universe

Solar Activity Heats Up

August 28 saw a major solar flare erupting from a complex sunspot group crossing the Sun's southern hemisphere. The intensity of the eruption placed it in the most powerful "X" category. The flare was accompanied by a coronal mass ejection (CME) which was clocked at 600 km/hr as it headed past the Earth. This CME passed south of Earth's orbital plane and did not cause any major effects here. However, CMEs that collide directly with the Earth can excite geomagnetic storms, which have been linked to satellite communication failures. In extreme cases, such storms can induce electric currents in the earth and oceans that can damage electric power transmission equipment. Scientists expect to see solar flare-ups daily during the solar max, which is expected in mid-2000.

Leaking Earth Could run dry

Researchers from the Tokyo Institute of Technology say that Earth could be dry and barren within a billion years because the oceans are draining into the planet's interior. They have calculated that about 1.12 billion tonnes of water leaks into the Earth each year. Although a lot of water also moves in the other direction, not enough comes to the surface to balance what is lost. The scientists believe that eventually all of it will disappear. They predict that the Earth's surface will look a lot like the surface of the planet Mars where a similar process seems to have taken place. This research was published in the New Scientist magazine. Mir drifts free

Russian space station Mir has gone into "free drift" mode as control passes to a new onboard computer. The free flight is necessary to reduce power consumption so that Mir can survive for months in space before a possible return by cosmonauts. The last crew left on August 27, just 10 days before Mir would have celebrated 10 years of continuous crewing. The new computer keeps the solar panels pointed at the Sun so Mir's batteries remain charged. Russia is expected to make a decision late this year or early next on whether Mir will remain in orbit. The station costs about $250 million a year to operate and while this is not too high in space terms, Russia just doesn't have the money.

Shaking Earth

The centuries-old mystery of why the Earth appears to wobble has been solved. Every 1.2 years, the planet appears to move about its axis by about 20 ft at the North Pole, but since discovering the so-called Chandler Wobble in 1891, scientists had been unable to explain it. Now NASA believes that the cause lies in the Earth's oceans. Fluctuating pressure of water on the ocean bed caused by temperature, salinity and current changes - forces the Earth to move slightly on its axis. Atmospheric fluctuations add to the wobble. The findings were made by analyzing data from the International Earth Rotation Service, set up in Paris in 1988.

Moon Magic

The Moon has always been an object of fantasy as well as research but we still don't know exactly how the Earth got its moon.

According to the 'giant impact theory', proposed in the 1970s, the moon was formed after the Earth was hit by a huge object, as big as Mars.

Using the new model, researchers at the Southwest Research Institute and the University of California at Santa Cruz, created high-resolution simulations to show that an oblique impact by an object with 10 per cent of the mass of Earth could have ejected sufficient iron free material into Earth's orbit to eventually coalesce into the moon, while also leaving the Earth with its present mass and correct initial rotation rate.

The simulation also implies that the moon formed near the very end of Earth's formation, some 4.5 billion years ago. The moon is believed to have played an important role in making the Earth habitable because of the stabilizing effect it had on the tilt of Earth's rotation.

New Solar System Is Like Ours

After 15 years of searching, astronomers say they have found an alien planetary system that reminds them a lot of home. This is the first time planet hunters have detected what they believe is a Jupiter-like gas ball orbiting a star much like our Sun, at a distance that allows for the possibility of an unseen Earth-type planet orbiting in between.

In the last decade and a half, scientists have found more than 90 so-called extra-solar planets around stars outside our solar system. But none of these earlier discoveries has held the same potential to answer an essential question: Might there be other Earths in the universe?

"We have a (planetary) system that is maybe not a sibling of the solar system… it might be more accurately classified as a first cousin," Paul Butler of the Carnegie Institution said on Thursday.

Butler and fellow planet-hunter Geoffrey Marcy of the University of California-Berkeley noted that the newly discovered Jupiter-type planet is the third thought to orbit 55 Cancri, a star in the constellation Cancer that can be seen without telescopes or even binoculars. It is about as old – five billion years or so – and about the same size as our Sun. Aside from it known planets, the new planetary system has a tantalizing gap between the new Jovian discovery and two other big gas planets orbiting very close to the star, Marcy said.

There’s a huge region centered at about Earth-Sun distance, and in that gap… an Earth-mass planet could exist … and such a planet would be stable, " he said. "It could persist there for billions of years, so it’s conceivable that this system has rocky planets like Mars, Venus or Earth and we simply can’t detect them," Marcy said.

