# How fast is the universe expanding?

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• ZikZak
Lv 6

The universe is NOT expanding at the speed of light, as another ill-informed answerer claims. It's not expanding at any *speed* at all. The rate of expansion is a speed per distance--- the farther away an object is, the faster it recedes from us. The rate of expansion was very accurately measured by the WMAP experiment to be 71 kilometers per second, per Megaparsec.

In other words, a galaxy one Mpc away recedes at 71 km/s; a galaxy 2 Mpc away recedes at 142 km/s, etc.

• Anonymous

The expansion of the universe is a weird thing. It isn't that the galaxies are physically moving outward, it's that space itself is expanding. This means that although everything appears to be moving away from Earth, nothing is really moving. Because of this, you can't specify how fast the universe is expanding in something like miles per second.

Astronomers measure the expansion of the universe in kilometers per second per megaparsec. This is called the Hubble Constant, and its value is somewhere around 70 kilometers per second per megaparsecs. If an object is one megaparsec away (that's 3 million light-years, or 20 billion billion miles, or 30 billion billion kilometers), it's moving away at 70 kilometers per second, which is about 150,000 MPH. Things that are twice as far away move twice as fast, if you ignore the effects of gravity and dark energy.

You can also put this into terms of a rate of growth. Roughly speaking, the universe is growing in size by about 7 percent every billion years.

Note that there is still a fair amount of disagreement as to what the value of the Hubble Constant is exactly. Most astronomers adopt a number around 70, but there's a range of around 65-75 that people frequently use. Some years ago, there were two competing measurements out there -- one 50 and one 100. A handful of astronomers still prefer one of these older measurements.

There's no easy answer to your question because we have to talk about the *observable* universe and *the* universe.

*The* universe is not the same as the *observable* universe, mainly because science has discovered that in the first instant of the Big Bang the space of the universe expanded faster than the speed of light (..this is okay because it's space doing the FTL thing, not mass *in* that space..) This so-called expansion means that there are immense regions of *the* universe that we'll never be able to observe because those regions are moving away from us faster than the speed of light.

As for the *observable* universe, we've found that the farther away we look the faster the expansion of the *observable* universe will be. Right now we've determined that for every one-million parsecs (..equal to 3,261,688.071 light years..) farther away we look, the universe expands 70 km/sec faster. For example, if galaxy 'A' is 2-million parsecs from Earth, it will be receding from us at 140 km/sec. If Galaxy 'B' is 4-million parsecs away it will be receding at 280 km/sec

Source(s): KARAOKE is Japanese for "Tone Deaf"
• plainy
Lv 4
3 years ago

it particularly is dazzling for something that has mass to exceed the value of sunshine. that is not mass that's shifting however. in case you think of sci fi movies the place the deliver travels at some variety of warp rigidity - how do they get around the sunshine velocity barrier? by ability of warping the area-time continuum - folding it into yet another length so as that the area between 2 gadgets is decreased by ability of a given component. the upward push of the universe would not contain the actually circulate of rely via area (it particularly is constrained to the value of sunshine) yet particularly the substitute in distance itself, it particularly is to declare the "fabric" of area-time is being stretched. ok enable's help visualise this. Take a balloon and inflate it a splash, then positioned 2 dots on the balloon, then inflate the balloon. word the area between the two dots will advance devoid of the dots incredibly shifting, additionally the area between the dots will advance with the sq. of the upward push in radius of the balloon. desire this facilitates you to visualize the assumption of inflation.

The universe expands at the speed of light and it has been since one-thirty billionths of a second after it began.

The universe is a finite entity so it must have a maximum size

It likely has a maximum size.of about 6 billion light years in radius.

The universe could be much older than this but no bigger.

The universe can't be in a state of accelerated expansion,the farthest galaxies we can see expired long ago.

the universe is an incident that started in the past,will run it's course,go out of existence and never occur again.

• Anonymous
5 years ago

according to stephen hawking its the only known thing thats faster then light

• Anonymous

Nice thesis, Jerry but that's not the answer to the question asked.

Allah has mention about the expansion of the universe in Koran. But He didn't mention how fast it expends

Lv 4

who said 'the universe is expanding',instead itz the population thatz expanding.

Scientists still in the murk about 'dark energy'

Updated 12h 15m ago | Comments 4 | Recommend 2 E-mail | Save | Print | Subscribe to stories like this

THREE DESTINIES

Three theories on what could happen as dark energy expands the universe:

1. Accelerated expansion

If dark energy is a constant, expansion will continue at an accelerated pace. In 30 billion years, we will see only a handful of galaxies -- all the others will have sped out of sight.

2. The Big Rip

Strengthening dark energy will force an expansion in about 30 billion years so violent that every structure -- from clusters of galaxies to atoms -- will be ripped apart.

3. The Big Crunch

Dark energy will fade, and gravity will cause the universe to implode.

Sources: NASA; Ann Feild, Space Telescope Science Institute

By Ron Cowen, Special for USA TODAY

Nearly a decade after scientists discovered that a mysterious force is pushing the universe to expand at an ever-faster rate, they still don't understand how that is happening.

University of Chicago cosmologist Michael Turner calls the acceleration "the most profound mystery in all of science." It was Turner who coined the term "dark energy" for the unknown substance that provides this cosmic push. Studies have shown that it comprises 74% of all the mass and energy of the universe.

