Editor's Note: This story was originally printed in the February 2004 issue of Scientific American. We are reposting this story because author Adam Riess was selected as a MacArthur Fellow in 2008 by the MacArthur Foundation.
From the time of Isaac Newton to the late 1990s, the defining feature of gravity was its attractive nature. Gravity keeps us grounded. It slows the ascent of baseballs and holds the moon in orbit around the earth. Gravity prevents our solar system from flying apart and binds together enormous clusters of galaxies. Although Einstein’s general theory of relativity allows for gravity to push as well as pull, most physicists regarded this as a purely theoretical possibility, irrelevant to the universe today. Until recently, astronomers fully expected to see gravity slowing down the expansion of the cosmos.
In 1998, however, researchers discovered the repulsive side of gravity. By carefully observing distant supernovae—stellar explosions that for a brief time shine as brightly as 10 billion suns— astronomers found that they were fainter than expected. The most plausible explanation for the discrepancy is that the light from the supernovae, which exploded billions of years ago, traveled a greater distance than theorists had predicted. And this explanation, in turn, led to the conclusion that the expansion of the universe is actually speeding up, not slowing down. This was such a radical finding that some cosmologists suggested that the falloff in supernova brightness was the result of other effects, such as intergalactic dust dimming the light. In the past few years, though, astronomers have solidified the case for cosmic acceleration by studying ever more remote supernovae.
But has the cosmic expansion been speeding up throughout the lifetime of the universe, or is it a relatively recent development— that is, occurring within the past five billion years or so? The answer has profound implications. If scientists find that the expansion of the universe has always been accelerating, they will have to completely revise their understanding of cosmic evolution. But if, as cosmologists expect, the acceleration turns out to be a recent phenomenon, researchers may be able to determine its cause—and perhaps answer the larger question of the destiny of the universe—by learning when and how the expansion began picking up speed.
Battle of Titans
ALMOST 75 YEARS AGO astronomer Edwin Hubble discovered the expansion of the universe by observing that other galaxies are moving away from ours. He noted that the more distant galaxies were receding faster than nearby ones, in accordance with what is now known as Hubble’s law (relative velocity equals distance multiplied by Hubble’s constant). Viewed in the context of Einstein’s general theory of relativity, Hubble’s law arises because of the uniform expansion of space, which is merely a scaling up of the size of the universe.
In Einstein’s theory, the notion of gravity as an attractive force still holds for all known forms of matter and energy, even on the cosmic scale. Therefore, general relativity predicts that the expansion of the universe should slow down at a rate determined by the density of matter and energy within it. But general relativity also allows for the possibility of forms of energy with strange properties that produce repulsive gravity. The discovery of accelerating rather than decelerating expansion has apparently revealed the presence of such an energy form, referred to as dark energy.
Whether or not the expansion is slowing down or speeding up depends on a battle between two titans: the attractive gravitational pull of matter and the repulsive gravitational push of dark energy. What counts in this contest is the density of each. The density of matter decreases as the universe expands because the volume of space increases. (Only a small fraction of matter is in the form of luminous stars; the bulk is believed to be dark matter, which does not interact in a noticeable way with ordinary matter or light but has attractive gravity.) Although little is known about dark energy, its density is expected to change slowly or not at all as the universe expands. Currently the density of dark energy is higher than that of matter, but in the distant past the density of matter should have been greater, so the expansion should have been slowing down then.
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19 Comments
Add Comment"Gravity keeps us grounded. It slows the ascent of baseballs and holds the moon in orbit around the earth."
Reply | Report Abuse | Link to thisTechnically, it keeps the moon in orbit around the sun. The earth and the moon are a double-planet system orbiting around a common "center".
What makes this significantly different from the other planet-satellite systems is that when the moon's orbit takes it between the earth and the sun, the moon's orbit remains concave towards the sun, not towards the earth.