Heavy Traffic Heads for Mars

American space agency NASA has outlined ambitious, long-term plans to explore the planet Mars. It says six major missions will take place in little more than 10 years, with Italy and France also participating. At an annual cost estimated at $400 million to $450 million a year for the next five years, the agency will dispatch a combination of orbiting spacecraft and landers to the Red Planet. Then, after 2010, the agency will undertake a mission to bring back samples from Mars. In 1999, NASA lost two Martian missions : the Mars Polar Lander and the Mars Climate Orbiter. The failures were a huge blow and prompted a major review of the way NASA carries through its space operations. The campaign to explore Mars is unparalleled in the history of space exploration. It’s meant to be a robust, flexible, long-term programme that will give the highest chances for success. The new strategy is aimed to answer questions about Mars’ mineralogy, geology and climate history. The idea is to ‘follow the water’ so we may know the answers to far-reaching questions about the red planet humans have asked over the generations: Did life ever arise there, and does life exist there now ?"

Astronomers spot winking baby star

A Sun-like star just out of infancy has winked at astronomers, indicating its eclipse by cosmic dust and rocks, the stuff of which planets like Earth could possibly form, scientists reported on Wednesday.

The star, located in the Unicorn constellation about 2,400 light years from Earth, disappeared from view for regular periods of about 48 days over the past six years. Its disappearance suggested an eclipse, but not a typical one caused by an intervening planet, star or moon.

Only a collection of smaller objects, like dust and rocks, could cause the long eclipse the astronomers saw. Known as KH 15D, the star is only about 3 million years old, a prime age for monitoring by astronomers interested in our solar system's planet-forming past.

"We've monitored thousands of these stars over the years and this is the only that behaves this way," said astronomer William Herbst of Wesleyan University in Connecticut. "Essentially the star winks at us."

The dust that caused the wink is different from the fine interstellar dust that is distributed throughout the cosmos. Herbst said. Its particles are bigger, indicating that it is clumping into what astronomers call a protoplanetary disk - the disk from which planets can form.

"Is there a mass in here that is somehow sculpting the obscuring clouds so that it's producing these rings of material which then circle around the star and alternately block the object? We think that's very possible," Herbst said. There could be two blobs circling the star, or just one, but there is no confirmation as yet of exactly what could be causing this kind of disk to form, said Herbst's colleague Catrina Hamilton.

At just 3 million years old, KH 15D is a cosmic toddler barely out of infancy. By contrast, our solar system is thought to be about 4.5 billion years old. However, some astronomers believe the planets may have begun forming when the Sun was a few million years old.

The disk is forming quite close to the star, closer than the planet Mercury is to the Sun. "The star is ... like the Sun was when it was 3 million years old, so the processes that are going on in this inner disk region, where terrestrial planets would be forming - could be analogous to what was going on with the formation of Earth," Herbst said.

universe

Solar Activity Heats Up

August 28 saw a major solar flare erupting from a complex sunspot group crossing the Sun's southern hemisphere. The intensity of the eruption placed it in the most powerful "X" category. The flare was accompanied by a coronal mass ejection (CME) which was clocked at 600 km/hr as it headed past the Earth. This CME passed south of Earth's orbital plane and did not cause any major effects here. However, CMEs that collide directly with the Earth can excite geomagnetic storms, which have been linked to satellite communication failures. In extreme cases, such storms can induce electric currents in the earth and oceans that can damage electric power transmission equipment. Scientists expect to see solar flare-ups daily during the solar max, which is expected in mid-2000.

Leaking Earth Could run dry

Researchers from the Tokyo Institute of Technology say that Earth could be dry and barren within a billion years because the oceans are draining into the planet's interior. They have calculated that about 1.12 billion tonnes of water leaks into the Earth each year. Although a lot of water also moves in the other direction, not enough comes to the surface to balance what is lost. The scientists believe that eventually all of it will disappear. They predict that the Earth's surface will look a lot like the surface of the planet Mars where a similar process seems to have taken place. This research was published in the New Scientist magazine. Mir drifts free

Russian space station Mir has gone into "free drift" mode as control passes to a new onboard computer. The free flight is necessary to reduce power consumption so that Mir can survive for months in space before a possible return by cosmonauts. The last crew left on August 27, just 10 days before Mir would have celebrated 10 years of continuous crewing. The new computer keeps the solar panels pointed at the Sun so Mir's batteries remain charged. Russia is expected to make a decision late this year or early next on whether Mir will remain in orbit. The station costs about $250 million a year to operate and while this is not too high in space terms, Russia just doesn't have the money.

