Why is universe expanding

Another facility that will help answer the question of what the Hubble Constant's value is the James Webb Space Telescope, which is due to be launched late in By studying infrared wavelengths, it will allow better measurements that won't be obscured by the dust between us and the stars. If they find that the difference in the Hubble Constant does persist, however, then it will be time for new physics. And although many theories have been offered up to explain the difference, nothing quite fits what we see around us.

Each potential theory has a downside. For example, it might be there was another kind of radiation in the early universe, but we have measured the CMB so accurately this does not seem likely. Another option is that dark energy could be changing with time. It has forced scientists to dream up new ideas that could explain what is going on. Depending on what these new telescopes reveal, Beaton and Freedman could well find themselves in the midst of a mystery worthy of an Agatha Christie novel after all.

Join one million Future fans by liking us on Facebook , or follow us on Twitter or Instagram. If you liked this story, sign up for the weekly bbc. The mystery of how big our Universe really is. Share using Email. By Abigail Beall 29th March The cosmos has been expanding since the Big Bang, but how fast? The answer could reveal whether everything we thought we knew about physics is wrong. They could beat Cepheids in the near future, Kolb says. The needle could shift towards one of the other values.

Or it could stay put, and the other techniques might eventually converge to it. For now, cosmologists have plenty to puzzle over. Freedman, W. Riess, A. Download references. News 09 NOV News 17 SEP Obituary 06 AUG Zhejiang University School of Medicine. Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily. There are candidate theories, but none are compelling. The thing that is needed to decide between dark energy possibilities - a property of space, a new dynamic fluid, or a new theory of gravity - is more data, better data.

What is dark matter? We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see.

Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them.

Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter.

Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. However, at this point, there are still a few dark matter possibilities that are viable. Baryonic matter could still make up the dark matter if it were all tied up in brown dwarfs or in small, dense chunks of heavy elements.

But the most common view is that dark matter is not baryonic at all, but that it is made up of other, more exotic particles like axions or WIMPS Weakly Interacting Massive Particles. Dark Energy, Dark Matter In the early s, one thing was fairly certain about the expansion of the universe. What Is Dark Energy? Universe Dark Energy-1 Expanding Universe. This diagram reveals changes in the rate of expansion since the universe's birth 15 billion years ago.

The more shallow the curve, the faster the rate of expansion. The curve changes noticeably about 7. Astronomers theorize that the faster expansion rate is due to a mysterious, dark force that is pulling galaxies apart. Dark Matter Core Defies Explanation.

This image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell The standard model of cosmology incorporates all the familiar forms of matter and radiation and their interactions.

Because so little is known about these dark ingredients, they are perhaps the obvious place to begin tampering with the standard model. But what if we also assume that dark matter is not made of just a single substance? Since many different kinds of visible particles exist — quarks, electrons and so on — there might be multiple dark particles as well.

In a paper published last summer in Physical Review D , Loeb and two collaborators considered a form of dark matter that decays into a lighter particle and a massless particle known as a dark photon. As more and more dark matter decayed over time, they reasoned, its gravitational pull would have lessened, and thus the expansion of the universe would have sped up, relieving the Hubble tension.

But making small changes like this to the standard cosmological model can have unwanted knock-on effects. By varying the decay rate and the amount of dark matter that is lost in each decay, Loeb and colleagues selected a model of decaying dark matter that they say still agrees with other astronomical observations.

Yet he remains dissatisfied with the decaying dark matter idea, in part because it introduces two new uncertain quantities into the equations. Ever since the surprise discovery in that the expansion of the universe is accelerating , cosmologists have included a repulsive dark energy in their model of cosmic evolution.

But its nature remains a mystery. An extra dose of dark energy in the early universe, dubbed early dark energy , could reconcile the conflicting values of the Hubble constant.