Why is the "dust" dimming distant supernovas expected to be uniform or isotropic? Can't different directions have different dimming?
Reply | Report Abuse | Link to thisIt is absolutely incomprehensible how anyone could believe that the speed of light is finite and that nothing else could travel faster. The expansion of space MUST be faster than light. If the expansion of space was not faster, light would have nowhere to go. Duh!!
Reply | Report Abuse | Link to thisIt is absolutely incomprehensible how anyone could believe that the speed of light is finite and that nothing else could travel faster. The expansion of space MUST be faster than light. If the expansion of space was not faster, light would have nowhere to go. Duh!!
Reply | Report Abuse | Link to thisFolks, has anyone ever thought about the speed of light being absolutely still relative to the Einstein's Spacetime Field? This field is also known as the "Higgs Field," it is an omnidirectional scalar field that permeates the entire universe. Why could it not be true that it is US that are moving relative to a beam of light, light by its very nature "stops in its tracks." This explains why the speed of light is constant, because as the universe expands, it is moving at lightspeed relative to a fixed, absolute frame of reference. In other words, we, our galaxy, and the very fabric of space itself are what is moving--relative to a motionless, timeless, and possibly infinite background space-time from which emanated the Big Bank, our universe and everything in it. Come to think of it, I think I will put together a technical paper on this topic.
Reply | Report Abuse | Link to thisThe speed of light is not constant over time so the acceleration and distance formulas are all off
Reply | Report Abuse | Link to thisThe theory that universe will expand to a point then begin to contract is fundamentally flawed. What would cause it to contract? Gravity? Praying?
Reply | Report Abuse | Link to thisWhen you stand by the ocean, you experience 1G. When you are 220 miles above the earth, you experience 0G. When you are 1 million miles away, how many G? Does it get weaker or stronger? How about when it is 10 billion miles away? The theory fails the common sense test. They can sell that to Christians, but dont try it on scientists. The further away you are from an object, the weaker its gravity pull. There is zero chance that the universe is going to get back into one single point, even if we assume it started from one single point.
This divorce is forever. Move on!
There is no need for dark energy, gravity folds space into what could be imagined as a doughnut with a singularity at the center. Much like a roller coaster driven by gravity as space expands, and as it crests the outside of the doughnut it falls back in on its'self. As if a balloon was blown up to the point of inversion with the point of inversion determined by gravity.The accelleration of space and matter in it viewed as an accellerated expantion to the observer but would really become an expansion into singularity driven by the force of gravity. This is a repetitive inversion, meaning that it is cyclic with a frequency relative to the universal mass and gravity over time.This is the origin of and ending of the universe.
Reply | Report Abuse | Link to thisWhen you read this post keep an open mind. This will challenge you to think outside the box.
Reply | Report Abuse | Link to thisEveryone here is missing an alternative explanation. This is that instead of the universe speeding up in it's expansion, the speed of light is in fact slowing down. Think about it. Do a google search and you will find that this is truly an alternative explanation. Now keep in mind that the speed of light slowing down would alter our concepts of time. This would mean that the universe is actually much younger than we believe. In fact it could be less than 10,000 years old! The problems scientists have with this explanation is that there is no known cause to the speed of light slowing down.
However the Bible has an explanation for this. This is that lucifer, called the bearer of light, was cast down from God's bandwidth and ever since his fall, the speed of light has slown down. When God spoke and all the frequencies of His glory became manifest, the cosmos became! From the tiniest vibrating superstring that is causing or singing the atoms that make up the table of 103 elements, all the way through everything the Hubble telescope sees, are the vibrating frequencies of Jesus voice. Colossians 1:16-17 says, For by Him all things were created that are in heaven an that are on earth, visible and invisible&He is before all things, and in Him all things consist (exist or are sustained).