Shaking Earth

The centuries-old mystery of why the Earth appears to wobble has been solved. Every 1.2 years, the planet appears to move about its axis by about 20 ft at the North Pole, but since discovering the so-called Chandler Wobble in 1891, scientists had been unable to explain it. Now NASA believes that the cause lies in the Earth's oceans. Fluctuating pressure of water on the ocean bed caused by temperature, salinity and current changes - forces the Earth to move slightly on its axis. Atmospheric fluctuations add to the wobble. The findings were made by analyzing data from the International Earth Rotation Service, set up in Paris in 1988.

Moon Magic

The Moon has always been an object of fantasy as well as research but we still don't know exactly how the Earth got its moon.

According to the 'giant impact theory', proposed in the 1970s, the moon was formed after the Earth was hit by a huge object, as big as Mars.

Using the new model, researchers at the Southwest Research Institute and the University of California at Santa Cruz, created high-resolution simulations to show that an oblique impact by an object with 10 per cent of the mass of Earth could have ejected sufficient iron free material into Earth's orbit to eventually coalesce into the moon, while also leaving the Earth with its present mass and correct initial rotation rate.

The simulation also implies that the moon formed near the very end of Earth's formation, some 4.5 billion years ago. The moon is believed to have played an important role in making the Earth habitable because of the stabilizing effect it had on the tilt of Earth's rotation.

New Solar System Is Like Ours

After 15 years of searching, astronomers say they have found an alien planetary system that reminds them a lot of home. This is the first time planet hunters have detected what they believe is a Jupiter-like gas ball orbiting a star much like our Sun, at a distance that allows for the possibility of an unseen Earth-type planet orbiting in between.

In the last decade and a half, scientists have found more than 90 so-called extra-solar planets around stars outside our solar system. But none of these earlier discoveries has held the same potential to answer an essential question: Might there be other Earths in the universe?

"We have a (planetary) system that is maybe not a sibling of the solar system… it might be more accurately classified as a first cousin," Paul Butler of the Carnegie Institution said on Thursday.

Butler and fellow planet-hunter Geoffrey Marcy of the University of California-Berkeley noted that the newly discovered Jupiter-type planet is the third thought to orbit 55 Cancri, a star in the constellation Cancer that can be seen without telescopes or even binoculars. It is about as old – five billion years or so – and about the same size as our Sun. Aside from it known planets, the new planetary system has a tantalizing gap between the new Jovian discovery and two other big gas planets orbiting very close to the star, Marcy said.

There’s a huge region centered at about Earth-Sun distance, and in that gap… an Earth-mass planet could exist … and such a planet would be stable, " he said. "It could persist there for billions of years, so it’s conceivable that this system has rocky planets like Mars, Venus or Earth and we simply can’t detect them," Marcy said.

Heavy Traffic Heads for Mars

American space agency NASA has outlined ambitious, long-term plans to explore the planet Mars. It says six major missions will take place in little more than 10 years, with Italy and France also participating. At an annual cost estimated at $400 million to $450 million a year for the next five years, the agency will dispatch a combination of orbiting spacecraft and landers to the Red Planet. Then, after 2010, the agency will undertake a mission to bring back samples from Mars. In 1999, NASA lost two Martian missions : the Mars Polar Lander and the Mars Climate Orbiter. The failures were a huge blow and prompted a major review of the way NASA carries through its space operations. The campaign to explore Mars is unparalleled in the history of space exploration. It’s meant to be a robust, flexible, long-term programme that will give the highest chances for success. The new strategy is aimed to answer questions about Mars’ mineralogy, geology and climate history. The idea is to ‘follow the water’ so we may know the answers to far-reaching questions about the red planet humans have asked over the generations: Did life ever arise there, and does life exist there now ?"

Astronomers spot winking baby star

A Sun-like star just out of infancy has winked at astronomers, indicating its eclipse by cosmic dust and rocks, the stuff of which planets like Earth could possibly form, scientists reported on Wednesday.

The star, located in the Unicorn constellation about 2,400 light years from Earth, disappeared from view for regular periods of about 48 days over the past six years. Its disappearance suggested an eclipse, but not a typical one caused by an intervening planet, star or moon.

Only a collection of smaller objects, like dust and rocks, could cause the long eclipse the astronomers saw. Known as KH 15D, the star is only about 3 million years old, a prime age for monitoring by astronomers interested in our solar system's planet-forming past.