Scientists say that if they can understand dark energy, they may learn the fate of the universe — whether it will keep on expanding, tear itself apart or implode cataclysmically billions of years from now.

Science writers took part in a workshop last month at the Space Telescope Science Institute in Baltimore to focus on the question of why gravity, on the largest scales, has switched roles — pushing out instead of holding in.

NASA plans to explore the question in a big way as well. The National Research Council recommended in early September that a dark-energy probe be the first spacecraft NASA launches in its delayed "Beyond Einstein" series of missions designed to explore the formation of the universe and some of its most unique features.

FIND MORE STORIES IN: Space Telescope | Physics | Big Bang | Michael Turner

Jointly sponsored by the Department of Energy, the series has three proposed missions, one of which would be selected and launched around 2015.

"It's not very often that theorists face a situation in which they need to explain something that is 74% of everything there is and they don't have a clue," says Mario Livio, theorist for the space telescope institute.

Coming to the opposite conclusion

Astronomer Adam Riess remembers the moment he realized that instead of pulling galaxies together, gravity was pushing them apart.

A decade ago, Riess was a 26-year-old postdoctoral researcher at the University of California-Berkeley, part of a team using the light from distant supernovae to study how rapidly the universe has been expanding over the past several billion years.

Researchers had known since the 1920s that the universe has been expanding in all directions but had assumed that the expansion was slowing, weighed down by the combined tug of all the galaxies.

But when Riess examined the supernova data in the fall of 1997, he found just the opposite: Cosmic expansion was speeding up. Something was undermining gravity's pull, turning it into a push and inflating the universe like a balloon. "I still recall feeling very excited — excited that it was true and also very anxious … because most things you discover in science are wrong, and they have a half-life of about five minutes."

But this time, the finding didn't fizzle. Instead, a rival team studying supernovae, led by Saul Perlmutter of the University of California's Lawrence Berkeley National Laboratory, had arrived at the same conclusion.

The most compelling evidence of dark energy relies on some of the most brilliant objects in the cosmos. Type 1a supernovae are stars that have blown themselves to smithereens and are bright enough to be seen in galaxies several billion light-years from Earth.

Like light bulbs of similar wattage, these supernovae all have about the same intrinsic brightness. This enables astronomers to calculate the distance to each eruption by observing how dim it appears on the sky. In addition, astronomers also determine how fast the host galaxy of each supernova is speeding away from Earth.

By combining this information, scientists find that the 13.7-billion-year-old universe began revving up its rate of expansion about 5 billion years ago.

Over the past 10 years, other studies have reinforced the dark-energy picture, Turner notes. These include images of the microwave glow left over from the universe-forming Big Bang and studies of X-rays that bathe distant clusters of galaxies.

"Now the evidence is rock-solid that the universe is speeding up," Turner says. "We live in this kooky universe."

'Big Rip' or 'Big Crunch'?

Dark energy presents a tremendous opportunity for physicists, in much the same way that the mysteries of the subatomic world did in the past century, Turner and others say.

In fact, dark energy may be tied to the subatomic world. Studies so far hint that dark energy might be sprinkled evenly throughout space. According to quantum mechanics, the laws that govern the motion and behavior of atomic particles such as electrons and protons, empty space isn't really empty. It seethes with pairs of particles and negatively charged antiparticles that constantly pop in and out of existence.

That activity imbues the nothingness of space with energy. And that energy could be just the hidden culprit behind dark energy.

So what are the possible fates awaiting the universe?

If dark energy has a constant density, as hinted by the supernova studies, the universe would continue to expand at an accelerated rate. Galaxies would be separated by such great distances and flee from one another at such high speeds that in 30 billion years, Turner says, residents of our own Milky Way would look out on a lonely sky. Only six other galaxies would be visible, compared with the billions seen today.

If dark energy becomes more powerful with time, its cosmic push would eventually become a cosmic killer. In 30 billion years, the runaway expansion would tear asunder every galaxy, star, planet, molecule and atom in what theorists call the "Big Rip." If, however, dark energy were to fade away, gravity's tug eventually would take back the reins. The universe would collapse in a "Big Crunch."

Now, scientists are designing new experiments to elucidate the properties of dark energy. The proposed space missions would variously hunt for several thousand supernovae, record the positions of 100 million galaxies and scour the heavens to study the image-distorting properties of gravity. Scientists acknowledge that there's a chance the missions could discover there's another reason altogether for the universe's accelerated expansion.

•The Supernova/Acceleration Probe would study the expansion history of the universe by recording 2,000 type 1a supernovae a year, using a mirror slightly bigger than that of the Hubble Space Telescope and the biggest camera ever launched into space.

•The Advanced Dark Energy Physics Telescope would use the echoes of primordial sound waves to examine cosmic expansion.

•The Dark Energy Space Telescope would be used to detect more than 3,000 type 1a supernovae over two years. It would then survey the sky to determine how the distribution of galaxies has evolved since the Big Bang.

The estimated \$1 billion price tag for these projects comes with no guarantee, but Turner says he's optimistic that in 10 years, space and ground-based telescopes will crack the mystery. "This puzzle seems to be (related) to a number of other puzzles. It's the nexus," he says. "We can't understand the universe until we discover what dark energy is."

Posted 12h 30m ago

Updated 12h 15m ago

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