The slowing down of light as explained through lucifer's fall, and secondly through man's fall, created a separation from the spiritual realm. The spiritual realm operates above the speed of light, because it is unaffected by the fall of lucifer and man. In other words the spiritual realm is all of original frequencies of God's glory. In the beginning, when God spoke the universe into existence, His entire bandwidth of glory was made physical. From His glory (all frequencies) and His voice (all frequencies expressed) all light, energy, and matter became.
Every creative idea, every vision, every prophecy comes to us from our future. The only way something can come from the future is if it travels faster than the speed of light. The only things that travel faster than the speed of light come from the spiritual realm, from the Holy Spirit. This is because we have lost the original bandwidth to communicate.Jesus Himself told His disciples that they will get their upper
bandwidth back. In John 16:13He said, When He, the Spirit of truth has
come, He will guide you into all truth&and He will show you things to
come. I want to show you your future.
These are all interesting questions. Light is made of particles called photons. Anything traveling will eventually slow down & this is what Edwin Hubble observed through his telescope, a slowing of light. The Universe is neither expanding nor contracting, it's simply swirling. It doesn't all collapse into a lump because once a certain mass is reached (mass of a star), the gravitational pressures are so great that the atoms degrade back into photons (light) and this is the formula : E = MC 2 (I've actually smashed a proton into light in my tiny lab). And of course MC 2 = E when the photons re-collect back into atoms (dark matter). This has been going on forever into the past & into the future as well. What Einstein didn't know, and that I discovered is that gravity is caused by a particle called the graviton. I didn't give it this name, was a nice fellow in a chat room who suggest this, and it stuck. Gravity is caused by gravitons bumping into things. Gravity pushes, it's not some mystical aether force, it's a simple particle. All atoms have gravitons in orbit around them. If you group a bunch of atoms together, you will get gravity. More atoms, more gravity. Gravitons also bump things from the sides and cause inertia. These inertia impacts are what regulate the movements of mechanical clocks, watches, etc. and were the first clue that gravitons are the source of time itself. Anyone can prove this with simple experiments. What is interesting is that gravitons travel in excess of 10,000 times the speed of light. If you pass light close to a large mass, the gravitons will bump into the photon particles & actually bend the light a small amount. This effect can be easily observed using telescopes. I hope this has been helpful...I'm available for questions....alfredschrader@aol.com
Reply | Report Abuse | Link to thisI have read the comments and suggest a few things: --think of space as ether and you live in very high velocity much faster than light , ether flow towards center of earth. As such you see things fall vertically. each ether particle reacts with each quark of matter as such Galileo found all objects big or small fall equally. ether is giving gravity effect. Michelson thought it dragable but it is not as such null result. Einstein mistaken by his Lorentz application and in postulates. We know light speed changes with medium that is why refraction as such light speed changes with different ether density location in space as such speed of light changes in space as per local ether density. So light speed is not universal constant neither the constants in law is universal constant and may be broad structure of law without the constant may not be changing. Our physics is wrong as Dr. Roger Penrose told in recent interview and to know why it is wrong --read my theory of ether-gravity-dark energy theory of gravitoethertons and balloon inside balloon theory published in ASTRONOMY.NET in year 2002 . If you open --durgadas datta facebook -- the links will be available for perusal and comments to my e-mail: durgadas.ddatta@gmail.com
Reply | Report Abuse | Link to thisRather than postulating dark energy and dark matter to account for observed acceleration of the expansion, why not simply attribute it to black holes? If one assumes the big bang resulted in a wide range in the mass of objects - with higher mass objects (including black holes or their precursors) traveling slightly slower than lower mass ones (including the rest of the observable universe), it would be fairly easy to imagine it took several billion years for the heavy masses to catch up (while their enormous gravity caused observable expansion to decelerate) - then continued plowing ahead of visible matter through sheer momentum... resulting in the acceleration now being seen as their gravity (now pulling normal matter in their wake from outside the bounds of the bubble occupied by normal matter). This would fit nicely with what we know about black holes - ie, detectable only by their effect on nearby light and matter; if the vast majority of black holes (which one would assume constitutes the vast majority of matter in the universe) were "ouside the bubble" for the last 7.5 billion years, there'd be no way to detect them other than the acceleration in expansion of the bubble
Reply | Report Abuse | Link to thisOK... newbie question. If observing distant galaxies means looking back in time, wouldn't it be logical that those galaxies, which we are seeing as they were millions or billions of years ago, would be moving away from us faster than closer ones? After all, the closer to the big bank we get the faster the motion away from us should be. I do not understand how this observation is surprising or unexpected. Please have patience with me. Thanks.