"We've monitored thousands of these stars over the years and this is the only that behaves this way," said astronomer William Herbst of Wesleyan University in Connecticut. "Essentially the star winks at us."

The dust that caused the wink is different from the fine interstellar dust that is distributed throughout the cosmos. Herbst said. Its particles are bigger, indicating that it is clumping into what astronomers call a protoplanetary disk - the disk from which planets can form.

"Is there a mass in here that is somehow sculpting the obscuring clouds so that it's producing these rings of material which then circle around the star and alternately block the object? We think that's very possible," Herbst said. There could be two blobs circling the star, or just one, but there is no confirmation as yet of exactly what could be causing this kind of disk to form, said Herbst's colleague Catrina Hamilton.

At just 3 million years old, KH 15D is a cosmic toddler barely out of infancy. By contrast, our solar system is thought to be about 4.5 billion years old. However, some astronomers believe the planets may have begun forming when the Sun was a few million years old.

The disk is forming quite close to the star, closer than the planet Mercury is to the Sun. "The star is ... like the Sun was when it was 3 million years old, so the processes that are going on in this inner disk region, where terrestrial planets would be forming - could be analogous to what was going on with the formation of Earth," Herbst said.

Universe Measured: We're 156 Billion Light-years Wide!

f you've ever wondered how big the universe is, you're not alone. Astronomers have long pondered this, too, and they've had a hard time figuring it out. Now an estimate has been made, and its a whopper.

The universe is at least 156 billion light-years wide.

In the new study, researchers examined primordial radiation imprinted on the cosmos. Among their conclusions is that it is less likely that there is some crazy cosmic "hall of mirrors" that would cause one object to be visible in two locations. And they've ruled out the idea that we could peer deep into space and time and see our own planet in its youth.

First, let's see why the size is a number you've never heard of before.

Stretching reality

The universe is about 13.7 billion years old. Light reaching us from the earliest known galaxies has been travelling, therefore, for more than 13 billion years. So one might assume that the radius of the universe is 13.7 billion light-years and that the whole shebang is double that, or 27.4 billion light-years wide.

But the universe has been expanding ever since the beginning of time, when theorists believe it all sprang forth from an infinitely dense point in a Big Bang.

"All the distance covered by the light in the early universe gets increased by the expansion of the universe," explains Neil Cornish, an astrophysicist at Montana State University. "Think of it like compound interest."

Need a visual? Imagine the universe just a million years after it was born, Cornish suggests. A batch of light travels for a year, covering one light-year. "At that time, the universe was about 1,000 times smaller than it is today," he said. "Thus, that one light-year has now stretched to become 1,000 light-years."

All the pieces add up to 78 billion-light-years. The light has not traveled that far, but "the starting point of a photon reaching us today after travelling for 13.7 billion years is now 78 billion light-years away," Cornish said. That would be the radius of the universe, and twice that -- 156 billion light-years -- is the diameter. That's based on a view going 90 percent of the way back in time, so it might be slightly larger.

"It can be thought of as a spherical diameter is the usual sense," Cornish added comfortingly.

(You might have heard the universe is almost surely flat, not spherical. The flatness refers to its geometry being "normal," like what is taught in school; two parallel lines can never cross.)

Hall of mirrors

The scientists studied the cosmic microwave background (CMB), radiation unleashed about 380,000 years after the Big Bang, when the universe had first expanded enough to cool and allow atoms to form. Temperature differences in the CMB left an imprint on the sky that was used last year to reveal the age of the universe and confirm other important cosmological measurements.

The CMB is like a baby picture of the cosmos, before any stars were born.

The focus of the new work, which was published last week in the journal Physical Review Letters, was a search of CMB data for paired circles that would have indicated the universe is like a hall of mirrors, in which multiple images of the same object could show up in different locations in space-time. A hall of mirrors could mean the universe is finite but tricks us into thinking it is infinite.

Think of it as a video game in which an object disappearing on the right side of the screen reappears on the left.

"Several years ago we showed that any finite universe in which light had time to 'wrap around' since the Big Bang would have the same pattern of cosmic microwave background temperature fluctuations around pairs of circles," Cornish explained. They looked for the most likely patterns that would be evident in a CMB map generated by NASA's Wilkinson Microwave Anisotropy Probe (WMAP).

They didn't find those patterns.

Don't look back

"Our results don't rule out a hall-of-mirrors effect, but they make the possibility far less likely," Cornish told SPACE.com, adding that the findings have shown "no sign that the universe is finite, but that doesn't prove that it is infinite."

