will be helping with the task of unraveling the mystery of dark energy. WFIRST will map the structure and distribution of matter throughout the cosmos and across cosmic time. It will also map the universe’s expansion and study galaxies from when the universe was a wee 2-billion-year-old up to today. Using these new data, researchers will learn more than we’ve ever known about dark energy. Perhaps even cracking open the case!
You can find out more about the history of dark energy and how a number of different pieces of observational evidence led to its discovery in our Cosmic Times series. And keep an eye on WFIRST to see how this mystery unfolds.
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com
Observations of Earth, Soyuz, moon and Space Shuttle Endeavor made from the International Space Station.
source: images.nasa.gov
Follow @psych2go for more!
“Einstein’s equation is amazingly elegant. But is its simplicity real or only apparent? Does E = mc² derive directly from an inherent equivalence between any mass’s energy and the square of the speed of light (which seems like a marvelous coincidence)? Or does the equation only exist because its terms are defined in a (conveniently) particular way?”
Quite arguably, Einstein’s E = mc² is the most famous equation in the entire world. And yet, it isn’t obvious why it had to be this way! Could there have been some other speed besides the speed of light that converts mass to energy? Could there have been a multiplicative constant out in front besides “1” to give the right answer? No, no there couldn’t. If energy and momentum are conserved, and particles have the energies and momenta that they do, there’s no other option.
Come learn, at last, why E = mc², and why simply no other alternative will do.
“9.) The solstices are neither the hottest nor coldest days of the year. This one is actually very specific to Earth: the hottest times of the year typically correspond to approximately 6 weeks after the summer solstice, and approximately 6 weeks after the winter solstice. Other planets don’t have this same phenomenon for one very important reason: they don’t have the majority of their surfaces covered in liquid water.
The oceans themselves, being composed of large quantities of water and containing approximately 1,000 times the mass of Earth’s atmospheres, contain a tremendous amount of heat, and are slow to change their temperatures. We might receive more (or less) energy from the Sun on the summer (or winter) solstices, but the oceans require time to heat up or cool down. Global average temperature extremes, therefore, usually occur in early August and February, rather than at the June and December solstices.”
The solstice, Latin for the Sun standing still in the sky, occurs whenever the Earth’s axial tilt reaches a maximum relative to the Earth’s orbital plane around the Sun. With a tilt of 23.5 degrees, but a tilt that’s independent of our elliptical orbit around the Sun, many surprising and counterintuitive facts arise.
Want to know as many of them as possible? Come get this remarkable and fascinating list of educational facts on this year’s solstice: June 21, 2019!
“A dolphin may look like a fish, but it’s really a mammal. Similarly, the composition of an object is not the only factor in classifying it: its evolutionary history is inextricably related to its properties. Scientists will likely continue to argue over how to best classify all of these worlds, but it’s not just astronomers and planetary scientists who have a stake in this. In the quest to make organizational sense of the Universe, we have to confront it with the full suite of our knowledge.
Although many will disagree, moons, asteroids, Kuiper belt and Oort cloud objects are fascinating objects just as worthy of study as modern-day planets are. They may even be better candidates for life than many of the true planets are. But each object’s properties are inextricably related to the entirety of its formation history. When we try to classify the full suite of what we’re finding, we must not be misled by appearances alone.”
You’ve heard about the IAU’s definition, where in order to be a planet, you must pull yourself into hydrostatic equilibrium, orbit the Sun and nothing else, and gravitationally clear your orbit. You’ve also heard about the controversial new definition from geophysical/planetary science arguments, that planets should be based on their ability to pull themselves into a spheroidal shape alone.
Well, what about a third way: defining planets (and a whole classification scheme) based on astrophysical concerns alone? It’s time to start thinking about it!
On this day 50 years ago, human beings embarked on a journey to set foot on another world for the very first time.
At 9:32 a.m. EDT, millions watched as Apollo astronauts Neil Armstrong, Buzz Aldrin and Michael Collins lifted off from Launch Pad 39A at the Kennedy Space Center in Cape Canaveral, Florida, flying high on the most powerful rocket ever built: the mighty Saturn V.
As we prepare to return humans to the lunar surface with our Artemis program, we’re planning to make history again with a similarly unprecedented rocket, the Space Launch System (SLS). The SLS will be our first exploration-class vehicle since the Saturn V took American astronauts to the Moon a decade ago. With its superior lift capability, the SLS will expand our reach into the solar system, allowing astronauts aboard our Orion spacecraft to explore multiple, deep-space destinations including near-Earth asteroids, the Moon and ultimately Mars.
