Star Gazing: Observing dark energy

Star Gazing: Observing dark energy

Calculating the mysteries of the universe

We have known about dark matter and dark energy for at least a decade but as yet still have no idea as to what they are. To make the issue worse, these two ingredients of the universe make up about 95 per cent of the matter in it. The matter making up us, our planet, the sun, Milky Way and everything else we can see in the universe adds up to the other five per cent. A discrepancy this big cannot be put down to bad measurements. It must be real.

Dark matter turned up when astronomers measured the orbits of stars in galaxies. If we know the orbital speeds of stars and how far they are from the centre of their galaxies we can determine the mass of the galaxy and how it is distributed. However, the calculation indicated there is much more material in galaxies than we see. This unknown stuff needed a name, so it ended up being called dark matter. The name is meaningless in that we have no idea what it is, or even if it is what we understand as matter at all.

The issue of dark energy is even stranger and is linked to the expansion of the universe. When that expansion was first discovered, it was logical to see if the expansion could be calculated backwards to see what happened in the past. This led to the discovery that at a point in the past, currently estimated to be just under fourteen billion years ago, everything in the universe, including space and time, were in one lump, which then started to expand. The Big Bang Theory was born.

If the Big Bang threw everything outwards, the expansion would be working against the gravitational attraction of everything in the universe trying to pull it all back together into one lump. The result would be that the expansion would slow over time, and might even reverse one day. However, the most distant galaxies tell us a different story; the expansion is speeding up. Imagine throwing a ball in the air and instead of it slowing and then falling back, it accelerated upwards, out of sight. As both common sense and Newton’s First Law say, things only accelerate when a force is acting on them. This outward force has become known as dark energy. As in the case of the dark matter, giving it a name does not tell us what it is. But now a project is coming together that should be a major step towards finding out.

The main priority is to come up with more and better data on how quickly really distant galaxies are being carried away from us by the expansion. Since the light from a galaxy a billion light years away from us has spent a billion years getting to us, we see it as it was a billion years ago. By looking at more and more distant galaxies we are looking further and further back in time. By measuring the speed that the galaxy is moving away from us, we know how fast the universe was expanding back then. So to help us get a better understanding of what dark energy might be, we need a lot more measurements of really distant galaxies. To address this need an international team of researchers has come up with a device called the Dark Energy Spectroscopic Instrument (DESI). Inside DESI are 5000 optical fibres. Each of these fibres can be used to capture the light from one galaxy. Measuring one selection of 5000 galaxies will take about 20 minutes, including galaxies as far as 10 billion light years away, that is 10 billion years back in time. The observing plan is to measure 35 million galaxies.

Our ignorance is underlined by the diversity of ideas as to what it could be. One idea is that it is vacuum pressure, random fluctuations in the fabric of space-time. Another is that gravity is more complicated than we think. In nature, every force has a counter-force, except gravity. Maybe it does, and we are seeing evidence of it. We need data.

Jupiter and Saturn lie low in the southwest after dark. The moon reaches last quarter on Nov. 18. Mars lies very low in the east before dawn.

Ken Tapping is an astronomer with the Dominion Radio Astrophysical Observatory near Penticton. Email: ken.tapping@nrc-cnrc.gc.ca

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Victory Church homeless shelter had the highest calls for police service above everywhere else, at 290 calls for service, in the first three months of the year. (Jesse Day Western News)
UPDATE: Human error doubled data about calls for police to Penticton’s homeless shelters

Police have now partnered with Interior Health to have a nurse come with them to calls

A woman wears a face mask and shield to curb the spread of COVID-19 while walking in North Vancouver, B.C., on Wednesday, January 6, 2021. THE CANADIAN PRESS/Darryl Dyck
57 new cases of COVID-19 in Interior Health region

Thirty people in the region are in hospital, 16 of whom are in intensive care

Fun in Penticton is being promoted through banners going up along Main and Westminster. (Suzanne White Western News)
Banners go up in downtown celebrating fun in Penticton

From beach or biking time to dining or shopping, the banners promote things to do

(File photo)
Penticton, Summerland RCMP having success with online crime reporting

They have also added new crimes that can be reported online

Parkway Elementary Gr. 4 and 5 students have created an art project displayed for sale at businesses around Penticton with money raised going back to the school, local charity and internationally. (Submitted)
Penticton elementary students artwork displayed around Penticton

Parkway Elementary Grade 4/5s have art at Lakeside Resort, Blendz and Dragon’s Den

Jose Marchand prepares Pfizer COVID-19 vaccination doses at a mobile clinic for members of First Nations and their partners, in Montreal, Friday, April 30, 2021. The National Advisory Committee on Immunization is coming under fire after contradicting the advice Canadians have been receiving for weeks to take the first vaccine against COVID-19 that they’re offered. THE CANADIAN PRESS/Ryan Remiorz
Trudeau says he is glad he got AstraZeneca, vaccines are only way out of pandemic

‘The most important thing is to get vaccinated with the first vaccine offered to you’

B.C.’s provincial health officer, Dr. Bonnie Henry. THE CANADIAN PRESS/Jonathan Hayward
Dip in COVID-19 cases with 572 newly announced in B.C.

No new deaths have been reported but hospitalized patients are up to 481, with 161 being treated in intensive care

(Kingfisher Boats photo)
In the market for a boat in the North Okanagan? Be prepared to wait

Vernon’s Kingfisher Boats is out of 2021 models, with many 2022 models already pre-sold

Solar panels on a parking garage at the University of B.C. will be used to separate water into oxygen and hydrogen, the latter captured to supply a vehicle filling station. (UBC video)
UBC parkade project to use solar energy for hydrogen vehicles

Demonstration project gets $5.6M in low-carbon fuel credits

FILE – A student arrives at school as teachers dressed in red participate in a solidarity march to raise awareness about cases of COVID-19 at Ecole Woodward Hill Elementary School, in Surrey, B.C., on Tuesday, February 23, 2021. THE CANADIAN PRESS/Darryl Dyck
B.C. ‘should be able to’ offer 1st dose of COVID vaccine to kids 12+ by end of June: Henry

Health Canada authorized the vaccine for younger teens this morning

A woman in the Harrison Mills area was attacked by a cougar on Tuesday, May 4. B.C. Conservation Officers killed two male cougars in the area; the attack was determined to be predatory in nature. (File photo)
2 cougars killed following attack on woman in Agassiz area

Attack victim remains in hospital in stable condition

A woman wears a face mask and shield to curb the spread of COVID-19 while walking in North Vancouver, B.C., on Wednesday, January 6, 2021. THE CANADIAN PRESS/Darryl Dyck
B.C. CDC updates info, acknowledging small respiratory droplets can spread COVID-19

Large droplets, not aerosols had been fixture of public health messaging for many months

George Ryga, considered by many as Canada’s most important English playwright lived in Summerland from 1963 until his death in 1987. He is the inspiration for the annual Ryga Arts Festival. (Contributed)
Summerland archive established for George Ryga

Renowned author wrote novels, poetry, stage plays and screen plays from Summerland home

Most Read