Reply | Report Abuse | Link to thisDURGADAS DATTA published a research paper --MISJUDGEMENT by NEWTON in year 2002/2003 in ASTRONOMY.NET where he proved that EINSTEIN is not correct in his theories and NEWTONIAN ideas of matter pull is wrong. INSTEAD Datta suggested that matter repels matter but attracts antimatter. ETHER once discarded by EINSTEIN by misunderstanding MICHELSONS EXPERIMENT . This Ether in the ETHER=GRAVITY=DARK ENERGY THEORY OF GRAVITOETHERTONS OF MR.DATTA has been further explained in his BALLOON INSIDE BALLOON THEORY OF MATTER AND ANTIMATTER UNIVERSES ON OPPOSITE ENTROPY PATH. According to him , this gravitoethertons or ether is produced at the common boundary of matter and antimatter universe by annihilation of matter and antimatter and injected into our universe to cause all laws and expansion as DARK ENERGY. SO ignoring ether or dark energy was a mistake by EINSTEIN. We live in a swirling,whirling,flowing GRAVITOETHERTON SOUP OF VARRYING DENSITY OF DARK ENERGY FIELD . SO COSMOLOGY CONSTANT IS NOT A CONSTANT BUT VARRYING FIELD DENSITY OF GRAVITOETHERTONS. DURGADAS DATTA SUGGESTED TO REVISE GRAVITY EQUATION AS F=P.G.M.m/R.R WHERE P IS PERMEABILITY OF GRAVITOETHERTONS. According to him GHRAVITOETHERTONS are magnetic and as such we live in magnetic universe of swirling gravitoethertons NOT NEWTONIAN GRAVITY PULL. IF WE APPLY THIS THEORY ,THEN NO DARK MATTER WILL BE REQUIRED TO EXPLAIN ANYTHING AND WE WILL UNDERSTAND DARK FLOW ALSO. LET US MODIFY NEWTONIAN AND EINSTEIN EQUATIONS TO EXPLAIN RECENT OBSERVATIONS. DURGADAS DATTA SAID that gravitoethertons are getting focussed at center of Earth and Sun and Milky way galaxy etc etc to produce intense heat and magnetism HIS theories has shown us to re look at our ASTRONOMY and formulate A ELECTRO-MAGNETIC UNIVERSE . DURGADAS DATTA said that we see matter in stable form in molecules and gravitoethertons are magnetically repelling each matter molecule equally -- IRRESPECTIVE OF MASS BUT BY CHARGE WHICH IS SAME -- towards center of earth so that we see all matter fall equally as observed by GALILEO. EVEN IN AVOGADROS LAW WE SEE GRAVITOETHERTONS REACT EQUALL WITH ANY GAS MOLECULE BY CHARGE ALONE SO THAT NUMBER OF MOLECULES ARE SAME. MENDELEEFS TABLE MAY ALSO BE EXPLAINED SIMILARLY. SO DURGADAS DATTA HAS GIVEN US MAGNETIC GRAVITOETHERTONS THEORY OF ELECTRO-MAGNETIC UNIVERSE BEYOND STANDARD MODEL TO RE LOOK ALL RECENT ASTRONOMICAL PHENOMENA. e-mail: durgadas.ddatta@gmail.com.