The results do render impossible a "soccer ball" shape for the universe, proposed late last year by another team. "However, if they were to 'pump up' their soccer ball to make it larger, they could evade our bounds" and still be in the realm of possibility, Cornish said. Other complex shapes haven't been ruled out.

The findings eliminate any chance of seeing our ancient selves, however, unless we can master time travel.

"If the universe was finite, and had a size of about 4 billion to 5 billion light-years, then light would be able to wrap around the universe, and with a big enough telescope we could view the Earth just after it solidified and when the first life formed," Cornish said. "Unfortunately, our results rule out this tantalizing possibility."

---

Impossible? Cornish Explains Further

Update, 8:25 a.m. Tuesday, May 25

This article generated quite a few e-mails from readers who were perplexed or flat out could not believe the universe was just 13.7 billion years old yet 158 billion light-years wide. That suggests the speed of light has been exceeded, they argue. So SPACE.com asked Neil Cornish to explain further. Here is his response:

"The problem is that funny things happen in general relativity which appear to violate special relativity (nothing traveling faster than the speed of light and all that).

"Let's go back to Hubble's observation that distant galaxies appear to be moving away from us, and the more distant the galaxy, the faster it appears to move away. The constant of proportionality in that relationship is known as Hubble's constant.

"One seemingly paradoxical consequence of Hubble's observation is that galaxies sufficiently far away will be receding from us at a velocity faster than the speed of light. This distance is called the Hubble radius, and is commonly referred to as the horizon in analogy with a black hole horizon.

"In terms of special relativity, Hubble's law appears to be a paradox. But in general relativity we interpret the apparent recession as being due to space expanding (the old raisins in a rising fruit loaf analogy). The galaxies themselves are not moving through space (at least not very much), but the space itself is growing so they appear to be moving apart. There is nothing in special or general relativity to prevent this apparent velocity from exceeding the speed of light. No faster-than-light signals can be sent via this mechanism, and it does not lead to any paradoxes.

"Indeed, the WMAP data [on cosmic microwave background radiation] contain strong evidence that the very early universe underwent a period of accelerated expansion in which the distance been two points increased so quickly that light could not outrace the expansion so there was a true horizon -- in precise analogy with a black hole horizon. Indeed, the fluctuations we see in the CMB are thought to be generated by a process that is closely analogous to Hawking radiation from black holes.

"Even more amazing is the picture that emerges when you combine the WMAP data with [supernova] observations, which imply that the universe has started inflating again. If this is true, we have started to move away from the distant galaxies at a rate that is increasing, and in the future we will not be able to see as many galaxies as they will appear to be moving away from us faster than the speed of light (due to the expansion of space), so their light will not be able to reach us."

Universe Measured: We're 156 Billion Light-years Wide!

f you've ever wondered how big the universe is, you're not alone. Astronomers have long pondered this, too, and they've had a hard time figuring it out. Now an estimate has been made, and its a whopper.

The universe is at least 156 billion light-years wide.

In the new study, researchers examined primordial radiation imprinted on the cosmos. Among their conclusions is that it is less likely that there is some crazy cosmic "hall of mirrors" that would cause one object to be visible in two locations. And they've ruled out the idea that we could peer deep into space and time and see our own planet in its youth.

First, let's see why the size is a number you've never heard of before.

Stretching reality

The universe is about 13.7 billion years old. Light reaching us from the earliest known galaxies has been travelling, therefore, for more than 13 billion years. So one might assume that the radius of the universe is 13.7 billion light-years and that the whole shebang is double that, or 27.4 billion light-years wide.

But the universe has been expanding ever since the beginning of time, when theorists believe it all sprang forth from an infinitely dense point in a Big Bang.

"All the distance covered by the light in the early universe gets increased by the expansion of the universe," explains Neil Cornish, an astrophysicist at Montana State University. "Think of it like compound interest."

Need a visual? Imagine the universe just a million years after it was born, Cornish suggests. A batch of light travels for a year, covering one light-year. "At that time, the universe was about 1,000 times smaller than it is today," he said. "Thus, that one light-year has now stretched to become 1,000 light-years."

All the pieces add up to 78 billion-light-years. The light has not traveled that far, but "the starting point of a photon reaching us today after travelling for 13.7 billion years is now 78 billion light-years away," Cornish said. That would be the radius of the universe, and twice that -- 156 billion light-years -- is the diameter. That's based on a view going 90 percent of the way back in time, so it might be slightly larger.

