In 1998, two teams of astronomers discovered that, instead of slowing down, the universe is expanding faster today than it was in earlier epochs
Adam Riess thought there must have been a mistake.
In late 1997, he was analyzing observations of exploding stars to help determine whether the universe would expand forever, or would someday reverse course and collapse in on itself. His observations seemed to show that not only would the universe continue to expand, but also that it was expanding faster as it got older — something that no one expected.
Riess, who is now an astronomer at Johns Hopkins, double-checked his figures, and found there was no mistake. Something was pushing down on the universe's gas pedal, making it expand faster. For want of a better name, that 'something' was identified as dark energy.
Riess was a member of one of two teams that made the same basic discovery. The other was headed by Saul Perlmutter of the University of California, Berkeley. Their discovery stunned scientists because it indicated that their understanding of the universe was far from complete — that some unknown force was counteracting gravity and pushing galaxies away from each other. Astronomers, physicists, and others continue to try to identify the cause of the accelerating universe.
"The universe is not slowing down enough to come to a halt, and in fact it's not slowing at all, but it's speeding up, and that was obviously the big surprise at the end of '97, when we saw these results." — Saul Perlmutter
Looking for Exploding Stars
Both teams were examining a class of exploding stars known as Type Ia supernovae. These stars are white dwarfs — the hot, dense, dead cores of stars that were once similar to the Sun — with close stellar companions. The white dwarf 'steals' hot gas from its companion. The gas piles up, forming a superhot layer atop the white dwarf. When the gas pushes the star past a critical mass, it sets off a runaway nuclear explosion that blasts the star to bits. For a while, the supernova can outshine an entire galaxy of normal stars, so it's easy to see these exploding stars even in distant galaxies.
The ability to see Type Ia supernovae far across the universe makes them good "standard candles" — a way to measure distances to other galaxies.
All Type Ia supernovae brighten and fade in a predictable way. Measuring how long it takes a supernova to brighten and then fade reveals its true brightness. By comparing a star's true brightness to how bright it looks in our sky, astronomers can find its distance.
One more step completes the picture. Astronomers measure how fast the star is moving away from Earth by measuring its redshift — a stretching of its light waves by the expansion of the universe itself.
Hubble Space Telescope images show supernovae (arrows) in three distant galaxies. [P. Garnavich (CfA)/High-z Supernova Search Team/NASA]
Pedal to the Metal
By putting together the distances and speeds of many supernovae, the two teams hoped to show how the expansion of the universe had changed over the eons.
Most astronomers expected one of two outcomes.
If the universe contained enough stars, gas, planets, and other matter, and this material were packed tightly enough, then gravity would slow the expansion and eventually reverse it. In that case, the universe would end with a Big Crunch — the opposite of the Big Bang in which it was born.
If, on the other hand, the universe contained less matter, then the universe would continue to expand forever, although the expansion would grow slower with time.
Riess was analyzing observations made by the High-z Supernova Search Team, while Perlmutter led the Supernova Cosmology Project. Both teams observed several supernovae over several years. They used small telescopes to look at large patches of sky at different times, then compared the pictures to see if a supernova had appeared in any of the galaxies in their field of view. When a supernova appeared, they used larger telescopes to study the explosions in detail. Improved technology yielded supernovae that were up to 9 billion light-years away, which is much farther than earlier searches.
Key Discoveries About the Expanding Universe
After collecting their data, Riess ran a computer program that calculated how much mass was required to account for how quickly the universe was slowing down. The computer's answer was a negative number — in other words, negative mass. There's no such thing as negative mass, though, so Riess basically flipped the answer over. He realized that the computer was telling him that the expansion of the universe wasn't slowing down, but instead was getting faster.
Perlmutter's team reached the same conclusion, and the teams published their findings in 1998. Science magazine named their discovery the 'Breakthrough of the Year' for 1998, and hundreds of other scientists jumped into the fray — beginning the effort to understand dark energy.Gelish soft gel tips how to? What does dark blue mean on a mood ring? why the settlers came ed helper wii usb helper how many games how to level craft skills swtor How to hide tv wires in wall? Destiny how to do tricks slr? who are the main participants in the scope definition? how to measure my inseam What does over under mean? How many senate votes needed to impeach president? What goes with beef tips? how do you know the difference between spotting and period mabinogi how to obtain tailoring skills keyword how you would advice your current employer to use encryptio which of the following is the best definition of a consumer price index? java ssv helper does what Tricks to help swallow liquids when you have dysphagia? how to improve tankless water heater what kind of mood is romeo in before the boys go to the party? what is mercutio’s advice? What does nwt mean on poshmark? What is the meaning of _? what is the definition of a contemporary issue what is the difference between isolation and quarantine what is the difference between broad match and phrase match when do federal covid unemployment benefits end what is the advice for engineering internship at gogle What are the best shoes for standing all day? How to use however? how t cells become helper or cytotoxic What does an insurance adjuster do? what is the difference between permutation and combination You can't teach an old dog new tricks why would you want a dog? We reap what we sow meaning? a man and woman team giving advice on how to master your mind how to improve wifi signal strength in laptop what benefits does lemon water have What is jet lag? what is elasticity definition what is reference material definition What is the meaning of intranet and extranet? what is undernutrition definition how to improve the perfomance of my s7 edge What is the meaning of vanish? how to measure your hand size nfl combine how to describe people who are good at giving advice what is the difference between doctor and physician which is correct looking for advise or advice How do i cast to my tv? yeah i got skills what are you gonna do about it What does ana mean? What number of college students are nondrinkers? Why do my finger tips turn greenish color? What does false imprisonment mean? How long to cook tater tots in air fryer? Photo editing when to use filters tips? how to give advice using should How to make eyelashes grow? What does ancillary mean? How to take a screen shot? How to do a cool paper tricks? what difference, at this point, does it make? What is the meaning of coons? what are the responsibilities of a factory helper How to send tips to jobs that a former coworker is a threat? Top tips on how to use excel? What time does shoe carnival close? advice on how to suicide What are the ranks in the army lowest to highest? Why do the tips of my elbows hurt? how to improve people management skills how to improve affordable housing What does hierarchy mean? How to use mod podge? Which comply foam tips are best? What does 999 mean juice? Tips on how to dip dance? how did sanitation improve for south africa where are helper t cells made and mature How to dispose of tv? what is the difference between hard money and soft money what is risk behaviors definition What is myalgia? what is the difference between adventure and survival in minecraft How long do k tips extensions last? what va benefits are available to me What does igy6 mean? how to get all skills to 100 in skyrim console commands how to start making money online without any skills how to use ambush skills gw2 What does eiffel tower meaning sexually? What is the meaning of informational text? how to measure for a sliding barn door how long do you get widows benefits which of the following is not one of hermans skills who won the skills competition 2021 How to play new westworld game tips and tricks? how can you improve your work performance interview question how to improve posture lying down what advice would you give a high school student What is polarized sunglasses? How to get rid of a hangover headache? how long does hamburger helper meat last Tops tricks when presenting a puchase agreement to a buyer? What does verbal mean? how to improve dribbling stamina in soccer What does differential diagnosis mean? How to pass college tips reddit? what is the difference between snyder cut justice league what advice does atticus give scout about understanding people How to prevent pregnancy? what is the definition of earth science? How to do amazing card tricks revealed? why are active listening skills important What does rio mean? what is the difference between vhs and vcr How can i catch tricks? What does snf mean?