Reply | Report Abuse | Link to thisGravitoethertons are injectected into our universe in cycles and not uniform. Therefore the flares on sun is also periodic and non uniform due to effect of gravitoethertons fallin on sun. The temp. of sun flare is more than sun surface due to this external effect and also the radioactivity on earths radioactive isotopes is cyclic non uniform due to gravitoethertons. --durgadas.ddatta@gmail.com
Reply | Report Abuse | Link to thisThe theoretical calculation of quantum vacuum energy density is wrong by 55 orders of magnitude? And now they expect it to be zero once they add in "a new symmetry principle"? How many "free paramters" do they have in this "theoretical" framework that they can go on tweaking until they can make the observations fit the "theory"?
Reply | Report Abuse | Link to thisSo now they want us to believe that the rate of expansion was slowing down until the formation of the galaxies and then started speeding up again? And the only "evidence" for this comes an equipment that only a few have access to?
The amazing thing is not that the cosmologists come out with such bizarre theories. After all, they need to continue to get funding. But that anyone else takes them seriously!
I'm no scientist, however, it is clear from the fact "The Expanding Universe: From Slowdown to Speed Up" is,
Reply | Report Abuse | Link to thisthere is some other thing (Pure physics) in the known universe which can travel faster than light and its nothing but space. As space is one of the major factor which controls the visible brightness of the light.
I guess, based on this fact we are assuming the Universe is expanding.
We found liquid vortex to generate double spiral waves. Super massive Black Hole vortex should in the same way generate gravitational spiral waves- could it cause the Universe accelerated expansion? It is our opinion that, yes, it is the highly probable cause of it!
Reply | Report Abuse | Link to thisVortex, an important Nature phenomenon, is normally hardly accessible, or too distant, or too fast or, in other appearances, too slow for detailed parametric observations. Except the liquid vortex, a study of which we carried out, assuming it is adequately representing the generic vortex features.
We have found the vortex to generate double-spiral waves. Another spinning double-spiral was found to be formed below the funnel bottom propagating down into the drain hole. Due to the lower double spiral, the funnel bottom was most of the time shaped not as a circle but as a rough digit 8-like "dipole", and its spinning was the intrinsic cause inducing generation of the double spiral waves.
Spiral waves generation was taking place at all the conditions observed, and a solid conclusion was made that the double spiral wave generation is an intrinsic vortex property most probably universal and applicable for other types of vortexes including the Black Holes.
In this case, the spinning vortex bottom mass dipole dynamically modulates the space-time generating waves, which are propagating all the way through the space-time as spiral waves. Spiral waves carry forward momentum transferring it on their way to the massive objects, inducing a mass-repelling action at long-range when the static gravitation attraction deems out. This effect makes the Black Holes to be the likely source of (Dark) energy, and the generated spiral waves to carry and transfer the energy to the remote massive objects fueling the Universe accelerating expansion.
Here is an important note: thanks to the water transparency we could see the vortex from aside, which allowed us to observe the developments below the vortex bottom, actually beyond its "event horizon". If the liquid was non-transparent, the key function of the lower (beyond-the-vortex-bottom) double-spiral could not been observed and thereby not realized. This indicates that the beyond the event horizon Black Hole developments, even being unobservable, could, nevertheless, influence and even control the overall Black Hole structure and dynamics.
We are running a related detailed discussions with the images and links to the videos at http://www.thenakedscientists.com/forum/index.php?topic=42033.0 and at http://gotkisy.blog.com/
what if we are in fact towards the edge of the universe and while observing supernovas on the edge aswell they seem to be speeding away from us , as they are but most likely as the same speed , as the sphere expands distance between any galaxy will grow exponentially but the actual speed from its point of origin could be still the same.
Reply | Report Abuse | Link to thisexample place two dots on a balloon and blow it up so that the dots travels at a constant speed from the centre, yet on the surface the dots will gradually travel apart from each other at a faster pace. unless they find the centre of our universe data will be corrupted.
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