So, how does the Saturn V measure up half a century later? Let’s take a look.
Every human who has ever stepped foot on the Moon made it there on a Saturn V rocket. The Saturn rockets were the driving force behind our Apollo program that was designed to land humans on the Moon and return them safely back to Earth.
Developed at our Marshall Space Flight Center in the 1960s, the Saturn V rocket (V for the Roman numeral “5”) launched for the first time uncrewed during the Apollo 4 mission on November 9, 1967. One year later, it lifted off for its first crewed mission during Apollo 8. On this mission, astronauts orbited the Moon but did not land. Then, on July 16, 1969, the Apollo 11 mission was the first Saturn V flight to land astronauts on the Moon. In total, this powerful rocket completed 13 successful missions, landing humans on the lunar surface six times before lifting off for the last time in 1973.
Just as the Saturn V was the rocket of the Apollo generation, the Space Launch System will be the driving force behind a new era of spaceflight: the Artemis generation.
During our Artemis missions, SLS will take humanity farther than ever before. It is the vehicle that will return our astronauts to the Moon by 2024, transporting the first woman and the next man to a destination never before explored – the lunar South Pole. Over time, the rocket will evolve into increasingly more powerful configurations to provide the foundation for human exploration beyond Earth’s orbit to deep space destinations, including Mars.
SLS will take flight for the first time during Artemis 1 where it will travel 280,000 miles from Earth – farther into deep space than any spacecraft built for humans has ever ventured.
The Saturn V was big.
In fact, the Vehicle Assembly Building at Kennedy Space Center is one of the largest buildings in the world by volume and was built specifically for assembling the massive rocket. At a height of 363 feet, the Saturn V rocket was about the size of a 36-story building and 60 feet taller than the Statue of Liberty!
Measured at just 41 feet shy of the Saturn V, the initial SLS rocket will stand at a height of 322 feet. Because this rocket will evolve into heavier lift capacities to facilitate crew and cargo missions beyond Earth’s orbit, its size will evolve as well. When the SLS reaches its maximum lift capability, it will stand at a height of 384 feet, making it the tallest rocket in the world.
For the 1960s, the Saturn V rocket was a beast – to say the least.
Fully fueled for liftoff, the Saturn V weighed 6.2 million pounds and generated 7.6 million pounds of thrust at launch. That is more power than 85 Hoover Dams! This thrust came from five F-1 engines that made up the rocket’s first stage. With this lift capability, the Saturn V had the ability to send 130 tons (about 10 school buses) into low-Earth orbit and about 50 tons (about 4 school buses) to the Moon.
Photo of SLS rocket booster test
Unlike the Saturn V, our SLS rocket will evolve over time into increasingly more powerful versions of itself to accommodate missions to the Moon and then beyond to Mars.
The first SLS vehicle, called Block 1, will weigh 5.75 million pounds and produce 8.8 million pounds of thrust at time of launch. That’s 15 percent more than the Saturn V produced during liftoff! It will also send more than 26 tons beyond the Moon. Powered by a pair of five-segment boosters and four RS-25 engines, the rocket will reach the period of greatest atmospheric force within 90 seconds!
Following Block 1, the SLS will evolve five more times to reach its final stage, Block 2 Cargo. At this stage, the rocket will provide 11.9 million pounds of thrust and will be the workhorse vehicle for sending cargo to the Moon, Mars and other deep space destinations. SLS Block 2 will be designed to lift more than 45 tons to deep space. With its unprecedented power and capabilities, SLS is the only rocket that can send our Orion spacecraft, astronauts and large cargo to the Moon on a single mission.
The Saturn V was designed as a multi-stage system rocket, with three core stages. When one system ran out of fuel, it separated from the spacecraft and the next stage took over. The first stage, which was the most powerful, lifted the rocket off of Earth’s surface to an altitude of 68 kilometers (42 miles). This took only 2 minutes and 47 seconds! The first stage separated, allowing the second stage to fire and carry the rest of the stack almost into orbit. The third stage placed the Apollo spacecraft and service module into Earth orbit and pushed it toward the Moon. After the first two stages separated, they fell into the ocean for recovery. The third stage either stayed in space or crashed into the Moon.