"It can be thought of as a spherical diameter is the usual sense," Cornish added comfortingly.

(You might have heard the universe is almost surely flat, not spherical. The flatness refers to its geometry being "normal," like what is taught in school; two parallel lines can never cross.)

Hall of mirrors

The scientists studied the cosmic microwave background (CMB), radiation unleashed about 380,000 years after the Big Bang, when the universe had first expanded enough to cool and allow atoms to form. Temperature differences in the CMB left an imprint on the sky that was used last year to reveal the age of the universe and confirm other important cosmological measurements.

The CMB is like a baby picture of the cosmos, before any stars were born.

The focus of the new work, which was published last week in the journal Physical Review Letters, was a search of CMB data for paired circles that would have indicated the universe is like a hall of mirrors, in which multiple images of the same object could show up in different locations in space-time. A hall of mirrors could mean the universe is finite but tricks us into thinking it is infinite.

Think of it as a video game in which an object disappearing on the right side of the screen reappears on the left.

"Several years ago we showed that any finite universe in which light had time to 'wrap around' since the Big Bang would have the same pattern of cosmic microwave background temperature fluctuations around pairs of circles," Cornish explained. They looked for the most likely patterns that would be evident in a CMB map generated by NASA's Wilkinson Microwave Anisotropy Probe (WMAP).

They didn't find those patterns.

Don't look back

"Our results don't rule out a hall-of-mirrors effect, but they make the possibility far less likely," Cornish told SPACE.com, adding that the findings have shown "no sign that the universe is finite, but that doesn't prove that it is infinite."

The results do render impossible a "soccer ball" shape for the universe, proposed late last year by another team. "However, if they were to 'pump up' their soccer ball to make it larger, they could evade our bounds" and still be in the realm of possibility, Cornish said. Other complex shapes haven't been ruled out.

The findings eliminate any chance of seeing our ancient selves, however, unless we can master time travel.

"If the universe was finite, and had a size of about 4 billion to 5 billion light-years, then light would be able to wrap around the universe, and with a big enough telescope we could view the Earth just after it solidified and when the first life formed," Cornish said. "Unfortunately, our results rule out this tantalizing possibility."

---

Impossible? Cornish Explains Further

Update, 8:25 a.m. Tuesday, May 25

This article generated quite a few e-mails from readers who were perplexed or flat out could not believe the universe was just 13.7 billion years old yet 158 billion light-years wide. That suggests the speed of light has been exceeded, they argue. So SPACE.com asked Neil Cornish to explain further. Here is his response:

"The problem is that funny things happen in general relativity which appear to violate special relativity (nothing traveling faster than the speed of light and all that).

"Let's go back to Hubble's observation that distant galaxies appear to be moving away from us, and the more distant the galaxy, the faster it appears to move away. The constant of proportionality in that relationship is known as Hubble's constant.

"One seemingly paradoxical consequence of Hubble's observation is that galaxies sufficiently far away will be receding from us at a velocity faster than the speed of light. This distance is called the Hubble radius, and is commonly referred to as the horizon in analogy with a black hole horizon.

"In terms of special relativity, Hubble's law appears to be a paradox. But in general relativity we interpret the apparent recession as being due to space expanding (the old raisins in a rising fruit loaf analogy). The galaxies themselves are not moving through space (at least not very much), but the space itself is growing so they appear to be moving apart. There is nothing in special or general relativity to prevent this apparent velocity from exceeding the speed of light. No faster-than-light signals can be sent via this mechanism, and it does not lead to any paradoxes.

"Indeed, the WMAP data [on cosmic microwave background radiation] contain strong evidence that the very early universe underwent a period of accelerated expansion in which the distance been two points increased so quickly that light could not outrace the expansion so there was a true horizon -- in precise analogy with a black hole horizon. Indeed, the fluctuations we see in the CMB are thought to be generated by a process that is closely analogous to Hawking radiation from black holes.

"Even more amazing is the picture that emerges when you combine the WMAP data with [supernova] observations, which imply that the universe has started inflating again. If this is true, we have started to move away from the distant galaxies at a rate that is increasing, and in the future we will not be able to see as many galaxies as they will appear to be moving away from us faster than the speed of light (due to the expansion of space), so their light will not be able to reach us."

TOP 10 OF ALL KIND

LOVE IS ONLY WEAPON TO SAVE THE WORLD

TOP 10 OF ALL KIND

LOVE IS ONLY WEAPON TO SAVE THE WORLD