Much like the Saturn V, our Space Launch System is also a multi-stage rocket. Its three stages (the solid rocket boosters, core stage and upper stage) will each take turns thrusting the spacecraft on its trajectory and separating after each individual stage has exhausted its fuel. In later, more powerful versions of the SLS, the third stage will carry both the Orion crew module and a deep space habitat module.
Just as the Saturn V and Apollo era signified a new age of exploration and technological advancements, the Space Launch System and Artemis missions will bring the United States into a new age of space travel and scientific discovery.
Join us in celebrating the 50th anniversary of the Apollo 11 Moon landing and hear about our future plans to go forward to the Moon and on to Mars by tuning in to a special two-hour live NASA Television broadcast at 1 p.m. ET on Friday, July 19. Watch the program at www.nasa.gov/live.
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.
"If it weren’t for this rare transition, from higher energy spherical orbitals to lower energy spherical orbitals, our Universe would look incredibly different in detail. We would have different numbers and magnitudes of acoustic peaks in the cosmic microwave background, and hence a different set of seed fluctuations for our Universe to build its large-scale structure out of. The ionization history of our Universe would be different; it would take longer for the first stars to form; and the light from the leftover glow of the Big Bang would only take us back to 790,000 years after the Big Bang, rather than the 380,000 years we get today.
In a very real sense, there are a myriad of ways that our view into the distant Universe — to the farthest reaches of deep space where we detect the earliest signals arising after the Big Bang — that would be fundamentally less powerful if not for this one quantum mechanical transition. If we want to understand how the Universe came to be the way it is today, even on cosmic scales, it’s remarkable how subtly dependent the outcomes are on the subatomic rules of quantum physics. Without it, the sights we see looking back across space and time would be far less rich and spectacular."
What gives the Universe the properties we see today? Is it gravity, working on the largest of cosmic scales? It plays a role, but perhaps ironically, the subatomic physics that governs electron transitions within atoms is maybe even more important.
This is how quantum physics allows us to see as far out in space and as far back in time as we can. Without it, our Universe would be a very different place.
Saturn is so beautiful that astronomers cannot resist using the Hubble Space Telescope to take yearly snapshots of the ringed world when it is at its closest distance to Earth. 😍
These images, however, are more than just beauty shots. They reveal exquisite details of the planet as a part of the Outer Planets Atmospheres Legacy project to help scientists understand the atmospheric dynamics of our solar system’s gas giants.
This year’s Hubble offering, for example, shows that a large storm visible in the 2018 Hubble image in the north polar region has vanished. Also, the mysterious six-sided pattern – called the “hexagon” – still exists on the north pole. Caused by a high-speed jet stream, the hexagon was first discovered in 1981 by our Voyager 1 spacecraft.
Saturn’s signature rings are still as stunning as ever. The image reveals that the ring system is tilted toward Earth, giving viewers a magnificent look at the bright, icy structure.
Image Credit: NASA, ESA, A. Simon (GSFC), M.H. Wong (University of California, Berkeley) and the OPAL Team
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com
Psalm 19-1-4
On #WorldTeachersDay, we are recognizing our two current astronauts who are former classroom teachers, Joe Acaba and Ricky Arnold, as well as honoring teachers everywhere. What better way to celebrate than by learning from teachers who are literally out-of-this-world!
During the past Year of Education on Station, astronauts connected with more than 175,000 students and 40,000 teachers during live Q & A sessions.
Let’s take a look at some of the questions those students asked:
Taking a look at our home planet from the International Space Station is one of the most fascinating things to see! The views and vistas are unforgettable, and you want to take everyone you know to the Cupola (window) to experience this. Want to see what the view is like? Check out earthkam to learn more.
There are several experiments that take place on a continuous basis aboard the orbiting laboratory - anything from combustion to life sciences to horticulture. Several organizations around the world have had the opportunity to test their experiments 250 miles off the surface of the Earth.
If you are a good listener and follower, you can be successful on the space station. As you work with your team, you can rely on each other’s strengths to achieve a common goal. Each astronaut needs to have expeditionary skills to be successful. Check out some of those skills here.
Nothing excites Serena Auñón-Chancellor more than seeing a living, green plant on the International Space Station. She can’t wait to use some of the lettuce harvest to top her next burger! Learn more about the plants that Serena sees on station here.
While aboard the International Space Station, taste buds may not react the same way as they do on earth but the astronauts have access to a variety of snacks and meals. They have also grown 12 variants of lettuce that they have had the opportunity to taste.
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.